Six-bar Linkage Mechanism Research Articles

Deep Learning-Driven Analysis of a Six-Bar Mechanism for Personalized Gait Rehabilitation

Abstract Recent advances in robotics and artificial intelligence have highlighted the potential for the integration of computational intelligence in enhancing the functionality and adaptability of robotic systems, particularly in rehabilitation. Designing robotic exoskeletons for the lower limb rehabilitation of post-stroke patients requires frequent adjustments to accommodate individual differences in leg anatomy. This complex engineering challenge necessitates a deep understanding of human physiology, robotics, and optimization to develop adaptive robotic systems and also to swiftly quantify the required adjustments and implement them for each patient. The conventional approaches, which mostly rely on heuristics and manual tuning, often struggle to achieve optimal results. This paper presents a novel method that integrates a genetic algorithm (GA) with a deep learning approach to generate a gait trajectory of the ankle joint from a six-bar linkage mechanism of fixed dimensions. Later, using the same approach, the inverse kinematics solution for this mechanism is also devised whereby, the set of the link dimensions of the six-bar linkage mechanism is obtained for the given gait trajectory of an individual to achieve customization. We simulated the kinematic behavior of the six-bar linkage mechanism within defined mechanical constraints and utilized the generated data for training a feedforward neural network and long short-term memory models. The proposed model, when trained, can produce accurate lengths for the desired gait trajectories in the sagittal plane and vice-versa which further validates our proposed approach for inverse kinematics solution.

A reconfigurable multi-terrain adaptive casualty transport aid base on Watt II six-bar linkage for industrial environment.

Introduction: This paper presents the Reconfigurable Multi-Terrain Adaptive Casualty Transport Aid (RMTACTA), an innovative solution addressing the critical need for rapid and safe pre-hospital casualty transport in industrial environments. The RMTACTA, leveraging the Watt II six-bar linkage, offers enhanced adaptability through six modes of motion, overcoming the limitations of traditional stretchers and stretcher vehicles by facilitating navigation across narrow and challenging terrains. Methods: The RMTACTA's design incorporates two branching four-bar mechanisms to form a compact, reconfigurable Watt II six-bar linkage mechanism. This setup is controlled via a single remote rope, allowing for easy transition between its multiple operational modes, including stretcher, stretcher vehicle, folding, gangway-passing, obstacle-crossing, and upright modes. The mechanical design and kinematics of this innovative linkage are detailed, alongside an analysis of the optimal design and mechanical evaluation of rope control. Results: A prototype of the RMTACTA was developed, embodying the proposed mechanical and kinematic solutions. Preliminary tests were conducted to verify the prototype's feasibility and operability across different terrains, demonstrating its capability to safely and efficiently transport casualties. Discussion: The development of the proposed Reconfigurable Multi-Terrain Adaptive Casualty Transport Aid (RMTACTA) introduces a novel perspective on the design of emergency medical transport robots and the enhancement of casualty evacuation strategies. Its innovative application of the Watt II six-bar linkage mechanism not only showcases the RMTACTA's versatility across varied terrains but also illuminates its potential utility in critical scenarios such as earthquake relief, maritime rescue, and battlefield medical support.

A new passive transfemoral prosthesis mechanism based on 3R36 knee and ESAR foot providing walking and squatting

Researchers have proposed various linkage mechanisms to connect knee and ankle joints for above-knee prostheses, but most of them only offer natural walking. However, studies have shown that people assume a squatting posture during daily activities. This paper introduces a novel mechanism that connects the knee joint with the foot-ankle joint to enable both squatting and walking. The prosthetic knee used is the well-known 3R36, while the energy storing and return (ESAR) prosthetic foot is used for the ankle-foot joint. To coordinate knee and ankle joint movements, a six-bar linkage mechanism structure is proposed. Simulation results demonstrate that the proposed modular transfemoral prosthesis accurately mimics the motion patterns of a natural human leg during walking and squatting. For instance, the prosthesis allows a total knee flexion of more than 140° during squatting. The new prosthesis design also incorporates energy-storing mechanisms to reduce energy expenditure during walking for amputees.

A Dynamic Approach to Low-Cost Design, Development, and Computational Simulation of a 12DoF Quadruped Robot

Robots equipped with legs have significant potential for real-world applications. Many industries, including those concerned with instruction, aid, security, and surveillance, have shown interest in legged robots. However, these robots are typically incredibly complicated and expensive to purchase. Iron Dog Mini is a low-cost, easily replicated, and modular quadruped robot built for training, security, and surveillance. To keep the price low and its upkeep simple, we designed our quadruped robot in a modular manner. We provide a comparative study of robotic manufacturing cost between our proposed robot and previously established robots. We were able to create a compact femur and tibia structure with sufficient load-bearing capacity. To improve stability and motion efficiency, we considered the novel Watt six-bar linkage mechanism. Using the SolidWorks modeling software, we analyzed the structural integrity of the robot’s components, considering their respective material properties. Furthermore, our research involved developing URDF data for our quadruped robot based on its CAD model. Its gait trajectory is planned using a 14-point Bezier curve. We demonstrate the operation of the simulation model and briefly discuss the robot’s kinematics. Computational methods are emphasized in this research, coupled with the simulation of kinematic and dynamic performances and analytical/numerical modeling.

Mechanically Assisted Neurorehabilitation: A Novel Six-Bar Linkage Mechanism for Gait Rehabilitation.

Repeated and intensive gait training can improve muscle strength and movement coordination of patients with neurological or orthopedic impairments. However, conventional physical therapy by a physiotherapist is laborious and expensive. Therefore, this therapy is not accessible for the majority of patients. This paper presents a six-bar linkage mechanism for human gait rehabilitation with a natural ankle trajectory. Firstly, a six-bar linkage mechanism is selected as the original mechanism to construct a gait rehabilitation device. Then the ankle trajectory is formulated as a function of the crank angle. And the rotation angle of the crank is set as a linear function of time. Therefore, constant speed motor is sufficient to control the mechanism. For the dimensional synthesis, the precise point distances of the gait trajectory and the coupler curve are set as objective functions, with the kinematic constraints including in the optimization procedure. To obtain the optimal structure design parameters, a cooperative dual particle swarm optimization algorithm is developed. The results show that the coupler curve matches well with the gait trajectory. The average distance between the 60 precision points is 3.5 mm.

Dimensional Synthesis and Optimization of a Six-Bar Linkage Mechanism for Gait Rehabilitation

Linkage mechanisms, among which most are four-bar linkage mechanisms or six-bar linkage mechanisms, are major parts of robotic gait rehabilitation systems. The dimensional synthesis and optimization of a six-bar linkage mechanism for human gait rehabilitation is described in this paper. The relationship between the limiting position characteristics of linkages and gait trajectory phases need to be analyzed due to the timing requirements of gait training. The process includes (1) path transformation from ankle trajectory to the desired objective path curve, (2) the new dimensional synthesis of the proposed mechanism, (3) optimization and simulation of the proposed mechanism. The coupler curve generated by the mechanism designed with this process and the desired objective pattern are shown to match well with each other, illustrating the feasibility of the presented method.

Towards a miniature self-propelled jellyfish-like swimming robot

Jellyfish uses jet propulsion to achieve a diversity of propulsion modes in the water. In this article, a miniature jellyfish-inspired swimming robot is designed and built, which is capable of executing horizontal and vertical propulsion and maneuvers. In order to imitate the jellyfish in terms of morphology and kinematics, the robotic jellyfish is designed to be comprised of a streamlined head, a cavity shell, four separate drive units with bevel gears, and a soft outer skin encasing the drive units. A combination of four six-bar linkage mechanisms that are centrally symmetric is adopted as the driver to regulate the phases of contraction and relaxation of the bell-shaped body. Furthermore, a triangle wave generator is incorporated to generate rhythmic drive signals, which is implemented on the microcontroller. Through independent and coordinated control of the four drive units, the robotic jellyfish is able to replicate various propulsion modes similar to real jellyfish. Aquatic tests on the actual robot verify the effectiveness of the formed design scheme along with the proposed control methods.

Designing a High-Speed Press with a Six-Bar Linkage Mechanism

This paper describes the design process of a high-speed cutting press with a linkage mechanism in its drive train. The whole process is carried out for a virtual prototype. The kinematic and dynamic properties of the six-bar linkage mechanism are optimised regarding boundary conditions coming from the production process and kinematic requirements. Using a rigid body model, the geometric dimensions and inertia parameters of the links of the mechanism can be determined. A finite-element (FE) model is build up to check the parts’ durability during work load. A verification of main results is realised on an experimental prototype made from rapid prototyping material.

The Optimization Design of Six-bar Linkage Mechanism

At present, multi-bar linkage mechanism is one of the most important directions of mechanical presses’ development. Utilizing the typical multi-linkage drawing mechanism of the plunger slide and compounding its parameters scientifically are a fairly effective way to realize the drawing technology demand. This paper established kinematics mode of the six-bar drawing mechanism by bar-group method, and produced simulated system by Visual Basic, which simulated the actual motion of the mechanism. With the objective function-velocity fluctuation in drawing and drawing depth, using chaos genetic algorithm method, carried out optimization design of the mechanism, and acquired several groups’ data. The optimization results showed that their performance in kinematics was improved greatly and had exceeded the original mechanism. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2863

Blank Holder Force Control System Driven by Servo-Motor

Blank holder force (BHF) control is used to prevent wrinkles of sheet metal in deep drawing process. Based on a novel conception of BHF control technique driven by servo-motor, a new BHF device with six-bar linkage mechanism has been designed and manufactured. Whole control system of the new BHF technique was developed, and the basic structure of the hardware configuration of the system was given. Software analysis, implementation and division of the functional modules have been done. Also, the control software in data acquisition and processing module has been developed in the relevant technology of the BHF control system for the requirements of real-time, stability and accuracy. By the new BHF device combined with the hardware and the software system, the BHF can be regulated accurately variation with the predefined BHF profile in deep drawing process.

Integrated design of legged mechatronic system

This paper presents a system based on the integrated design and experiment for a one degree-of-freedom (DOF) legged mechatronic system (LMTS). A six-bar linkage mechanism, which is derived from a four-bar linkage with a symmetrical coupler point and pantograph into one, is designed, and common controllers are used to control the velocity and position loops.

宇宙ロボット 脚・腕統合リムメカニズム 腕転用脚機構の運動学解析

Human works like handling objects, carrying loads, assembling parts, and cutting parts, are completed by the combination of both leg locomotion and hand manipulation, in the various fields of construction, agricultural fields, factory, and home. The authors propose a new concept for the integration of locomotion and manipulation, “the Integrated Limb Mechanism.” The concept covers the technical fields both of the control integration and of the mechanism integration necessary for the practical working robot.Here, a six-bar linkage mechanism with four degrees of freedom is introduced as an example of integrated limb mechanism with both advantages in leg and in arm with consideration for mechanical design. Computer simulation with the dynamic model is performed to verify the transformability from leg posture into arm posture of the mechanism. The kinematic analysis by the manipulatability ellipsoid is done to evaluate the different motion rates between the leg posture and the arm posture. Some useful tasks are considered suitable to the mechanism.

Generic Models for Designing Dwell Mechanisms: A Novel Kinematic Design of Stirling Engines as an Example

The desirable motion characteristics of mechanisms are so implicit that they are difficult to express analytically. Our design methodology involves development of generic design models through abstractions of entire emotion characteristics. We have developed a finite set of generic models (for straight-line, circular-arc, and dwell mechanisms) that represents the entire design space in the sense that a given design specification falls under at least one of the generic design models. This paper presents the generic design models for four-bar straight-line, circular arc, and six-bar dwell linkage mechanisms. The models presented here provide ready-made designs for many dwell applications. We have also presented a new concept in mechanisms design in which multiple coupler points on a four-bar linkage are used to drive different output dyads resulting in multiple dwell outputs. Finally, a new mechanism for the opposed piston stirling engine is presented to illustrate the use of generic design models and the application of a single-input controlling dual output motions with dwells.

Geometric Analysis and Optimization of a Symmetrical Watt Six-Bar Mechanism

This paper describes the synthesis of a mechanism, with the aim of producing a virtual hinge device whose instantaneous centre varies in position as little as possible, and gives an analysis of the relative instantaneous centres of six bars that form a Watt six-bar linkage mechanism. A new expression of the three-centre theorem is successfully applied to the six-bar linkage mechanism by combining geometric representation with vector analysis. Based on this analysis, a formulation for optimization has been established, and the mechanism has been optimized to minimize the movement of the instantaneous centre of one of the bars. A dimensionless example is given.

On the Dead-Center Positions of Planar Linkage Mechanisms

In dead-center positions, a mechanism loses its mobility and has zero mechanical advantage. Based on the concept of instant centers, we develop a methodology to generate planar linkage mechanisms in dead-center positions. This methodology also can be applied to generate planar toggle linkage mechanisms. All possible configurations of six-bar planar linkage mechanisms, with one degree of freedom, in dead-center positions are listed.

Methods for Determining the Second Accelerations in a Plane Linkage Mechanism with One Degree of Freedom and a Plane Cam Mechanism

Previously, the authors proposed the graphical methods for determining the velocities, accelerations and second accelerations in a plane cam mechanism and a plane linkage mechanism with one degree of freedom. G.H. Martin and M.F. Spotts reported analytical method for determining the velocities and accelerations in a four-bar linkage and a direct-contact mechanism by means of geometry of the complex plane, and only showed the guide to solve a six-bar linkage mechanism. Thereupon, the authors have derived the equations for determining the second accelerations in a plane linkage and a plane cam mechanism by means of complex numbers.

Methods for Determining the Second Accelerations in a Plane Linkage Mechanism with One-Degree of Freedom

W.J.Carter reported the method by which the second accelerations or the change of accelerations in a lever crank mechanism could be solved. His method necessitates the construction of a drawing by means of relative velocity method and the calculation of the third time derivatives of angular motions of crank, and different formulas must be applied considering whether the rotopole for crank and lever is outside the fixed centers or between them. His method, moreover, has defects, namely, errors are likely to occur, and some of the lines in the drawing frequently come outside the paper. Authors derive the general formula of the second acceleration of the driven lever of the plane four-bar linkage mechanism, and propose the graphical method by which the second accelerations in the plane four-bar linkage mechanism can be solved rapidly, simply and accurately. Also it is found that their method can be applied to solve the velocity, acceleration, and second acceleration of any link when those terms of one of the links of multi-bar linkage, especially, sixbar linkage mechanism are given.

Methods for Determining the Second Accelerations in a Plane Linkage Mechanism with One Degree of Freedom

W.J.Carter reported the method by which the second accelerations or the change of accelerations in a lever crank mechanism could be solved. His method necessitates the construction of a drawing by means of relative velocity method and the calculation of the third time derivatives of angular motions of crank, and different formulas must be applied considering whether the rotopole for crank and lever is outside the fixed centers or between them. His method, moreover, has defects, namely, errors are likely to occur, and some of the lines in the drawing frequently come outside the paper. Authors derive the general formula of the second acceleration of the driven lever of the plane four-bar linkage mechanism, and propose the graphical method by which the second accelerations in the plane four-bar linkage mechanism can be solved rapidly, simply and accurately. Also it is found that their method can be applied to solve the velocity, acceleration, and second acceleration of any link when those terms of one of the links of multi-bar linkage, especially, sixbar linkage mechanism are given.

Graphical Method for Determining Accelerations in a Plane Linkage Mechanism with One-Degree of Freedom

Of the graphical methods for determining accelerations in a plane linkage mechanism with one-degree of freedom, the method of projection and the method of closed circuit of vectors are already known. But these methods have the fault that one may mistake in solving a problem because of their complicated procedures and lack of the clear arrangement of their constructions. In this paper, a new graphical method is proposed in order to obtain readily accelerations in the mechanism by applying the method which was already shown by the authors in the paper of The Analysis of Complex Motion in Cam Mechanism. This method is also convenient to solve rapidly and mechanically the actual accelerations in any type of four-bar linkage mechanisms and multi-bar linkage mechanisms, for instance, six-bar linkage mechanisms.

An Application of Six-Bar Linkage to the Thread Take-Up Lever in a Sewing Machine

In the last report, an unsolved problem in the analysis of six-bar linkage mechanisms was studied. In this paper, as the result of the investigation on the synthesis of C-type, the author found a new type of the thread take-up lever used for the sewing machine, employing six-bar linkage which has turning pairs only and whose free end performs an ideal thread take-up motion. Thus a most noiseless operation has been attained.