Steering Torque Threshold Control for Reliable Hands-Free Detection
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Solution Overview
Problem
Existing steering support devices for vehicles face challenges in accurately determining whether the driver is gripping the steering wheel, leading to erroneous hand-free state detection due to torque fluctuations from control torque and road disturbances, which can be misinterpreted by setting inappropriate reference values.
Innovation Solution
The steering support device adjusts the reference value for determining hand-free state based on the direction of torque input, using multiple sensors and angle detection devices to differentiate between torque from the steering wheel and steered wheel, thereby setting a larger reference value when torque is input from the steered wheel side to reduce erroneous detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reference value is set to a large value to suppress erroneous hand-free detection, then the reliability of hand-free detection is improved, but the measurement precision of steering torque detection deteriorates due to control torque and road disturbances
Solution Approach 1:
The reference value is dynamically adjusted based on the detected torque direction. When torque from the steered wheel side is detected (indicating automatic steering or road disturbance), a larger reference value is applied. When torque from the steering wheel side is detected (indicating driver input), a smaller reference value is applied. This dynamic adjustment resolves the contradiction by adapting the reference value to the current operating condition.
Solution Approach 2:
Different reference values are applied to different torque input scenarios. The system identifies the torque source direction and applies locally optimized reference values: a larger reference value for steered-wheel-side torque input to prevent false hand-free detection, and a smaller reference value for steering-wheel-side torque input to maintain detection sensitivity.
2Measurement precision
If the reference value is set to a small value to improve steering torque detection sensitivity, then the measurement precision is improved, but the reliability of hand-free detection deteriorates due to false positive detection during automatic steering
Solution Approach 1:
The reference value changes dynamically based on the torque input direction detected by the steering torque sensor. During automatic steering when control torque is applied to the steering transmission system, the system detects torque from the steered wheel side and automatically increases the reference value, preventing false hand-free detection while maintaining the ability to detect actual hand-free states.
3Device complexity
If a single reference value is used for all torque input scenarios, then the device complexity is reduced, but the adaptability to different operating conditions deteriorates
Solution Approach 1:
The system changes the reference value parameter based on the detected torque input direction. By monitoring which side (steering wheel or steered wheel) is inputting torque, the system automatically selects the appropriate reference value, achieving adaptability to different operating conditions without requiring complex multiple sensor systems or sophisticated algorithms.
Data Source
AI summary
A steering support device including: a torque applying device configured to apply control torque to a steering transmission system between a steering wheel and a steered wheel; a steering torque sensor provided in the steering transmission system between the steering wheel and the torque applying device; and a control unit configured to determine that the driver is not holding the steering wheel when the torque Ts detected by the steering torque sensor is less than the reference value Tsc. The control unit sets a reference value Tsc to a larger value when determining that torque is input to the steering torque sensor from the steered wheel side than when determining that torque is input to the steering torque sensor from the steering wheel side.