Stable Visual PID Control of Redundant Planar Parallel Robots

This chapter presents an image-based Proportional Integral Derivative (PID) controller for a redundant overactuated planar parallel robot; the control objective is to drive the robot end effector to a desired constant reference position. The main feature of the proposed approach is the use of a vision system for obtaining the end effector position. This approach precludes the use of the robot forward kinematics. The Lyapunov method and the LaSalle invariance principle allow assessing asymptotic closed-loop stability. Experiments in a laboratory prototype permit evaluating the performance of the closed-loop system.