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From underactuation to quasi-full actuation: Aiming at a unifying control framework for articulated soft robots

Keppler, Manuel and Ott, Christian and Albu-Schäffer, Alin Olimpiu (2022) From underactuation to quasi-full actuation: Aiming at a unifying control framework for articulated soft robots. International Journal of Robust and Nonlinear Control, 32 (9), pp. 5453-5484. Wiley. doi: 10.1002/rnc.6102. ISSN 1049-8923.

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Official URL: https://dx.doi.org/10.1002/rnc.6102


We establish a structure preserving state and input transformation that allows a class of underactuated Euler Lagrange systems to be treated as “quasi-fully” actuated. In this equivalent quasi-fully actuated form, the system is characterized by the same Lagrangian structure as the original one. This facilitates the design of control approaches that take into account the underlying physics of the system and that shape the system dynamics to a minimum extent. Due to smoothness constraints on the new input vector that acts directly on the noncollocated coordinates, we coin the term quasi-fully actuated. The class of Euler–Lagrange systems we consider is the class of articulated soft robots with nonlinear spring characteristics that are modeled with a block diagonal inertia matrix. We illustrate how the quasi-fully actuated form enables the direct transfer of control concepts that have been derived for fully actuated manipulators. We adopt the popular energy-shaping and two passivity-based concepts. The exemplary adoptions of the PD+ and Slotine and Li controllers allow us to solve the task-space tracking problem for highly elastic joint robots with nonlinear spring characteristics. These control schemes allow compliant behavior of the robot's TCP to be specified with respect to a reference trajectory. A key aspect of the presented framework is that it enables the adoption of rigid joint controllers as well as concepts underlying the original stability analysis. We believe that our framework presents an important step toward unifying the control design for rigid and articulated soft robots.

Item URL in elib:https://elib.dlr.de/193639/
Document Type:Article
Title:From underactuation to quasi-full actuation: Aiming at a unifying control framework for articulated soft robots
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Keppler, ManuelUNSPECIFIEDhttps://orcid.org/0000-0002-1532-963XUNSPECIFIED
Ott, ChristianUNSPECIFIEDhttps://orcid.org/0000-0003-0987-7493UNSPECIFIED
Albu-Schäffer, Alin OlimpiuUNSPECIFIEDhttps://orcid.org/0000-0001-5343-9074142115925
Date:26 February 2022
Journal or Publication Title:International Journal of Robust and Nonlinear Control
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 5453-5484
Keywords:robot control, joint elasticity, passivity-based control, impedance control, underactuated system
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Robotics
DLR - Research area:Raumfahrt
DLR - Program:R RO - Robotics
DLR - Research theme (Project):R - Robot Dynamics & Simulation [RO]
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013) > Analysis and Control of Advanced Robotic Systems
Institute of Robotics and Mechatronics (since 2013)
Deposited By: Keppler, Manuel
Deposited On:26 Jan 2023 20:07
Last Modified:26 Sep 2023 14:34

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