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Brain as Complex Adaptive System
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Brain as Complex Adaptive System
Model: GPT-4
There is ample evidence that the human brain is a self-organized, complex adaptive system that encodes stimuli with context-sensitive constraints.
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ChatGPT
ChatGPT
Indeed, the human brain is widely considered a self-organized, complex adaptive system. Let's break down what that means:
Self-organization
: This concept implies that structure or patterns emerge spontaneously from the interactions within the system itself, without being commanded by an outside authority or a single dominant component. In the brain, this can be seen in how neurons, through their repeated and dynamic interactions, form complex networks that underpin cognition, perception, and action.
Complex adaptive system
: This term refers to a system that is complex in that it is composed of multiple interconnected elements, and adaptive in that it has the capacity to change and learn from experience. The human brain is made up of billions of neurons and trillions of synapses, which interact in complex ways to produce thought, perception, emotion, and behavior. Furthermore, the brain is adaptive, in the sense that it can learn and change its own structure and function in response to input from the environment���a process known as neuroplasticity.
As for encoding stimuli with context-sensitive constraints, this is a crucial aspect of the brain's function. It means that the way our brain processes and encodes information depends on the context in which the stimuli are perceived. For example, the sound of the word "bat" will be processed differently depending on whether the context is baseball or wildlife. This ability for context-dependent processing allows for a richer, more nuanced perception and understanding of the world.
The human brain is a remarkable example of a self-organized, complex adaptive system, and understanding it better can provide insights into numerous aspects of human cognition, behavior, and neurological disorders.
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Constraints work, then, by modifying either a system's phase space or the probability distribution of events and movements within that space.
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ChatGPT
ChatGPT
Yes, that's a solid understanding of constraints in the context of complex systems.
Modifying the system's phase space
: In complex systems theory, the "phase space" of a system is a mathematical concept that includes all possible states the system can be in. A constraint can modify the phase space by limiting or changing the possible states the system can occupy. For example, in the brain, physiological constraints like the fixed number of neurons and synaptic connections limit the potential configurations that the brain's neural networks can take on.
Altering the probability distribution of events and movements within that space
: Constraints can also influence the likelihood of the system being in one state versus another. In other words, they can change the probability distribution across the system's phase space. For instance, experiences and learning can change the synaptic strengths between neurons in the brain, making some neural firing patterns more likely than others. This can be seen as a change in the probability distribution within the brain's phase space.
These concepts are fundamental in understanding the functioning of complex adaptive systems, including the human brain, and can be applied to many other areas as well, such as ecology, economics, and social sciences.
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What are the differences between Lila Gatlin's types of constraints?
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ChatGPT
ChatGPT
Lila Gatlin was a theoretical biologist and physicist who wrote extensively about constraints and complexity in biological systems. She proposed different types of constraints that can act on a system:
Dynamical Constraints
: These constraints relate to the behavior of the system over time. They could be inherent to the system or could emerge from its interaction with the environment. They shape the trajectory of the system's evolution.
Structural Constraints
: These refer to the constraints that are imposed by the physical structure of the system. In biological organisms, these could include the physical properties of cells, the layout of an organism's body, or the arrangement of neurons in a brain.
Symbolic Constraints
: This type of constraint is about information and communication. In biological terms, this might refer to the genetic code - a system of symbolic representations (i.e., four different nucleotides) that contain instructions for the construction and operation of a biological organism.
Each type of constraint operates at different levels and in different ways to shape the behavior of complex systems. These constraints can interact with each other and with the components of the system, leading to the emergence of complex and often unpredictable behaviors. It's through these constraints and their interactions that complex systems like the human brain are able to adapt, evolve, and exhibit a wide range of behaviors.
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I mean specifically context-free and context-sensitive constraints.
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ChatGPT
ChatGPT
My apologies for the confusion. Let's focus on the specific types of constraints you mentioned: context-free and context-sensitive constraints.
Context-Free Constraints
: These are constraints that apply universally and independently of the specific situation or environment. In biological systems, context-free constraints could include fundamental physical laws and constants, genetic constraints, or basic biochemistry that is conserved across different species. For example, the genetic code which translates sequences of nucleotides into amino acids is essentially the same in all known life forms, making it a context-free constraint.
Context-Sensitive Constraints
: These constraints, in contrast, are dependent on the particular situation or environment. They change based on the context and circumstances. In the brain, for example, the interpretation of a neural signal might depend on the context in which it is received. Similarly, in evolution, the fitness of a particular trait often depends on the environmental context, making natural selection a context-sensitive constraint.
Together, context-free and context-sensitive constraints shape the behavior and evolution of complex adaptive systems. By understanding these constraints and how they interact, we can better understand the behavior of these systems and potentially predict their future states.
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When organized into a complex, integral whole, parts become correlated as a function of context-dependent constraints imposed on them by the newly organizd system in which they are now embedded.
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ChatGPT
ChatGPT
Yes, you're correct. This concept represents a key idea in systems theory and complex systems science. It's also closely related to the concept of emergence, where new properties or behaviors arise from the interactions of parts within a system. These emergent behaviors or properties are not predictable solely based on the individual parts themselves, but rather depend on the organization of these parts and the context-dependent constraints within the system.
Let's take the example of a human brain, which is composed of billions of neurons. These neurons, when considered individually, have certain properties. However, when they become organized into the complex, integral whole that is the brain, they start to function in a completely different way due to the interactions and relationships with other neurons. They become correlated due to context-dependent constraints imposed by the brain's structure, function, and the surrounding environment.
For instance, the firing pattern of a neuron may change based on its connections with other neurons and the input it receives from them. In other words, the neuron's activity becomes correlated with the activity of the other neurons to which it's connected, and this correlation is influenced by the constraints of the system. These constraints may include the physical structure of the brain, the strengths of synaptic connections, the timing of neuronal firing, etc.
In a broader sense, context-dependent constraints influence the behavior of the individual components (like neurons), guiding them to work together in a coordinated manner, thus allowing the emergence of complex behaviors and functions at a higher level (like perception, cognition, etc.). This integral organization creates a new level of complexity and adaptation that could not be predicted from the properties of the neurons alone.
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Catalysts (collectively autocatalytic sets), feedback loops, and biological resonance and entrainment embody context-sensitive constraints.
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ChatGPT
ChatGPT
Indeed, catalysts (or more specifically in biological systems, autocatalytic sets), feedback loops, and biological resonance and entrainment are all examples of context-sensitive constraints. Let's break down how each of these mechanisms embody context-sensitive constraints:
Autocatalytic Sets
: In biology, an autocatalytic set is a collection of molecules, each of which can be catalytically produced from other molecules in the set, given a small "seed" of initial molecules. This concept is central to theories about the origin of life. Autocatalytic sets represent context-sensitive constraints because their function and formation are highly dependent on the particular molecules present and the environmental conditions. A slight change in these conditions or the presence of different molecules could dramatically alter the functioning or even the existence of the autocatalytic set.
Feedback Loops
: Feedback loops are fundamental to many biological processes, including homeostasis, neuronal regulation, and hormonal control. They act as context-sensitive constraints because the effect of the feedback loop is dependent on the current state of the system. For instance, in a negative feedback loop that controls body temperature, the actions taken to either cool or warm the body are dependent on the current body temperature and the surrounding environmental temperature.
Biological Resonance and Entrainment
: Biological resonance is a phenomenon where biological systems (like the heart, the brain, etc.) oscillate at certain frequencies, and these oscillations can be reinforced by external signals with the same frequency. Entrainment, on the other hand, refers to the synchronization of these oscillations with an external rhythm or cycle, such as the light-dark cycle for circadian rhythms. These phenomena embody context-sensitive constraints because the resonance or entrainment is highly dependent on the external signals and rhythms that the system is exposed to.
In each of these cases, the specific behavior or state of the system is determined not just by the components of the system itself, but also by the specific environmental conditions or context. The fact that these mechanisms can adapt and respond to changing conditions makes them an integral part of what makes biological systems complex and adaptive.
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From the bottom up, the establishment of context-sensitve constraints is the phase change that self-organizes the global level.
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ChatGPT
ChatGPT
Indeed, the establishment of context-sensitive constraints can be seen as a "phase change" that helps self-organize a system at the global level.
Phase changes in physics refer to transitions between states of matter, like from solid to liquid or liquid to gas. When applied to complex systems, phase changes refer to a sudden shift in the behavior or organization of the system due to the changing of certain parameters.
When parts of a system are organized from the bottom up under context-sensitive constraints, they start to function differently as a whole compared to their individual functions. These parts start to exhibit correlated behaviors, and new emergent properties arise at the global level. This shift from local, independent behaviors to global, interdependent behaviors can be considered a type of phase change in the context of complex systems.
For instance, in a neural network, individual neurons may fire independently. However, as connections between neurons strengthen and adjust under the influence of various context-sensitive constraints (like synaptic plasticity, which is dependent on the timing of neural firing), the network may suddenly shift to a state where large groups of neurons fire together in a synchronized manner. This synchronization could represent a global pattern of activity that underlies a specific cognitive function, representing a phase change from independent to coordinated behavior.
This "phase change" that self-organizes the global level is a crucial aspect of complex adaptive systems, allowing for the emergence of complex behaviors from simple components. Understanding these changes can provide key insights into the dynamics of such systems, including the human brain, ecosystems, societies, and more.
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These excerpts have been from Dynamics in Action by Alicia Juarrero. She proposes an interpretive, narrative model of explanation inspired by a mereological hermeneutical interpretation.
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ChatGPT
ChatGPT
"Dynamics in Action" by Alicia Juarrero is indeed a significant contribution to the field of philosophy of action, and it has wide-ranging implications for our understanding of complex systems.
Juarrero applies complex systems theory to human action, suggesting that actions should be seen as emergent phenomena in a dynamic system, constrained by both context-free and context-sensitive constraints. Her interpretive, narrative model of explanation emphasizes the importance of understanding the context in which actions occur, as well as the history and intentions of the actor.
A mereological interpretation, in this context, refers to an understanding of how the parts of a system relate to the whole. In complex systems, the properties of the whole cannot be reduced to the properties of its parts, and Juarrero applies this perspective to human action.
Hermeneutical interpretation, on the other hand, refers to a method of understanding and interpretation that is often used in the social sciences and humanities. It involves considering the meaning of a text or action within its broader context, which includes not only the immediate environment but also cultural, historical, and personal contexts.
In combining these approaches, Juarrero's work provides a nuanced and insightful framework for understanding human action as an emergent phenomenon within a dynamic, complex system. It underscores the fact that our actions are shaped by a multitude of interacting factors, including not only our immediate environment but also our personal histories and the broader cultural and social context.
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She says, the gloval dynamics of self-organizing complex adaptive processes constrain top-down their components (motor processes in the case of behaviour).
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ChatGPT
ChatGPT
Alicia Juarrero's assertion that the global dynamics of self-organizing complex adaptive processes constrain their components top-down is a reflection of the key principles in complexity theory. Let's break it down:
In self-organizing complex adaptive systems, such as the human brain, there are interactions and dependencies both ways: from the individual components to the whole (bottom-up) and from the whole to the individual components (top-down).
In the context of human behavior, the "motor processes" represent the individual components or actions. These are not isolated or independent processes, but are integrated and coordinated to produce complex behavior. The top-down constraints come from the global dynamics of the system, i.e., the overall state of the brain and the organism, including cognitive processes, emotions, memories, and goals.
For instance, your decision to reach for a cup of coffee involves a complex interplay of perception, cognition, and motor planning, which then guides the specific motor actions needed to reach for the cup and grasp it. The global state of the system (your intention to drink coffee, your perception of the cup's location, your memories of how to perform the action) provides top-down constraints that guide and shape the specific motor processes involved.
This top-down constraint doesn't mean that the system is strictly deterministic or predictable. Rather, it's a dynamic interaction between global and local processes, with the system continually adapting and reorganizing itself in response to changing conditions. It reflects the non-linear, adaptive, and emergent properties of complex systems. Understanding these top-down and bottom-up influences can provide a more complete picture of the complexity of behavior and other phenomena in such systems.
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Context Changes Everything eBook by Alicia Juarrero
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balance of who holds power in our societies, a context has been slowly. created in which any muscular response to climate change seems politically.
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Context Changes Everything: How Constraints Create Coherence
Book by Alicia Juarrero
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From the influential author of Dynamics in Action, how the concepts of constraints provide a way to rethink relationships, opening the way to intentional, meaningful causation.Grounding her work in the problem of causation, Alicia Juarrero challenges previously held beliefs that only forceful impacts are causes. ... Google Books
Originally published: 2023
Author: Alicia Juarrero
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It appears that you have conducted a search related to Alicia Juarrero's book "Context Changes Everything: How Constraints Create Coherence." This book builds upon Juarrero's previous work in "Dynamics in Action" and further explores the role of constraints in shaping complex systems. The search results indicate various sources where you can purchase or access the book.
In "Context Changes Everything," Juarrero further delves into the problem of causation, challenging the idea that only forceful impacts can be considered as causes. Instead, she promotes the understanding that coherence is induced by enabling constraints, leading to intentional, meaningful causation.
This view aligns with her emphasis on the significance of both context-free and context-sensitive constraints in shaping the behavior of complex systems, which we have been discussing. By providing a deep analysis of these concepts, Juarrero's work contributes to a better understanding of the dynamics of complex adaptive systems, whether they are biological, social, or artificial.
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A list of everything we've talked about so far.
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Sure, here's a summary of the concepts we've discussed:
Complex Adaptive Systems
: Systems made up of many parts (agents) which interact with each other, leading to emergent behavior and adaptation of the system as a whole. These include natural phenomena such as ecosystems and brains, as well as human-made systems like economies and traffic networks.
Context-Sensitive Constraints
: Constraints that modify a system's behavior based on the current context or state of the system. The same action or event can have different outcomes or effects depending on the context in which it occurs.
Lila Gatlin's Types of Constraints
: Lila Gatlin categorized constraints into two types, namely context-free constraints, which function independently of the specific state or context of the system, and context-sensitive constraints, which modify a system's behavior based on the current context or state of the system.
Phase Space
: A multidimensional space in which each dimension represents a possible state of a system. The path taken by a system through this space represents the system's behavior over time.
Autocatalytic Sets
: Collections of molecules that can catalytically produce each other from a seed set, serving as an example of context-sensitive constraints in biology.
Feedback Loops
: Fundamental to many biological processes, these loops represent the reciprocal nature of cause-and-effect relationships. Feedback loops, both positive and negative, are examples of context-sensitive constraints.
Biological Resonance and Entrainment
: Phenomena where biological systems oscillate at certain frequencies, reinforced by external signals with the same frequency. Entrainment is the synchronization of these oscillations with an external rhythm.
Phase Changes
: In complex systems theory, a phase change refers to a significant shift in the system's behavior due to a change in certain parameters.
Alicia Juarrero's Work
: We discussed her book "Dynamics in Action," where she proposes an interpretive, narrative model of explanation based on a mereological hermeneutical interpretation, focusing on the role of context-sensitive and context-free constraints in complex systems. We also mentioned her other book, "Context Changes Everything: How Constraints Create Coherence."
Top-Down Constraints
: In complex systems, global dynamics can exert top-down constraints on the components of the system, shaping their behavior in the process. This concept is central to Juarrero's understanding of the dynamics of complex systems.
I hope this summary helps! If you need more information or clarification on any of these points, feel free to ask.
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Constraint programming (CP) is a programming paradigm aimed at solving combinatorial problems. It draws from various fields such as artificial intelligence, computer science, and operations research. In CP, the programmer declares the constraints on the feasible solutions for a set of decision variables, instead of providing explicit steps or sequences for executing a solution. The constraints only define the properties of the solution, rather than a procedural route to it. A method is then required to solve these constraints, usually relying on techniques like chronological backtracking and constraint propagation.
CP can be expressed as a form of constraint logic programming, which involves incorporating constraints into a logic program. This was initially done by Jaffar and Lassez in 1987 in the context of Prolog II, leading to the first implementations of constraint logic programming such as Prolog III, CLP(R), and CHIP.
Beyond logic programming, constraints can be incorporated into other programming paradigms including functional programming, term rewriting, and imperative languages. Languages such as Oz (functional) and Kaleidoscope (imperative) have built-in support for constraints, but constraints can also be implemented in imperative languages via constraint solving toolkits, which are separate libraries for an existing imperative language.
In relation to constraint-based evolution, this paradigm involves evolving systems under constraints that shape and direct their development. Just as constraints in CP guide the search for solutions, in constraint-based evolution, the constraints can guide the process of evolution, determining what kind of solutions (or 'evolutions') are feasible and guiding the system towards those.
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You've provided a great summary of Constraint Programming (CP) and how it connects to other domains such as artificial intelligence, logic programming, and evolutionary systems. Let's expand on these topics a little more:
Constraint Programming (CP):
In CP, instead of specifying a step-by-step algorithm to solve a problem, you define the problem in terms of constraints that potential solutions must satisfy. CP is particularly effective for combinatorial problems such as scheduling, routing, and allocation where there is a vast space of potential solutions. The challenge in CP lies in efficiently navigating this solution space.
Constraint Logic Programming:
This combines logic programming (a type of programming paradigm where program statements represent facts and rules about problems within a system of formal logic) with constraint solving. Jaffar and Lassez's work in 1987 on Prolog II was seminal in this field.
Constraint Incorporation into Other Paradigms:
As you mentioned, constraints can also be incorporated into other programming paradigms such as functional programming (Oz) and imperative languages (Kaleidoscope). Constraint toolkits offer another way to utilize constraints, allowing you to add constraint-solving capabilities to existing imperative languages.
Constraint-Based Evolution:
Similar to CP, where constraints guide the search for solutions, in constraint-based evolution, constraints shape the process of evolution. This view is particularly pertinent to the study of biological evolution, where environmental and genetic constraints guide the path of evolutionary development. But it also applies to artificial systems like evolutionary algorithms, where artificial constraints can be used to guide the search for solutions.
It's interesting to see how the idea of constraints, which we also discussed in the context of complex systems and human action, applies across such a diverse range of domains. It's a testament to the power and generality of this concept.
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Connections with the topics discussed before.
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ChatGPT
Constraint programming and the dynamics of complex adaptive systems, as discussed earlier, are two different areas, but they have underlying similarities due to their shared emphasis on constraints. Here are some potential connections:
Constraints Shaping Behavior and Solutions
: In both fields, constraints aren't seen as merely restrictive but also as guiding and shaping behavior or solutions. In complex adaptive systems, context-sensitive constraints guide the system's evolution and dynamics. Similarly, in constraint programming, constraints guide the search for feasible solutions.
Top-down Influences
: In Alicia Juarrero's view of complex adaptive systems, top-down constraints from the global dynamics influence the behavior of the system's components. This is somewhat analogous to constraint programming, where global constraints on the feasible solutions guide the behavior of the algorithm.
Phase Spaces and Solution Spaces
: The concept of a phase space in complex systems is somewhat similar to the solution space in constraint programming. Both represent the set of all possible states or solutions, and the system or algorithm's behavior can be understood as a path through this space.
Adaptation and Solving
: Both complex adaptive systems and constraint programming involve a process of adaptation or solving, guided by constraints. In complex systems, this could be the system adapting to changes in its environment. In constraint programming, it's about finding a solution that satisfies all the constraints.
Emergent Behavior and Combinatorial Problems
: Both areas deal with emergent behavior or properties. In complex adaptive systems, emergent behavior arises from the interactions between components. In constraint programming, the solutions to combinatorial problems often emerge from the interplay of the constraints.
While these are different fields with their own unique concepts and methods, these connections show how the concept of constraints provides a common language to discuss and analyze diverse phenomena.
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CHAPTER
2 The Brain as a Complex Adaptive System Get access Arrow
Jos�� Silveira, Patricia Rockman
https://doi.org/10.1093/med/9780197509326.003.0002
Pages 13���24
Published: October 2021
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Abstract
This chapter introduces complexity and its contribution to objective uncertainty in mental health and addiction. The view of the brain as a complex adaptive system is discussed, and the conceptualization of the mind as emergent from the brain is introduced. Limits that complexity imposes on the accuracy of establishing causation, pattern recognition, and predictions���all three of which are fundamental to clinical practice and the research that informs it���are explained. The pragmatic utility of viewing the brain and mind through a lens of complex adaptive systems is discussed with emphasis on how it makes many sources of clinical uncertainty irreducible.
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The abstract you've shared outlines a chapter by Jos�� Silveira and Patricia Rockman on the brain as a complex adaptive system. They discuss several key ideas:
Brain as a Complex Adaptive System
: They suggest that the brain, with its billions of neurons and trillions of synaptic connections, is a complex adaptive system. This means the behavior of the brain emerges from the interactions of its many parts and adapts over time in response to the environment.
Mind as an Emergent Phenomenon
: The authors discuss the concept that the mind is an emergent property of the brain. In this view, consciousness and mental processes don't reside in any one part of the brain but emerge from the complex interplay of many individual neuronal activities.
Complexity and Uncertainty
: They emphasize that the complexity of the brain introduces a degree of uncertainty into our understanding and prediction of its behavior. This can impact pattern recognition, prediction, and establishing causation, all of which are vital to clinical practice and research in mental health and addiction.
Pragmatic Utility of the Complexity View
: Despite these challenges, they argue that viewing the brain and mind as complex adaptive systems can be pragmatically useful. It can help us appreciate that certain aspects of clinical uncertainty, stemming from this complexity, are irreducible.
This perspective aligns with the discussions we've had earlier on complex adaptive systems and constraints. It's also reminiscent of Alicia Juarrero's view on the limits of mechanistic explanations and the role of context-sensitive constraints in shaping behavior. In the case of the brain, these constraints could be thought of as the physiological and structural rules that guide the interactions of neurons.
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Connections between the topics.
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The discussions so far have covered a wide range of topics, from constraint programming to complex adaptive systems and the brain. Despite their diversity, there are several key themes and connections that emerge:
Role of Constraints:
In both constraint programming and complex adaptive systems, constraints play a pivotal role. In constraint programming, constraints define the problem space and guide the search for feasible solutions. In complex adaptive systems, constraints (which can be context-free or context-sensitive) influence the behavior of the system components and shape the system's evolution.
Adaptation and Self-Organization:
Both complex adaptive systems and the brain (viewed as a complex adaptive system itself) exhibit properties of adaptation and self-organization. In these systems, the whole is more than just the sum of its parts, and high-level patterns and behaviors emerge from the interactions among the components. Similarly, constraint programming involves a search process that adapts based on the problem's constraints.
Emergence:
The concept of emergence appears in our discussion of complex adaptive systems, the brain, and even constraint programming. In complex systems and the brain, high-level behaviors or patterns emerge from the interactions among lower-level components. In constraint programming, feasible solutions emerge from the interplay of constraints.
Uncertainty and Limitations of Predictability:
The brain, viewed as a complex adaptive system, introduces a degree of uncertainty in understanding and predicting its behavior, similar to the way the dynamics of any complex system can be challenging to predict. This resonates with the theme of irreducible uncertainty in Alicia Juarrero's work.
Viewing Systems Holistically:
The brain as a complex system, Alicia Juarrero's discussion on global dynamics affecting components, and the overall approach to constraint programming all emphasize a holistic view. They suggest that understanding the whole system���be it the brain, a complex adaptive process, or a combinatorial problem���often requires more than just understanding its individual parts.
By drawing these connections, we can see how these seemingly disparate topics share common themes and principles, providing a richer and more integrated understanding of constraints, complexity, and adaptation.
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Language Sciences
Volume 19, Issue 2, April 1997, Pages 177-196
Language Sciences
The emergence of linguistic structure: Paul Hopper's Emergent Grammar Hypothesis revisited
Author links open overlay panelT. Weber
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Abstract
In his programmatic paper on Emergent Grammar (1987, BLS 13, 139���157), Paul Hopper challenges the discipline of linguistics by characterizing linguistic structure as being temporal, deferred, emergent, and the study of language as a necessarily political and disputed activity. I show that Hopper's arguments reflect, in the realm of linguistics, the influence of Jacques Derrida's philosophical deconstructivism that in the past decades has had a major impact on many other disciplines ranging from literary criticism to ethnography. I further contrast the deconstructivist view of language with competence approaches to language such as those by Noam Chomsky and John Searle and argue that the former raises theoretical questions that the latter have not yet responded to.
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This abstract discusses Paul Hopper's Emergent Grammar Hypothesis, which challenges traditional linguistics by characterizing linguistic structure as temporal, deferred, emergent, and politically disputed. The hypothesis resonates with the concept of emergent properties in complex adaptive systems, the brain, and constraint programming, which we've discussed previously.
In Hopper's view, linguistic structure is not fixed or predefined but emerges over time from use and adaptation. This mirrors the idea of self-organization in complex systems, where global structures or patterns emerge from local interactions. The claim that the study of language is politically disputed might reflect how constraints and context shape the evolution of language, similar to their role in complex systems.
The abstract also draws a connection between Hopper's arguments and Jacques Derrida's philosophical deconstructivism. Deconstructivism challenges the idea of absolute or fixed meanings, suggesting instead that meaning is context-dependent and constantly evolving. This is reminiscent of Alicia Juarrero's emphasis on context-sensitive constraints and the idea that the meaning or behavior of system components depends on the larger system they're embedded in.
The abstract contrasts this emergent, deconstructivist view of language with competence approaches by Noam Chomsky and John Searle. These approaches typically posit a fixed, innate linguistic structure or grammar, analogous to the idea of context-free constraints in a system.
Hopper's Emergent Grammar Hypothesis thus weaves together themes from our earlier discussions, highlighting the role of emergence, adaptation, and constraints in shaping linguistic structures. It also underscores the potential limits of reductionist or mechanistic approaches to understanding complex phenomena like language.
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Go into a little bit more detail, with examples.
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ChatGPT
Certainly, let's delve deeper into this using examples.
Paul Hopper's Emergent Grammar Hypothesis is a perspective of language that characterizes linguistic structure as temporal, deferred, and emergent. This viewpoint suggests that language is not a fixed entity but rather something that arises based on how it's used in context.
For example, consider the evolution of slang or colloquial expressions over time. These language variations often arise from specific cultural or societal contexts and evolve based on repeated use. A word like "selfie" emerged from cultural changes and technological advancements (i.e., the widespread use of smartphones with front-facing cameras), reflecting how language can adapt and evolve based on societal changes, a context-sensitive constraint in this case.
Comparing this to traditional models, Noam Chomsky's theory of generative grammar posits that language structure is innate and universal among humans, meaning that the basic principles of grammar are the same across all languages. This would be similar to a context-free constraint, as it applies universally, regardless of the specific language or cultural context.
The deconstructivist view of language, influenced by Jacques Derrida's philosophical ideas, challenges this notion of fixed meanings. It posits that meaning is not absolute but is instead dependent on context and interpretation. For instance, the word "freedom" might have different connotations in different political, historical, or cultural contexts. In a democratic society, "freedom" might be associated with individual rights and liberties, whereas in an authoritarian context, the same word might be associated with dissent or rebellion.
This reflects the context-sensitive nature of meaning in language and aligns with Alicia Juarrero's discussion on context-sensitive constraints in complex adaptive systems, where the behavior of system components (words, in this case) depends on the larger system (the socio-cultural context) they are embedded in.
Hopper's Emergent Grammar Hypothesis and the deconstructivist view of language therefore offer a perspective on language as a complex adaptive system, shaped by both local interactions (e.g., individual use of language) and global dynamics (e.g., societal and cultural changes). This aligns with our earlier discussions on the role of emergence, adaptation, and constraints in shaping complex systems.
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Deep belief networks and cortical algorithms: A comparative study
for supervised classif i cation
Yara Rizk, Nadine Hajj, Nicholas Mitri, Mariette Awad���
Department of Electrical and Computer Engineering, American University of Beirut, Beirut, Lebanon
a r t i c l ei n f o
Article history:
Received 23 March 2017
Revised 17 January 2018
Accepted 17 January 2018
Available online 3 March 2018
Keywords:
Deep learning
Deep belief networks
Cortical algorithms
a b s t r a c t
The failure of shallow neural network architectures in replicating human intelligence led the machine
learning community to focus on deep learning, to computationally match human intelligence. The wide
availability of increasing computing power coupled with the development of more eff i cient training algo-
rithms have allowed the implementation of deep learning principles in a manner and span that had not
been previously possible. This has led to the inception of deep architectures that capitalize on recent
advances in artif i cial intelligence and insights from cognitive neuroscience to provide better learning
solutions. In this paper, we discuss two such algorithms that represent different approaches to deep
learning with varied levels of maturity. The more mature but less biologically inspired Deep Belief
Network (DBN) and the more biologically grounded Cortical Algorithms (CA) are i rst introduced to give
readers a bird���s eye view of the higher-level concepts that make up these algorithms, as well as some of
their technical underpinnings and applications. Their theoretical computational complexity is then
derived before comparing their empirical performance on some publicly available classif i cation datasets.
Multiple network architectures were compared and showed that CA outperformed DBN on most datasets,
with the best network architecture consisting of six hidden layers.
? 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an
open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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The article you've referred to is a comparative study of two deep learning algorithms, Deep Belief Networks (DBN) and Cortical Algorithms (CA), with a focus on supervised classification tasks. Let's dissect the abstract to gain a clearer understanding:
Deep learning:
The authors mention that the limitations of shallow neural network architectures have led the machine learning community to focus more on deep learning to better emulate human intelligence.
Deep Belief Networks (DBN):
DBNs are a type of generative probabilistic model typically composed of multiple layers of latent variables ("hidden units"), with connections only between layers but not within a layer. DBNs are considered more mature in terms of their development and application, but they are less biologically inspired.
Cortical Algorithms (CA):
As the name suggests, these are algorithms that draw their inspiration more directly from the workings of the brain. The specifics aren't mentioned in the abstract, but it's likely they aim to model the hierarchical and recurrent structures observed in the brain's cortex.
Computational complexity:
The authors provide both a theoretical computational complexity analysis of these algorithms and an empirical performance comparison on public classification datasets.
Results:
Multiple network architectures were compared, with the results suggesting that CA outperformed DBN on most datasets. The most effective network architecture consisted of six hidden layers.
It's important to remember that the abstract doesn't cover the full details of the study. To get a more comprehensive understanding, it would be necessary to read the full paper. The abstract does, however, indicate that the authors' focus is on exploring the strengths and weaknesses of two different approaches to deep learning, with an eye towards both theoretical and practical considerations.
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1. Introduction
In an endeavor to replicate human level intelligence, artif i cial
intelligence (AI) research has fused insights from the i elds of com-
puter science, cognitive neuroscience, computational science, and a
litany of others to produce algorithms that perform with increasing
eff i cacy on what is arguably the core element of intelligence:
learning.
Notable among the many learning algorithms in AI are artif i cial
neural networks (ANN) and their many variants. ANN are collec-
tions of interconnected artif i cial neurons that incrementally learn
from their environment and attempt to mimic some of the basic
information processing processes in the brain. Their function is
def i ned by the processing performed at the neuron level, the con-
nection strengths between neurons (synaptic weights), and net-
work structure (organization and linkage of neurons) [1]. It is the
latter that resides at the core of the discussion presented herein.
Throughout their evolution, discussed in more details in the
next section, shallow ANN still suffer from multiple issues in the
context of complex applications requiring a higher level of abstrac-
tion. However, with the rapid increase in processing power, the
opportunitytosuccessfullyimplementthecomputationally
demanding designs of deeper architectures has recently emerged.
The development of eff i cient training algorithm such as Hinton
et al.���s greedy algorithm [2] has also helped ANN���s resurgence.
Furthermore, i ndings in computational neuroscience have led to
increased interest in deep, biologically inspired architectures
[3���5] which adhere more faithfully to neuro-scientif i c theories of
the human brain���s topology.
In this paper, we limit the scope of our comparative study to
two- nowadays popular- algorithms: Hinton et al.���s Deep Belief
Networks (DBN) [2], and Cortical Algorithms (CA) [6]. While many
other deep architectures have been developed, including long
short-term memory for sequential data processing and convolu-
tional neural networks for image processing, this comparative
study compares feedforward architectures. Specif i cally, DBN, one
of the more eff i cient deep architecture training algorithms is com-
pared to CA, a feedforward architecture with more biologically
faithful properties. Deep neural networks (DNN), specif i cally
DBN, is presented as the state of the art of ANN in their traditional
forms with network topologies built from layers of neuron models
but with more advanced learning mechanics and deeper architec-
ture, without modeling the detailed biological phenomena consti-
tuting human intelligence. Maintaining a high-level abstraction of
the biological modeling, results in simpler mathematical models
for DBN compared to CA. On the other hand, CA represents the shift
towards incorporating more biologically inspired structures than
DBN, like cortical columns and inhibiting and strengthening learn-
ing rules, as outlined by Edelman and Mountcastle���s work [7].
The structure of the paper is such that Section 2 summarizes the
history of ANN while Sections 3 and 4 review the fundamental con-
cepts and learning schemes of DBN and CA, respectively. Section 5
derives both algorithms��� theoretical computational complexity.
Finally, Section 6 presents an empirical comparison on classif i ca-
tion tasks before concluding with closing remarks in Section 7.
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ChatGPT
ChatGPT
The introduction of the study sets up a discussion on the development and comparison of Deep Belief Networks (DBN) and Cortical Algorithms (CA), two deep learning algorithms. Let's breakdown the key points:
Artificial Intelligence and Learning:
The authors mention how the goal of replicating human-level intelligence has led to advancements in AI and learning algorithms, focusing specifically on artificial neural networks (ANNs).
Artificial Neural Networks:
ANNs are a collection of interconnected artificial neurons that learn from their environment. Their functioning is defined by processing at the neuron level, the connection strengths between neurons (synaptic weights), and network structure. The authors mention that despite the evolution of ANNs, traditional "shallow" ANNs face challenges when dealing with complex applications requiring higher levels of abstraction.
Deep Architectures:
With increased processing power and development of efficient training algorithms, deep architectures have been given more attention. Findings from computational neuroscience have sparked an interest in deep, biologically-inspired architectures.
Scope of the Study:
The study is a comparison of Hinton et al.'s Deep Belief Networks (DBN) and Cortical Algorithms (CA). While other deep learning architectures exist, the authors have chosen to focus on these two due to their popularity, efficiency, and relevance to the discussion of biologically-inspired deep learning architectures.
Comparison of DBN and CA:
The authors describe DBN as state-of-the-art ANNs that use advanced learning mechanics and deeper architectures, but without detailed modeling of biological phenomena. On the other hand, CA is presented as more biologically-inspired, incorporating structures such as cortical columns and learning rules based on inhibitory and strengthening processes.
Structure of the Paper:
The paper will delve into the history of ANNs, review the fundamentals of DBN and CA, derive theoretical computational complexities of both algorithms, and finally present empirical comparisons on classification tasks.
From this introduction, it is clear that the paper aims to provide a comprehensive examination of DBN and CA, both theoretically and practically, in an attempt to better understand these architectures and their applicability to learning tasks.
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Artif i cial neural networks history
Before delving into the deeper network structures presented in
this paper, we will go over the evolution of neural networks from
their shallow beginnings to the complex structures that have
recently become popular.
2.1. Concepts from neuroscience
Despite the advances in neuroscience and technology that have
allowed for a detailed description of the structure of the brain, the
learning process in the brain is yet to be completely understood.
Biologically, the brain mainly consists of the cerebrum, the cerebel-
lum, and the brain stem [8].
The cerebral cortex, biologically def i ned as the outer layer of tis-
sue in the cerebrum and believed to be responsible for higher order
functioning, is an association of an estimated 25 billion neurons
interconnected through thousands of kilometers of axons propa-
gating and spreading about 1014synapses simultaneously [9],
arranged in six layers and divided into regions, each performing
a specif i c task [10].
82Y. Rizk et al./Applied Computing and Informatics 15 (2019) 81���93
Though it is not very clear how certain areas in the brain
become specialized, it is known that multiple factors affect the
functional specialization of the brain areas such as structure, con-
nectivity, physiology, development and evolution [11]. Neurons,
considered the basic element in the brain, have different shapes
and sizes but are all variations of the same underlying scheme,
i.e. they start the same general-purpose function but become spe-
cialized with training [12]. While dendrites are the site of reception
of synaptic inputs, axons convey electrical signals over long dis-
tances. Inputs to neurons cause a slow potential change in the state
of the neuron; its characteristics are determined by the membrane
capacitance and resistance allowing temporal summation [13].
Studies showed that the organization of the cortex can be
regarded as an association of columnar units [14,15], each column
being a group of nodes sharing the same properties. Learning in the
human brain is mainly performed using plastic connections,
repeated exposures and i ring and inhibition of neurons. In a sim-
plif i ed manner, information l owing in the cortex causes connec-
tions in the brain to become active, over time, with repeated
exposures these connections are strengthened creating a represen-
tation of the information processed in the brain. Moreover, inhibi-
tion of neurons- physically def i ned as prohibiting neurons from
i ring- partly account for the forgetting process [16].
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ChatGPT
ChatGPT
In this section of the paper, the authors provide a brief overview of the evolution of artificial neural networks (ANNs) and discuss some concepts from neuroscience that relate to ANNs.
2.1. Concepts from Neuroscience
The authors start with a basic introduction to the structure of the brain, mentioning that the brain primarily consists of the cerebrum, cerebellum, and brain stem.
They then describe the cerebral cortex, the outer layer of the cerebrum. This part of the brain is thought to be responsible for higher-order functioning and contains an estimated 25 billion neurons interconnected through axons, creating around 10^14 synapses. The cortex is arranged in six layers and divided into regions, each performing a specific task.
There are many factors that influence the functional specialization of different brain areas, including structure, connectivity, physiology, development, and evolution. Neurons, which are considered the fundamental units of the brain, start with the same general function and become specialized with training.
The authors then describe the organization of the cortex in terms of columnar units, with each column being a group of nodes (neurons) sharing the same properties.
Learning in the human brain is primarily performed using plastic connections, repeated exposures, and the firing and inhibition of neurons. Information flow in the cortex causes certain brain connections to become active and over time, with repeated exposures, these connections are strengthened, thereby creating a representation of the information processed in the brain.
Inhibition of neurons, which prevents neurons from firing, partly accounts for the process of forgetting. This is a simplified explanation of the complex learning processes in the human brain.
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Shallow beginnings
At a nodal level, ANN started with the simplif i ed McCulloch-
Pitts neural model (1943) [17], which was composed of a basic
summation unit with a deterministic binary activation function.
Successors added complexity with every iteration. At the level of
activation functions, linear, sigmoid, and Gaussian functions came
into use. Outputs were no longer restricted to real values and
extended to the complex domain. Deterministic models gave way
to stochastic neurons and spiking neurons which simulated ionic
exchanges. All these additions were made to achieve more sophis-
ticated learning models.
At the network level, topologies started out with single layered
architectures such as Rosenblatt���s perceptron (1957) [18], Widrow
and Hoff���s ADALINE network (1960) [19] and Aizerman���s kernel
perceptron (1964) [20]. These architectures suffered from poor
performance and could not learn the XOR problem, a simple but
non-linear binary classif i cation problem. This led to the introduc-
tion of more complex networks starting with the multilayer per-
ceptron (Rumelhart, 1986) [21], self-recurrent Hopf i eld networks
(1986) [22], self-organizing maps (SOM or Kohonen networks,
1986) [23], adaptive resonance theory (ART) networks (1980s)
[24] and various others which are considered shallow architectures
due to the small number of hidden layers.
Successive iterations incrementally improved on their prede-
cessors��� shortcomings and promised higher levels of intelligence,
a claim that was made partially feasible due to the hardware���s
improved computational capabilities [25] and due to the develop-
ment of faster and more eff i cient training and learning algorithms.
Learning mechanics, whether supervised (back propagation) or
unsupervised (feed forward algorithms), matured in parallel and
allowed for better performance in a varied set of specif i c tasks.
Nonetheless, the compound effect of the innovation targeting all
aspects of these shallow networks was not enough to capture true
human intelligence while large computational needs throttled the
progress of deeper networks.
2.3. Shallow networks��� limitations
Supervisedlearningpresentsmanychallengesincluding
the curse of dimensionality [26] where the increase in the number
offeaturesandtrainingsamplesmakeslearningmore
computationally demanding. Furthermore, non-linear data is more
diff i cult to divide into classes due to the inherent feature overlap.
Unable to position themselves as strong AI models- general intel-
ligent acts as def i ned by Kurzweil- which can faithfully emulate
human intelligence, ANN lagged Support Vector Machines (SVM)
[27] in the 1990���2000s.
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ChatGPT
ChatGPT
In this section, the authors discuss the development of artificial neural networks (ANNs) from their shallow beginnings and some limitations of these early networks.
Shallow Beginnings:
ANNs started with the simplified McCulloch-Pitts neural model (1943), which consisted of a basic summation unit with a deterministic binary activation function. Later iterations added complexity to this model, introducing activation functions like linear, sigmoid, and Gaussian functions. The outputs of these functions extended to the complex domain, and deterministic models gave way to stochastic neurons and spiking neurons, which simulated ionic exchanges.
The early network topologies started with single-layered architectures such as Rosenblatt���s perceptron (1957), Widrow and Hoff���s ADALINE network (1960), and Aizerman���s kernel perceptron (1964). These early architectures had limited performance and could not learn to solve the XOR problem, a simple but non-linear binary classification problem. This led to the development of more complex networks like the multilayer perceptron (Rumelhart, 1986), self-recurrent Hopfield networks (1986), self-organizing maps (Kohonen networks, 1986), adaptive resonance theory (ART) networks (1980s), and others. However, these are still considered shallow architectures due to their small number of hidden layers.
Each successive iteration improved on the shortcomings of their predecessors and promised higher levels of intelligence. These promises were partially realized due to improved computational capabilities of hardware and the development of faster and more efficient training and learning algorithms. Learning mechanics, including supervised learning (like backpropagation) and unsupervised learning (like feed-forward algorithms), matured and allowed for better performance on specific tasks. However, even with all these improvements, shallow networks could not fully capture true human intelligence, and the high computational demands limited the development of deeper networks.
Shallow Networks��� Limitations:
The authors also discuss the challenges and limitations of shallow networks. One such limitation is the curse of dimensionality, which states that as the number of features and training samples increases, learning becomes more computationally demanding. Another issue is that non-linear data is harder to classify due to feature overlap.
Shallow ANNs were unable to position themselves as strong AI models, which can faithfully emulate human intelligence. In the 1990s and early 2000s, support vector machines (SVMs) outperformed ANNs.
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The impending era of beta-amyloid therapy: Clinical and research considerations for treating
vascular contributions to neurodegeneration
A R T I C L E I N F O
Keywords
Alzheimer���s disease
Vascular dementia
Cerebral amyloid angiopathy
Treatment
The dawning of a new era of disease-modifying therapy for Alz-
heimer���s disease (AD) may be imminent. For the fi rst time, positive re-
sults from more than one trial of beta-amyloid lowering therapy have
been published. Increasingly, the data suggest that removing beta-
amyloid plaques from the brain may reduce the rate of functional
cognitive decline by approximately one quarter. If conf i rmed, this will
revolutionize care for dementia. This potential breakthrough will
impose new obligations for the assessment of vascular contributions to
cognitive decline and dementia (VCID), new potential dangers, and new
opportunities to invigorate clinical trials for VCID.
The controversy surrounding the United States (U.S.) Food and Drug
Administration (FDA) approval and marketing of Biogen���s aducanu-
mab���against the recommendations of their expert advisory panel, and
marked by deviations from the FDA���s own protocols according to its
internal review and a congressional investigation���obscured the
remarkable fact that for the fi rst time a drug had been proven in clinical
trials to effectively remove senile plaques in living people. Aducanumab
was granted accelerated approval by the FDA based on its ability to
reduce amyloid plaque load, a proposed surrogate treatment marker.
However, critics pointed out that the evidence linking beta-amyloid
removal to better cognitive function was weak. Despite the FDA
approval, U.S. Medicare declined to cover costs of the drug in routine
practice. The European Union declined to approve it at all. With little
hope of a market developing for aducanumab, Biogen stopped promot-
ing it. A previous editorial in Cerebral Circulation-Cognition and Behavior
urged caution in accepting Biogen���s interpretation of the results and
pointed out implications for VCID research [1].
More recently, lecanemab has been reported to reduce decline in the
Clinical Dementia Rating Scale Sum of Boxes (CDR-SB) by 27% in a
phase 3 trial [2], and donanemab has been reported to reduce decline in
Integrated Alzheimer���s Disease Rating Scale by 32% in a phase 2 trial
[3]. By comparison, aducanumab reduced decline in CDR-SB by 22% in
the EMERGE trial but did not reduce decline in the ENGAGE trial [4]. On
January 6, the FDA announced approval for lecanemab under the same
accelerated approval process that was used for aducanumab. Whether
lecanemab will gain traction in the marketplace remains to be seen. The
E.U. has not made a decision yet on lecanemab, and U.S. Medicare has
not evaluated it yet for coverage for seniors. However, given the
increasing evidence of a statistically signif i cant, but modest, effect on
slowing cognitive decline, it seems more and more likely that mono-
clonal antibody treatments will be entering clinical practice soon.
If use of anti-beta-amyloid monoclonal antibody therapy becomes
widespread, it will obligate clinicians to accurately diagnose cerebral
amyloid angiopathy (CAA), a common cause of VCID, to reduce risk for
amyloid-related imaging abnormalities-edema (ARIA-E) and -hemor-
rhage (ARIA-H). CAA appears to be the main risk factor for ARIA [5].
Although most ARIA events are silent, detected on imaging only, and can
be managed by dose reduction with slow resumption starting at a lower
dose, a few percent of events are symptomatic and can lead to serious
injury or death [6]. The lower reported incidence of ARIA in trials of
lecanemab relative to aducanumab (Table 1) raised hopes that this may
be less of a concern for lecanemab. This hope was undermined, however,
by a recent report of fatal intracerebral hemorrhage and CAA-related
vasculitis in a patient treated with intravenous thrombolysis for an
ischemic stroke while receiving lecanemab in open-label extension [7].
Another patient in the open-label extension phase had a cerebral hem-
orrhage and died while taking anticoagulation for atrial fi brillation [8].
We suggest caution when considering the use of lecanemab in patients
taking anticoagulants, pending more data, consensus recommendations,
and labeling by drug regulatory authorities. We recommend that
post-marketing studies and registries be created to learn more about the
risk for adverse events on these drugs.
1 / 1
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In this article, the authors are discussing the potential advent of a new era of disease-modifying therapy for Alzheimer's disease (AD), centered around beta-amyloid lowering therapies.
Key Points:
Beta-Amyloid Therapies
: Positive results from multiple trials of beta-amyloid lowering therapies suggest that removing beta-amyloid plaques from the brain may reduce the rate of functional cognitive decline by about a quarter. If this is confirmed, it would significantly change the approach to dementia care.
Aducanumab Controversy
: The US FDA's approval of Biogen's aducanumab, which goes against their expert advisory panel's recommendations, has stirred up some controversy. Although clinical trials proved the drug effective in removing senile plaques in living people, critics argued that the evidence linking beta-amyloid removal to improved cognitive function was weak. The drug was not approved by the European Union and was not covered by the U.S. Medicare. Biogen has since stopped promoting it.
Lecanemab and Donanemab
: More recently, lecanemab and donanemab have shown promise in reducing cognitive decline by 27% and 32% respectively in their respective trials. The FDA approved lecanemab via the same accelerated process used for aducanumab, but it's unclear if the drug will be accepted in the marketplace.
Risk Factors
: Widespread use of anti-beta-amyloid monoclonal antibody therapy would require clinicians to accurately diagnose cerebral amyloid angiopathy (CAA), a common cause of vascular contributions to cognitive decline and dementia (VCID), to reduce risk for amyloid-related imaging abnormalities-edema (ARIA-E) and -hemorrhage (ARIA-H).
Adverse Effects
: There is also a concern about serious adverse effects such as intracerebral hemorrhage and CAA-related vasculitis in patients receiving these therapies. The authors recommend caution, especially in patients on anticoagulants, and suggest the creation of post-marketing studies and registries to learn more about the risks associated with these drugs.
In conclusion, while beta-amyloid therapies may offer a new direction in Alzheimer's treatment, they come with new responsibilities, potential dangers, and implications for future research. Careful consideration and further investigation are needed.
1 / 1
Functional and structural brain connectivity: Are they reproducible in cerebral small
vessel disease?
Cerebral small vessel disease (SVD) is important due to its associa-
tion with numerous outcomes relevant to function and quality of life as
we age, including mood, mobility, stroke, dementia, and death [1,2].
SVD is very common among older adults: white matter hyperintensities
(WMH), an MRI manifestation of SVD, are seen in 65-96% of partici-
pants in study populations with mean ages 60-74 years [3]. WMH vol-
ume progression rates range from 4-37%/year in older adults [4].
However, WMH are not present only in older adults���they are detected
across a wide age range from young adulthood upward [4].
Given that SVD is typically detected by neuroimaging and often oc-
curs in the absence of symptoms, this indicates a long latent period in the
pathophysiology of the disease. This provides a wide potential time
window for interventions designed to prevent progression to clinically
overt symptoms. Disappointingly, few treatments have been demon-
strated to be effective for this purpose in randomized controlled trials,
with the exception of intensive blood pressure control among those with
hypertension which has been shown to reduce WMH progression and
reduce risk of Mild Cognitive Impairment (MCI) and a composite
outcome of MCI or dementia [5,6]. Thus, there is a need for additional
treatments for SVD. Furthermore, there is a need to better understand
both the pathophysiology of SVD and who is at high risk of SVD to
prioritize them for interventions. Meeting each of these needs requires
longitudinal studies with repeated measures and thus valid, reproduc-
ible biomarkers to measure changes in cerebrovascular health over time
and with treatment.
In this issue of Cerebral Circulation- Cognition and Behavior, Tozer
and colleagues report on testing the reproducibility of network-specif i c
structural and functional connectivity in participants with SVD as
compared with age-matched controls [7]. Brain connectivity is expected
to decline with declining cognition and with greater neuropathology.
Although there have been studies on reproducibility of functional [8,9]
and structural brain connectivity [10] measures, the reproducibility
studies on participants with SVD are limited. This study gives important
insights into the reproducibility of network-specif i c brain connectivity
in older adults with SVD.
The authors found that across multiple brain networks, structural
connectivity demonstrated good reproducibility for both SVD patients
and controls. Regarding functional connectivity, reproducibility was
good across multiple networks for controls, but not among the SVD
patients. Overall, structural connectivity measures appeared more
reproducible than functional connectivity measures, and the reproduc-
ibility of the functional connectivity did not appear to depend on
average connectivity nor on the reproducibility of the structural
connectivity.
Deriving reliable and reproducible brain connectivity-based bio-
markers has been diff i cult. One reason is that with brain connectivity
studies there is no standard method of data acquisition or analysis [11,
12]. There are several methods for calculating both the functional
connectivity (ROI [13] or seed-based [14] methods and data-driven
methods [15]) and for calculating structural connectivity based on
diffusion imaging (streamline tractography and probabilistic tractog-
raphy [12]). Tozer, et al. collected multi-echo resting-state fMRI data
and processed and analyzed the data using SPM and the CONN toolbox
[13] for calculating functional connectivity, and they collected single
b-value diffusion data and used streamline tractography for calculating
structural connectivity [16]. Thus, one thing to keep in mind is that the
reproducibility results they report are valid only for a data set acquired
and processed with similar methods. Given this limitation, the results
discussed here will be useful in developing biomarkers for functional
and structural brain connectivity.
A key contribution of this work is its provision of preliminary evi-
dence of reproducibility of network-specif i c connectivity rather than
global metrics of brain connectivity. For example, the authors found that
the control limbic, salience, somatomotor, and visual networks all had
structural connectivity with intraclass correlation coeff i cients (ICCs)
���0.82, indicating good to excellent reproducibility, and the control
default mode network (DMN) and frontoparietal network (FPN) had
structural connectivity ICCs around 0.65, indicating moderate repro-
ducibility. They also found that DMN had the greatest reproducibility for
functional connectivity in both SVD and control participants. It should
be kept in mind that differences in reproducibility by network were not
tested statistically. Thus, this work provides good candidate network-
specif i c reproducibility differences to test in future, larger studies.
This is important, because while global functional connectivity repro-
ducibility is poor in SVD participants [16], if functional connectivity
reproducibility is better in a specif i c network, it may be a more attrac-
tive candidate biomarker.
The fi ndings that the SVD patients may have greater variability in
their network-specif i c functional connectivity than the controls allow
for the intriguing possibility that this variability could prove to be a
biomarker of the disease. The authors did not statistically test differ-
ences in functional connectivity between SVD patients and controls, and
it should be noted that the 95% conf i dence intervals for the ICCs in these
two groups overlapped. Thus, whether Tozer and colleagues��� results
represent true differences between SVD patients and controls needs to be
evaluated in future studies with larger sample sizes well-powered to
detect such an effect. Nevertheless, recent biology of aging research has
pointed to increasing variability in biomarkers as complex body systems
Contents lists available at ScienceDirect
Cerebral Circulation- Cognition and Behavior
journal homepage: www.sciencedirect.com/journal/cerebral-circulation-cognition-and-behavior
https://doi.org/10.1016/j.cccb.2023.100175
Received 16 June 2023; Accepted 3 July 2023
Cerebral Circulation- Cognition and Behavior xxx (xxxx) xxx
2
deteriorate with aging and preceding critical transitions which often
presage collapse [17]. Longitudinal study designs would be required to
demonstrate increasing network functional connectivity variability in
SVD patients over time.
Another key limitation of this study is that in this small study sample
(N=25), women were underrepresented, and racial and ethnic diversity
was limited. These limitations to generalizability should be addressed in
future studies especially given that women, as compared to age-matched
men, and some ethnoracial groups are likelier than others to have WMH
and experience WMH progression [4].
While there are ongoing efforts to develop biomarkers for SVD and
for vascular contributions to cognitive impairment and dementia (VCID)
more broadly including the MarkVCID [18,19] and HARNESS [20]
consortia, this paper makes a meaningful contribution to the literature
by adding to the evidence regarding structural connectivity in SVD and
providing preliminary evidence regarding functional connectivity as a
potential biomarker in SVD.
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This paper is discussing the need for more research into Cerebral small vessel disease (SVD) and the potential usefulness of structural and functional brain connectivity as biomarkers in SVD research.
SVD is very common among older adults and is associated with numerous functional and quality of life outcomes such as mood, mobility, stroke, dementia, and death. It is often detected in the absence of symptoms, implying a long latent period in the disease's pathophysiology. This offers a potential time window for preventative interventions.
However, few treatments have been shown to be effective for this purpose in randomized controlled trials, other than intensive blood pressure control among those with hypertension, which has been shown to reduce white matter hyperintensity (WMH) progression and reduce the risk of Mild Cognitive Impairment (MCI) and a composite outcome of MCI or dementia. There is thus a need for additional treatments for SVD and to better understand both the pathophysiology of SVD and who is at high risk of SVD.
In this study, the authors investigate the reproducibility of structural and functional brain connectivity measures in participants with SVD. The authors found that structural connectivity demonstrated good reproducibility for both SVD patients and controls. However, functional connectivity showed good reproducibility across multiple networks for controls but not among the SVD patients.
The findings that the SVD patients may have greater variability in their network-specific functional connectivity than the controls are promising. This variability could potentially prove to be a biomarker of the disease. However, this needs to be evaluated in future studies with larger sample sizes.
Despite the limitations of this study, such as the small sample size and lack of representation from women and racial and ethnic diversity, it makes a meaningful contribution to the literature by adding to the evidence regarding structural connectivity in SVD and providing preliminary evidence regarding functional connectivity as a potential biomarker in SVD.
1 / 1
Adjustable Convergence Rate Prescribed Performance with
Fractional-Order PID Controller for Servo Pneumatic Actuated
Robot Positioning
Mohd Iskandar Putra Azahar, Addie Irawan
��� , R.M.T. Raja Ismail
Robotics, Intelligent Systems & Control Engineering (RiSC) Research Group, Faculty of Electrical & Electronics Engineering Technology, Universiti
Malaysia Pahang, 26600 Pekan, Pahang, Malaysia
a r t i c l e i n f o
Keywords:
Pneumatic actuator
adjustable convergence rate
fi nite-time prescribed performance control
pneumatic robot
a b s t r a c t
This study presents the method for optimal error tracking in position control for a servo pneu-
matic actuated robot grasper system using a new adjustable convergence rate prescribed perfor-
mance control (ACR-PPC). It focuses on improving the feedback controller and the fractional-
order proportional-integral-derivative (FOPID) controller used for the position control of each
robot���s fi nger. Multiple features were considered such as tracking error, rising time, faster tran-
sient response with fi nite-time convergence, oscillation reduction, and pressure stabilization in
the pneumatic system. Experiments were conducted using a single fi nger of a tri-f i nger pneu-
matic gripper (TPG) robot, actuated by a single proportional valve with a double-acting cylinder
(PPVDC). Two types of input trajectories were tested: step and sine wave inputs, which are com-
mon and critical for pneumatic systems. The results show that the proposed method eliminates
oscillation and achieves high tracking performance within the prescribed bounds and minimal
overshoot as well. The oscillation was suppressed with minimal overshoot and fast response was
achieved by tuning the formulated adjustable prescribe performance function, thus improving the
rising time response without signif i cant loss of performance.
1. Introduction
Pneumatic and hydraulic systems, known as fl uid dynamic actuators, are widely used in various industrial fi elds around the world
due to their high power-to-weight ratio and reliability. Pneumatic actuators of f er advantages over hydraulic actuators in terms of
cleanliness, simplicity of design, low cost, and immunity to electromagnetic interference. However, the compressibility of air results
in a lower natural frequency in pneumatic systems, making the airf l ows more complicated through valve pipeline and challenging to
enhance positioning and tracking accuracy. Additionally, the nonlinear and unpredictable behavior of pneumatic systems is caused by
the presence of frictional forces, making the control of motion in pneumatic servo systems (PSS) a challenging task. To achieve stability
List of abbreviations: PSS, Pneumatic Servo System; FLC, Fuzzy Logic Control; PPVDC, Pneumatic Proportional Valve with a Double-Acting
Cylinder; TPG, Tri-Finger Pneumatic Gripper; PID, Proportional Integral and Derivative; FOPID, , Fractional-order PID; FO, Fractional Order; PPC,
Prescribed Performance Control; PPF, Prescribed Performance Function; ARC-PPC, Adjustable Convergence Rate Prescribed Performance Control;
AC-PPF, Adjustable-Convergence Rate PPF; CPPC, Conventional Prescribed Performance Control; P + ID, Proportional Plus Integral and Derivative;
PSO, Particle Swarm Optimization; AHU, Air Handling Unit; MISO, Multiple Input and Single-Output; MCU, Microcontroller Unit; GS, Gripping
State; RS, Release State; IAE, Integral Absolute Error; ISE, Integral Square Error; ITAE, Integral Time Absolute Error.
��� Corresponding author.
E-mail address: addieirawan@ump.edu.my (A. Irawan) .
https://doi.org/10.1016/j.cogr.2023.04.004
Received 16 March 2023; Received in revised form 14 April 2023; Accepted 14 April 2023
Available online 27 April 2023
2667-2413/�� 2023 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article
under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
M.I.P. Azahar, A. Irawan and R.M.T. Raja Ismail Cognitive Robotics 3 (2023) 93���106
List of Symbols
���� ���� Decay Function
����Predef i ned Performance Function
�������� Initial Value of the Tracking Error at the Transient Interval
�������Maximum Allowable Range of the Tracking Error at the Steady-state Interval
���� 0 Predef i ned Convergence Time
����Adjustable Prescribed Function
�������� ( ���� =1 , 2) Scaling Factor
��� Convergence Rate
�� ����Upper Boundary Gain of the PPC
����Lower Boundary Gain of the PPC
�� ��������(0) Upper Limit of the Maximum Overshoot
��������(0) Lower Limit of the Maximum Undershoot
���� ( ���� ) New Transformed Tracking Error
���� ���� Reference Input of Displacement for the Rod-Piston Stroke
���� ( ���� ) Tracking Error
���� �������� Feedback Response of Displacement for the Rod-Piston Stroke
���� ���� Proportional Gain of the FOPID Controller
���� ���� Integral Gain of the FOPID Controller
���� ���� Derivative Gain of the FOPID Controller
����Integral Order of the FOPID Controller
����Dif f erential Order of the FOPID Controller
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This study discusses a new approach to achieve optimal error tracking in a servo pneumatic actuated robot grasper system using Adjustable Convergence Rate Prescribed Performance Control (ACR-PPC). This approach focuses on enhancing the feedback controller and the Fractional-Order Proportional-Integral-Derivative (FOPID) controller used for position control in each finger of the robot.
The main factors considered in this study include tracking error, rise time, quick transient response with finite-time convergence, oscillation reduction, and pressure stabilization in the pneumatic system. Experiments were carried out using a single finger of a tri-finger pneumatic gripper (TPG) robot, actuated by a single proportional valve with a double-acting cylinder (PPVDC). The research tested two types of input trajectories: step and sine wave inputs, which are common and critical for pneumatic systems.
The results indicated that the proposed method successfully eliminates oscillation and achieves high tracking performance within the prescribed bounds, along with minimal overshoot. The oscillation was suppressed with minimal overshoot and a fast response was achieved by tuning the formulated adjustable prescribed performance function, thus improving the rise time response without significant loss of performance.
Despite the benefits offered by pneumatic actuators, such as cleanliness, simplicity of design, low cost, and immunity to electromagnetic interference, their use comes with some challenges. The compressibility of air results in a lower natural frequency in pneumatic systems, making airflows more complicated through valve pipelines, which can be a challenge to enhance positioning and tracking accuracy. Also, the nonlinear and unpredictable behavior of pneumatic systems due to the presence of frictional forces makes the control of motion in pneumatic servo systems (PSS) a challenging task. The study addresses these challenges and proposes solutions to improve the performance and stability of such systems.
Overall, this study has made a substantial contribution to the field of robotics and control engineering by proposing a novel approach for error tracking and position control in servo pneumatic actuated robots. This research is likely to have applications in industries where pneumatic robots are used, and further research can focus on expanding these findings and applications.
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and ef i ciency in the face of these challenges, a strong control strategy for pneumatic systems is crucial. Signif i cant ef f orts have been
put forth to enhance control systems for pneumatic actuators, specif i cally to control the position of rod-piston by utilizing numerical
control theories, intelligent systems, and optimization techniques that are based on computing. Many dif f erent control strategies have
been developed to address the issues in PSS, including the combination of classical control systems, as well as integrated approaches
incorporating modern techniques such as cascading proportional integral derivative (PID) control, adaptive fractional-order control,
intelligent control, and data-driven control as well through computing method. Despite their potential, these feedback controllers
alone struggle to perform ef f ectively in nonlinear systems with uncertainties, like PSS. Prescribed performance control (PPC) [ 1 , 2 ]
architecture has recently gained popularity due to its simplicity, allowing the user to set error boundary parameters to enhance
feedback control performance. However, conventional PPC has some drawbacks such as the lack of fi nite time features and a fi xed
convergence boundary, which limits its practical applications in real-time scenarios.
Therefore, this study presents a method to optimize the pneumatic position control system using a newly formulated adjustable
convergence rate prescribed performance control (ACR-PPC). The focus of this study is to address the high nonlinearities inherent
in the servo pneumatic rod-piston position control of a single proportional valve with a double-acting cylinder (PPVDC), attached to
each fi nger of the tri-f i nger pneumatic grippers (TPG) robot. The fractional-order proportional-integral-derivative (FOPID) controller
is used as the feedback control platform, which is improved by the proposed ACR-PPC because it is currently used as the core
closed-loop controller for each fi nger proportional motion in the TPG system. Additionally, this study addresses the dynamic stability
and unmeasurable test rig constraints such as frictional force at the joint, slip at the joint, and the gravity force factor of the PPVDC.
Experiments were conducted using two types of input trajectories: step and sinusoidal inputs, which are considered common, practical,
and critical inputs for a PPVDC motion [3] .
In this paper, Section II covers the discussion on related works regarding control system design and solutions for pneumatic
systems. Section III provides information on the pneumatic actuated robot system and its operating principles that were used in this
study. Section IV outlines the methodology of the proposed ACR-PPC design, its formulation, and its integration with the FOPID
controller as the inner-loop controller. The results of experiments conducted using the TPG robot platform and their analysis are
presented in Section V, and the paper concludes with Section VI.
2. Related Works in the Design and Solution of Control Systems for Pneumatic Systems
A substantial rise in the use of pneumatic actuators in industrial automation has been noted particularly in the applications such
as machine precision and fl exible systems (robot manipulators and intelligent vehicles). This has led to an increased demand for ac-
curate position tracking performance and consistent positioning between the two endpoints of the pneumatic actuator���s stroke [ 3 , 4 ].
Furthermore, computational intelligence integrated with optimization strategy approaches are gaining traction as a solution, partic-
ularly in improving the performance of control systems. The function approximation-based intelligent design strategy is commonly
recognized as a prominent way to cope with the unknown nonlinearities and uncertainties. For instance, fuzzy logic control with
cascade strategy approach was used by [5] , whereby the single-input fuzzy P + ID controller was proposed for the dynamics control
with hysteresis compensation on the soft-pneumatic actuator. Fuzzy logic was also used by Chojecki and Ambroziak in their works
94
M.I.P. Azahar, A. Irawan and R.M.T. Raja Ismail Cognitive Robotics 3 (2023) 93���106
Table 1
List of equipment
Equipment Value
Pneumatic cylinder CKD Air Cylinder CAC4-A-50B-75-Y/Z
Pneumatic proportional valve Festo MPYE-5-1/4-010-B
Pneumatic pressure regulator & fi lter AirTAC SR200
Pneumatic pressure transducer Festo SPTW-P10R-G14-A-M12
Air compressor SWAN SVP202 Air Compressor
Rotary encoder Rotary encoder- 500ppr
as self-tuning tools for particle swarm optimization (PSO) algorithm in air handling unit (AHU) equipped with multiple actuators
[6] . The similar fuzzy logic-based self-tuning approach was also deployed in [ 3 , 7 ] using a hybrid strategy for a PSS in robot system.
However, an adaptive neural network was used to improve the performance of error tracking control on PSS in [8] . Most of the inte-
gration approaches perform an impressive tracking performance of more than 70% whenever compared to the conventional control
method without any intelligent system assistance. However, most of these systems are still in the of l ine and predetermined practices
which require further ref i ning in the real-time process to cater the unpredictable conditions.
In recent years, a lot of research on fractional order (FO) control systems has been conducted. Unlike traditional calculus which uses
integer orders of derivatives and integrals, fractional order calculus uses real-number orders. Integer-order derivatives and integrals
are just special cases of their fractional-order equivalents. In [9] , a fractional-order disturbance observer was proposed to estimate
mismatched disturbances, while a novel fractional-order sliding mode controller based on an observer was proposed to reduce tracking
inaccuracies and chatter. For instance, in [10] , an adaptive sliding mode control was improved with a fractional-order derivative
sliding surface and a switching-type reaching law, leading to less chattering and reduced energy consumption for targeted PSS. On
the other hand, discrete-time FO integral sliding mode control approach, proposed by [11] , was developed to stabilize pneumatic
artif i cial muscles with an antagonistic conf i guration, using a fractional-order exponential reaching law. FO approaches also done
by [ 5 , 12 ], whereby two solutions were proposed using FO integral sliding surfaces and dif f erent reaching rules to reduce reaching
time and improve system performance. Researchers have also integrated FO systems with other control systems such as intelligent
control systems to increase the dimensionality of the FO system. For example, a two-degree-of-freedom FO fuzzy PID controller was
proposed to improve PSS accuracy in [13] . The FOPID controller provides a signif i cant advantage over a typical PID controller by
having two additional tunable parameters. However, with more parameters, the tuning process is more dif i cult, especially if it was
done manually.
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This manuscript focuses on the development of an adjustable convergence rate prescribed performance control (ACR-PPC) to optimize error tracking in the position control of a servo pneumatic actuated robot grasper system. It particularly addresses the highly nonlinear pneumatic servo systems (PSS) attached to each finger of the tri-finger pneumatic grippers (TPG) robot.
The challenges in controlling PSS arise due to the compressibility of air, which results in a lower natural frequency, making airflow through the valve pipeline complex and tracking accuracy enhancement difficult. Moreover, the nonlinear and unpredictable behavior due to the presence of frictional forces also adds to the challenge.
The study incorporates a fractional-order proportional-integral-derivative (FOPID) controller as the feedback control platform to overcome these limitations. The proposed ACR-PPC enhances this controller to improve the response time and tracking accuracy of the system. The ACR-PPC allows for adjustable error boundary parameters, which helps to counter the lack of finite-time features and fixed convergence boundaries in the conventional prescribed performance control (PPC).
The researchers conducted experiments using two types of input trajectories: step and sinusoidal inputs, common inputs for a PPVDC motion. The results of the study demonstrate that the proposed method eliminates oscillation and achieves high tracking performance within the prescribed bounds and minimal overshoot.
The manuscript also discusses related works in the control system design and solutions for pneumatic systems, focusing on the use of computational intelligence integrated with optimization strategy approaches. The related works cover various approaches including fuzzy logic control with cascade strategy, adaptive neural network, and fractional order (FO) control systems.
Despite the significant strides made in improving PSS control, most of the existing systems require offline and predetermined practices, which limit their real-time adaptability. This study proposes an ACR-PPC method that provides a solution to this challenge, thereby making a significant contribution to pneumatic actuated robot system control.
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the tracking error to within a prescribed boundary region. This method has potential to replace or reduce the need of approximation
control approaches to cater the uncertainties in nonlinear control system structure such as position control on PSS.
3. Pneumatic Actuated Robot System and Its Principle of Operation
This section provides a comprehensive overview of the working principle of the tri-f i nger pneumatic gripper (TPG) system. The
TPG platform consists of three independently actuated pneumatic actuators as illustrated in Fig. 1 . The robot grasper operates in two
primary states: (1) the gripping state (GS) and (2) the release state (RS). The GS state can be proportioned up to the maximum point
as shown in Fig. 1 (a), and vice versa for the RS state as shown in Fig. 1 (b).
Each rod-piston pneumatic cylinder has a length of 75 mm, with a particular emphasis on the positioning of one rod-piston for
one fi nger. The main components of the platform are displayed in Table 1 . The control system design for this platform uses a multiple
input and single output (MISO) conf i guration and is implemented using a 32-bit microcontroller unit (MCU) running a real-time
95
M.I.P. Azahar, A. Irawan and R.M.T. Raja Ismail Cognitive Robotics 3 (2023) 93���106
Figure 1. TPG in (a) gripping state and (b) release state.
Figure 2. Schematic diagram for the hardware connection of a single fi nger of TPG robot
operating system. The MCU controls each rod-piston of each fi nger in the TPG robot through a proportional valve and considers
minimum two feedback signals, from the rotary encoder on the fi nger joint and the pressures from each pneumatic piston cylinder
to perform closed-loop control. The hardware schematic of the TPG robot control for a single fi nger connection is shown in Fig. 2 .
4. Controller Design
4.1. Adjustable Converge Rate Prescribed Performance Control
A limitation has been identif i ed in the fi nite-time prescribed performance function proposed and deployed in [24���26] , where
the convergence rate is fi xed. The concept of an adjustable convergence rate presents a more promising solution to overcome the
limitations of a fi xed rate, as introduced in [2] . This allows for the ability to vary and adjust or tune either the fi nite time of convergence
rate or the dif f erent transient rate settings. Therefore, the new adjustable convergence rate PPF (AC-PPF) formulation is introduced
as Eq. (1) as follows:
����( ���� ) = (����
0 ��� ������� )����
���� + ������� (1)
96
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This section discusses the implementation of the tri-finger pneumatic gripper (TPG) system and the design of the proposed controller.
The TPG system operates on two primary states: the gripping state (GS) and the release state (RS). The system comprises three independently actuated pneumatic actuators, each controlling one finger of the gripper. The control system employs a multiple input and single output (MISO) configuration, implemented through a 32-bit microcontroller unit (MCU) running a real-time operating system. The MCU oversees the movement of each rod-piston through a proportional valve and takes feedback from a rotary encoder located at each finger joint and the pressures from each pneumatic piston cylinder for closed-loop control.
The controller design involves the use of an adjustable convergence rate prescribed performance control (ACR-PPC). Conventional finite-time prescribed performance function often suffers from a limitation where the convergence rate is fixed, meaning the controller's response time cannot be adjusted to cater for different systems or conditions. The ACR-PPC proposed in this research overcomes this limitation, allowing for an adjustable convergence rate. This means the time it takes for the controller to reach the desired control output or the different transient rate settings can be varied and adjusted. The adjustable convergence rate prescribed performance function (AC-PPF) is given by the equation:
����( ���� ) = (����_0 ��� ������� )����_���� + ������� (1)
This introduces a much-needed flexibility to the control system, making it more adaptable to real-time changes and unforeseen conditions. In essence, this methodology provides a promising way to deal with the challenges in controlling highly nonlinear pneumatic servo systems.
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a signif i cant negative overshoot was observed at around 0.2 s, as depicted in Fig. 13 (a). During the delay ignition test, as shown in
Fig. 13 (b), the pressure distribution for the CPPC-FOPID was not as smooth as the ACRPPC-FOPID but was much more stable than
that of the FOPID. This is due to the impact of gravity force and the friction force between the TPG platform���s joint region when the
rod-piston expands, pushing the TPG fi nger downward, and retracts, pulling it upward, during sequential GS and RS operations. This
outcome suggests that the ACRPPC-FOPID outperforms both the FOPID and CPPC-FOPID in terms of pressure distribution.
6. Conclusion
The proposed ACR-PPC with FOPID controller strategies were introduced and verif i ed through multiple experiments on the TPG
platform, ensuring the system���s transient and steady-state error performance. One noteworthy conclusion from this study is that
the ACR-PPC ef f ectively eliminates the initial oscillation that leads to mechanical vibration following each rod-piston positioning
transient and addresses the phase-shifted issue in the FOPID controller. The improved performance in various input conditions, such
as sinusoidal input trajectories, demonstrates that the proposed control strategy can handle the constant time lag or phase shift
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M.I.P. Azahar, A. Irawan and R.M.T. Raja Ismail Cognitive Robotics 3 (2023) 93���106
Figure 13. The pressure dif f erence in between both cylinder chambers performance started at (a) 0 s and (b) 4 s
between the desired input and feedback response. Additionally, the absence of approximation in the proposed ACR-PPC reduces the
complexity of controller design in terms of methodology. Since pneumatic systems are also known for their highly nonlinear behavior,