Integrated structural/control design of micro-positioner for boring bar tool insert

This paper presents a method to improve the performance of an electromechanical system by employing an integrated structural/control design methodology. In their previous work, the authors have introduced an intelligent boring bar, utilizing a micropositioner (composed of a piezoelectric actuator and photosensitive detectors) to actively control a cutting insert. The purpose of the micro-positioner was to improve precision of boring process by isolating the boring tool from tool vibrations and compensating tool position for geometric errors. The controller for the micro-positioner was designed only after the mechanical design was finalized. As a result, the controller performance was acceptable, but overall performance of the system was limited by its mechanical structure. This paper introduces a new approach of concurrent design of the mechanical structure and the controller to enhance the performance of the micro-positioner. With the proposed method, both mechanical and control design variables are determined simultaneously in a single optimization problem. The objective and constraint equations quantify system performance, stability, actuator saturation, and life expectancy as explicit functions of the design variables. The proposed integrated methodology both simplifies the design process of the prototype boring tool and enhances its performance over the previous design, as shown by simulation results.