Direction-Specific Steering Torque Thresholds for Hands-Off Detection
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Solution Overview
Problem
Existing autonomous driving systems face challenges in accurately detecting whether a driver's hands are on or off the steering wheel due to inherent friction and compliance in the steering system, leading to false detections and increased costs from implementing touch sensors.
Innovation Solution
An autonomous steering control system adjusts torque thresholds based on rack velocity, reducing the torque required to be applied by the driver to account for friction and compliance, thereby minimizing false detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed torque threshold is used for hands-on detection, then the detection system is simple to implement, but friction and compliance in the steering system cause false detections
Solution Approach 1:
The patent implements dynamic torque threshold adjustment by monitoring rack velocity and adapting the threshold accordingly. When rack velocity exceeds a threshold, the system reduces the torque threshold to account for friction and compliance effects, thereby maintaining detection accuracy under varying operating conditions without requiring complex additional hardware
Solution Approach 2:
The system changes the torque threshold parameter based on rack velocity conditions. By detecting when the rack velocity exceeds a predetermined threshold, the system automatically adjusts the torque threshold downward to compensate for friction and compliance, resolving the contradiction between simple implementation and reliable detection
2Reliability
If torque threshold is reduced to account for friction, then false detections are minimized, but the torque required for normal steering operation decreases
Solution Approach 1:
The system dynamically adjusts the torque threshold only when rack velocity indicates friction and compliance are significant. During normal low-velocity steering operations, the full torque is available to the driver, while during high-velocity operations where friction dominates, the threshold is temporarily reduced to prevent false hands-off detections
Solution Approach 2:
The system creates a velocity-dependent copy or model of the friction and compliance effects, using rack velocity as a proxy to estimate when these effects become significant. This allows the torque threshold to be adjusted based on a simplified velocity criterion rather than directly measuring complex friction forces
Data Source
AI summary
Methods and apparatus to control a torque threshold for hands on/off detection are disclosed. An example non-transitory machine readable storage medium includes instructions to cause programmable circuitry to at least identify a velocity of a steering rack or an angular velocity associated with a steering wheel, cause a first torque threshold associated with a first rotational direction of the steering wheel to be different from a second torque threshold associated with a second rotational direction of the steering wheel when the velocity or the angular velocity satisfies a threshold, identify a steering torque encountered by the steering wheel, and detect a hands off condition when the steering torque does not satisfy the first torque threshold nor the second torque threshold.