Towing Hook Load Measurement via Resonance Frequency
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Solution Overview
Problem
Existing methods for measuring the applied load on towing hooks are inaccurate and prone to thermal and structural issues, particularly failing to detect smaller loads on rigid objects and towable accessories connected to vehicles.
Innovation Solution
A method involving imparting vibrations to the tow bar using an actuator and detecting the natural frequency harmonics with sensors to determine the applied load, allowing for accurate measurement of both positive and negative loads, even when the towing hook arrangement is not mounted to a vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure load on towing hook, then measurement capability is provided, but thermal drifting, electric drifting, and structural integrity problems occur
Solution Approach 1:
The patent replaces strain gauges (electrical sensing system) with a resonance frequency-based measurement system that uses mechanical vibration and acoustic sensors. The load is measured by detecting changes in the natural resonance frequency of the towing hook structure, eliminating the need for electrical strain gauges and their associated thermal and electric drifting problems.
Solution Approach 2:
The patent changes the measurement parameter from strain (electrical resistance change) to resonance frequency (mechanical vibration characteristic). By measuring the natural frequency of the towing hook structure and its harmonics, the system achieves load measurement without the reliability issues of strain gauges, as frequency measurements are not affected by thermal or electric drifting.
2Adaptability or versatility
If resonance force sensor is used as disclosed in Abnaki patent, then measurements on all forms of structural pre-stress are enabled, but the application to vehicles and measurement methodology is not disclosed
Solution Approach 1:
The towing hook structure itself serves as the sensing element. By exciting the towing hook with vibration and measuring its natural resonance frequency, the system uses the structure's own mechanical properties to detect load without requiring external force sensors or complex measurement equipment. The towing hook's mass and stiffness characteristics provide the measurement basis.
Solution Approach 2:
The resonance frequency measurement system can detect all forms of structural pre-stress (axial compression, tension, bending moments, torsion) by analyzing the towing hook's natural frequency and harmonics. This universal approach eliminates the need for separate sensors for different stress types, simplifying the implementation while maintaining versatility.
3Measurement precision
If vibration-based measurement is used, then accurate detection of small loads is achieved, but additional components (actuator and sensor) are required
Solution Approach 1:
The patent introduces a vibration source (actuator) and acoustic sensor as intermediaries to couple the load information to the measurement system. The actuator excites the towing hook structure, and the acoustic sensor detects the resulting resonance frequency, serving as mediators that enable precise measurement without requiring direct contact or complex instrumentation on the towing hook itself.
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 approach provides a cost-effective and precise method for detecting small loads applied to towing hooks and tow bar accessories, enabling reliable measurements before and after vehicle mounting, and accounting for torque and dampening effects.
Implementation Method 1
imparting a vibration to the tow bar and detects how the towing hook arrangement reacts to the imparted vibration
Implementation Method 2
detects the natural frequency harmonics with sensors
Implementation Method 3
detects how the towing hook arrangement reacts to the imparted vibration
Data Source
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AI summary
A method for measuring the applied load on a towing hook/or a tow bar accessory of a towing hook arrangement (10) for a vehicle, and a towing hook arrangement (10) for a vehicle. The towing hook arrangement (10) comprises a towing hook (12) and/or a tow bar accessory arranged on a tow bar (11), the towing hook arrangement (10) also comprises a sensor arrangement (20) having at least one actuator (21, 21') and at least one sensor (22, 22'), the sensor arrangement is adapted to detect an imparted vibration on the tow bar (11) and use the detected imparted vibration to determine the applied load on the towing hook (12) and/or the tow bar accessory.