An Integrated Spatial Path-planning and Controller Design Approach for a Hover-mode Helicopter Model

The objective of this paper is to design a controller based on a nonlinear hover-mode model for a helicopter, which can be seamlessly integrated in an existing spatial path-planning approach. Unlike traditional approaches, this novel two-level hierarchical controller takes ‘ small-body forces’ explicitly into consideration. A higher level controller (HLC), with slower time-scale, controls the translational motion. This controller chooses the main rotor thrust, and a reference signal for the fuselage rotation matrix. This reference rotation matrix is then tracked by a lower level controller (LLC) at a faster time-scale, to select the two flapping angles of the tip path plane (TPP) and the tail rotor thrust. The reference rotation matrix is chosen by the HLC so as to meet the objective of local translation, specified by a local potential function. The local potential field is represented as an obstacle-free spherical region, a ‘ bubble’, in which the helicopter is constrained to fly. A string of such bubbles is generated by an existing spatial path-planning algorithm. The helicopter switches its controlling bubbles in a sequence to produce gross motion. The system is demonstrated by computer simulation, using a scaled model.