A bio-inspired tensegrity manipulator with multi-DOF, structurally compliant joints

Abstract

Most traditional robotic mechanisms feature inelastic joints that are unable to robustly handle large deformations and off-axis moments. As a result, the applied loads are transferred rigidly throughout the entire structure. The disadvantage of this approach is that the exerted leverage is magnified at each subsequent joint possibly damaging the mechanism. In this paper, we present two lightweight, elastic, bio-inspired tensegrity robotic arms adapted from prior static models which mitigate this danger while improving their mechanism's functionality. Our solutions feature modular tensegrity structures that function similarly to the human elbow and the human shoulder when connected. Like their biological counterparts, the proposed robotic joints are flexible and comply with unanticipated forces. Both proposed structures have multiple passive degrees of freedom and four active degrees of freedom (two from the shoulder and two from the elbow). The structural advantages demonstrated by the joints in these manipulators illustrate a solution to the fundamental issue of elegantly handling off-axis compliance. Additionally, this initial experiment illustrates that moving tensegrity arms must be designed with large reachable and dexterous workspaces in mind, a change from prior tensegrity arms which were only static. These initial experiments should be viewed as an exploration into the design space of active tensegrity structures, particularly those inspired by biological joints and limbs.

Biotensegrity: What is the big deal?

“…Biotensegrity has influenced the development of robots destined for the exploration of space (Caluwaerts et al 2014) and new classes of joint and prostheses with potential medical applications (Lessard et al 2016). It inherently recognizes that complex living structures are the result of interactions between some basic principles of self-organization, and that Nature's 'strategy for design' is already contained within the dynamic architecture of the system.…”

Phase Changing Materials-Based Variable-Stiffness Tensegrity Structures

“…8,9 Recently, tensegrity structures 10 have been proposed as an approach to design soft robots with mechanical properties similar to those of biological systems at different scales, ranging from individual cells 11 to muscular-skeletal systems. 12 Examples of such tensegrity systems include robots with embodied intelligence, [13][14][15][16][17] bio-inspired manipulators, 18,19 soft modular robots, 20,21 and soft deployable robots. 22 However, in most of these case studies, tensegrity structures are characterized by a predefined and fixed stiffness.…”

Rolling Locomotion of Cable-Driven Soft Spherical Tensegrity Robots

“…12,13 Yet other tensegrity robots based on multimodule tensegrity prisms were developed for duct exploration and maintenance tasks, and two prototypes were constructed for this purpose. 14,15 Moreover, bioinspired tensegrity manipulators mimicking a human shoulder and elbow were developed 16,17 by building upon the fact that tensegrity structures can effectively describe anatomical structures of the human body. 18,19 Among the tensegrity robots that are being developed in various shapes, a special attention has been paid to spherical tensegrity robots as mobile robotic platforms.…”