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Soft Hands

Soft Hands represent a departure from classical robot hand design, which often relies on exact models and precise planning of contact points. Instead, we aim to increase robustness and safety through the use of soft materials and flexible mechanics. This softness allows us to exploit contact with the environment and use it in robust grasping and manipulation strategies.

In our lab we develop the RBO Hand 2, research necessary Soft Robotic aspects, and formulate the concept of Morphological Computation.

RBO Hand 2

Lupe

The RBO Hand 2 is a hand made from PneuFlex actuators mounted on a flexible, printed scaffold. The hand was developed to investigate the capabilities and limits of hands when relying only on soft, deformable structures. The unique deformability provides several advantageous benefits to robots trying to interact with the environment:

  • very robust against blunt collisions
  • very low impact energies
  • passively compliant fingers and palm decouple contact from the robot arm, stabilizing force control
  • mechanical adaptability to object shapes simplifies finger control
  • the pneumatic actuation makes it easy to create complex hand and actuator geometries

The result of our research are several hand prototypes, which we refer to collectively as Soft Hands. RBO Hand 2 is the latest model and used in our lab for research into grasping strategies.

The RBO Hand 2 is controlled using a PneumaticBox and is relatively cheap to produce, modify and repair.

If you want to build your own, you are welcome to do so! We have published the CAD models for the PneuFlex actuators.

Contact: Raphael Deimel, Vincent Wall

Videos of the RBO Hand 2

You can find more videos of the soft hands on our YouTube channel!

 

Versions of the RBO Hand

Over time we have created quite a few different versions of the RBO Hand. Here are a few:

Sensorized RBO Hand 2

The sensor feedback of the RBO Hand 2 is limited to the channel pressures. But the space of potential deformations of the PneuFlex actuators is very large.

While it will not be possible to detect all those different deformations, we proposed a method to sensorize the fingers of the RBO Hand 2 to detect task relevant deformations. The result is the Sensorized RBO Hand 2.

Related Publication:
Wall, Vincent, Gabriel Zöller, and Oliver Brock. "A method for sensorizing soft actuators and its application to the RBO hand 2." Robotics and Automation (ICRA), 2017 IEEE International Conference on. IEEE, 2017. [Link] (PDF, 1,7 MB)

Contact: Vincent Wall 

Hand prototypes for the SOMA project

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As part of the SOMA project we develop versions of the RBO Hand, based on feedback from all partners in the consortium. These hand versions change the geometry of the fingers, palms, and wrist. Because the RBO Hand is assembled from modular parts, we can quickly switch out parts and try different ideas.

The (original) RBO Hand

Lupe

The RBO Hand (published in 2013) was the first soft hand that employed PneuFlex actuators. It uses 3 pairs of parallel and straight PneuFlex actuators. The finger are also partially connected to each other. The hand has a passively bendable rubber sheet acting as a palm in opposition to the fingers.

Related publication:
Deimel, Raphael, and Oliver Brock. "A compliant hand based on a novel pneumatic actuator." Robotics and Automation (ICRA), 2013 IEEE International Conference on. IEEE, 2013. [Link] (PDF, 1,9 MB)

PneumaticBox

Lupe

For the control of the pneumatic RBO Hand 2 we had to create our own hardware. We developed the "PneumaticBox", which consists of valve array, a single-board computer, and a custom printed circuit board. 

A detailed description of the hard- and software can be found in the Tutorial section.

Soft Robotics

PneuFlex actuators

Lupe

We develop a set of production processes and a complete design toolchain for soft continuum actuators under the name PneuFlex. The toolchain consists of several components:

  • A unified process to create PneuFlex actuators of diverse shape from a given mold
  • A method to automatically create PneuFlex molds from a parametric description of shape.
  • A method to automatically create PneuFlex molds from a description of mechanical parameters
  • A system to simulate a PneuFlex actuator or to simulate arrangements of actuators (i.e. soft hands)
  • A pneumatic control hardware tailored to the requirements of finger-size soft continuum actuators
  • Controllers to enable complex, synchronized actuation across PneuFlex actuators

Soft Sensors

PneuFlex actuators with liquid metal strain sensors
Lupe

Due to the high deformability of soft actuators, most existing sensor technologies are not compatible. They often rely on joints and rigid links and are not flexible enough to work with silicone rubber based actuators.

This is why one branch of our research tackles this problem and investigates how to add rich tactile and proprioceptive feedback to highly flexible actuators like the PneuFlex.

An example of some of the alternative sensor technologies we explore are:

  • Deformation sensing using liquid metal strain sensors
  • Shape sensing using fiber Bragg grating of optical fibers
  • Strain sensing with conductive thermoplastic elastomer fibers
  • Touch sensing with stretchable multi-layer capacitive surfaces

Contact: Vincent Wall

Printable Fingers

Lupe

Current and expected advances in additive manufacturing promise to provide roboticists with the means to literally print complete soft actuators in a single, automated manufacturing step. This could drastically simplify the fabrication process and allow for quicker exploration of various design properties. Additionally, incorporating structures on the mesoscale opens design choices not possible with solid bulk materials.

Together with our partners from the SoMa project we investigate how to create flexible 3D-models for pneumatic actuators, that we can simulate, adapt, and print.

Contact: Vincent Wall

 

 

Morphological Computation

Lupe

The term Morphological Computation emphasizes the notion, that the way a robot is built (its morphology) provides a substantial contribution to the computation of reactive behavior. Intuitively, controlling a robot on the higher level gets simpler when the robot's body provides more Morphological Computation to the task.

At RBO Lab, we investigate methods to quantify the contribution of a robot's morphology to a specific task, and ways of increasing that share. We use soft hand design as a use case that provides sufficient complexity and cooperate with MPI Leipzig on the supporting theory

 

 

 

 

 

Funding

Lupe

SoMa - Soft Manipulation, Horizon 2020 project funded by the European Commission. May 2015 - April 2019. Alexander von Humboldt professorship - awarded by the Alexander von Humboldt foundation and funded through the Ministry of Education and Research, BMBF,
July 2009 - June 2015

Publications

Raphael Deimel and Patrick Irmisch and Vincent Wall and Oliver Brock. Automated Co-Design of Soft Hand Morphology and Control Strategy for Grasping. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017.

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Espen Knoop and Moritz Bächer and Vincent Wall and Raphael Deimel and Oliver Brock and Paul Beardsley. Handshakiness: Benchmarking for Human-Robot Hand Interactions. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017.

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Keyan Ghazi-Zahedi and Raphael Deimel and Guido Montúfar and Vincent Wall and Oliver Brock. Morphological Computation: The Good, the Bad, and the Ugly. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017.

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Vincent Wall and Gabriel Zöller and Oliver Brock. A Method for Sensorizing Soft Actuators and Its Application to the RBO Hand 2. Proceedings of the IEEE International Conference on Robotics and Automation (ICRA), pp. 4965–4970, 2017.

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Raphael Deimel and Marcel Radke and Oliver Brock. Mass Control of Pneumatic Soft Continuum Actuators with Commodity Components. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pp. 774–779, 2016.

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Raphael Deimel and Oliver Brock. A Novel Type of Compliant and Underactuated Robotic Hand for Dexterous Grasping. The International Journal of Robotics Research 35(1-3):161-185, 2016.

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Vincent Wall and Raphael Deimel and Oliver Brock. Selective Stiffening of Soft Actuators Based on Jamming. Proceedings of the IEEE International Conference on Robotics and Automation (ICRA), pp. 252-257, 2015.

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Raphael Deimel and Oliver Brock. A Novel Type of Compliant, Underactuated Robotic Hand for Dexterous Grasping. Robotics:Science and Systems (RSS), 2014.

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Raphael Deimel and Oliver Brock. A Compliant Hand Based on a Novel Pneumatic Actuator. Proceedings of the IEEE International Conference on Robotics and Automation (ICRA), pp. 2047–2053, 2013.

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