Papers by Author: Zhi Yong Li

Abstract: In this paper, a space vector PWM (SVPWM) control algorithm based on BP neural network is proposed to cope with the complex calculation required in SVPWM through analyzing SVPWM for three phase voltage fed inverter. This method uses the strong nonlinear approximation ability of the BP neural network to fit the eqivalent segment SVPWM modulated wave, modulate with the triangular carrier wave, and then get the control signals of the three phase voltage inverter. A simulation model for PMSM control system was developed by MATLAB/Simulink with the neural network Toolbox. The results show that the BP neural network based SVPWM algorithm makes the motor control system has a smaller current harmonics and torque ripple, and reduce the amount of computation in digital control system with strong guidance.

Abstract: The initial gap in electrochemical machining (ECM) is a significant affection parameter for ECM process and machining stability. A tool setting detection system based on LabVIEW technology has been designed to realize the rapid and accurate pinpoint between two electrodes since the initial gap of micro-ECM is usually only a few microns to tens of microns. The system can not only efficiently complete tool setting detection in micro-ECM, but also real-time monitor the change of processing current. 120 comparative experiments have been conducted to evaluate the erosion amount of workpiece material, the reliability, repeatability and positioning accuracy of micro-ECM process in the conditions of wet tool setting compared with dry tool setting. The experimental results have shown that adopting the tool setting detection system designed in this paper, the erosion rates of cathode and anode after 120 repeated wet tool setting experiments were only 0.21% and 0.02%, the positioning accuracy and repeatability can completely meet the requirements of tool setting in micro-ECM, and greatly improve the efficiency of the micro-ECM.

Abstract: Alumina ceramics film which has high hardness, wear resistance and erosion resistance can be obtained using micro arc oxidation on the surface of aluminum alloy. The process parameters have great influence on the corrosion resistance of alumina ceramics film prepared by micro arc oxidation. In this research, the alumina ceramics film was gotten using micro arc oxidation with different process parameters. The corrosion resistance of ceramics coating prepared by micro arc oxidation on the surface of aluminum alloy was investigated by putting the samples into sodium chloride solution of the concentration 3.5%.The influence regularity of process parameters such as current density, impulse frequency, duty ratio and process time on the corrosion resistance of alumina ceramics film was researched. This can provide basis for the optimization of process parameters.

Abstract: Alumina ceramics film which has high hardness, wear resistance and erosion resistance can be obtained using micro arc oxidation on the surface of aluminum alloy. The process parameters have great influence on the surface morphology of alumina ceramics film prepared by micro arc oxidation. In this research, the alumina ceramics film was gotten using micro arc oxidation with different process parameters. The surface morphology of ceramics film was analyzed using scanning electron microscope (SEM). The SEM photograph was processed using ImageJ software. The dimensions of holes diameter and porosity on the surface of ceramics film were investigated. The influence regularity of process parameters such as current density, impulse frequency, duty ratio and process time to the surface morphology of alumina ceramics film was researched. This can provide basis for the optimization of process parameters.

Abstract: The active power filter with LCL filter (LCL-APF) possesses the advantages of wide bandwidth of compensation and a small amount of switching ripples. A direct power control (DPC) method of LCL-APF without harmonic current detection technology is proposed. Not only the complex detection of load harmonic current and compensation harmonic current is omitted, but also the total rate of harmonic distortion of grid side is reduced from 27.7% to 1.12%. To overcome the disadvantages of resonance caused by three-order LCL filter, the power of active power damping is added in the power controller. Thus, the dynamic control performance of LCL-APF is improved, as stable waveforms of grid current and power after 0.04s proved. Meanwhile, a modified DPC control loop is formed. Simulation results prove that the proposed method is correct and feasible. In view of the fact that it is rapid and accurate, especially the power level of 150kW, so it is suitable for the distributed generation system.

Abstract: To improve the mechanical properties of the EDM electrode material, the electroforming process for fabricating copper-nanozirconia (ZrO₂) particles composite aided by ultrasonic has been presented. In this research, some vital process parameters such as concentration of ZrO₂, rotational speed and ultrasonic frequency have been evaluated. Two inspection criteria, content of ZrO₂ and micro hardness of deposited layer were employed to evaluate the fabrication quality of copper-nanozirconia (ZrO₂) composite material. The experimental results indicate that nanocomposites grains electroformed aided by ultrasonic are refined. Their organizations are more uniform and dense, the surface is flatter and the microhardness of nanocomposites is significantly improved.

Abstract: In this study, we firstly developed a numerical electrochemical micro-machining (EMM) setup. Furthermore, the effects of five vital process parameters, applied voltage, electrolyte type, electrode shape and diameter, electrode feed rate on micro-seams machining accuracy and process stability were evaluated. The experimental results show that: Wire electrodes machining accuracy is higher than that of sheet electrode. With the wire electrodes diameter decreased from 0.2mm to 0.06mm, micro-seam width is reduced by 36.55%. With the wire electrode feed rate increased from 0.2mm/min to 0.6mmm/min, micro-seam width is reduced by 44.2%. Sheet electrodes machining stability is better than that of wire electrode. The number of machining stability of sheet electrode is 25% higher than that of wire electrode in the condition of 8V applied voltage.

Abstract: This paper introduces a novel experiment platform for AC speed control system based on TMS320LF2407A. The system composition and the design method of hardware and software function modules are set forth. In this experimental platform, Users can carry out the experiments of many kinds of motor control strategy for induction motor, synchronous motor and the other motors. This experimental platform is transparent to hardware and is open to software system, and achieved good results in the practical teaching and research.

Abstract: This paper puts forward a novel design method of controller based on BP neural network, which is applied to the permanent magnet synchronous motor (PMSM) double closed loop speed regulation system of speed regulator, by using the neural network controller instead of traditional PID controller. It applies the nonlinear adaptive ability of neural network for optimizing the control parameters of PID controller for PMSM. The simulation model was established in Matlab/Simulink. The simulation results indicate that the neutral network PID controller, compared with the traditional PID, has strong robustness and adaptive ability to the model and environments, indicating the good dynamic and static characteristics and control effects.

Abstract: A novel algorithm of space vector PWM (SVPWM) based on artificial neural network is proposed in this paper, in order to cope with the complex calculation required in Space Vector PWM. It makes full use of the fast parallel computation and learning capability of ANN to shorten the time of calculation and reduce the harmonic composition and loss. The simulation model of vector control for permanent magnet synchronous motor drive system is built and simulated in MATLAB/Simulink. The simulation results show that the permanent magnet synchronous motor drive system based on artificial neural network SVPWM has more perfect performance than that based on traditional SVPWM controller in dynamic and static property, such as little torque pulses as well as robustness.