Steer-by-Wire Sensor Redundancy via Motion Conversion
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Solution Overview
Problem
Steer-by-wire steering systems with sensors of different functions cannot employ the technique for determining inappropriate sensor detection values used in power steering systems, as they lack identical sensors for comparison.
Innovation Solution
A redundant steer-by-wire steering system with two systems of electric motors, each equipped with a motor rotation angle sensor and a steering amount sensor, allowing for detection-value inappropriateness determination by comparing detection values among the sensors, enabling the system to function even if one or two detection values are inappropriate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a steer-by-wire steering system uses sensors with different functions, then the system can be configured with diverse sensor types, but the system cannot determine inappropriate detection values using majority rule comparison
Solution Approach 1:
The patent introduces a motion converting mechanism as an intermediary that connects the motor rotation (detected by motor rotation angle sensors) to the steering rod motion (detected by steering amount sensor). This intermediary establishes a known functional relationship between the sensors, enabling cross-validation of detection values even though the sensors measure different physical quantities. The controller uses this relationship to determine whether detection values are appropriate through comparison.
2Reliability
If a power steering system uses identical sensors for comparison, then the system can easily determine inappropriate detection values using majority rule, but the system lacks the versatility of using different sensor types
Solution Approach 1:
The patent transforms the comparison approach from direct detection value comparison (requiring identical sensors) to comparison based on a known functional relationship. The controller converts detection values to a common reference frame using the motion converting mechanism's transmission ratio, enabling validation between sensors of different types that measure different parameters (motor rotation angle vs. steering rod position).
Data Source
AI summary
A vehicle steering system, including: a steering actuator including an electric motor, a steering rod configured to steer a wheel by a steering amount, and a motion converting mechanism configured to convert a rotating motion of a motor rotation shaft into a motion of the steering rod; first and second motor rotation angle sensors configured to detect a motor rotation angle; a steering amount sensor configured to detect a motion amount of the steering rod as the steering amount; and a controller configured to execute a steering amount control and to perform detection-value inappropriateness determination in which it is determined that any one or two of a detection value of the first motor rotation angle sensor, a detection value of the second motor rotation angle sensor, and a detection value of the steering amount sensor are inappropriate based on comparison among the detection values.