DEVELOPMENT OF A MATHEMATICAL MODEL TO ESTIMATE THE TEMPERATURE OF REAR BRAKE DISC FOR AN EPB SYSTEM

摘要

A vehicle equipped with MoC system is prevented from rolling using friction force between brake pad and disc when parking. While a vehicle is driving, the brake system operates a lot of times for deceleration. When a driver hits brake pedal, the brake pad is moved toward the brake disc by hydraulic pressure from master cylinder. While brake pad is in contact with brake disc, the friction force between brake pad and disc is converted to heat energy. The generated heat raises the temperature and expands the volume of brake disc. The absorbed heat in the disc is transferred to other parts or ambient by conduction, convection and radiation. The removed heat makes the temperature of disc falls down and the volume shrinks. As volume change makes a gap between brake pad and disc, the clamping force of brake pad would become lower. If the vehicle is on a hill, it may experience rolling due to the slope. In this study, a mathematical model to estimate disc temperature is created using Matlab/Simulink. The mathematical model is divided into two parts, disc heating and cooling. The friction energy while braking and the amount of heat input is calculated using brake pressure and vehicle velocity. The disc is cooled down by convection while the vehicle is driving. When the vehicle is parking, most of heat is removed to air by conduction and radiation. The phenomenon of heat output is defined by vehicle velocity. A dynamo experiment is set up for validation of the developed mathematical model. The wheel is rolling at a constant angular velocity and wheel pressure is applied for various seconds to raise the disc temperature. The experiment is carried out under 5 conditions. The temperature is raised up to 100 ～ 500°C and cooled down to ambient temperature. In addition, a real driving condition is also applied. The vehicle runs at various velocities and brake pressure is applied to calliper. The same simulation condition is applied to the experiment and the disc temperature is measured using thermo-couple. The estimated result is very similar compared to experiment result. Therefore, it is concluded that the developed mathematical model can be reliable.