Four-bar Linkage Research Articles

Simulation and Experimental Study on Aerospace Push-button Latch of Planar Four-bar Linkage

This paper analyzes the relevant research on push-button quick-release latch, and presents the dynamic model of a typical push-button latch based on a planar four-bar linkage mechanism. ADAMS software was used to simulate the opening and closing performance of the typical push-button latch. The influence of push angle, push position, push speed and push acceleration on the actual opening force measurement of the product was analyzed, as well as the preload test method of the push-button latch, and the sensor method was recommended to measure the preload force, and tested by experiments. Moreover, this paper analyzes the durability test method of push-button latch, uses the sensor to detect the change of opening and closing force in the process of durability test and studies the durability test of typical products.

3D Deformation Capture via a Configurable Self-Sensing IMU Sensor Network

Motion capture technologies reconstruct human movements and have wide-ranging applications. Mainstream research on motion capture can be divided into vision-based methods and inertial measurement unit (IMU)-based methods. The vision-based methods capture complex 3D geometrical deformations with high accuracy, but they rely on expensive optical equipment and suffer from the line-of-sight occlusion problem. IMU-based methods are lightweight but hard to capture fine-grained 3D deformations. In this work, we present a configurable self-sensing IMU sensor network to bridge the gap between the vision-based and IMU-based methods. To achieve this, we propose a novel kinematic chain model based on the four-bar linkage to describe the minimum deformation process of 3D deformations. We also introduce three geometric priors, obtained from the initial shape, material properties and motion features, to assist the kinematic chain model in reconstructing deformations and overcome the data sparsity problem. Additionally, to further enhance the accuracy of deformation capture, we propose a fabrication method to customize 3D sensor networks for different objects. We introduce origami-inspired thinking to achieve the customization process, which constructs 3D sensor networks through a 3D-2D-3D digital-physical transition. The experimental results demonstrate that our method achieves comparable performance with state-of-the-art methods.

Development of a Cubic Core Lightweight Panel Using Origami-Kirigami Engineering

Honeycomb core panels are commonly used in industry as lightweight structures. However, because the bond between the face plate and the regular hexagonal core is weak, there are strength problems, such as heat and shear loads. In this study, a new cubic core panel was developed as an alternative to a honeycomb core panel. Unlike conventional honeycomb core panels, cubic cores can be processed from a single flat plate by punching and bending. Through the square contact area between the face plate and the cubic core, a double-bond integral panel structure was assembled using glue and rebates. The cubic core panel had a higher bending stiffness and bonding strength than the conventional honeycomb panel. A three-point bending test was performed on the processed cubic core panel. The relationship between the bending load and the deformation of the cubic core panel was determined. The curved part of the cubic core panel can be easily processed by cutting out a part of the material on one side of the cubic core panel in accordance with the lightweight structure of the curved part. A design formula for the curved part of the cubic core panel was derived using the curvature radius and curvature angle of the actual curved structure. A cubic core molding system was investigated using the parallel movement characteristics of the four-bar link mechanism for future mass production. An important design factor for practical use was obtained by deriving the relational expression between the bending load and plastic displacement.

Determining kinematic parameters of a four-bar linkage

An algorithm for determining the kinematic parameters of a four-bar linkage by a graph-analytical method without constructing plans for the positions of the mechanism, velocities and accelerations is proposed. The results of the implementation of the proposed calculation algorithm in the TURBO BASIC programming environment are presented. The expediency of using this method for calculating the kinematic parameters of flat lever mechanisms is substantiated. Keywords: four-bar linkage, velocity, acceleration, analytical method, calculation algorithm. nurlan1965@list.ru

Experimental method research and miniature durability test-bench design of electric sliding door

With recent enhancements in vehicle electrification, electric sliding doors have received significant research attention; however, the testing methods for the sliding doors components need to be improved. Herein, according to the durability evaluation index of sliding doors, a miniaturized durability test bench is designed for the electronic lock system and sliding door power output mechanism assembly. The motion trajectory of the electronic lock system can be fitted as a circular arc curve through dynamic characteristics analysis; therefore, a four-bar linkage with a flexible link is used to simulate the trajectory. Through the finite element simulation method, the test-bench stress is calculated at room temperature and a high temperature (75°C); this facilitates the selection of an appropriate material (GCr15). This experimental method is an economical, reliable, and accurate scheme to standardize the durability test of the electronic lock system and power output mechanism assembly.

Comparison of Consumed Power and Safety of Two Types of Semi-Automatic Vegetable Transplanter: Cam and Four-Bar Link

The consumed power and safety of cam and four-bar-link semi-automatic vegetable transplanters were analyzed and compared according to the engine speed and planting distances. A measurement system was constructed to obtain the torque, rotational speed, and strain at the corresponding locations of both transplanters. Field tests were conducted at three engine speeds and three planting distances for each type of transplanter. The torque and rotational speed data of the input shaft of the transplanting devices were used to calculate the power consumed during transplanting. The strain data were converted into stress values to calculate the static safety factor and fatigue life. The results show that the torque and consumed power of the cam transplanter were greater than those of the four-bar-link transplanter under similar operational conditions, owing to its rigid and heavier design. The consumed power increased as the engine speed increased for both types. The static safety factor and fatigue life exhibited different values depending on the measurement location with a sufficient safety margin. Although more skill is required in planting distance control owing to its manual adjustment, the four-bar-link type is more economical under similar operating conditions because of its smaller power requirement.

Application of the ellipse of elasticity theory to the functional analysis of planar compliant mechanisms

In the last decades, a wide range of methods have been proposed for the analysis of compliant mechanisms. In this investigation, the theory of the ellipse of elasticity is tailored to the linear kinetostatic analysis of flexible systems. The proposed approach exploits the antiprojective polarity transformations of the conic associated to the generic two-port elastic suspension. According to the presented method, the elastostatic features of flexible elements with complex geometries, and of compliant mechanisms with serial, parallel, and hybrid topologies, can be represented by a unique geometric entity. As a consequence, the deflection analysis problem is reduced to a geometric problem with a straightforward solution. A specific procedure is developed both at the element and at the mechanism levels, to completely describe field of displacements and loads distribution in the elastic suspension. The application of the method is exemplified considering the analysis of different flexures and of a compliant four-bar linkage.

Analysis of the efficiency of advanced methods of in-plane shear testing of highstrength CFRP specimens

The mechanical testing performed to determine shear characteristics of advanced carbon fiber-reinforced plastics (CFRP) can involve significant problems. First of all, this is due to the difficulties in providing uniform distribution of shear stresses in the working area of the specimens, particularly in determining the strength characteristics of advanced polymer composite materials based on high-modulus or highstrength carbon fibers with the ± 45° layup, where the material properties depend not only on the matrix but also on the fiber properties, unlike unidirectional composites. In addition, one can mention a large number of shear test methods and related standards of in-plane shear testing. At the same time, the results of the tests performed according to various standards generally do not comply with each other. In this study the analysis of CFRP shear characteristics obtained from various test methods was performed. The calculated and experimental data of stress-strain distribution for various specimen types were obtained. The experimental results of determining the strength and elastic characteristics of CFRP in the in-plane shear were obtained during the testing of 125 flat specimens made of four brands of CFRP reinforced with the ± 45° plies. None of the standard methods discussed in this study was found to provide uniform distribution of shear stresses in the working area of the test specimen. The strength values closest to the predicted ones were obtained from the specimens made according to ASTM D7078 (GOST R 57207) based on the method of V-notch plate distortion. At the same time, the method of plate distortion in the four-bar linkage (GOST 24778, ASTM D2719) and the losipescu method (ASTM D5379, GOST R 56799) cannot definitely be used to reliably determine the shear strength characteristics of advanced CFRP reinforced with the ± 45° plies.

An experimental comparative study of adaptive sigma-point Kalman filters: Case study of a rigid–flexible four-bar linkage mechanism and a servo-hydraulic actuator

This paper investigates the application, design, and implementation of different adaptive sigma-point Kalman filters for nonlinear dynamic systems. It is a well-known fact that the performance of nonlinear Kalman filters depends on a prior knowledge of system noise statistics. In real-time applications, this knowledge is difficult and in some cases impossible to predefine. Therefore, an adaptation mechanism based on the random weighting method is proposed in this work to estimate, simultaneously, noise covariance and the state of the system. On the other hand, for real time execution, the computational efficiency of such filters should also be considered to minimize the burden on computational resources. Based on these two factors, in this paper, four different variants of the adaptive sigma-point Kalman filter are studied in detail: (I) an Adaptive Unscented Kalman filter (AUKF), (II) an Adaptive Square-root Unscented Kalman filter (ASr-UKF) with an Unscented Transformation sigma-point selection strategy, (III) an Adaptive Scaled Spherical Simplex Unscented Kalman filter (AS3UKF), and (IV) an Adaptive Square-root Scaled Spherical Simplex Unscented Kalman filter (ASr-S3UKF) with scaled spherical simplex sigma-point selection strategy. The performance of these adaptive sigma-point Kalman filters is analyzed here in depth and discussed for application to a simulated rigid–flexible four-bar linkage mechanism and a practical servo-hydraulic actuator setup under different scenarios. The simulation and the experimental results indicated that, for the cases studied in this article, the filters are competitive and present advantages and disadvantages that should be dealt with according to the requirements of the problem.

A bio-inspired foldable-wing wave energy converter for ocean robots

In remote and harsh sea areas, ocean robots are practical tools to replace humans to execute ocean operations. However, limited power supply constrains the performance of ocean robots, especially in terms of duration time and operation range. Inspired by flying fish, a foldable-wing wave energy converter (FW-WEC) is proposed for ocean robots to extract energy from wave. Equipped with the wave-energy wing, the FW-WEC is capable of switching from the WEC mode that possesses large energy capturing surface to the robot mode with the characteristic of compact structure, which allows for the installation on robots. To satisfy the requirements of the wave-energy wing, several foldable structures are considered and evaluated based on the defined performance index. With the serial four-bar linkage selected and adopted, a prototype of FW-WEC is designed, constructed and tested. The hydrodynamic model is established to analysis the motion response of the prototype under regular wave, of which the accuracy is verified compared with experimental results. According to the wave tank experiment carried out under different wave conditions, the maximum power output of FW-WEC reaches up to 2.6 W and the corresponding capture width ratio is calculated to be 8.0 %. The proposed FW-WEC offers a promising solution for the enhancement of endurance capability of ocean robots.

Optimal Design and Dynamic Analysis of a Spring-Actuated Cam-Linkage Mechanism in a Vacuum Circuit Breaker

This study attempted to establish an optimal design and perform dynamic analysis for a spring-actuated cam-linkage composite mechanism in a rated 12 kV, 25 kA vacuum circuit breaker (VCB). The optimal design of the VCB mechanism involves two steps: the first step involves the optimal design of the stiffness of closing springs and the cam profile, based on three-order polynomial motion curve of the follower; the second step involves the optimal design of a four-bar linkage. To minimize the surplus work in the VCB operating mechanism, the overall difference between the general output force and general resistant force of the VCB operating mechanism during the closing operation was adopted as the objective function to be minimized. Furthermore, the differential evolution algorithm with the golden ratio (DE-gr), an efficient and accuracy metaheuristic algorithm, was employed as the optimization method. The dynamic analysis of the optimal operating mechanism was conducted using a MATLAB-coded program and verified by the multibody dynamic software MSC-ADAMS. The dynamic analysis revealed that the optimal design of the VCB mechanism can considerably decrease the average closing velocity of the movable contact and the Hertz stress between the contact surface of the cam and the roller follower.

Design and control of intelligent bionic artificial hand based on image recognition.

At present, the popular control method for intelligent bionic prosthetic hands is EMG control. However, the control accuracy of this method is low. It is a trend to integrate computer vision into the prosthetic hand. The purpose of this paper is to design an intelligent prosthetic hand based on image recognition, improve the control accuracy and the quality of life of the disabled. Convolutional neural network is used to recognize the object to be grasped, and the recognition result is used as a trigger signal to control our intelligent prosthetic hand. We have designed a four-bar linkage mechanism and a side swing mechanism in the structure, which can not only achieve the flexion and extension of fingers but also realize the adduction and abduction of the four fingers and the lateral swing of the thumb. Through the method of image recognition, the new intelligent bionic hand can achieve five kinds of Human action. Including grasp, side pinch, three-finger pinch, two-finger pinch, and pinch between fingers. The experiment result proves that the precision of image recognition control is very excellent, the intelligent prosthetic hand can be completed the corresponding task.

Design and Analysis of Transformable Wheel-legged Mobile Robot

Wheeled mobile robot has good ground motion ability, fast moving speed and low energy consumption, but poor obstacle surmounting performance. In order to make the mobile robot have the motion performance in complex environments, the wheel mechanism and the wheel-leg mechanism are coupled and designed, and a deformable wheel-leg structure is designed. The mobile robot can not only move in the wheel mode, but also switch to the wheel-leg mode to adapt to the complex motion environment. The deformable wheel-leg mechanism is composed of a four-bar linkage, and the static analysis of key components is carried out in ANSYS.

Ergonomic dual four-bar linkage knee exoskeleton for stair ascent assistance.

Introduction: Robotic exoskeletons are emerging technologies that have demonstrated their effectiveness in assisting with Activities of Daily Living. However, kinematic disparities between human and robotic joints can result in misalignment between humans and exoskeletons, leading to discomfort and potential user injuries. Methods: In this paper, we present an ergonomic knee exoskeleton based on a dual four-bar linkage mechanism powered by hydraulic artificial muscles for stair ascent assistance. The device comprises two asymmetric four-bar linkage mechanisms on the medial and lateral sides to accommodate the internal rotation of the knee and address the kinematic discrepancies between these sides. A genetic algorithm was employed to optimize the parameters of the four-bar linkage mechanism to minimize misalignment between human and exoskeleton knee joints. The proposed device was evaluated through two experiments. The first experiment measured the reduction in undesired load due to misalignment, while the second experiment evaluated the device's effectiveness in assisting stair ascent in a healthy subject. Results: The experimental results indicate that the proposed device has a significantly reduced undesired load compared to the traditional revolute joint, decreasing from 14.15N and 18.32N to 1.88N and 1.07N on the medial and lateral sides, respectively. Moreover, a substantial reduction in muscle activities during stair ascent was observed, with a 55.94% reduction in surface electromyography signal. Discussion: The reduced undesired load of the proposed dual four-bar linkage mechanism highlights the importance of the adopted asymmetrical design for reduced misalignment and increased comfort. Moreover, the proposed device was effective at reducing the effort required during stair ascent.

Retractable Undercarriage Design for a Quadcopter

In the current paper, design of a foldable undercarriage for quadcopter is suggested and investigated. The deploying/retracting mechanism comprises a four-bar linkage. The mechanism lowermost configuration forms a kinematic lock. A solution to complex variable equations has been worked out to put together the mechanism geometry. In addition, a 3D CAD model has been developed to visualize the design better.

Development of a computer program for dimensional synthesis of a four-bar mechanism that generates a prescribed trajectory

This work aims to develop a computational tool for synthesizing a four-bar linkage mechanism that can generate a prescribed path for a point coupler link to follow. The dimensional synthesis of the mechanism involves determining the lengths of each of its links. In this case, two possible configurations are evaluated: crank-rocker and/or double crank. The prescribed path consists of an arbitrary number of points contained in a plane, along with the corresponding rotation degrees of the driver element. Dimensioning the mechanism involves many variables, and it is possible to obtain various configurations that generate paths that are approximately the desired path. Therefore, the synthesis problem arises as an optimization problem in which the objective function seeks to minimize the Euclidean norm between the prescribed points and the points earned. To solve the optimization problem, a user-friendly computer program called SIDIGETRA was developed using the genetic algorithms numerical technique. Design constraints were imposed to obtain an open configuration of the mechanism and to avoid branching defects, order, and Grashof. The program's proper functioning was validated by comparing the results obtained in case studies published in a research article in which the genetic algorithms technique was also applied. The percentage relative errors between the coordinates of the obtained points and prescribed points were calculated and found to be satisfactory. Additionally, the results generated by SIDIGETRA were validated with a visual comparison between the prescribed trajectory and the one obtained by simulating the position analysis of the synthesized mechanism using a commercial software tool designed for this purpose.

Using a 3D-Printed Hand Orthosis to Improve Three-Jaw Chuck Hand Function in Individuals With Cervical Spinal Cord Injury: A Feasibility Study.

Individuals with cervical spinal cord injury (C-SCI) often use a tenodesis grip to compensate for their hand function deficits. Although clinical evidence confirms that assistive devices can help achieve hand function improvements, the currently available devices have some limitations in terms of their price and accessibility and the difference in the user's muscle strength. Therefore, in this study, we developed a 3D-printed wrist-driven orthosis to improve the gripping effect and tested the feasibility of this device by assessing its functional outcomes. A total of eight participants with hand function impairment due to a C-SCI were enrolled, and a wrist-driven orthosis with a triple four-bar linkage was designed. The hand function of the participants was assessed before and after they wore the orthosis, and the outcomes were assessed using a pinch force test, a dexterity test (Box and block test, BBT), and a Spinal Cord Independence Measure Version III questionnaire. In the results, before the participants wore the device, the pinch force was 0.26 lb. However, after they wore the device, it increased by 1.45 lb. The hand dexterity also increased by 37%. After 2 weeks, the pinch force increased by 1.6 lb and the hand dexterity increased by 78%. However, no significant difference was observed in the self-care ability. The results showed that this 3D-printed device with a triple four-bar linkage for individual with C-SCI improved pinch strength and hand dexterity in these patients, but did not improve their self-care ability. It may help patient in the early stages of C-SCI to learn and use the tenodesis grip easily. However, the usability of the device in daily life needs further research.

A robotic fish capable of fast underwater swimming and water leaping with high Froude number

Natural underwater species outperform man-made underwater vehicles in many aspects. In this work, as our first effort to eventually mimic flying fish, a robotic fish capable of swimming fast and leaping out of water was developed, named KUFish. The thrust of KUFish was produced by a tail-beating mechanism driven by a DC motor in combination with reduction gears, four-bar linkage, and pulley-string mechanisms. The passive dynamic stability was implemented by the symmetric mass distribution, positive buoyancy, and lower center of gravity. A series of swimming experiments indicated that the KUFish could swim 0.68 m and leap out of the water with a speed of 1.35 m/s (6.1 BL/s) at an instant of 0.68 s after release. In addition to experimentation, a two-dimensional dynamic model was developed to predict the swimming behavior of the robot. The proposed dynamic model could reasonably capture the measured swimming performance of the robot before water leaping. The water leaping capability of the KUFish can be well supported by the computed Froude number of (1.08 or 0.92) in terms of the body faring length or robot length, respectively. The results from the current work can be useful for developing a flying-fish-like swimming robot in the future.

Design of a Felid-like Humanoid Foot for Stability Enhancement.

The foot is an important part of humanoid robot locomotion that can help with shock absorption while making contact with the ground. The mechanism of the foot directly affects walking stability. A novel foot mechanism inspired by the toes of felids is proposed. The foot has four bionic modules with soft pads and sharp claws installed at the four corners of a flat foot. This foot can reduce the impact experienced during foot landing and increase the time that the foot is in contact with the ground, which can improve the adaptability of the robot to different ground surface conditions with different levels of stiffness. The main structure of the bionic module is a four-bar linkage consisting of a slide way and a spring. Furthermore, the length of the four-bar linkage and the posture of the claw during insertion into soft ground are optimized to improve the stability and buffering performance. The validity of the proposed foot mechanism has been proved in simulations.

Direct Kinetostatic Analysis of a Gripper with Curved Flexures.

Micro-electro-mechanical-systems (MEMS) extensively employed planar mechanisms with elastic curved beams. However, using a curved circular beam as a flexure hinge, in most cases, needs a more sophisticated kinetostatic model than the conventional planar flexures. An elastic curved beam generally allows its outer sections to experience full plane mobility with three degrees of freedom, making complex non-linear models necessary to predict their behavior. This paper describes the direct kinetostatic analysis of a planar gripper with an elastic curved beam is described and then solved by calculating the tangent stiffness matrix in closed form. Two simplified models and different contributions to derive their tangent stiffness matrices are considered. Then, the Newton-Raphson iterative method solves the non-linear direct kinetostatic problem. The technique, which appears particularly useful for real-time applications, is finally applied to a case study consisting of a four-bar linkage gripper with elastic curved beam joints that can be used in real-time grasping operations at the microscale.