Abstract:
This paper explains the strategies to create a hardware-based real time model of DC servomotor by utilizing the FPGA
technology that can accurately simulate the behavior of the servomotor in real-time. Such FPGA based hardware model is useful for
testing control algorithms, validating designs, and optimizing performance for various applications because of its reconfiguration
capabilities. Continuous-time model is discretized using both Backward Euler (BE) and Trapezoidal (TRZ) methods for the real-time
implementation on FPGA. The discretized models are coded using ‘C’, converted to hardware descriptive language using Vivado high
level synthesis tools, and the performance is analyzed with change in step-size by comparing with the transfer function (TF) model.
With 100 μsec step-size, TRZ response is found to be matching with the TF model, however, a step-size of 0.6 μsec was required for
the BE. Also analyzed the closed loop speed control performance of the hardware-based real time DC servomotor models with discrete
PID controller, again by varying the step-size. Both the BE and TRZ models could track the reference speed within 2 msec, because
of the PID controller, however faster dynamics was observed in case of TRZ as compared to BE, especially with larger step-size. These
analysis shows the effect of step-size and the discretization technique for the real-time modeling, however, with a suitable selected
values, the developed FPGA model can be utilized efficiently for the development of suitable control algorithm.
