Vehicle Wheel Torque Perturbation for Road Friction Estimation
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Solution Overview
Problem
Current methods for determining road surface characteristics, such as friction coefficients, are not optimal in all situations, particularly when a braking or stability event has not occurred, making it difficult to set desired vehicle distances in cruise control or non-cruise control driving.
Innovation Solution
A method and system that apply torque to vehicle wheels, measure wheel slip, and estimate road surface characteristics using a processor and sensors to determine the road's coefficient of friction, allowing for proactive assessment of road conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If road surface characteristics are determined only during braking or stability events, then measurement simplicity is maintained, but road characteristic estimation is unavailable during normal driving conditions
Solution Approach 1:
The system performs preliminary road surface characteristic estimation by applying small torque perturbations to the wheels during normal driving conditions, before any braking or stability event occurs. This allows the vehicle control system to have road friction data readily available when needed, rather than waiting for specific events to trigger measurements.
Solution Approach 2:
The system uses the vehicle's existing wheel torque application during normal acceleration and deceleration maneuvers to generate the necessary wheel slip for road characteristic estimation. Instead of requiring separate dedicated measurement events, the system leverages ordinary driving operations to continuously estimate road surface properties.
2Loss of information
If torque is applied to wheels to measure wheel slip for road characteristic estimation, then road surface characteristics can be determined during normal driving, but additional energy consumption occurs
Solution Approach 1:
The system applies only small, partial torque perturbations to the wheels just sufficient to generate measurable wheel slip for road characteristic estimation. These small torque applications are much smaller than full braking or acceleration events, minimizing energy consumption while still obtaining accurate road friction data.
Solution Approach 2:
The system continuously estimates road surface characteristics during normal driving operations, eliminating the need for separate dedicated measurement events. By integrating road characteristic estimation into ongoing driving maneuvers, the system avoids the energy cost of stopping and restarting measurement processes.
3Measurement precision
If wheel slip is measured to estimate road surface characteristics, then accurate friction coefficients can be obtained, but vehicle control complexity increases
Solution Approach 1:
The system uses existing vehicle sensors (wheel speed sensors, torque sensors) and processors that serve multiple functions including normal vehicle control, to also perform road surface characteristic estimation. This multi-functional approach obtains accurate friction coefficients without adding dedicated complex measurement hardware.
Solution Approach 2:
The system uses feedback from existing vehicle sensors that monitor wheel speed, torque, and slip to continuously estimate road surface characteristics. This feedback mechanism leverages data already being collected for vehicle control, achieving precise friction measurement without requiring separate complex sensing 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
Enables accurate and proactive estimation of road surface characteristics, improving vehicle control and safety by providing reliable data for vehicle spacing and stability even in non-emergency situations.
Implementation Method 1
determining a wheel slip for the one or more wheels... estimating the characteristic of the surface of the road based at least in part on the wheel slip and the torque
Data Source
AI summary
Methods and systems are provided for estimating a characteristic of a surface of a road on which a vehicle is travelling is provided. The system comprises a sensor and a processor. The sensor is configured to measure information pertaining to a wheel slip for one or more wheels of the vehicle after a torque is applied. The processor is coupled to the sensor, and is configured to at least facilitate applying the torque for the one or more wheels of the vehicle, and estimating the characteristic of the surface of the road based at least in part on the wheel slip after the torque is applied and the torque.