Electric Power Steering Angle Calculation via Motor Feedback
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Solution Overview
Problem
Conventional electric power steering systems face challenges in achieving high accuracy for automatic steering control due to low resolution of steering angle sensors, leading to oscillations and positional displacements.
Innovation Solution
An electric power steering apparatus that includes a rate limiter for smoothing the target steering angle, a current command value calculating section for calculating correction current commands based on actual steering angles and steering torque, and a damping control section for proportional and differential control, enabling accurate automatic steering control without additional parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional steering angle sensor is used for automatic steering control, then the system structure remains simple, but the steering angle resolution is low causing oscillations and positional displacements
Solution Approach 1:
The patent introduces a steering angle calculation unit that acts as an intermediary between the motor angle sensor and the automatic steering control. This unit calculates the steering angle by dividing the motor angle by the reduction ratio, providing high-resolution steering angle data without requiring an additional high-precision steering angle sensor. The calculation unit processes the motor angle information and outputs accurate steering angle values, resolving the contradiction between measurement precision and device complexity.
2Manufacturing precision
If feedback control of motor current is performed for accurate steering assist torque generation, then the steering assist accuracy is improved, but the system requires complex control mechanisms
Solution Approach 1:
The patent implements feedback control by continuously monitoring the motor current and adjusting the voltage supplied to the motor. The control unit compares the actual motor current with the commanded current and modifies the PWM duty cycle to minimize the difference. This feedback mechanism ensures accurate steering assist torque generation while maintaining a relatively simple control structure by using standard PWM control techniques.
3Measurement precision
If the actual steering angle is calculated using motor angle and reduction ratio, then high accuracy automatic steering control is achieved without additional parts, but the system must handle calculation and communication between ECUs
Solution Approach 1:
The patent enables the EPS control unit to self-calculate the steering angle using its own motor angle sensor data and the known reduction ratio. Instead of relying on external steering angle sensors or complex communication systems, the control unit performs the calculation internally using the formula: steering angle = motor angle / reduction ratio. This self-service approach achieves high accuracy automatic steering control without requiring additional sensing parts or complex communication infrastructure.
Data Source
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AI summary
[Problem] An object of the present invention is to provide an electric power steering apparatus that is capable of performing the automatic steering control without using any particular parts in a vehicle having functions of the automatic steering control and the manual steering control, and improves accuracy of the automatic steering by comprising a damping control function and correcting the target steering angle by the calculated actual steering angle. [Means for solving the problem] An electric power steering apparatus comprising: a steering angle control section that calculates a secondmotor current command value in an automatic steering control so as to bring a first actual steering angle close to a target steering angle; and a switching section that inputs the first and second motor current command values and is switched by a switching signal, wherein the steering angle control section comprises an actual steering angle calculating section that calculates a second actual steering angle on the basis of the first actual steering angle, a steering torque and a motor rotation angle and calculates the second motor current command value on the basis of the target steering angle and the second actual steering angle.