Dynamic electromechanical coupling resulting from the air-gap fluctuation of the linear motor in machine tools

• The calculation methods of motor thrust considering the air-gap fluctuation caused by the mechanical vibration were put forward. And the analytic expression of motor thrust was established.
• The influence of gap fluctuation caused by the mechanical vibration on the motor thrust was discussed. And its effect on the dyamic precision of feed system was analyzed.
• The mechanism of the electromechanical coupling considering motor air-gap fluctuation was revealed.

This paper investigates a dynamic electromechanical coupling resulting from the air-gap fluctuation of the linear motor in machine tools. The modes of the mechanical vibration are analyzed firstly in the linear motor feed system. Then the influence of mechanical vibration on the air-gap fluctuation is researched. Based on the Maxwell's equation and energy method, the analytical expression of the motor thrust is established considering the air-gap fluctuation. Then we discuss the effects of air-gap fluctuation on the motor thrust. At last, the dynamic electromechanical coupling caused by the air-gap fluctuation is theoretically analyzed and verified by experiments. The results show that the mechanical vibration can affect the characteristics of the motor thrust conversely causing the fluctuation of the motor air-gap. The air-gap fluctuation can produce new thrust harmonics. These new thrust harmonics excite mechanical system again, and then the electromechanical coupling loop is formed, leading to a worse dynamic precision of the feed system. In addition, the couplings will aggravate with the increase of velocity and load.