Steering Wheel Grip Detection Using Position-Based Torque Thresholds
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Solution Overview
Problem
Conventional grip determining systems inaccurately assess whether a driver is gripping a steering operation member due to varying output values of the steering torque sensor based on the contact position, leading to incorrect determinations when thresholds are set without considering the driver's contact position on the steering operation member.
Innovation Solution
A grip determining system that includes a contact sensor to detect capacitance variations based on the driver's contact position and a steering torque sensor to adjust thresholds accordingly, ensuring accurate determination of grip based on the estimated contact position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed threshold is set for steering torque to determine grip, then the determination process is simple, but the accuracy of grip determination deteriorates due to varying contact positions
Solution Approach 1:
The threshold for steering torque is made dynamic rather than fixed. The controller adjusts the threshold based on the contact position detected by the contact sensor. When the driver's hand is detected at different positions on the steering wheel, the system dynamically selects appropriate threshold values to maintain accurate grip determination across various contact scenarios.
Solution Approach 2:
The system changes the parameter (threshold value) based on the contact position. Multiple threshold values are predefined corresponding to different contact positions, and the controller selects the appropriate threshold based on where the driver's hand is detected on the steering wheel, thereby maintaining determination accuracy across different grip locations.
2Measurement precision
If the threshold is set to a relatively small value, then grip determination sensitivity increases, but false positive determinations increase when the driver is not gripping
Solution Approach 1:
Different threshold values are assigned to different contact positions on the steering wheel. Each region of the steering wheel has an optimized threshold that accounts for the local characteristics of torque generation at that position. This ensures high sensitivity for detecting actual grip while maintaining reliability by preventing false positives through position-specific threshold selection.
3Reliability
If the threshold is set to a relatively large value, then false positive determinations decrease, but false negative determinations increase when the driver is gripping
Solution Approach 1:
The threshold parameter is adjusted based on contact position to balance sensitivity and reliability. For contact positions where torque values are naturally lower, lower thresholds are applied to maintain detection sensitivity. For positions where torque values are naturally higher, higher thresholds are applied to reduce false positives, thereby optimizing both sensitivity and reliability across all grip scenarios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise threshold setting according to the driver's contact position, accurately determining grip on the steering operation member, thereby ensuring safe transfer of vehicle control to the driver.
Implementation Method 1
a contact sensor (35) provided in a steering operation member (22) of a vehicle (1) and configured such that capacitance of the contact sensor varies according to a contact position of a driver on the steering operation member
Data Source
AI summary
A grip determining system includes a contact sensor provided in a steering operation member of a vehicle and configured such that capacitance of the contact sensor varies according to a contact position of a driver on the steering operation member, a steering torque sensor configured to output an output value according to steering torque generated by a steering operation by the driver, and a controller configured to determine whether the driver is gripping the steering operation member. The controller is configured to estimate the contact position of the driver on the steering operation member based on the capacitance of the contact sensor, set a threshold according to the estimated contact position of the driver, and determine that the driver is gripping the steering operation member in a case where the output value of the steering torque sensor is equal to or more than the threshold.