Simulation of pneumatics in brake systems

Abstract: Pneumatic brake systems use pressurized air to apply the brakes and are used in trucks, amongst other vehicles. Due to the compressibility of the air, there is a time delay from the push-down of the brake pedal to the attainment of the desired brake effect. The time for the pressure in the brake cylinder to reach 75% of its final pressure is subject to legal requirements, and this master thesis studies the possibilities to predict that time by simulation. The program GT-SUITE is chosen for the simulation, since it is shown to be suitable in a survey of potential software and an evaluation. Also, MATLAB is used to simulate an approximate system description. To support the modeling of brake system components, measurements are made on a simple brake rig, gradually extended with common brake components which then can be modeled. Finally, the models are verified with a measurement on a complete brake system. In the simple rigs, the simulations are accurate and able to predict the effect of new components. Verifying the models, though, the simulation is not accurate enough. However, the simulation seems to give conservative results, which means that a truck that in simulation passes the certification is likely to pass it in reality too.