Passivity-based control of magnetostrictive materials

In this article, velocity and position controllers for magnetostrictive materials are designed and discussed. Magnetostrictive materials are a competitive choice for micro-positioning actuation tasks because of the large force and strain they provide. Unfortunately, they are highly nonlinear and hysteretic, which makes them difficult to control. In this article, the passivity approach is used to establish stability for velocity control. Using a physical argument, passivity of the system under discussion is proved. No model for magnetostrictive material is used in this proof and the result can be used in any hysteresis model for the material. This result is used to develop a stabilizing velocity controller. For position control, it is shown that a PI controller can provide stability and tracking if the hysteretic plant satisfies certain conditions. It is shown that these conditions are satisfied for the Preisach model under mild assumptions. Using this result, a class of stabilizing position controllers is identified. The velocity and position controllers are evaluated experimentally and their performances discussed.