Morphological communication: exploiting coupled dynamics in a complex mechanical structure to achieve locomotion

Traditional engineering approaches strive to avoid, or actively suppress, nonlinear dynamic coupling among components. Biological systems, in contrast, are often rife with these dynamics. Could there be, in some cases, a benefit to high degrees of dynamical coupling? Here we present a distributed robotic control scheme inspired by the biological phenomenon of tensegrity-based mechanotransduction. This emergence of morphology-as-information-conduit or ‘morphological communication’, enabled by time-sensitive spiking neural networks, presents a new paradigm for the decentralized control of large, coupled, modular systems. These results significantly bolster, both in magnitude and in form, the idea of morphological computation in robotic control. Furthermore, they lend further credence to ideas of embodied anatomical computation in biological systems, on scales ranging from cellular structures up to the tendinous networks of the human hand

A comprehensive dynamic model for class-1 tensegrity systems based on quaternions

In this paper we propose a new dynamic model, based on quaternions, for tensegrity systems of class-1. Quaternions are used to represent orientations of a rigid body in the 3-dimensional space eliminating the problem of singularities. Moreover, the equations based on quaternions allow to perform more precise calculations and simulations because they do not use trigonometric functions for the representation of angles. We present a thorough introduction of tensegrities and the current state of research. We also introduce the quaternions and provide in the appendix some important details and useful properties. Applying the Euler–Lagrange approach we derive a comprehensive dynamic model, first for a simple rigid bar in the space and, at last, for a class-1 tensegrity system. We present two model forms: a matrix and a vectorial form. The first more compact and easier to write, the latter more suitable to apply the tools and the theory based on vector fields.Postprint (author’s final draft

WAVE PROPAGATION IN TENSEGRITY AND PERIODIC STRUCTURES

This dissertation focuses on the development of the fundamental understanding of the dynamic behavior of assemblies of periodic arrays of tensegrity unit cells (along one and two directions). The ultimate aim of the dissertation is to capitalize on the attractive attributes of tensegrity structures with the unique characteristics of periodic structures, which stem from their ability to impede the propagation of disturbances that fall within certain frequency bands (known as stop bands or bandgaps). A successful implementation of such periodic/tensegrity structures is envisioned to extend the usefulness of tensegrity to vibration isolation problems, as well as to the synthesis of tunable acoustic and elastic wave filters, in both the frequency and spatial domains. In this dissertation, numerical analysis of the statics and kinematics of icosahedron tensegrity cells are developed. The developed relationships are utilized to conceive one- and two-dimensional periodic arrays by appropriate stacking of icosahedron tensegrity cells. Alternative configurations for the periodic tensegrity arrays are considered for improved band gap characteristics, and a novel design for a periodic, tensegrity-based damper/vibration isolator is presented and demonstrated. Particular emphasis is placed here on investigating and demonstrating some of the very interesting elastic properties of the periodic/tensegrity structures. Among these properties is the ratio of the bulk modulus to the shear modulus which are shown to be on the order of 1000. These values are two orders of magnitude higher than any naturally-occurring bulk material, suggesting that the viable potential of the periodic/tensegrity structures as suitable candidates for the synthesis of practical and realizable “pentamode” metamaterials, with many potential applications in the novel areas of acoustic and elastic cloaking where the proposed periodic/tensegrity structures act as liquids to ensure proper impedance matching

Ein Beitrag zur Entwicklung mobiler Roboter basierend auf multistabilen Tensegrity Strukturen

In dieser Arbeit wird die Anwendung von Tensegrity Strukturen mit mehreren stabilen Gleichgewichtskonfigurationen zur Realisierung von Lokomotionssystemen in der mobilen Robotik untersucht. Diese Strukturen werden unter dem mechanischen Aspekt modelliert und verschiedene Aktuatorstrategien zur Realisierung eines kontrollierten Wechsels zwischen den unterschiedlichen stabilen Gleichgewichtslagen abgeleitet. Zur experimentellen Verifikation der theoretischen Ansätze wird ein Prototyp einer multistabilen Tensegrity Struktur entwickelt. Die experimentellen Ergebnisse bestätigen die vorteilhaften Eigenschaften multistabiler Tensegrity Strukturen sowie die Möglichkeit von kontrollierten Konfigurationswechseln. Infolge von Erweiterungen des mechanischen Modells unter Berücksichtigung von Umwelteinflüssen wird das Bewegungsverhalten von Tensegrity Strukturen simuliert. In dieser Arbeit wird die Fortbewegung durch die Gleichgewichtslagenwechsel der multistabilen Tensegrity Struktur realisiert. Abhängig von der gewählten Aktuierungsstragie kann eine schreitende Lokomotion, eine kriechende Lokomotion sowie eine springende Lokomotion realisiert werden. Experimente mit dem entwickelten Prototyp bestätigen die zuvor untersuchten Lokomotionsformen. Durch Kombination der verschiedenen Bewegungsmodi resultiert ein multimodales Lokomotionssystem. Dieses Lokomotionssystem erlaubt die Anpassung des Lokomotionsprinzips hinsichtlich der gegebenen Umgebungsbedingungen.In this work, tensegrity structures with multiple stable equilibrium configurations are investigated to develop locomotion systems in the fields of mobile robotics. These structures are modeled from the mechanical point of view and various actuation strategies to realize a controllable change between the different stable equilibrium states are derived. A prototype of a multistable tensegrity structure is developed to verify the theoretical approaches experimentally. The experimental results confirm the advantageous properties of multistable tensegrity structures and the possibility to change the configuration in a controllable manner. Due to extensions of the mechanical model considering environmental influences, the motion behavior of tensegrity structures is simulated. In this work, the locomotion is realized by changing between the stable equilibrium configurations of the multistable tensegrity structure. Various actuation strategies yield a tilting locomotion, a crawling locomotion and a jumping locomotion. Experiments with the developed prototype confirm the different locomotion types. A multimodal locomotion system is derived by combining the various locomotion modes. This system allows the adaptation of the locomotion principle with regard to the given environmental conditions.In dieser Arbeit wird die Anwendung von Tensegrity Strukturen mit mehreren stabilen Gleichgewichtskonfigurationen zur Realisierung von Lokomotionssystemen in der mobilen Robotik untersucht. Diese Strukturen werden unter dem mechanischen Aspekt modelliert und verschiedene Aktuatorstrategien zur Realisierung eines kontrollierten Wechsels zwischen den unterschiedlichen stabilen Gleichgewichtslagen abgeleitet. Es wird ein Prototyp einer multistabilen Tensegrity Struktur entwickelt und dessen Bewegungsverhalten simuliert. Abhängig von der gewählten Aktuierungsstrategie kann eine schreitende Lokomotion, eine kriechende Lokomotion sowie eine springende Lokomotion realisiert werden. Experimente mit dem Prototyp bestätigen diese Lokomotionsformen. Durch Kombination der verschiedenen Bewegungsmodi resultiert ein multimodales Lokomotionssystem. Dieses Lokomotionssystem erlaubt die Anpassung des Lokomotionsprinzips hinsichtlich der gegebenen Umgebungsbedingungen