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.

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 [2] 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 [3].

Contact: Raphael Deimel, Vincent Wall [4]

You can find more videos of the soft hands on our YouTube channel [5]!

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

As part of the SOMA project [10] 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 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] [12]

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 [14].

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 [16] 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 [17] tailored to the requirements of finger-size soft continuum actuators
• Controllers to enable complex, synchronized actuation across PneuFlex actuators

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 [19] we investigate how to create flexible 3D-models for pneumatic actuators, that we can simulate, adapt, and print.

Contact: Vincent Wall [20]

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 [22] on the supporting theory