Analyzing the Impact of Discretization Techniques on Real Time Simulation of DC Servo Motor Using FPGA

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. The uniqueness of our paper lies in the application of C language for modeling a DC servomotor by discretizing the model with both Backward Euler (BE) and Trapezoidal (TRZ) methods. The discretized models are then implemented on FPGA using Vivado HLS 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 feasibility of Hardware-in-the-Loop (HIL) technique by connecting the DC servomotor in loop with the PID controller on FPGA, 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. This analysis demonstrates the impact of step-size and discretization technique on real-time modeling. By selecting suitable values, the FPGA model can be efficiently harnessed to develop a tailored control algorithm and optimize performance for diverse applications.