High-Accuracy Contouring Control Based On Vibration Reduction

In order to improve machining efficiency and accuracy of parts with complex surface, feed drives of machine tools need to deliver fast motions for rapid positioning of tool or workpiece. However, the inertial forces generated by acceleration and deceleration of machine tool apartment excite the structural mode and cause residual vibrations, which lead to poor surface quality of the parts and make servo system unstable. On the one hand, the vibrations cause the position error of feed drives and increase the tracking error of machine table which usually attached with tools or probe. On the other hand, the vibrations cause the distortion of the tools or probe. So it is meaningful to improve the contour accuracy by reducing the vibration caused by inertial forces.In order to solve the above issues, this research is curried out with the following line:Modeling and identification of the feed drives. In this part, the rigid model of feed drives is identified by unbiased least square technique and the friction characteristics are identified using a Kalman filter. Moreover, the pole place controller is designed to improve the bandwidth and tracking accuracy of feed drives.Vibration avoidance technologies of machine tools. In this part, input shaping and drive based active damping technology are implemented to reduce vibration. Compared to active damping technology, input shaping is easier to complement and have better robustness for modeling uncertainty.Real-time contour error estimation and contouring control of multi-axis control systems. Although input shaping can effectively avoid vibrations, it distorts the toolpath in multi-axis control systems due to added time delays. Based on the transfer function of axis drives, the contouring error caused by input shaping and limited bandwidth can be predicted and compensated to the control loop to improve the contouring accuracy. Experiments are conducted on an X-Y platform to validate the estimation accuracy and control performance. The results indicate that the proposed integrated input shaping and contour error compensation module can reduce the vibration of machine parts and results accurate contouring of desired path.At last, “FiveAxisServoControl” software is developed based on the work above. The software can be used to identify the model of axis drives and control the single-axis or multiaxis feed drive systems.