Steering Wheel Hand Detection With Moisture Compensation
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Solution Overview
Problem
The influence of water retention in steering wheel materials on capacitive sensor systems for hand detection is significant, often leading to erroneous detection of gripping states due to changes in capacitive and ohmic couplings.
Innovation Solution
A method that includes performing diagnostic measurements to determine the environmental influences caused by water retention on the capacitive and ohmic couplings between the sensor electrode and the steering wheel core, and using these measurements to correct the determination of the capacitive coupling of the sensor electrode to the reference potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the steering wheel core is connected to a fixed ground potential to avoid interfering effects, then the stability of the measurement is improved, but the capacitance coupling between the sensor electrode and the steering wheel core increases significantly, reducing measurement precision
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring the voltage change of the sensor electrode during a diagnostic discharge phase. This intermediary measurement of the discharge curve allows indirect determination of the capacitive coupling conditions without directly measuring the problematic capacitance values, thereby resolving the contradiction between stability and precision
Solution Approach 2:
The patent changes the measurement parameter from direct capacitance measurement to voltage change measurement during discharge. By measuring the voltage change ΔU of the sensor electrode when discharging through a known resistance, the system can infer capacitive coupling conditions without being affected by the large static capacitance values, thus maintaining both stability and precision
2Adaptability or versatility
If water retention in steering wheel materials is present, then the manufacturing flexibility and comfort are improved, but the capacitive and ohmic couplings change, leading to erroneous detection and reducing reliability
Solution Approach 1:
The patent performs preliminary diagnostic measurements during the initialization phase to establish baseline values for capacitive and ohmic couplings under current environmental conditions. By pre-measuring and storing reference values that account for water retention effects, the system can later compensate for these effects during actual hand detection, maintaining reliability while allowing material flexibility
Solution Approach 2:
The patent implements a feedback mechanism where diagnostic measurements continuously monitor changes in capacitive and ohmic couplings caused by water retention. The system uses this feedback information to dynamically adjust and correct hand detection measurements, thereby maintaining detection reliability despite variations in material moisture content
3Measurement precision
If diagnostic measurements are performed to determine environmental influences, then the measurement precision is improved, but the device complexity and measurement time increase
Solution Approach 1:
The patent merges the hand detection function with the diagnostic measurement function into a single sensor electrode system. The same sensor electrode used for hand detection also serves as the measurement point for diagnostic purposes during the discharge phase. This merging eliminates the need for separate diagnostic sensors or additional hardware, improving precision without significantly increasing device complexity
Solution Approach 2:
The patent implements periodic diagnostic measurements at defined intervals (e.g., during initialization or at regular time periods) rather than continuous monitoring. This periodic approach maintains measurement precision by regularly updating environmental compensation data while minimizing the additional time and computational resources required, thus balancing precision with system complexity
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 approach allows for real-time correction of the hand detection measurement, thereby reducing errors caused by water retention and ensuring accurate detection of gripping states.
Implementation Method 1
the presence of the hand in a detection range of a sensor structure including a sensor electrode(s) connected to an input/output of a sensor electronics system brings about a change in a capacitive coupling of the sensor electrode to a reference potential
Implementation Method 2
the capacitive coupling CHand and the ohmic coupling RHumid between the sensor electrode and the steering wheel core caused by water retention in the steering wheel
Implementation Method 3
the capacitive coupling CHand and the ohmic coupling RHumid between the sensor electrode and the steering wheel core caused by water retention in the steering wheel
Data Source
AI summary
A method for detecting a presence of a human hand in a gripping area of a steering wheel with the use of a capacitive sensor system is provided. The steering wheel includes a metal steering-wheel core connected to ground. The presence of the hand in a detection range of a sensor electrode arranged on the steering wheel and connected to sensor electronics brings about a change in a capacitive coupling (CHand) of the sensor electrode at a reference potential as compared with a reference state without the presence of the hand. Via a diagnostic measurement, a measure (ΔUHumid) of environmental influences (CHumid, RHumid) on capacitive and ohmic couplings between the sensor electrode and the steering-wheel core attributable to water retention in the steering wheel is determined. The measure of the environmental influences is used for correcting the determination of the capacitive coupling of the sensor electrode at the reference potential.