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Scissor-like bridges can quickly build emergency channels after disasters and improve rescue efficiency. In view of the characteristics of poor stiffness and low material utilization of scissor-like elements（SLEs）, a new cable supported scissor-like deployable bridge（CSSDB）for emergency was proposed combined with cable supported system. In order to investigate the behavior of CSSDB, Karamba3D was adopted to establish the finite element model, and parametric analysis was carried out under the action of moving vehicle load, considering the struts’ length and numbers, the SLEs’ cross section, the initial prestress amplitude and the expansion angle. Besides, Galapagos was used to optimize the CSSDB with the minimum structural mass as the optimization objective. The results show that increasing struts’ number, struts’ length and initial prestress can effectively reduce the stress and deflection of SLEs, while the stress and deflection can be increased by increasing expansion angle. Increasing thickeness of SLEs’ cross section reduces stress and increases deflection instead, and the CSSDB’s performance is still dependent on bending of SLEs. The optimization reduces structural mass by 38.89%, and the stress and deflection of CSSDB are 0.25 and 0.2 times than that of the corresponding scissor-like bridge, which proves the superiority of the CSSDB. [ABSTRACT FROM AUTHOR]

Abstract There are vast constraint equations in conventional dynamics analysis of deployable structures, which lead to differential-algebraic equations (DAEs) solved hard. To reduce the difficulty of solving and the amount of equations, a new flexible multibody dynamics analysis methodology of deployable structures with scissor-like elements (SLEs) is presented. Firstly, a precise model of a flexible bar of SLE is established by the higher order shear deformable beam element based on the absolute nodal coordinate formulation (ANCF), and the master/slave freedom method is used to obtain the dynamics equations of SLEs without constraint equations. Secondly, according to features of deployable structures, the specification matrix method (SMM) is proposed to eliminate the constraint equations among SLEs in the frame of ANCF. With this method, the inner and the boundary nodal coordinates of element characteristic matrices can be separated simply and efficiently, especially on condition that there are vast nodal coordinates. So the element characteristic matrices can be added end to end circularly. Thus, the dynamic model of deployable structure reduces dimension and can be assembled without any constraint equation. Next, a new iteration procedure for the generalized-α algorithm is presented to solve the ordinary differential equations (ODEs) of deployable structure. Finally, the proposed methodology is used to analyze the flexible multi-body dynamics of a planar linear array deployable structure based on three scissor-like elements. The simulation results show that flexibility has a significant influence on the deployment motion of the deployable structure. The proposed methodology indeed reduce the difficulty of solving and the amount of equations by eliminating redundant degrees of freedom and the constraint equations in scissor-like elements and among scissor-like elements.

Structural units are the basic components of self-locking foldable grid structures, and their spatial configurations have a vital influence on the structural performance of the overall grid. Research on the deployment process of structural units can help effectively control their stress level and achieve a rational self-locking capability for the units. Therefore, this article describes experimental and modeling studies on the deployment process of structural units and provides a reference for the establishment of numerical models and the design of structural units. The experimental results revealed that the self-locking capability of a structural unit is mainly determined by the bending moments of its members in the planes of the scissor-like elements. The method for adjusting the locations of the pivot endpoints at the radial bars is effective for improving the self-locking capacity, but the degree of adjustment must be strictly controlled to prevent large rotation at the inner lower hub joint. In addition, the feasibility of the modeling method was verified by comparing the experimental curves with the curves obtained by theoretical models. [ABSTRACT FROM AUTHOR]

• A system of two components alternatingly linearly interconnected is developed. • Scissor-like elements are connected with cable bending-active members in pairs. • In the form-found state the scissor-like elements' joints are locked. • Coupling cables increase the stiffness of the bending-active members. • The system enables form flexibility and adaptability. The development of transformable structures in architecture is primarily based on the reduction of self-weight, construction volume and technical complexity, so as to achieve reconfigurability and provide efficient kinematics in terms of shape transformations and deformations. Along these lines, the current paper refers to the design and analysis of an adaptive structure of two components alternatingly linearly interconnected; namely, scissor-like elements (SLEs), and inversely curvilinear cable bending-active members in pairs. Initially, the study investigates parametrically the geometrical configurations of the proposed structural system as to the location of the SLEs joint and the relative lengths of the elastic members in pairs. The subsequent Finite-Element Analysis (FEA) of nine selected system configurations includes their form-finding and vertical loading. In the respective form-found state, the central joints of the SLEs are locked via electromagnetic brakes, and the coupling cables are introduced to the bending-active members. The proposed structure aims at increasing related transformation capabilities, form flexibility and adaptability, on the basis of the two components' contribution. [ABSTRACT FROM AUTHOR]

Highlights • A novel family of extendable kinematic chains, termed dual scissor-like mechanisms(D-SLiM), is proposed in this paper. • Three such D -SLiM legs are employed to build two novel 3-DOF scissor-like mechanism - parallel lower-mobility(SLiM-PaLM) manipulators with "Y" and "△" shapes. • The mechanics, common kinematics, simplified dynamics, workspaces, deployed-stowed ratios and stiffnesses of the SLiM-PaLM manipulators are investigated. • Prototypes of the Y- and △-shaped SLiM-PaLM manipulators are fabricated and tested which validate the mobility and motion feasibility of these manipulators. Abstract A novel family of extendable kinematic chains, termed dual scissor-like mechanisms (D-SLiM), is proposed in this paper. The chains, which generally have two translational degrees of freedom (DOF), are constructed by linking two identical parallel scissor-like elements. The mobility and singularities of the proposed kinematic chains are discussed. Three such D-SLiM legs are employed to build two 3-DOF scissor-like mechanisms - parallel lower-mobility(SLiM-PaLM) manipulators with "Y" and "△" shapes, termed Y- and △- shaped SLiM-PaLM manipulators, respectively. Due to the large range of motion of each leg, such translational parallel manipulators are capable of being collapsed for storage and deployed in the work area. Common kinematic and simplified dynamic models are derived. The forces in the horizontal links are addressed for analyzing the singularities and stiffness of the D-SLiM. Furthermore, the workspace, stiffness and deployed-stowed length ratio of the SLiM-PaLM manipulators are investigated. Prototypes of the Y- and △-shaped SLiM-PaLM manipulators are fabricated and tested to validate the presented design and analysis. [ABSTRACT FROM AUTHOR]

In the design and analysis of morphing wings, several sciences need to be integrated. This article tries to answer the question, “What is the most appropriate actuation mechanism to morph the wing profile?„ by introducing the synthesis, analysis, and design of a novel scissor-structural mechanism (SSM) for the trailing edge of a morphing wing. The SSM, which is deployable, is created via a combination of various scissor-like elements (SLEs). In order to provide mobility requirements, a four-bar linkage (FBL) is assembled with the proposed SSM. The SSM is designed with a novel kinematic synthesis concept, so it follows the airfoil camber with minimum design error. In this concept, assuming a fully-compliant wing skin, various types of SLEs are assembled together, and emergent SSM provide the desired airfoil geometries. In order to provide the required aerodynamic efficiency of newly-created airfoil geometries and obtain pressure distribution over the airfoil, two-dimensional (2D) aerodynamic analyses have been conducted. The analyses show similar aerodynamic behavior with the desired NACA airfoils. By assigning the approximate link masses and mass centers, the dynamic force analysis of the mechanism has also been performed, and the required torque to drive the newly-developed SSM is estimated as feasible.

This article proposes a structural dynamics method for foldable stairs based on transfer matrix. The stairs are made up of a number of identical scissor-like elements which are supposed to be Euler–Bernoulli beams. The dynamics of each segment beam between every two adjacent revolute joints can be precisely expressed by the transfer matrix of the segment with the variables of boundary conditions of the joints. Therefore, the structural dynamics of the whole stairs is built using the least number of variables compared with the traditional methods. In addition, this method avoids the problem of the traditional transfer-matrix method that the number of variables greatly increases when there are a huge number of cross-joints within a structure. [ABSTRACT FROM PUBLISHER]

• Dynamic equation is represented like a mass-spring-damper model. • Parameters are computed by least squares method. • Linear matrix inequalities employed to define a robust control law. • Controller offers zero steady-state error and arbitrary poles allocation. • Controller is able to deal with uncertainties. In this paper we present a standard robust control strategy to deal with uncertainties in scissor-like elements (SLE) systems. The dynamic equation is obtained by system identification theory and simplified into a mass-spring-damper (MSD) model. The desired performance can be obtained if the closed-loop poles are adequately allocated in the complex plane. A linear matrix inequality (LMI) based on Lyapunov stability and stabilization theorems are employed to that. This techique is applied and tested in practical mechatronic examples based on SLE mechanisms. [ABSTRACT FROM AUTHOR]

In the design and analysis of morphing wings, several sciences need to be integrated. This article tries to answer the question, "What is the most appropriate actuation mechanism to morph the wing profile?" by introducing the synthesis, analysis, and design of a novel scissor-structural mechanism (SSM) for the trailing edge of a morphing wing. The SSM, which is deployable, is created via a combination of various scissor-like elements (SLEs). In order to provide mobility requirements, a four-bar linkage (FBL) is assembled with the proposed SSM. The SSM is designed with a novel kinematic synthesis concept, so it follows the airfoil camber with minimum design error. In this concept, assuming a fully-compliant wing skin, various types of SLEs are assembled together, and emergent SSM provide the desired airfoil geometries. In order to provide the required aerodynamic efficiency of newly-created airfoil geometries and obtain pressure distribution over the airfoil, two-dimensional (2D) aerodynamic analyses have been conducted. The analyses show similar aerodynamic behavior with the desired NACA airfoils. By assigning the approximate link masses and mass centers, the dynamic force analysis of the mechanism has also been performed, and the required torque to drive the newly-developed SSM is estimated as feasible. [ABSTRACT FROM AUTHOR]