Pressure Control of a Pneumatic Actuator Using On/O Solenoid Valves

Abstract: Nowadays a very important aspect in heavy duty vehicles is the braking system. The braking system can be divided into EBS brakes, exhaust brake and retarder, where the latter is of interest in the present Master's Thesis. This thesis presents an investigation whether it is possible to substitute today's concept, i.e. controlling the air pressure to the retarder using a proportional-valve, with two so-called on/o®-valves and a pressure sensor, which will reduce expenses and contingently hysteresis phenomena seen in the current system. A non-linear model of the Electronic Control Unit (ECU) electrical drives, and the electrical, magnetic, mechanical, and pneumatic parts of the valves, is designed. A Proportional-Integral-Derivative (PID)-controller is designed based on the derived model. Two di®erent pulsing schemes have been investigated. However, just one of the approaches together with the results from the other one is presented in this thesis. In order to improve the control performance non-linear control and prediction methods are used so that required time response and robustness is achieved. Finally the modelled current and pressure are validated against the measured data, and a verification of the controller is done on the prototypes.