Hydraulic Character Modeling and Vehicle Stability Control Algorithm for EHB System of Passenger Car 2016-01-0454
As a new braking system, EHB can significantly improve the braking performance and vehicle handling and stability. In this paper the structure of high-speed on-off valve and the valve core principle are discussed, the paper also analysis the response of the valve core under different modulation frequency, duty cycle and the change of wheel cylinder pressure. Set a proper modulation frequency to make sure that electromagnetic valve can be worked in a greater linear range. While modeling, the response time will be incorporated into the electromagnetic valve opening or closing time, through the simulation analysis of restricting the duty cycle of electromagnetic valve or not, in the spool in a certain relative displacement standard conditions, the electromagnetic valve duty cycle may not be restricted due to the spool in a certain relative displacement to amend the solenoid valve lag time because of simplifying the process of modeling electromagnetic with neglecting lag time to ensure that the duty cycle of solenoid valve is set under the conditions of not work in their death or saturation region. Based on vehicle dynamic stability control theory, a control strategies and algorithms were established combined with structural characteristics of EHB hydraulic system. Reference to vehicle linear model with vehicle model, an additional vehicle yaw torque is decided by comparing vehicle actual state to normal one. By translating to the torque into the corresponding additional wheel brake pressure, wheel cylinder pressure is controlled in closed-loop from getting pressure sensor information which provided by pressure sensor in wheel cylinder.