Wireless SAW Sensor for Traction Battery Pressure Monitoring
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Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) of traction batteries in vehicles, such as using open circuit voltage (OCV), are limited by requiring the battery to be at rest and have low accuracy due to small voltage changes during operation, especially in the 30% to 50% SOC range.
Innovation Solution
Incorporating a temperature-compensated passive wireless surface acoustic wave (SAW) sensor within the traction battery to measure pressure changes caused by lithium ion movement, allowing for real-time, in-situ monitoring of forces and improved SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open circuit voltage (OCV) method is used to estimate SOC, then the measurement is simple, but the accuracy is low due to small voltage changes during operation
Solution Approach 1:
The patent replaces the electrical voltage measurement system with a mechanical pressure sensing system. Surface acoustic wave (SAW) sensors detect mechanical pressure changes caused by lithium ion movement and electrode expansion/contraction, converting mechanical effects into measurable signals for SOC estimation, thereby achieving higher accuracy through a different physical domain.
Solution Approach 2:
The patent changes the measurement parameter from electrical voltage to mechanical pressure. By monitoring pressure variations within the battery caused by lithium ion insertion/extraction and electrode volume changes, the system achieves more sensitive and accurate SOC detection, especially in the 30-50% SOC range where voltage changes are minimal.
2Productivity
If OCV method is used, then the system is simple to operate, but it requires the battery to be at rest and cannot provide real-time monitoring during operation
Solution Approach 1:
The patent replaces the static electrical voltage measurement with a dynamic mechanical pressure measurement system. The SAW sensor continuously monitors pressure changes during battery operation, capturing real-time SOC information without requiring the battery to be at rest, thereby enabling productivity improvement while maintaining reliability.
Solution Approach 2:
The patent employs temperature compensation mechanisms that pre-calculate and adjust for thermal effects on pressure measurements. By anticipating and compensating for temperature variations before they affect measurement accuracy, the system maintains reliable SOC estimation during dynamic operation across varying thermal conditions.
3Measurement precision
If pressure sensing is implemented to improve SOC estimation accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent uses surface acoustic wave (SAW) technology, which is aĉç (mature) and compact solution for pressure sensing. The SAW sensor integrates the pressure-sensitive element with the signal processing functionality in a single chip, reducing overall device complexity while maintaining high measurement precision for SOC estimation.
Solution Approach 2:
The patent changes the measurement parameter to pressure, which provides more sensitive detection of lithium ion movement. This parameter change enables accurate SOC estimation with a simpler sensor configuration compared to attempting to improve voltage measurement precision through complex electrical sensing arrangements.
4Reliability
If temperature compensation is added to the SAW sensor, then measurement reliability improves under varying temperatures, but device complexity increases
Solution Approach 1:
The patent merges the temperature compensation functionality directly into the SAW sensor structure. The SAW sensor inherently provides temperature compensation through its design, where the acoustic wave propagation characteristics are used to simultaneously detect both pressure and temperature, eliminating the need for separate compensation components and reducing overall device complexity.
Solution Approach 2:
The SAW sensor serves multiple functions: it detects pressure changes for SOC estimation and simultaneously provides temperature compensation. This multi-functionality approach improves measurement reliability under varying temperatures without requiring additional dedicated temperature sensing or compensation mechanisms, thereby avoiding increased device complexity.
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 SAW sensor provides accurate SOC estimation even during battery operation, overcoming the limitations of traditional OCV methods by measuring pressure changes associated with lithium ion expansion/contraction, enhancing accuracy and reliability.
Implementation Method 1
A traction battery of a vehicle includes a temperature compensated passive wireless surface acoustic wave sensor within the traction battery
Implementation Method 2
measuring forces or pressure within the battery using a surface acoustic wave (SAW) sensor
Data Source
AI summary
A traction battery of a vehicle includes a temperature compensated passive wireless surface acoustic wave sensor within the traction battery and a controller. The temperature compensated passive wireless surface acoustic wave sensor is configured to receive a broadcast signal and transmit a reflected signal. The controller is programmed to transmit the broadcast signal and receive the reflected signal, and based on a difference in phase and amplitude between the broadcast and reflected signals indicative of an increase in pressure within the traction battery, stop charging the traction battery.