Design of a Microprocessor-Based Adaptive Control System for Active Vibration Compensation Using PMN Actuators

Abstract

This thesis is written to address a pressing need in vibration control for machine tools. Machine tools are the platform of machining operations. Precision machining has been the focus to enhance product quality and improve productivity in every sector of the U.S. industry to maintain its competitiveness in the world market.<P>A mechatronic system is employed in this thesis investigation, incorporating both mechanical and electronic aspects. This thesis focuses on the design of a control system architecture that features a closed feedback loop involving the machining process, a variable-impedance transducer, microprocessor-based parameter adjustment mechanisms, and PMN actuators. The designed control system serves as a critical part to ensure the success of a previously designed tool post structure. Three basic system components are a sensing system, a phase-shift manipulator and a self-tuning gain adapter. In the sensing system, the high precision variable impedance tranducer detects the tool displacement in micro-scale. Recognizing the time delay between the control action and the detected tool vibratory motion, an innovative approach to use phase-shift to replicate the time delay is formulated. An information model is incorporated to manipulate the needed shift in real time. To balance the need between maintaining system stability and achieving maximum vibration attenuation, a self-tuning mechanism is employed to adjust the level of control energy supplied by the power amplifier to the PMN actuators. Regression analysis is utilized to obtain an empirical relationship between the measured tool vibratory magnitude and the appropriate actuation, thus completing an adaptive control loop. The control system realization, both hardware and software, is completed in this thesis work with success.<P>Initial results from this thesis investigation have been fruitful. Significant findings include: PMN actuators are excellent electro-mechanical devices for active vibration control; phase shift and self-tuning are two unique mechanisms in controlling time delay and magnification gain; and the microprocessor-based controller developed in this thesis work is a great success and signifies the importance of interdisciplinary research across the mechanical and electrical engineering domains.