Motion Of Mechanism Research Articles

Reliability calculation and error analysis of VSV adjustment mechanism motion accuracy

The adjustable stator vane (VSV) adjustment mechanism of an aircraft engine was taken as the research object, and a kinematic model with kinematic pair clearance was established. Considering the randomness of factors such as drive error, dimensional error and assembly clearance, a VSV adjustment mechanism motion accuracy reliability model considering the failure correlation of each stator blade motion accuracy was established. The BP neural network proxy model was introduced, and the Monte Carlo method was used to calculate the reliability of the mechanism, and the variation law of the reliability with the number of stator blades and the failure threshold was given. By comparing with the system model with independent unit failure assumptions and the fully correlated system model, the rationality of the mechanism system motion accuracy reliability model considering failure correlation was verified. Finally, a method for estimating the reliability error of the complex system caused by the proxy model error was proposed, and it was proved that the reliability calculation result of the VSV adjustment mechanism is accurate and reliable.

A parallel mechanism-based virtual biomechanical shoulder robot model: Mechanism design optimization and motion planning

This paper presents the design and optimization process of a Virtual Biomechanical Shoulder Robot Model (VBSRM) based on a 6-4 parallel mechanism. To address the challenges posed by parallel manipulators and the specific biomechanical constraints of the shoulder joint, a comprehensive design analysis is conducted. First, a kinematic model of the VBSRM is developed, followed by an investigation of its geometric model. To obtain an optimal VBSRM design, performance objectives such as condition number, norm of actuator force, and stiffness are identified and optimized. Initially, only condition number of the robot mechanism is optimized using Genetic Algorithm and performance objectives from the optimal design are analyzed. Later, the three objectives are grouped to form a single function and a single objective-based optimization is also conducted. However, further investigation revealed the conflicting nature of the objectives and hence these were simultaneously optimized using the Non-dominated Sorting Genetic Algorithm (NSGA II). The results obtained from various optimization routines are compared and it is found that the results from the NSGA II provide a better tradeoff between the performance objectives. The motion trajectories from the optimal design of the VBSRM are later analyzed vis-à-vis human shoulder motions for its intended use as a robotic model of the human shoulder joint in various applications.

Parallel 3-RSR Wrist Rehabilitation Mechanism and Motion Performance Analysis

In order to help patients with wrist injuries to carry out recovery training, a simple and portable parallel 3-RSR wrist rehabilitation mechanism was introduced in order to achieve the expected therapeutic effect. Firstly, the parallel 3-RSR wrist rehabilitation mechanism is described. Taking the parallel mechanism as the research object, the degree of freedom is calculated and the pose is solved by analytical method, which verifies the rationality of the mechanism motion. Then, based on the boundary search method, the reachable workspace of the parallel wrist rehabilitation mechanism is analyzed, and the relevant workspace map is drawn. Finally, considering the reasonable optimization of the structural size of the workspace, the results show that the optimized reachable attitude workspace is significantly larger than the initial workspace. This study provides a theoretical reference for the ontology design of rehabilitation institutions.

RSSR Mechanism Design and Motion Control Strategy of a Carbon-Free Vehicle for Obstacle Avoidance Competition

RSSR Mechanism Design and Motion Control Strategy of a Carbon-Free Vehicle for Obstacle Avoidance Competition

Study on hydrodynamic performance of multi-link cycloidal propeller

Cycloidal propellers are special propellers that can obtain a wide range of thrust in any direction without changing the propeller rotation speed or requiring the assistance of a rudder. They are typically installed on ships with high-mobility requirements. The implementation of pure cycloidal blade pitch control is complex, and there are a few control mechanisms capable of realizing these blade pitch motions. In this paper, a multi-link mechanism is designed to control the movement of the blades, and the relationships between blade pitch angle, linkage lengths, and their adjustment angles are established. The linkage lengths and their adjustment angles are solved using a genetic algorithm. The blade pitch angle controlled by the multi-link mechanism matches well with the pure cycloidal pitch angle after adjusting the linkage lengths and adjustment angles. The layout of linkages for the six-blade cycloidal propeller is designed to ensure that there is no motion interference between the linkages and their supporting shafts during operation. The open water hydrodynamic performance of the cycloidal propeller controlled by the multi-link mechanism and pure cycloidal pitch motion is analyzed using computational fluid dynamics. The simulation results indicate that the cycloidal propeller can achieve similar performance with different control mechanisms.

Establishment and analysis of a unified mathematical model of kinematics and dynamics of flexible parallel mechanisms

Abstract The conventional positive solution approach for determining the forward motion of the kinematic mechanism relies primarily on the outcomes of the inverse solution of motion, which is not universally applicable to flexible parallel mechanisms. Furthermore, the process of analyzing the natural frequency of parallel mechanisms is complex, cumbersome, and challenging. More importantly, the two models are independent, and there is no unified mathematical analysis model for flexible parallel mechanisms. Therefore, this paper establishes a unified mathematical model for kinematics and dynamics analysis of flexible parallel mechanisms through an improved multi-body system transfer matrix method. Taking the flexible 3-RPU planar mechanism and the space 2-RPU (2-UPS) space mechanism as examples, respectively, the forward motion solution of the mechanism was analyzed and its working space range and resonance frequency were solved. Finally, the calculation results are compared with the simulation results, and the feasibility and accuracy of the method are proved. Through this method, we can quickly solve the motion characteristics of the mechanism without relying on the results of the inverse solution of the mechanism, which provides suggestions for the precise control of flexible parallel mechanisms and also provides corresponding reference basis for the practical application of flexible parallel mechanisms.

Design and analysis of a new deployable articulated mast mechanism with two-dimensional deploying-folding motion

Abstract A traditional deployable articulated mast mechanism can only provide one-dimensional (1D) deploying-folding motion. This paper aims to investigate the design and analysis of a novel deployable articulated mast mechanism with two-dimensional (2D) deploying-folding motion. Firstly, the topological motion of deployable mast mechanisms can provide 2D deploying-folding motion is analyzed, and a potential rectangular prism linkage unit is presented to construct single degree-of-freedom (DOF) deployable mast mechanisms with 2D deploying-folding motion. Secondly, the kinematics of the new deployable mast mechanism is established based on its structural symmetry and modular features. Thirdly, the deploying dynamics of the new mechanism are built based on the Lagrange equation. Fourthly, the deployed/folded ratio, interference and singularity of the new mechanism are analyzed. Finally, a numerical example is used to illustrate the effectiveness of the theoretical analysis, and a physical prototype is developed to show the fabrication feasibility of the new deployable mechanism. Compared with the traditional counterparts with 1D deploying-folding motion, the new deployable mast mechanism has a larger deployed/folded ratio, which has a good application prospect in space missions to support solar arrays, magnetometers, cameras and antennas.

Type synthesis of novel 1R, 2R, 1R1T, and 2R1T hybrid RCM mechanisms based on topological arrangement and modular design method

Remote center motion (RCM) mechanisms play a significant role in minimally invasive surgery (MIS) to provide geometric constraints to the surgical tool motion. To satisfy the rapid diversified development of the surgical robot in various environment, especially in the head coil, MRI room or other enclosed confined space, this paper focuses on the type synthesis of hybrid-RCM mechanisms using the topological arrangement and modular design method (TAMD). Firstly, the concepts of TAMD are proposed systematically for type synthesis of general hybrid mechanisms. Secondly, TAMD is applied towards the type synthesis of RCM mechanisms to generate their topological arrangement and motion characteristic relationships. Thirdly, main module and secondary modules are designed for RCM mechanisms of four different motions (i.e., 1R, 2R, 1R1T, and 2R1T) based on the proposed topological arrangement. Numerous novel 1R, 2R, 1R1T, and 2R1T RCM mechanisms are then proposed by assembling these main and secondary modules. Finally, one typical case for each motion of RCM mechanisms is taken as an example to validate its motion capability.

Numerical method for the form finding and force analysis of non-prestressed cable-membrane structures with mechanism displacement

The non-prestressed cable-membrane structures exhibit significant nonlinear characteristics such as mechanism displacement and large deformation under external loads. Analyzing such structural behaviors using traditional finite element analysis methods is challenging due to the singularity of the stiffness matrix and the non-convergence of the iterations. In this study, a numerical method based on the vector form intrinsic finite element (VFIFE) method for form finding and force analysis of non-prestressed cable-membrane structures with mechanism displacement is introduced. First, the basic principle and calculation process for analyzing the deformation and internal force of cable-membrane structures are introduced. Second, the applicability of the present method is demonstrated by four numerical examples, including static analysis of the double parabolic inflated membrane and the hemispherical inflated cable-membrane, mechanism motion simulation of the cloth, and large deformation calculation for the flexible curtain. Finally, a spatial non-prestressed cable-membrane model experiment is performed. The effectiveness of VFIFE method is further validated by comparing the measured displacement and internal force to the numerical results. It is shown that the numerical method proposed in this study can effectively simulate the morphological evolution and internal force distribution for the flexible cable-membrane structures with large mechanism displacement, providing a reference for analyzing such practical engineering problems involving strongly nonlinear characteristics.

Structural design and coupling analysis of multimode variable coupling parallel mobile robots

Purpose There is coupling between the branches of mobile parallel robots, similar to traditional parallel mechanisms, but there is currently relatively little research on the coupling problem between the branches of mobile parallel robots. Design/methodology/approach This study optimizes the coupling analysis method of traditional parallel mechanisms, treats the mobile parallel mechanism as a whole, takes the motion of the active pair as input and the overall motion of the mobile parallel mechanism as output and analyzes the input–output characteristics of the mobile parallel mechanism. Moreover, this study applies this theory to a mobile parallel mechanism, designs control logic and finally conducts simulation and physical verification. Findings This study proposes a coupling analysis method suitable for parallel mobile robots and designs the control logic of their active pair based on the results of their coupling analysis. This study designs a multimode variable coupling parallel mobile robot, which can change the coupling of the mechanism by changing its own branch chain structure, so that it can switch between different coupling configurations to meet the different needs brought by different terrains. Originality/value The work presented in this paper propose a method for analyzing the coupling of mobile parallel robots and simplify their control logic by applying coupling theory to the design of mobile parallel robots. This study conducts simulation and physical experiments, thereby filling the gap in the coupling analysis of parallel mobile robots and laying the foundation for the research of uncoupled parallel mobile robots.

Non-probabilistic time-dependent reliability analysis of mechanism motion accuracy based on extreme value response

Non-probabilistic time-dependent reliability analysis of mechanism motion accuracy based on extreme value response

Thermal performance of a motile-microorganism within the two-phase nanofluid flow for the distinct non-Newtonian models on static and moving surfaces

Nanofluid plays a crucial role in addressing the heat transmission challenges facing the industries including chemical processing systems, automobile radiators, spacecraft design, concrete heating, solar thermal conversion systems, etc. Consequently, this research is devoted to analyzing the solar radiation mechanism, thermophoresis and Brownian motion under unique conditions, specifically, temperature gradient within liquids with limiting viscosities or plastic dynamic viscosity at zero and infinite shear rate. To increase the model novelty, a model involving two phases of Casson–Carreau fluid conveying tiny particles is developed to analyze the flow of solar radiation mechanism over stationary and moving surfaces. Furthermore, the impacts of heat generation, chemical reaction and activation energy are also taken into account. The dimensionless equations are solved through numerical methods using the Galerkin-weighted residual technique and analytically employing the Homotopy analysis method with the assistance of MATHMATIACA 11.3 software. Our study reveals that the fluid temperature reduces for greater values of Weissenberg number, and Casson parameter. Additionally, the distribution of gyrotactic microorganisms decreased against the bio-convective Schmidt number and Peclet number.

Force analysis of the planetary-type mechanisms of the enhanced vibration exciters

The planetary-type vibration exciters are relatively novel and prospective types of actuators for various vibratory technological equipment. Numerous research papers substantiated the possibilities of implementing such exciters for generating circular, elliptical, and rectilinear oscillations of the working members of different technological machines. The present research continues the authors’ previous investigations dedicated to kinematics and dynamics of planetary-type vibration exciters and is focused on the analysis of forces, moments, and torques acting upon the elements of the corresponding actuating mechanisms. The research methodology contains the development of the simplified dynamic diagrams of two different designs of planetary-type mechanisms, derivation of the analytical expressions describing force parameters of the considered mechanical systems, performing the mathematical modeling and computer simulation of the mechanism motion in order to analyze the corresponding forces, moments, and torques. The obtained results present the time dependencies of the mentioned force parameters under different operational conditions and design parameters of the planetary-type mechanism. The major scientific novelty of the paper consists in defining the minimal required torque of the motor needed to be applied for driving the mechanism at different conditions. The research outcomes can be effectively used by engineers while developing new and improving existent vibratory technological machines equipped with the considered planetary-type vibration exciter.

Фундаментальний аналіз та оптимізація (мінімізація) динамічних навантажень у пружних елементах механізмів підйому вантажу кранів. Частина І

The fundamental analysis and optimization (minimization) of dynamic loads in elastic elements (ropes) of load lifting mechanisms of cranes used in urban development is carried out. The basis of the analysis and methodology of optimization of motion modes of the mentioned mechanisms is the approach implemented in the classical calculus of variations, namely: the integral functional is minimized, which reflects undesirable properties of the mechanical system. Optimized modes of motion of the crane load lifting mechanism, which is represented in the paper by a mechanical system with a linear function of the position of its elements (the load on the rope and the drive mechanism). The significant influence of motion modes of exactly drive mechanisms on dynamic loads in elastic elements (ropes) of the load lifting mechanism of a city-building crane is shown. Usually separate typical modes of motion optimize only one certain property of the specified mechanism. In many practical cases, it is necessary to select modes of motion that optimize a set of properties of a machine or mechanism (respectively, a crane or a load lifting mechanism of a city-building crane). It is for the selection of such modes of motion of machines and mechanisms that dynamic criteria for their evaluation are needed. All existing criteria for evaluating machines and mechanisms can be conditionally divided into two classes: 1) positional (maximum values of kinematic characteristics of links, dynamic loads, amplitudes and frequencies of oscillations, dynamics coefficients, etc.); 2) integral (rms values of kinematic characteristics of links and dynamic loads, energy costs, etc.). In the work the fundamental analysis of the mentioned criteria is carried out and it is shown that for estimation of motion modes of hoisting machines, as well as mechanisms of cargo lifting cranes (boom, bridge, gantry, city cranes) it is necessary to use integral criteria, because they are the ones that estimate motion during the whole cycle. Integral criteria for evaluating urban construction cranes and load lifting mechanisms are presented, which fully reflect their dynamic properties, motion characteristics and, in particular, minimize dynamic loads on elastic elements (ropes). The results obtained in this study can be further used to clarify and improve the existing engineering methods of calculation of hoisting cranes used in urban planning, as well as their load lifting mechanisms, both at the design stages and in the modes of proper operation.

Mechanism Design and Motion Planning of a Hexapod Curling Robot Exhibited During the Beijing 2022 Winter Olympics Games

When a curling rock slides on an ice sheet with an initial rotation, a lateral movement occurs, which is known as the curling phenomenon. The force of friction between the curling rock and the ice sheet changes continually with changes in the environment; thus, the sport of curling requires great skill and experience. The throwing of the curling rock is a great challenge in robot design and control, and existing curling robots usually adopt a combination scheme of a wheel chassis and gripper that differs significantly from human throwing movements. A hexapod curling robot that imitates human kicking, sliding, pushing, and curling rock rotating was designed and manufactured by our group, and completed a perfect show during the Beijing 2022 Winter Olympics Games. Smooth switching between the walking and throwing tasks is realized by the robot’s morphology transformation based on leg configuration switching. The robot’s controlling parameters, which include the kicking velocity vk, pushing velocity vp, orientation angle θc, and rotation velocity ω, are determined by aiming and sliding models according to the estimated equivalent friction coefficient μequ and ratio e of the front and back frictions. The stable errors between the target and actual stopping points converge to 0.2 and 1.105 m in the simulations and experiments, respectively, and the error shown in the experiments is close to that of a well-trained wheelchair curling athlete. This robot holds promise for helping ice-makers rectify ice sheet friction or assisting in athlete training.

Research on a novel compliant mechanism applied in the vehicle side door latch and stability analysis via Lyapunov exponents

The functional reliability of the vehicle latch is very important and is determined by the internal mechanism’s motion stability. In this paper, a novel compliant mechanism constructed with a novel compliant joint is applied to the vehicle latch, and multiple mode motions of the mechanism realize the newly added electric power release function. The repeatability of mechanism trajectories and phase diagrams of several different periodic motions is creatively regarded as the stability of the compliant mechanism. In this compliant mechanism, the endpoint of the groove-coupler is chosen as a characteristic point and the compliant joint’s spring stiffness kT is taken as the key parameter to obtain trajectories and phase diagram. It is found that all cycle overlapping phase diagrams possess intuitively good repeatability, except in two locally specific regions. Then, Wolf’s numerical calculation method of Lyapunov exponents is utilized to analyze the motion stability of the compliant mechanism. An appropriate range (1.0–1.05 N mm/°) of the joint stiffness kT is obtained, satisfying the stability criterion. Finally, characteristic point trajectory and functional experiments with kT = 1 N mm/° are conducted to verify the motion stability of the compliant mechanism. The method of mechanism motion stability analysis by means of Lyapunov exponents can be applied to other under-actuated mechanisms.

Design, optimization, debugging, and simulation of an agricultural biomimetic hexapod robot

This paper comprehensively studies the model establishment, kinematic analysis, hardware design, software development, and agricultural applications of hexapod robot, laying a solid foundation for their practical application in the agricultural field and proposing prospects for future research and development. This article mainly conducts in-depth research on the mechanical design, kinematic analysis, hardware implementation, software development, and application in the agricultural field of hexapod robots. Firstly, a brief introduction to biomimetic robots will be provided, and a comparative analysis will be conducted on existing common legged robots. Afterwards, use solidworks-2021 for 3D modeling to draw the legs and main structure of the robot. In terms of kinematic analysis, by studying the mechanism structure and motion characteristics of hexapod robot, the forward and inverse kinematic equations are derived, and the gait planning and motion control algorithms of the robot are analyzed in detail. These analyses provide a theoretical basis for the robot's program and actual motion. In terms of hardware, a lightweight and high-performance hexapod robot hardware platform has been designed using mainstream controllers such as Borboardino and ultrasonic sensors. This hardware platform has excellent responsiveness and adaptability, and can efficiently move and operate in complex agricultural environments. In terms of software, a comprehensive control system has been developed, including motion planning, action execution, and obstacle avoidance modules. By integrating triangular gait technology and related algorithms, robot can achieve navigation and obstacle avoidance, and perform tasks such as crop planting and spraying in the agricultural field. The simulation file of the hexapod robot was established using CoppeliaSim software, achieving motion based on the robot body, six legs, and end effectors. Finally, a 3D-printer is used to print and assemble all components, and complete the design through debugging and verification. The hexapod robot is capable of autonomous cruising in farmland, completing tasks such as planting and watering crops, providing efficient and intelligent agricultural production solutions for farmers.

Design and stability analysis of the gear-type mobile mechanism with a single actuator.

Gear mechanism transmits the motion and power of parallel axes, intersecting axes and staggered axes, which has been widely employed in production and life. Gear-type mobile mechanism is a type of robot that can achieve motion through gear transmission. Due to its unique motion mode, it can handle various tasks in certain unconventional environments, such as particularly steep surfaces. Cylindrical gear, bevel gear and non-cylindrical gear are taken as the main parts of the mechanism to form a novel research series, respectively. The models of gear-type mobile mechanism are established in this paper, and the degrees of freedom of the mechanism are briefly calculated based on the screw theory. Simultaneously, the influence of centroid trajectory on motion stability is discussed to solve the possible problem that opposite rotation occur during the movement. Furthermore, the trajectory model of zero moment point is calculated considering the motion of the gear-type mobile mechanism. After that, the simulation and experimental analysis of its motion capability show that the gear-type mobile mechanism has excellent characteristics in stability, flexibility and continuity.

Analysis and modeling for the dynamics of the nipper mechanism considering jaw’s impacts

The comber is very important in the spinning for high quality yarns, in which the nipper mechanism (NM) determines the quality of the yarn it combs. This paper is to connect topology and multi-body dynamics to reveal the principle of impact motion of the nipper mechanism. Firstly, the working process of the NM is analyzed and corresponding kinematic models of work sub-phases are derived. Subsequently, the transition from the work phase of the jaw closed to the opened is studied. The research results show that during the transformation process, the mechanism presented another work phase with multiple impacts, which is the main reason why the NM could not stably clamp the cotton clump and thus affect the quality of the yarn combed by the comber. According to the relative coordinate method, the dynamic model of the NM is set up. Combining the classical collision theory and the restitution coefficient equation, the acquisition of the impact impulse generated at the jaw and the subsequent motion of the mechanism are decided. Finally, the NM in the E62 comber is taken as an example to verify the correctness of the established dynamic model, and the influences of different input speeds, restitution coefficients, and stiffness coefficients of spring on the jaw’s impact are studied. This has certain theoretical value for improving the speed and efficiency of the comber.

An innovative approach to teaching engineering graphics focused on CAD/CAM/CAE systems

A new approach to teaching the subject “Engineering Graphics” is developed in the article; it focuses on the use of CAD/CAM/CAE systems as useful tools for solving engineering problems related to mechanical engineering, instead of describing different software options. Thus, the content of the topic is divided into two blocks, one is devoted to the analysis of the results of modeling the motion of dissimilar mechanisms, and the second is devoted to the analysis of various cases of loading structural elements using the FEA module. Both blocks are available in Autodesk Inventor Pro, and students can download it for free. So, students can visualize and understand the complexity of the design process in engineering.