| The general structure and working principle of the high performance digital servo-system driven by 4-motors are introduced firstly in this thesis. And some improvements are made during speed-loop experiments. Then, two kinds of nonlinearities, backlash and friction are studied in detail. Anti-backlash scheme using bias-voltage control method in the system is introduced. And a friction model is established with MATLAB Simulink toolbox, which is composed of static friction, Coulomb friction and viscous friction. Bad influence on the system caused by friction is confirmed by both simulation and system experiments. A fixed friction compensation method based on friction model is proposed and its validity is proved by simulation. Finally, a system fault tolerant control method based on FDD (Fault Detection and Diagnostics) technology is designed. For detecting the faults in real time, MCU is used to detect, identify and deal with faults with the help of PC/104 computer. Experiment results show that system runs smoothly and steadily when local faults occur. |
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