Ph.D. Proposal Presentation by
Tuesday, November 1, 2005
(Dr. Steven Y. Liang, Chair)
"Direct Feed Drive for Grinding Machine"
The objective of this study is to develop a methodology to control linear motor feed drives in cylindrical plunge grinding machines. One of the ever-present goals in manufacturing is to increase the levels of quality and accuracy of the parts being fabricated. Grinding, as an important finishing process, is of great practical relevance with respect to this objective and has imposed stringent requirements on grinding machine performance. As a promising technology, a linear motor direct feed drive discards the transmission system required for a conventional feed drive and therefore there exists no transmission associated error such as backlash, pitch error, etc. Also, the friction problem is greatly alleviated by the application of direct drive because of no transmission. In addition, direct drive is capable of achieving high acceleration and velocity which is hard to obtain using a conventional feed drive. In spite of these advantages, linear motors have not been able to totally replace conventional techniques. Resistance to utilizing linear motors may be ascribed to those drawbacks associated with linear motors such as: (1) Force ripple which originate from cogging, reluctance force and commutation error, (2) Cutting force disturbances directly acting on linear motor, and (3) Friction is still a problem although reduced compared to conventional drive. To become a viable feed drive technology, all of these factors should be overcome by explicitly taking each into account in the controller design.
The proposed research will focus on cylindrical plunge grinding because it is one of the most frequently used grinding processes.The overall objective of the proposed research is to develop a systematic methodology to enhance the direct feed drive performance for cylindrical plunge grinding machines under the effect of force ripple, friction and grinding force by systematic experiments, simulation, and sophisticated controller design. To achieve this goal, the proposed study includes: 1) Hybrid approach for friction compensation combining model-based with nonmodel-based approach; 2) Modeling and compensation of force ripple ; 3) Grinding force compensation; and 4) Controller implementation and performance evaluation.