Steering Wheel Grip Detection With Adaptive 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 that adjusts the capacitance threshold based on the slope of the electrostatic capacitance measurement value, distinguishing between changes caused by environmental conditions and driver interactions, without requiring separate sensors for temperature and humidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed capacitance threshold is used for grip determination, then the device complexity is reduced, but measurement precision deteriorates due to environmental variations
Solution Approach 1:
The capacitance threshold is changed from a fixed value to a dynamic value that automatically adjusts based on the slope of measurement values. The system continuously monitors the rate of change and adapts the threshold accordingly, transforming a static parameter into a dynamic one that responds to environmental conditions without adding complex sensor systems.
Solution Approach 2:
The system uses feedback from the measurement value changes to adjust the capacitance threshold. By monitoring the slope of measurement values and using this information to modify the threshold, the system creates a closed-loop control mechanism that improves measurement precision while maintaining relatively simple device architecture.
2Measurement precision
If temperature and humidity sensors are added to compensate for environmental variations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The electrostatic capacitance sensor performs both its primary function of detecting grip presence and a secondary function of monitoring environmental variations. By analyzing the slope of measurement values, the system uses the existing sensor's data to self-adjust the capacitance threshold, eliminating the need for separate temperature and humidity sensors.
Solution Approach 2:
The electrostatic capacitance sensor is made multi-functional by using it for both grip detection and environmental condition monitoring. The same sensor that detects driver grip also provides information about temperature and humidity changes through its measurement value slope, allowing one component to serve multiple purposes.
3Measurement precision
If the capacitance threshold is changed based on measurement value changes, then measurement precision is improved, but device complexity increases due to additional control logic
Solution Approach 1:
The system changes the parameter of capacitance threshold based on the slope parameter of measurement values. By establishing a relationship between these two parameters and automatically adjusting the threshold according to slope conditions, the system improves measurement precision through parameter adaptation rather than adding complex hardware structures.
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 determination of steering wheel grip presence/absence is achieved, reducing misjudgment and contributing to sustainable transportation systems with a simpler configuration.
Implementation Method 1
a measurement device (for example, the measurement circuit 42 described later) which measures an electrostatic capacitance of an electrode (for example, the electrode 40 described later) provided to the steering wheel
Data Source
AI summary
A steering device includes a measurement circuit which measures electrostatic capacitance of an electrode provided to a steering wheel, and a grip determination device which determines presence/absence of gripping of the steering wheel based on a measurement value Ch_d from the measurement circuit. The grip determination device includes a capacitance threshold setter which sets a reference value Ch_0 for the electrostatic capacitance of the electrode, and a determiner which determines presence/absence of gripping of the steering wheel based on a difference between the measurement value Ch_d and reference value Ch_0. The capacitance threshold setter changes the reference value Ch_0(n) according to a change amount dCh_0(n) in the measurement value when the absolute value |a(n)| for the slope of the filter value Ch_d_f(n) of the measurement value was less than a predetermined slope threshold a_th.