Vehicle Control Device Friction Coefficient Estimation
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Solution Overview
Problem
Existing vehicle control systems, such as adaptive cruise control and collision mitigation brake systems, are ineffective in maintaining appropriate vehicle distance and controlling acceleration and deceleration when the friction coefficient between tires and the road surface is low, as on snowy or frozen roads, due to increased braking distance and reduced grip force.
Innovation Solution
A vehicle control device comprising a tire-side device with a vibration detection unit that estimates the friction coefficient and transmits data to a vehicle-side device, which then calculates the braking distance and adjusts acceleration and deceleration accordingly, using a transmitter, receiver, and signal processing units to communicate and control vehicle travel based on real-time road surface conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acceleration and deceleration control is based on the assumption of high friction coefficient (μ=0.8), then collision avoidance can be achieved under normal conditions, but the control becomes inappropriate when the friction coefficient is low (snow-covered roads, frozen roads, worn tires)
Solution Approach 1:
The system dynamically adjusts the friction coefficient assumption based on real-time detection of tire vibration characteristics. Instead of using a fixed high friction coefficient (μ=0.8), the system continuously monitors vibration signals from the tire and updates the friction coefficient value to match current road conditions, enabling adaptive control that maintains reliability across varying conditions.
Solution Approach 2:
The tire-side device autonomously detects friction coefficient information by analyzing tire vibration characteristics and transmits this data to the vehicle-side device. The system serves itself by using the tire's own vibration signals as the sensing mechanism, eliminating the need for separate road condition sensors.
2Measurement precision
If the friction coefficient is underestimated, then braking distance is overestimated and acceleration/deceleration timing is delayed, but if the friction coefficient is overestimated, then braking distance is underestimated and collision avoidance fails
Solution Approach 1:
The system uses mechanical vibration of the tire as the sensing mechanism. The vibration detection unit attached to the tire back side measures vibration characteristics that directly correlate with friction coefficient. This physical sensing method provides accurate real-time measurements without delays, enabling precise friction coefficient estimation that directly informs timing-critical acceleration and deceleration control.
3Measurement precision
If a vibration detection unit is attached to the tire to detect friction coefficient, then accurate road surface condition information can be obtained, but the device complexity increases
Solution Approach 1:
The system extracts friction coefficient information from the existing tire vibration signals that occur naturally during vehicle operation. Instead of adding complex sensing systems, it extracts useful information from the tire's own mechanical vibrations, which are already present due to road interactions. This extraction approach minimizes added complexity while achieving accurate road surface detection.
Solution Approach 2:
The vibration detection unit acts as an intermediary between the tire and the control system. It converts mechanical vibration characteristics into electrical signals that can be processed by the signal processing unit to determine friction coefficient. This intermediary component provides a simple bridge that translates physical tire behavior into usable control information without requiring complex direct measurement systems.
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 solution allows for more accurate control of vehicle acceleration and deceleration by estimating the braking distance based on the friction coefficient, ensuring safer inter-vehicle distances and preventing collisions by adjusting timing according to varying road conditions, even on low-friction surfaces.
Implementation Method 1
a vibration detection unit that is attached to a back side of a tread of a tire fitted to a tire wheel mounted on a vehicle and that outputs a detection signal corresponding to a magnitude of vibration of the tire
Data Source
AI summary
A vehicle control device including a tire-side device and a vehicle-side device is provided. The tire-side device includes a vibration detection unit that outputs a detection signal corresponding to a magnitude of vibration of a tire, a signal processing unit that generates μ data representing a friction coefficient between the tire and a road surface by processing the detection signal, and a transmitter that transmits the μ data. The vehicle-side device includes a receiver that receives the μ data and a travel control unit that estimates the friction coefficient based on the μ data, acquires a braking distance of the vehicle based on the friction coefficient, and controls acceleration and deceleration of the vehicle based on the braking distance.