Research On Ending-effects Thrust Ripples Of High Precision Permanent Magnet Linear Motor And Compensation Approach

Modern super-guality NC machines bring forward the demands of high speed and high precision to the servo feeding system. One of the most necessary methods to realize high speed and high precision is used direct drive of permanent magnet linear servo motor (PMLSM). Under the support of National Natural Science Fund Project and Liaoning Province Natural Science Fund Project, the thrust ripple caused by ending effect and its compensation control strategy for PMLSM are researched in this thesis. The main contents are as following:1. The PMLSM end effect without load and with the current contribution are analyzed and calculated, the equation of thrust ripple caused by ending effect is proposed based on vector control.2. The design theory of PMLSM based on permeance modulation is proposed. Using open slot, the wave of cogging permeance and ending permeance are well-proportioned modulated in one pole pitch respectively, which can effectively restrain ending and cogging effects of PMLSM and reduce thrust ripple to improve the positioning precision of servo system.3. The fractional-slot theory and permeance modulation are properly applied to the configuration design of PMLSM, the design theory of magnetic circuit and windings are provided for permeance modulate permanent magnet linear motor which used proper fractional-slot and special concentrated phase bands. A typical PMLSM with 12 poles is designed with idiographic parameters and optimized magnetic field, and the thrust ripples is measured.4. Because the PMLSM used for NC machine has the characteristic of short primary, long secondary and flexibility of installation with several motors' parallel drive, the PMLSM's design method of moving phases between 2 units is put forward. According the amplitude-phase characteristic of thrust ripples caused by ending effect, it is obtained the optimized degrees between 2 units' phases, which can farther restrain thrust ripple amplitude. The thrust ripples is measured on the 90 degree moving phase and the optimized prototype.5. In order to further improve the servo precision of linear feed system, according to the periodically characteristic of end effect, the quick compensation control strategy based on position and current compensation data is brought forward. The optimized prototype's compensation table is set up, which is compared with other prototypes.6. An B spline network is used as function approximator to observing thrust ripples to improve the compensation precision. The effectiveness of the control strategy is proved by simulation results.