Abstract
In this paper, we describe design of precise 3-axial servo controller for an inchworm mobile mechanism and simulation result of 1 axis control for checking the validity of the design. The inchworm mobile mechanism is composed of 6 piezoelectric actuators (PAs) and a pair of electromagnets (EMs). If one EM is fixed to a ferromagnetic floor, another EM can position X, Y, and Θ axes by 6 PAs. In previous study, we have developed 3-axial proportional-integral-derivative (PID) control with 50nm resolution for the mechanism with 4 linear encoders for measuring 3DoF motion of the free magnet precisely. However, we conclude that we need over 100ms of settling time because of mutual coupling effects among X, Y, and θ axes by PID controller. In this paper, we propose new design of servo controller to be robust against the disturbance and also reduce settling time, by using combination of bang-bang control and state feedback control. In this controller, we aim at establishment of 3-axial servo control in nanometer scale that can realize ±0.5μm positioning repeatability, and less than 10ms of settling time in 50μm×50μm of positioning range for getting sufficient working efficiency.
