Steering Wheel Grip Detection Circuit Topology
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Solution Overview
Problem
Conventional steering wheel grip detection devices are prone to errors in hand contact detection due to the influence of thermostat opening or closing on the capacitance value of the heater, leading to incorrect grip detection.
Innovation Solution
A steering wheel grip detection device is designed with a series circuit comprising a heater and an inductance element, connected in series with a thermostat, and a capacitive element in parallel, which reduces the impact of thermostat opening or closing on the electrostatic sensor circuit's output by stabilizing the capacitance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a heater is used for both heating and grip detection, then the device can serve dual purposes, but the thermostat opening or closing causes errors in grip detection
Solution Approach 1:
The heater wiring is divided into two separate circuits: a heating circuit controlled by the thermostat and a detection circuit connected to the electrostatic sensor. This segmentation allows the heater to serve dual purposes while isolating the detection function from thermostat interference, resolving the contradiction between versatility and measurement precision.
Solution Approach 2:
The inductance element acts as an intermediary component in the detection circuit, providing a stable reference impedance that is not affected by thermostat switching. This intermediary element enables accurate grip detection while the heater performs its heating function independently.
2Device complexity
If the heater capacitance is used for grip detection, then the existing heater can be utilized, but thermostat switching causes capacitance value changes that lead to detection errors
Solution Approach 1:
The heater circuit is segmented into heating and detection pathways. The detection pathway includes the inductance element and electrostatic sensor that measures capacitance changes due to hand proximity, while the heating pathway remains controlled by the thermostat. This segmentation maintains reliability by isolating the detection signal from thermostat-induced capacitance variations.
Solution Approach 2:
The system monitors changes in capacitance parameters caused by hand proximity to the steering wheel. The electrostatic sensor detects these capacitance variations in the detection circuit, which remain stable despite thermostat operations, enabling reliable grip detection using the existing heater infrastructure.
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 effectively minimizes errors in grip detection by maintaining a consistent capacitance value, regardless of thermostat state, thereby improving the accuracy of hand grip recognition on the steering wheel.
Implementation Method 1
an electrostatic sensor circuit electrically connected to the lead. The electrostatic sensor circuit detects a grip on a steering wheel by a capacitance value of the heater
Implementation Method 2
a heater and an inductance element that are connected in series with each other
Data Source
AI summary
A steering wheel grip detection device includes a positive electrode terminal electrically connected to a positive electrode of a power source and a negative electrode terminal electrically connected to a negative electrode of the power source. The steering wheel grip detection device further includes a thermostat, a heater, and an inductance element that are electrically connected with one another in this order in series wiring from the positive electrode terminal to the negative electrode terminal, as well as a capacitor through which a wiring path from the thermostat to the heater is electrically connected with the negative electrode terminal. The steering wheel grip detection device has an electrostatic sensor circuit that is electrically connected with a wiring path from the inductance element to the heater and that detects a grip on a steering wheel by a capacitance value of the heater.