| Switched reluctance motors (SRMs) have recently received a great deal of attention due to their simple construction. Their light weight, high power density and high speed capability make them ideal for a wide range of applications. SRM is made of concentric coil windings on the stator poles and steel laminates on the rotor. The torque is produced by injecting current into the stator windings to produce a reluctance force, which works to align the rotor and the stator poles. Thus far, industrial applications of the motor have been few due to the need for a complex controller to deal with the highly nonlinear plant (motor) characteristics. Controller stability is an issue, since the machine parameters are inherently nonlinear during normal operation.; Traditional methods of SRM control rely on detailed finite element analysis and test characterization to generate detailed lookup tables for machine control. These tables define phase conduction angle and current magnitude as a function of motor speed, load, rotor position and bus voltage. Although this method results in acceptable drive performance, its implementation is computationally intensive, complex and costly in both hardware and software. In addition, the controller response is sensitive to multiple parameter variation and is, therefore, not practical in mass production.; The focus of this thesis is to develop a simple controller for the SRM based on the digital control concept. The concept of digital control is that the dynamics of a nonlinear system can be controlled by applying a high-frequency switching control, equivalent to a high and a low state. The proposed approach considers both the reference current and the conduction angle as a part of the controller. Stability is proved by applying variable structure control theory. Experimental results supporting simulation results are also presented. The resulting controller exhibits (1) stable control even in the face of plant parameter variation, (2) fast dynamic response under a load, (3) efficient high speed operation, and (4) simple implementation. |
