Closed-loop torque control for electric power steering
First Claim
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1. A method for controlling an electric power steering system in a vehicle comprising the steps of:
- measuring steer angle and vehicle speed;
developing, in response to the measured steer angle and vehicle speed, a steering torque command representative of a target operator exerted steering torque;
comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and
controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque.
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Abstract
A control system for electric power steering develops a desired operator exerted steering torque command independent of operator exerted torque, compares that command to a measure of actual operator exerted steering torque and controls an electric motor providing electric power steering assist to minimize the difference between the desired operator exerted steering torque command and the actual operator exerted steering torque.
89 Citations
19 Claims
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1. A method for controlling an electric power steering system in a vehicle comprising the steps of:
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measuring steer angle and vehicle speed; developing, in response to the measured steer angle and vehicle speed, a steering torque command representative of a target operator exerted steering torque; comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for controlling an electric power steering system in a vehicle comprising:
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means for measuring steering wheel angle and vehicle speed; means for developing a steering wheel velocity signal as a time derivative of said measured steering wheel angle; means for developing, in response to the measured steering wheel angle and vehicle speed and in response to the steering wheel velocity signal, a steering torque command representative of a target operator exerted steering torque and for comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and means for controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator exerted steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (7)
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8. An apparatus for controlling an electric power steering system in a vehicle comprising:
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means for measuring steering pinion gear angle of a steering pinion gear mechanically coupled to a steering shaft and a steering rack; means for developing a pinion gear velocity signal as a time differentiation of said steering pinion gear angle; means for developing, in response to the measured steering pinion gear angle and vehicle speed and in response to the pinion gear velocity signal, a steering torque command representative of a target operator exerted steering torque and for comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and means for controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator exerted steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (9)
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10. A method for controlling an electric power steering system in a vehicle comprising the steps of:
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measuring steer angle and vehicle lateral acceleration; developing, in response to the measured steer angle and vehicle lateral acceleration, a steering torque command representative of a target operator exerted steering torque; comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the torque operator steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (11, 12, 13, 14)
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15. An apparatus for controlling an electric power steering system in a vehicle comprising:
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means for measuring steering wheel angle and vehicle lateral acceleration; means for developing a steering wheel velocity signal as a time differentiation of said measured steering wheel angle; means for developing, in response to the measured steering wheel angle and vehicle lateral acceleration and in response to the steering wheel velocity signal, a steering torque command representative of a target operator exerted steering torque and for comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and means for controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operated exerted steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (16)
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17. An apparatus for controlling an electric power steering system in a vehicle comprising:
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means for measuring steering pinion gear angle of a steering pinion gear mechanically coupled to a steering shaft and a steering rack; means for developing a pinion gear velocity signal as a time differentiation of said steering pinion gear angle; means for developing, in response to the measured steering pinion gear angle and vehicle lateral acceleration and in response to the pinion gear velocity signal, a steering torque command representative of a target operator exerted steering torque and for comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and means for controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator exerted steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque. - View Dependent Claims (18)
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19. A method for controlling an electric power steering system in a vehicle comprising the steps of:
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developing, independent of operator exerted steering torque, a steering torque command representative of a target operator exerted steering torque; comparing the steering torque command to a measure of actual operator exerted steering torque and developing a torque error signal in response to the comparison; and controlling an electric motor to apply torque assist to the vehicle steering system in response to the torque error signal, increasing said torque assist if the actual operator exerted steering torque is greater than the target operator steering torque and decreasing said torque assist if the actual operator exerted steering torque is less than the target operator steering torque thereby to minimize the torque error signal and bring the actual operator exerted steering torque into substantial agreement with the target operator exerted steering torque.
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Specification