Due to its simple structure and good deployable characteristics, scissor-like structure (SLS) is widely used in many fields, such as mechanical engineering, structure engineering, and aerospace engineering. Because of its inherent structural characteristics, a SLS can possess superior nonlinearities both in equivalent stiffness and damping only with linear component. It also has high loading capacity and excellent equilibrium stability. Thus, it is promising as a vibration isolator. Based on recent findings, a theoretical study is herein executed to build up a universal stiffness model of full types of SLS (including 6 assembly types), considering mass of scissor arm, Coulomb and viscous friction forces in joint parts. Plus more, perturbation method (PM) and average method (AM) are applied to investigate vibration isolation performances of SLS with different assembly types and installation parameters and to compare them with known quasi-zero-stiffness vibration isolators in the literature. Finally, a simulation is done to testify the presented findings and to compare them with former studies. It is shown that: without changing its overall structure and outside dimensions, a SLS vibration isolator can have significantly different nonlinear stiffness for specific nonlinear characteristics only through adjusting assembly type, installation parameters, and initial deformation of its linear component. Since allowable workspace of a vibration isolator is always limited by isolation object and its surrounding structure, this finding indicates a new way to design and modify vibration isolation performance of a system. It will greatly expand application of SLS in vibration isolation.

Analysis on nonlinear stiffness and vibration isolation performance of scissor-like structure with full types

Inspection and maintenance of equipment inside buildings, such as exit signs, bared pipelines, air vents, and fire alarms often requires a robot to reach high, hidden, or confined areas that are difficult for humans to access. Even though these tasks are easy and repeatable, they are still not automated. The Mobile Extendable Robot Arm (MERA) is a movable robot arm with a novel 2-DOF scissor mechanism for reaching a high place and positioning an end-effector. MERA is composed of a locomotion vehicle with a rotation table and a 4-DOF extender arm, itself made of two layers of the 2-DOF scissor mechanism arranged in series. Placing the end-effector at an arbitrary point in space, the 4-DOF arm possesses two degrees of redundancy, allowing access to a point from various directions and enabling obstacle avoidance. In this paper, we present the design and analysis of the 2-DOF scissor mechanism. The 2-DOF scissor mechanism has two rotary actuators for driving the base links individually; consequently, the mechanism can elongate the entire body and tilt at the center of the base shaft. However, we found that the 2-DOF scissor mechanism had a singularity; after analyzing the singularity, we propose two novel solutions to the problem.

/pdf/a-mobile-extendable-robot-arm-singularity-analysis-and-2uqf4llz1j.pdf

A Mobile Extendable Robot Arm: Singularity Analysis and Design*

Scissor mechanism, a basic element of structure and mechanism, can be used to make lots of deployable structures and functional motion devices. In such structures or devices, input configuration and parameter settings of actuator in scissor mechanism are variable and very important to structural forces and kinematics, however, has not been investigated systematically. Former researches on input vectors only consider a mechanism with decided input configuration and parameter settings. To supply a universal model for design purpose, a CHAracteristic Triangle (CHAT) is herein reported to calculate input vectors. The CHAT can be picked up from each of six input configurations of single group scissor lift mechanism. Based on former works and authors’ simulations, several value rules of input vectors in scissor mechanism are discovered, summarized, and approved via mathematics analysis. One of those rules shows that the maximum input force always occurs in the beginning position of lifting. Which indicates extreme importance of initial lift angle to design. Meanwhile, a further research on typology refines six input configurations into more detailed value cases according to possible parameter settings. Among them, three constant lift force cases, two singular cases and other cases are discussed individually. Typology and value rules are significant to power selection, mechanism configuration design and dimension optimization. Validity of presented equations is approved by four reported samples. Not limit to studied single group mechanisms, CHAT can also be found easily in every linear driven scissor lift mechanism such as multiple group mechanism, parallel mechanism, or nonstandard connected single group mechanism. Thus, presented universal equations are suitable for widespread applications with scissor mechanism.

/pdf/a-characteristic-triangle-method-on-input-vectors-of-scissor-2ixzwkbbcj.pdf

A characteristic triangle method on input vectors of scissor lift mechanism and its applications in modeling and analysis

In order to meet the needs of transporting turnover box filled with medicines from the shelves of high-mix low-capacity medicine warehouses to the stations of various departments in hospitals, a novel AGV with automatic pick-and-place system based on scissor lifting platform was proposed. The mechanical structure consists of AGV chassis, scissor lifting mechanism, rotary platform, extension mechanism and vacuum sucker actuator. Each parts of the device were analyzed and designed. The strength of the scissors mechanism is analyzed by Finite-element analysis, and the structure is optimized. The AGV adopts multi-modal control mode, realizes the control and autonomous operation of the whole vehicle based on Robot Operating System. The AGV combines magnetic stripe navigation and RFID site label to realize autonomous driving and it is equipped with ultrasonic sensors and LiDAR as safety system. Finally, the whole system is built, and functional tests are carried out on each module. The experimental results show that the entire system meets the design requirements and complete specific work tasks.

Design of a novel AGV with automatic pick-and-place system based on scissor lifting platform

In this study, an innovative 25-ton-capacity scissor lift was designed for the first time, and a prototype was produced in Onder Group Inc. Within the scope of the study, a rolling bearing system was designed instead of the conventional welded scissor-hinge connection system. Static and strength calculations were made using finite element analysis for comparison purposes. As a result of the analysis, it was determined that the stress distribution on the roller bearing system was more homogeneous and at lower values (≈60 MPa) than the welded hinge system. In addition, a detachable (bolted) joint was obtained instead of a fixed (welded) joint with the designed rolling bearing system. With the design analyses carried out within the scope of the study, a particular joint-clamp system was made to expand the surface areas of the welded joints.

/pdf/design-and-prototype-production-of-scissor-lift-platform-25-19u1lzy8.pdf

Design and Prototype Production of Scissor Lift Platform 25 Tons Capacity

Scissor lifting mechanisms are widely equipped on airport ground support facilities, in this paper, we propose a unified modeling process for two special SLMs by establishing the expression of input motion vectors and input force vectors and test the results by three proposed cases. A characteristic triangle and corresponding parameters are introduced for any configuration. The presented method provides a reference mode for studying scissor lifting mechanism.

Unified Modeling for Input Forces and Input Vectors for Two Scissor Lifting Mechanisms

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A characteristic triangle method on input vectors of scissor lift mechanism and its applications in modeling and analysis

Unified Modeling for Input Forces and Input Vectors for Two Scissor Lifting Mechanisms