Dynamic error of CNC machine tools: a state-of-the-art review

The dynamic error of CNC machine tools, which often exceeds the quasi-static error at high-speed machining, becomes the main reason affecting the machining error of the sculptured surface parts. Although much research efforts have been dedicated to dynamic error, there is a lack of systematical summaries. In this review, firstly, the dynamic error is defined as the deviation of actual displacement of effector end of axis relative to reference displacement during feed motion. Secondly, according to the mechanical and control structure of the servo feed system, the dynamic error is divided into two components: dynamic error inside the servo loop (component 1) and dynamic error outside the servo loop (component 2). Based on the two components, the causes resulting in the dynamic error are analyzed from the points of view of the servo feed system itself and its input (setpoints). Thirdly, the basic strategies for reducing the dynamic error of individual axis, as well as for reducing the trajectory dynamic error by coordinating the dynamic error of individual axis, are summarized. Finally, the problems and future research directions on dynamic error are analyzed. It is concluded that resolving the contradiction between the setpoints and the servo feed system is still a great challenge for dynamic error in high-speed machining. To achieve high dynamic accuracy at high-speed machining, the control strategies on the dynamic error outside the servo loop should be further developed and integrated into dynamic error inside the servo loop-oriented control strategies. Meanwhile, the servo feed system itself and its input need to be investigated as a whole, so that the servo feed system of each axis can adapt to the differences and changes of the setpoints, and the differences in the servo dynamics of each axis can be considered in the setpoints.