Capture Point Control in Thruster-Assisted Bipedal Locomotion

TL;DR

This paper introduces a capture point control strategy for a thruster-assisted bipedal robot, enhancing stability and terrain negotiation by integrating external forces into the control model, demonstrated through simulation results.

Contribution

It extends capture point control methods to include external forces like thrusters, a novel approach for improving bipedal robot stability on challenging terrains.

Findings

Controller demonstrates improved stability in simulations.

Inclusion of external forces offers new locomotion insights.

Potential for enhanced terrain negotiation capabilities.

Abstract

Despite major advancements in control design that are robust to unplanned disturbances, bipedal robots are still susceptible to falling over and struggle to negotiate rough terrains. By utilizing thrusters in our bipedal robot, we can perform additional posture manipulation and expand the modes of locomotion to enhance the robot's stability and ability to negotiate rough and difficult-to-navigate terrains. In this paper, we present our efforts in designing a controller based on capture point control for our thruster-assisted walking model named Harpy and explore its control design possibilities. While capture point control based on centroidal models for bipedal systems has been extensively studied, the incorporation of external forces that can influence the dynamics of linear inverted pendulum models, often used in capture point-based works, has not been explored before. The inclusion of these external forces can lead to interesting interpretations of locomotion, such as virtual buoyancy studied in aquatic-legged locomotion. This paper outlines the dynamical model of our robot, the capture point method we use to assist the upper body stabilization, and the simulation work done to show the controller's feasibility.