A lightweight, multi-axis compliant tensegrity joint

Lessard, Steven; Bruce, Jonathan; Jung, Erik; Teodorescu, Mircea; SunSpiral, Vytas; Agogino, Adrian

doi:10.1109/icra.2016.7487187

Cited by 29 publications

(21 citation statements)

References 17 publications

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“…In this section, we consider the form-finding problem of a bio-inspired tensegrity arm proposed by Scarr [30] and Lessard et al [31], [32]. The arm is composed of a shoulder tetrahedron, humerus, and forearm that are stabilized by corresponding cables.…”

Section: Bio-inspired Tensegrity Armmentioning

confidence: 99%

A Task-Space Form-Finding Algorithm for Tensegrity Robots

Kong

2020

IEEE Access

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A modified dynamic relaxation algorithm for the form-finding of tensegrity robots in task space is proposed in this paper. There are some form-finding problems of tensegrity structures that are hard to be handled by the node-based dynamic relaxation algorithm. For tensegrity structures with multiple interconnected rods or rigid rods, the node-based dynamic relaxation algorithm is usually difficult to perform this type of form-finding. The node-based dynamic relaxation algorithm becomes rather cumbersome if several different ratios between rod lengths and cable lengths are desired, which restricts its applicability to less regular structural forms. The performance of the algorithm is affected by the relative difference in stiffness between members(cables and rods). To solve these problems, we extend the general dynamic relaxation algorithm from node space to task space. The proposed algorithm considers multiple interconnected rigid rods as an entire rigid body to derive its motion in six degrees of freedom. We simulated the motion process of the rigid body approaching its self-equilibrium position under the force exerted by all surrounding cables. In the form-finding process, the relative location relationship of all interconnected rods on a complex rigid body is maintained. The algorithm is valid for the form-finding of tensegrity structures which are with several different ratios between rod lengths and cable lengths. Besides, the modified algorithm is not affected by the stiffness of interconnected rods on rigid bodies. To demonstrate the capability of the method, four examples, including a two-segment spine robot, a bio-inspired tensegrity arm, a multi-segment spine robot, a tensegrity robot with disconnected and interconnected rigid rods, are presented in this paper.

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Section: Bio-inspired Tensegrity Armmentioning

confidence: 99%

A Task-Space Form-Finding Algorithm for Tensegrity Robots

Kong

2020

IEEE Access

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“…To determine which physical prototypes were fea-sible robotic arms, we initially simulated an array of various tensegrity robotic arms with NASA's Tensegrity Robotics Toolkit (NTRT). NTRT is an open-source simulator that allows users to design and control tensegrity structures and robots which has been built on top of the Bullet Physics Engine (version 2.82) 1 . These simulations illustrated which models were stable when controlled by a periodic signal.…”

Section: Figure 2 a Mapping Between The Major Compression Elements Omentioning

confidence: 99%

“…The nexuses observed in human arms inspired the functionally similar tensegrity joints in our model. These arm models use the same design as the elbow joint first described by Lessard et al [1] which functions similarly to a Cardan joint. In this elbow design, the number of compression and tension elements are minimized while maintaining two active degrees of freedom (and many more redundant passive degrees of freedom).…”

Section: Compression Elementsmentioning

confidence: 99%

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

Lessard

Castro

Asper

et al. 2016

2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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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.

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“…The purpose of this paper is twofold: first, to reformulate a marching procedure by using the force density method to obtain the static and kinematic expressions; second, to demonstrate, by simulations, that this procedure can effectively reconfigure a multi-stage tensegrity structure with fixed nodes from a stable initial position to another stable position, along different directions. The proposed method can represent an alternative for applications such as positioning, manipulation or simulation of human mechanics (Lessard et al, 2016). The structure of this paper is the following.…”

Section: Introductionmentioning

confidence: 99%

Reconfiguration of multi-stage tensegrity structures using infinitesimal mechanisms

González

Luo

Shi

2019

Lat. Am. j. solids struct.

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The use of tensegrity structures in soft robotics has seen an increased interest in recent years thanks to their mechanical properties, but the control of these systems remains an open problem. This paper presents a reconfiguration strategy for actuated multi-stage tensegrity structures. The algorithm works on the principle of using the infinitesimal mechanisms of the structure to generate a path of positions along which a multistage tensegrity structure can change its shape while maintaining the self-equilibrium. Combining the force density method with a marching procedure, the solution to the equilibrium problem is given by a set of differential equations that define the kinematic constraints of the structure. Beginning from an initial stable position, the algorithm calculates a small displacement until a new stable configuration is reached, and recurrently repeats the process during a given interval of time. By means of three numerical examples, we show the efficacy of our algorithm for reconfiguring a two-stage tensegrity mast along different directions.

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A lightweight, multi-axis compliant tensegrity joint

Cited by 29 publications

References 17 publications

A Task-Space Form-Finding Algorithm for Tensegrity Robots

A Task-Space Form-Finding Algorithm for Tensegrity Robots

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

Reconfiguration of multi-stage tensegrity structures using infinitesimal mechanisms

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