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Chapter 21 — Actuators for Soft Robotics

Alin Albu-Schäffer and Antonio Bicchi

Although we do not know as yet how robots of the future will look like exactly, most of us are sure that they will not resemble the heavy, bulky, rigid machines dangerously moving around in old fashioned industrial automation. There is a growing consensus, in the research community as well as in expectations from the public, that robots of the next generation will be physically compliant and adaptable machines, closely interacting with humans and moving safely, smoothly and efficiently - in other terms, robots will be soft.

This chapter discusses the design, modeling and control of actuators for the new generation of soft robots, which can replace conventional actuators in applications where rigidity is not the first and foremost concern in performance. The chapter focuses on the technology, modeling, and control of lumped parameters of soft robotics, that is, systems of discrete, interconnected, and compliant elements. Distributed parameters, snakelike and continuum soft robotics, are presented in Chap. 20, while Chap. 23 discusses in detail the biomimetic motivations that are often behind soft robotics.

Variable impedance actuators: Moving the robots of tomorrow

Author  B. Vanderborght, A. Albu-Schäffer, A. Bicchi, E. Burdet, D. Caldwell, R. Carloni, M. Catalano, Ganesh, Garabini, Grebenstein, Grioli, Haddadin, Jafari, Laffranchi, Lefeber, Petit, Stramigioli, Tsagarakis, Van Damme, Van Ham, Visser, Wolf

Video ID : 456

Most of today's robots have rigid structures and actuators requiring complex software control algorithms and sophisticated sensor systems in order to behave in a compliant and safe way adapted to contact with unknown environments and humans. By studying and constructing variable impedance actuators and their control, we contribute to the development of actuation units that can match the intrinsic safety, motion performance and energy efficiency of biological systems and, in particular, of the humans. As such, this may lead to a new generation of robots that can co-exist and co-operate with people and get closer to the human manipulation and locomotion performance than is possible with current robots.

PETMAN tests Camo

Author  Boston Dynamics

Video ID : 457

The PETMAN robot was developed by Boston Dynamics with funding from the DoD CBD program. It is used to test the performance of protective clothing designed for hazardous environments. The video shows initial testing in a chemical protection suit and gas mask. PETMAN has sensors embedded in its skin that detect any chemicals leaking through the suit. The skin also maintains a microclimate inside the clothing by sweating and regulating temperature. Partners in developing PETMAN were MRIGlobal, Measurement Technology Northwest, Smith Carter, SRD, CUH2A, and HHI.

Introducing WildCat

Author  Boston Dynamics

Video ID : 458

WildCat is a four-legged robot being developed to run fast on all types of terrain. So far WildCat has run at about 16 mph on flat terrain using bounding and galloping gaits. The video shows WildCat's best performance so far. WildCat is being developed by Boston Dynamics with funding from DARPA's M3 program. For more information about WildCat visit our website at

VSA-CubeBot - Peg in hole

Author  Centro di Ricerca "E. Piaggio"

Video ID : 460

VSA-CubeBot performing an assembly task. It consists in inserting a chamfered 29.5 mm diameter cylindrical peg in a 30 mm diameter round hole. The task is performed using only inexpensive position sensors, without force measurements, by exploiting the intrinsic mechanical elasticity of the variable impedance actuation units.

DLR Hand Arm System smashed with baseball bat

Author  Sebastian Wolf, Oliver Eiberger, Gerd Hirzinger

Video ID : 461

The DLR Hand Arm System is equipped with variable stiffness actuators (VSA). In this demonstration of robustness, the arm resists the impact of a baseball bat.

Safety evaluation of lightweight robots

Author  Sami Haddadin

Video ID : 463

Inteview with Sami Haddadin on safety evaluation of lightweight robots (Discovery Channel interview "Daily Planet", January 9th, 2008)

Hammering task with the DLR Hand Arm System

Author  Markus Grebenstein, Alin Albu-Schäffer, Thomas Bahls, Maxime Chalon, Oliver Eiberger, Werner Friedl, Robin Gruber, Sami Haddadin, Ulrich Hagn, Robert Haslinger, Hannes Höppner, Stefan Jörg, Mathias Nickl, Alexander Nothhelfer, Florian Petit, Josef Rei

Video ID : 464

The DLR Hand Arm System uses a hammer to drive a nail into a wooden board. The passive flexibility in the variable stiffness actuators (VSA) helps to keep a stable grasp during the impact and protects the hardware from damage.

Dynamic walking of whole-body compliant humanoid COMAN

Author  Chengxu Zhou, Xin Wang, Zhibin Li, Nikolaos Tsagarakis

Video ID : 465

COMAN performing dynamic walking.

BLUE: A biped robot with variable stiffness and damping

Author  Chengxu Zhou, Xin Wang, Zhibin Li, Nikolaos Tsagarakis

Video ID : 466

The video includes clips of the robot walking, squatting while displaying various degrees of stiffness, and the stiffness adjustment mechanism.

Maccepa system

Author  Michael Gutmacher, Bram Vanderborght et al.

Video ID : 467

The Maccepa system used for a brachiation robot.