Method for estimating longitudinal adhesion coefficient of road

Abstract

The invention discloses a method for estimating the longitudinal adhesion coefficient of a road. The method comprises the following steps: preliminarily estimating a longitudinal road adhesion coefficient in real time on the road surface of a flat expressway by using a recursive least squares (RLS) method with a forgetting factor specific to a front-wheel steering four-wheel automobile on the basis of an overall longitudinal dynamics model and a simplified magic formula tire model; further filtering signal noise by using an extended Kalman filter (EKF) algorithm by taking the estimated longitudinal road adhesion coefficient and a tire model parameter as expansion states, and realizing self-adaptive adjustment of a tire model coefficient; finally, acquiring accurate and robust longitudinal road adhesion coefficient estimation in real time. The method can adapt to working conditions of high slip rate and low slip rate of flat expressways at the same time.

Description

Technical field [0001] The invention relates to a road longitudinal adhesion coefficient estimation method. Its purpose is to use recursive least squares and extended Kalman filtering methods through vehicle longitudinal dynamics modeling and tire models to realize the Accurate and reliable estimation of the longitudinal road adhesion coefficient under the conditions of high slip rate and low slip rate. The vehicle longitudinal active safety system can adjust the control strategy according to the estimated longitudinal road adhesion coefficient, improve vehicle safety, and has high accuracy, It has significant advantages such as low cost, real-time and good adaptability, and belongs to the field of automotive active safety measurement and control. Background technique [0002] With the development of social economy, the problem of road traffic safety has become increasingly prominent and has become a global problem. Traffic accidents all over the world cause a large number of ca...

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Problems solved by technology

However, this method can only be applied to low slip rate conditions, and under high slip rate conditions, the assumption that the normalized traction force is proportional to the slip slope is no longer valid, so this method cannot be used to determine the road adhesion coefficient At the same time, there are some differences in the slip slope on the same road surface due to the influence of other factors, which brings certain difficulties to the identification of the adhesion coefficient

Another commonly used method is to use different forms of nonlinear formulas to fit the normalized traction force and slip ratio curves according to the measured data in real time, so as to estimate the adhesion coefficient according to the peak value of the fitted curve. Only under the condition of large tire slip ratio can the estimated result be closer to the real value

At the same time, this method uses a nonlinear function for fitting, which has a large amount of calculation and poor real-time performance. No matter which nonlinear function is used, it cannot match the tire characteristics under all working conditions, and the error is large.

It can be seen that the main problem in the estimation of the adhesion coefficient is that it is difficult to obtain good estimation results under the conditions of high slip rate and low slip rate at the same time, which limits its application in the longitudinal active safety system of automobiles.

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