Design and Characterization of a Novel Vacuum Bending Actuator and a Bimorph: for Preliminary Use in a Continuum Robot Arm

Conventional rigid robotic manipulators face difficulties when operating in confined areas. They also pose a safety risk when cohabiting a working environment with humans, animals or any other softer components. Soft and flexible robots provide a novel alternative solution in such places where the rigid system fails. Soft and flexible robotic manipulators are mostly inspired by biological counterparts such as elephant trunk and octopus arms. They have flexible limbs and redundant degrees of freedom where these characteristics enable special abilities such as variable bending, contraction, and stiffness. In this paper, the authors propose a soft vacuum bending actuator (VBA) that can be implemented as part of a soft flexible continuum robotic manipulator. The proposed actuator comprises a soft bendable silicone skeleton encompassed within a polyethylene (PE) film. When the air is removed from the cavity within the film, bending motion is obtained. In order to obtain multi-planar motion, two VBAs are connected in parallel to create a bimorph actuator. This paper presents the isotonic and isometric characterization of these devices. Experimental results show that a single VBA (132 mm length) was capable of lifting a maximum load of 204 g and achieving a 59 mm displacement (26° bending angle) while lifting 90 g at 10 kPa (abs.) and that a 47 g bimorph actuator can generate a 169 g force in isometric testing. Finally, a simple prototype continuum arm design is implemented to validate the applicability of the actuators. The results validate the applicability of this novel vacuum-actuated soft bending actuator for use in continuum arm applications.