UAV rotorcraft in compliant contact: Stability analysis and simulation

A hovering vehicle interacting with objects and surfaces must be robust to contact forces and torques transmitted to the airframe, which produce coupled dynamics distinctly different from those of free flight. These mechanics may be modeled as elastic couplings between the aircraft and the ground, represented by a 6-DOF spring in ℝ³×SO(3).We show that Proportional Derivative attitude and position controllers that stabilize a rotorcraft in free flight will also stabilize the aircraft during contact for a range of contact displacements and stiffnesses. Simulation of the coupled aircraft dynamics demonstrates stable and unstable modes of the system.