Norbert C. Cheung

Multi-Objective Optimization Design of In-Wheel Switched Reluctance Motors in Electric Vehicles

The method of the optimization design with multi-objectives for switched reluctance motors (SRMs) in electric vehicles (EVs) is proposed in this paper. It is desired that electric motors for EVs have high torque, high efficiency, and high torque density. Thus, the developed optimization function is selected as the correct compromise between the maximum average torque, maximum average torque per copper loss, and maximum average torque per motor lamination volume, by using three weight factors and three base values. The stator and rotor pole arc angles are selected as the optimized variables. Furthermore, the authors also discuss the design requirements and some constraints on the optimization design. The results of the optimization design show that the proposed method meets the requirements of EVs on electric motors well. A prototype of the optimally designed in-wheel SRM for EVs has been manufactured. This paper provides a valuable method to implement the optimal design of SRMs for EVs.

Position control of linear switched reluctance motors for high-precision applications

Most advanced manufacturing processes require precise motions for material transfer, packaging, assembly, and electrical wiring. To achieve precise linear motions, most of these high-performance manufacturing machines use X-Y sliding tables with permanent-magnet rotary motors and rotary to linear couplers. Though this method is the most widely used, it has disadvantages of low accuracy, complex mechanical adjustments, high cost, and low reliability. This paper describes the position control of a linear switched reluctance motor for high-performance motions in manufacturing automation. The proposed actuator has a very simple structure and it can be manufactured easily. There is no need for magnets and no limitation on the travel distance. The actuator is extremely robust and can be used in a hostile environment. A novel current-force-position lookup table is first developed to perform the force linearization. Then, a plug-in robust compensator using H/sub /spl infin// loop-shaping design is employed to improve the system robustness and the tracking performance. Experimental results of the motion system indicate that the system has fast tracking responses with good accuracy.

High-precision position control of a novel planar switched reluctance motor

This paper presents the position control of a novel two-dimensional (2-D) switched reluctance (SR) planar motor. The planar motor consists of a six-coil moving platform and a flat stator base made from laminated mild steel blocks. Unlike conventional x-y tables, which stack two moving slides on top of each other, the proposed 2-D planar motor has the advantages of simple mechanical construction, high reliability, and the ability to withstand harsh operating conditions. Together with the two linear encoders attached to the x-axis and y-axis, the motor can be controlled under closed-loop mode. To combat the problem of force nonlinearity, this paper proposes a cascade controller with force linearization technique to implement the drive controller. Due to the unique structure of the planar motors magnetic circuit, there is very little coupling between the x-axis and y-axis, and no decoupling compensation is needed. Preliminary results show that the proposed SR planar motor has a positional accuracy of 5 /spl mu/m and a maximum acceleration/deceleration rate of 2 G.

Position estimation in solenoid actuators

This paper describes a novel method of estimating the position of a plunger inside a solenoid. The solenoid is a single phase variable reluctance actuator, with a highly nonlinear magnetic circuit. For the proposed method, position is estimated indirectly through the solenoids incremental inductance in the high current region. It exploits the advantage that motional e.m.f. is negligible under normal operating conditions. The incremental inductance is obtained from the rate of current rise of the PWM waveform, which in turn, is measured by a dedicated current rise measurement circuit. Position is estimated from a two dimensional look up table of incremental inductance and current. The method is simulated and then implemented on a typical industrial solenoid valve. Factors which affect the accuracy of the estimation and methods of overcoming them are also described in the paper.

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.

Novel Modeling and Damping Technique for Hybrid Stepper Motor

It is well known that commercial hybrid stepper system has one or more low-speed resonant points. However, this characteristic cannot be accurately modeled without high-order equations or complicated measurement of motor parameters. In this paper, a novel approach is proposed to model the behavior of a commercial 1.8deg hybrid stepper motor accurately and efficiently. Also, model-based damping algorithms for both open-loop control and servo control are proposed. Simulation and experimental results show that the proposed algorithms can effectively eliminate low-speed resonance and vibration of the stepper system. The algorithms are efficient enough to be implemented on commercial DSP-based controllers without sacrificing motion control performance.

Development and control of a low-cost linear variable-reluctance motor for precision manufacturing automation

Most advanced manufacturing processes require precise linear-position control for material transfer, packaging, assembly, and electrical wiring. To achieve precise linear motion, most of these high-performance manufacturing machines use X-Y sliding tables with permanent-magnet rotary motors and rotary-to-linear couplers. Though this method is the most widely used, it has disadvantages of low accuracy, complex mechanical adjustments, high cost, and low reliability. This paper describes the use of the variable-reluctance-driving principle to construct a novel linear direct-drive actuator system for high-performance position control in manufacturing automation. The proposed actuator has a very simple structure and it can be manufactured easily. There is no need for magnets and no limitation on the traveling distance. The actuator is extremely robust and can be used in hostile environment. A novel control method, using cascade control and the force-linearization technique, is developed and implemented for precision position control of the actuator. Experimental results of the motion system indicate that the system has fast responses with good accuracy.

Proportional control of a solenoid actuator

Solenoids are nonlinear actuating devices normally used in a switching mode. This paper proposes a dual rate cascade control for converting a switching solenoid into a proportional actuator. A fast inner loop current controller and a slower PID outer loop trajectory controller are employed, A simple static nonlinear map is used to partially linearise the system. This method results in a proportional actuator which is effective and practical.<<ETX>>

Design of a linear switched reluctance motor for high precision applications

This paper describes the design of a linear switched reluctance motor (LSRM) for high-speed high-precision point-to-point motions. An S-shaped curve is first chosen as the trajectory motion profile and then a simple yet effective design procedure is introduced to design the motors mechanical dimensions. Theoretical deduction and experimental results on the phase inductance and the static force generation are presented and compared with each other. The final design has a simple and robust structure. Measurements from the fabricated LSRM show that the motor has met all design specifications. The resultant LSRM is very useful in high-precision applications, especially in semiconductor fabrication machineries.

Disturbance and Response Time Improvement of Submicrometer Precision Linear Motion System by Using Modified Disturbance Compensator and Internal Model Reference Control

Permanent magnet linear motors are a type of linear motors that are generally used in precision motion control applications. However, the position of motor is easily disturbed by external force, disturbance, and variation in parameters of plant. Therefore, the construction of the high-precision linear motion system is a difficult task. This paper implements a modified disturbance observer and compensator, which includes a novel variable gain, to overcome the effects of unknown parameters of the motor, to minimize the effect of the disturbance, and to reduce the response time of the disturbance. This compensated linear motor is further controlled by the internal model reference control algorithm so that the position of the motor can be tracked with expected response precisely. The authors conducted the experiments and verified the feasibility of the high-precision positioning control. Compared with the case of normal disturbance compensator, the experimental results also illustrate the improvements of the novel variable gain, which reduces the response time toward the command signal and the external disturbance.