Capacitive Sensor Seat Frame Grounding Detection
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Solution Overview
Problem
Capacitive sensors used for seat occupancy detection in vehicles face challenges due to the influence of the seat frame's grounding status, which can affect impedance measurements and lead to incorrect occupancy state determination if the seat frame is not properly grounded or if there are issues with the connection between the seat frame and the sensor.
Innovation Solution
A capacitive sensor system with a control and evaluation circuit that includes an antenna electrode and a seat frame connector, allowing the system to operate in different modes to measure electrical current flowing between the antenna electrode and ground, and to diagnose the seat frame's grounding status by temporarily coupling the measurement circuit to the seat frame, thereby determining if a path to ground is available and issuing error signals for faulty connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seat frame is not properly grounded or has connection issues, then the impedance measurement becomes unreliable, but adding grounding detection functionality increases device complexity
Solution Approach 1:
The patent combines the occupancy detection function with the seat frame grounding detection function into a single capacitive sensor system. The same antenna electrode and control circuit are used for both detecting occupancy and detecting seat frame grounding status, eliminating the need for separate detection systems and reducing overall device complexity while improving reliability
Solution Approach 2:
The capacitive sensor is designed to perform multiple functions: it detects both the occupancy state of the seat and the grounding status of the seat frame. The control circuit analyzes impedance measurements to determine both occupancy and grounding conditions, making the system universal and reducing the need for additional specialized components
2Loss of information
If the seat frame grounding status is not monitored, then the sensor system remains simple, but incorrect occupancy state determination occurs leading to loss of information
Solution Approach 1:
The system implements feedback by continuously monitoring the seat frame grounding status and using this information to adjust or validate occupancy detection results. The control circuit receives feedback about grounding conditions and uses this to determine whether impedance measurements accurately reflect occupancy status, preventing incorrect conclusions
Solution Approach 2:
The system performs preliminary detection of seat frame grounding status before or concurrent with occupancy detection. By first establishing whether the seat frame is properly grounded, the system prepares the measurement conditions and can adjust its interpretation of impedance measurements accordingly, preventing information loss from incorrect assumptions
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 effectively determines the seat frame's grounding state, preventing incorrect occupancy state determination and enabling the detection of faults in the sensor system, ensuring accurate occupancy detection and alerting client appliances of potential issues.
Implementation Method 1
The capacitive coupling strength is generally determined by applying an alternating voltage signal to an antenna electrode and by measuring the current flowing from that antenna electrode
Implementation Method 2
an oscillating voltage signal is applied to a transmit electrode, which builds up an oscillating electric field to ground
Implementation Method 3
This current may be measured by a transimpedance amplifier, which is connected to the sensing electrode and which converts the current flowing into the sensing electrode into a voltage proportional to the current
Implementation Method 4
the control and evaluation circuit is configured to measure (alternating) electrical current flowing into the seat frame connector
Data Source
AI summary
A capacitive sensor for a vehicle seat comprises an antenna electrode and a control and evaluation circuit operatively connected to the antenna electrode. The control and evaluation circuit is configured to operate in a first mode of operation, during which it measures alternating electrical current flowing between the antenna electrode and ground. The capacitive sensor comprises a seat frame connector for connecting the control and evaluation circuit to the seat frame of the vehicle seat. The control and evaluation circuit is configured to operate in a second mode of operation, during which it measures electrical current flowing into the seat frame connector.