TDR Steering Wheel Hand Detection with Aging Compensation
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Solution Overview
Problem
Existing hand positioning detection systems for steering wheels face challenges in reliability due to aging and environmental effects, such as temperature changes, which affect the accuracy of hand positioning detection.
Innovation Solution
A sensing system utilizing time-domain reflectometry (TDR) with an electrically conducting signal line arranged along the steering wheel rim, featuring a predefined electric impedance change, and a control unit to determine hand positioning by analyzing the travel time and reflection of measurement signals, compensating for propagation speed alterations caused by aging and environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive sensors are used for hand detection on steering wheel, then hand positioning detection capability is achieved, but detection accuracy deteriorates due to aging and environmental effects
Solution Approach 1:
The patent replaces capacitive sensing with a TDR-based electrical measurement system. Instead of using capacitive sensors that are sensitive to environmental factors, the invention uses time-domain reflectometry to send electrical signals through a signal line on the steering wheel and analyze reflections. This substitution of measurement principle eliminates the sensitivity to aging and temperature effects that plague capacitive sensors, thereby resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent changes the measurement parameter from capacitive coupling to signal propagation time. By measuring the time it takes for an electrical signal to travel along the signal line and reflect back, the system obtains hand positioning information that is independent of environmental factors. This parameter change from capacitance to time-of-flight measurement resolves the issue of detection accuracy deterioration due to aging and temperature.
2Reliability
If TDR measurement is used for hand detection, then detection reliability is improved, but system complexity increases
Solution Approach 1:
The patent makes the signal line serve multiple functions: it is both the structural component of the steering wheel and the measurement medium for TDR. The same signal line that provides structural integrity and aesthetic appearance also serves as the transmission medium for detection signals. This multi-functionality reduces system complexity by eliminating separate sensor components while maintaining high reliability through TDR measurement.
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
The system provides reliable detection of hand positioning on the steering wheel, unaffected by aging and environmental effects, enabling accurate determination of hand presence and position, including scenarios like one or two hands touching or grasping the wheel, and supports decision-making in Automatic Driver Assistance Systems.
Implementation Method 1
The invention is based on a TDR measurement for determining information about a hand positioning on a steering wheel. A time-dependent measurement signal is sent to a signal line and a reflected signal is received and analyzed.
Implementation Method 2
The signal line comprises an electric impedance change of predefined magnitude that is permanently arranged at a predefined position along the signal line. The measurement signal reflects off impedance changes to provide information about hand positioning.
Implementation Method 3
The signal line is arranged to extend along a major part of a surface of a rim of the steering wheel with a priori knowledge about a relation between a distance of any portion of the signal line from a reference point and information on a position on the rim. The system compensates for propagation speed alterations caused by aging and environmental factors.
Data Source
AI summary
A method of detecting a hand positioning on a steering wheel using a sensing system having an electrically conducting signal line on a rim of the steering wheel with a priori knowledge about a relation between a distance of any portion of the signal line from a reference point and information on a position on the rim, and which further includes an electric impedance change of predefined magnitude that is permanently arranged at a predefined position along the signal line, a signal voltage source, and a control and evaluation unit. From a received measurement signal traveling along the signal line and having been reflected by the electric impedance change and by another portion or portions of the signal line, a reference travel time is determined. A position or positions on the rim of the other portion or portions of the signal line can then be determined.