Control systems for a robot gripper

Abstract

The fundamental issues in modeling and "executive level" control of a three-link, three-joint robotic arm-gripper system are presented. First, a mathematical model of the mechanism is developed. This model is coupled with a model of a DC permanent magnet motor, as an actuator, to obtain an overall system model. This model is used to design and simulate five local control systems for the independent control of the joints in the arm portion of the arm-gripper system. The control systems developed are a simple feedback system, a position servo system, a position servo system with direct gravity compensation, a state-feedback control system designed based on pole placement, and a PID controller. The effect of gravity moment upon the system response is examined, and the performance of each control system is analyzed. The performance of each controller is quantified by the settling time, percent overshoot, and steady-state error metrics. The position servo system with gravity compensator is found to be the best overall control system approach.