WIM Sensor Calibration Using Measuring Wheel Force Data
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Solution Overview
Problem
Current WIM sensor calibration methods are complex, expensive, and require multiple traversals by a statically weighed truck, leading to inaccuracies due to random fluctuations and environmental factors, necessitating a more efficient and accurate calibration process.
Innovation Solution
A calibration method using a vehicle equipped with a measuring wheel to directly measure dynamic wheel forces, synchronizing these data with WIM signal data to determine a calibration function for quick and precise sensor calibration, allowing for single-traverse calibration and accounting for differences between dynamic and static loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple traversals by a statically weighed truck are performed for calibration, then statistical security against random fluctuations is improved, but the calibration process becomes more complex and time-consuming
Solution Approach 1:
The patent replaces the mechanical calibration system (statically weighed truck performing multiple traversals) with a direct measurement system using a measuring wheel that captures dynamic wheel forces in a single pass. The measuring wheel directly measures the force exerted by the vehicle wheel on the road surface, eliminating the need for multiple statistical measurements and complex data processing.
Solution Approach 2:
The calibration vehicle serves itself by equipping its own wheels with measuring wheels that directly measure the forces. This self-measurement capability eliminates the need for external static weighing infrastructure and multiple traversal requirements, allowing the system to perform calibration autonomously in a single pass.
2Measurement precision
If multiple traversals are performed for calibration, then accuracy is improved, but the time required for calibration increases
Solution Approach 1:
The measuring wheel is pre-equipped on the calibration vehicle before the calibration run. This preliminary preparation ensures that during the single traversal, all necessary force measurements are captured immediately and continuously, eliminating the need for repeated traversals to gather sufficient calibration data.
Solution Approach 2:
The measuring wheel continuously measures dynamic wheel forces throughout the single calibration traversal, capturing all necessary data in one uninterrupted pass. This continuous measurement approach replaces the discrete multiple-traversal method, maintaining accuracy while reducing total calibration time.
3Ease of operation
If dynamic loads are measured without direct wheel force measurement, then measurement simplicity is improved, but measurement accuracy deteriorates due to aerodynamics and spring condition variations
Solution Approach 1:
The measuring wheel acts as an intermediary device that directly contacts the road surface through the vehicle wheel, measuring the actual force exerted on the road. This intermediary measurement approach captures the true dynamic wheel force while accounting for aerodynamic and suspension effects, providing accurate calibration data without requiring complex corrections.
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 simplifies and accelerates the calibration process, reducing costs and increasing accuracy, often requiring only one measurement, while also assessing road quality for improved measurement reliability.
Implementation Method 1
the dynamic wheel force on the road and on the WIM sensor is measured directly on the measuring wheel
Implementation Method 2
Typical WIM systems include two inductive loops for vehicle classification and two rows of WIM sensors installed approximately 4m apart in a roadway
Data Source
Figure 1~2(d)
AI summary
The invention relates to a method for calibrating a WIM (Weigh In Motion) sensor (2) built into a road (1), the sensor being suitable for determining the dynamic and/or static weight of a vehicle (3) as it is passing over the WIM sensor (2). According to the invention, a calibrating vehicle (3) that is fitted with at least one measuring wheel (4) passes over the WIM sensor (2). During travel, the dynamic wheel force (5) on the road (1) and on the WIM sensor (2) is measured dependent on time or location directly at said measuring wheel (4) and conveyed to an evaluating unit (7). In addition, at the same time WIM signal data (6) are measured at the WIM sensor (2) and also conveyed to the evaluating unit (7). The wheel force data (5) is synchronised with the WIM signal data (6) and on the basis of a comparison of the wheel force data (5) with the WIM signal data (6), a calibrating function (8) is determined, which is used for calibrating the WIM sensor (2).