The definition of maximum position of φ_x-s_x-diagrams to improve the electronic control braking system performance

The choice of thresholds of electronic control adjustment of braking systems is oriented at the maximum of φ_x - s_x-diagram. To specify the maximum position of φ_x - s_x-diagram its forms under different conditions should be known. The majority of the vehicle motion modes are determined by the side force. In different cases the lateral force can occur before or after the wheel brake moment. The purpose of the article is to investigate the sequence effect of side force occurrence and the braking torque on the wheel tire grip with a solid road surface and to study the maximum position of φ_x - s_x-diagram. The author has developed techniques to take into account the sequence of appearance of the side force and torque of the wheel when calculating φ_x - s_x-diagrams. The research is based on the hypothesis according to which the proportion of the coefficient of adhesion implemented by the static friction in the contact area in the presence of lateral force is dependent on the proportionality coefficient of static friction. The formulas for the calculation of coupling coefficients for different slide sequence take into account the successive emergence of lateral force and braking torque of the wheel. The formulas are universal and can be applied to all types of tyres, different kinds and conditions of road surface. The forms of φ_x - s_x-diagram were studied at different sequence of side force occurrence and torque of the wheel. The essential influence of lateral force occurrence sequence and the torque of the wheel on friction properties of static and sliding zones of the wheel tire contact with the road and the maximum position of φ_x - s_x-diagram has been established. If the lateral force was prior to the beginning of braking the car (braking at turn, side wind, etc.), the maximum decrease of the friction coefficient was reduced in the preserved horizontal sliding position. If the lateral force appeared after the beginning of vehicle braking (braking while turning, side wind, etc.) its increase will cause reduction of the maximum friction coefficient at sliding displacement to the left. It has been established that the growth of the lateral force value from zero to a weight value led to the peak change of φ_x - s_x-diagrams up to 66% in the direction of smaller sliding. The results obtained can be applied in the creation and implementation of the wheeled vehicle control algorithms in the electronic active safety systems in order to increase traffic safety.

vehicle, braking, electronic control of braking system, thresholds setting, interaction of the tyre with solid road surface, the sequence of appearance of the lateral force and the braking torque of the wheel, coupling coefficient, the proportionality coefficient of static friction, forms of φ_x - s_x-diagram, the maximum position of φ_x - s_x-diagram

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