Investigation of the dynamic electromechanical coupling due to the thrust harmonics in the linear motor feed system

In the linear motor feed system, all the intermediate transmission components are cancelled. Lots of thrust harmonics caused by the nonlinearity of drive circuit and motor itself directly act on the mechanical system, leading to the vibrations. Meanwhile, the mechanical vibrations also affect the characteristics of motor thrust through the full closed-loop control. There is a close coupling between the servo drive and mechanical system, affecting the dynamic precision of the feed system. Therefore in this paper, an analytical method, which is used to present the mechanism of the electromechanical coupling caused by the thrust harmonics and its effects on the dynamic precision, is explored for the linear motor feed system. The thrust harmonics and mechanical characteristics are calculated firstly. The interactions between the servo system and mechanical system are analyzed afterwards. Then the coupled equation is established and the coupled process is analyzed. Moreover, the influence of the coupling on the displacement fluctuation is discussed. The results show that the thrust harmonics will produce significant displacement fluctuations, which is actually an electromechanical coupling process. In addition, its effects will aggravate with the increase of the velocity. At last several measures are put forward to improve the dynamic precision of the feed system. The displacement fluctuation caused by thrust harmonics is decreased more than 90% by implementing an integrated compensation strategy. This work will provide the theoretical support for the analysis and optimization of the complex electromechanical couplings, especially for the linear motor feed system.