Dynamic modelling and linear quadratic Gaussian control of a twin-rotor multi-input multi-output system

This paper presents an investigation into the modelling and control of a one-degree-of-freedom (1 DOF) twin-rotor multi-input multi-output (MIMO) system (TRMS). The behaviour of the TRMS in certain aspects resembles that of a helicopter. Hence, it is an interesting identification and control problem. A dynamic model characterizing the TRMS in hover is extracted using a black-box system identification technique. The extracted model is employed in the design of a feedback linear quadratic Gaussian compensator, namely the stability augmentation system (SAS). This has a good tracking capability but requires high control effort and has inadequate authority over residual vibration of the system. These problems are resolved by further augmenting the system with a command path prefilter, resulting in the command and stability augmentation system (CSAS). The combined feedforward and feedback compensator satisfies the performance objectives and obeys the actuator constraint. The control law is implemented in realtime on the TRMS platform.