Axle Load Estimation via Wheel Slip and Force Values
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Solution Overview
Problem
In truck-trailer combinations, accurately distributing brake torque among axles is challenging when axle load sensors fail, as existing methods rely on functional sensors to determine load distribution, and without sensors, alternative methods are needed to estimate axle loads effectively.
Innovation Solution
A method and device that estimate axle load distribution using secondary physical variables, such as wheel rotational speed changes caused by tire compression, which are detected by ABS sensors, and influence of torques and slippage, allowing for load determination through slip and force values, even without functional axle load sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If axle load sensors are used to detect load distribution, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical load sensors with a calculation-based system that uses existing ABS wheel speed sensors and vehicle dynamic models to estimate axle loads. This substitution eliminates the need for additional mechanical sensing equipment while maintaining load detection capability through mathematical relationships between wheel speeds and axle forces.
Solution Approach 2:
The system utilizes data already being collected by the ABS system (wheel rotational speeds) and combines it with vehicle parameters to self-determine axle load distribution. The existing sensor infrastructure serves dual purposes: both brake control and load estimation, eliminating the need for separate dedicated load sensors.
2Reliability
If axle load sensors are installed, then reliability of brake force distribution is improved, but ease of operation deteriorates due to increased maintenance requirements
Solution Approach 1:
The patent makes the ABS wheel speed sensors serve multiple functions: both their original function for brake control and the additional function of providing data for axle load estimation. This multi-functionality reduces the total number of sensors required and simplifies maintenance since only the existing ABS system needs to be maintained rather than additional dedicated load sensor systems.
3Device complexity
If secondary physical variables are used to estimate axle loads, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The system continuously monitors wheel rotational speeds and uses this feedback in real-time calculations to estimate axle loads. The calculation unit processes ongoing data from the ABS sensors, dynamically updating load estimates based on current vehicle operating conditions, which improves accuracy compared to static estimation methods.
Solution Approach 2:
The patent utilizes changes in wheel rotational speed parameters as indicators of axle load variations. By monitoring how wheel speeds change under different loading conditions and using these parameter variations to infer load distribution, the system achieves accurate estimation without requiring direct mechanical measurement of axle forces.
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
Enables accurate estimation of axle loads and effective brake force distribution, ensuring safe braking performance even when axle load sensors are malfunctioning or absent, by utilizing wheel speed ratios and slip stiffness calculations to determine dynamic loads and normal forces on axles.
Implementation Method 1
the load on the axle compresses the pneumatic tires of the wheels of the axle, an effective rolling radius of the wheels changes depending on the load
Implementation Method 2
an effective rolling radius of the wheels changes depending on the load. The changed rolling radius of a wheel is reflected in a changed rotational speed of the wheel
Implementation Method 3
the slip value represents a slip between the axle and another axle of the road train and the force value represents a driving or retarding force on the axle
Implementation Method 4
The rotational speed is additionally influenced by torques acting on the wheel or by slippage of the pneumatic tires caused by the torques
Data Source
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AI summary
The present invention relates to a method (400) for estimating an axle load distribution in a road train (100, 200), wherein the method (400) has a determining step (402) in which at least one load (122) acting on an axle (108) of the road train (100, 200) is determined using a slip value (126) and a force value (128), wherein the slip value (126) represents a slip between the axle (108) and a further axle (1/10) of the road train (100, 200), and the force value (128) represents a driving or decelerating force (118) at the axle (108).