Steering Lash Startup Detection Using Signal Decay Rate
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Solution Overview
Problem
Advanced Driver Assist Systems (ADAS) vehicles operating in SAE Level 3+ environments lack the human driver's ability to detect steering system faults through tactile feedback, making it difficult to diagnose lash conditions in mechanical components like the steering system, which can lead to catastrophic failures.
Innovation Solution
A lash detection diagnostic method that involves sending excitation motor commands to the steering system, measuring sensor signals, determining the decay rate of signal magnitude at various frequencies, and diagnosing a lash condition if the decay rate exceeds a predetermined threshold, using a control module with enabling, measurement, and classification modules to automate the detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If human driver tactile feedback is used to detect steering faults, then fault detection capability is improved, but this approach cannot be applied in ADAS Level 3+ vehicles where no human driver is present
Solution Approach 1:
The patent replaces the mechanical/tactile feedback system (human driver's hand feeling) with an electronic sensing system. The controller applies excitation motor commands to the steering system and measures sensor signals (current, voltage, position) to detect lash conditions through electrical and mechanical parameter analysis, enabling fault detection in automated vehicles without human drivers.
Solution Approach 2:
The patent introduces an intermediary diagnostic system between the steering system and the fault detection function. The controller acts as an intermediary that applies test signals (excitation motor commands) to the steering system, measures the response through sensors, and analyzes the data to detect lash conditions, replacing the direct human tactile detection path.
2Reliability
If automated lash detection using excitation motor commands and decay rate analysis is implemented, then fault detection capability in automated vehicles is improved, but system complexity increases
Solution Approach 1:
The patent makes the existing motor control system and sensors serve multiple functions. The motor control system not only controls steering assistance but also applies excitation commands for diagnostic testing. The sensors not only monitor normal operation but also capture test response signals. This multi-functionality reduces the need for separate diagnostic hardware, thereby limiting complexity increase.
Solution Approach 2:
The steering system performs its own self-diagnosis through the automated lash detection process. The controller applies excitation commands, measures the system's own response, and analyzes the decay rate to detect lash conditions. This self-service approach eliminates the need for external diagnostic equipment or human inspection, improving reliability while keeping the system integrated and relatively simple.
3Ease of operation
If traditional startup diagnostics are used, then diagnostic simplicity is maintained, but lash conditions cannot be detected in automated driving systems
Solution Approach 1:
The patent performs preliminary diagnostic testing during the startup phase of the vehicle. The controller applies excitation motor commands and measures sensor signals before the vehicle begins normal operation. This preliminary action allows lash conditions to be detected early, ensuring the steering system is functioning correctly before automated driving commences, thereby maintaining diagnostic simplicity while enabling reliable lash detection.
Data Source
AI summary
Technical solutions are described for lash detection diagnostic in a steering system. An example method includes sending, by a controller, an excitation motor command to a motor control system. The method further includes measuring, by the controller, a sensor signal generated in response to the excitation motor command. The method further includes determining, by the controller, a decay rate of a change in magnitude of the signal at a plurality of frequencies. The method further includes diagnosing, by the controller, that the steering system has a lash condition based on the decay rate exceeding a predetermined threshold.