Thruster-Assisted Incline Walking

TL;DR

This work addresses slope navigation for a quadruped using thruster-assisted locomotion by extending WAIR concepts to Husky Carbon. It introduces a reduced-order model (HROM) and a collocation-based optimization to jointly coordinate foot placement and thruster inputs, ensuring ground reaction forces stay inside friction cones. Simulation results on a 30-degree incline demonstrate feasible thruster-wrench control that maintains body stability and contact, with normal forces kept above a minimum and friction constraints respected. The approach expands the operational envelope of multi-modal legged systems and lays groundwork for experimental validation and more robust control under real-world disturbances.

Abstract

In this study, our aim is to evaluate the effectiveness of thruster-assisted steep slope walking for the Husky Carbon, a quadrupedal robot equipped with custom-designed actuators and plural electric ducted fans, through simulation prior to conducting experimental trials. Thruster-assisted steep slope walking draws inspiration from wing-assisted incline running (WAIR) observed in birds, and intriguingly incorporates posture manipulation and thrust vectoring, a locomotion technique not previously explored in the animal kingdom. Our approach involves developing a reduced-order model of the Husky robot, followed by the application of an optimization-based controller utilizing collocation methods and dynamics interpolation to determine control actions. Through simulation testing, we demonstrate the feasibility of hardware implementation of our controller.

Figures (7)

• Figure 1: Capturing Northeastern Husky Carbon, a quadrupedal robot with four ducted fans affixed to its torso, undergoing WAIR locomotion tests inspired by avian biomechanics, as it navigates a ramp.
• Figure 2: Depicts the parameters of the reduced-order model (ROM) for the Husky, which are employed to govern the equations of motion as detailed in Section \ref{['sec:mdl']}.
• Figure 3: Illustrates snapshots of the WAIR simulation performed in Matlab on a slope of 30 degrees. The figure also shows the foot locations, Center of mass trajectory, optimal thrust wrench inputs (red), scaled ground reaction (green) forces and the positions of the legs. It can be seen that the ground reaction force stays within the friction cone
• Figure 4: Body states during 30-degree incline WAIR simulation.
• Figure 5: Ground reaction forces of the active stance feet in contact with the ground during the WAIR maneuver with and without thrusters. The red shaded region shows HROM walking on the slope, The horizontal lines at 0 N show that without thruster input the normal forces to the surface tend to become close to zero or even negative (i.e foot loses contact with the ground)