A linear feedback control system is used in most control systems for positioning and trajectory tracking. There are sensors at each joint to measure the joint angle and velocity, and there is an actuator at each joint to apply a torque on the neighboring link. The readings from the sensors will constitute the feedback of the control system. By choosing appropriate gains we can control the behavior of the output function representing the actual trajectory generated. Minimizing the error between the desired and actual trajectories is our main concern. Figure 2 shows a block diagram for the controller, and the role of each of the robot modules in the system.
