added header for feedback + feedforward

Author: ProfessorAtomicManiac

docs/section-7/control.md

@@ -8,13 +8,12 @@ Or is there?
 
 Control systems are the solutions to the three problems mentioned above. They help programmers manipulate motors to a great deal of control and flexibility. When designing a control algorithm for a robot mechanism, there are a number of different approaches to take. These range from very simple approaches, to advanced and complex ones. Each has tradeoffs. Some will work better than others in different situations, some require more mathematical analysis than others.
 
+## Feedback and Feedforward
+
 There are two fundamental types of mechanism controllers that we will cover here:
 
 **Feedforward control (or “open-loop control”)** refers to the class of algorithms which incorporate knowledge of how the mechanism under control is expected to operate. For example, using physics we can account for the force of gravity, friction, and other forces. Using this “model” of operation, the control input is chosen to make the mechanism get close to where it should be. In general, feedforward control is required whenever the system requires some constant control signal to remain at the desired setpoint (such as position control of a vertical arm where gravity will cause the arm to fall)
 
-!!! note
-    The Feedforward control section is still being worked on, so only Feedback control is discussed.
-
 **Feedback control (or “closed-loop control”)** refers to the class of algorithms which use sensors to measure what a mechanism is doing, and issue corrective commands to move a mechanism from where it actually is, to where you want it to be. Even with unlimited study, it is impossible to know every force that will be exerted on a robot’s mechanism in perfect detail. So feedback control is used to correct the error not covered by feedforward control.
 
 !!! Note