Electric Power Steering Neutral Position Correction
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Solution Overview
Problem
Existing electric power steering systems struggle to accurately determine the neutral position of a steering wheel, especially due to secular changes in the steering system and driver input, leading to potential errors in vehicle straight-line stability.
Innovation Solution
A control device and method that utilize a processor to determine the vehicle's straight-ahead traveling state based on vehicle speed, steering wheel torque, and angle, storing and calculating a weighted average of steering wheel angles to correct the neutral position, with increased weightage given to higher vehicle speeds for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the neutral position is determined based on simple wheel speed difference, then the detection method is simple, but the measurement precision is insufficient
Solution Approach 1:
The patent changes the detection parameters from simple wheel speed difference to a comprehensive set including vehicle speed, steering wheel torque, and steering wheel angle. By selecting and weighting multiple parameters, the system achieves higher measurement precision for neutral position detection while managing complexity through systematic parameter selection and weighting strategies.
2Measurement precision
If multiple steering wheel angles are stored and weighted average is calculated, then the measurement precision improves, but the loss of time increases
Solution Approach 1:
The patent applies partial action by storing multiple steering wheel angle data points and calculating a weighted average rather than using all possible data. The weighting scheme prioritizes recent data and data from straight-ahead traveling states, achieving improved precision without processing excessive historical data that would unnecessarily increase time loss.
Solution Approach 2:
The system performs preliminary classification of driving states (straight-ahead vs. non-straight-ahead) before calculating the weighted average. By pre-identifying relevant data points that meet the straight-ahead traveling conditions, the system reduces the computational burden during the averaging process, thereby reducing time loss while maintaining precision.
3Adaptability or versatility
If the neutral position is frequently updated, then the adaptability improves, but the stability of the composition deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring driving state conditions (vehicle speed, steering torque, steering angle) and only updating the neutral position when straight-ahead traveling conditions are met. This feedback mechanism allows the system to adapt to secular changes in the steering system while maintaining stability by rejecting updates during transient or non-representative driving conditions.
Solution Approach 2:
The system dynamically adjusts the neutral position based on real-time driving conditions rather than using a fixed update schedule. By making the update mechanism dynamic and condition-dependent, the system achieves adaptability to secular changes while maintaining stability through selective updating only when reliable data is available.
Data Source
AI summary
A control device includes a processor and a storage device storing a program for controlling an operation of the processor. The processor determines whether a vehicle is in a straight-ahead traveling state, based on a vehicle speed detected by a vehicle speed sensor, a steering wheel torque applied to a steering wheel, and a steering wheel angle as a rotation angle of an input shaft. The processor stores the steering wheel angle in the memory when determining that the vehicle is in the straight-ahead traveling state. The processor stores the steering wheel angle in the memory multiple times when determining that the vehicle is in the straight-ahead traveling state. The processor calculates a corrected steering angle amount from a weighted average of the steering wheel angles stored in the memory.