LQG/LTR Based Controller Design for Three Degree of Freedom Helicopter/Twin Rotor Control System

This work focuses on the design of a linear quadratic Gaussian controller for three degree of freedom helicopter. This system is developed at PIEAS for studying the dynamics of multi-input multi-output system. The system is underactuated having three degrees of freedom and two actuators. The outputs of the system are phi, thetas positions in the horizontal plane and in the vertical plane as well as the position along the vertical axis i.e. height. The system is inherently nonlinear and unstable. The nonlinear model of the plant has also been presented. We have linearized the system and designed a robust controller using linear quadratic Gaussian/loop transfer recovery (LQG/LTR) technique for the system. LQG/LTR guarantees both good robustness and performance. The technique is applicable for the square/fully actuated plants. We applied this technique to the underactuated system by modifying the plant inputs. We augmented a dummy input to the plan to make the plant square. Using this controller we successfully track the two outputs phi and h of the system and regulate the vertical position thetas. The simulation result of the plant with controller has been presented, which shows the effectiveness of the algorithm