Prediction of Pressure Pulsation in Brake Line Considering Wave Propagation Characteristics of Fluid Contained in Flexible Hose for Automotive Hydraulic Brake System

Brake pulsation noise caused by fluid-borne vibration, which is generated by pressure pulsations from the pump in the Electronic Stability Control (ESC) modulator, occurs when the control brake function is activated under various driving conditions, such as Adaptive Cruise Control (ACC) and regenerative-friction brake coordination. This noise is particularly noticeable in Battery Electric Vehicles (BEVs), where the background noise from the power source is lower than that of internal combustion engine vehicles. The simulation of pressure pulsations in the brake system requires the excitation force of the pump built into the ESC modulator, the characteristics of valves, and the characteristics of the flexible hose; however, it is extremely difficult to determine these parameters with high accuracy from the design specifications. For this reason, in this study, the pump and valves were experimentally identified, while the flexible hose was represented by a three-element Voigt model to describe its viscoelastic properties. The pressure pulsation prediction model of the brake line was constructed by formulating the characteristics of all hydraulic components using four-pole matrix equations consisting of pressure, flow rate, and impedance, along with the continuity equation. This paper describes the method for creating a prediction model of pressure pulsation, the measurement results of the transfer matrix of the flexible hose, the modeling and parameter identification method of the flexible hose, and the accuracy verification results from a bench test of a brake system equivalent to an actual vehicle. Since a high-accuracy prediction model has been constructed, by predicting the pressure pulsation at any position in the brake line for any pump rotation speed, it can be utilized for designing the pump rotation speed that achieves both braking performance and brake pulsation noise reduction, and for examining bending and clamp positions of the brake line that avoid the amplification of excitation force.