Integral Sliding Mode Control for Fast Tool Servo Diamond Turning of Micro-Structured Surfaces

Fast Tool Servo (FTS) diamond turning is a promising machining process for fabricating high precision micro-structured surfaces. However, the dynamics of FTS affects its performance and causes form error in the machined surfaces, thus shortening the useful bandwidth of the FTS for precision machining. In this paper, an Integral Sliding Mode Control (ISMC) algorithm is proposed to control the FTS in order to achieve the desired closed-loop dynamics. The robustness of the ISMC to disturbance and model uncertainties or variations is ensured by the implementation of disturbance estimation and an integral switching control action. The influence of the FTS dynamics can thereby be minimized by modifying the tool path offline with the inverse of the desired dynamics. Experiments on machining of typical micro-structured surfaces show that the proposed method is effective in reducing the FTS dynamics induced form error in the machined surface.