Modelling and experimental validation of an ultra-high precision positioning system based on the FPGA architecture

The nonlinear model of a small-scale ultra-high precision positioning device is developed in this work in the MATLAB/SIMULINK environment. The conventional Stribeck model is used to describe the DC motor frictional nonlinearities, while the more sophisticated Dahl model is used to predict the behaviour of the mechanical components of the system. In the experimental set-up, a linear incremental encoder is used as a feedback sensor, while a Michelson-type laser Doppler interferometric system is employed to validate the obtained precision and accuracy. The digital PID controller is implemented on the FPGA architecture by using the LabVIEW programming environment. A good matching of simulated and measured dynamic responses is obtained although some friction-induced discrepancies are still present.