Vehicle Power Steering Abnormality Detection Circuit
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Solution Overview
Problem
Existing power steering devices and control systems face challenges in accurately detecting abnormalities in state quantity detecting means, leading to misjudgments, especially on low-friction road surfaces where small steering torque variations can occur, affecting the reliability of steering assist functions.
Innovation Solution
A system comprising a first abnormality detection circuit for comparing steering torque, steering angle, and motor rotation angle signals, a comparison signal production circuit to generate additional signals, a second abnormality detection circuit to determine normal or abnormal values based on majority signal agreement, and a control continuation judgment circuit to maintain or limit steering assist control accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If detection signals from state quantity detecting means are compared to detect abnormalities, then abnormality detection function is provided, but abnormality detection accuracy is lowered due to conversion and estimation requirements
Solution Approach 1:
The patent creates calculation-based copy signals (steering torque calculation signal, steering angle calculation signal, motor rotation angle calculation signal) from the original detection signals. These copy signals are generated through mathematical calculations using multiple sensor inputs and are then compared with the original detection signals to detect abnormalities, avoiding direct comparison between different types of detection signals that would require conversion and estimation.
Solution Approach 2:
The patent introduces calculation signals as intermediary elements between the original detection signals. Instead of directly comparing detection signals from different sensors (which requires conversion), the system calculates intermediate signals from combinations of detection signals and uses these intermediaries for comparison, thereby maintaining accuracy while enabling abnormality detection.
2Reliability
If steering torque detection signal is used for abnormality detection, then abnormality detection is enabled, but misjudgment occurs on low-friction road surfaces where steering angle varies even with small steering torque
Solution Approach 1:
The patent makes the abnormality detection system universal by creating calculation signals that integrate multiple sensor inputs (steering torque sensor, steering angle sensor, motor rotation angle sensor). This multi-functional approach allows the system to adapt to various road conditions including low-friction surfaces, as the calculation signals reflect the combined state of all sensors rather than relying on a single sensor that may be affected by specific conditions.
Solution Approach 2:
The patent changes the parameters used for abnormality detection by calculating new signals from combinations of original parameters. Instead of directly using steering torque detection signal alone (which fails on low-friction surfaces), the system calculates a steering torque calculation signal from multiple parameters including steering angle and motor rotation angle, thereby adapting the detection parameters to work accurately under varying road conditions.
Data Source
AI summary
In a power steering device and a vehicle-mounted instrument, an abnormality detection accuracy of a state quantity detection means is increased.In an electric power steering device and a vehicle-mounted instrument that are each provided with a plurality of state quantity detection means, an abnormality detection for the state quantity detection means is carried out by comparing detection signals issued from the state quantity detection means provided on a redundant system, and by comparing the detection signals issued from the state quantity detection means with signals that are issued from other state quantity detecting means and calculated to be matched with the same unit as the compared detection signals, a value or close value that is possessed by the largest number of signals is set as a normal value.