9 - IZTECH
Optimized hybrid kinetic and adaptive structures
The main objective of the work package is to demonstrate the feasibility and reveal the potential of shape-controlled structures through the modelling, analysis and design of novel adaptable hybrid systems. It will be demonstrated how a synergistic architectural and engineering approach to the design of responsive structures provides opportunities of maximizing the utility of buildings and accomplishing energy performance that exceeds the one of conventional fixedshape buildings. Controlled-shape buildings may accommodate varying functional needs as well as environmental conditions reinforcing the sustainability of our build-up resources, cost reductions and energy savings. In order to capitalize on these benefits the development of shape-controlled structures requires innovative design processes and topology optimization procedures. The establishment of an appropriate design framework and the development of adaptable structures are included among the major objectives of the WP. In addition the objective of this work-package is to develop an assistance optimization tool for the geometric and structural design of adaptive structural patterns. This tool will be able to optimize possible geometries of a planar or spatial adaptive structure according to the given parameters; or find probable dimensions and connection angles of the elements according to the given geometry. For both situations, the tool will optimize the element sections according to the given exterior conditions like materials, dynamic loads, etc.
WP7 - Optimized hybrid kinetic and adaptive structures [Months: 13-48]
Buildings have traditionally been fixed-shape structures designed to optimize the overall function, environmental or loadbearing performance requirements. Further improvements will be possible through designs that allow buildings to adapt their shape in order to meet the requirements of changing functional needs and/or external environmental conditions, or loading conditions . The work carried out internationally in this field has been fairly limited and mostly remains at a conceptual research level (e.g., parametric associative digital design and 3D graphical representation techniques). Moreover, most of the developments involve passive structures equipped with a control system to enable limited transformability, in an additive way to allow influencing certain controlled members [2-4]. In achieving optimal structural and energy performance, the transformability of kinetic hybrid structures examined in the WP envisages to arise primarily from the inherent integrative composition and dual capabilities of the members with regard to their load-bearing and control function, than exclusively from the mechanical control system. Optimal reconfigurations of the systems may be sought after in a performance-based approach according to the external conditions or local transformations of the members. A mechanism can be defined as a group of rigid bodies connected to each other by rigid kinematic pairs to transmit force and motion . Most movable, foldable, deployable and convertible structures behave as mechanisms during their conversion process and as a load resisting entity when they take a predetermined form. Thus, they have the characteristics of both a mechanism and a bearing structure. These types of mechanisms are called structural mechanisms . Most adaptive structures are structural mechanisms. Some basic mechanisms can be used as unit elements of a planar or spatial structural mechanism. In this WP, such structural mechanisms will be called as deployable structural patterns. This WP will investigate the opportunities for a geometric and structural design assistance method special for adaptive structural patterns. The tool will find (and optimize) the number of structural units, location of all hinge points, coordinates of all nodes, and possible cross-section dimensions according to the given geometry and suggested material. During the study, kinematic analysis and design methods will be used together with geometric optimization, digital parametric design and structural optimization techniques. The WP consists of the following Tasks: Task 7.1: Investigations on Adaptable Architecture and Shape Control The WP will be initiated with a systematic investigation of case examples and interdisciplinary design methodologies of adaptable architectures and shape control of buildings. Traditional approaches of performance-based design approaches applied to conventional building structures will have to be reconsidered to meet the new requirements and fully exploit the potential of this new architectural concept. Key aspects will be identified and investigated together with the respective control requirements. Hybrid structural and tensegrity systems that enable a minimization of the bending stresses of the primary linear structural members through respective development of axial stresses in secondary members will be considered and evaluated in terms of their structural efficiency and kinematic potential [5-7]. In parallel, methodologies Page 24 of 48 for the analysis of adaptable structures will be established, including the kinematic analysis, motion planning and control. Given several similarities between variable shape structures and robotic manipulation systems, well established methodologies from robotics will be appropriately customized to this discipline . Such methodologies concern the kinematics, dynamics and control of the structures. For example, the position of a shape-controlled structure will be effectively represented using coordinate transformations as in the case of an articulated robot. Task 7.2: Structural Analysis and Design of Hybrid Structures Analysis and design of adaptable prototype structural systems includes the definition of the system specifications based on which alternative solutions will be considered and systematically evaluated before finalizing the structural solutions that will be further examined. For this purpose the outcomes of the preliminary investigations of Task 4.1 will be utilized. The structural design will involve selecting the kinematics structure, the required degrees-of-freedom and the actuation methods before proceeding with the actual design of the members [9, 10]. The design will be supported by static analyses in order to calculate the loading for different configurations and loading conditions of the systems. The aim will be the form-optimization as to the load distribution and estimation of the required capacity of the actuators to manoeuvre the structure according to the required motion patterns. Task 7.3: Control System Analysis Concurrently with the structural design, research will be carried out regarding the design of the control system. A list of functional specifications will be compiled based on which the control architecture will be formalized. This will include the necessary functions that the control system will be required to perform, the appropriate responsiveness to external environmental and loading stimuli, the type and degree of interaction with the user, speed of response, reliability levels, safety features to be implemented, expandability, etc. The development of the appropriate control system architecture will indicate the various functions that the system will be required to perform, the functional relationships between them and their hierarchy. The flow and processing of information within the systems will need to be specified including the required user input. The computer control hardware will be analysed and appropriate sensors (position encoders, etc.) and actuators (e.g. electric motors, hydraulic systems, pneumatic systems, etc.) will be selected. Moreover, as part of the control system analysis, the issue of motion planning will also be investigated. The goal will be to design appropriate motion sequences in order to optimize certain cost functions (e.g. energy consumption, motion time, etc.). Task 7.4: Modelling and Simulation Both the structural motion system and the control system will be modelled and overall kinetic hybrid systems will be simulated. Based on the dynamic models the control system will be simulated under different scenarios of interest and the systems behaviour will be predicted. This may include different operating conditions, the effect of external disturbances, etc. Simulations will help confirm the correctness and adequacy of the structural and control system design and study the interactions between them. Task 7.5: Topology Optimization in Kinetic Hybrid Structures For this Task the emphasis will be on form-finding and optimization of the hybrid structures at global and local level. In the first case, the structures may obtain different geometrical reconfigurations according to the external criteria by following the transformation paths specified throughout the motion planning, whereas in between transformation stages from any initial to a target configuration define respective temporary transformation phases . Although the transformation phases constitute only transition intervals, the reconfiguration envelope implies the high flexibility made possible for the transformability of the structures. In this way the optimization of the structures refers to the external conditions and the configurations of the system to be obtained . In the second case the optimization of the structures refers to the members’ geometrical characteristics that may adapt to the external conditions in each transformation stage . Task 7.6: Kinematic Structural Synthesis In the first part of this task, the literature on deployable structural systems will be examined paying attention on modular systems composed of various unit elements. Some examples of such modular systems are designed by Calatrava , Escrig , Hoberman  (Iris Dome and Hoberman Arch), Kokawa , Gantes , van Mele , de Temmermann , Rippmann , Korkmaz , Akgün , Kiper  and Maden . Unit elements of these deployable structures will be listed and a library of unit elements will be constructed. Then, the geometric features of these unit elements will be investigated. Such a study is presented in  In general, unit elements may possess different geometric features; however some unit elements can be used for the same type of geometry, as well. These geometric features will be the base of the next task. Task 7.7: Determination of Shape Topologies According to the geometric features of different types of unit elements, alternative geometric forms obtained by assembling different combinations of units will be examined. This analysis will reveal the geometric constraints on what type of geometric forms can be obtained using the unit elements in the library. These constrained geometries can be called base geometries. The second part of this task is to approximate a given desired geometric form with base geometries. Such geometric approximation studies are given in [22, 28]. This approximation problem can be posed as a geometric optimization problem which can be solved by analytical approximation tools such as least squares Page 25 of 48 approximation, Chebyshev approximation, etc., or numerical optimization tools such as genetic algorithms. The base geometry generically consists of several sections, where each section corresponds to a single type of unit element. Task 7.8: Kinematic Design In this task, first, proper unit elements will be selected for each section of the base geometry. Then the kinematic design of each unit element will be performed. Next, the connection details of the unit elements in adjacent sections will be developed. An example study of such a process is given in . During the kinematic design, some of the construction parameters may be arbitrary. These arbitrary parameters either can be user defined, or else can be determined subject to strength requirements. The structural optimization for the strength considerations is the topic of Task 7.10. Task 7.9: Formulation and Parametric Design In this task, a parametric model will be built using Grasshopper (a graphical algorithm editor) plugin to Rhinoceros® software not only to analyse the alternative geometric forms proposed in Task 7.7, but also to develop a flexible tool allowing changes at the topological, geometrical and structural levels. The parametric model that is established by defining a set of variables (independent parameters) and expressions (relations between parameters) in Grasshopper will enable rapid exploration of different form scenarios by changing the input parameters such as unit elements or surface curvatures. In addition to the topological and geometrical descriptions, some required parameters for the structural analysis will be embedded in the parametric model, including element type and connectivity, material and section properties, boundary conditions, load cases and analysis tasks. The parametric model will allow testing the strength and the stiffness of the proposed structures, as well. According to the given input parameters, all necessary output data will be obtained from the parametric model for further analysis on the structural optimization in Task 7.10. Task 7.10: Structural Optimization Sustainable development should be the main motto for all sorts of industrial applications. Any proposed architectural solution to fulfil spatial requirements should as well come with really necessary amount of materials and as well should also be considered for recyclability as well following the Eco-design initiative. In this task, the parametric design model obtained on the Task 7.9 will be used to perform optimization of the adaptive structures to provide an optimum solution to fulfil the requirements. Adaptive structures can be used for many purposes, there is one possible use which may be very crucial especially in the case of disasters to provide temporary shelters for the survivors. So storage and transportation would be crucial in that sense. A single objective function will be studied first to reach a design satisfying all the strength and stability constraints at a minimum weight. Then topology and material optimization will be carried as a multi objective optimization task. It is planned to extend the study to include other objectives as foldability and space enclosure as well programmed as multi objective optimization process. Both gradient search and metaheuristic methods will be accessorized to complete task.