Bar Linkage Research Articles

Trajectory planning of a closed five-bow-shaped bar linkage based on finite Fourier series

With aim to reduce the energy consumption, a trajectory planning method is presented for a closed five-bow-shaped bar linkage, which can be propelled itself by morphing configuration. The objective herein is to optimize the driving joints trajectories within the global feasible region when the linkage rolls along the ground with a desired acceleration. The driving joint trajectories were represented by finite Fourier series, whose coefficients were solved by genetic algorithm to ensure a minimal energy consumption of the linkage. The impact of the number of terms of finite Fourier series on the energy consumption was also discussed through numerical examples. As a result, the energy consumption based on this strategy had been reduced by 19%, comparing with the constant potential energy strategy. A number of terms between six and eight using to denote the joint trajectories are appropriate, because that a small number of terms is incapable of expressing the joint trajectories accurately, whereas, a large number makes the joints to be subjected to vibration shock. At last, simulation on a virtual model and experiments on a prototype were carried out to verify the effectiveness of the proposed method.

A study of the instantaneous centers of velocity for 1-dof and 2-dof planar linkages

This paper presents a detailed study of the instantaneous centers of velocity (henceforth referred to as instant centers) and the lines containing the instant centers for one-degree-of-freedom (1-dof) and two-degree-of-freedom (2-dof) planar linkages with up to 11 links. The focus is on graphical methods to locate secondary instant centers (that is, instant centers which are unknown from inspection and require graphical construction) or the lines containing secondary instant centers. The secondary instant center for a pair of links with one relative degree of freedom is a unique point, and for a pair of links with two relative degrees of freedom the secondary instant center must lie on a unique line. For a 2-dof linkage, the problem of finding the unique locations of the secondary instant centers on these lines is not addressed in this paper (this would correspond to knowing the ratio of the two input velocities). The paper reviews known graphical methods for the 4-bar, 5-bar, 6-bar, and 7-bar linkages and then presents original graphical methods to locate the secondary instant centers for the 1-dof 8-bar and 10-bar linkages, and the lines containing the secondary instant centers for the 2-dof 9-bar and 11-bar linkages.

Improved Sliding Mode Variable Structure Control of Robot Manipulators with Flexible Joints based on Singular Perturbation

This paper discusses the kinematics analysis method of six link mechanism based on virtual prototype technology and Adams. Firstly, the kinematics mathematical model of the six-bar linkage is deduced. Then, based on the design and development process of virtual prototype technology, the virtual prototype model of the six-bar press is established in ADAMS software. Finally, the kinematics simulation analysis is carried out for the model. The proposed method provides a reference for the parametric and optimal design analysis of the multi bar linkage of the mechanical press.

FLAP Heliostat

Heliostats represent a major cost share of concentrating solar power (CSP) plants with central receiver. They are essential for system efficiency and strongly influence maintenance cost and service life. Since CSP facilities require direct solar radiation, suitable installation sites can eminently be found in desert regions. However, dusty conditions may greatly reduce the performance of the plant due to soiling of the heliostat’s reflective surface and / or irreversible degradation caused by abrasive sand particles. A novel heliostat called FLAP, developed specifically for desert environments, is presented in this paper. It was designed with an emphasis on maximum manufacturing and maintenance cost reduction, yet improved service life in mind. The essential innovation of the FLAP heliostat is the patented foldable reflector support structure consisting of two panel sections that are oriented face-to-face when being in lay-down stow position. Folding of the panels is accomplished by means of a mechanism comprising a simple yet effective 4-bar linkage. To avoid costs for additional drives, the device is actuated by the one single central linear actuator that is also used for elevation tracking. Furthermore, wind loads are minimized due to the low profile of the heliostat structure in stow position, resulting in material and hence overall cost savings.

Force-adjustable parallel-occlusion grasper.

During laparoscopic surgery, the operating surgeon grasps sections of the gastrointestinal tract (GIT), including delicate structures, with long (270mm) 5mm diameter graspers. These grasping instruments increase the risk of iatrogenic damage due to crushing of the grasped tissue. This risk is increased significantly by diseases such as bacterial peritonitis and inflammatory bowel disease and reduced but not abolished by using parallel-closing laparoscopic instruments. This study describes the design and laboratory testing of fully developed and tested smart graspers capable of reducing the grasping force used for inflamed tissues and hollow viscera. In an ISO 13485-certified mechanical laboratory and CAD machine workshop, the authors have designed, developed, and evaluated a smart gasper capable of exerting a preselected uniform grasping force on the gastrointestinal tract and other structures/ tissues, through a mechanism incorporated in the handle of the instrument. This enables the control and graded reduction of the grasping force by the incorporation of a compression spring. The authors named the new instrument the force-adjustable parallel-occlusion grasper (FA-POG) because, in addition to applying a uniform force on the grasped bowel/tissue, it also enables the surgeon to select the force before grasping, depending on its physical condition, and pathological state. FA-POG differs from traditional pinch-occlusion grasper in two respects: it exerts a uniform force on the grasped tissue/bowel and enables the operating surgeon to select and apply a predetermined uniform grasping force, ranging from 1 to 5 N, depending on the pathological condition of the bowel/structure. The ISO 13485-certified and fully developed prototype has been subjected to various grasping in-vitro tests using freshly harvested porcine small-bowel segments obtained from a local abattoir, using Instron tensiometry. The authors designed and α/β tested a parallel-occlusion gasper that enables the operating surgeon to select the force before grasping. This grasper design consists of end-effectors jaws with a 4-bar linkage mechanism for wide, uniform parallel-occlusion force, surpassing traditional scissor-type laparoscopic graspers. It incorporates a force-level controller knob, based on a spring-loaded mechanism, enabling surgeon-preselected grip force to prevent excessive grasping. The authors validated the design experimentally using porcine small-bowel segments, optimizing teeth for maximum grip friction to minimize slippage.

Time-dependent reliability analysis of planar mechanisms considering truncated random variables and joint clearances

The dimension variables and joint clearances are key factors affecting the motion accuracy of a mechanism. The existing time-dependent reliability analysis methods usually assume that the dimension variables follow ideal distribution, ignoring the truncation restrictions due to production and manufacturing. In addition, improper handling of the correlation between joint clearance variables leads to inaccurate calculation results. To address the above issues, this paper proposes a time-dependent kinematic reliability analysis method, in which the truncated random variables and joint clearances are comprehensively considered. Firstly, the complex correlation of clearance variables in the motion error function is processed by the dimension reduction method. Then, the truncated variables are converted into truncated standard normal variables. Furthermore, the envelope function method with expansion at the most probable point (MPP) is used to transform time-dependent reliability into time-independent reliability at multiple time points, greatly reducing computational complexity. On this basis, the saddlepoint method is used to fit the motion error cumulative distribution function at each time point, and the upper and lower bounds of failure probability are obtained through the Copula function and second-order narrow reliability bounds. The effectiveness of the proposed method is verified by a typical 4-bar linkage and a single crank double rocker mechanism.

Knee Angle Generation with Walking Speed Adaptation Ability for a Powered Transfemoral Prosthetic Leg Prototype

This paper presents a microcontroller-based solution for generating real-time normal walking knee angle of a powered transfemoral prosthetic leg prototype. The proposed control algorithm was used to determine the prosthetic knee angle by utilizing seven hip angle movement features generated from only the inertia measurement unit (IMU) deployed on the prosthetic socket on the thigh of the same side. Then, a proportional–integral–derivative (PID) controller is developed to control the motor to reach the desired knee angle in real time. Furthermore, a novel parallel four-bar linkage-based master–slave validation framework combining a motion capture system was introduced to evaluate the performance of the knee angle generation on a speed-adjustable treadmill with able-bodied subjects. In the framework evaluation, 3 different walking speeds were applied to the treadmill to validate different speed adaptation capabilities of the prosthetic leg control system, precisely 50 cm/s, 60 cm/s, and 70 cm/s. Through the proposed 4-bar linkage framework, the prosthesis’s movement can simulate able-bodied subjects well with maximum RMSE never exceeding 0.27° in the swing flexion phase, 4.4° to 5.8° in the stance phase, and 1.953° to 13.466° in the swing extension phase. The treadmill results showed that the prosthetic leg is able to perform a normal walking gait following different walking speeds of the subject. Finally, a corridor walking experiment with a bypass adapter was successfully performed to examine the feasibility of real prosthetic walking situations.

Dynamic Modeling and Analysis of Electric Motor With Integrated Magnetic Spring Driving Weaving Loom Application

This article presents the dynamic modeling and analysis of an electric motor with integrated magnetic spring (EMMS) when it is coupled to a weaving loom application. The EMMS can provide the majority part of the oscillating part of the load in a passive way by the magnetic spring. The electric motor provides the average torque and the remaining oscillating part in an active way. This reduces the energy consumption. To create an accurate dynamic model for the EMMS, lookup tables are generated from a finite-element model. Further, a 4-bar linkage mechanism is employed to emulate the behavior of the shedding mechanism of a real weaving loom application. Eventually, the whole system dynamic model was created in Matlab environment. Moreover, a complete experimental setup was constructed to validate the effectiveness of the proposed dynamic model and the EMMS behavior. It is shown that the proposed dynamic model effectively predicts the performance of the EMMS system. Besides, it is proved that the EMMS can effectively reduce the energy consumption of the weaving loom application. The amount of reduction in the energy consumption depends on the designed magnetic spring. For the considered application, it can reach 57%.

A tilting system design and simulation of ground penetrating radar

In this paper, a tilting system of ground penetrating radar by 5R1C 6-bar linkage mechanism is proposed. The kinematic function of hydraulic cylinder and the output angle is given in explicit format. The quasi-static formulation of the tilting system is proposed to calculate the shaft and revolute force. The simulation of mechanism via ADAMS and an experiment is made to verify the design. The maximum stress is exposed in curved shaft and the worst working condition is the tilt condition. It proves the validity of tilting system that both mechanism and hydraulic system work well in the loading condition and unloading condition.

Evolutionary Patterns of Modularity in the Linkage Systems of the Skull in Wrasses and Parrotfish.

The concept of modularity is fundamental to understanding the evolvability of morphological structures and is considered a central framework for the exploration of functionally and developmentally related subsets of anatomical traits. In this study, we explored evolutionary patterns of modularity and integration in the 4-bar linkage biomechanical system of the skull in the fish family Labridae (wrasses and parrotfish). We measured evolutionary modularity and rates of shape diversification of the skull partitions of three biomechanical 4-bar linkage systems using 205 species of wrasses (family: Labridae) and a three-dimensional geometric morphometrics data set of 200 coordinates. We found support for a two-module hypothesis on the family level that identifies the bones associated with the three linkages as being a module independent from a module formed by the remainder of the skull (neurocranium, nasals, premaxilla, and pharyngeal jaws). We tested the patterns of skull modularity for four tribes in wrasses: hypsigenyines, julidines, cheilines, and scarines. The hypsigenyine and julidine groups showed the same two-module hypothesis for Labridae, whereas cheilines supported a four-module hypothesis with the three linkages as independent modules relative to the remainder of the skull. Scarines showed increased modularization of skull elements, where each bone is its own module. Diversification rates of modules show that linkage modules have evolved at a faster net rate of shape change than the remainder of the skull, with cheilines and scarines exhibiting the highest rate of evolutionary shape change. We developed a metric of linkage planarity and found the oral jaw linkage system to exhibit high planarity, while the rest position of the hyoid linkage system exhibited increased three dimensionality. This study shows a strong link between phenotypic evolution and biomechanical systems, with modularity influencing rates of shape change in the evolution of the wrasse skull.

Energy Efficient Electric Drivetrain Employing Magnetic Spring for Weaving Loom Applications

This paper compares three drivetrains for the shedding mechanism of weaving loom applications, which have a strongly oscillating load pattern. The three drivetrains employ a permanent magnet motor without a gearbox. The first drivetrain uses only the electric motor (EM1) while the other two drivetrains use the electric motor with assistance of a separate or an integrated magnetic spring (EM2MS or EMMS respectively). The magnetic spring provides part of the load torque in a passive way. This results in a reduced power consumption. The optimal design and the performance analysis of the machines have been presented for the considered application using a 2D finite element model coupled with an optimization algorithm. To validate experimentally the theoretical results, the EMMS prototype is manufactured and tested with and without an external load. The employed load is a 4-bar linkage that emulates the behaviour of a shedding mechanism of a given weaving loom. It is found that employing a magnetic spring can effectively reduce the power consumption of the drivetrain by more than 40%. However, introducing the magnetic spring reduces the flexibility of the system. In addition, it increases the initial cost. Nevertheless, the higher initial cost of the drivetrain will be paid back by the lower energy consumption.

Synthesis of new suspension mechanisms for two-wheeler vehicles

Now-a-days, because of easy usage and affordability to general population, two-wheeler had become very much popular over four-wheeled vehicles. They are easy to carry everywhere and on varied terrain where other four-wheeler fails. Two-wheeler has a variety of segments like bicycles, dicycles, motorcycles, scooters, and mopeds. Also, required international mandate for electric mobility dictates makeover of two-wheeler segment. Wide acceptability of two-wheeler mobility depends upon rider’s comfort and effortless driving which mainly depends on the vital performance of suspension system, stability, terrain adaptability and ultimately in its design. This study uses ‘Creative design theory’ to generate varieties of mechanisms applicable to suspension system for two-wheeler. Initially, in this paper, we have studied the available suspension mechanisms and generated an atlas of suspension mechanisms for 4, 5, 6 and 7 bar linkage kinematic chains with one and two degrees of freedom. We have generated 33 innovative suspension mechanisms. Out of these mechanisms, we can filter out existing ones to find the novel mechanisms.

Dynamic analysis of a translating five-bar linkage mechanism

In this paper, the dynamic analysis of a translating five-bar linkage mechanism is presented. The dynamic model of the mechanism is developed with the applied force to the crank arm resolved into the two principal planes, that is, x- and y- directions and the resulting reaction forces and moments at the pin joints determined at various translating acceleration of 0, 10, 20, 30 and 40 m/s2 in the direction as well as in the opposite direction of the crank rotation. It was observed that the horizontal reaction forces at the pin joints were decreasing as the translating acceleration increases in the direction of crank rotation while it increases when the acceleration increases in the opposite direction to the crank rotation. It was also observed that the pin joint moments at point A decreases as the translation velocities increases in the crank arm rotation direction while it increases as the acceleration increases in the opposite direction. The converse is the case for pin joint B, while there were no significant differences for pin joint moments at pin joints C and D in all the considered acceleration in both directions. Also, the vertical reaction forces at the pin joints did not change in magnitude as the magnitude and directions of the acceleration were altered. The analysis brings to the fore the importance of the consideration of translating acceleration in the design, development and utilization of five – bar linkage to avoid failure at any of the joints.

Exact 3D Path Generation via 3D Cam-Linkage Mechanisms

Exact 3D path generation is a fundamental problem of designing a mechanism to make a point exactly move along a prescribed 3D path , driven by a single actuator. Existing mechanisms are insufficient to address this problem. Planar linkages and their combinations with gears and/or plate cams can only generate 2D paths while 1-DOF spatial linkages can only generate 3D paths with rather simple shapes. In this paper, we present a new 3D cam-linkage mechanism, consisting of two 3D cams and five links, for exactly generating a continuous 3D path. To design a 3D cam-linkage mechanism, we first model a 3-DOF 5-bar spatial linkage to exactly generate a prescribed 3D path and then reduce the spatial linkage's DOFs from 3 to 1 by composing the linkage with two 3D cam-follower mechanisms. Our computational approach optimizes the 3D cam-linkage mechanism's topology and geometry to minimize the mechanism's total weight while ensuring smooth, collision-free, and singularity-free motion. We show that our 3D cam-linkage mechanism is able to exactly generate a continuous 3D path with arbitrary shape and a finite number of C 0 points, evaluate the mechanism's kinematic performance with 3D printed prototypes, and demonstrate that the mechanism can be generalized for exact 3D motion generation.

Linear Regression Modelling of Actual and Designed Angles of a Four Bar Linkage using MATLAB

The study, linear regression modeling of actual and designed angles of a four bar linkage through MATLAB approach was successfully carried out. The researchers considered actual and designed angles data gotten through Simulink modeling and simulation in the MATLAB command window. The linear regression modeling was achieved using designed angles of +30, +30, -23 and 0 degrees with the corresponding actual position angles of -92.4196, -223.375, 0, +101.66 degrees. The correlation coefficient of -0.7022 and p-value coefficient of 0.2978 from data analysis indicated that there is negative and significant relationship between actual angle and designed positions angles; however, the linear graph showed some region of positive relationship. MATLAB analysis also computed the linear regression model between actual and designed positions angles. The root mean squared error was observed to be 121 with standard error of 65. 234. The P-value 0.2978 and degrees of freedom 2 of the linear regression model generated are consistent with the P-value and degrees of freedom of ANOVA model, that proves correctness of the model. The researchers made the following recommendations: To avoid failure of machines and mechanisms and to minimize operational noise, actual position angles of links must be computed before linkage configuration is carried out, this research can also be done in future using other advanced software for generalization.

"Linear Regression Modelling of Actual and Designed Angles of a Four Bar Linkage using MATLAB"

The study, linear regression modeling of actual and designed angles of a four bar linkage through MATLAB approach was successfully carried out. The researchers considered actual and designed angles data gotten through Simulink modeling and simulation in the MATLAB command window. The linear regression modeling was achieved using designed angles of +30, +30, -23 and 0 degrees with the corresponding actual position angles of -92.4196, -223.375, 0, +101.66 degrees. The correlation coefficient of -0.7022 and p-value coefficient of 0.2978 from data analysis indicated that there is negative and significant relationship between actual angle and designed positions angles; however, the linear graph showed some region of positive relationship. MATLAB analysis also computed the linear regression model between actual and designed positions angles. The root mean squared error was observed to be 121 with standard error of 65. 234. The P-value 0.2978 and degrees of freedom 2 of the linear regression model generated are consistent with the P-value and degrees of freedom of ANOVA model, that proves correctness of the model. The researchers made the following recommendations: To avoid failure of machines and mechanisms and to minimize operational noise, actual position angles of links must be computed before linkage configuration is carried out, this research can also be done in future using other advanced software for generalization.

About dynamics of a workpiece in a transportation mechanism from a robotized system

This paper proposes an approach for kinematic parameters study of a solid body subjected to relative motion into an inertial transportation mechanism which deserves a robotized system. Kinematics of this complex mechanism may be difficult consequently of 0/3/3 structural group presence. The approach presented in paper avoids mentioned inconvenient, making an interesting observation: the complex mechanism as a whole can be thought as an equivalent mechanism, also complex but easier regarding kinematic calculations. This situation is possible for certain dimensional reports of links lengths only, and this new mechanism consists from two four bar linkages connected each another, so that driven link of first is driving link for another. The discussed solid body stands on a sitting plane tied of the connecting rod from second of the four bar above mentioned linkages. The purpose of this study is to describe the horizontal movement of the solid body, taking into account dynamical considerations.

COMPARISON OF ENERGY COST IN TRANSFEMORAL PROSTHESIS USERS USING MECHANICAL FOUR-BAR LINKAGE AND PNEUMATIC SYSTEM PROSTHETIC KNEE JOINTS

Background. The prosthetic knee joint is an essential component of the transfemoral prosthesis. Different types of knee joints are used in transfemoral prosthesis. The different features found in artificial knee joints affecting on different energy costs to prosthesis user during walking. The selection of prosthetic knee joints should be appropriate to the user's needs.Research purposes. To analyze and comparing two types of prosthetic knee joint four bar linkage mechanical and pneumatic system in minimize the energy cost during walking.Research methods. Quantitative descriptive. The participants were 4 men transfemoral prosthesis user. Energy cost calculation is done with five minutes walking test, which is participants observed for 5 minutes by using prosthetic knee joint four bar linkages mechanical and pneumatic system.Results. The results showed that the prosthetic knee joint fourbar linkage pneumatic system decreased the energy cost by decreasing the value of PCI (p <0.05) and the participants's speed was increase significantly affected (p <0.05) compared to the fourbar linkage mechanical.Conclusion. The results show decreased PCI values and increased walking speed in the use of prosthetic knee joint fourbar linkage pneumatic system. It can be concluded that the use of pneumatic knee joints can clinically facilitate prosthesis users during walking.

Fast online reinforcement learning control of small lift-driven vertical axis wind turbines with an active programmable four bar linkage mechanism

Maintaining high power generation for small lift-driven vertical axis wind turbines in a changing wind environment has not been well studied yet, due to the challenges inherited from the unpredictable turbulent flow-blade interaction and complex blade interferences. Herein, a fast online reinforcement learning pitch control using an active programmable four bar linkage mechanism is proposed, making it possible for turbines to quickly adapt to wind changes and maintain high power output in operation. We formulate the pitching mechanism using a drag-link configuration with a variable frame link length into an optimization problem and further solve it by the interior point algorithm under a wide range of tip speed ratios. Then, a parameter explorative policy gradient reinforcement learning method is designed for the turbine to adaptively tune the frame link length. Since the design significantly reduces the number of parameters needed to depict a whole pitch trajectory, the proposed online learning process can converge quickly, making it capable of handling complex wind conditions in an urban environment. The transient behavior overlooked in much of the literature is also studied. Comparisons to two benchmarks have demonstrated that our proposed system has a superior performance.

Development of Air Bearing Stage Using Flexure for Yaw Motion Compensation

This paper presents an air bearing stage that uses flexure for yaw motion compensation. The proposed stage realizes motion in three degrees of freedom (DOF), which are the X, Y, and Θz directions. To work with Θz as the rotational motion of the stage, we applied a flexure consisting of four bar linkages. The stage from a previous study in which flexure is applied to compensate for yaw motion error has the limitation of increasing the structural stiffness of the stage due to the rotational stiffness. In this study, we propose a combination of a new stage structure and flexure to ensure the high structural stiffness of the stage and the very low rotational stiffness of the flexure at the same time. Modeling and design optimization were performed to apply adequate flexure to the proposed stage. Experiments were carried out to verify yaw motion error compensation and the performance of the stage. The proposed stage has a maximum yaw motion error of 0.86 arcsec during the scanning motion and 48 ms settling time, while the stepping motion is improved by 34.2% compared to the previous study.