Steering Wheel Grip Sensing with Switchable Sensor-Shield Electrodes
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Solution Overview
Problem
Conventional grip detection devices for steering wheels suffer from inaccurate grip sensing due to variations in parasitic capacitance caused by environmental factors, leading to false sensing results and increased component count and manufacturing costs.
Innovation Solution
A grip detection device for a steering wheel with a first electrode wider than a second electrode, allowing switching between modes where the first electrode functions as a sensor and the second as a shield, or vice versa, and incorporating a control circuit to detect grip based on capacitance changes in these modes, while optionally acting as a heater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor electrode and shield electrode are arranged parallel to each other on a pad substrate, then grip detection capability is provided, but parasitic capacitance varies due to environmental factors causing inaccurate sensing
Solution Approach 1:
The patent implements dynamic role switching between the first and second electrodes. The control circuit alternates between a first mode where the first electrode is the sensor electrode and the second electrode is the shield electrode, and a second mode where their roles are reversed. This dynamic configuration allows the system to adapt to environmental changes and distinguish genuine grip signals from parasitic capacitance variations caused by temperature and humidity.
Solution Approach 2:
The patent changes the operational parameters by switching the functional roles of the electrodes between two distinct modes. By measuring capacitance in both modes and comparing the results, the system can identify and compensate for environmental variations in parasitic capacitance, thereby improving grip detection accuracy despite changes in temperature and humidity conditions.
2Measurement precision
If multiple electrodes are used for grip detection with role switching, then sensing accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the first and second electrodes to serve dual purposes. Each electrode can function as either a sensor electrode or a shield electrode depending on the operational mode. This universal design allows the same physical electrodes to perform multiple functions, improving measurement precision without proportionally increasing device complexity, as the hardware structure remains relatively simple while the control logic handles the role switching.
3Adaptability or versatility
If the first electrode is wider than the second electrode, then the first electrode can effectively serve as both sensor and shield, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating an asymmetric electrode configuration where the first electrode has a larger projected area than the second electrode. This deliberate local difference in dimensions enables the first electrode to effectively serve both as a sensor electrode and a shield electrode when needed. The asymmetric design provides functional versatility while the dimension difference is controlled within manufacturing tolerances to ensure proper capacitance characteristics in both operational modes.
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
This configuration enhances grip sensing accuracy by isolating capacitance variations from environmental factors, reduces component count, and maintains heating functionality without increasing manufacturing costs.
Implementation Method 1
the shield electrode is electrically coupled to a voltage source to create a capacitance between the shield electrode and the sensor electrode, and the sensor electrode can detect a change in the capacitance
Implementation Method 2
The shield electrode can also heat the surface of a vehicle part
Data Source
AI summary
A grip detection device for a steering wheel includes: a first electrode arranged at a rim; a second electrode arranged at the rim; and a control circuit, in which the first electrode is wider in projected area than the second electrode, the control circuit allows switching between: a first mode in which the first electrode serves as a sensor electrode and the second electrode serves as a shield electrode; and a second mode in which the first electrode serves as the shield electrode and the second electrode serves as the sensor electrode, and the control circuit further: obtains a first-mode capacitance detected by the first electrode serving as the sensor electrode in the first mode and a second-mode capacitance detected by the second electrode serving as the sensor electrode in the second mode; and detects a grip on the steering wheel based on the first-mode capacitance and the second-mode capacitance.