Motivated by technological advances in power electronics and signal processing, and by the interest in using direct drives for robot manipulators, we investigate the control problem of high-performance drives for switched reluctance motors (SRM's). SRM's are quite simple, low cost, and reliable motors as compared to the widely used dc motors. However, the SRM presents a coupled nonlinear multivariable control structure which calls for complex nonlinear control design in order to achieve high dynamic performances. We first develop a detailed nonlinear model which matches experimental data and establish an electronic commutation strategy. Then, on the basis of recent nonlinear control techniques, we design a state feedback control algorithm which compensates for all the nonlinearities and decouples the effect of stator phase currents in the torque production. The position dependent logic of the electronic commutator assigns control authority to one phase, which controls the motion, while the remaining phase currents are forced to decay to zero. Simulations for a direct drive, single link manipulator with the SRM are reported, which show the control performance of the algorithm we propose in nominal conditions and test its robustness versus the most critical parameter uncertainties of payload mass and stator resistance.

Feedback linearizing control of switched reluctance motors

A new type of doubly salient machine is presented in which the field excitation is provided by a nonrotating permanent magnet (PM). This doubly salient PM (DSPM) motor is shown to be kindred to square waveform PM brushless DC motors. Linear and nonlinear analysis has been performed to investigate the characteristics of this new type of PM motors. A prototype DSPM motor has been designed, and a comparison has been made between this new type of motor and the induction motor. It is shown that, by fully exploiting modern high-energy PM material and the doubly salient structure, the DSPM motor can offer superior performance over existing motors in terms of efficiency, torque density, torque-to-current ratio, and torque-to-inertia ratio, while retaining a simple structure amenable to automatic manufacture. >

A novel permanent magnet motor with doubly salient structure

In this article we review the recent advances in iterative learning control (ILC) for nonlinear dynamic systems. In the research field of ILC, two categories of system nonlinearities are considered, namely, the global Lipschitz continuous (GLC) functions and local Lipschitz continuous (LLC) functions. ILC for GLC systems is widely studied and analysed using contraction mapping approach, and the focus of recent exploration moves to application problems, though a number of theoretical issues remain open. ILC for LLC systems is currently a hot area and the recent research focuses on ILC design and analysis by means of Lyapunov approach. The objectives of this article are to introduce recent development and advances in nonlinear ILC schemes, highlight their effectiveness and limitations, as well as discuss the directions for further exploration of nonlinear ILC.

A survey on iterative learning control for nonlinear systems

Although design of the variable reluctance (switched reluctance( type of synchronous machine has experienced intense activity in recent years, relatively little effort has been expended on improving the torque capability of the synchronous reluctance type of motor drive. Based on the analysis presented in this paper, it appears that substantial improvements can be made in the design of such motor drives resulting in performance characteristics which match or, indeed, perhaps even exceed that of the induction machine.

Synchronous reluctance machines―a viable alternative for AC drives?

This paper proposes a general field modulation theory for electrical machines by introducing magnetomotive force modulation operator to characterize the influence of short-circuited coil, variable reluctance, and flux guide on the primitive magnetizing magnetomotive force distribution established by field winding function multiplied by field current along the airgap peripheral. Magnetically anisotropic stator and rotor behave like modulators to produce a spectrum of field harmonics and the armature winding plays the role of a spatial filter to extract effective field harmonics to contribute the corresponding flux linkage and induce the electromotive force. The developed field modulation theory not only unifies the principle analysis of a large variety of electrical machines, including conventional dc machine, induction machine, and synchronous machine which are just special cases of the general field modulated machines, thus eliminating the problem of the machine theory fragmentation, but also provides a powerful guidance for inventing new machine topologies.

General Airgap Field Modulation Theory for Electrical Machines

The paper explores the theory and potential of a family of doubly salient electronically-switched reluctance motors. It is demonstrated that the machine provides the basis for fully-controllable variable-speed systems, which are shown to be superior to conventional systems in many respects. The motor retains all the advantages normally associated with induction motors and brings significant economy in the drive electronics. The basic modes of operation, analysis, design considerations and experimental results from a range of prototype motors up to 15 kW at 750 rev/min are described. The most recent prototype has achieved a continuous rating which is 1.4 times that of the equivalent induction motor.

J. Corda

Papers

Variable-speed switched reluctance motors