Steering Angle Detection Using Stored Absolute Values
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Solution Overview
Problem
Existing electric power steering systems require multiple resolvers for accurate steering angle detection, leading to complex structures and increased costs, and suffer from inaccurate control when the ignition is turned off and the steering wheel is turned while the system is in an off state.
Innovation Solution
A steering angle detecting apparatus that uses a relative steering angle detecting unit to continuously detect the steering angle during startup and shutdown, storing the value in non-volatile memory and correcting it upon startup to calculate a provisional absolute steering angle, allowing for accurate detection without multiple sensors and preventing incorrect control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple resolvers are used to detect steering angle, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The invention stores the absolute steering angle value in memory immediately before system shutdown occurs. This preliminary action ensures that when the system restarts, the stored value can be corrected using detected relative steering angles to quickly establish an accurate absolute steering angle without requiring multiple resolvers, thereby resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The invention introduces a microcontroller that acts as an intermediary to calculate the absolute steering angle by combining the stored absolute value with detected relative steering angles. This intermediary processing unit enables accurate steering angle detection without requiring multiple complex sensor components, thus reducing device complexity while maintaining measurement precision
2Productivity
If absolute steering angle is stored in memory at shutdown, then productivity is improved, but reliability deteriorates when steering wheel is turned during off state
Solution Approach 1:
The invention continuously detects relative steering angles during system operation and uses this feedback information to correct the stored absolute steering angle value upon system startup. By incorporating this feedback mechanism, the system maintains reliable steering angle accuracy even when the steering wheel position changes during the off state, while still achieving fast startup productivity
Solution Approach 2:
The invention dynamically adjusts the steering angle detection approach by transitioning from a static stored value to a dynamically corrected value. The stored absolute steering angle is continuously refined using real-time relative steering angle detection, enabling the system to adapt to steering wheel movements during off state while maintaining both startup speed and angle accuracy
Data Source
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AI summary
To provide a steering angle detecting apparatus for a vehicle, capable of accurately detecting an absolute steering angle of a steering mechanism and an electric power steering apparatus including the same. When an ignition is turned off, an absolute steering angle detection value φa immediately before the ignition is turned off is stored as an absolute steering angle stored value φam in a non-volatile memory (19) and a CAN relative steering angle φrc immediately before the ignition is turned off is stored as a relative steering angle stored value φrm in the non-volatile memory (19). When the ignition is turned on, a value obtained by correcting the absolute steering angle stored value φam with an angle (a difference between the relative steering angle stored value φrm and the CAN relative steering angle φrc) by which steering is performed during a period from the time when the ignition is turned off until the time when the ignition is turned on is set as an initial value of the absolute steering angle. Then, a provisional absolute steering angle calculated value φap is calculated on the basis of the relative steering angle φrc, using the initial value of the absolute steering angle as a reference.