Soft robots that mimic human muscles

An EPFL team is developing soft, flexible and reconfigurable robots. Air-actuated, they behave like human muscles and may be used in physical rehabilitation. They are made of low-cost materials and could easily be produced on a large scale.


Published on Youtube Oct 11, 2016

Laure-Anne Pessina, École polytechnique fédérale de Lausanne, EPFL 12 October 2016

Robots are usually expected to be rigid, fast and efficient. But researchers at EPFL’s Reconfigurable Robotics Lab (RRL) have turned that notion on its head with their soft robots.

Soft robots, powered by muscle-like actuators, are designed to be used on the human body in order to help people move. They are made of elastomers, including silicon and rubber, and so they are inherently safe. They are controlled by changing the air pressure in specially designed ‘soft balloons’, which also serve as the robot’s body. A predictive model that can be used to carefully control the mechanical behavior of the robots’ various modules has just been published in Nature – Scientific Reports.

Potential applications for these robots include patient rehabilitation, handling fragile objects, biomimetic systems and home care. “Our robot designs focus largely on safety,” said Jamie Paik, the director of the RRL. “There’s very little risk of getting hurt if you’re wearing an exoskeleton made up of soft materials, for example” she added.

spamodeling
Modeling and Design of Soft Pneumatic Actuators. Numerical simulation results using Finite Element Analysis (FEA) for soft actuators in linear and bending motion. Simulations predict motion-force profiles obtained with the actuators, enabling the design of more efficient systems.
A model for controlling the actuators
In their article, the researchers showed that their model could accurately predict how a series of modules – composed of compartments and sandwiched chambers – move. The cucumber-shaped actuators can stretch up to around five or six times their normal length and bend in two directions, depending on the model.

“We conducted numerous simulations and developed a model for predicting how the actuators deform as a function of their shape, thickness and the materials they’re made of,” said Gunjan Agarwal, the article’s lead author.

One of the variants consists of covering the actuator in a thick paper shell made by origami. This test showed that different materials could be used. “Elastomer structures are highly resilient but difficult to control. We need to be able to predict how, and in which direction, they deform. And because these soft robots are easy to produce but difficult to model, our step-by-step design tools are now available online for roboticists and students.”

Gunjan Agarwal, Matthew Roberston and Jamie Paik. Creidt Marc Delachaux 2016 EPFL

A rehabilitation belt
In addition to these simulations, other RRL researchers have developed soft robots for medical purposes. This work is described in Soft Robotics. One of their designs is a belt made of several inflatable components, which holds patients upright during rehabilitation exercises and guides their movements.“We are working with physical therapists from the University Hospital of Lausanne (CHUV) who are treating stroke victims,” said Matthew Robertson, the researcher in charge of the project. “The belt is designed to support the patient’s torso and restore some of the person’s motor sensitivity.”

The belt’s soft actuators are made of pink rubber and transparent fishing line. The placement of the fishing line guides the modules’ deformation very precisely when air is injected. “For now, the belt is hooked up to a system of external pumps. The next step will be to miniaturize this system and put it directly on the belt,” said Robertson.

Adaptable and reconfigurable robots
Potential applications for soft actuators don’t stop there. The researchers are also using them to develop adaptable robots that are capable of navigating around in cramped, hostile environments. And because they are completely soft, they should also be able to withstand squeezing and crushing.

“Using soft actuators, we can come up with robots of various shapes that can move around in diverse environments,” said Paik. “They are made of inexpensive materials, and so they could easily be produced on a large scale. This will open new doors in the field of robotics.”

Source EPFL

Stretchable Materials for Robust Soft Actuators towards Assistive Wearable Devices, Agarwal G, Besuchet N, Audergon B, Paik J. Sci Rep. 2016 Sep 27;6:34224. doi: 10.1038/srep34224.

Also see
Soft Pneumatic Actuator Fascicles for High Force and Reliability, Robertson Matthew A., Sadeghi Hamed, Florez Juan Manuel, and Paik Jamie. Soft Robotics. October 2016, ahead of print. doi:10.1089/soro.2016.0029.
Design and Analysis of a Soft Pneumatic Actuator with Origami Shell Reinforcement, Paez Laura, Agarwal Gunjan, and Paik Jamie. Soft Robotics. September 2016, 3(3): 109-119. doi:10.1089/soro.2016.0023.
Modeling and Design Tool for Soft Pneumatic Actuators in Soft robotics toolkit
Jamie Paik and her “soft” robotics in EPFL
Soft Robotics: How to Make Squishy Machines in UNL Maker Club
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