Shi Wei Zhao

Bio: Shi Wei Zhao is an academic researcher from Hong Kong Polytechnic University. The author has contributed to research in topics: Switched reluctance motor & Magnetic levitation. The author has an hindex of 6, co-authored 16 publications receiving 128 citations.

A Novel Planar Switched Reluctance Motor for Industrial Applications

Abstract: This paper presents a novel two-dimensional (2-D) planar switched reluctance motor (PSRM) for position control applications. The proposed 2-D planar motor has the advantages of simple mechanical construction, high reliability, and the ability to withstand hostile operating conditions. Due to the unique structure of the planar motor's magnetic circuit, there is very little coupling between the X- and Z-axis, and no decoupling compensation is needed. It is expected that this innovative SR planar motion system will be an ideal replacement for traditional X-Y tables in industrial automation applications

A Novel Flux Linkage Measurement Method for Linear Switched Reluctance Motors

Abstract: The magnetic characteristics of a linear switched reluctance motor (LSRM) are important in its performance prediction and verification. Owing to the complicated magnetic paths, the measurement of the flux linkage for this type motor has drawn many researchers' attentions. In this paper, a new flux linkage measurement method for LSRMs is proposed to obtain the flux linkage characteristics of LSRMs using an online winding resistance estimation technique. Both the theoretical derivation and the actual implementation of the proposed method are addressed in this paper. In comparison with the search coil scheme and the static resistor scheme, experimental results confirm the validity and accuracy of this method. In short, the proposed method is simple, effective, and easy to be implemented. It is a practical solution for flux linkage measurement of LSRMs and other motors.

Magnetic Analysis of Switched Reluctance Actuators in Levitated Linear Transporters

Abstract: A novel linear magnetic levitated actuator using the switched reluctance principle is addressed in this paper. This actuator can be applied to precise motion control of automation machines. The proposed system has the advantages of a simple and robust structure, and direct drive capability. The contactless structure eliminates mechanical wear, friction, noise, and heat generation. To verify the feasibility of the proposed system, the magnetic levitated force is analyzed by magnetic circuit analysis (MCA) and by finite-element analysis (FEA). A prototype structure is fabricated, and experiments are performed with the actual hardware. Results of the MCA and the FEA are both compared with the results obtained from the hardware experiments. They all agree with the proposed design methodology. This paper can form a useful reference in the design of a mechanical structure for magnetic levitated switched reluctance actuators.

Position Estimation and Error Analysis in Linear Switched Reluctance Motors

Abstract: In this paper, a continuous position estimation scheme is presented for linear switched reluctance motors (LSRMs). The scheme uses diagnostic current injection into an unenergized phase to detect the motor position. This paper proposed that a new current integration index be used to quantify the measurement of current waveform. Hardware implementation results demonstrate the effectiveness of the proposed estimation scheme for the LSRM. This paper also performs a study on the accuracy of the estimated position. Through the detailed experimental data, the approach of polynomial fitting is compared with the lookup table with regard to characteristic curve representation. The estimation error distributions and their standard deviation show that the accuracy and precision are close between these two approaches.

Design and simulation of a linear switched reluctance generator for wave energy conversion

Abstract: This paper investigates the direct-drive linear switched reluctance generator for wave energy conversion. A double-sided linear switched reluctance generator is designed. Its nonlinear flux characteristics are simulated by finite element method. The excitation circuit of the linear switched reluctance generator is reviewed and the control algorithm for this generator is also discussed.

Dynamic Surface Control Using Neural Networks for a Class of Uncertain Nonlinear Systems With Input Saturation

Abstract: In this paper, a dynamic surface control (DSC) scheme is proposed for a class of uncertain strict-feedback nonlinear systems in the presence of input saturation and unknown external disturbance. The radial basis function neural network (RBFNN) is employed to approximate the unknown system function. To efficiently tackle the unknown external disturbance, a nonlinear disturbance observer (NDO) is developed. The developed NDO can relax the known boundary requirement of the unknown disturbance and can guarantee the disturbance estimation error converge to a bounded compact set. Using NDO and RBFNN, the DSC scheme is developed for uncertain nonlinear systems based on a backstepping method. Using a DSC technique, the problem of explosion of complexity inherent in the conventional backstepping method is avoided, which is specially important for designs using neural network approximations. Under the proposed DSC scheme, the ultimately bounded convergence of all closed-loop signals is guaranteed via Lyapunov analysis. Simulation results are given to show the effectiveness of the proposed DSC design using NDO and RBFNN.

Direct Adaptive Neural Control for a Class of Uncertain Nonaffine Nonlinear Systems Based on Disturbance Observer

Abstract: In this paper, the direct adaptive neural control is proposed for a class of uncertain nonaffine nonlinear systems with unknown nonsymmetric input saturation. Based on the implicit function theorem and mean value theorem, both state feedback and output feedback direct adaptive controls are developed using neural networks (NNs) and a disturbance observer. A compounded disturbance is defined to take into account of the effect of the unknown external disturbance, the unknown nonsymmetric input saturation, and the approximation error of NN. Then, a disturbance observer is developed to estimate the unknown compounded disturbance, and it is established that the estimate error converges to a compact set if appropriate observer design parameters are chosen. Both state feedback and output feedback direct adaptive controls can guarantee semiglobal uniform boundedness of the closed-loop system signals as rigorously proved by Lyapunov analysis. Numerical simulation results are presented to illustrate the effectiveness of the proposed direct adaptive neural control techniques.

Wave Energy Conversion

Abstract: The present invention is used as power for wave energy of the ocean, and relates to the use of the energy of the high-pressure sea water, the apparatus 10, which was generally converted to a water pressure of greater than greater than 800psi and preferably 100psi. Sea water of the high pressure generated by the device 10 may be transported through the pipe to shore for any suitable purpose. The device 10 includes a pump 13 operatively connected to the support to hang in the water body (1), the float 12, and the float (12). And the pump 13 comprises a piston 61 extending between the take entrance 47, the take-out chamber (49) and the take entrance 47 and the take-out chamber (49). The piston 61 includes a tube 63 having a flow passage 102 extending between the take entrance 47 and the take-out chamber (49). The piston 61 and the take-out chamber (49) are cooperating to form the expansion and the pumping chamber (100) to receive a contraction in accordance with the reciprocating motion of the piston. The piston 61 is operatively connected to the float (12) to be driven by upward movement of the float. The pump may be to process the water to pass by using the electrolytic process, to accept from a linear electric generator employed in the pump. Seawater, wave energy, buoyancy, pumps, water treatment

A Novel Four-Level Converter and Instantaneous Switching Angle Detector for High Speed SRM Drive

Abstract: A novel four-level converter and instantaneous switching angle detector for a high speed switched reluctance motor are proposed. Since the excitation time is very short compared to the general speed range of a high speed drive, the excitation current can not be built-up sufficiently. Also, the demagnetization current can be easily extended to the negative torque region. To obtain a fast current buildup and suitable demagnetization, a novel four-level converter is proposed. The proposed converter has an additional charge capacitor and an active power switch compared to a conventional asymmetric converter. The high voltage of the additional capacitor is applied to the phase winding in the fast excitation mode and the phase current is rapidly decreased during the recharging of capacitor in demagnetization mode. In addition, an instantaneous switching angle detector separated by main digital controller is designed for precise switching angle control. During high speed operation, rotor position error increases due to the constant sampling period of digital controller. The proposed instantaneous switching angle detector operates with optical encoders pulse and pre-set switching position regardless of sampling time. So, it determines the precise switching pattern without time delay from sampling time. The proposed high speed control system is verified by computer simulation and experimental results.

An analytical literature review of stand-alone wind energy conversion systems from generator viewpoint

Abstract: The purpose of this paper is to provide an analytical review of wind turbine-generator systems for stand-alone applications. The review focuses on variable-speed wind turbines, as the future trend in wind energy conversion, in contrast with the traditional fixed-speed wind turbines. Indirect-drive and direct-drive turbines are comparatively evaluated. The concerns about long-term availability of permanent magnet materials and its impact on the future of permanent magnet synchronous generator are addressed. Having cost and efficiency in mind, viability of indirect-drive squirrel cage induction generator for stand-alone wind energy conversion systems is discussed. As an efficient induction machine design, permanent magnet induction generator is also examined. Finally, the potential of using switched reluctance machine, as a generator, in a direct-drive wind turbine system is investigated.