Position compensation in all attitude of flying objects and application to flip maneuver control of small unmanned helicopters

Abstract

Flight control system with position compensation applicable to trajectory tracking of agile maneuvers that require an attitude rotation and a reverse of main rotor thrust of single-rotor helicopters is proposed. The outer loop position compensator calculates the desired attitude and rotor thrust which reduce position tracking error by utilizing a kinematics equation established near the reference trajectory. The desired attitude is set using the magnitude of the rotor thrust in the reference trajectory, which enables continuous position feedback compensation based on the fact that the relationship between rotational and translational motion becomes independent as the rotor thrust decrease. To achieve high-bandwidth control of lateral-longitudinal angular rates in the inner loop, two-degree-of-freedom servo system is designed using a linear model with blade flapping motion dynamics. The control system is applied to autonomous control of flip maneuvers which include transition between upright and inverted hovering. The reference trajectory of a flip maneuver is generated as a parameterized simple equation which can be adjusted to the helicopter ability. Simulation and outdoor flight tests of the autonomous flip maneuvers demonstrated the capability of position feedback compensation that reduces position tracking error during out-of-trimmed flight state. This control technique can be extended to various agile flights for quick execution of flight tasks or recovery maneuvers from dangerous state.