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

Previous papers by these authors presented an effort to develop a prototype boring tool, utilizing a piezoelectric actuator and photosensitive detectors to actively control a cutting insert. This paper describes an effort to redesign the system using an integrated structural/control methodology. The purpose of the micro-positioner is to improve precision by: i) isolating the finish cutter from tool vibrations, ii) absorbing energy from the tool during rough cuts, and iii) compensating for small geometric or thermal errors. These characteristics enable tools with large length to diameter ratios (L/D) without loss in machining precision, and facilitate automated tool changes. The integrated structural/control design variables consist of the structural shape of the mechanism, including the piezoelectric actuator, and the controller feedback gains. The design variables are determined simultaneously in a single optimization problem. The objective and constraints 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 improves the performance over the original design, as shown by simulation results.