Soft Robot Arm Inspired by the Octopus

Abstract

The octopus is a marine animal whose body has no rigid structures. It has 8 arms composed of a peculiar muscular structure, named muscular hydrostat. The octopus arms provide it with both locomotion and grasping capabilities, thanks to the fact that their stiffness can change over a wide range and it can be controlled through combined contractions of the muscles. The muscular hydrostat can better be seen as a modifiable skeleton. Furthermore, the morphology the arms and the mechanical characteristics of their tissues are such that the interaction with the environment, namely water, is exploited to simplify control. Thanks to this effective mechanism of embodied intelligence, the octopus can control a very high number of degrees of freedom, with relatively limited computing resources. From these considerations, the octopus emerges as a good model for embodied intelligence and for soft robotics. The prototype of a robot arm has been built based on an artificial muscular hydrostat inspired to the muscular hydrostat of the Octopus vulgaris. The prototype presents the morphology of the biological model and the broad arrangement of longitudinal and transverse muscles. Actuation is obtained with cables (longitudinally) and with SMA springs (transversally). The robot arm combines contractions and it can show the basic movements of the octopus arm, like elongation, shortening, and bending

Design, fabrication and control of soft robots

“…4): 1) Variable length tendons (in the form of tension cables 23 or shape memory alloy actuators 24 ) may be embedded in soft segments, to achieve, for example, robotic octopus arms (Fig. 3f).…”

“…An understanding of worm biomechanics also led to a bioinspired worm design composed of flexible materials and actuated by shape memory actuators (SMAs) 88 , and an annelid inspired robot actuated by dielectric elastomer 22 . A European initiative studied the biomechanics and control of the octopus to produce a soft robotic prototype 24,9 . Likewise, a self-contained, autonomous robotic fish actuated by soft fluidic actuators was demonstrated to be capable of forward swimming, turning, and depth adjustment 11, 31 (see Fig.…”

Light‐Driven Soft Robot Mimics Caterpillar Locomotion in Natural Scale

“…[10][11][12] Realizing a natural size caterpillar robot faces two challenges. First, the size of available actuators, either based on shape-memory alloys, [13] dielectric elastomers, [14] or pneumatic/ fluidic artificial muscles [3,15] prevents miniaturization. Not only are the smallest robots to date tens of centimeters in size, but they also require external power to be supplied via wires or tubing.…”

Simple or Complex Bodies? Trade-offs in Exploiting Body Morphology for Control

“…"Soft" robots, with the robot Octopus (e.g., [29]) serving as a good representative, break the traditional separation of control and mechanics and exploit the morphology of the body and properties of materials to assist control as well as perceptual tasks. Pfeifer et al [40] even discuss a new industrial revolution.…”

“…At the same time, the bodies themselves tend to be much more complex in terms of geometrical as well as dynamical properties. This has motivated the design of compliant, tendon-driven robots like ECCE [51] or Kenshiro [35], and soft, deformable robots like Octopus (e.g., [29]) (we are moving from left to right in Fig. 1).…”