| With the energy and environmental issues become increasingly prominent, study onhybrid cars in the automotive industry is deepening and the various problems continue toappear, the contradiction between the maximum recovery of braking energy and maintenanceof the good brake pedal feel exists in the study of the hydraulic brake control system. This ismainly reflected that in order to take fully use of the motor for regenerative braking in lightbraking intensity, the braking force could be completely provided by the motor without theneed of generating braking friction, in which condition the brake pedal feel will be affectedwith the traditional brake control system. The most traditional car is equipped with hydraulicbrake control system along with vacuum booster, further studies of its various componentparts which will be applied in hybrid cars need to be conducted so that the regenerativebraking function can be perfected. A hydraulic brake control system including vacuumbooster with better regenerative braking performance is presented in this paper, and then astudy focused on its key components--the structure of the active vacuum booster device andcontrol algorithm has been conducted, more braking energy has been recycled.The main work of this paper is as follows:1. Through searching relevant papers and with the help of our group members, a type ofhydraulic brake control system with active vacuum booster has been proposed in order toimprove braking energy regenerating performance, especially a unique structure of activevacuum booster has been designed, which the vacuum degree can be adjusted real-time, andso to the adjustment of the wheel cylinder pressure in conjunction with the ABS hydraulicmodulator unit. The motor regenerative braking can be fully utilized without affecting thebrake pedal feel, which is mainly reflected in the smaller braking condition and motorregenerative braking force is gradually withdrawing from the situation.2. As to the designation of the structure of active vacuum booster, according to thevehicle parameters, the internal key parameters has been calculated and matched in detail, and being corrected with the national standard of GB7258-2004.3. With the rich component library of AMESim, the simulation models of the activevacuum booster components has been established according to the physical relationsbetween them, such as counter-disk model, forward-rear room model, middle diaphragmmodel, vacuum pump model, vacuum valve model, ABS hydraulic modulator unit model,the motor and battery model, vehicle model. Forwardly, the parameters of related gas, liquid,and brake lines (hard and soft tube) has been set in detail, so the simulating progress andresults can be more close to reality.4. In this paper, the active vacuum booster vacuum is under the closed-loop controlbased on MATLAB/Simulink fuzzy PD controller, which is simulated together with vehiclehydraulic brake control system model built with AMESim software, two main aspectsincluded as followed: First, the simulation of servo characteristics including emergencybraking condition of active vacuum booster. Second, the simulation of regenerative brakingfunction achieved by active vacuum booster in conjunction with the ABS hydraulicmodulator unit, in other words, no friction brake force on both front and rear axles undersmall intensity brake, and regulating friction brake force on front axle with the help ofhydraulic modulator unit in order to cope with the dynamic simulation of electric mechanism.At the same time, the function of initiative pressurizing has been achieved by the activevacuum booster in conjunction with hydraulic modulator unit, to some extent, the realizationof the active vacuum booster structure and function studied in this paper has been verified. |
PDF Full Text Request