Tire-road Friction Coefficient Research Articles

A Study on Overtaking Behavior on the Slippery Road

Overtaking behavior on two-lane and slippery road becomes more difficult because tire-road friction coefficient drops. In this study, overtaking behavior model considering slippery roads is developed and analysis of overtaking behavior is conducted. That is, by developing passing sight distance estimation model and aborting model, analysis of overtaking and aborting behavior on slippery road is conducted. As a result, the following facts are clarified. The length of overtaken vehicle, overtaking vehicle's speed and road conditions affect passing sight distance. The overtaking vehicle's speed and road conditions affect aborting behavior.

Estimation of Tire-Road Friction Using Observer Based Identifiers

This paper presents methods for identifying the tire-road friction coefficient. The proposed methods are: an observer-based least square method and an observer/filtered-regressor-based method. These methods were designed assuming that some of the states are not available since physical parameter identification methods developed assuming that the system states are available are not attractive from a practical point of view. The observer is used to estimate signals which are difficult or expensive to measure. Using the estimated states of the system and the filtered-regressor, the parameter estimates are obtained. The proposed methods are evaluated on an eight state nonlinear vehicle/transmission simulation model with a Bakker-Pacejka's formula tire model. Vehicle tests have been performed on dry and wet roads to verify the performance of the methods. It has been shown through simulations and vehicle tests how the RPM sensors can be used with observer based identification methods to estimate the tire-road friction from measurements of engine rpm, transmission output speed and wheel speed. The proposed methods will be useful in the implementation and adaptation of vehicle collision warning/avoidance algorithm since the tire-road friction can be estimated only using the RPM sensors which are currently being used in production vehicles.

Algorithms for a Vehicle Dynamics Monitoring System, Based on Model Reference Structure

Vehicle control depends heavily on the knowledge of the vehicle operatingconditions. One of the most important parameters for its control is thetyre–road friction coefficient (µ). An appropriate way toestimate the vehicle operating conditions is the Model Reference Approach.This technique requires a model that provides estimated states which can becompared with the measured states, the difference is used to determine thereal operating conditions. This paper presents two different applications ofthe Model Reference Techniques to estimate tyre–road frictioncoefficient; these are based on the relation between tyre forces and slip,and on the vehicle lateral behaviour using an extended Kalman filter.Experimental data from the test vehicle confirms the good results obtainedin the friction estimation based on the tyre slip–force relation. Theestimation using an extended Kalman filter on lateral behaviour showsaccurate tracking. The next step to be taken is to integrate all thealgorithms in the test vehicle and to validate them for a wide range ofoperating conditions, in order to have reliable information for the activesystem control.

Determination of Tire-Road Friction Coefficients for Skid Mark Analysis

Abstract An experimental study was made to compare the validities of methods currently used by accident reconstructionists to determine the coefficient of friction between the road and the vehicle tires at the time of an incident. This value could then be used in conjunction with skid mark length and vehicle weight to calculate the prebraking speed of the vehicle. Three automobiles and three trucks with a variety of tires and loadings were used on a variety of pavements. The accuracy and area of applicability of each of four methods for obtaining friction coefficients were determined by relating the prebraking speed calculated from each to the actual speed at the time of brake application. All four methods were satisfactory for automobiles and the pickup truck used, but only two were acceptable for heavy trucks. The most valid coefficients are obtained from skid mark lengths obtained under conditions duplicating those in an incident.

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The paper proposes an integrated adaptive coordination technique for active front steering (AFS) and direct yaw moment control (DYC). The main contribution is to present an integrated multi-input multi-output (MIMO) adaptive control method to manage the variations of vehicle mass and tire-road friction coefficient as parameter uncertainties. The proposed integrated control strategy encompasses two: upper and lower control layers. At the upper control layer, there is a model reference adaptive controller responsible for generating additive steering angle and corrective yaw moment. The coordination between AFS and DYC is realized using a gain scheduling mechanism based on a stability index. At the lower control layer, the desired yaw moment is converted to the brake torque before being applied to the rear wheels. Three critical and important high-speed lane-change maneuvers are considered. The simulation results confirm that the proposed control structure can reduce the sideslip angle and lateral acceleration. Furthermore, the system tracking performance in terms of handling and stability in different maneuvers is improved.