BALLU2: A Safe and Affordable Buoyancy Assisted Biped

Chae, Hosik and Ahn, Min Sung and Noh, Donghun and Nam, Hyunwoo and Hong, Dennis (2021) BALLU2: A Safe and Affordable Buoyancy Assisted Biped. Frontiers in Robotics and AI, 8. ISSN 2296-9144

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Abstract

This work presents the first full disclosure of BALLU, Buoyancy Assisted Lightweight Legged Unit, and describes the advantages and challenges of its concept, the hardware design of a new implementation (BALLU2), a motion analysis, and a data-driven walking controller. BALLU is a robot that never falls down due to the buoyancy provided by a set of helium balloons attached to the lightweight body, which solves many issues that hinder current robots from operating close to humans. The advantages gained also lead to the platform’s distinct difficulties caused by severe nonlinearities and external forces such as buoyancy and drag. The paper describes the nonconventional characteristics of BALLU as a legged robot and then gives an analysis of its unique behavior. Based on the analysis, a data-driven approach is proposed to achieve non-teleoperated walking: a statistical process using Spearman Correlation Coefficient is proposed to form low-dimensional state vectors from the simulation data, and an artificial neural network-based controller is trained on the same data. The controller is tested both on simulation and on real-world hardware. Its performance is assessed by observing the robot’s limit cycles and trajectories in the Cartesian coordinate. The controller generates periodic walking sequences in simulation as well as on the real-world robot even without additional transfer learning. It is also shown that the controller can deal with unseen conditions during the training phase. The resulting behavior not only shows the robustness of the controller but also implies that the proposed statistical process effectively extracts a state vector that is low-dimensional yet contains the essential information of the high-dimensional dynamics of BALLU’s walking.

Item Type: Article
Subjects: Archive Digital > Mathematical Science
Depositing User: Unnamed user with email support@archivedigit.com
Date Deposited: 23 Jun 2023 07:05
Last Modified: 20 Nov 2023 05:24
URI: http://eprints.ditdo.in/id/eprint/1223

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