Direct Torque Control Of Dual Induction Motor Drives Fed By Five-Leg Inverter For Electric Vehicles

Multi motor drives system is the current trend in electric vehicle application.Conventionally,each induction motor will have its own dedicated three-phase inverter.However,dual motor drives using dedicated three-phase inverter have its limitation,it is difficult to control,synchronise and not cost effective.This research aims to develop and implement a combined electric differential (ED) for torque distribution of electric vehicle steering action and independent speed control for dual induction motors drives fed by a single Five-Leg Inverter (FLI).It is desired for having fewer components and reduces size and cost for multi motor drives system. Recent research has shown that,dual motors drives can be independently controlled by using FLI.Direct torque control (DTC) scheme for induction motor with space vector pulse width modulation (SVPWM) technique is used for the drive in this research.Flux and torque responses are estimated by DTC estimator.Additionally,the special 6 to 5 duty cycle SVPWM is used to trigger the FLI in order to control the torque and speed of the dual induction motors.These motors are directly coupled to the wheels of the electric vehicle test rig in the laboratory.The ED is used to distribute the torque for both of the wheels.The employment of ED method allows the investigation of the effects of steering angle input variation and different speed command towards detail study of electric motor drives performance in an electric vehicle application. Upon the completion of the research based on simulation and experimental works it is proves that the proposed technique has produced good expected result of the combined ED and independent speed control for dual induction motors drives fed by a single FLI.The system has been tested with steering angle variation from 20°, 45°,80° and 100° to compare the performance of dual motor controller for right tum manoeuvre and left turn manoeuvre for low speed operation fix at 200 rpm.It is show that the speed difference between M I and M2 increase with the increasing of steering angle as well as the cornering distance and angle also increase respectively.It is confirmed that there is a correlation between the linear velocities of the car (kmph) is decreasing with the increasing of steering angle for both right tum and left manoeuvre

Improved direct torque control load torque estimator with the influence of steering angle for dual induction motors electric vehicle traction drive system

Front-wheel direct-driven dual motors of an electric vehicle (EV) with a single controller configuration offer great potential and flexibility for improving system performance, efficiency and safety. The objective of the paper is to design a new load torque estimator of Direct Torque Control (DTC) by merging the electrical model with the mechanical model of an EV traction system to improve the dual motors single controller configuration. The electrical model utilise Space Vector PWM (SVPWM) DTC control of dual induction motors fed Five-leg Inverter (FLI) while the mechanical model takes the 14DOF vehicle dynamic model as its main structure. The new technique used is by integrating lateral force with longitudinal force produced at the touch point of a tyre with road surface as the input to the new load torque estimator of DTC. The new load torque estimator technique results were, then, compared with the standard load torque estimator that used the voltage and current feedback only. The findings showed that while torque estimator of conventional DTC had no effect of steering angle on the speed, torque and current performance of the motors, the new load torque estimator showed a significant impact. The speed, torque and current responds of the motors now have precisely been estimated; following the trajectory of the steering angle. Hence, for future research the new load torque estimator with the accurate and precise speed and torque response can further be utilized in stability, slip and skid and traction control or even for electronic braking system