Instantaneous torque control of electric motor drives

Abstract

In the control of adjustable speed drives, the performance of inexpensive digital integrated circuits is approaching the stage where traditional control algorithms may be displaced by newer algorithms that better exploit their speed and the functional capabilities of their software. This paper introduces the concept of "instantaneous torque control" as an objective worth pursuing in the application of such digital IC's to drive systems. Instantaneous torque control would in principle permit the fastest possible response and the elimination of torque ripple, along with many other advantages not possible with conventional control algorithms, most of which are set up to control a time-averaged torque. This paper develops some of the fundamental principles of instantaneous torque control for the switched reluctance motor, which is used as an example because, like the brushless dc permanent-magnet motor with concentrated windings, it has the potential for rapid response but it can have appreciable torque ripple with unfavorable firing angles.Neither of these machines satisfies the conditions for the existence of a reference-frame transformation that will eliminate the rotor position from the voltage and torque equations, and this opens up a number of interesting questions as to the generality of instantaneous torque control algorithms, and whether they can be incorporated into the general or unified theory of electrical machines.

Optimization and Evaluation of Torque-Sharing Functions for Torque Ripple Minimization in Switched Reluctance Motor Drives

“…T ORQUE-SHARING function (TSF) is an effective approach to implement the control of torque ripple minimization (TRM) in switched reluctance motor (SRM) drives [1]- [7]. In order to realize minimum torque ripples, it is shown that the proposed TSFs can be employed to distribute, intelligently, the reference torque among all the phases of the motor, while ensuring that the sum of all the individual phase torques is equal to the expected torque.…”

“…The former means that the torque produced by a phase winding changes with the rotor position linearly, whereas the latter means that the torque produced by a phase winding changes nonlinearly with the rotor position. An early effort to develop exponential TSF for minimizing torque ripple was made by Illic-Spong et al [1], and those functions are referred as m-functions. Schramm et al [2] present a scheme of the linear TSF in which the torque changes linearly during phase commutation and the currents in two adjacent phases are the same at the central commutation point.…”

“…The organization of this paper is described as follows. First, the authors will develop improved exponential and sinusoidal TSFs based on [1] and [3], and describe linear and cubic TSFs in Section II. The two criteria to evaluate TSFs will be proposed in Section III.…”

Nonlinear Speed Control of Switched Reluctance Motor Drives Taking into Account Mutual Inductance

“…Optimal current profiling [4] and torque distribution functions [5][6][7][8][9] were proposed in the literature to minimize torque ripples during commutation. In [5,6], the basic idea was to distribute the desired torque to two adjacent phases during commutation using proposed torque distribution functions. Linearly decreasing the outgoing phase and increasing the incoming phase during the commutation interval was proposed in [7] to obtain a high performance torque controller.…”

Compensation of Permanent Magnet Motors Torque Ripple by Means of Current Supply Waveshapes Control Determined by Finite Element Method

“…Indeed, several works have shown that it is theoretically possible to reduce torque ripple by controlling the current input motors [2] [3]. However, these works only concem the elimination of electromagnetic torque ripple and disregard the cogging torque ripple.…”