When the existing literature on the research of scissor structures is thoroughly investigated, it is seen that different researchers use different terminologies and classifications especially for the definition of the primary units and the motion type. Some of the studies define the whole geometry based on the geometric properties of the primary scissor units and the unit lines while some other studies define it according to the loops. All these studies use different names for similar elements. This article aims to review the literature on the classification and terminology of scissor structures and represent the state of art on the studies. Tables are represented showing all approaches in the literature. In addition, the article criticizes the missing points of each terminology and definition, and proposes some new terminology. In order to arrive at this aim, different definitions of the primary scissor units and motion types used in key studies in the literature are investigated thoroughly. With several examples, it is demonstrated that naming the scissor units according to the resulting motion type might be misleading and it is better to specify the motion type for the whole structure. A classification for transformation of planar curves is presented.
Scissor linkages are commonly used as mechanisms for scaling objects. They constitute a significant portion of deployable structures. Since 1960s many researchers sought to form novel structures using the scissor units. In 1990s Hoberman brought a new perspective to the field when he used the loops, not the units to form linkages. Starting from mid 2000s, other researchers joined into this new approach of design. One of the latest researches presented a design for scaling a circular forms with antiparallelogram loops. This study shows that an anti-parallelogram loop assembly can also be used for scaling planar curves with variable curvature.
Scissor mechanisms are frequently used for deployable structures and many studies have been conducted on the subject. Most of the studies consider scissor units as modules in the design process. An alternative approach is to utilize loops as the modules for design. In this paper, the
design alternatives of single degree-of-freedom planar linkages comprising anti-parallelogram loops using the loop assembly method is presented. First, scissor mechanisms are reviewed. Next, the types of four-bar loops and the resulting linkages in the literature are introduced and those which
are yet to be explored, anti-parallelogram being one of them, are identified. Then the loop assembly method and the examples in the literature are reviewed. As a method to form as many alternatives as possible, symmetry operations are proposed. Suitable frieze symmetry groups utilized for
obtaining the assemblies are explained and the anti-parallelogram loop patterns are derived. Next, the single degree-of-freedom linkages are obtained from the loop assemblies. Finally, a selection of the resulting linkages with novel properties are presented. This study shows that loop assemblies
are efficient in systematic type synthesis of scissor linkages, some types of which could not be foreseen by using units as modules.
Hareketli köprüler ilk zamanlar korunma ihtiyacı ile tasarlanmıştır. Modern zamanlarda ise ulaşımı kolaylaştırmak için geliştirilmeye devam edilmektedir. Sabit köprülerin aksine farklı kullanım senaryolarını desteklemeleri sebebiyle tercih edilmektedirler. Bu yazıda mevcut hareketli köprüler kinematik özellikleri açısından tanıtılmış, hangi kullanım seneryolarını destekledikleri ve eksik kaldıkları yönler açıklanmıştır. Daha sonra güncel bir örnek olan Rolling Bridge'de kullanılmış strüktürel mekanizmanın tasarım prensiplerden yararlanarak, tüm kullanım senaryolarını destekleyen form değiştirebilen köprü için çok devreli ve iki serbestlikli yeni bir strüktürel mekanizma önerilmiştir. Son olarak mekanizmanın pozisyon analizi yapılarak Microsoft Excel ® ortamında gerçekleştirilen grafik sunulmuştur.
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