Soft Arms

Dynamic control of soft robots interacting with the environment

Despite the emergence of many soft-bodied robotic systems, model-based feedback control has remained an open challenge. This is largely due to the intrinsic difficulties in designing controllers for systems with infinite dimensions. We propose an alternative formulation of the soft robot dynamics which connects the robot’s behavior with the one of a rigid bodied robot with elasticity in the joints. The matching between the two system is exact under the common
hypothesis of Piecewise Constant Curvature. Based on this connection we introduce two control architectures, with the aim of achieving accurate curvature control and Cartesian regulation of the robot’s impedance, respectively. The curvature controller accounts for the natural softness of the system, while the Cartesian controller adapts the impedance of the end effector for interactions with an unstructured environment. This work proposes the first closed loop dynamic controller
for a continuous soft robot. The controllers are validated and evaluated on a physical soft robot capable of planar manipulation.

  • [PDF] C. Della Santina*, R. K. Katzschmann*, A. Bicchi, and D. Rus, “Dynamic control of soft robots interacting with the environment,” in 2018 IEEE-RAS International Conference on Soft Robotics (RoboSoft), 2018.
    [Bibtex]
    @inproceedings{della2018dynamic,
    author = {Della Santina*, Cosimo and Katzschmann*, Robert K. and Bicchi, Antonio and Rus, Daniela},
    booktitle = {2018 IEEE-RAS International Conference on Soft Robotics (RoboSoft)},
    title = {Dynamic control of soft robots interacting with the environment},
    month = {April},
    year = {2018}
    }

* Authors contributed equally to this work.

 

Autonomous Object Manipulation Using a Soft Planar Grasping Manipulator

This work presents the development of an autonomous motion planning algorithm for a soft planar grasping manipulator capable of grasp-and-place operations by encapsulation with uncertainty in the position and shape of the object. The end effector of the soft manipulator is fabricated in one piece without weakening seams using lost-wax casting instead of the commonly used multi-layer lamination process. The soft manipulation system can grasp randomly positioned objects within its reachable envelope and move them to a desired location without human intervention. The autonomous planning system leverages the compliance and continuum bending of the soft grasping manipulator to achieve repeatable grasps in the presence of uncertainty. A suite of experiments is presented that demonstrates the system’s capabilities.

  • [PDF] [DOI] R. K. Katzschmann, A. D. Marchese, and D. Rus, “Autonomous Object Manipulation Using a Soft Planar Grasping Manipulator,” Soft Robotics, vol. 2, iss. 4, pp. 155-164, 2015.
    [Bibtex]
    @article{katzschmann2015autonomous,
    author = {Katzschmann, Robert K. and Marchese, Andrew D. and Rus, Daniela},
    doi = {10.1089/soro.2015.0013},
    issn = {2169-5172},
    journal = {Soft Robotics},
    month = {dec},
    number = {4},
    pages = {155--164},
    publisher = {Mary Ann Liebert, Inc. 140 Huguenot Street, 3rd Floor New Rochelle, NY 10801 USA},
    title = {Autonomous Object Manipulation Using a Soft Planar Grasping Manipulator},
    url = {http://online.liebertpub.com/doi/10.1089/soro.2015.0013},
    volume = {2},
    year = {2015},
    abstract = {This paper presents the development of an autonomous motion planning algorithm for a soft planar grasping manipulator capable of grasp-and-place operations by encapsulation with uncertainty in the position and shape of the object. The end effector of the soft manipulator is fabricated in one piece without weakening seams using lost-wax casting instead of the commonly used multi-layer lamination process. The soft manipulation system can grasp randomly positioned objects within its reachable envelope and move them to a desired location without human intervention. The autonomous planning system leverages the compliance and continuum bending of the soft grasping manipulator to achieve repeatable grasps in the presence of uncertainty. A suite of experiments is presented that demonstrates the system's capabilities.},
    }

 

Whole Arm Planning for a Soft and Highly Compliant 2D Robotic Manipulator

Soft continuum manipulators have the advantage of being more compliant and having more degrees of freedom than rigid redundant manipulators. This attribute should allow soft manipulators to autonomously execute highly dexterous tasks. However, current approaches to motion planning, inverse kinematics, and even design limit the capacity of soft manipulators to take full advantage of their inherent compliance. We provide a computational approach to whole arm planning for a soft planar manipulator that advances the arm’s end effector pose in task space while simultaneously considering the arm’s entire envelope in proximity to a confined environment. The algorithm solves a series of constrained optimization problems to determine locally optimal inverse kinematics. Due to inherent limitations in modeling the kinematics of a highly compliant soft robot and the local optimality of the planner’s solutions, we also rely on the increased softness of our newly designed manipulator to accomplish the whole arm task, namely the arm’s ability to harmlessly collide with the environment. We detail the design and fabrication of the new modular manipulator as well as the planner’s central algorithm. We experimentally validate our approach by showing that the robotic system is capable of autonomously advancing the soft arm through a pipe-like environment in order to reach distinct goal states.

  • [PDF] [DOI] A. D. Marchese, R. K. Katzschmann, and D. Rus, “Whole Arm Planning for a Soft and Highly Compliant 2D Robotic Manipulator,” in Intelligent Robots and Systems (IROS), 2014 IEEE/RSJ International Conference on, 2014, pp. 554-560.
    [Bibtex]
    @inproceedings{marchese2014whole,
    author = {Marchese, Andrew D and Katzschmann, Robert K. and Rus, Daniela},
    booktitle = {Intelligent Robots and Systems (IROS), 2014 IEEE/RSJ International Conference on},
    doi = {10.1109/IROS.2014.6942614},
    isbn = {9781479969340},
    issn = {21530866},
    pages = {554--560},
    publisher = {IEEE},
    title = {Whole Arm Planning for a Soft and Highly Compliant 2D Robotic Manipulator},
    year = {2014},
    month = {nov},
    abstract = {Soft continuum manipulators have the advantage of being more compliant and having more degrees of freedom than rigid redundant manipulators. This attribute should allow soft manipulators to autonomously execute highly dexterous tasks. However, current approaches to motion planning, inverse kinematics, and even design limit the capacity of soft manipu- lators to take full advantage of their inherent compliance. We provide a computational approach to whole arm planning for a soft planar manipulator that advances the arm's end effector pose in task space while simultaneously considering the arm's entire envelope in proximity to a confined environment. The algorithm solves a series of constrained optimization problems to determine locally optimal inverse kinematics. Due to inherent limitations in modeling the kinematics of a highly compliant soft robot and the local optimality of the planner's solutions, we also rely on the increased softness of our newly designed manipulator to accomplish the whole arm task, namely the arm's ability to harmlessly collide with the environment. We detail the design and fabrication of the new modular manipulator as well as the planner's central algorithm. We experimentally validate our approach by showing that the robotic system is capable of autonomously advancing the soft arm through a pipe-like environment in order to reach distinct goal states.},
    }

News articles (Sept. 2014):

Will tomorrow’s robots move like snakes?” featured in
Popular Science, Washington Post, Huffpost, ACM TechNews

A Recipe for Soft Fluidic Elastomer Robots

This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes.

  • [PDF] [DOI] A. D. Marchese, R. K. Katzschmann, and D. Rus, “A Recipe for Soft Fluidic Elastomer Robots,” Soft Robotics, vol. 2, iss. 1, pp. 7-25, 2015.
    [Bibtex]
    @article{marchese2015recipe,
    author = {Marchese, Andrew D and Katzschmann, Robert K. and Rus, Daniela},
    doi = {10.1089/soro.2014.0022},
    issn = {2169-5172},
    journal = {Soft Robotics},
    number = {1},
    pages = {7--25},
    title = {A Recipe for Soft Fluidic Elastomer Robots},
    url = {http://online.liebertpub.com/doi/10.1089/soro.2014.0022},
    volume = {2},
    year = {2015},
    month = {mar},
    abstract = {This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes.},
    }

Link to Soft Manipulator Arms at the Distributed Robotics Laboratory, CSAIL, MIT