High-precision control of linear actuators with nonlinear friction

In recent years, a high-precision stage control has received great attention due to the progress of nano-technology. A fast-response and high-precision control method based on the internal model control in the case where the controlled object has the integral characteristic is reported. The disturbance observer-based internal model control (DIMC) system has the advantages of no-overshoot, easy-design and simple-realization comparing to the conventional IMC method for the integral objects. However, an overshoot is generated when the model/plant mismatch exists. In the proposed method, since the plant model is explicitly included in the controller, the compensation for the dynamical change of the plant is easily realized by giving an adaptive identification mechanism to the plant model. Experimental results with an ultra-precision stage demonstrate that the proposed control system achieves high-precision positioning performance.