Structural design and optimization of large cable–rib tension deployable antenna structure with dynamic constraint

Packing optimization and design of the deployable parabolic rigid antenna based on origami

A technique is introduced for the kinematic synthesis of deployable cable-stiffened truss structures. This technique, which is an extension of a prior procedure [l-21 for generating deployable truss structures, can be applied to generate all concepts of cable-stiffened truss structures as well as all their deployable derivatives. Examples illustrating the implementation of this new technique, along with a discussion of the results achieved. are included in this article. The primary function of a deployable structure is to maintain a stable configuration in its deployed state. This is reflected in current design practices of trading off decreased deployment or retraction performance for increased structural performance. As a result, various designs of deployable truss structures (with, and without cables) have been introduced that are over-constrained during deployment/retraction, i.e. deployment/retraction of these structures can only be achieved through the deformation of individual links or by exploiting symmetric features of the structure. The number of different conceptual designs of deployable structures that are based on a given structural configuration is unlimited, if deployable structures are permitted to be overconstrained during deploymenthetraction. For this reason, researchers in the area of deployable structures have given little attention to the systematic design of deployable truss structures and have instead devoted much of their attention to the introduction and discussion of novel concepts of deployable truss structures [3-171. If, on the other hand, it is assumed that the primary function of a deployable structure is to serve as a mechanism with a minimum number (i.e. at least one) of degrees-of-freedom, then the number of different conceptual designs that are based on a given structural configuration is finite. Hence, it is then possible to generate all possible designs for a given structural configuration. The assumption that a deployable structure is not constrained during deployment/retraction has enabled the development of a technique for the generation of all conceptual designs of deployable truss structures that can be used as building blocks (modules) of much larger structures [I-21. It should be noted that this technique, referred to as kinematic synthesis of * Sr. Mechanical Engineer, Member AIAA deployable structures, does not assume that the structural configuration is known but instead uses the characteristics of a given class of structures (i.e. truss modules) to generate all possible configurations of structures in this class. The limitation of this technique to truss modules has been avoided in the Explosion-Implosion technique [19], developed by the same authors, for the generation of allconceptual designs of deployable truss structures of which the locations of the nodes are known. Both techniques have been shown to result in the generation of an enormous, yet finite, number of novel conceptual designs as well as those that have been reported in the literature. Furthermore, by limiting the degrees-of-freedom available at individual joints, conceptual designs can be generated of deployable structures that are overconstrained during deployment/retraction. Although the kinematic synthesis technique and the explosionimplosion technique result in the generation of an enormous number of conceptual designs of deployable truss structures, they are not applicable to truss structures with cables. Yet, cable-stiffened truss structures have important advantages such as the reduction in mass and/or reduction in joints that can be achieved by replacing links in truss structures with cables. The objective of this article is to modify the technique introduced in [I-21 such that the new technique is also applicable to cablestiffened truss structures. This new approach can then be applied to generate novel concepts of deployablecable-stiffened truss structures as well as those that have been reported in the literature.

Large deployable membrane diffraction antenna plays a significant role in achieving high-precision remote sensing detection in the future owing to its super large aperture. In order to accurately adjust and maintain the primary mirror surface of the deployable diffraction antenna, a novel scheme of surface shape control has been proposed in this paper. In the scheme, the large deployable antenna is divided into several mirror units and each mirror unit is spread by braced frames. Besides, the membrane mounting units are controlled by six actuators with 6 degrees of freedom. The actuators which are low cost and applicable in complex environment are developed according to relevant control requirements. The designed actuators have the advantages of wide adjustable range (up to 21mm) and high precision (better than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.16\mu m$</tex> ), which is much better than the traditional piezoelectric actuator scheme, and the cost performance is higher than the adjustment scheme of optical telescope. Finally, the simulation results demonstrate the feasibility of the proposed control scheme. The performances of the actuators are displayed by experimental tests.

Dynamic performance prediction of an annular tensegrity structure based on similitude method

Large deployable hoop-truss antennas are widely used in satellite communication systems for their high antenna gain and small packed volume. Knowledge of the deployment dynamics of the large deployable hoop-truss antenna and its coupling with spacecraft attitude motion are essential for the design of deployment mechanisms and attitude control systems. In this paper, a spacecraft with two flexible solar panels, which are reduced by Craig–Bampton component modal synthesis, is modeled by natural coordinate formulation. A large deployable hoop-truss antenna is modeled with the absolute nodal coordinate formulation. Both lead to a constant-mass matrix without the centrifugal and Coriolis forces. The whole dynamics model is used to solve the attitude and the reaction moment during the deployment process. Nonsynchronous deployment phenomena due to the structural flexibility and the decay of the driving force are investigated, and results show that these phenomena can increase the stresses suffered by the hoop truss, which should be considered in the design of a large deployable hoop-truss antenna.

It is nearly impossible to carry out prototype experiments of large deployable space antennas because of their large dimensions. To solve this problem, a performance prediction approach is proposed in this paper. The prototype’s working performance is predicted by the scale model of the large deployable antenna. Based on this method, the natural frequency of the ring tension truss deployable antenna working in space is studied. The effect of the structural parameter distortion is taken into consideration by similarity criteria, and a similarity experimental formula of structural natural frequency is obtained. Four finite element models are established to validate the correction of the prediction method. The simulation results show that it’s valid for the prediction method to analyze the prototype in space, and it can be applied to promote the design, and performance prediction of the large deployable antennas.

During the last 20 years, structural optimization has become one of the most important topics of engineering applications. Design optimization of structure has been an interesting area of research in the field of engineering design for its ability to short the design cycle and to enhance product quality. Significant research activity has occurred in the area of structural optimization in the last decade. Especially for topology optimization of structure, many new theoretical, algorithmic, and computational contributions have resulted by researchers and engineers. Topology optimization is a powerful tool for global and multi-scale design of macrostructures, microstructures, and the cell of prescribed composite materials. The population based evolutionary algorithms have emerged as powerful mechanism for finding optimum solutions of complex optimization problems in engineering during the last two decades. Evolutionary computation is the study of computational systems which use ideas and get inspiration from natural evolution and adaptation [1]. The thinking has wide application in various engineering fields, such as computer science, artificial intelligence, operations research. Genetic algorithm is another kind of bio-inspired optimization method and it is playing an increasingly important role in studies of complex adaptive systems. Its application ranges from adaptive agents in economic theory to the use of machine learning techniques in the design of complex devices and structures, such as aircraft turbines and integrated circuits [2]. Optimization of structures can be classified into three categories: sizing, shaping, and topology optimization. In the topology optimization, it is concerned with the structure members and connectivity between members. In general, it is easily represented by discrete variables rather than by those used for continuous optimization problems. Topology optimization is the most difficult and complex among three categories and it is special useful in developing innovative conceptual designs. Structural optimization, in particular the topology optimization, has been identified as one of the most challenging tasks in structural design. Various techniques and approaches have been established during the last two decades. Topology optimization usually referred to as layout optimization or general shape optimization [3]. It lets engineers get the optimal topology of structure or new configurations during product design phase, as they are implementing the design of the size

The inter-connectivity and type selection of joints in a mechanism can be represented by a graph. In this article a technique is presented for the generation of such a graph for a (spatial) deployable truss structure. First a fundamental graph is constructed which reveals all possible joint connections in a deployable structure. This graph, which can be derived from the geometry of a deployable structure, is then reduced to the graph of the kinematic structure (revealing the joint inter-connectivity) by applying a set of rules. The process of joint specification is completed by assigning joint types to edges in the graph such that the required mobility of the deployable structure it represents is ensured. Procedures are provided that incorperate the techniques introduced in this article and which can be used to generate all possible joint assignments for a given deployable structure.

Early attempts of optimised structural designs go back to the 1600s, when Leonardo da Vinci and Galileo conducted tests of models and full-scale structures [1]. A 1994`s review of structural optimization can be found in the study by Cohn and Dinovitzer [2], who pointed out that there was a gap between theoretical studies and the practical application in practice. They also noted the short number of studies that concentrated on concrete structures. A review of structural concrete optimization can be found in the 1998`s study by Sarma and Adeli [3]. The methods of structural optimization may be classified into two broad groups: exact methods and heuristic methods. The exact methods are the traditional approach. They are based on the calculation of optimal solutions following iterative techniques of linear programming [4,5]. The second main group comprises the heuristic methods, whose recent development is linked to the evolution of artificial intelligence procedures. This group includes a broad number of search algorithms [6-9], such as genetic algorithms, simulated annealing, threshold accepting, tabu search, ant colonies, etc. These methods have been successful in areas different to structural engineering [10]. They consist of simple algorithms, but require a great computational effort, since they include a large number of iterations in which the objective function is evaluated and the structural restrictions are checked. Among the first studies of heuristic optimization applied to structures, the contributions of Jenkins [11] and of Rajeev and Krishnamoorthy [12] in the early 1990s are to be mentioned. Both authors applied genetic algorithms to the optimization of the weight of steel structures. As regards RC structures, early applications in 1997 include the work of Coello et al [13], who applied genetic algorithms to the economic optimization of RC beams. Recently, there has been a number of RC applications [14-16], which optimize RC beams and building frames by genetic algorithms. Also recently, our research group has applied simulated annealing and threshold acceptance to the optimization of walls, frame bridges and building frames [17-20]. However, despite advances on structural concrete optimization, present design-office practice of concrete structures is much conditioned by the experience of structural engineers. Most procedures are based on the adoption of cross-section dimensions and material grades based on sanctioned common practice. Once the structure is defined, it follows the analysis of stress resultants and the computation of passive and active O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m

In contrast to conventional structures, deployable structures do not have a fixed geometry and can be transformed between fully expanded and contracted. When folded, they are smaller than traditional fixed structures and can be easily stored and transported. Due to its changeable dimension, the deployable structure has been widely studied in many fields. This research lists the representative applications of deployable structures in three major fields, including aerospace, medical and construction, and analyses the characteristics of each. It is argued that deployable structures are used in several fields currently, however, the various types are not closely related so far, and some of them have not been studied in depth. It leads to the fact that most of the current designs for deployable structures are limited to focusing on specific types. Based on the usage requirements of different industries, the deployable structures often need to be redesigned, thus limiting the promotion of deployable structures in the future. It is believed that categorizing deployable structures according to the scope of application of each type and designing several generalized structural templates for conventional structural shapes will greatly facilitate the utility of deployable structures in various fields.

Abstract. Spacecraft in orbit are gradually developing in the direction of large-scale, complex, and distributed. These aircraft structures will undergo complex thermal deformation because of time-varying and distributed thermal excitation in harsh operating environments. Real-time and accurate structural deformation monitoring is important to ensure the spacecraft's performance in orbit. The inverse Finite Element Method (iFEM) is the most promising strain-based deformation reconstruction algorithm for the independent of the material properties and external load information. However, iFEM needs to obtain the strain field of the structure and accurately define the geometry dimension and boundary displacements. For large deployable aerospace structures, the special characteristics of the unfolding mechanism lead to complex boundary constraints, leading to low shape-sensing accuracy of iFEM if characterized inaccurately. This paper proposed a shape-sensing method that combined iFEM with boundary parameters optimization to deal with the limitation. Based on the genetic algorithm, the parameters of boundary constraints in iFEM are optimized to achieve an accurate representation of complex boundary constraints and high-precision deformation reconstruction. The numerical experiment of a sub-panel structure with complex boundary constraints of a deployable Space-borne antenna was carried out to validate the effectiveness of the proposed method.

Structural optimization with frequency constraints by genetic algorithm using wavelet radial basis function neural network

Various test methods have previously been adopted to test large deployable space structures. However, traditional methods are not applicable to a precise evaluation of three-dimensional deployment characteristics with quasistatic deployment motions. This paper describes the design and performance of a deployment test system using magnetically suspended sliders. The sliders support the deployable structure vertically, and each of them moves freely with negligible friction under the horizontal surface of a ceiling plate. All the sliders control the tension of their vertical cables independently using the feedback signals of the tension sensor to compensate for the gravity of the deployable structure. The test system using magnetically suspended sliders enables maximum drag with a horizontal motion of less than 0.25N and tension control precision from a suspension cable of within 0.25N. The adequacy of this test system is confirmed by a deployment test using a 7m test model.

In architectural engineering, deployable scissor structures are generally used for mobile and temporary applications. They are characterised by their dual functionality as either kinematic mechanisms (during deployment) or loadbearing skeletal structures (after deployment). It is crucial to realise that there is a direct and mutual relationship between the geometry, the kinematics and the structural response of the scissor system. Due to a relatively complex design process it can be highly beneficial to evaluate these structures at a pre-design stage in terms of their structural performance. In order to do so, new computational methods are introduced. Karamba is a finite element plug-in for Grasshopper, fully embedded in the 3D modelling software Rhinoceros, which calculates interactively the response of three dimensional beam structures. The advantage of this new tool is the compatibility with the parametric environment of Grasshopper. These software tools are still in development, but already show their potential in terms of geometric modelling and structural optimisation. In this research it is shown in which way these evolving computational methods can contribute to the design of deployable scissor structures. By using the proposed methodology of preliminary evaluation, the scissor structures are geometrically and structurally optimised at an early stage, thereby enhancing the overall design process and facilitating further detailed analysis.

There is a need for large deployable antennas with diameters larger than 10 m for space‐VLBI satellites and mobile communication satellites. Several deployment mechanisms have been proposed, each of which uses determined lines and points on a smooth prototype reflector surface. The basic structure is to use the reflector surfaces which are located between them as meshes or films.This paper examines types of mechanical errors of a deployable antenna and its relation with the radiation characteristics. Its effects on the radiation characteristics are shown numerically. As a result, it is shown that the gain reduction is less than 0.18 dB by subdividing the reflector surfaces by equilateral triangles whose side is about one‐eighth the radius for a 2‐GHz band tension‐truss type antenna of 15 m diameter. With a penalty of an additional 0.1 dB, the number of approximating triangles can be reduced by about 30 percent by subdividing the outer portion of the reflector twice as roughly as the interior portion. However, it is important to add phase offsets.It is shown that grating lobes appear in the sidelobe characteristics due to the periodic errors. The relationship between mechanical error and the effective error of the reflector surface is also clarified.