Torque oscillation compensation using torque emulator/observer feedback

• US 5,442,268 A
• Filed: 05/13/1993
• Issued: 08/15/1995
• Est. Priority Date: 05/13/1993
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Wedeen, Robert S., Goodarzi, Gholam D.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Masih, Karen
• Application Number:
  US08/061,658
• Time in Patent Office: 824 Days
• Field of Search: 318/432, 318/610, 318/434, 318/433, 318/798
• US Class Current: 318/432
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A torque oscillation compensation system and torque estimator that uses torque emulator/observer feedback derived from an electric vehicle motor drive train. The present torque oscillation compensation system is adapted for use with an electric vehicle comprising a source of torque command signals and an electric motor that is controlled by a power switching circuit. The power switching circuit is responsive to the torque command signals and provides pulse width modulated signals for driving the motor. The system comprises a torque estimator that is coupled to received pulse width modulated signals provided by the power switching circuit, and motor currents and speed, for providing estimated torque feedback signals derived therefrom. A summing device coupled to the source of of torque commands, the torque estimator, and to the power switching circuit, for combining the torque command signals with the estimated torque feedback signals to provide compensated input signals to the power switching circuit that control the motor torque and speed. The present invention provides a calculated estimate of motor power and torque in an electric drive train system. The power and torque are calculated by utilizing pulse width modulated signals of a motor controller and scaling the result according to the value of the battery voltage/power supply. This provides accurate operation over the entire battery voltage range without requiring voltage measurement at the motor terminals. The present technique provides for smooth vehicle handling over a broad range of speeds for every mode of propulsion operation. Single phase and three phase embodiments of the invention are disclosed.

Claims

1. A torque oscillation compensation system for use with an electric vehicle comprising a source of torque command signals and an electric motor that is controlled by a power switching circuit that is responsive to the torque command signals and which provides pulse width modulated signals for driving the motor, said system comprising:

a torque estimator coupled to receive pulse width modulated signals provided by the power switching circuit for providing estimated torque feedback signals derived therefrom, wherein said torque estimator comprises;

(i) processing and scaling means coupled to receive the pulse width modulated signals and a battery signal, for scaling the pulse width modulated signals in proportion to the battery signal to produce output signals that comprise a measure of the phase voltages applied to the motor,

(ii) multiplying and summing means responsive to a measured current signal from the motor and to a signal indicative of the equivalent resistance of the motor for producing an output signal corresponding to a first transfer function,

(iii) multiplying means coupled to the multiplying and summing means for multiplying the output signals therefrom to produce an output power signal indicative of the output power P(t) of the motor, and

(iv) dividing means coupled to the multiplying means for dividing the output power signal by the speed of the electric vehicle to produce an output torque signal T(t) that is coupled to the summing device as the estimated torque feedback signal from the estimator circuit; and

a summing device coupled to the source of torque command signals, the torque estimator, and to the power switching circuit, for combining the torque command signals with the estimated torque feedback signals to provide compensated input signals to the power switching circuit that controls the motor.

2. A torque oscillation compensation system for use with an electric vehicle comprising a source of torque command signals and an electric motor that is controlled by a power switching circuit that is responsive to the torque command signals and which provides pulse width modulated signals for driving the motor, said system comprising:

a torque estimator coupled to receive pulse width modulated signals provided by the power switching circuit for providing estimated torque feedback signals derived therefrom, wherein the torque estimator comprises;

(i) processing and scaling means coupled to receive the pulse width modulated signals and a battery signal, for scaling the pulse width modulated signals in proportion to the battery signal to produce output signals that comprise predetermined line to line voltage signals applied to the motor,

(ii) multiplying and summing means responsive to the line to line voltage signals and to a signal indicative of the equivalent resistance of the motor and to measured phase currents, for producing an output signal corresponding to first transfer function representative of instantaneous power,

(iii) multiplying means coupled to the multiplying and summing means for multiplying the output signals therefrom to produce an output power signal indicative of a second transfer funciton representative of power,

(iv) summing means coupled to the multiplying and summing means for summing the output signals therefrom to produce an output power signal indicative of the output power P(t) of the motor, and

(v) dividing means coupled to the multiplying means for dividing the outut power signal by the speed of the electric vehicle to produce an output torque signal T(t) that is coupled to the summing device as the estimated torque feedback signal from the estimator circuit; and

a summing device coupled to the source of torque command signals, the torque estimator, and to the power switching circuit, for combining the torque command signals with the estimated torque feedback signals to provide compensated input signals to the power switching circuit that controls the motor.