Four-bar Linkage Mechanism Research Articles

Design of the Drive Mechanism of a Rotating Feeding Device

Component batching can be a source of time waste in specific industrial applications, such as kitting. Kitting operations are usually performed by hoppers, but other devices can be used to optimize the process. In a previous work, a rotary device has been proved to be more efficient than hoppers; such a device allows the kitting and releasing of the components in a single rotatory movement, while traditional hoppers require at least two movements. In this paper, an improvement of such feeding device is proposed. The movement of the rotary device is driven by a four-bar linkage mechanism which is designed through functional synthesis. Thank to the four-bar linkage mechanism, the alternate motion of the rotary distributor is derived from the constant speed of the motor.

Design and dynamic analysis of jumping wheel-legged robot in complex terrain environment.

Wheel-legged robots have fast and stable motion characteristics on flat roads, but there are the problems of poor balance ability and low movement level in special terrains such as rough roads. In this paper, a new type of wheel-legged robot with parallel four-bar mechanism is proposed, and the linear quadratic regulator (LQR) controller and fuzzy proportion differentiation (PD) jumping controller are designed and developed to achieve stable motion so that the robot has the ability to jump over obstacles and adapt to rough terrain. The amount of energy released by the parallel four-bar linkage mechanism changes with the change of the link angle, and the height of the jump trajectory changes accordingly, which improves the robot's ability to overcome obstacles facing vertical obstacles. Simulations and real scene tests are performed in different terrain environments to verify obstacle crossing capabilities. The simulation results show that, in the pothole terrain, the maximum height error of the two hip joint motors is 2 mm for the obstacle surmounting method of the adaptive retractable wheel-legs; in the process of single leg obstacle surmounting, the maximum height error of the hip joint motors is only 6.6 mm. The comparison of simulation data and real scene experimental results shows that the robot has better robustness in moving under complex terrains.

SurgGrip: a compliant 3D printed gripper for vision-based grasping of surgical thin instruments

The online version contains supplementary material available at 10.1007/s11012-022-01594-6.

Design of a Wearable Mechanism With Shape Memory Alloy (SMA)-Based Artificial Muscle for Assisting With Shoulder Abduction

This letter proposes a new mechanism, a four-bar linkage-based support hinge mechanism, for assisting with shoulder abduction with artificial muscle based on a shape memory alloy (SMA). An artificial muscle using the SMA coils is designed to lighten the entire system and support the wearer's movement both actively and passively. It can generate up to 273 N and 180 N with and without energy input, respectively, while weighing only 0.04 kg. Furthermore, to consider the rotation axis shifts of the arm during shoulder abduction, the trajectory of the arm along the shoulder abduction is modeled using the scapulohumeral rhythm, a combined movement of the scapula and humerus. The mechanism is designed to follow the modeled arm trajectory and achieve the required torque to perform shoulder abduction based on a four-bar linkage mechanism. It can generate up to 10.1 Nm and 6.3 Nm of torque with and without energy input, respectively. To verify the assistive effect of the proposed mechanism, electromyography is measured while performing the same exercise requiring shoulder abduction with and without the support of the mechanism. The results show that the proposed mechanism reduces not only muscle load but also fatigue while performing the shoulder abduction.

Mechanism Design and Control of a Winged Hovering Robot With Flapping Angle Constraint

Abstract In this paper, we first presented a four-bar linkage mechanism for actuating the wings in a flapping wing flying robot. After that, given the additional constraints imposed by the four-bar linkage, we parameterized the wing kinematics to provide sufficient control authority for stabilizing the system during 3D hovering. The four-bar linkage allows the motors to spin continuously in one direction while generating flapping motion on the wings. However, this mechanism constrains the flapping angle range which is a common control parameter in controlling such systems. To address this problem, we divided each wingbeat cycle into four variable-time segments which is an extension to previous work on split-cycle modulation using wing bias but allows the use of a constant flapping amplitude constraint for the wing kinematic. Finally, we developed an optimization framework to control the system for fast recovery while guaranteeing the stability. The results showed that the proposed control parameters are capable of creating symmetric and asymmetric motions between the two wings and, therefore can stabilize the hovering system with minimal actuation and flapping angle amplitude constraint.

Design of the Jump Mechanism for a Biomimetic Robotic Frog.

Frogs are vertebrate amphibians with both efficient swimming and jumping abilities due to their well-developed hind legs. They can jump over obstacles that are many or even tens of times their size on land. However, most of the current jumping mechanisms of biomimetic robotic frogs use simple four-bar linkage mechanisms, which has an unsatisfactory biomimetic effect on the appearance and movement characteristics of frogs. At the same time, multi-joint jumping robots with biomimetic characteristics are subject to high drive power requirements for jumping action. In this paper, a novel jumping mechanism of a biomimetic robotic frog is proposed. Firstly, the structural design of the forelimb and hindlimb of the frog is given, and the hindlimb of the robotic frog is optimized based on the design of a single-degree-of-freedom six-bar linkage. A simplified model is established to simulate the jumping motion. Secondly, a spring energy storage and trigger mechanism is designed, including incomplete gear, one-way bearing, torsion spring, and so on, to realize the complete jumping function of the robot, that is, elastic energy storage and regulation, elastic energy release, and rapid leg retraction. Thirdly, the experimental prototype of the biomimetic robotic frog is fabricated. Finally, the rationality and feasibility of the jumping mechanism are verified by a jumping experiment. This work provides a technical and theoretical basis for the design and development of a high-performance amphibious biomimetic robotic frog.

Design and testing a highly backdrivable and kinematic compatible magneto-rheological knee exoskeleton

Lower limb exoskeletons (LLE) have been successfully used in robotic-assisted rehabilitation to reduce the burden of locomotor impairment of disabled people. However, the design limitations of LLE mechanisms, such as the lack of kinematic compatibility relative to the user’s joints and the use of high stiff or heavy actuators, limit the outcomes of treatment and increase the risk of injury. To address these shortcomings, in this work we present the design of the MRKneeExo, a highly backdrivable and kinematically compatible active knee exoskeleton. The powertrain of the system is composed of a BLDC 70 W motor associated with a harmonic drive gearbox and a customized magneto-rheological (MR) clutch. To improve kinematic compatibility with the user’s knee, a crossed four-bar linkage mechanism (FBLM) was optimally designed to follow the trajectory of the instant center of rotation (ICR) of the knee projected in the parasagittal plane where the joint is placed. The MR clutch is used to decouple the motor-reducer from the FBLM, thus enabling high backdrivability. The results showed a small error (<3 mm) between the FBLM and the knee ICR. Furthermore, the MR clutch allowed for low back-drive torque (1.28 N m) compared to the torque to back-drive the motor-reducer (18.51 N m). This paper is presented in a framework that can be generalized to support the design of other knee exoskeletons.

Design and Testing of a Bioinspired Lightweight Perching Mechanism for Flapping-Wing MAVs Using Soft Grippers

Flapping-wing MAVs are starting to emulate the advanced flight maneuverability of insects and birds, however they struggle to achieve a similar aptitude for taking off and landing in challenging cluttered environments. The ability to perch on objects such as branches or metal struts would result in a wide range of potential landing sites, both indoors and outdoors, and would increase the achievable mission duration, thus allowing a more versatile usage of MAVs. While perching is particularly challenging with flapping-wing MAVs, these vehicles are highly promising for complex missions in confined spaces. In this letter a systematic bioinspiration approach was adopted to design a new lightweight perching solution suitable for bird-size flapping-wing MAVs. The proposed concept combines a four-bar linkage mechanism with an active-passive actuation method to achieve a large gripping power at low energy consumption. Additionally it relies on compliant soft grippers inspired by the Fin Ray effect, which lead to a high adaptability to different perching surface textures and shapes. A prototype of the proposed concept was manufactured and tested experimentally in gripping tests and rail-guided perching tests. With a total mass of 45 g the concept is suited for bird-size MAVs in the weight range of 150–300 g. Flight tests on a surrogate (multirotor) platform demonstrate the approach functions successfully in realistic free-flight conditions.

Error Feedback Method (Efm) Based Dimension Synthesis Optimization for Four-Bar Linkage Mechanism

Error Feedback Method (Efm) Based Dimension Synthesis Optimization for Four-Bar Linkage Mechanism

Development of walking assisting device by mutual assistance among leg joints

As the number of elderly people in Japan increases, the number of people who have difficulty in daily walking is increasing. In order to solve this problem, it is required to develop a walking assist device that encourages the user to walk properly. Therefore, by using a link mechanism to mutually assist the torque generated in the knee and ankle to the other, it is possible to realize an auxiliary device that is completed only by the user without using actuators. This can be expected to improve the muscle strength and walking motivation of the user. The equipment manufactured in the previous research had three problems. The first was the heavy weight of the device, the second was the huge size of the device, and the third was that it could not be adapted to the wearer's physique. Therefore, in this research, linkages are made of resin, and the Parallel four-bar linkage mechanism is used to make the device smaller, lighter, and adaptable to the wearer's physique. The ratio of the torque of the hip joint and the knee joint of the manufactured device was investigated by simulation and the mechanical characteristics were verified.

Effect of novel continuous friction model on nonlinear dynamics of the mechanisms with clearance joint

A general methodology for the dynamic modelling and analysis of planar multi-body systems with a continuous friction model in joint clearance is presented. Joint clearance is the critical factor that influences the dynamic response and the performance of mechanisms for high-speed application. In light of recent developments in the joint clearance studies, the number of contact force models has been introduced with ignoring friction continuity. The selection of an appropriate continuous friction model is still challenging and essential, which requires further development. Therefore, a perfect continuous friction model, including the Stribeck effect, static, dynamic and viscous friction terms, is proposed and validated. Investigating the dynamic modelling and analysis of double rocker four-bar linkage mechanisms with frictional revolute clearance joints is presented to investigate friction models' effect when surfaces collide with a non-zero tangential velocity. Unlike the smooth crank input mechanism, a double rocker four-bar linkage mechanism is analysed as a challenging problem in the impact mode. Resolving this concern, the novel friction model avoids discontinuity at zero velocity considering the accurate static friction zone. The results reveal that the novel friction model, compared with the piecewise friction model, is more effective in reflecting the mechanical systems' dynamic behaviour. In order to grasp the nonlinear characteristics of the high-speed four-bar linkage mechanism with our model in joint clearance, the Poincaré portrait, and Fast Fourier transformation plot are employed. It is proved that chaos exists in the dynamic response with the influence of the restitution coefficients and kinetic coefficient of friction.

High-capacity stacking apparatus for thermoforming machine – Part II: Structural design of the adjustable stacker driving mechanism

Part II presents the structural design of a high-capacity adjustable stacker mechanism for thermoforming machines which enables the receival, transport and stacking of cup-like products. It was previously established (please see Part I) that a four-bar linkage mechanism with a one-way clutch is the optimal solution for realizing the intermittent motion of the stacker conveyor. The main objective here is to enable the change of the stacker work parameters, with the goal of changing and adjusting the work stroke of the conveyor. Accordingly, there are two main requirements the solution needs to fulfill. The first is that of the regulation characteristic’s function – the relationship between the change of the work stroke and the change of the regulation parameter, must be linear, and the second is that it allows for regulation within a wide range. Due to this, the adopted solution proposed that two links have variable lengths. The input link should have discreet length values which correspond to different values of the conveyor work stroke, while the output link length should be continuously variable, within a narrow range thus ensuring linear regulation characteristic. Finally, it should be noted that this solution makes the stacker compatible with a wide array of products, which increases the productivity and flexibility, adjusting the stacker to receive a different product can be done quickly and easily and avoiding a halt in the production as it takes less time to adjust the stacker than the thermoforming machine.

Empirical Study of Constraint-Handling Techniques in the Optimal Synthesis of Mechanisms for Rehabilitation

Currently, rehabilitation systems with closed kinematic chain mechanisms are low-cost alternatives for treatment and health care. In designing these systems, the dimensional synthesis is commonly stated as a constrained optimization problem to achieve repetitive rehabilitation movements, and metaheuristic algorithms for constrained problems are promising methods for searching solutions in the complex search space. The Constraint Handling Techniques (CHTs) in metaheuristic algorithms have different capacities to explore and exploit the search space. However, the study of the relationship in the CHT performance of the mechanism dimensional synthesis for rehabilitation systems has not been addressed, resulting in an important gap in the literature of such problems. In this paper, we present a comparative empirical study to investigate the influence of four CHTs (penalty function, feasibility rules, stochastic-ranking, and ϵ-constraint) on the performance of ten representative algorithms that have been reported in the literature for solving mechanism synthesis for rehabilitation (four-bar linkage, eight-bar linkage, and cam-linkage mechanisms). The study involves analysis of the overall performance, six performance metrics, and evaluation of the obtained mechanism. This identified that feasibility rules usually led to efficient optimization for most analyzed algorithms and presented more consistency of the obtained results in these kinds of problems.

Design and Implementation of a Lizard-Inspired Robot

The purpose of this paper is to design a lizard-inspired robot driven by a single actuator. Lizard-inspired robots in previous studies had the issue of slippage of their supporting legs. To overcome this issue, a lizard-inspired robot consisting of a four-bar linkage mechanism was designed. The purpose of this paper was achieved through three processes. The first process was kinematic analysis, where the turning angle and stride length of the robot were analyzed. The kinematic analysis results were verified via numerical simulations. The second process was the design and fabrication of the robot. For the robot’s design, both a shuffle-walking method utilizing a claw-shaped leg mechanism and a sliding-rod mechanism for equipping the actuator on the robot’s own coordinates were designed. The third process was experimental verification. The first experimental result was that the claw-shaped leg mechanism was capable of generating an 85.26 N difference in the static frictional force in the longitudinal direction. The other three experimental results were that the robot was capable of driving with 3.51%, 3.16%, and 3.53% error compared to the kinematic analyses, respectively.

Design and optimization of exoskeleton structure of lower limb knee joint based on cross four-bar linkage

This research introduces the knee exoskeleton system that assists in knee joint rehabilitation, which is centered on human wearing comfort. According to the bionic principle, this paper proposes a bionic knee exoskeleton structure based on a cross four-bar linkage mechanism. The cross four-bar linkage mechanism is used to simulate the internal cruciate ligament of the human knee joint to realize the instantaneous rotation center movement of the knee joint. The motor drives the telescopic rod to simulate the movement of the exoskeleton of the knee joint by the thigh muscle of the human body. The auxiliary limit locking structure simulates the knee joint patella to prevent hyperextension of the exoskeleton of the knee joint. The particle swarm-based algorithm is used to optimize the size and position of the connecting rod of the cross four-bar linkage to follow the motion of the human knee joint better. The results show that the optimized and synthesized cross four-bar linkage mechanism has a small average error value, which can better reproduce the anthropomorphic motion characteristics of the human knee joint, achieve an ideal match between the motion form of the human knee joint and the exoskeleton, and improve coordination and adaptability with human joint movement. Through the wearer test, it is found that the structure has a variable instantaneous center of rotation trajectory. Under the condition of satisfying the flexion angle and torque of the human body, the knee joint movement could be simulated with the optimal trajectory to achieve the consistency with the human knee joint movement, so as to alleviate the discomfort of the wear movement of the patients in the auxiliary rehabilitation process, and it provides an advantage for the wear comfort of the human rehabilitation movement.

A new non-probabilistic time-dependent reliability model for mechanisms with interval uncertainties

This paper proposes a new non-probabilistic time-dependent reliability model for evaluating the kinematic reliability of mechanisms when the input uncertainties are characterized by intervals. Based on the introduction of the non-probabilistic interval process of motion error, the most probable point of an outcrossing is defined to transform the complicated time-dependent problem into a concisely time-independent problem. A non-probabilistic time-dependent reliability index is proposed to evaluate the kinematic reliability of various mechanisms, and two computational strategies are designed to calculate the index. Then, the proposed reliability model is applied to a numerical example, a typical four-bar linkage mechanism and a car rack-and-pinion steering linkage mechanism, to demonstrate the significance of the proposed reliability model. The results show that the proposed model provides an effective tool for making reliability evaluation of time-dependent problems.

Finite element simulation of frontal plane adaptation using full-foot, split-toe and cam-linkage designs in prosthetic feet.

ABSTRACT Introduction People with lower-limb amputation have problems with balance, falls, residual limb symptoms, functional mobility, and the need for cognitive attention during gait. Insufficient prosthetic foot frontal plane adaptability may be partly responsible. Theoretically, prosthetic foot design should allow smooth forward motion of the body mass with minimal correction despite initial ground-foot contact geometry. The purpose of this study is to determine if a cam-linkage articulation, designed for frontal plane prosthetic foot adaptability, improves forward motion on cross-slopes compared with single (full-foot) or double (split-toe) cantilever spring designs, using finite element simulation. Materials and Methods Model construction (material data, geometry, and mesh) and simulations were performed using Ansys LS-Dyna. The cam-linkage mechanism was based on a crossed four-bar linkage mechanism to provide frictionless frontal plane rotation. The cam-linkage was placed in series with a full-foot or a split-toe prosthetic foot and either locked or unlocked during stance phase of simulated gait on level surfaces and 15-degree cross-slopes. The simulation was initiated with foot flat and a proximal mass having a forward velocity of 1 m/s. Rotations and translations were calculated for the proximal mass and mediolateral contact forces at the proximal pylon–body mass connection and were calculated to determine the theoretical effect of the frictionless cam-linkage prosthetic foot on the socket interface. Primary outcomes were lateral deviation, vertical displacement, frontal plane rotation, change in forward velocity (percentage of initial) of the body mass, and maximum and average forces at the pylon–body mass connection. Results During the stance phase of gait on the 15-degree cross-slope, with the cam-linkage locked, the split-toe reduced lateral displacement compared with the full-foot prosthetic foot by 33%. The frictionless cam-linkage decreased lateral displacement by 67% for the full-foot and 50% for the split-toe variations. Vertical displacement and forward velocity were increased by the split-toe locked variation (7.4 mm and 3%, respectively) and also increased with the cam-linkage (7.6 mm and 1.5%, respectively). Frontal plane rotation was reduced with full-foot, frictionless cam-linkage compared with other variations. The frictionless linkage reduced average mediolateral forces at the pylon–body mass connection by approximately one-third compared with a locked linkage with either a full-foot or split-toe variation. Conclusions This finite element simulation study shows that a frictionless cam-linkage with frontal plane adaptability integrated into a prosthetic foot improved mediolateral forces, displacement, and frontal plane angular rotation of the proximal pylon compared with a locked linkage during the stance phase of gait when in contact with a 15-degree cross-slope. These findings may have implications for people using lower-limb prostheses if future studies demonstrate improved gait over uneven ground, or reduced pain, skin breakdown, and the work of walking.

Durability Test Bench Design for Electric Lock of Sliding Door

With the rapid development of automobile industry, electric door locks have widely used in various vehicle doors, especially for sliding doors. Among all performances, durability performance for electric locks is virtual for safety, so miniaturized durability test bench has been designed in the research according to the national standard of electric lock. Firstly, four-bar linkage mechanism has been adopted as the main actuator for the motion track achievement, the real motion track of sliding door can be guaranteed through the verification of ADAMS simulation. Secondly, the compression test has been carried out to calculate the reaction force of door sealing strips, thus the resistance device of test bench for simulating reliable locking process of electric lock has been designed. The miniaturized durability test bench can replace the existing durability test method which only performed by the whole vehicle testing, thus providing a low-cost and reliable test device for relevant manufacturers.

Soft sensor hybrid model of dynamic liquid level for sucker rod pump oil wells

The measurement of the dynamic liquid level is of great importance during the oil-producing process of rod pumping wells. It may affect the production of oil fields and motor efficiency. However, the dynamic liquid level is difficult to detect because of the circumstances in the downhole of rod pump wells. In this paper. Firstly, according to the working principles of the sucker rod pump, the mechanical models of the pumping motor and four-bar linkage mechanism are respectively built. Secondly, for the underground frictions, a mechanical model based on the energy conservation equation is built and then the mechanism model is built between the dynamic liquid level and power of the motor. To improve the accuracy of the mechanism model, a novel method based on an artificial fish swarm algorithm optimization Gaborc-kernel extreme learning machine is used to establish a soft sensor dynamic liquid level error compensation model. The mechanism model is paralleled with the soft sensor model to establish a hybrid model of dynamic liquid level. Eventually, the AFSA-Gaborc-KELM soft sensor hybrid model is verified by using the oil dataset collected from the electrical parameter acquisition equipment. This hybrid model is compared with some other models. In the comparison, the proposed hybrid model has better performance and prediction accuracy for the dynamic liquid level than the BP hybrid model, GA-ELM hybrid model, and LSSVM hybrid model.

Cutting performance by surgical scissors of tubular soft tissues such as blood vessels

Current surgical scissors globally and significantly deform blood vessels when cutting them because of the softness and tubular shape of the vessels, which damages the cut site. In this study, cutting experiments were performed on tubular tissue phantoms, and finite element analysis was conducted to clarify the influence of the scissors configuration on the cutting characteristics. Based on the findings, a new scissors model with a four-bar linkage mechanism is proposed. Cutting experiments showed that the developed scissors significantly suppresses global deformation during cutting.