Steering Angle Detection Using Nonlinear Learning Maps
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Solution Overview
Problem
Conventional electric power steering systems face challenges in accurately estimating motor shaft and steering shaft angles due to nonlinear elements in the reduction mechanism, leading to difficulties in diagnosing and backing up angle sensors, which affects reliability and increases costs.
Innovation Solution
A vehicle steering angle detecting apparatus with dual-system angle sensors that learn and estimate motor shaft and steering shaft angles by dividing nonlinear elements into static, dynamic, and delay characteristics, allowing for accurate backup and abnormality judgment, even when one sensor fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-system angle sensors are equipped with steering shaft and motor shaft, then reliability and redundancy are improved, but device complexity and cost increase
Solution Approach 1:
The system uses feedback control by comparing the steering shaft angle detected by the first angle sensor with the motor shaft angle detected by the second angle sensor, and adjusts the motor current based on the angle difference to maintain accurate steering assistance even when one sensor fails
Solution Approach 2:
The control unit acts as an intermediary that processes data from both angle sensors, calculates the angle difference, and determines sensor abnormality, enabling the system to utilize information from both sensors to maintain reliability without simply duplicating the entire sensor system
2Measurement precision
If nonlinear elements of reduction mechanism are learned and compensated, then measurement precision of angle estimation is improved, but device complexity and processing time increase
Solution Approach 1:
The system pre-acquires steering shaft angle and motor shaft angle data during normal operation, and performs learning processing to create compensation value maps for nonlinear elements before they are needed, so that accurate angle estimation can be achieved without complex real-time calculations
Solution Approach 2:
The learning processing is performed dynamically based on actual operating conditions, with the system adaptively updating compensation values for static characteristics, dynamic characteristics, and delay characteristics according to the specific steering工况, rather than using fixed complex models
3Manufacturing precision
If learning processing is performed for static, dynamic, and delay characteristics, then manufacturing precision of angle compensation is improved, but loss of time for learning increases
Solution Approach 1:
The learning processing is performed periodically under specific steering conditions (such as when the vehicle is stationary or during normal steering operation), dividing the learning process into manageable segments for static characteristics, dynamic characteristics, and delay characteristics rather than requiring continuous extensive learning
Solution Approach 2:
The system performs learning processing selectively based on whether the current operating conditions meet the predetermined criteria, and only learns the necessary characteristics (static, dynamic, or delay) based on the specific situation, rather than always performing complete learning for all three characteristics
Data Source
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AI summary
[Problem] An object of the present invention is to provide a vehicle steering angle detecting apparatus and an electric power steering apparatus equipped therewith having reasonable price that estimate a motor shaft angle and a steering shaft angle with a high accuracy by learning nonlinear elements, and can back up both angle sensors by utilizing estimating angles of the both angle sensors. [Means for solving the problem] The present invention is the vehicle steering angle detecting apparatus that connects a motor, which assist-controls a steering system of a vehicle, to the steering shaft via a reduction mechanism, and comprises the first angle sensor which detects the steering shaft angle of the steering shaft and the second angle sensor which detects the motor shaft angle of the motor, comprising: a function that updates a static characteristic map and a dynamic characteristic map by iteratively learning a static characteristic and a dynamic characteristic of the nonlinear elements including the reduction mechanism, and mutually estimates the steering shaft angle and the motor shaft angle by using the static characteristic map and the dynamic characteristic map. The present invention is also the electric power steering apparatus equipped with the vehicle steering angle detecting apparatus.