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Soft Hands represent a departure from classical robot hand design, as they explicitly exploit mechanical compliance and coupling to outsource control to the hardware. The goal is to make grasping strategies that rely on contact with the environment easier to execute and more robust, which is achieved by sacrificing full controllability of hand posture and knowledge of exact contact locations. While some soft parts and compliant structures are used in almost all grippers and hands, it is often added as an afterthought to "make things work". Until now, it hasn't been proposed as the central paradigm of hand design. We investigate what type of compliance and how much of it is beneficial, and how to best leverage the added morphological complexity to simplify higher level control.
Hand in hand with rethinking the hardware, we also have to adapt control and planning. Efforts to use Soft Hands effectively is therefore an important parallel branch of research
Another important aspect of soft hands is, that technology to build soft robots - when compared to that tendon-driven electromechanical hands - is still in its infancy. Therefore, we also research methods and technologies of Soft Robotics which we use as a toolbox to be able to prototype soft hands quickly and effectively.
For the same reasons, we also develop the Pneumaticbox, which is an system for real-time control of pneumatic valves, integrating pressure sensing and control algorithms tailored to soft continuum actuators.
RBO Hand 2
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.
You can find more videos of the soft hands on our YouTube channel!
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.