Multi-linkage Mechanism Research Articles

Hydrodynamic Performance of Cycloidal Propellers with Four-Bar and Mixed Four-bar/Five-bar Mechanisms: A Numerical Study

Cycloidal propellers constitute a specialized category of underwater propulsion devices, widely employed in vehicles requiring exceptional maneuverability. The parameters of the blade-driving mechanism directly impact the propeller performance. Hence, the effect of variations in the geometric parameters of the blade-driving mechanism on the hydrodynamic performance of cycloidal propellers must be investigated. In this study, a specific set of four-bar and mixed four-bar/five-bar mechanisms are taken as examples, and the effect of linkage-length variations on the hydrodynamic performance of cycloidal propellers was analyzed using numerical simulation methods. First, we established a physical model of the cycloidal propeller, and then derived the relationship between blade-rotation and revolution angles. Subsequently, by solving the Navier–Stokes equations and employing computational fluid dynamics simulations based on viscosity, an analysis is conducted to reveal the trends in the impact of different linkage-length combinations on the hydrodynamic performance of the cycloidal propeller. Finally, the outcomes of the numerical simulations are interpreted using the wing element theory. In similar blade-driving mechanisms, the effects of varying linkage lengths on propeller hydrodynamic performance are determined through alterations in the blade rotation angle range and equilibrium position. An increase in the range of the blade-rotation angle significantly enhances the hydrodynamic performance of the cycloidal propeller. This research employs a more realistic auto-propulsion mode for numerical simulations, establishing a mapping relationship between the blade-driving mechanism and hydrodynamic performance of the cycloidal propeller, while analyzing the underlying influencing mechanisms. Furthermore, crucial numerical simulations and theoretical foundations are employed for designing the four-bar and mixed four-bar/five-bar mechanism cycloidal propellers. The findings of this study could also be used in similar cycloidal propellers with multilinkage mechanism.

Modeling and Simulation of Theoretical Digging Force of an Excavator Based on Arbitrary Posture

Theoretical digging force is an important performance parameter of the hydraulic excavator. Due to the multi-linkage mechanism, the digging posture of an excavator is ever-changing; thus, it is not easy to calculate the theoretical digging force. Traditionally, the theoretical digging force is calculated by selecting a limited number of postures of the excavator based on experience, which cannot reflect the force condition of each posture in the excavation process. In order to calculate the theoretical digging force of any posture in the excavation process, this paper uses the principle of the analytical method to establish a theoretical excavation force mathematical model of bucket excavation and uses Matlab software to solve the theoretical excavation force mathematical models. In order to verify the model’s correctness, the experimental method is used to determine the actual maximum excavation force of the excavator. The test results showed that there was little difference between the actual maximum digging force and the theoretical maximum digging force, which verified the correctness of the theoretical digging force mathematical models and provided a theoretical digging force calculation method and reference for the structural design and optimization of the excavator.

Nonlinear dynamic behavior analysis of multi-linkage mechanism with multiple lubrication clearances

Clearance exists in mechanical equipment, which aggravates the friction and wear in moving pairs and reduces the use accuracy of mechanism. So as to reduce the impact of clearance on industrial equipment, lubricating oil is usually added to the clearance of moving pair. The lubricating oil can effectively reduce the collision and vibration between components and reduce noise. Previous studies mainly concentrated on the research of dry clearance joints, but less on clearance lubrication. At the same time, there is little research on nonlinear characteristic of lubrication clearance. For the sake of studying the impact of lubrication clearance with multiple revolute joints on mechanical system, the dynamic response and nonlinear characteristic of planar six-bar linkage are analyzed. The movement model of lubrication clearance is developed, and lubrication force of lubrication clearance is modeled by modified Pinkus–Sternlicht model. Dynamical model of lubrication clearance of planar six-bar linkage is established by Lagrange multiplier method. The impacts of lubrication, viscosity coefficient, clearance value and driving speed on dynamic of mechanism with lubrication clearance are explored. By drawing bifurcation diagram, phase trajectory diagram and Poincare map, the nonlinear characteristic of mechanism with lubrication clearance is studied.

Modeling and analysing of spring-loaded double parallelogram mechanism using moment balance

Double Parallelogram Lifting Mechanism (DPLM) is a multi-linkage mechanism adopted as the lifting mechanism of the designed robot in this paper. DPLM is designed based on Double Parallelogram Mechanism (DPM), making it a compact and stable multi-linkage mechanism with a low retracted height and a great working height. This paper investigates the condition in which DPLM obtains static equilibrium at any height using Hookean springs and the minimization of the motor’s required torque exertion against the gravitational moment of the weight of the mechanism. A mathematical model describing all the factors involved in moment balancing of DPLM is derived and established in MATLAB and is verified through experiments with a virtual prototype conducted in SOLIDWORKS. The obtained results show that the magnitude of the moment exerted by the tension of a spring can be determined not only by its exact installation positions but also by its D value, which is the difference in the distances between the two installation points of a spring and their respective rotation axes. An optimization method based on minimizing the RMSE of the unbalanced moment for DPLM is introduced.

Анализ особых положений плоского многозвенного рычажного механизма четвертого класса

The planar multi-linkage mechanism of the fourth order, the output rocker of which implements an approximate stopping in one critical position is described in the article. The mechanism consists of three dyads passing through their limit positions in a single duty cycle. That is why the singularity problem is relevant for such mechanisms and should be studied to avoid jamming of links or the appearance of uncontrolled movements. The mathematical model is based on the theory of screws and contains the closed-loop equilibrium equations obtained for the investigated mechanism. Based on the obtained results of the geometry and singularity analyses, it is shown that there are eight different positions in which some joints stop momentarily and then their angular velocity direction changes

A light-weight passive upper arm assistive exoskeleton based on multi-linkage spring-energy dissipation mechanism for overhead tasks

This paper introduces a novel passive type upper arm exoskeletal vest for assisting overhead jobs in industrial environment such as automotive manufacturing centers. The developed upper arm exoskeleton named as Hyundai Vest Exoskeleton (H-VEX) proposes two key mechanical structural elements: (1) an energy-storage multi-linkage mechanism dissipating spring-loaded energy according to angle-increment of a wearer’s upper arm, and (2) a poly-centric shoulder joint mechanism on the transverse plane for its proper alignment with a wearer’s shoulder joint movement. Based on the proposed mechanical structures, H-VEX has effective ergonomic properties which enable it to provide a smooth-increasing upper arm assistive torque according to increment in a wearer’s arm angle up to its target angle without impeding movements in large ranges of motion (RoM). Especially, the critical design parameters of the energy-storage multi-linkage are able to be adjusted to generate customized assistive torque responses, and additionally, this mechanism can be covered in a thin cover frame for beneficial ergonomic & cosmetic reasons. Furthermore, industrial-purposed requirements such as mechanical endurance and cost-effectiveness can be achieved taking advantages of key structures.To verify the effectiveness of H-VEX on overhead works, activation signals of electromyography (EMG) on main corresponding muscles of ten subjects carrying out overhead manipulation tasks were measured and compared with cases without wearing the exoskeletal vest. The statistical analysis on acquired EMG signal indicates that assistive torque provided by H-VEX was shown to significantly decrease activation of the shoulder-related muscles during target tasks.

A Study for Adjustable Riding Position of the Innovation Bicycle Design

This research is about the analysis and design of the user in a wheelchair use posture can be changed. So user can through different sitting posture changes to provide different needs, so the folding design patents for the existing data collection and classification, through the analysis of advantages and disadvantages, further to find the innovative design approach. Finally through the multi linkage mechanism system, change the seat, handlebars and rear position, provide different posture context. In order to reduce the cost, this study is designed to integrate the innovation input mechanism, multi linkage system, through the construction of 10 joints and degrees of freedom of the bicycle frame. Then use 3D software to design of bicycle the size of the frame of innovation, through the three-dimensional CAD model to simulate the mechanism between movement and interference, and to evaluate the 3D The virtual prototype can meet the requirement. It will also enable CAE to analyze and determine the strength and the safety of the bicycle frame structure of ANSYS11.0 stress. Finally, we have integrated design through CAID to make a product appearance, the focus of research is mainly a study of CAD, CAE, CAID integration the production and the completion of a prototype.

Kinematics Analysis of Multi-link Mechanism for Miniature Servo Press Based on Matlab

The degree of freedom for a multi-link drive mechanism of a 50kN miniature servo press was calculated. The kinematics equations of the mechanism was established based on the rod group method. The choice or design basis for rod length and some hinge points were proposed. The multi-linkage mechanism’s line segment model was constructed in SolidWorks and a set of design parameters was obtained that met the requirements. The M file of kinematic equations were wrote and calculated in Matlab and the displacement, velocity and acceleration curve of the slider were obtained. Compared with the crank-slider mechanism, the mechanism has the features of quick return, small return speed, slightly smaller speed and larger acceleration near B.D.C. Therefore, the speed and acceleration characteristics of the mechanism were inferior to the crank-slider mechanism in the case of reverse rotation and higher speed.

自重補償を用いた上向き作業補助装置TasKiの提案

The average age of agricultural workers is aging. We focused on under-trellis work done on crops on the shelf with raising their arms. In the upward work, it is necessary to keep the arm with its own weight of approximately 2 to 4 kg. It is considered to be a cause of fatigue of arms and back. Therefore, in this research, we attempted to reduce the fatigue of the upward work by the weight compensation mechanism that balances the elastic force of the spring and their arms weight. It can compensate for their arms weight by the force of the spring in various postures of the arm at the time of work by using lightweight and highly accurate weight compensation mechanism authors developed. Furthermore, a horizontal multi-linkage mechanism that follows the movement of the shoulder and arm of a human is used. In this way, it is completely pure mechanical and simple structure without a motor and battery, and it can be expected effective in all upward works.

Modelling and Simulation of Kinematics for Planar R-2RRP-RRR Mechanism Based on SimMechanics and Adams

Planner multi-linkage mechanism is widely used in the manufacturing industry. In this paper, a kind of planner R-2RRP-RRR mechanism is researched. The kinematics simulation model is established and implemented for this kind of mechanism based on SimMechanics and Adams respectively. Through simulation, the motion rule for the key part of mechanism is obtained. The simulation results show that this method is effective and efficient when the simulation is implemented for a certain machine system. Meanwhile, it provides a foundation for design and manufacturing of the mechanism in the future.

Modeling and Simulation of Kinematics for Planar R-RRR-RRP Mechanism Based on Assur Rod Group Theory

Planar multi-linkage mechanism is widely used in the manufacturing industry. In this paper, a kind of planar R-RRR-RRP mechanism is analyzed. The kinematics simulation model is established based on assur rod group method and then implemented for this kind of mechanism based on MATLAB/Simulink. Through simulation, the motion rules for the key part of mechanism (the end-effector) are obtained. The simulation results show that this method is effective and efficient when the simulation is implemented for a certain machine system. Meanwhile, it provides a foundation for design and manufacturing of the mechanism in the future.

A Fundamental Study of Wing Actuation for a 6-in-Wingspan Flapping Microaerial Vehicle

This paper investigates the hovering efficiency of the wing-actuation parameters of a flapping microaerial vehicle with a two-degree-of-freedom (2-DOF) driving mechanism, using finite-element analysis based on the arbitrary Lagrangian-Eulerian method (ALE-FEA). A 75-mm-long wing and multilinkage mechanism that consisted of thin plates and films was employed. It generated a flapping motion that consisted of horizontal stroke of the wing and twist around its leading edge, which were activated by the rotations of two motors. The application of the ALE-FEA was successfully extended to the structural behavior of the driving mechanism. The behaviors of the linkage mechanism, the wing, and its surrounding airflow were reproduced numerically. Various parameters were obtained, some of which were difficult to measure in real experiments, such as the pressure distribution on the wing. For cases of 25 combinations of wings' twist angles and flapping periods, lift forces and energy requirements for the motors were determined. Based on these results, the most efficient flapping combination that generated 1 gf lift force was calculated. In contrast with the combination that created the strongest lift force, the combination of a larger twist angle and a faster flapping cycle was found to provide the most efficient flight.