Research On The Analysis Of Detent Force And Control Strategies Of Permanent Magnetic Synchronous Linear Motors

The electrical energy can be transferred into linear motion by permanent magnetic synchronous linear motors (PMSLMs), and all intermediate transmission mechanism can be canceled. Therefore, the feeding system can drive load directly, and realize manufacturing procedure with high speed and high precision. Consequently, PMSLM is becoming the principal function device of super-quality NC machines, and has extensive application perspectives in NC systems with high speed and high precision,IC manufacture and packing devices, lithographic tools,and so on. However, in the PMSLMs, there exists thrust ripple caused by the load disturbance, the detent force generated by end-effect and slot-effect, and the perturbation of system parameters, which has negative effect on the positioning accuracy and the steadiness at low speed, and then becomes one of significant causes interfering with the widely use of the PMSLMs in industrial practice. This paper focused on how to weaken the negative effect of thrust ripple on the performance of the PMSLMs, and analyzed the occurrence reasons and the calculation methods of thrust ripple, and proposed the corresponding constructive design methods to reduce detent force and the control strategy to restraint thrust fipple, and performed experiments to verify the validity of the proposed methods above.Firstly, the detent force that is the main reason of thrust ripple was analyzed by the motor design methods. The analysis model of the magnetic field in the PMSLM was built by means of equivalent magnetizing current and Schwarz-Christoffel transformation, and the detent force was analyzed by Maxwell stress. The analysis results showed that the detent force could be divided into the end force caused by end-effect and the cogging force caused by slot-effect, and then the finite element models were set up to calculate the end force and the cogging force respectively, as the result, the corresponding constructive design methods were proposed.Secondly, the vector control theory,the kinematics model and the sinusoidal space vector Pulse-Width-Modulation (SVPWM) control technology were analyzed dividually, and then the mathematic simulation model of the servo system of PMSLM was built. Since the thrust ripple has great influence on the precision and steadiness of the velocity control, the sliding-mode control device of speed loop was designed. In order to reduce the chattering of the sliding-mode control, the disturbance observer was designed to estimate the disturbance of the servo system and the estimation was fed back to the output current of the sliding-mode control. Furthermore, the fuzzy control strategy was introduced to modify the amplitude of the switching control at real time, in order that the chattering of the control system was weakened, and at the same time, the robustness and the fast tracking performance were maintained.On the basis of the theory study above, the design and the realization of the software and hardware of the servo system of PMSLM based on the DSP was described in detail, and the experiments were made to verify the effectiveness of the proposed constructive design methods and control algorithms.