Wheel Oscillation Road Friction Detection Without Resonance Discomfort
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Solution Overview
Problem
Existing road-surface condition evaluation apparatuses face challenges in accurately assessing road conditions, particularly on low-friction surfaces, and may cause discomfort to vehicle occupants due to reliance on natural resonant oscillations.
Innovation Solution
An evaluation apparatus that actively induces oscillations in vehicle wheels using a specific frequency different from natural resonant frequencies, allowing for accurate road surface condition evaluation by comparing predicted and actual oscillation attenuation rates to determine low- or high-friction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If natural resonant oscillation is used for road surface evaluation, then the evaluation can be performed without active intervention, but the measurement precision is insufficient and causes occupant discomfort
Solution Approach 1:
The patent applies mechanical vibration by actively oscillating the wheel at a specific frequency to induce measurable responses from the road surface. The oscillation unit generates controlled vibrations that interact with the road surface friction characteristics, allowing precise evaluation of road conditions through the resulting oscillation attenuation, while avoiding natural resonant frequencies that cause occupant discomfort.
Solution Approach 2:
The patent changes the oscillation frequency parameter from natural resonant frequencies to specific frequencies that optimize both measurement precision and comfort. By selecting frequencies below resonant frequencies (e.g., 0.5-5 Hz), the system achieves accurate road surface evaluation without inducing uncomfortable vibrations in the vehicle body, thus resolving the contradiction between measurement quality and occupant comfort.
2Measurement precision
If active oscillation is applied to the wheel, then road surface evaluation accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by utilizing existing vehicle components (motor controller, wheel, sensors) for the road surface evaluation function. The oscillation unit leverages the motor controller's existing capability to regulate motor output, and the oscillation obtainer uses existing wheel speed sensors, thereby improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The system performs self-service by using the vehicle's own motion and existing control systems to generate the oscillation signals needed for evaluation. The motor controller that normally regulates motor output is also used to generate controlled oscillations, and the wheel's natural rotation provides the basis for measuring oscillation attenuation, eliminating the need for separate dedicated hardware.
3Object-affected harmful factors
If oscillation frequency is set below resonant frequency, then occupant comfort is improved, but the signal attenuation becomes less pronounced
Solution Approach 1:
The patent employs feedback by continuously monitoring the wheel oscillation response and comparing it with predicted oscillation based on the oscillation command. The evaluation unit calculates both the first attenuation rate (actual) and second attenuation rate (predicted), using this feedback loop to accurately determine road surface friction conditions even with smaller attenuation signals at lower frequencies.
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 enhances road surface condition assessment accuracy and reduces occupant discomfort by using controlled oscillations, enabling more precise friction condition determination and stable vehicle travel.
Implementation Method 1
a wheel resonant system includes a vehicle body, a road surface and at least a wheel
Implementation Method 2
calculate a first attenuation rate of a waveform of an oscillation obtained by the oscillation obtainer, and a second attenuation rate of a reference waveform
Implementation Method 3
a coefficient of friction between each wheel and the frozen road surface becomes extremely lower
Implementation Method 4
an oscillation of a rotational speed of each wheel based on the oscillation command for each target road surface is more likely to decay as a friction coefficient of the corresponding target road surface becomes smaller
Data Source
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AI summary
An evaluation apparatus (10) for evaluating a condition of a road surface on which a vehicle (100) is traveling includes an oscillation unit (11) configured to output an oscillation command that causes at least one wheel of the vehicle to oscillate, and an oscillation obtainer (12) configured to obtain an oscillation of rotation of the at least one wheel in response to the output of the oscillation command. The evaluation apparatus includes an evaluation unit (13) configured to perform an evaluation of the condition of the road surface in accordance with the oscillation command and the oscillation obtained by the oscillation obtainer.