Electric Power Steering Torque Control via SAT Compensation
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Solution Overview
Problem
Conventional electric power steering apparatuses fail to implement steering torque equivalent to steering angle and angular velocity without being affected by road surface conditions, and exhibit poor smoothness and stability in operation due to inadequate consideration of steering angle and angular velocity.
Innovation Solution
The electric power steering apparatus calculates a steering reaction compensation value based on steering angle, angular velocity, and self-aligning torque, and adjusts the current command value using this compensation, or controls the twist angle of a torsion bar to follow the steered angle, incorporating virtual spring and damper components and noise-filtered SAT values to achieve stable control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional feedback control adjusts motor voltage based on current command value and detected motor current, then motor current control is achieved, but steering torque cannot be made equivalent to steering angle and angular velocity without being affected by road surface conditions
Solution Approach 1:
The patent introduces feedback control of motor current by adjusting voltage supplied to the motor based on the difference between current command value and detected motor current value. Additionally, feedback sections with phase compensating sections and gain sections are used to feedback SAT (self-aligning torque) to the steering assist command value, enabling precise control of steering torque equivalent to steering angle and angular velocity while compensating for road surface condition variations.
Solution Approach 2:
The patent changes control parameters by introducing SAT compensation values and steering reaction compensation values calculated based on steering angle, steering angular velocity, and SAT. These parameter changes allow the system to maintain accurate steering torque control equivalent to steering angle and angular velocity while being insensitive to road surface conditions.
2Ease of operation
If conventional electric power steering apparatus performs basic feedback control, then motor assist torque is provided, but smoothness and stability of operation are poor
Solution Approach 1:
The patent implements multiple feedback mechanisms including feedback control of motor current, SAT feedback through phase compensating sections and gain sections, and steering reaction compensation feedback. These feedback loops significantly improve the smoothness and stability of operation by continuously adjusting control parameters based on actual system state and road surface conditions.
Solution Approach 2:
The patent calculates steering reaction compensation values in advance based on steering angle, steering angular velocity, and SAT compensation value before actual steering operations. This beforehand preparation of compensation values cushions against variations in road surface conditions, ensuring smooth and stable operation throughout the steering process.
3Measurement precision
If conventional apparatus does not consider steering angle and angular velocity in control, then control simplicity is maintained, but steering torque cannot follow target values accurately
Solution Approach 1:
The patent uses feedback sections with phase compensating sections and gain sections to feedback SAT to the steering assist command value. This feedback mechanism enables accurate followability to target steering torque by continuously adjusting control based on actual system state, while maintaining reasonable control complexity through systematic calculation approaches.
Solution Approach 2:
The patent performs preliminary calculations of SAT compensation values and steering reaction compensation values based on steering angle, steering angular velocity, and vehicle speed before actual torque control. This preliminary action prepares the necessary compensation parameters in advance, enabling accurate steering torque control without excessive real-time computational complexity.
Data Source
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AI summary
[Problem] An object of the present invention is to provide an electric power steering apparatus that enables implementation of a desired steering torque without being affected by a state of a road surface by controlling a steering torque so as to become a value corresponding a steering angle and a steering angular velocity. [Means for solving the problem] An electric power steering apparatus that assists and controls a steering system by driving a motor based on a current command value calculated based on a steering torque and a vehicle speed, comprises a SAT compensation value calculating section that calculates a SAT compensation value based on a SAT value; and a steering reaction compensation value calculating section that calculates a steering reaction compensation value based on the SAT compensation value, a steering angle and a steering angular velocity; and corrects the current command value by the steering reaction compensation value. Further, an electric power steering apparatus controls a twist angle of a torsion bar so as to follow a value corresponding to a steered angle.