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For the braking performance investigated when vehicle was on the road of different road adhesion coefficient, the match of ideal braking force distribution curves of front and rear wheels and front and rear arresters was studied. The concept of braking performance to reflect "braking force utilization" was introduced.The braking force utilization algorithm came out depending on the different matches. A light bus was chosen as an example. Vehicle braking performance under different road adhesion coefficient was studied in detail.At the same time, vehicle braking performance under different matches was studied with braking force distribution value changed. The results indicate that, braking force utilization appears first increased and then decreased with the increase of road adhesion coefficient.Along with the increase of braking force distribution value,the braking force utilization decreased on low adhesion coefficient road,then increased on high adhesion coefficient road.The method could evaluate the braking performance on the road of different road adhesion coefficient efficiently.

Auxiliary brake sets had been widely used for heavy duty trucks and advanced buses. They played a role of split-flow braking load of main brake system. As one of auxiliary brake sets eddy current retarder had good braking performance and braking stability, and it is automotive and maintain constant speed by its continual braking. In this paper, key technologies of eddy current retarder, such as braking torque, working volt and current, magnetic circuit, material of rotor plate and iron, heat dissipation performance of rotor plate, match between eddy current retarded and automobile, and effect of temperature rise on its braking performance were presented and discussed in detail. Meanwhile, advantage and disadvantage of eddy current retarder were analyzed.

On the basis of analyzing the structure and working principle of MRF brake, braking torque calculation formula of two disc MRF brake is established. Dynamic yield stress changing with the applied magnetic field is analyzed. Braking torque generated by MRF’s viscous changing with disk rotation velocity is also analyzed when magnetic field is zero. Furthermore; braking torque changing with magnetic field intensity is analyzed under a certain rotation velocity. The study provides a theoretical basis for MRF design.

Eddy current retarder was a retarder braking set used in an automobile, and it can transform kinetic energy or mechanical energy of the automobile into heat energy, and heat energy was emitted around environment by the blades founded in the rotor of eddy current retarder, so flow field within the blade had direct effect on heat elimination and braking performance. In this paper two styles of 2D computational model for the rotor had been established. The flow field between and out of blades were analyzed by using RNG Κ-ε model and energy equation. The velocity distribution, pressure distribution between blades, static pressure on work face and rear face of the blade along radial direction all were accepted. The pressure, velocity and air flux for two styles of the blades had been compared. Numerical analysis of flow field was in favor of improved structure design for the blade.

According to structure of disk MRF brake computational model of inner flow field for MRF was set up at simplified condition when MRF was regarded as Bingham model. Velocity distribution in inner flow field had been analyzed at different brake velocities and magnetic intensity using finite volume method (FVM), and brake torque and power had also been received at the same condition by integral method. Numerical analysis data were compared with theoretical data. Result showed that velocity distribution of inner flow field was not linear at axial direction, and that brake torque of disk MRF brake was constant approximately, and that numerical data and theoretic data were identical and it can provide reference for design.

Design of magnetic circuit is the key for disk MRF brake and has an important effect on brake torque per unit mass. In this paper structure and working principle of disk MRF brake are introduced, and magnetic circuit is designed by using engineering magnetic field method, and main technologies are introduced in detail, and its magnetic field is analyzed based on finite element method. This is benefit for structure optimization of the magnetic circuit. The feather of the magnetic circuit is received by numerical analysis method, and magnetic saturation and leakage phenomenon are found at the circuit, and these problems should be paid attention especially.