Batteryless SAW Sensor for Tire Pressure Monitoring
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Solution Overview
Problem
Conventional pressure and temperature sensors in harsh environments, such as vehicle tires, face issues with battery-related inaccuracies, weight, limited life, and complexity due to the need for battery replacement, as well as reliability concerns from electronic components and harsh conditions like high temperatures and vibrations.
Innovation Solution
A wireless and batteryless surface acoustic wave (SAW) sensor system with a SAW sensor and antenna, optionally combined with a passive RFID device, that operates without a battery by using radio frequency interrogation to measure pressure and temperature changes, allowing for easy installation and reduced component count, and is designed for harsh media applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional battery-powered sensors are used, then wireless communication capability is achieved, but device complexity and maintenance requirements increase due to battery replacement needs
Solution Approach 1:
The patent removes the battery and active electronics from the sensor unit, extracting the power source and signal generation functions to an external interrogator device. This leaves only the passive sensing elements (capacitive or piezoresistive) in the wheel sensor, dramatically reducing electronic complexity and eliminating maintenance requirements.
Solution Approach 2:
The patent replaces the mechanical/electrical battery-powered transmission system with a passive electromagnetic resonance system. The sensor modulates the impedance of its antenna circuit in response to pressure and temperature, and this modulation is detected by the external interrogator, eliminating the need for active electronics and batteries.
2Reliability
If battery-powered sensors are installed in tires, then pressure and temperature monitoring is enabled, but weight increases and serviceability deteriorates due to battery replacement requirements
Solution Approach 1:
The patent employs a disposable, maintenance-free sensor design where the entire wheel sensor unit is installed once and never requires service. The passive design with no battery means the sensor can remain in the tire for the lifetime of the tire itself, eliminating all serviceability issues associated with battery replacement.
Solution Approach 2:
The sensor system is self-powered through passive energy harvesting from the interrogator's electromagnetic field. The sensor automatically measures and transmits data without requiring any external power source or maintenance, making it completely self-service capable.
3Adaptability or versatility
If batteries are used in wheel sensors, then wireless communication is achieved, but measurement precision decreases due to temperature-dependent battery variations
Solution Approach 1:
The patent introduces an external interrogator as an intermediary that performs the signal processing and measurement calculations. The interrogator receives the passive impedance modulation signal from the sensor and computes the pressure and temperature values, removing the temperature-sensitive battery from the measurement chain and eliminating its source of error.
Solution Approach 2:
The patent replaces the battery-powered active transmission system with a passive impedance modulation system. The sensor's antenna circuit impedance changes in response to pressure and temperature, and these changes are detected by the external interrogator, eliminating temperature-dependent battery voltage variations from the measurement process.
4Use of energy by moving object
If conventional wireless sensors with batteries are used, then data transmission capability is achieved, but safety concerns arise for intrinsically safe operations
Solution Approach 1:
The patent extracts the power source from the wheel sensor, removing the battery and all active electronics that consume energy. The passive sensor requires no power consumption and cannot generate sparks or heat, making it inherently safe for intrinsically safe environments such as petrochemical facilities.
Solution Approach 2:
The passive sensor design eliminates all energy-consuming components, creating a truly passive device that draws minimal energy from the interrogator's electromagnetic field. This passive operation ensures the sensor meets intrinsically safe requirements for use in hazardous environments.
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 solution provides a reliable, lightweight, and easy-to-install pressure and temperature sensing system resistant to shock and vibration, eliminating battery-related inaccuracies and enabling intrinsically safe operations, suitable for applications like tire pressure monitoring and industrial use.
Implementation Method 1
Surface acoustic wave (SAW) devices used as sensors in measurement systems are known
Implementation Method 2
SAW devices are resonators whose resonant frequency changes when strained
Implementation Method 3
pressure and temperature information is transmitted by radio frequencies from each sensor location
Data Source
AI summary
The SAW sensor in a stainless steel button package having a diaphragm and mounted on a threaded port. Package can hermetically seal a sensor and RFID-antenna assemblies from media. Sensor diaphragm is exposable to media. Sensor and RFID antennas communicate electrically with SAW sensor and RFID device, respectively, for sensor measurements and identification. Antennas receive RF interrogation signal from a nearby interrogator/transceiver and send reflected RF signals back to the interrogator unit containing sensor measurement and sensor ID. TRF signal excites a SAW resonator inside the sensor and causes the SAW to resonate wherein resonant frequency changes with pressure and temperature applied to the sensor. Antennas could be printed circuit board antennas, helical antennas, loop antennas, any other commercially available off-the-shelf antennas or a combination of these.