Chattering-free sliding mode control for the parallel mechanism of a virtual axis machine tool

The precision control of the virtual axis machine tool is still one of the biggest obstacles of the commercialization of the virtual axis machine tool in the precision processing, which impedes the utilization. It is becoming urgent to solve this problem. In this paper joint-space trajectory planning based on the cycloid movement to ensure the stability of the mechanism movement is conducted on the basis of the kinematics analysis of the parallel mechanism of the 6-DOF virtual axis machine tool. According to the characteristics of the control of the parallel mechanism of the virtual axis machine tool, a novel completely chattering-free sliding mode control system is designed to achieve the high precision control with the sliding function s instead of the sign function sgn(s). This control system is easy to design and implement, and it is not necessary to establish accurate mathematical model of parallel mechanism of virtual axis machine tool. The simulation of every branch control of the virtual axis machine tool shows that this control system has a good performance in tracking and anti-interference and can achieve the accurate control of branches of virtual axis machine tool.