Enabling steep slope walking on Husky using reduced order modeling and quadratic programming

Abstract

Wing-assisted inclined running (WAIR) observed in some young birds, is an attractive maneuver that can be extended to legged aerial systems. This study proposes a control method using a modified Variable Length Inverted Pendulum (VLIP) by assuming a fixed zero moment point and thruster forces collocated at the center of mass of the pendulum. A QP MPC is used to find the optimal ground reaction forces and thruster forces to track a reference position and velocity trajectory. Simulation results of this VLIP model on a slope of 40 degrees is maintained and shows thruster forces that can be obtained through posture manipulation. 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.

Figures (8)

• Figure 1: Image of Husky Carbon ramezani_generative_2021, a legged-aerial robot, positioned on an inclined surface. Husky features four electric ducted fans mounted on its torso and twelve custom-designed actuators with high energy density.
• Figure 2: Depicts the parameters of the full, Husky reduced-order model (HROM), and the planar variable length inverted pendulum (VLIP) model, which are employed to govern the equations of motion as detailed in Section \ref{['sec:modelling']}. The thruster forces and moments are applied at the body's center of mass to assist in walking and climbing up the slope.
• Figure 3: Figure depicting Snapshots from the Matlab simulation of the WAIR VLIP model going up a slope of 40 degrees
• Figure 4: Error and tracking performance of body position and velocity
• Figure 5: Position tracking in COP frame