Research On The End Effect And Control Of The PM Linear Motor Used In The Electric Discharge Machining

In the field of the electric discharge industry manufacture, the conventional "rotation motor + threaded spindle" movement mode is the leading condition, that gets the indirect linear movement. Because of its lower velocity and precision, this mode is not fit for the demand of the higher velocity and precision technology of the numerical control machining.The direct drive mode based on the permanent magnet (PM) linear motor can be provided for the best performance of the electric discharge machining. It finishes the high speed and high acceleration cutting, and solves the difficult problem of manufacturing deep slot mould. However, the disturbance of the linear motor's end effect is the main factor of affecting the machining performance.First, in this paper the design of PM linear motor is optimized. The electromagnetic finite element software is programmed using the ANSYS and the thrust is calculated that the linear motor's end effect brings. In the vector control, both the no-load thrust and the thrust with the different current are calculated, and the end effect influenced by the current magnitude is analyzed. The low-frequency slot harmonic modulation is used to weaken the end effect or decrease the wave of the thrust, and the many projects are designed or the better project is selected. Besides, the motor control system based on the digital signal processor (DSP) is analyzed. The hardware circuit about the DSP system is designed. The DSP control software is programmed on the field magnetic orientated control and the space vector pulse width modulation (SVPWM), that establishes the'basis for implementing the modern control principle. The method of compensating the end effect is presented. Finitely, the experiment device of measuring the thrust is designed, and the experiment data of the thrust is obtained.In conclusion, when the current of the winding is increased, the tendency of the end effect-thrust is unchangeable, the no-load end effect is the main part of the PM linear motor's end effect. The more poles mode, the unequal pole width mode; the low-frequency slot harmonic modulation mode and the mode of changing end magnetic conductance are presented, and these designing method can efficiently weaken the end effect and decrease the wave of the thrust. The high-speed calculation function and the inner integrated peripherals of DSP are used. DSP can satisfy the real-time demand of the advanced control principle when these are implemented.