Nonlinear Model Predictive Control (NMPC) for Twin Rotor MIMO System (TRMS)

Twin Rotor MIMO System (TRMS) is a dynamic model with high non-linearity that resembles a helicopter with reduced degree-of-freedom (DOF). Besides, cross-coupling between main rotor and tail rotor contributes to the difficulty in controlling the system. Majority of the previous researches have not focused on continuous actual dynamic disturbance test. The objectives of this project are to model TRMS and control the system against major disturbance (wind effect) and set-point changes. The first phase of the project started with mathematical modelling of direct current (DC) motors, where the relationship between input voltage and angular velocity was captured. The next phase would be the modelling of the whole system and design of controller. During the second phase, the modelling would involve aerodynamics and other Physics laws. Once the complete model was formed, Proportional, Integral and Derivative (PID) and Linear Quadratic Regulator (LQR) controllers were designed to optimize the dynamic system. The system has been tested using wind variation as actual dynamic disturbance to validate the disturbance rejection performance. It was found that the best performance from combination of PID and LQR controllers gave 89% improvement in term of pitch overshoot and 33% improvement in term of yaw overshoot during disturbance rejection compared to PID-only controller.