Steering Wheel Grip Detection Circuit Topology
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Solution Overview
Problem
Existing steering wheel grip detection devices are prone to errors in detecting hand contact due to the influence of the open/closed state of the thermostat, which affects the capacitance of the heater and leads to incorrect grip detection.
Innovation Solution
A steering wheel grip detection device is designed with a series circuit including an inductance element, a thermostat, and a heater, where the electrostatic sensor circuit is connected to detect grip through an electric or electromagnetic field, and a voltage or current detecting circuit is used to determine the open/closed state of the thermostat, reducing its influence on hand contact detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the thermostat is used to control the heater temperature, then the heater can prevent overheating and adjust temperature, but the open/closed state of the thermostat causes fluctuations in the electrostatic capacitance of the heater, leading to errors in hand grip detection
Solution Approach 1:
The patent segments the detection function by introducing a separate electrostatic sensor circuit that is electrically isolated from the heater circuit. The sensor circuit connects to the steering wheel through a different path (via the inductance element and thermostat in series, but with the sensor tapping off at a point that doesn't share the same current path as the heater), allowing independent measurement of electrostatic capacitance changes due to hand contact without being affected by thermostat-induced capacitance variations in the heater circuit.
Solution Approach 2:
The patent introduces an inductance element as an intermediary component between the power supply and the heater/thermostat circuit. The electrostatic sensor circuit connects through this inductance element, which acts as a mediator that blocks direct current while allowing the sensor to detect electrostatic field changes. This intermediary structure isolates the sensor measurements from the thermal control circuit's capacitance fluctuations.
2Adaptability or versatility
If the heater circuit is used for grip detection, then the existing heater infrastructure can be utilized, but the thermostat's operation introduces noise and false signals in the detection
Solution Approach 1:
The patent segments the electrical circuit into two independent paths: one for heating (power supply → thermostat → heater) and one for sensing (power supply → inductance element → electrostatic sensor circuit). This segmentation allows the system to use the existing heater infrastructure while maintaining a separate, reliable detection path that is not contaminated by thermostat operations.
Solution Approach 2:
The patent replaces the direct electrical connection method with an electromagnetic field-based detection method. Instead of measuring electrical parameters directly in the heater circuit that are affected by the mechanical thermostat switch, the system uses an electrostatic sensor to detect changes in electric field capacitance caused by hand contact, substituting a more reliable field-based measurement for the problematic circuit-based 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 device effectively reduces the impact of the thermostat's state on grip detection, providing accurate identification of hand contact with the steering wheel by correcting for voltage and current fluctuations associated with the thermostat's operation.
Implementation Method 1
an electrostatic sensor circuit electrically connected to the end of the heater to which the inductance element is electrically connected, or to the middle of the wiring path of the heater, to detect a grip of the steering wheel by means of an electric or electromagnetic field
Data Source
AI summary
A steering wheel grip detection device includes a series circuit including an inductance element, a thermostat incorporated into a steering wheel, and a heater incorporated into the steering wheel; an electrostatic sensor circuit that detects a grip of the steering wheel by means of an electric or electromagnetic field; and a voltage detecting circuit that detects an open/closed state of the thermostat.