Precision Positioning Control by Using Frictional Compensation of Linear Ball Guideway

Abstract

In recent positioning devices, linear ball guideways are used instead of air static guideways. Frictional force is caused because the linear ball guideways has rolling elements. As the rolling friction shows very complex behavior, it is very difficult to compensate friction force in positioning control. Therefore, for achieving high precision positioning, precise frictional model is needed. In this study, nonlinear frictional model is proposed for expressing the rolling frictional behavior of the linear ball guideway. Moreover, the model is used to positioning control and the effectiveness of the method using the model is verified. The nonlinear frictional model is based on the frictional model called Bristle model. The frictional characteristic changes depending on displacement. However, the Bristle model does not capture it. Therefore, the proposed nonlinear frictional model newly introduces to the change in the characteristic of spring coefficient on the size of displacement. The nonlinear frictional model is used as feed-forward control and the friction compensation is implemented. As the result, the positioning error is decreased compared with the general PID control.