Research On Key Control Tcehnology And Application Of Modern Linear Motor

The linear motor can directly transform electrical energy into linear moving mechanical energy, the mechanical friction and losses can be reduced in this system without transmission mechanisms. Therefore, it is much suitable for direct drive system. Optimal motor design and driving technology are two main developing directions of the linear motor. The latter involves power electronics and automatic control, and it is the key to improve the adjusting speed performance for motor. It also becomes the focus of the study for modern linear motor.The dissertation has researched following several areas around the driving technology of linear motor:1. The principle, structure, classification, development and the applications of linear motor in the fields of military, civil, industrial automation and transportation are introduced. Then, the vlf control, field oriented control (FOC) and direct thrust control (DTC) for linear motor are described, after that the research background and the main contents are pointed out.2. The mathematic model of the permanent magnet synchronous linear motor (PMLSM) is built, and then several types of FOC for PMLSM are introduced based on this model. Space vector pulse width modulation (SVPWM) is realized by using TI’s floating-point digital signal processor (DSP) TMS320F28335. Generation and adverse effects of dead-time effect are analyzed based on the structure of the inverter, and the dead-time error voltage vector is deduced to describe the dead-time effect. Since the linear motor is mostly used in short-stroke direct drive system, dead-time effect has great effect on control performance due to its relative low operation frequency. The voltage vector compensation and time compensation methods used to eliminate the dead-time effect are investigated by the experiment. The results indicate that the dead-time compensation methods can reduce the current distortion and thrust ripple.3. The servo control system is built with air-cored PMLSM, and the performance of position-speed-current closed-loop system and position-current closed-loop system are discussed by experiment. Improved position-speed-current closed-loop servo control system which built with id=0FOC is proposed. Fuzzy adaptive PI controller is used in servo control system instead of the conventional speed regulator, and position error caused by the parameters of PI controller is analyzed in orientation process. Feedforward compensation correction devices of speed, acceleration, load damping and viscous friction are designed. It is validated by the experiment on tubular air-cored PMLSM. The speed and position are measured, and the measured results of speed and position indicate that the speed overshoot is reduced by fuzzy adaptive PI controller and position tracking error is significantly reduced by feedforward control. The research indicates that the dynamic performance and control accuracy of PMLSM can be improved by adopting the improved control methods combined with fuzzy adaptive PI control and feedforward control.4. Initial mover position estimation of PMLSM is discussed in the research. Due to the saturation saliency effect of PMLSM, initial mover position can be estimated in stationary state based on inductance variation. Fluctuating high-frequency signal injection is used in this research. Mover position information can be extracted effectively by the improved extreme value method. The experimental results show that the improved high-frequency injection method is more accurate and reliable than available pulse-voltage injection method for the initial mover position estimation.5. The sensorless FOC system for PMLSM based on back electromotive force (back-EMF) method is built in the research. The dead-time compensation and mean value of flux linkage method are validated to eliminate the flux linkage drift effectively, so the accuracy of mover position estimation is improved significantly. The influence of estimation position due to parameter variation is analyzed by experimental results. Due to Back-EMF sensorless method can’no"t get the mover position of PMLSM at zero-speed, method of current closed-loop and speed open-loop is adopted in startup state, and system is switched to speed-current closed-loop control model when the linear motor speed reached the threshold. By adjusting the q-axis current, a smooth and stable transition between speed open-loop control and speed closed-loop control is realized.6. A dynamic operation wireless control system in urban rail test line is designed. Drive circuit, signal detection circuit and protection circuit of vehicle inverter are researched in order to meet the high reliability requirements for this system, and control program design and implementation process for inverter are also proposed. In order to contact each part of system efficiently, host computer control system is built with LabVIEW. Finally, the communication of the urban rail test line is tested. By analyzing the experimental results, the method of double-examination is proposed to solve the command transmission error, and reliable operation of the test line is guaranteed at last.