The Experts below are selected from a list of 2703 Experts worldwide ranked by ideXlab platform
Ian F C Smith - One of the best experts on this subject based on the ideXlab platform.
-
using dynamic measurements to detect and locate ruptured cables on a Tensegrity Structure
Engineering Structures, 2018Co-Authors: Ann Christine Sychterz, Ian F C SmithAbstract:Abstract Tensegrity Structures are cable-strut systems held in equilibrium due to self-stress. There is potential for damage tolerance when they are kinematically redundant. In this paper, detection and location of a ruptured cable in a deployable Tensegrity footbridge are studied through monitoring changes in dynamic behavior. Position values and axial load values of elements are measured before, during, and after a cable breakage. Free and forced-vibration-induced dynamic behavior of the Tensegrity Structure are characterized in the state of deployment (one half of the Structure) and in-service (full Structure). Examination of ambient vibrations for the half Structure and forced vibrations for the full Structure successfully led to detection of ruptured cables. Exclusion of possible damage cases for location using measurements effectively reduces the number of candidate cases when using nodal displacement measurements. Correlation methods using strain measurements are also successful to locate a ruptured cable. These methods reveal the potential for self-diagnosis of complex sensed Structures.
-
deployment and shape change of a Tensegrity Structure using path planning and feedback control
Frontiers in Built Environment, 2018Co-Authors: Ann Christine Sychterz, Ian F C SmithAbstract:Tensegrity Structures are pin-jointed assemblies of struts and cables that are held together in a stable state of stress. Shape control is a combination of control-commands with measurements to achieve a desired form. Applying shape control to a near-full-scale deployable Tensegrity Structure presents a rare opportunity to analytically and experimentally study and control the effects of large shape changes on a closely coupled multi-element system. Simulated cable-length changes provide an initial activation plan to reach an effective sequence for self-stress. Controlling internal forces is more sensitive than controlling movements through cable-length changes; internal force-control is thus a better objective than movement-control for small adjustments to the Structure. The deployment of a Tensegrity Structure in previous work was carried out using predetermined commands. In this paper, two deployment methods and a method for self-stress are presented. The first method uses feedback cycles to increase speed of deployment compared with implementation of empirically predetermined control-commands. The second method consists of three parts starting with a path-planning algorithm that generates search trees at the initial point and the target point using a greedy algorithm to create a deployment trajectory. Collision and overstress avoidance for the deployment trajectory involve checks of boundaries defined by positions of struts and cables. Even actuator deployment followed by commands obtained from a search algorithm results in the successful connection of the Structure at midspan. Once deployment at midspan is achieved by either method, a self-stress algorithm is implemented to correct the position and element forces in the Structure to the design configuration prior to in-service loading. Modification of deployment control-commands using the feedback method (with twenty cycles) compared with empirically predetermined control-commands successfully provides a more efficient deployment trajectory prior to midspan connection with up to 50% reduction in deployment time. The path-planning method successfully enables deployment and connection at midspan with a further time reduction of 68% compared with the feedback method (with twenty cycles). The feedback control, the path-planning method and the soft-constraint algorithm successfully lead to efficient deployment and preparation for service loading. Advanced computing algorithms have potential to improve the efficiency of complex deployment.
-
Deployment and Shape Change of a Tensegrity Structure Using Path-Planning and Feedback Control
Frontiers Media S.A., 2018Co-Authors: Ann C. Sychterz, Ian F C SmithAbstract:Tensegrity Structures are pin-jointed assemblies of struts and cables that are held together in a stable state of stress. Shape control is a combination of control-commands with measurements to achieve a desired form. Applying shape control to a near-full-scale deployable Tensegrity Structure presents a rare opportunity to analytically and experimentally study and control the effects of large shape changes on a closely coupled multi-element system. Simulated cable-length changes provide an initial activation plan to reach an effective sequence for self-stress. Controlling internal forces is more sensitive than controlling movements through cable-length changes; internal force-control is thus a better objective than movement-control for small adjustments to the Structure. The deployment of a Tensegrity Structure in previous work was carried out using predetermined commands. In this paper, two deployment methods and a method for self-stress are presented. The first method uses feedback cycles to increase speed of deployment compared with implementation of empirically predetermined control-commands. The second method consists of three parts starting with a path-planning algorithm that generates search trees at the initial point and the target point using a greedy algorithm to create a deployment trajectory. Collision and overstress avoidance for the deployment trajectory involve checks of boundaries defined by positions of struts and cables. Even actuator deployment followed by commands obtained from a search algorithm results in the successful connection of the Structure at midspan. Once deployment at midspan is achieved by either method, a self-stress algorithm is implemented to correct the position and element forces in the Structure to the design configuration prior to in-service loading. Modification of deployment control-commands using the feedback method (with twenty cycles) compared with empirically predetermined control-commands successfully provides a more efficient deployment trajectory prior to midspan connection with up to 50% reduction in deployment time. The path-planning method successfully enables deployment and connection at midspan with a further time reduction of 68% compared with the feedback method (with twenty cycles). The feedback control, the path-planning method and the soft-constraint algorithm successfully lead to efficient deployment and preparation for service loading. Advanced computing algorithms have potential to improve the efficiency of complex deployment challenges
-
adaptive control of a deployable Tensegrity Structure
Engineering Structures, 2017Co-Authors: Nicolas Veuve, Ann Christine Sychterz, Ian F C SmithAbstract:Abstract Deployable Structures belong to a special class of moveable Structures that are capable of form and size change. Controlling movement of deployable Structures is important for successful deployment, in-service adaptation and safety. In this paper, measurements and control methodologies contribute to the development of an efficient learning strategy and a damage-compensation algorithm for a deployable Tensegrity Structure. The general motivation of this work is to develop an efficient bio-inspired control framework through real-time measurement, adaptation, and learning. Building on previous work, an enhanced deployment algorithm involves re-use of control commands in order to reduce computation time for mid-span connection. Simulations are integrated into a stochastic search algorithm and combined with case-reuse as well as real-time measurements. Although data collection requires instrumentation, this methodology performs significantly better than without real-time measurements. This paper presents the procedure and generally applicable methodologies to improve deployment paths, to control the shape of a Structure through optimization, and to control the Structure to adapt after a damage event.
-
dynamic behavior and vibration control of a Tensegrity Structure
International Journal of Solids and Structures, 2010Co-Authors: Bel Hadj N Ali, Ian F C SmithAbstract:Tensegrities are lightweight space reticulated Structures composed of cables and struts. Stability is provided by the self-stress state between tensioned and compressed elements. Tensegrity systems have in general low structural damping, leading to challenges with respect to dynamic loading. This paper describes dynamic behavior and vibration control of a full-scale active Tensegrity Structure. Laboratory testing and numerical simulations confirmed that control of the self-stress influences the dynamic behavior. A multi-objective vibration control strategy is proposed. Vibration control is carried out by modifying the self-stress level of the Structure through small movement of active struts in order to shift the natural frequencies away from excitation. The PGSL stochastic search algorithm successfully identifies good control commands enabling reduction of structural response to acceptable levels at minimum control cost.
Klaus Zimmermann - One of the best experts on this subject based on the ideXlab platform.
-
Kinematic analysis of a rolling Tensegrity Structure with spatially curved members
Meccanica, 2020Co-Authors: Philipp Schorr, Lena Zentner, Klaus Zimmermann, Enrique Roberto Carrillo Li, Tobias Kaufhold, Jorge Antonio Rodríguez Hernández, Valter BöhmAbstract:In this work, a Tensegrity Structure with spatially curved members is applied as rolling locomotion system. The actuation of the Structure allows a variation of the originally cylindrical shape to a conical shape. Moreover, the Structure is equipped with internal movable masses to control the position of the center of mass of the Structure. To control the locomotion system a reliable actuation strategy is required. Therefore, the kinematics of the system considering the nonholonomic constraints are derived in this paper. Based on the resulting insight in the locomotion behavior a feasible actuation strategy is designed to control the trajectory of the system. To verify this approach kinematic analyses are evaluated numerically. The simulation data confirm the path following due to an appropriate shape change of the Tensegrity Structure. Thus, this system enables a two-dimensional rolling locomotion.
-
multi mode motion system based on a multistable Tensegrity Structure
IFToMM World Congress on Mechanism and Machine Science, 2019Co-Authors: Philipp Schorr, Lena Zentner, Valter Böhm, G Stepan, Klaus ZimmermannAbstract:This paper presents a multi-mode motion system based on a compliant Tensegrity Structure with multiple stable equilibrium configurations. The motion system is in contact to an arbitrarily shaped rigid ground due to gravity. The movement is realized by changing successively between different equilibrium states. Depending on the strategy of changing the equilibrium configuration, different motion types occur. The reachable area of the motion system can be enlarged by adapting the motion type depending on the given environmental characteristics. Furthermore, the efficiency of the motion can be improved by choosing the most suitable motion mode. Theoretical studies regarding the change of the equilibrium states are introduced. Moreover, simulation results for the different motion modes tilting, vibration driven and jumping are illustrated. The resulting motion characteristics emphasize the advantageous adaptability of the motion system regarding to varying environmental conditions.
-
design of a vibration driven motion system based on a multistable Tensegrity Structure
International Conference on Informatics in Control Automation and Robotics, 2018Co-Authors: Philipp Schorr, Lena Zentner, Valter Böhm, Klaus ZimmermannAbstract:In this paper a novel approach to realize a uniaxial bidirectional vibration driven motion system with controllable direction of motion is investigated. The considered motion system bases on a Tensegrity Structure with multiple stable equilibrium configurations. The Structure is in contact with a horizontal plane due to gravity and the actuation is realized by the harmonic change of the length of a selected member. Beside varying the actuation parameters, the direction of motion can be controlled by changing the equilibrium configuration of the Tensegrity Structure. In this paper the topology of the Tensegrity Structure and the parameter values are chosen appropriately to provide two symmetric equilibrium configurations. A change of the equilibrium state yields a novel configuration of the entire motion system which is symmetric to the original state. Utilizing the symmetry of the system the same actuation yields an opposite motion. This approach represents a reliable opportunity to control the direction of motion by changing the equilibrium state for constant actuation parameters. This paper focuses on the parameter selection and the design of the actuation of the vibration driven motion system. The working principle of the vibration driven motion system is verified by numerical simulations. This contribution represents the theoretical investigation for the further development of a prototype.
-
Motion characteristics of a vibration driven mobile Tensegrity Structure with multiple stable equilibrium states
Journal of Sound and Vibration, 2018Co-Authors: Philipp Schorr, V. Böhm, Lena Zentner, Klaus ZimmermannAbstract:Abstract A novel type of a vibration driven motion system based on a compliant Tensegrity Structure with multiple stable equilibrium states is considered. These equilibrium configurations correspond to different prestress states with different dynamical properties. Therefore, the motion characteristics can be varied by changing the equilibrium state. For the application in the fields of mobile robotics, these discrete adjustable dynamics are advantageous. The vibration modes of the Structure as well as the corresponding motion characteristics of the system can be adapted to the given environmental conditions in order to ensure a reliable motion. In this paper, dynamical investigations of an exemplary two-dimensional multistable Tensegrity Structure are considered. For the chosen parameter values the Structure features two relevant equilibrium configurations. The resulting motion system is in contact to a horizontal plane due to gravity and the actuation is realized by the harmonic variation of the length of a single tensioned member. The motion of the system is simulated for various actuation frequencies with the different equilibrium states as an initial configuration. A uniaxial or a planar movement occurs depending on the selection of the actuated member within the Tensegrity Structure. The steady state motion is evaluated regarding motion characteristics like the steady state velocity. Moreover, the influences on the motion behavior caused by the different equilibrium states as an initial condition are emphasized.
-
dynamic analysis of a compliant Tensegrity Structure for the use in a gripper application
Dynamical Systems Theory and Applications, 2017Co-Authors: Susanne Sumi, Philipp Schorr, Valter Böhm, Klaus ZimmermannAbstract:The use of compliant Tensegrity Structures in robotic applications offers several advantageous properties. In this work the dynamic behaviour of a planar Tensegrity Structure with multiple static equilibrium configurations is analysed, with respect to its further use in a two-finger-gripper application. In this application, two equilibrium configurations of the Structure correspond to the opened and closed states of the gripper. The transition between these equilibrium configurations, caused by a proper selected actuation method, is essentially dependent on the actuation parameters and on the system parameters. To study the behaviour of the dynamic system and possible actuation methods, the nonlinear equations of motion are derived and transient dynamic analyses are performed. The movement behaviour is analysed in relation to the prestress of the Structure and actuation parameters.
Valter Böhm - One of the best experts on this subject based on the ideXlab platform.
-
Kinematic analysis of a rolling Tensegrity Structure with spatially curved members
Meccanica, 2020Co-Authors: Philipp Schorr, Lena Zentner, Klaus Zimmermann, Enrique Roberto Carrillo Li, Tobias Kaufhold, Jorge Antonio Rodríguez Hernández, Valter BöhmAbstract:In this work, a Tensegrity Structure with spatially curved members is applied as rolling locomotion system. The actuation of the Structure allows a variation of the originally cylindrical shape to a conical shape. Moreover, the Structure is equipped with internal movable masses to control the position of the center of mass of the Structure. To control the locomotion system a reliable actuation strategy is required. Therefore, the kinematics of the system considering the nonholonomic constraints are derived in this paper. Based on the resulting insight in the locomotion behavior a feasible actuation strategy is designed to control the trajectory of the system. To verify this approach kinematic analyses are evaluated numerically. The simulation data confirm the path following due to an appropriate shape change of the Tensegrity Structure. Thus, this system enables a two-dimensional rolling locomotion.
-
multi mode motion system based on a multistable Tensegrity Structure
IFToMM World Congress on Mechanism and Machine Science, 2019Co-Authors: Philipp Schorr, Lena Zentner, Valter Böhm, G Stepan, Klaus ZimmermannAbstract:This paper presents a multi-mode motion system based on a compliant Tensegrity Structure with multiple stable equilibrium configurations. The motion system is in contact to an arbitrarily shaped rigid ground due to gravity. The movement is realized by changing successively between different equilibrium states. Depending on the strategy of changing the equilibrium configuration, different motion types occur. The reachable area of the motion system can be enlarged by adapting the motion type depending on the given environmental characteristics. Furthermore, the efficiency of the motion can be improved by choosing the most suitable motion mode. Theoretical studies regarding the change of the equilibrium states are introduced. Moreover, simulation results for the different motion modes tilting, vibration driven and jumping are illustrated. The resulting motion characteristics emphasize the advantageous adaptability of the motion system regarding to varying environmental conditions.
-
design of a vibration driven motion system based on a multistable Tensegrity Structure
International Conference on Informatics in Control Automation and Robotics, 2018Co-Authors: Philipp Schorr, Lena Zentner, Valter Böhm, Klaus ZimmermannAbstract:In this paper a novel approach to realize a uniaxial bidirectional vibration driven motion system with controllable direction of motion is investigated. The considered motion system bases on a Tensegrity Structure with multiple stable equilibrium configurations. The Structure is in contact with a horizontal plane due to gravity and the actuation is realized by the harmonic change of the length of a selected member. Beside varying the actuation parameters, the direction of motion can be controlled by changing the equilibrium configuration of the Tensegrity Structure. In this paper the topology of the Tensegrity Structure and the parameter values are chosen appropriately to provide two symmetric equilibrium configurations. A change of the equilibrium state yields a novel configuration of the entire motion system which is symmetric to the original state. Utilizing the symmetry of the system the same actuation yields an opposite motion. This approach represents a reliable opportunity to control the direction of motion by changing the equilibrium state for constant actuation parameters. This paper focuses on the parameter selection and the design of the actuation of the vibration driven motion system. The working principle of the vibration driven motion system is verified by numerical simulations. This contribution represents the theoretical investigation for the further development of a prototype.
-
dynamic analysis of a compliant Tensegrity Structure for the use in a gripper application
Dynamical Systems Theory and Applications, 2017Co-Authors: Susanne Sumi, Philipp Schorr, Valter Böhm, Klaus ZimmermannAbstract:The use of compliant Tensegrity Structures in robotic applications offers several advantageous properties. In this work the dynamic behaviour of a planar Tensegrity Structure with multiple static equilibrium configurations is analysed, with respect to its further use in a two-finger-gripper application. In this application, two equilibrium configurations of the Structure correspond to the opened and closed states of the gripper. The transition between these equilibrium configurations, caused by a proper selected actuation method, is essentially dependent on the actuation parameters and on the system parameters. To study the behaviour of the dynamic system and possible actuation methods, the nonlinear equations of motion are derived and transient dynamic analyses are performed. The movement behaviour is analysed in relation to the prestress of the Structure and actuation parameters.
-
indoor locomotion experiments of a spherical mobile robot based on a Tensegrity Structure with curved compressed members
International Conference on Advanced Intelligent Mechatronics, 2017Co-Authors: Tobias Kaufhold, Valter Böhm, Florian Schale, Klaus ZimmermannAbstract:This work presents theoretical and experimental investigations on an untethered rolling Tensegrity robot. Previous research has shown, that rolling locomotion of compliant Tensegrity robots can be realized without change of their shape, by using only internal mass shifting. The use of simple Tensegrity Structures, based on curved compressed members enables pure rolling locomotion in contrast to the most known prototypes of this kind. Therefore, theoretical and experimental investigations of an untethered locomotion system based on a simple Tensegrity Structure, consisting of two disconnected compressed curved members connected to a continuous net of twelve prestressed tensioned members with pronounced elasticity, are considered. Planar locomotion is induced by the movement of only two drive units as internal masses along the curved compressed members. Theoretical considerations show the influence of the geometrical system parameters on the movement behavior of the system. With the help of experimental investigations, by using motion-capturing technique, main properties of the locomotion performance of a prototype are discussed.
Shinichi Hirai - One of the best experts on this subject based on the ideXlab platform.
-
crawling by body deformation of Tensegrity Structure robots
International Conference on Robotics and Automation, 2009Co-Authors: Mizuho Shibata, Fumio Saijyo, Shinichi HiraiAbstract:In this paper, we describe the design of a deformable robot with a Tensegrity Structure that can crawl and we show the results of experiments showing the ability of these robots to crawl. We first describe a Tensegrity Structure, composed of struts and cables, and its characteristics. We next explain the principle of crawling by robot body deformation, followed by a classification of the methods by which a body can be deformed and the contact conditions of the robot through the cable-graph of the Tensegrity Structure. We also describe topological transition graphs that can visualize crawling from each initial contact condition. We then discuss the characteristics of the proposed robot in terms of design freedom. Finally, we show experimentally that the prototype of a Tensegrity robot can crawl.
-
ICRA - Crawling by body deformation of Tensegrity Structure robots
2009 IEEE International Conference on Robotics and Automation, 2009Co-Authors: Mizuho Shibata, Fumio Saijyo, Shinichi HiraiAbstract:In this paper, we describe the design of a deformable robot with a Tensegrity Structure that can crawl and we show the results of experiments showing the ability of these robots to crawl. We first describe a Tensegrity Structure, composed of struts and cables, and its characteristics. We next explain the principle of crawling by robot body deformation, followed by a classification of the methods by which a body can be deformed and the contact conditions of the robot through the cable-graph of the Tensegrity Structure. We also describe topological transition graphs that can visualize crawling from each initial contact condition. We then discuss the characteristics of the proposed robot in terms of design freedom. Finally, we show experimentally that the prototype of a Tensegrity robot can crawl.
Robert E. Skelton - One of the best experts on this subject based on the ideXlab platform.
-
integrating mass and control energy optimization for Tensegrity Structure
International Conference on Intelligent Control and Information Processing, 2011Co-Authors: Robert E. Skelton, Jie YanAbstract:This paper presents a Tensegrity Structure optimization approach which minimizes the control energy and Structure material volume at the same time. Firstly we formulate the dynamic model for Class 1 and Class 2 systems, and based on the nonlinear model we derive the linearized model for Class 1 system. Then using this model we solve the Information Architecture problem for different complexity Structures. Based on multiple constrains, an integrated algorithm is presented to optimize the mass, price and control energy simultaneously. At last we use T-Bar Structure as an example, and it shows us that the proposed algorithm works well.
-
Energy optimization of deployable Tensegrity Structure
Proceedings of the 30th Chinese Control Conference, 2011Co-Authors: Qiang Li, Robert E. SkeltonAbstract:This paper presents a numerical method to design a Tensegrity Structure which can deploy itself to a desired shape and cost the minimal energy. Starting from the dynamic model in matrix the static model in vector form which is easy to solve the force density is deduced. The self-deploy control problem is described as a math model by using this new vector model and the condition whether there exists a solution is given out. Projection algorithm is adopted to get the optimal solution. The optimization method investigated is applied to two examples and simulation results demonstrate that the theory works well.
-
CDC - Regenerative Tensegrity Structures for Energy Harvesting Applications
Proceedings of the 45th IEEE Conference on Decision and Control, 2006Co-Authors: Jeffrey T. Scruggs, Robert E. SkeltonAbstract:This paper investigates the potential of controlled Tensegrity Structures as a means for electrically generating and storing energy injected into the Structure by external disturbances. An approach is presented for the integration of linear, regenerative actuators into Tensegrity Structures as supplemental active bars. By operating these actuators as generators, mechanical energy absorbed from the Structure during periods of external excitation is converted to electrical energy. Through proper control of the power-electronic network to which the actuators are connected, a fraction of this energy may be recovered and delivered to a storage system or an external power grid. A generalized model for a regenerative Tensegrity Structure with arbitrarily-many actuators is presented, which accounts for electrical dissipation in the actuators and associated electronics. Issues pertaining to actuator selection and power-electronic control are discussed. An approach is presented for the design of simple collocated linear velocity-feedback controllers for systems with one actuator, such that the rate of structural energy extraction is optimized for the steady-state closed-loop response to an external disturbance. The approach is illustrated in a simulation example for a small-scale system. Extensions are discussed in which a regenerative Tensegrity Structure is used to harvest energy from the motion of ocean waves.
-
active vibration control of a three stage Tensegrity Structure
Smart Structures and Materials 2004: Damping and Isolation, 2004Co-Authors: Waileung Chan, D Arbelaez, Frederic Bossens, Robert E. SkeltonAbstract:This experimental study demonstrates the efficiency of simple control strategies to damp a 3-stage Tensegrity tower Structure. The tower is mounted on a moving support which is excited with a limited bandwidth random signal (filtered white noise) by a shaker. Our goal is to minimize the tansmissibility between base acceleration and top plate acceleration using piezoelectric displacement actuators and force sensors collocated at the bottom stage of vertical strings. Two types of controllers have been designed, namely, it local integral force feedback control and acceleration feedback control. It can be shown that both controllers can effectively damp the first 2 bending modes by about 20 dB, and the acceleration feedback controller performs even better as it can also reduce the amplitude of the next 2 bending modes by about 5-10 dB.
-
equilibrium conditions of a Tensegrity Structure
International Journal of Solids and Structures, 2003Co-Authors: D Williamson, Robert E. Skelton, Jeongheon HanAbstract:This paper characterizes the necessary and sufficient conditions for Tensegrity equilibria. Static models of Tensegrity Structures are reduced to linear algebra problems, after first characterizing the problem in a vector space where direction cosines are not needed. This is possible by describing the components of all member vectors. While our approach enlarges (by a factor of 3) the vector space required to describe the problem, the advantage of enlarging the vector space makes the mathematical Structure of the problem amenable to linear algebra treatment. Using the linear algebraic techniques, many variables are eliminated from the final existence equations.
