The duplex-grinding machine for silicon wafer developed by SHI has achieved very accurate positioning of a tool tip at a scale of several tens of nanometers as well as high positioning stiffness. Our new positioning mechanism applied to the machine has adopted double V-shaped groove sliding guideways and a force operation type hydraulic actuator of high power and high resolution.

In the positioning mechanism where friction occurs, unstable phenomena such stick-slip caused by nonlinear friction generally deteriorate the accuracy of positioning. We have built the simulator of the positioning mechanism developed by applying the empirical equation that precisely states the friction characteristics. The simulator is used to understand the positioning characteristics and to optimize the mechanism and control systems.

This paper presents an outline of the simulator, the comparison between the experimental and simulation results, and the simulation performance, which has demonstrated an excellent nonlinear positioning behavior under friction.