Shi Wei Zhao

A Self-Tuning Regulator for the High-Precision Position Control of a Linear Switched Reluctance Motor

In the high-technology mass manufacturing industry, high-speed and high-precision motion is an indispensable element in the automated production machines. In recent years, there has been a growing tendency to employ direct drive permanent magnet linear synchronous motors in demanding motion applications. Although the overall performance is good, its implementation cost remains high. This is mostly due to the cost of the Neodymium-Boron magnets, the manufacturing of the magnetic rails, and the precision of the overall mechanics. In this paper, a much cheaper alternative is proposed-to use a low-cost linear switched reluctance motor (LSRM) and an adaptive control strategy to overcome the tolerances and difficult control characteristics inherent in the motor. The LSRM has simple and robust structure, and it does not contain any magnets. However, its force is solely drawn from the reluctance change between the coil and the steel plates. Variations on the behavior of these two elements due to different operating conditions will change the motion behavior of the motor. Also, to keep the overall cost low, the LSRM sets a marginal mechanical tolerance during its mass production. This leads to characteristic variations in the final product. Finally, since the LSRM is a direct drive motor, any variations on the motor characteristics will directly reflect on the control system and the motion output. In this paper, a self-tuning regulator (STR) is proposed to combat the difficulties and uncertain control behaviors of the LSRM. This paper first introduces the motor winding excitation scheme, the model of the LSRM, and the current control method. The LSRM system is modeled as a single-input single-output discrete model with its parameters estimated by the recursive least square (RLS) algorithm. Then, an STR based on the pole placement algorithm is applied to the LSRM for high- performance position tracking. Both the simulation investigation and the experimental verification were conducted. In both cases, the results verified that the proposed RLS algorithm can estimate the parameters with fast convergence. The STR can provide quick response and high precision which is robust to the change of system parameters. Combined with STR control, the LSRM is a low-cost solution to fast, accurate, and reliable position tracking for many demanding motion control applications.

High-Precision Position Control of a Linear-Switched Reluctance Motor Using a Self-Tuning Regulator

High-precision position control of linear-switched reluctance motor (LSRM) is important in motion-control industry. The static model-based controller sometimes cannot give satisfactory output performance due to the inherent nonlinearities of LSRM and the uncertainties of the system. In this paper, a self-tuning regulator (STR) based on the pole-placement algorithm is proposed for high-precision position tracking of the LSRM. Following the time-scale characteristics analysis of LSRM position-tracking system and force-characteristic investigation, the position-tracking model is treated as a second-order system. Different from the static model-based control schemes, the dynamic model of the LSRM can be obtained by online estimation. Also, some practical aspects are taken into account. Owing to the unmodeled dynamics and high-frequency measurement noises, there are some oscillations in the practical control signals, and they can be reduced by a properly designed filter. Both the simulation and experimental results demonstrate that, in the control of the proposed STR, the position-tracking system can reproduce the reference signal with the desired performance in harsh ambient. These results confirm that the method is effective and robust in the high-precision position tracking of LSRM.

A Novel Planar Switched Reluctance Motor for Industrial Applications

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 motors 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

Magnetic Analysis of Switched Reluctance Actuators in Levitated Linear Transporters

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.

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

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.

Position Estimation and Error Analysis in Linear Switched Reluctance Motors

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.

Passivity-based control of linear switched reluctance motors

Abstract In this paper, a non-linear controller for linear switched reluctance motors (LSRMs) is developed by utilizing their properties and the energy dissipation theory. As the electrical time constant is much smaller than the mechanical time constant, the whole LSRM driving system can be treated as a two-time-scale system. It is then decomposed into an electrical subsystem and a mechanical subsystem, which are interconnected by negative feedbacks. Controllers for these two subsystems are designed to guarantee that both systems are passive. Because a system consisting of two passive subsystems connected through negative feedbacks is still passive as a whole, stability of an LSRM driving system can be achieved at system level. The proposed control strategy is characterized by a simple structure and easy implementation. Experimental results are also provided to prove the effectiveness and robustness of the proposed position control for LSRM.

Trajectory Control of a Linear Switched Reluctance Motor using a Two-Degree-of-Freedom Controller

Linear switched reluctance motors (LSRMs) have been an attractive choice for direct-drive applications due to their low-cost and simple structures. However, LSRMs are difficult to control because of the highly nonlinear model. In this paper, a LSRM model, which takes the winding current tracking as a part of the LSRM model, is first proposed based on the two-time-scale method. According to this model, a basic yet effective two-degree-of-freedom controller is developed. The two-degree-of-freedom controller is as low cost as the conventional proportional-derivative (PD) controller but it has better the high frequency tracking capability than the conventional PD controller. Experimental results indicate that the LSRM model is effective for the controller design and the position tracking system with the proposed controller can track the position command accurately.

Disturbances Rejection for Precise Position Control of Linear Switched Reluctance Motors

In this paper, a passivity-based control (PBC) algorithm with disturbance estimation is proposed to obtain precise position control of a Linear Switched Reluctance Motor (LSRM) driving system. Following the modeling analysis of the driving system, a full-order controlled model is first developed. On the basis of the state error equation, the proposed robust PBC algorithm is derived from the view of energy dissipation and the global stability of the whole servo system is insured by the proposed algorithm in turn. Through the disturbance estimation, it can also reject the effect from external disturbances and make the servo system achieve precise position tracking. Simulations and experimental implementations carried out on the proposed LSRM driving system demonstrate that the proposed control algorithm is effective for the LSRM position tracking system.

On Control of Planar Switched Reluctance Motor

Abstract By using the energy dissipation theory and the property of the switched reluctance motor, this paper presents a nonlinear controller for the planar switched reluctance motors (PSRM). Based on the fact that the electrical time constant is much smaller than the mechanical time constant, the whole PSRM driving system is treated as a two-time-scale system and can be decomposed into two subsystems (electrical and mechanical) that are negative feedback interconnection. The controllers are designed for two subsystems respectively to ensure that they are passive. In view of the fact that the system made of two passive subsystem connected through negative feedback is still passive. Therefore, the stability of PSRM driving system is ensured in large scale. This control strategy possesses a simple structure and can be implemented easily. The experimental results show that the proposed control is effective for the position control of PSRM.