Mathematical Modelling and Simulation of a PWM Inverter Controlled Brushless Motor Drive System from Physical Principles for Electric Vehicle Propulsion Applications

Abstract

High performance electric motor drive systems are central to modern electric vehicle propulsion systems (Emadi et al. , 2003) and are also widely used in industrial automation (Dote, 1990) in such scenarios as numerical control (NC) machine tools and robotics. The benefits accruing from the application of such drives are precision control of torque, speed and position which promote superior electric vehicle dynamical performance (Miller, 2010) with reduced greenhouse carbon gaseous emissions resulting in increased overall automotive efficiencies. These electric motor drive attributes also contribute to enhanced productivity in the industrial sector with high quality manufactured products. These benefits arise from the fusion of modern adaptive control techniques (El Sarkawi, 1991) with advances in motor technology, such as permanent magnet brushless motors, and high speed solid-state switching converters which constitute the three essential ingredients of a high performance embedded drive system. The controllers of these machine drives are adaptively tuned to meet the essential requirements of system robustness and high tracking performance without overstressing the hardware components (Demerdash et al, 1980; Dawson et al, 1998). Conventional d.c. motors were traditionally used in adjustable speed drive (ASD) applications because torque and flux control were easily achieved by the respective adjustment of the armature and field currents in separately excited systems where fast response was a requirement with high performance at very low speeds (Vas, 1998). These dc motors suffer from the drawback of a mechanical commutator assembly fitted with brushes for electrical continuity of the rotor mounted armature coil which increases the shaft inertia and reduces speed of response. Furthermore they require periodic maintenance because of brush wear which limits motor life and the effectiveness of the commutator for high speed applications due to arcing and heating with high current carrying capacity (Murugesan, 1981). Brushless motor drive (BLMD) systems, which incorporate wide bandwidth speed and torque control loops, are extensively used in modern high performance EV and industrial motive power applications as control kernels instead of conventional dc motors. Typical high performance servodrive applications (Kuo, 1978; Electrocraft Corp, 1980) which require high torque and precision control, include chemical processing, CNC machines, supervised