Steering Wheel Capacitance Sensor Failure Detection Under Grip
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Solution Overview
Problem
Existing steering wheel units cannot diagnose failures in capacitance sensors when the steering wheel is gripped.
Innovation Solution
A hands-on detection device comprising a core metal, a shield electrode, a sensor electrode, and a control unit that acquires capacitance values and determines failure states regardless of whether the steering wheel is gripped or not, using short-circuiting and voltage measurement techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steering wheel is gripped during diagnosis, then the capacitance sensor cannot be diagnosed for failure, but if the steering wheel is not gripped, then the diagnosis can be performed
Solution Approach 1:
The control unit performs failure determination by short-circuiting the shield electrode and core metal before hands-on detection, establishing a known reference state. This preliminary action creates a baseline capacitance value that enables failure diagnosis regardless of subsequent grip states.
Solution Approach 2:
The diagnosis process is divided into distinct operational modes: a first operation mode for failure determination with short-circuited shield and core metal, and a second operation mode for normal hands-on detection. This segmentation allows each mode to be optimized independently, enabling failure diagnosis to occur in the first mode before grip detection in the second mode.
2Reliability
If separate circuit configurations are used for hands-on detection and failure determination, then accurate diagnosis is possible, but device complexity increases
Solution Approach 1:
The capacitance sensor and associated circuitry serve dual functions: failure determination by measuring capacitance in the short-circuited state and normal hands-on detection by measuring capacitance in the operational state. This multi-functionality eliminates the need for separate dedicated failure diagnosis hardware, reducing overall device complexity while maintaining diagnostic accuracy.
Solution Approach 2:
The circuit configuration dynamically switches between different operational states through the control unit's management of the first switch, which connects or disconnects the short-circuiting path between the shield electrode and core metal. This dynamic reconfiguration allows the same hardware to perform different measurement functions without requiring parallel static circuits.
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 failure determination of capacitance sensors regardless of the steering wheel's grip state, ensuring reliable detection and reducing production costs by integrating hands-on and failure determination processes within a single circuit configuration.
Implementation Method 1
acquire a capacitance value of the sensor electrode (21) in a state in which the shield electrode (22) and the core metal (23) are short-circuited
Data Source
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AI summary
A hands-on detection device of a steering wheel according to one embodiment of the present invention is a hands-on detection device (1) of a steering wheel (2), comprising: a core metal (23); a shield electrode (22) provided outside the core metal (23) and separated by an insulator (In); a sensor electrode (21) further provided outside the shield electrode (22) and separated by an insulator (In); and a control unit (11) configured to acquire the capacitance value of the sensor electrode (21) in a state in which the shield electrode (22) and the core metal (23) are short-circuited, and determine whether or not there is a failure based on the capacitance value.