Development of operator training support system for small-scale helicopters by automatic recovery control with attitude and velocity stabilization

Abstract

Applications of small unmanned helicopters are rapidly growing in the civilian and commercial field such as pesticide spraying, aerial filming, and inspection. However, accidents often happen from deficient of operator skill, which leads to a large demand for reliable and skilled pilot. This paper describes the development of operator training support system that improves manual operation skill of the helicopter in safety under an actual environment. When attitude angle, velocity, or position exceed threshold values as a result of poor maneuvering or wind effect, manual inputs are automatically switched to control inputs and the helicopter is recovered to stabilized hover. The recovery controller is designed using quaternion-based formulation for nonlinear helicopter kinematics. The angular rate commands are calculated from quaternion error defined as the minimum-angle rotation required to decrease translational speed. To execute a high speed tracking control of angular rate, two-degrees-of-freedom servo system is applied to the inner loop dynamics. Nonlinear simulation and experiment result with this controller show smooth recovery maneuver from large attitude angle to hover state as if controlled by skilled pilot. A series of flight test with the operator training support system demonstrated the validity of the proposed architecture for accident avoidance during operator training. This system will contribute to safe and efficient operator training of unmanned helicopters.