CHAPTER 8 CONTROLLER SELECTION AND IMPLEMENTATION Controller Selection Motion of the robot was generated by the actuators based on velocity, position, and vision information. For each of the systems, the most important aspect was that the controller keep the system stable for all operations. The accuracy of each of the controllers was governed by the steady-state errors as specified by the performance criteria. Although not specified as values, the desire was that the response time of each joint be as fast as possible. Thus, a maximum bandwidth was requested for each control procedure. Also, these controller systems were to be designed with minimum reaction to disturbances such as noise, drift, and external loads. In the case of the citrus-picking robot, the manipulator was constructed before the controllers were considered. The control problem involved designing controllers for a system which could not easily be altered to gain optimum performance. Thus, the performance was limited by the manipulator rather than the controller. Approximations of the joint open-loop transfer functions were established in Chapter 6. The open-loop velocity transfer functions for all joints were approximated as second-order systems as demonstrated by KvOh Gv(s) = [2 s +25hO)hS + Oh (8-1) Open-loop position and vision dynamics were approximated as second-order systems with integrators with the following form: