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Inclusion of the Actuators Dynamics for Soft Robot Control

Novaki Ribeiro, Lucas (2022) Inclusion of the Actuators Dynamics for Soft Robot Control. Master's, Technische Universität München.

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During the last decade there has been a growth of interest in the field of soft robots. The natural compliant motion of these systems promises a safer human-machine interaction and robust locomotion and manipulation in unstructured environments. The possibility to use its own body to absorb or conserve energy represents a fundamental advantage not found in traditional rigid robots. However, in order to achieve this desired level of performance, there are still many theoretical and technical advances needed, many of which are related to model-based control. So far, the control strategies are based on either point-to-point motion through the use of static models, or dynamic controllers formulated in end-effector or configuration space, which neglect the dynamics of the actuation system. This thesis analyzes the influence of such actuators dynamics in soft robots for trajectory tracking and investigates how this problem can be tackled with a singular perturbation approach for the case of a tendon-driven planar continuum mechanism. First, the equations of motion of the mechanism are obtained using the variable length constant curvature model and the Euler-Lagrange method. Then, the control laws for singular perturbation based controllers are proposed. A parameter identification phase and validation of the kinematic model are performed. Numerical simulations and real experiments in a testbed for different tendon stiffness are made and analyzed, comparing singular perturbation with baseline feedback controllers. Additionally, the closed loop frequency response for each control law is assessed. The results showed how low tendon stiffness imposes a great limitation in the control performance for the standard feedback controllers. On its turn, by considering the coupling dynamics and introducing a force tracking inner loop, singular perturbation controllers were capable to damp vibrations and achieve lower control errors, while not relying on high gains. The inclusion of the motors inertial and damping forces also proved to be fundamental for high frequency motion.

Item URL in elib:https://elib.dlr.de/191504/
Document Type:Thesis (Master's)
Title:Inclusion of the Actuators Dynamics for Soft Robot Control
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:28 February 2022
Refereed publication:No
Open Access:No
Number of Pages:100
Keywords:Tendon-driven Soft Robot, Actuation Dynamics, Model-based control, Singular Perturbation
Institution:Technische Universität München
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)
Deposited By: Deutschmann, Dr. -Ing. Bastian
Deposited On:02 Dec 2022 08:11
Last Modified:02 Dec 2022 08:11

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