Torque oscillation compensation using torque transducer feedback

Abstract

A torque oscillation compensation system and circuit that uses torque transducer feedback derived from an output shaft of an electric vehicle motor to compensate for electrical motor pulsations such as are experienced in an electric vehicle. A torque input source provides a torque input signal, that is coupled to a summing circuit. A controller is coupled to the summing circuit, and power switching circuitry is coupled between the controller and the electric motor. A torque transducer is coupled to the output shaft of the motor to sense torque pulsations. An oscillation compensation circuit is coupled between the torque transducer and the summing circuit that generates a feedback compensation signal that is combined with the torque input signal to compensate for output shaft oscillators. The oscillation compensation circuit comprises a loop amplifier having a predetermined transfer function and is coupled to the torque transducer, and AC coupling circuitry, typically comprising a plurality of coupling capacitors, coupled between the loop amplifier and the summing circuit. A limiter circuit comprising first and second oppositely coupled diodes may be coupled to a point between the AC coupling capacitors. The oscillation compensation circuit may include a cascade amplifier coupled to the AC coupling circuitry. Compensation for the torque pulsations is provided by utilizing the AC component of a signal derived from the torque transducer that is coupled to the drive shaft of the electric motor as a feedback signal from which compensation commands are derived. This AC-coupled signal is fed back with proper amplitude and phase shift to modulate and compensate the motor current and/or slip and/or speed and/or commutating angle and/or field current to eliminate torque fluctuations of the drive train of the vehicle. The present invention eliminates these unwanted torque pulsations over all modes of propulsion operation.