Variable Topology Mechanism Research Articles

Modeling on flexible variable topology mechanism based on the Kane method

In recent years, with the development of space science and technology and the deepening of space exploration, a new type of institution with variable topology, variable topology, with its flexibility to adapt to the environment and diversity of tasks, has become an important development direction of multi-purpose and highly integrated complex space institutions in our country. Therefore, it is very important to study the dynamic problems of this kind of flexible variable topology mechanism and explore the methods and means to improve the dynamic performance, which meets the major requirements of the development of Chinese space science and technology. In this paper, a rigid-flexible coupling manipulator system that can realize the conversion of single and two degrees of freedom is studied. The full-structure nonlinear dynamics model of the manipulator is established by using the Kane method.

Topology Transformation Analysis on Serial Flexible Variable Topology Mechanism

The flexible variable topology mechanism (FVTM) has become a research focus in the field of the mechanism because of its reconfigurable characteristics, which exhibit excellent adaptability in complicated working environments. In the process of topology transformation, the FVTM often generates impact, which leads to vibration and instability of the flexible elements. It seriously affects the accuracy and reliability of the operation. In view of this, this paper takes the serial-FVTM as an example to analyse its impact characteristics during topology transformation. The impact dynamics model is established by the theorem of impulse. Based on this, the fourth-order Runge-Kutta method is used to solve the dynamics differential equations. Using the control variable method, the influence of different parameters on the impact characteristics of the FVTM is obtained through numerical simulation analysis. Finally, the methods to improve the stability of the FVTM during topology transformation are analysed to expand new ideas for the subsequent research.

Operations in Synthesized Eight Link Gear Variable Topology Mechanism using Python Programming

This paper illustrates the implementation of python programming in the field of kinematics and helps the planners to visualize the working nature of the synthesized mechanism. In the present context, the authors have considered eight link gear variable topology mechanism in this paper which is synthesized using a complex number approach. This synthesized mechanism is studied using MATLAB programming and the various positions obtained are taken into the consideration for python programming. These advanced tools create an insight among the design engineers on the working nature of the mechanism. The operating condition of the synthesized eight link gear variable topology mechanism in two different phases is analyzed using python programming. This shows the mechanism operating condition in two different phases and validates the output obtained with the help of visualization results in mechanism orientation.

A variable-topology morphing composite cylindrical lattice

Morphing composite structures are of significant interest due to the fact that they exhibit superior mass-to-stiffness ratios and a large degree of tailorability in comparison to traditional materials and structures. One such morphing composite structure is the multistable composite cylindrical lattice. Current work introduces a novel variable-topology morphing mechanism to it through the use of both permanent magnets and electromagnets. By replacing a set of mechanical fasteners from the central intersection of the lattice strips with a bespoke variable-topology mechanism introduces a controllable and replicable semi-autonomous means for topology morphing. The variable-topology mechanism allows the structure to transition from being a linear deployment actuator to one that deploys along a curved path, without need for external mechanical input. The behaviour of both the variable-topology mechanism and the topology-changing cylindrical lattice are thoroughly characterised through a combination of mechanical and virtual tests.

Solid Edge 3D Model of Synthesized Geared Slider Crank Mechanism with Variable Topology Features

The paper introduces solid edge 3D model of synthesized geared slider crank mechanism. The synthesized mechanism exhibits the features of variable topology mechanism. This mechanism is modeled in solid edge software and presented. The gear connected to the crank provides the possibility of using it as an input and as well as output to the mechanism. The mechanism showcases the single input to multiple output variable topology features.

Kinematic Synthesis of 3R-1P Geared Slider Crank Mechanism with Variable Topology Features for Motion Generation

The paper focuses on synthesis of slider crank mechanism consisting of a single gear as a part of input and output of the mechanism. Complex number method is used as one of the synthesis criteria. This is a planar four link gear slider mechanism having one degree of freedom which is considered for synthesis using variable topology method for the task of motion generation. The mechanism consists of three revolute and one slider joints. Synthesized mechanism exhibits the features of variable topology mechanism in different modes of operation.

Preliminary design of a revolute to prismatic morphing compliant joint

The reduction of weight and size of mechanisms are important and difficult challenges considering portability, energy efficiency, and simplicity of fabrication. One of the solutions to address these issues consists of mechanisms with variable topology for which the mobility of the output is a succession of several simpler elementary motions. This change of mobility allows for achieving complex motions without necessitating a complicated design where many actuators or types of mechanical transmissions are required. Indeed, these variable topology mechanisms, also referred to as morphing mechanisms, have the ability to change their output motion throughout their workspace. Hand tools, medical devices, and aerospace robotic end-effectors are potential applications of this technology. In this paper, conceptual designs of such a revolute to prismatic morphing joint and its implementation using compliant hinges are proposed. Additionally, performance indexes pertaining to the desired output motion are proposed. First, a pseudo-rigid body model of a design candidate is presented, and simulations of this model are compared with finite element analyses to ensure accuracy. Then, several design features are quantitatively evaluated to propose improvements for future versions of the design. Finally, an early prototype illustrates the potential and feasibility of the proposed design as well as a possible application. Video

A Review on Mechanisms with Variable Topology (Revisiting the Variable Topology Mechanism)

Simple mechanisms are used for various machines to obtainthe desired motions. If the link numbers and degrees of freedomgo on increasing, then the synthesis is also becoming more and more complex. The synthesized mechanisms have some limitations in satisfying the required motions. For these purpose mechanisms having multi-degrees of freedom, adjustable mechanisms and mechanisms with variable topology need to be focused on. Thispaper is mainly focused onthe review of available literature on variable topology mechanisms in general and solution rectification of mechanisms in particular.

Forward dynamics of variable topology mechanisms—The case of constraint activation

Many mechanical systems exhibit changes in their kinematic topology altering the mobility. Ideal contact is the best known cause, but also stiction and controlled locking of parts of a mechanism lead to topology changes. The latter is becoming an important issue in human–machine interaction. Anticipating the dynamic behavior of variable topology mechanisms requires solving a nonsmooth dynamic problem. The core challenge is a physically meaningful transition condition at the topology switching events. Such a condition is presented in this article. Two versions are reported, one using projected motion equations in terms of redundant coordinates, and another one using the Voronets equations in terms of minimal coordinates. Their computational properties are discussed. Results are shown for joint locking of a planar 3R mechanisms and a 6DOF industrial manipulator.

Mechanism Synthesis of a Transformable Wheel-Legged Robot

Based on synthesizing the robot’s chassis mechanism,a transformable chassis is presented to adapt to the conflictive requirements of complex fields. A transformable wheel-legged robot has been designed with the applied chassis. As a variable topology mechanism, the robot has many changeable configurations. Finally the structure implementation of the robot was discussed.

Structure Decomposition and Homomorphism Identification of Planar Variable Topology Mechanisms

Structural analysis of variable topology mechanisms (VTMs) is the leading task when studying the topological variability of mechanisms. Of several major concerns, structure decomposition and homomorphism identification are two dominating issues for the structural analysis of VTMs. This paper presents a systematic computational approach for the structure decomposition and homomorphism identification of planar VTMs. Along with the proposed method, a constraint matrix representation, that records the potential motion constraints and the topological structures of a VTM, is introduced for serving as the basis of the approach. In addition, a new index, namely, degrees of homomorphism (DOHs), is suggested for quantifying the topological similarity among VTMs. For illustration, an automatic steel clamping and sawing mechanism and a group of mechanisms with similar topologies are adopted, from which their structure decomposition and homomorphism identification are carried out. As shown, the method is both symbolically readable and computationally considerable. The result is helpful for the automated structural analysis and synthesis of variable topology mechanisms.

Energy efficiency analysis of quadruped robot with trot gait and combined cycloid foot trajectory

Quadruped robots consume a lot of energy, which is one of the factors restricting their application. Energy efficiency is one of the key evaluating indicators for walking robots. The relationship between energy and elastic elements of walking robots have been studied, but different walking gait patterns and contact status have important influences on locomotion energy efficiency, and the energy efficiency considering the foot-end trajectory has not been reported. Therefore, the energy consumption and energy efficiency of quadruped robot with trot gait and combined cycloid foot trajectory are studied. The forward and inverse kinematics of quadruped robot is derived. The combined cycloid function is proposed to generate horizontal and vertical foot trajectory respectively, which can ensure the acceleration curve of the foot-end smoother and more successive, and reduce the contact force between feet and environment. Because of the variable topology mechanism characteristic of quadruped robot, the leg state is divided into three different phases which are swing phase, transition phase and stance phase during one trot gait cycle. The non-continuous variable constraint between feet and environment of quadruped robot is studied. The dynamic model of quadruped robot is derived considering the variable topology mechanism characteristic, the periodic contact and elastic elements of the robot. The total energy consumption of walking robot during one gait cycle is analyzed based on the dynamic model. The specific resistance is used to evaluate energy efficiency of quadruped robot. The calculation results show the relationships between specific resistance and gait parameters, which can be used to determine the reasonable gait parameters.

Metamorphic Equation of Variable Topology Mechanisms Based on the Constraint function

Metamorphic mechanism has variable topology and possess multiple stable configurations.In order to represent its topological constraint and configuration transformation effectively and accurately,a set of mathematic parameters and equations is studied.The constraint function is defined according to the constraint features of kinematic joints.With constraint functions as elements,the adjacent matrix of the origin kinematic chains of metamorphic mechanism is proposed.Based on the adjacent matrices,metamorphic equations are established correspond to three metamorphic ways of linkages and three metamorphic ways of joints.According to different metamorphic ways,the metamorphic matrices and metamorphic functions are defined.The application example shows that the constraint function and the adjacent matrix can represent variable topology mechanisms conveniently and completely,as well as the metamorphic equations can be used to represent and analyze the configuration transformation of metamorphic mechanisms accurately.The method proposed provides a new way for the representation and analysis of variable topology mechanisms and lays a theoretic foundation on the kinematics and dynamics of metamorphic mechanisms.

Dyad synthesis of planar seven-link variable topology mechanism for motion between two dead-centre positions

This paper suggests variable topology method using Dyad technique for synthesizing seven-link planar mechanism for motion between two dead centre positions. The tasks like path generation with prescribed timing and function generation are also dealt with. Numerical examples are provided and are verified. Complex numbers, which readily lend themselves as an ideal tool for modeling linkage members as parts of planar mechanisms, are used for writing displacement equations for dyads.

On the Operation Space and Motion Compatibility of Variable Topology Mechanisms

With the implementation of just one mechanism, variable topology mechanisms can serve the functions of many mechanisms by changing their topology. These types of mechanisms have raised interest and attracted numerous studies in recent years, yet few of these studies have focused discussing of these mechanisms in light of their operation space. As the change of a variable topology mechanism is induced by either intrinsic constraints or constraints due to the change of joint geometry profile, the operation space of kinematic joints and kinematic chains in various working stages is changed in accordance. A theoretic framework based on the concept of the operation space of variable topology mechanisms is presented here. A number of characteristics with regard to the motion compatibility among joints and loops in different working stages are derived, laying a foundation for systematical synthesis of variable topology mechanisms. Design of a novel latch mechanism for the standardized mechanical interface system is given as an illustrative example for the synthesis of a variable topology mechanism.

Analysis and Design of Lower-Mobility Parallel Mechanism of Non-Symmetrical Based on Variable Topology Theory

First, the branched-chain of parallel mechanism was Classified according to reciprocal screw theory. Then, the introduction of variable topology mechanism theory, with the characteristics of parallel mechanisms themselves, the definition and basic variable topology means of variable topology parallel mechanism were given. With evolutionary theory, the method to design lower-mobility parallel mechanisms of non-asymmetric was proposed based on variable topology mechanism theory .Taking 3-RPS as ideal mechanism and topology synthesis was carried out, besides 2-RPS mechanism were analyzed. The introduction of variable topology mechanism theory provided a theoretical basis and innovative approaches for the synthesis configuration of Lower-mobility parallel mechanisms of non-asymmetric.

Mechanism Design and Gait Experiment of an Amphibian Robotic Turtle

In this paper we describe the design of a new bio-inspired amphibian robot with high environmental adaptability. The robot, called MiniTurtle-I, can transform terrestrial and aquatic locomotion configurations through a new variable topology mechanism (Leg-Flipper). Based on the modular design philosophy, four rotatory joint modules (Joints I–IV) constitute a Leg-Flipper module. Variable topology structure transformation of Leg-Flipper by actuation redundancy enables the robot to achieve a variety of locomotion. Our motivation is to provide another solution to achieve amphibious movement both easily and efficiently. A prototype of MiniTurtle-I is built to exam the configuration transformations. Terrestrial, aquatic and semiaquatic gait experiments are performed to verify the locomotion functions of the MiniTurtle-I.