New soft robots really suck!

Recent advances in soft robotics have seen the development of soft pneumatic actuators (SPAs) to ensure that all parts of the robot are soft, including the functional parts. These SPAs have traditionally used increased pressure in parts of the actuator to initiate movement, but today a team from NCCR Robotics and RRL, EPFL publish a …

Mori: A Modular Origami Robot

The fields of modular and origami robotics have become increasingly popular in recent years, with both approaches presenting particular benefits, as well as limitations, to the end user. Christoph Belke and Jamie Paik from RRL, EPFL and NCCR Robotics have recently proposed an elegant new solution that integrates both types of robotics in order to …

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Actuator With Angle-Dependent Elasticity for Biomimetic Transfemoral Prostheses

  • Authors: Pfeifer, Serge; Pagel, Anna; Riener, Robert; Vallery, Heike

Despite tremendous improvements in recent years, lower-limb prostheses are still inferior to their biological counterparts. Most powered knee joints use impedance control, but it is unknown which impedance profiles are needed to replicate physiological behavior. Recently, we have developed a method to quantify such profiles from conventional gait data. Based on this method, we derive stiffness requirements for knee prostheses, and we propose an actuation concept where physical actuator stiffness changes in function of joint angle. The idea is to express stiffness and moment requirements as functions of angle, and then to combine a series elastic actuator (SEA) with an optimized nonlinear transmission and parallel springs to reproduce the profiles. By considering the angle-dependent stiffness requirement, the upper bound for the impedance in zero-force control could be reduced by a factor of two. We realize this ANGle-dependent ELAstic Actuator (ANGELAA) in a leg, with rubber cords as series elastic elements. Hysteresis in the rubber is accounted for, and knee moment is estimated with a mean error of 0.7 Nm. The nonlinear parallel elasticity creates equilibria near 0◦ as well as 90◦ knee flexion, frequent postures in daily life. Experimental evaluation in a test setup shows force control bandwidth around 5–9 Hz, and a pilot experiment with an amputee subject shows the feasibility of the approach. While weight and power consumption are not optimized in this prototype, the incorporated mechatronic principles may pave the way for cheaper and lighter actuators in artificial legs and in other applications where stiffness requirements depend on kinematic configuration.

Posted on: October 22, 2014

Soft Pneumatic Gelatin Actuator for Edible Robotics

  • Authors: Shintake, Jun; Sonar, Harshal Arun; Piskarev, Egor; Paik, Jamie; Floreano, Dario

We present a fully edible pneumatic actuator based on gelatin-glycerol material. The actuator is monolithic, fabricated via a molding process, and measures 90 mm in length, 20 mm in width, and 17 mm in thickness. Thanks to the material mechanical characteristics similar to those of silicone elastomers, the actuator exhibits a bending angle of 170.3 degrees and a blocked force of 0.34 N at the applied pressure of 25 kPa. These values are comparable to elastomer based pneumatic actuators. As a validation example, two actuators are integrated to form a gripper capable of handling various objects, highlighting the high performance and applicability of the edible actuator. These edible actuators, combined with other recent edible materials and electronics, could lay the foundation for a new type of edible robots.

Posted on: October 3, 2017

Stretchable Materials for Robust Soft Actuators towards Assistive Wearable Devices

  • Authors: Agarwal, Gunjan; Besuchet, Nicolas; Audergon, Basile Nicolas; Paik, Jamie

Soft actuators made from elastomeric active materials can find widespread potential implementation in a variety of applications ranging from assistive wearable technologies targeted at biomedical rehabilitation or assistance with activities of daily living, bioinspired and biomimetic systems, to gripping and manipulating fragile objects, and adaptable locomotion. In this manuscript, we propose a novel two-component soft actuator design and design tool that produces actuators targeted towards these applications with enhanced mechanical performance and manufacturability. Our numerical models developed using the finite element method can predict the actuator behavior at large mechanical strains to allow efficient design iterations for system optimization. Based on two distinctive actuator prototypes’ (linear and bending actuators) experimental results that include free displacement and blocked-forces, we have validated the efficacy of the numerical models. The presented extensive investigation of mechanical performance for soft actuators with varying geometric parameters demonstrates the practical application of the design tool, and the robustness of the actuator hardware design, towards diverse soft robotic systems for a wide set of assistive wearable technologies, including replicating the motion of several parts of the human body.

Posted on: September 27, 2016