The purpose of the thesis, is to develop a universal test bench for electro- pneumatic valves, used in commercial vehicles. The main points are the control software – to improve the previous, limited functionality test bench- and the clamping device for fast mechanical fixing, during the tests. The devices under test are electro- pneumatic valves, designed and manufactured by Knorr-Bremse Fékrendszerek Kft. These valves are parts of commercial vehicle braking and levelling systems.
I studied the structure of braking and levelling systems, operation, control, and filed of use of the electro- pneumatic valves. I examined the test specifications, the methods and the regulations of the endurance test. The core element of the test bench is a National Instruments CompactRIO system. I examined the architecture, and the possible ways of operation. Considering the resources, I decided, that instead of the complete operation mode (FPGA + processor), the simpler, more limited method will be used for development, where the FPGA bitfile cannot be modified. Before this decision, I made a mechanical model for the electro- pneumatic valves, to specify the sampling rate. I also examined the resolution of the control signal for the valves.
After doing the software specification, I started the software development in NI LabVIEW environment. The operation of the test bench is supervised by a PC. The CompactRIO controls the valves, and measures the properties of each switch. The PC stores these data, and provides user interface. The communication between these two components is a high priority task during the development. The duration of the endurance test is long (several weeks, or even months), therefore it is important, that no continuous supervision should be required for the measurement. In case of the failure of the PC, or the communication channel, the CompactRIO is capable of a temporary autonomous operation. After the optimization, I spent several weeks for testing the software during measurement. The final version of the software is currently used for real tests.
For the clamping device, I examined the specification, made several concepts for the components, then I ranked these concepts, and chose the best one. I made a D-FMEA analysis for the final concept, to eliminate the possible failures. I made the final 3D models, and the drawings of the custom parts, needed for manufacturing.