Tire Pressure Sensor Motion Detection via Signal Variance
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Solution Overview
Problem
Conventional Tire Pressure Monitoring Systems (TPMS) face issues with motion detection due to the size and sensitivity of shock sensors, and the expense and calibration requirements of accelerometers, leading to false readings and increased costs.
Innovation Solution
A TPMS device that uses a pressure sensor to determine vehicle motion by analyzing the power of the output signal, specifically through variance measurement across the entire frequency spectrum or specific frequency bands, eliminating the need for shock sensors and accelerometers, thereby reducing cost and space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shock sensors are used for motion detection, then vehicle motion can be detected, but the device size increases and false detection occurs due to sensitivity to contaminants
Solution Approach 1:
The patent extracts the motion detection function from dedicated shock sensors and implements it instead through analysis of pressure sensor output signal characteristics. By taking out the separate motion sensing component and using the existing pressure sensor data for motion detection, the device size is reduced while maintaining motion detection capability through signal power analysis that is insensitive to PCB contaminants.
2Reliability
If shock sensors are used for motion detection, then vehicle motion can be detected, but susceptibility to contaminants increases causing false readings
Solution Approach 1:
The patent replaces the mechanical shock sensor system with an electrical signal analysis approach. Instead of using a mechanical device that directly senses physical shocks and is susceptible to PCB contaminants, the system uses electrical signal processing of pressure sensor output to detect motion-induced pressure variations, thereby eliminating sensitivity to flux residue and moisture on the PCB.
3Reliability
If accelerometers are used for motion detection, then vehicle motion can be detected, but calibration requirements and cost increase
Solution Approach 1:
The patent implements self-service by using the pressure sensor's own output signal for motion detection purposes. The system analyzes the power and characteristics of the pressure signal itself to determine vehicle motion, eliminating the need for separate accelerometer components and their associated calibration procedures. This self-utilization of existing sensor data simplifies manufacturing and reduces costs.
4Reliability
If motion sensing devices are included in TPMS, then vehicle motion can be detected, but the space available on the wheel unit is reduced
Solution Approach 1:
The patent applies multi-functionality by enabling the pressure sensor to serve dual purposes: measuring tire pressure and detecting vehicle motion. By analyzing the power and characteristics of the pressure sensor output signal, the system extracts motion detection capability from the existing pressure sensing component, eliminating the need for separate motion sensing devices and freeing up PCB space for other functions.
Data Source
AI summary
A tire pressure monitoring device for a wheeled vehicle that is capable of detecting vehicle motion from the output of a pressure sensor. The device determines from the output signal an indication of the power of the signal, for example the variance of the signal, and detects if the vehicle is stationary or in motion depending on the determined indication of power. The device may determine that the vehicle is in motion if the determined indication of power exceeds a threshold value.