Controller for electric vehicle

Abstract

A power system of an electric vehicle is composed of a three-phase induction motor, an inverter for supplying alternating current converted from direct current of a battery mounted on the vehicle and a controller including a microcomputer for controlling the power supply to the motor. The controller calculates a torque required to drive the motor according to driving conditions of the vehicle. When a signal to stop the motor is generated, the power supply from the inverter to the motor is not immediately turned off but gradually decreased according to a predetermined torque decrease ratio if the motor is driven at that time with a torque higher than a predetermined level, to avoid uncomfortable vibrations of the motor associated with the abrupt turning off of the power supply thereto. The power supply to the motor is finally turned off when the torque of the motor is decreased to the level below the predetermined value. Thus, the uncomfortable vibration of the motor otherwise associated with the turning off of the power supply is avoided. Since the torque level permitting the turning off of the power supply and the torque decrease ratio are preset at optimum values based on vibration characteristics of the motor including its mounting, the motor is turned off within a reasonably short period of time after the signal to stop the motor is generated.

Dependencies are inferred from the claim text.