Research On ARM-based Digital Controller Of Fatigue Testing Machine

In order to improve the performance of original analog controller, this paper studied fatigue testing machine for catenary, thanks to the advantage of digital control and the development of modern control theory. According to the characteristic of fatigue testing machine, the digital control algorithm was presented and implemented in an example testing machine. Due to user's requirements, the digital controller had accomplished controllable processes followed given rules.The research achievement on application of the digital controller of fatigue testing Machine at home and abroad was roughly described by a lot of documents, and according to the needs of the project, the main subjects are drafted.This paper presented the work conditions of the testing machine. It was studied that the plant model of position and force system about valve control unsymmetrical hydraulic ram. Then it was analyzed that static error was caused by unsymmetrical hydraulic ram. For digital control application, the continue model was transformed to discrete one. Then, simulations about position and force system were done for choosing right control strategy. A digital PID controller was designed to the closed-loop system. And on this basis, using dynamic pressure feedback to improve system performance, the results proved that dynamic pressure feedback could perfectly improve the damper.According to the needs of testing machine, the paper discussed a hardware architecture of control system which was based on AT91RM9200(ARM) as controller's CPU, S1D13506 as LCD controller to realize the graphical user interface, and 16-bit AD7825, DA7644 to complete the Analog input and output data conversion in view of the need of signal acquisition.Based on the hardware platform, the transplant of the embedded software platform of U-boot and Linux Operating were investigated. The drivers and application software of several interfaces, including the A/D and D/A converter,LCD module were programmed. Because Linux is not real-time system, Xenomai module had been used by embedded linux system to realize the real-time processing function, The transplant of MiniGUI software ensured the smooth development in system graphics user interface. On the basis of the above , The application of Fatigue testing machine control system is developed by MiniGUI.Finally, author implemented the control algorithm in a digital controller for fatigue testing machine system. Control algorithms and digital controller were proven to be available and realizable. The choices of hardware and design of software were also proven to be validity. The controller achieved all expectable results.