Method and apparatus for thermal management of an electric power assist steering control system by compensating steering motor current
First Claim
1. A vehicle steering system including an electric motor actuator, a motor driver circuit for generating and applying a motor current to the electric motor actuator, a current sensor for measuring the motor current from the motor driver circuit and generating a feedback signal, a torque sensor for sensing an applied steering torque and providing a torque command signal having a value indicative of the applied steering torque, said steering system comprising:
- a controller for calculating a temperature of the electric motor actuator by evaluating the motor current applied to the electric motor actuator and an amount of thermal energy released by the electric motor actuator, and generating a temperature signal and having a temperature reduction factor which correlates to the temperature signal for reducing the motor current and the controller for providing a control signal to the motor driver circuit based on the feedback current signal and the torque command signal wherein the motor current is reduced by the temperature reduction factor when the temperature of the electric motor actuator is determined by the controller to be greater than a predetermined temperature limit; and
wherein the controller is programmed with an electric motor actuator temperature model for determining the temperature of the electric motor actuator.
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Accused Products
Abstract
An electric power assist steering control system having an electric motor actuator and a motor driver circuit for generating and applying a motor current to the electric motor actuator. A current sensor is included for measuring the motor current from the motor driver circuit and generating a feedback signal. A torque sensor is included for sensing an applied steering torque and providing a torque command signal having a value indicative of the applied steering torque. A controller calculates a temperature of the electric temperature of the electric motor actuator by evaluating the motor current applied to the electric motor actuator. In the case that the calculated temperature of the electric motor actuator surpasses a predetermined temperature, the electric power assist steering control system reduces the amount of motor current applied to the electric motor actuator thereby reducing the temperature of the electric motor actuator.
45 Citations
17 Claims
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1. A vehicle steering system including an electric motor actuator, a motor driver circuit for generating and applying a motor current to the electric motor actuator, a current sensor for measuring the motor current from the motor driver circuit and generating a feedback signal, a torque sensor for sensing an applied steering torque and providing a torque command signal having a value indicative of the applied steering torque, said steering system comprising:
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a controller for calculating a temperature of the electric motor actuator by evaluating the motor current applied to the electric motor actuator and an amount of thermal energy released by the electric motor actuator, and generating a temperature signal and having a temperature reduction factor which correlates to the temperature signal for reducing the motor current and the controller for providing a control signal to the motor driver circuit based on the feedback current signal and the torque command signal wherein the motor current is reduced by the temperature reduction factor when the temperature of the electric motor actuator is determined by the controller to be greater than a predetermined temperature limit; and
wherein the controller is programmed with an electric motor actuator temperature model for determining the temperature of the electric motor actuator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for compensation of a motor current in a vehicle steering control system including an electric motor actuator, a motor driver circuit for generating and applying the motor current to the electric motor actuator, said method comprising the steps of:
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determining the motor current applied to the electric motor actuator;
calculating a temperature of the electric motor actuator based on at least one electric motor actuator variable and an amount of thermal energy released by the electric motor actuator using a controller programmed with an electric motor actuator temperature model for determining the temperature of the electric motor actuator;
reducing the motor current applied to the electric motor actuator based on the calculated temperature of the electric motor actuator until the calculated temperature of the electric motor actuator falls within a predetermined temperature range; and
wherein the motor current applied to the electric motor actuator is reduced by a temperature reduction factor. - View Dependent Claims (10, 11, 12, 13, 14, 16)
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15. The method according to clam 9, wherein the amount of energy released is calculated based on a surface area of the electric motor actuator.
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17. A method for compensation of a motor current in a vehicle steering control system including an electric motor actuator, a motor driver circuit for generating and applying the motor current to the e ectric motor actuator, said method comprising the steps of:
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determining the motor current applied to the electric motor actuator;
calculating a determined temperature of the electric motor actuator based on at least one electric motor actuator variable and an amount of thermal energy released by the electric motor actuator using a controller programmed with an electric motor actuator temperature model for determining the temperature of the electric motor actuator; and
reducing the motor current applied to the electric motor actuator by a temperature reduction factor which is based on the determined temperature of the electric motor actuator until the determined temperature of the electric motor actuator falls within a predetermined temperature range.
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Specification