Modeling and control of a magnetostrictive tool servo system

This paper addresses the modeling and development of a nonlinear control methodology for a magnetostrictive system. As an application of smart materials, magnetostrictive transducers can generate high mechanical strain with a broadband response and provide accurate positioning. Even though these properties characterize a good tool servo application in precision machining, the actuators contain significant magnetic hysteresis and are highly nonlinear when combined with 2/sup nd/ order dynamics of a tool fixture. Full utilization of these transducers generally requires an advanced controller as well as accurate model of the transducer dynamics in response to various inputs. At moderate to high drives, the magnetostrictive actuator develops highly significant hysteresis on top of the dynamics of a tool fixture. Many sophisticated control schemes have been proposed to deal with this nonlinearity. This paper presents the development of a sliding mode controller to control a tool servo system for various inputs in the presence of highly nonlinear dynamics.