Closed-Loop Control of a Micropositioner Using Integrated Photodiode Sensors

A closed-loop control system with photodiode position sensors has been implemented in a microball bearing supported linear electrostatic micromotor to improve accuracy and reliability. The fabrication sequence of the previously developed micromotor was modified to integrate a photodiode-based position sensing mechanism. Proportional control law is used in the control system and device step response is analyzed for several step sizes at various maximum applied voltages by varying the constant of proportionality. Two critical functions for micropositioning applications have been demonstrated; the device can establish a necessary frame of reference for coordinate-based positioning and autonomously respond to arbitrary disturbances. The closed-loop position control system presented in this work illustrates the feasibility and functionality of smart microsystems using integrated feedback sensors