Steering Wheel Grip Sensing With Dynamic Capacitance Thresholds
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Solution Overview
Problem
Existing steering wheel grip determination systems, such as those using electrostatic capacitance sensors, are prone to misjudgment due to variations in environmental conditions like temperature and humidity, necessitating additional sensors for accurate grip detection.
Innovation Solution
A steering device with multiple electrostatic capacitance measurement devices at different positions on the steering wheel, which adjusts the capacitance threshold based on the similarity of measurement value trends to account for environmental changes, eliminating the need for separate temperature and humidity sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed capacitance threshold is used for grip determination, then the system configuration remains simple, but misjudgment occurs due to environmental state changes
Solution Approach 1:
The capacitance threshold is changed from a fixed value to a dynamic value that automatically adjusts according to environmental conditions. The threshold is corrected based on the degree of similarity in change trends of measurement values from multiple measurement devices, allowing the system to adapt to temperature and humidity changes without adding complex sensor systems.
2Reliability
If temperature and humidity sensors are added to correct for environmental changes, then grip determination accuracy improves, but device complexity increases
Solution Approach 1:
The electrostatic capacitance measurement devices themselves provide the information needed for environmental correction. By analyzing the degree of similarity in change trends of measurement values from multiple devices, the system self-determines when environmental corrections are needed and adjusts the capacitance threshold accordingly, eliminating the need for separate temperature and humidity sensors.
Solution Approach 2:
The electrostatic capacitance measurement devices serve dual functions: they detect both grip presence/absence and environmental state changes. The same measurement values used for grip determination are also used to calculate the degree of similarity and correct the capacitance threshold, making the existing sensors multi-functional and avoiding additional hardware.
3Reliability
If multiple measurement devices with different installation positions are used, then environmental state compensation becomes possible, but device complexity increases
Solution Approach 1:
The steering wheel is divided into multiple detection regions with measurement devices installed at different positions. Each measurement device independently monitors its local area, and the system compares the change trends of measurement values from these segmented regions to determine environmental state changes, enabling spatial distribution of sensing functions.
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
Precise grip detection is maintained despite environmental variations by dynamically adjusting the capacitance threshold, reducing misjudgment and simplifying the system configuration.
Implementation Method 1
a measurement device (for example, the measurement circuits 42, 52 described later) which measures an electrostatic capacitance of an electrode (for example, the electrodes 40, 50 described later) provided to the steering wheel
Data Source
AI summary
A steering device includes: a plurality of proximity sensors having different installation positions of electrodes on the steering wheel; and a grip determination device which determines the presence/absence of gripping of the steering wheel based on filter values Ch_R_f(n), Ch_L_f(n) of measurement values from the plurality of proximity sensors. The grip determination device includes: a capacitance threshold setter which sets a reference value Ch_0 relative to the electrostatic capacitance of the electrode; and a determiner which determines the presence/absence of gripping based on the difference between the measurement values Ch_R_d(n), Ch_L_d(n) and the reference value Ch_0. The capacitance threshold setter determines the necessity for correction of the reference value Ch_0 based on a degree of similarity in change trends of the filter values Ch_R_f(n), Ch_L_f(n) of the plurality of proximity sensors.