Three Dimensional Position Control of a Parallel Micromanipulator Using Visual Servoing

摘要

This paper presents a computer-vision based position controller for a highly non-linear parallel piezohydraulic micromanipulator: in addition to its non-linear kinematics the micromanipulator experiences hysteresis and drift induced by piezoelectric actuators. The controller consists of a decoupling matrix that provides decoupled translations (xyz) in the task frame and three Single Input Single Output (SISO) PI controllers for the translations. Position measurement is performed by a vision system that determines the x and y coordinates of the end-effector using a modified Hierarchical Chamfer Matching Algorithm (HCMA) and the z position using a depth-from-defocus method. Experiments show that the proposed controller is capable of servoing the parallel micromanipulator with a sub-micron accuracy at a sampling rate of 18 Hz.