Robust Control of a DC Motor and Load Using Quantitative Feedback Theory

This paper reports on robust position control of a DC motor and gear system attached to a mechanical load. The dynamics of the system will be identified using the sine wave inputs and least square method. It has been found out that a single linear time invariant (LTI) model cannot perfectly predicts the behavior of the system for a range of different frequencies. So, we are using a family of LTI systems instead with parameter uncertainty. Next a robust controller will be designed using Quantitative Feedback Theory (QFT) to provide consistent robust performance for the system. The performance of the QFT controller will be validated through both simulations and experimental data and will be compared with a PID controller. It has been shown that the QFT controller has a superior performance over the PID controller in terms of tracking error.