WAIR Enabled by Thrust Vectoring Through Posture Manipulation on a Multimodal Aerial-Legged Robot

Wing-assisted inclined running (WAIR), an impressive evolutionary capability observed in young Chukar birds, is an attractive maneuver that can be extended to legged aerial systems like Husky, a multimodal aerial-legged robot. This study proposes an control method using a Single Rigid Body (SRB) model with massless legs and thruster forces collocated at the center of mass of the Rigid Body. An Model Predictive Program (MPC) is then used to find the optimal ground reaction forces (GRF), and thruster forces and moments to track a reference position and velocity trajectory. An analysis on the controllability of the linearized dynamics also shows the effect of thrusters on a legged robot. MATLAB simulation results of a high fidelity model on a slope of 40 degrees are obtained that highlight the fact that posture manipulation can be used to vector thrust forces on steep slopes. The simulation also provides insight to how the combined efforts of the thrusters and the tractive forces from the legs make WAIR possible in thruster-assisted legged systems.