Application of PID control to an electro-pneumatic brake system

One of the most important systems that ensure the safe operation of vehicles traveling on roadways is the brake system. Most commercial vehicles such as buses and trucks are equipped with an air brake that uses compressed air as the energy transmitting medium. The conventional air brake has a significant time lag that affects its performance. An electro-pneumatic brake system uses an electric signal to modulate the air pressure in the brake system and it has been shown to significantly reduce the time lag associated with the conventional air brake system. This paper deals with the application of a PID controller for regulating the air pressure in an electro-pneumatic brake. An approximate first order linear model including time lag is proposed to predict the pressure transients in the brake system. The transfer function of the time lag is then approximated and used to design various controllers such as proportional, proportional-integral and proportional-integral-derivative controllers. These controllers are implemented on the experimental setup and their performances are compared.