Vehicle Load Estimation via Sprung Mass Vibration
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Solution Overview
Problem
Existing methods for estimating a vehicle's loading condition, such as measuring tire deflection, are inaccurate due to factors like road conditions, sensor reliability, and environmental influences, necessitating an indirect measurement approach that uses commonly available vehicle parameters to minimize cost and complexity.
Innovation Solution
The system estimates vehicle tire load by measuring vibration resonant frequency peaks of the sprung mass using commercially available sensors, specifically chassis vertical acceleration and pitch rate, and employs a Kalman filter to generate a dynamic load estimation based on observed frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tire-mounted strain sensors are used to measure tire deflection, then loading condition can be detected, but accuracy deteriorates due to road conditions, sensor dependability, and operating conditions
Solution Approach 1:
The patent uses vibration sensors mounted on the vehicle chassis as an intermediary to indirectly measure loading conditions through sprung mass frequency analysis, rather than directly measuring tire deflection with strain sensors. This intermediary approach avoids the accuracy problems of direct tire-mounted measurement while still providing reliable load detection.
Solution Approach 2:
The patent replaces the mechanical strain sensor system on tires with a vibration-based measurement system using accelerometers and frequency analysis. This substitution transitions from direct mechanical measurement to indirect dynamic analysis, eliminating the harmful effects of road conditions and sensor reliability issues on measurement precision.
2Measurement precision
If tire-mounted load sensors are installed, then loading condition measurement is effective, but device complexity and cost increase
Solution Approach 1:
The patent makes the vibration measurement system universal by using sensors and signal processing methods that can detect multiple loading conditions (empty, partial, full load) with a single integrated system. The same vibration sensors and frequency analysis methodology work across different vehicle types and loading scenarios, reducing overall system complexity.
Solution Approach 2:
The system uses the vehicle's own existing vibration characteristics and commonly available sensor data to determine loading conditions, rather than requiring external specialized sensors. The vehicle's natural vibration response serves as the measurement signal, and the processing uses standard signal analysis techniques already present in modern vehicles.
3Device complexity
If indirect measurement methodology is used, then cost and complexity are minimized, but measurement accuracy may be compromised
Solution Approach 1:
The patent exploits mechanical vibration principles by measuring the natural frequency of the sprung mass, which changes predictably with loading conditions. This vibration-based indirect measurement provides high accuracy because the frequency-shift method is inherently sensitive to mass changes while using simple, low-cost vibration sensors and signal processing.
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
This method provides accurate load estimation without the need for tire-mounted sensors, achieving a high correlation between actual and estimated loads, and can be implemented without additional hardware costs, effectively adjusting stability/brake/traction control systems based on loading conditions.
Implementation Method 1
identifies a change in vehicle loading condition by measuring vibration resonant frequency peaks (bounce mode and/or pitch mode) of the sprung mass
Implementation Method 2
Signals required include the chassis vertical acceleration and/or chassis pitch rate obtained from commercially available sensors mounted to the vehicle
Data Source
AI summary
A system and method estimating a vehicle tire load identifies a change in vehicle loading condition by measuring vibration resonant frequency peaks (bounce mode and/or pitch mode) of the unsprung mass. Signals required include the chassis vertical acceleration and/or chassis pitch rate obtained from commercially available sensors mounted to the vehicle. An observer model receives the inertial signal(s) and generates a dynamic load estimation based upon observed frequency change in the sprung mass natural frequency.