The attitude model and control of a three-degree-of-freedom experiment helicopter bench

Abstract

In order to control the attitude of the tilt rotor aircraft when it is in its helicopter state, the three-degree-of-freedom helicopter bench has been established. The model of the bench is derived based on the Lagrange equation. If there are two control inputs and three outputs, the system can be looked on as an under-actuated system. In order to accomplish two different tasks, two kinds of simplified methods have been suggested. Based on these two different simplified models, two types of model-based controllers, including the filter error approximation controller and the hierarchy-modified proportional plus derivative (PD) controller, are proposed. The filter error approximation controller can make the helicopter track the desired changing pitch and elevation angles, whereas the hierarchy-modified PD controller can make the helicopter hover at definite travel angle and elevation angle. This hierarchy controller is a multi-loop controller, which utilizes the pitch control as the inner loop and the travel control as the outer loop. The numerical simulations have proved that these two controllers can fulfil the two different proposed tasks. And the hierarchy-modified PD controllers have also been tested successfully in real-time experiments in the helicopter test-bed.