Metamorphic Mechanism Research Articles

Dynamic Analysis of Metamorphic Mechanisms with Impact Effects During Configuration Transformation

Metamorphic mechanisms have attracted considerable attention owing to their capability to switch their topology to adapt to different operational tasks. One feature of topological change is the re-contact of different bodies, which inevitably causes collisions affecting operation accuracy and service life. Consequently, in this study, a collision incidence matrix was introduced to describe the topology of a system involved in collisions, and a method for reducing the closed-loop system to an open-loop system was proposed. The complex movement of the metamorphic mechanism in a changing topology was classified into two different running stages of the source metamorphic mechanism. Based on the relative coordinate method, dynamic modeling of the source metamorphic mechanism considering the impact effects was conducted. Combining the classical collision theory and Newton–Euler equation, the generated impact impulse and the motion after collision were determined. Subsequently, a dynamic analytical method for the full configuration of metamorphic mechanisms was proposed to reflect the changes in the topological structure in the dynamic model. Finally, two typical metamorphic mechanisms used in packaging and spinning were considered as examples to verify the correctness and effectiveness of the proposed method, and their impact characteristics during configuration transformation were analyzed. The proposed analytical method of internal impact for a variable topology process provides effective theoretical guidance for the stability analysis of configuration transformation and structural design aimed at minimizing impacts.

Evolution Design of Multiple Metamorphic Mechanisms Inspired by the Concept of Assur Group

Evolution Design of Multiple Metamorphic Mechanisms Inspired by the Concept of Assur Group

Reliability Optimization Design of Constrained Metamorphic Mechanism Based on the Augmented Assur Groups

Reliability Optimization Design of Constrained Metamorphic Mechanism Based on the Augmented Assur Groups

A family of folding single-loop metamorphic mechanisms for aerospace manipulators: Synthesis, network, and analysis

Guided by predetermined degrees of freedom for different desired tasks, the type synthesis of single-loop metamorphic mechanisms (SLMMs) has long posed a challenge. Owing to the complexity and coupling of their overconstraints and the variability of constraints arising from bifurcation motions, it is difficult to ensure geometric coordination and synchronous motion for a network of multiple SLMMs. Here, we propose an approach to type synthesize SLMMs using the atlas method. A novel family of SLMMs is further synthesized. The mobility analysis of a selected 7R SLMM is carried out via screw theory. The kinematics and bifurcation phenomena are analyzed and verified through numerical simulation using computer-aided design models. To evaluate the performance of the SLMMs, the mapping relationship between key design parameters and performance indicators, such as the grasping angle, folding angle, and mechanical advantage, is studied. A networking method is then proposed by considering the geometric coordination conditions and variation of the overconstraints of SLMMs. Prototypes of an SLMM and manipulator with optimal geometrical parameters are developed to verify the feasibility and correctness of the proposed method and kinematic analysis.

Teleoperation of an Anthropomorphic Robot Hand with a Metamorphic Palm and Tunable-Stiffness Soft Fingers.

Teleoperation in soft robotics can endow soft robots with the ability to perform complex tasks through human-robot interaction. In this study, we propose a teleoperated anthropomorphic soft robot hand with variable degrees of freedom (DOFs) and a metamorphic palm. The soft robot hand consists of four pneumatic-actuated fingers, which can be heated to tune stiffness. A metamorphic mechanism was actuated to morph the hand palm by servo motors. The human fingers' DOF, gesture, and muscle stiffness were collected and mapped to the soft robotic hand through the sensory feedback from surface electromyography devices on the jib. The results show that the proposed soft robot hand can generate a variety of anthropomorphic configurations and can be remotely controlled to perform complex tasks such as primitively operating the cell phone and placing the building blocks. We also show that the soft hand can grasp a target through the slit by varying the DOFs and stiffness in a trail.

Design, Configuration Synthesis, and Experimental Study of Side-Rolling Metamorphic Mechanism for Metal Additive Manufacturing

Arc additive manufacturing (AAM) has the advantages of fast deposition speed and good surfacing quality. It is a promising additive manufacturing (AM) method. However, arc additive manufacturing is difficult to use widely in industry due to its poor deformation, microstructure, and mechanical properties. Since the mechanical properties of materials can be greatly improved by rolling, a method for configuration synthesis of the side-rolling mechanism by using metamorphic mechanism theory is presented in this paper. Firstly, by analyzing the operational demands of the side-rolling mechanism, we obtained the motion cycle diagram for the metamorphic mechanism in addition to the corresponding equivalent resistance gradient matrix. Secondly, according to the motion cycle diagram and equivalent resistance gradient matrix of the metamorphic mechanism, the structure and constraint form of the metamorphic joints were established, and the relationship between the force variation and the structure and the constraint form of the metamorphic joints was also obtained. Then, the structures of all 12 corresponding constrained metamorphic mechanisms were synthesized. Ultimately, one among the twelve mechanisms was chosen as the side-rolling metamorphic mechanism. The topological transformation of its working configuration was examined. The results confirmed the feasibility and practicality of the proposed structural synthesis method in this study.

Gait and simulation analysis of quadruped crawling robot based on metamorphic structure

PurposeThis study aims to present a type of metamorphic mechanism-based quadruped crawling robot. The trunk design of the robot has a metamorphic mechanism, which endows it with excellent crawling capability and adaptability in challenging environments.Design/methodology/approachThe robot consists of a metamorphic trunk and four series-connected three-joint legs. First, the walking and steering strategy is planned through the stability and mechanics analysis. Then, the walking and steering performance is examined using virtual prototype technology, as well as the efficacy of the walking and turning strategy.FindingsThe metamorphic quadruped crawling robot has wider application due to its variable trunk configuration and excellent leg motion space. The robot can move in two modes (constant trunk and trunk configuration transformation, respectively, while walking and rotating), which exhibits outstanding stability and adaptability in the examination and verification of prototypes.Originality/valueThe design can enhance the capacity of the quadruped crawling robot to move across a complex environment. The virtual prototype technology verifies that the proposed walking and steering strategy has good maneuverability and stability, which considerably expands the application opportunity in the fields of complicated scene identification and investigation.

Reaction mechanism of exfoliation degree and high temperature surface oxidation metamorphism of 2D Ti3C2Tx on thermal decomposition of various energetic materials

Achieving higher and faster energy release processes is a major research goal for energetic materials (EMs). Typically, EMs enhance their overall performance by incorporating catalysts. The novel two-dimensional layered MXenes, such as Ti3C2Tx, have shown significant potential as additives for ammonium perchlorate (AP). However, there is limited research on the impact of the exfoliation degree and high temperature oxidation of Ti3C2Tx MXene catalyst on the pyrolysis and combustion of different types of EMs. In this study, ultrathin Ti3C2Tx (U–Ti3C2Tx) MXene with a high exfoliation degree of approximately 20–80 nm was obtained through hydrofluoric acid (HF) etching, dimethyl sulfoxide (DMSO)-assisted layer expansion and ultrasonic peeling. The catalytic performance of MXenes on the thermal decomposition of three types of EMs (dihydroxylammonium 5, 5′-bistetrazole-1, 1′-diolate (TKX-50), cyclotetramethylene tetranitroamine (HMX), and AP) was evaluated. Results showed that 4 wt% U–Ti3C2Tx can reduce the decomposition peak of TKX-50 by 33.6 °C and decreases the high temperature decomposition (HTD) peak of AP by 45.5 °C, indicating superior catalytic performance compared to non-exfoliated Ti3C2Tx MXene. However, it had insignificant effect on HMX. Surface chemical analysis, electrochemical characterization, thermal decomposition of gaseous products analysis and material studio simulation all confirmed that high exfoliation U–Ti3C2Tx MXene exhibited better stability and electrical conductivity, facilitating the acceleration of the H+ transfer process and rapid gas release from EMs. Additionally, ignition tests demonstrated that high exfoliation U–Ti3C2Tx could effectively participate in the ignition process of EMs. The characterization and thermal analysis of Ti3C2Tx products after high temperature and oxidation treatment indicated that the catalytic activity is weakened due to high temperature crystal collapse and surface oxidation to TiOx metamorphism. This study provides new insights for the application of MXene catalysts in EMs.

Design and analysis of a novel cantilevered metamorphic mechanism deployable in plane

Originating from the truss topology optimization of a cantilever beam model loaded at a single point at the end, this article introduces a novel cantilevered metamorphic mechanism that can transform between the space truss and the plane state. Firstly, by eliminating triangular sub-structures within the cantilevered truss, it accomplishes the truss-mechanism transformation and synthesizes the metamorphic mechanism with three configurations. Secondly, the product of exponentials is utilized to establish forward kinematics models, and we analyze the locations and velocities of three key nodes. Thirdly, for the dimensional synthesis of structure parameters and with the help of the space model, we draw performance atlases of the input transmission index. Finally, the case study is carried out based on a specific mechanism, and it finds that this metamorphic mechanism shows excellent kinematic performance. This work provides an important theoretical basis for engineering applications, and the metamorphic mechanism has great application potential in many fields such as aerospace, marine engineering, and robotics. Furthermore, this research will also inspire researchers to develop other metamorphic mechanisms.

Reconfiguration characteristic revelation of multiple metamorphic mechanisms based on geometric morphology of screw systems

The design and analysis of reconfigurable mechanisms is a hot topic in the current research, but few studies discuss the impact of geometric parameter changes on the mechanism's reconfiguration characteristics. In this paper, for a family of 6R single-loop multiple metamorphic mechanisms, the evolution of reconfiguration characteristics under the change of geometric parameters is analyzed, including the link length ratio and the orientation characteristics of revolute joints. Based on the geometric morphology of screw system, the reconfiguration characteristics of the mechanism under different parameters are revealed, and the influence of parameter changes on the reconfiguration characteristics of the mechanism is discussed. Meanwhile, the effect of double parameter changes on mechanism reconfiguration is studied, and the reconfiguration characteristics of mechanisms under different parameter ranges are divided into seven different types.

Inverted Modelling: An Effective Way to Support Motion Planning of Legged Mobile Robots

This paper presents an effective way to support motion planning of legged mobile robots—Inverted Modelling, based on the equivalent metamorphic mechanism concept. The difference from the previous research is that we herein invert the equivalent parallel mechanism. Assuming the leg mechanisms are hybrid links, the body of robot being considered as fixed platform, and ground as moving platform. The motion performance is transformed and measured in the body frame. Terrain and joint limits are used as input parameters to the model, resulting in the representation which is independent of terrains and particular poses in Inverted Modelling. Hence, it can universally be applied to any kind of legged robots as global motion performance framework. Several performance measurements using Inverted Modelling are presented and used in motion performance evaluation. According to the requirements of actual work like motion continuity and stability, motion planning of legged robot can be achieved using different measurements on different terrains. Two cases studies present the simulations of quadruped and hexapod robots walking on rugged roads. The results verify the correctness and effectiveness of the proposed method.

Analysis and Design of the Reconfiguration Motion Qualities of a Deformable Robot Based on a Metamorphic Mechanism

Analysis and Design of the Reconfiguration Motion Qualities of a Deformable Robot Based on a Metamorphic Mechanism

Current Status and Development Strategy of the Flexible Metamorphic Mechanism

Current Status and Development Strategy of the Flexible Metamorphic Mechanism

Reliability Optimization Design Method of Constrained Metamorphic Mechanism Oriented to the Stability of Configuration Transformation

Reliability Optimization Design Method of Constrained Metamorphic Mechanism Oriented to the Stability of Configuration Transformation

Reliability analysis and optimization of dynamics of metamorphic mechanisms with multiple failure modes

Metamorphic mechanisms usually have multiple failure modes in engineering applications. Due to the complex dynamics and different configuration transformations under various work states, these mechanisms urgently require an efficient evaluation method to evaluate their reliability. A reliability analysis of dynamics for a controllable metamorphic palletizing robot considering the multiple failure modes and the random and interval variables is proposed. The dynamic responses are integrated into the new variables to calculate the reliability in this method, and further solved by a developed optimization scheme based on sensitivity. This scheme can obtain the dynamics within each variable range at one time. Meanwhile, compared with the conventional calculation and experiment validation, the case results show that their relative deviations of reliability are small, demonstrating the effectiveness of the proposed calculation method and optimization scheme. This work offers theoretical reliability references for the application of metamorphic mechanisms in engineering.

An Improved Metamorphosis-Based Scheme of Feed Mechanism Using Configuration Synthesis

In this work, the principle of metamorphic mechanism is optimized for the product design based on variable topological structures. One metamorphic element consisting of kinematic pair and kinematic size is proposed firstly and a configuration synthesis strategy for feed mechanism is performed in term of the translocation, inversion and duplication variation methods. Metamorphic elements are obtained by decomposing the source metamorphic mechanism. A novelty configuration scheme based on constraint variation features is established by the solution of the constraint relationship of metamorphic elements, and three kinds of configurations are synthesized. Comparisons with kinematic performances between source mechanism and developed mechanism configurations are modelled by the kinematic simulation. Results demonstrate that the multiple types of metamorphic mechanisms can be successfully synthesized, and the demands of functional targets are satisfied completely.

Ultrahigh temperature metamorphism recorded in the Lüliang Complex, Trans-North China Orogen: P–T–t evolution and heating mechanism

Identifying ultrahigh temperature (UHT) metamorphism from hot orogens and establishing its pressure–temperature–time (P–T–t) path will provide notable insights into tectonic evolution and heat source (mantle/mafic magma vs crustal radioactive elements) responsible for the extreme conditions. We report here a combined investigation of petrography, mineral chemistry, phase equilibria modelling, geothermobarometer calculation, geochronology and heat source for mafic and pelitic granulites from the Lüliang Complex, Trans-North China Orogen (TNCO), a representative Paleoproterozoic hot collisional orogen. The rocks record clockwise P–T paths, including granulite-facies peak and post-peak retrograde stages. Garnet + pyroxene + high-Ti hornblende-bearing assemblage in the mafic granulite and garnet + feldspar + sillimanite-bearing assemblage in the pelitic granulite constrain the thermal peaks at 8.2–10 kbar and 880–959 °C, suggesting UHT conditions. Zircon and monazite U–Pb dating, hornblende 40Ar/39Ar dating and Ti-in-zircon thermometer calculation indicate that the rocks may have experienced sluggish retrograde metamorphism from 1.92 to 1.80 Ga, with a cooling rate of 2.0–2.5 °C/Ma. The newly discovered UHT metamorphism, combined with previous geological data, validates a long-lived tectono-thermal evolution from 1.97 to 1.80 Ga in the TNCO. The calculated heat flow produced by the decay of radioactive elements in the thickened crust is 37–77 mW/m2 (with an average of 56 mW/m2), which is high enough to achieve UHT conditions. Therefore, we suggest that radioactive heating can be an important heating mechanism for UHT metamorphism in a long-lived hot orogen like the TNCO.

Dynamic analysis of a three-fingered deployable metamorphic robotic grasper

This paper selects a three-fingered deployable metamorphic robotic grasper as the studied object and presents a distributed dynamic modeling method for the multi-body system based on the metamorphic mechanism. Considering that the grasper contains two independent motion configurations, dynamic models of them are independently established, and then the final dynamic model of the whole grasper is formed. To further improve the modeling accuracy, it is creatively proposed that irregular links can be seen as rigid connections of multiple regular links, by which the dynamic model for the deployment motion of the grasper is firstly established via the Lagrange equation. For the grasping motion, since the finger of the grasper can be equivalent to a planar 4R serial mechanism, the dynamic models of the base mechanism and the basic module are established by the Lagrange equation to obtain the relationships between the driving forces and the equivalent torques. The whole grasper is then established by the recursive Newton-Euler method to enhance the modeling efficiency. Finally, the effectiveness of the dynamic model is well verified by the dynamic simulation.

Sylvester’s dialytic elimination in analysis of a metamorphic mechanism derived from ladybird wings

This paper investigates the metamorphic mechanism derived from the hindwing in ladybird beetles, which creates its mathematical models and analyzes kinematics based on screw theory using mathematical software. The hindwing in ladybird beetles is an origami-like structure. Considering the concept of equivalent mechanisms, any origami pattern can be seen as being composed of several spherical multi-bar linkages connecting to each other. Hence, this paper proposes an algebra method to reveal the relations between different joint angles in the spherical multi-bar linkage, using the loop equations and Sylvester’s dialytic elimination method. The results can be used to find the location and the motion trajectory of any desired point in this ladybird wing metamorphic mechanism. The way of analysis of the spherical multi-bar mechanism used in this paper can be widely applied in design and practical applications.

Multiple bifurcated reconfiguration of double-loop metamorphic mechanisms with prismatic joints

The design and analysis of multi-loop metamorphic mechanisms are challenging in the research of metamorphic mechanisms. Inspired by the parallelogram mechanism, this paper proposes a metamorphic mechanism by adding a link to the parallelogram mechanism and changing the properties of some kinematic joints. The metamorphic mechanism has two loops and is composed of six links connected by six revolute joints and one prismatic joint. The topological structure of the metamorphic mechanism is represented by a directed graph, and the multiple bifurcation of the metamorphic mechanism is analyzed by using screw theory and high-order kinematics. The metamorphic mechanism has six bifurcation points and four different motion branches, including one parallelogram branch, one isosceles trapezoid branch and two oscillating block branches. Meanwhile, by combining these metamorphic mechanisms, some novel metamorphic mechanisms with variable sizes and different configurations can be obtained. The metamorphic mechanism proposed in this paper provides a fresh perspective on how to design new metamorphic mechanisms.