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Current and Outlook on Manufacturing and Processing Technologies
Published in Yoseph Bar-Cohen, Advances in Manufacturing and Processing of Materials and Structures, 2018
Tensegrity refers to axially loaded prestressed structures that can change their shape without changing stiffness and can change the stiffness without changing their shape (Skelton and de Oliveira, 2009). They have the smallest structural mass density for any given compressive strength, bending strength, or torsional strength, and therefore, they offer very efficient active structures. Tensegrity components consist of a continuous network made of bars or struts that are supported in compression by cables or in tension by tendons. An example of a tensegrity structure in packed and extended configurations is shown in Figure 20.11. Using a tensegrity structure, one can potentially makes a robotic arm that can be extended to a long-structure and then rigidized or alternately making an on-command flexible/collapsible arm. While being mounted on an orbiting spacecraft, such a tensegrity arm can be made to reach great distances and potentially perform tasks (e.g., sample acquisition and manipulation) on small bodies in the Solar System, including meteors and comets.
An Introduction to the Mechanics of Tensegrity Structures
Published in Osita D. I. Nwokah, Yildirim Hurmuzlu, The Mechanical Systems Design Handbook, 2017
Robert E. Skelton, J. William Helton, Rajesh Adhikari, Jean-Paul Pinaud, Waileung Chan
Tensegrity structures have geometric structure that can be designed to achieve desirable mechanical properties. First, this chapter demonstrates how bending rigidity varies with the geometrical parameters. The bending rigidity is reduced when a string goes slack, and pretension delays the onset of slack strings. The important conclusions made in this section are Beams made from tensegrity units can be stiffer than their continuous beam counterparts.Pretension can be used to maintain a constant bending rigidity over a wider range of external loads. This can be important to robustness, when the range of external loads can be uncertain.For larger loads the bending stiffness is dominated by geometry, not pretension. This explains the mass efficiency of tensegrity structures since one can achieve high stiffness by choosing the right geometry.The ratio of mass to bending rigidity of the C2T4 tensegrity is shown to be smaller than for a rectangular cross-section bar, provided the geometry is chosen properly (angle between bars must be less than 53°). Comparisons to a conventional truss would be instructive. There are many possibilities.
Synthesis of structural self-repairing and health monitoring
Published in You-Lin Xu, Jia He, Smart Civil Structures, 2017
Tensegrity structures are structures composed of tension elements (strings, tendons or cables) surrounding compression elements (bars or struts) in equilibrium (Motro and Raducanu 2003). Since only a small amount of energy is needed to change the shape of these structures, tensegrities are attractive solutions for controllable structures, and increasing effort has been made on the active control of tensegrity structures. The potential applications of tensegrities on footbridges or pedestrian bridges were actively investigated (e.g. Ali et al. 2010; Veuve et al. 2015). Adam and Smith (2007) further described how self-diagnosis, shape control and SR could be integrated into tensegrity structures to copy with unknown events. The identification of either loading or damage location was first involved in self-diagnosis, and then self-diagnosis results were used for control tasks such as shape control and/or SR. Self-repair involved stiffness increases and stress decreases with respect to the damage state. Further investigation of the SR of a damaged tensegrity pedestrian bridge with the aim of meeting safety and serviceability requirements was also conducted (Korkmaz et al. 2011). The introduction of self-diagnosis, SR and self-controlled tensegrity structures will be given in Section 18.6.
An overview of self-engineering systems
Published in Journal of Engineering Design, 2021
Tensegrity structures are lightweight, flexible structures made up of tensioned cables and struts in a continuous self-stresses state with cables in tension and struts in compression. Adam and Smith (2007) modelled and built a self-diagnosing and self-repairing tensegrity structure. The critical struts can extend or contract, creating different forces and enabling the structure to diagnose where a load change or damage has occurred. The structure contains more cables and supports than required for stability. The repair process uses this redundancy and changes cable tension to reduce the peak load on the cables until an optimum point is reached. However, the repair is designed to maintain the structural stability and safety but not the full functionality; for example, the top nodes may no longer form a flat surface. This forms a complete SE system though it is reliant of humans to manage stages of the process, the repair is also dependent on having redundant cables and struts to cope with damaged ones. A similar approach was modelled for a tensegrity bridge design; when a strut was broken, the cable length and tension were adjusted to cope and not deflect excessively (Korkmaz, Bel Hadj Ali, and Smith 2010). Unfortunately, the process was only modelled and not verified in a prototype or experiment.
Synergistic control of a multi-segments vertebral column robot based on tensegrity for postural balance
Published in Advanced Robotics, 2018
One architectural design that explains well biomechanical compliance is tensegrity structures [21,22]. Tensegrity structures can be seen as physical networks of stress and loads so that they have an inner stress and plasticity in their structure that make them resilient, adaptive and robust to some external loads. In comparison to most robotic designs, they do not follow Newton's law for rigid bodies as they have no joints and no momentum or torque since the motors are not on the axis of articulation. Instead, they follow Hooke's law for elastic bodies. These features make them a promising paradigm for integrating structure and control design [23–25]. For instance, we can easily formalize a tensegrity system as a network of tension (muscles and soft tissues) and compression (bones), or as a network of springs and masses [26,27]. Therefore, they can be viewed as complex dynamical systems with many degrees of freedom [10,28,29], which is a property often seen in biological systems [30–32].
Design, Fabrication and Construction of a Deployable Double-Layer Tensegrity Grid
Published in Structural Engineering International, 2018
Valentin Gomez-Jauregui, Michael Quilligan, Cristina Manchado, Cesar Otero
Tensegrity is a structural principle based on the use of isolated components in compression inside a net of continuous tension, in such a way that the compressed members (usually bars or struts) do not touch each other and the pre-stressed tensioned members (usually cables or tendons) delineate the system spatially.1 Compressed elements can, however, be contiguous as long as they are only and always pin jointed and under compression; in this case, it could be considered that there are not several simple elements under compression, but just one complex component constituted by an assembly of elementary elements in compression.2 When this happens, the class of tensegrity (k), the maximum number of struts meeting at one node, is said to be greater than one, that is, k > 1. In this paper, the latter definition of tensegrity has been adopted, as well as the tensegrities of any class (k = 1 and higher).