Study On Identification Method Of Road Adhesion Coefficient Based On The Energy Theory

With the rapid development of the automotive industry, traffic accidents also haveincreased by motor vehicles. to reduce accidents, the vehicle active safety controltechnology has rapidly developedt in recent years and gradually be applied in the vehicles.To a large extent, the vehicle active safety control systems depend on the tire adhesion,however, road adhesion coefficient not only affects the vehicle’s acceleration performance,braking performance, but also affects the vehicle’s handling and stability performance. Thecar needs a good road adhesion to achieve high speed. Therefore, the car is always out ofcontrol due to the deterioration of the road adhesion because of weather and other factors.Indriving state, how to accurately get the vehicle status information especially the roadadhesion has become the primary solution to promote the vehicle safety control systems.The road adhesion coefficient mainly depends on road materials, road surfaceconditions, parameters of the tire structure and tire pressure, wheel radial load, vehiclespeed, working temperature and other factors. In most cases vehicle parameters such asquality, rotational inertia and tire pressure change with time. Therefore, the main factorsleading to changes of road adhesion coefficient is road conditions, rough, wet and muddy.Foreign scholars have conducted research in the field of road adhesion coefficientidentification for many years. They also have made substantial achievements by sensingtechnology, the model parameter estimation and a variety of data analysis methods toidentify the road conditions. This study aims on the energy transfer and consumption theoryto identify the road adhesion coefficient with vehicle status sensors duringbraking.According to the power equation, the study can achieve the purpose of real-timeestimation of road adhesion coefficient, which provides theoretical and technical support forthe active control of the vehicle.The braking performance is an important factor affecting the safety of the car driving.This article proposed a method to identify adhesion coefficient based on the energy theory,to solve the problems the precise model of the tire and vehicle dynamics modelbeingestablished to estimate the road adhesion coefficient. By analysing four differentbraking modes, the article only selected the friction brake working method, which is thedriver depresses the clutch pedal and brake pedal, thus four wheels come into braking torques. According to the power equation theory, the article deduced the calculation modelof road adhesion coefficient, which applied to the friction brake only. To verify the validityof estimation in braking condition, simulation model was created by MATLAB/SIMULINK.Through the ABS effect, the adhesion coefficient stabilized at the peak, which fullyillustrated that the adhesion coefficient model is correct.Based on the model, the article has carried on the preliminary study of the roadadhesion coefficient identification system. This article developed an external independentwheel speed system and a real-time test system for vertical load testing. On thesefoundations, combined with the V-BOX II system, the road adhesion coefficientidentification test system was developed. In the standard road, the road adhesion coefficientidentification system was tested. The results showed that: The system can real-time detectthe peak of road adhesion coefficient in braking, thus the model of road adhesion coefficientis correct and can be used for real-time test of the road adhesion coefficient in vehiclerunning, providing a feasible approach for active safety control.