Vehicle Seat Occupant Sensing with LC Suppression of Heater Interference
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Solution Overview
Problem
Existing occupant detection systems in vehicles face interference from seat heater control circuitry, which affects the accuracy of electric field impedance measurements used to determine the presence of an occupant.
Innovation Solution
An occupant detection system that includes an electrode, a signal generator producing signals at multiple frequencies, occupant detection circuitry, and an LC circuit to suppress capacitance interference from control circuitry, allowing for the determination of resistance, capacitance, and inductance, and comparison to a threshold to detect occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a seat heater with control circuitry is installed in the vehicle seat, then the seat heating function is provided, but the accuracy of electric field impedance measurement for occupant detection is degraded due to capacitive interference from the control circuitry
Solution Approach 1:
The patent applies the 'Blessing in disguise' principle by using the LC circuit to convert the harmful capacitive interference from the seat heater control circuitry into a beneficial filtering effect. The LC circuit is specifically designed to suppress capacitance at the operating frequency of the occupant detection system, thereby transforming the interference into a useful signal conditioning mechanism that improves measurement accuracy while maintaining seat heating functionality
Solution Approach 2:
The patent applies the 'Intermediary' principle by introducing an LC circuit as an intermediary component between the seat heater control circuitry and the occupant detection electrode. This intermediary LC circuit acts as a mediator that blocks the harmful capacitive coupling from the control circuitry while allowing the occupant detection signals to pass through, thus resolving the conflict between seat heating and accurate occupant detection
2Reliability
If electric field impedance measurement is used for occupant detection, then the presence of an occupant can be determined, but the measurement accuracy is degraded by capacitance from control circuitry elements such as transistors
Solution Approach 1:
The LC circuit transforms the harmful capacitance from control circuitry elements into a controlled filtering mechanism. By tuning the LC circuit to resonate at the detection frequency, the harmful capacitive effects are converted into a selective signal passband that enhances the desired detection signal while attenuating interference
Solution Approach 2:
The patent applies 'Parameter changes' by adjusting the electrical parameters of the LC circuit (inductance and capacitance values) to match the operating frequency of the occupant detection system. This parameter optimization allows the LC circuit to effectively suppress capacitance interference at specific frequencies while maintaining the integrity of the occupant detection signal
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 detects the presence of an occupant by minimizing capacitive interference from seat heater control circuitry, enabling accurate occupancy determination and reducing the need for duplicate components, thus lowering costs.
Implementation Method 1
an LC circuit coupled to the electrode and the control circuitry for suppressing capacitance generated by the control circuitry
Implementation Method 2
applying a plurality of signals at a plurality of frequencies to the electrode to generate an electric field proximate to the vehicle seat
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An occupant detection system (20) and method are provided for detecting an occupant seated in a vehicle seat (10). An electrode (12) is arranged in a seat (10) proximate to an expected location of an occupant for sensing an occupant proximate thereto. The electrode (12) may be integrated with a seat heater. Control circuitry (16) controls the seat heater. A signal generator (24) is coupled to the electrode (12) and configured output to the electrode (12) a plurality of signals at a plurality of frequencies. Occupant detection circuitry (22) detects voltages responsive to the plurality of signals at the plurality of frequencies and detects a state of occupancy based on the detected voltages. An LC circuit (30) coupled to the electrode (12) and the control circuitry (16) suppresses capacitance generated by the control circuitry (16).