Controls of BLDC motors in electric vehicle Testing Simulator

Brushless direct current (BLDC) motor is one of the popular motors in the industry and automotive. In automotive, this motor is often used in an electric vehicle (EV) due to its high efficiency. As part of the EV testing phase, EV Testing Simulator is built here by employing two BLDC motors that are mechanically coupled through their axis. One motor simulates an electric motor that drives the EV and the other simulates the mechanical loads on the driving motor such as frictional, drag, and gravitational forces in the downhill and uphill conditions. A control module of BLDC motor is devised and consists of two sub-modules, namely test-motor control sub-module and load-motor control sub-module. The first sub-module controls the speed of the test-motor (i.e. the driving motor of the EV)to simulate a prescribed EV driving cycle. Meanwhile, the second sub-module controls the torque or current of the load motor to simulate the loading effects on the test-motor. Both sub-modules have BLDC drivers with fixed Direct Torque Control (DTC) and closed loop schemes are therefore required especially for speed control of test-motor control sub-module. When simulating uphill road in which load-motor acts as a generator,load-motor sub-module performs closed loop torque control with a feedback obtained from a simple steady-state estimation of electric torque of the load-motor. Experiment results show that the test-motor sub-module produces relatively small speed oscillation around the reference value with a maximum speed of 1800 RPM.The load-motor sub-module can simulate load disturbance which generates 10-18 A load current for uphill mode and about 9A for downhill mode.