Simultaneous Optimization of Structure and Control of Smart Tensegrity Structures (original) (raw)
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Dynamic behavior and vibration control of a tensegrity structure
International Journal of Solids and Structures, 2010
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.
Dynamic analysis and vibration control of an active tensegrity structure
2009
Tensegrities are lightweight structures composed of cables and struts. Stability is provided by the self-stress state between tensioned and compressed elements. They present attractive solutions for controllable and smart structures as often small amounts of energy are needed to meet control requirements. Being lightweight structures, tensegrity systems are sensitive to dynamic loading. In spite of much research related to geometry, form-finding and architecture of tensegrity structures, few studies have focused on dynamic behavior and control. Also, few experimental studies have been observed to be of practical significance. Results are mainly tested numerically on small, simple and symmetrical tensegrity models. This paper extends ten years of research work on quasi-static control to perform dynamic analyses and study vibration control of a full-scale active tensegrity structure. Vibration modes of the structure are identified experimentally and compared with those determined thro...
Integrated Structure and Control Design of Modular Tensegrities
Proceedings of the 44th IEEE Conference on Decision and Control, 2005
This paper demonstrates a method for prestress optimization of tensegrity structures resulting in their optimal mixed dynamic and control performance. Prestress of a structure is parameterized using force-density variables that appear linearly in its linearized dynamic model. A feasible region for these parameters is defined in terms of the extreme directions of the prestress cone. A numerical method is proposed for computing this particular basis for the structure prestress cone. The problem is solved using a gradient method based on the sensitivity analysis. A numerical example of a cantilevered planar tensegrity beam is shown.
Self-stress design of tensegrity grid structures using genetic algorithm
International Journal of Mechanical Sciences, 2014
A numerical method is presented for the force identification of tensegrity grid structures according to external loads by using a force method combined with a genetic algorithm. The proposed method can find multiple initial self-stress modes by a diversity grouping. A genetic algorithm is used to uniquely define a single integral feasible set of initial self-stress for each case. Moreover the most critical member can be found by using the maximum value of self-stress mode scaling. Several numerical examples are presented to demonstrate the efficiency in determination of an initial integral feasible self-stress mode and its self-stress mode scaling for load-carrying capacity of tensegrity grid structures.
Multiobjective Hybrid Optimization–Antioptimization for Force Design of Tensegrity Structures
Journal of Applied Mechanics, 2012
Properties of Pareto optimal solutions considering bounded uncertainty are first investigated using an illustrative example of a simple truss. It is shown that the nominal values of the Pareto optimal solutions considering uncertainty are slightly different from those without considering uncertainty. Next a hybrid approach of multiobjective optimization and antioptimization is presented for force design of tensegrity structures. We maximize the lowest eigenvalue of the tangent stiffness matrix and minimize the deviation of forces from the specified target distribution. These objective functions are defined as the worst values due to the possible errors in the fabrication and construction processes. The Pareto optimal solutions are found by solving the two-level optimization–antioptimization problems using a nonlinear programming approach for the upper optimization problem and enumeration of the vertices of the uncertain region for the lower antioptimization problem.
Design of tensegrity structures using parametric analysis and stochastic search
Engineering With Computers, 2010
Tensegrity structures are lightweight structures composed of cables in tension and struts in compression. Since tensegrity systems exhibit geometrically nonlinear behavior, finding optimal structural designs is difficult. This paper focuses on the use of stochastic search for the design of tensegrity systems. A pedestrian bridge made of square hollow-rope tensegrity ring modules is studied. Two design methods are compared in this paper. Both methods aim to find the minimal cost solution. The first method approximates current practice in design offices. More specifically, parametric analysis that is similar to a gradient-based optimization is used to identify good designs. Parametric studies are executed for each system parameter in order to identify its influence on response. The second method uses a stochastic search strategy called probabilistic global search Lausanne. Both methods provide feasible configurations that meet civil engineering criteria of safety and serviceability. Parametric studies also help in defining search parameters such as appropriate penalty costs to enforce constraints while optimizing using stochastic search. Traditional design methods are useful to gain an understanding of structural behavior. However, due to the many local minima in the solution space, stochastic search strategies find better solutions than parametric studies.
Optimization of tensegrity structures
International Journal of Solids and Structures, 2006
This paper concerns the design of tensegrity structures with optimal mass-to-stiffness ratio. Starting from an initial layout that defines the largest set of allowed element connections, the procedure seeks the topology, geometry and prestress of the structure that yields optimal designs for different loading scenarios. The design constraints include strength constraints for all elements of the structure, buckling constraints for bars, and shape constraints. The problem formulation accommodates different symmetry constraints for structure parameters and shape. The static response of the structure is computed by using the nonlinear large displacement model. The problem is cast in the form of a nonlinear program. Examples show layouts of 2D and 3D asymmetric and symmetric structures. The influence of the material parameters on the optimal shape of the structure is investigated.
Analysis of Tensegric Structures by Total Potential Optimization Using Metaheuristic Algorithms
Journal of Aerospace Engineering, 29(5), 04016023, 2016
Tensile integrity (tensegrity, tensegric) structures are suggested for possible use in architectural works, bridges, covering large areas, and especially for habitats in outer space and on space bodies because of their minimal need for structural materials and ease of transfer and mounting. Structurally, their behavior is nonlinear and thus their analysis necessitates special care with recourse to special techniques. This study shows that their structural analysis can successfully be performed by a method called total potential optimization using meta-heuristic algorithms (TPO/MA) with no special precautions in a very general way. In the applications, which are conducted using software prepared for analyzing all types of nonlinear trusses and trusslike structures, the load-displacement behaviors of tensegric structures are investigated to include also the effect of prestressing level on cables. Genetic algorithms are used in this study as the metaheuristic technique for solving the optimization part of the problem.
Optimized Active Control of a Smart Cantilever Beam Using Genetic Algorithm
Designs
Vibration is one of the most dangerous phenomena that happens to a structure. It leads to premature fatigue and eventually failure, with potentially fatal consequences. A smart structure is an excellent solution to this problem; it adds an actuator, a sensor, and an appropriate control law to the system to reduce/eliminate the vibration. This study developed a complete analytical model for a cantilever beam with a collocated PZT sensor/actuator pair. First, we used a coupling of a collocated PZT sensor and an actuator to measure and control vibration levels based on a PID control law considering the physical constraints associated with PZT operation as the voltage level of the actuator. Next, the damping coefficient of the structure was determined by using genetic algorithms best fit to satisfy specific vibration conditions. Finally, we conducted a complete optimization for sensor/actuator position and PID parameters, using genetic algorithms. Thus, this paper gives a thorough under...
IEEE Access, 2021
The development of lightweight, stronger, and more flexible structures has received the utmost interest from many researchers. For this reason, piezoelectric materials, with their inherent electromechanical coupling, have been widely incorporated in the development of such structures to attenuate their vibrations. However, one of the main challenges is to find the optimal control and sensor-actuator placement. This paper presents an active vibration control for flexible structures, whereby a simply supported plate is taken as the benchmark model. A feedback controller with a collocated sensor-actuator configuration is used. Both disturbance and control signal acting on the plate is created by using piezoelectric (PZT) patches. The analytical model is derived based on the Euler-Bernoulli model. The Optimal location of the collocated sensor-actuator, as well as PID controller gains, are determined using Ant Colony Optimization (ACO) technique, then compared with the Genetic Algorithm ...