Slider-crank Linkage Research Articles

Wyznaczanie parametrów kinematycznych agregatu sprężarkowego w zastosowaniach z LPG

The collection and transportation of low-pressure gas released into the atmosphere from the oil fields is important in increasing gas production. This issue, which differs in its actuality, has both economic and pollution preveniton benefits. One such project, led by the UN Development Fund, was successfully implemented in the city of Siyazan, Azerbaijan. An electrically driven compressor unit of NQK-7/1-5 type with two oscillating cylinders is commonly used for such work. On visual inspection of the compressors undergoing repair, it was found that the seals in the pneumatic part and the elements of the cylinder-piston group are completely out of order, the gear teeth in the transmission part are broken, worn, the bearings are destroyed, the belts are torn, etc. Compressors sent for repair are almost always reassembled. A structural-kinematic analysis of the compressor installation was carried out to find out the causes of the existing malfunctions. For this purpose, a kinematic diagram of the conversion mechanism of the compressor – a slider-crank linkage mechanism was drawn up using the method of closed contours from projection equations relative to the X and Y axes, and based on the condition that the rotation angles of the piston and cylinder axes are equal, the instantaneous rotation angle, angular velocity and angular acceleration of the cylinder rotation, as well as instantaneous values of displacement, speed and acceleration of the piston inside the cylinder were found. It was shown that the designer's decision on the selection of the design scheme and determination of the product dimensions, which are one of the main issues in the design of the mechanism, should be made based on the results of the kinematic and dynamic analysis.

Hybrid Optimization Based Mathematical Procedure for Dimensional Synthesis of Slider-Crank Linkage

In this paper, an optimization procedure for path generation synthesis of the slider-crank mechanism will be presented. The proposed approach is based on a hybrid strategy, mixing local and global optimization techniques. Regarding the local optimization scheme, based on the null gradient condition, a novel methodology to solve the resulting non-linear equations is developed. The solving procedure consists of decoupling two subsystems of equations which can be solved separately and following an iterative process. In relation to the global technique, a multi-start method based on a genetic algorithm is implemented. The fitness function incorporated in the genetic algorithm will take as arguments the set of dimensional parameters of the slider-crank mechanism. Several illustrative examples will prove the validity of the proposed optimization methodology, in some cases achieving an even better result compared to mechanisms with a higher number of dimensional parameters, such as the four-bar mechanism or the Watt’s mechanism.

Kinematics of a planar slider-crank linkage in screw form

This paper investigates the forward and inverse kinematics in screw coordinates for a planar slider-crank linkage. According to the definition of a screw, both the angular velocity of a rigid body and the linear velocity of a point on it are expressed in screw components. Through numerical integration on the velocity solution, we get the displacement. Through numerical differential interpolation of velocity, we gain the acceleration of any joint. Traditionally, position and angular parameters are usually the only variables for establishing the displacement equations of a mechanism. For a series mechanism, the forward kinematics can be expressed explicitly in the variable of position parameters while the inverse kinematics will have to resort to numerical algorithms because of the multiplicity of solution. For a parallel mechanism, the inverse kinematics can be expressed explicitly in the variable of position parameters of the end effector while the forward kinematics will have to resort to numerical algorithms because of the nonlinearity of system. Therefore this will surely lead to second order numerical differential interpolation for the calculation of accelerations. The most prominent merit of this kinematic algorithm is that we only need the first order numerical differential interpolation for computing the acceleration. To calculate the displacement, we also only need the first order numerical integral of the velocity. This benefit stems from the screw the coordinates of which are velocity components. The example of planar four-bar and five-bar slider-crank linkages validate this algorithm. It is especially suited to developing numerical algorithms for forward and inverse velocity, displacement and acceleration of a linkage.

Analysis and Performance Evaluation of a 3-DOF Wearable Fingertip Device for Haptic Applications

Wearable fingertip device is a promising form to display haptic stimuli since it provides a lightweight and natural way for operators to grasp or manipulate the objects in the virtual environment. This paper focuses on the analysis and performance evaluation of a wearable fingertip device for haptic applications. The device is equipped with three small servo motors and can provide 3-DOF (degree of freedom) force feedback at fingertip with contact/non-contact capability. It combines a five-bar linkage and a slider-crank linkage, and these two linkages are decoupled, leading to simpler kinematics than some devices with coupled structures. In order to present the device, its mechanical analysis, kinematics analysis, and static force analysis were carried out at first. Then, four experiments were designed and conducted to evaluate the device performance quantitatively. The first experiment aimed to verify the effectiveness in rendering variable stiffness. The second experiment investigated its capability in providing different skin stretch directions for operators. The third experiment evaluated its performance improvement during virtual manipulation. The last experiment aimed to verify the effectiveness in displaying mass information during remote manipulation. The experimental results indicated that this device was capable of rendering various stiffness. It could generate eight clear skin stretch directions. The subjects had better performance during virtual manipulation with cutaneous feedback provided by the device than without cutaneous feedback. The device was also capable of displaying mass information during remote manipulation.

The effect of joint clearance on the dynamic behavior of a needle driver mechanism in a typical sewing machine

PurposeThe purpose of this paper is to investigate the effect of joint clearance on the behavior of a needle driver mechanism (a slider-crank linkage) of a typical sewing machine with an imperfect joint between the coupler and the slider (including needle).Design/methodology/approachIn order to model the clearance, the momentum exchange approach is used. The Lankarani and Nikravesh’s continuous contact force model is used to model the contact force, and the modified Coulomb’s friction law represents the friction between sliding members. The penetration force applied on the needle by fabric is chosen based on an experimental data in the literature. The dynamic response is validated for the existing properties in the literature without considering the penetration force.FindingsIt is shown that the clearance joint made considerable effect on the dynamic response of the system. The rough changes of the needle acceleration and jerk are obvious. The base reaction force changed roughly and did not vary as smooth as that of the mechanism with ideal joint. So, clearance joint in the mechanism could lead to an undesirable vibration in the system. Furthermore, the crank driver must provide a non-smooth moment on the crank to keep the crank rotational velocity constant. Moreover, reducing the clearance size sufficiently could make the dynamic response closer to that of the mechanism with ideal joint. In addition, smoother crank moment could be required if the clearance size is reduced sufficiently. Furthermore, the rough change of the base reaction force which can represent the vibration caused by the mechanism on the fixed frame could be reduced if the clearance size is small enough.Originality/valueLockstitch sewing machine is one of the most common apparel industrial machines. The needle driver mechanism of a sewing machine could have an important role for proper stitch forming. On the other hand, clearances are inevitable in assemblage of mechanisms to allow the relative motion between the members. This clearance is due to machining tolerances, wear, material deformations, and imperfections, and it can worsen mechanism performance such as precision, dynamic behavior and vibration. Unfortunately, despite the importance of the dynamic behavior of the needle driver mechanism from practical point of view, very little publications have focused especially on the investigation of the effect of clearance joint on the dynamic behavior of the sewing machine which could lead to undesired vibration of the system and shorter lifetime as a result. In this paper, the dynamic behavior of the system including, needle velocity and acceleration, crank moment and base reaction force was compared with that of the ideal mechanism. Finally, the effect of clearance size on the dynamic behavior of the system was investigated.

A Mechatronic Loading Device to Stimulate Bone Growth via a Human Knee.

This paper presents the design of an innovative device that applies dynamic mechanical load to human knee joints. Dynamic loading is employed by applying cyclic and periodic force on a target area. The repeated force loading was considered to be an effective modality for repair and rehabilitation of long bones that are subject to ailments like fractures, osteoporosis, osteoarthritis, etc. The proposed device design builds on the knowledge gained in previous animal and mechanical studies. It employs a modified slider-crank linkage mechanism actuated by a brushless Direct Current (DC) motor and provides uniform and cyclic force. The functionality of the device was simulated in a software environment and the structural integrity was analyzed using a finite element method for the prototype construction. The device is controlled by a microcontroller that is programmed to provide the desired loading force at a predetermined frequency and for a specific duration. The device was successfully tested in various experiments for its usability and full functionality. The results reveal that the device works according to the requirements of force magnitude and operational frequency. This device is considered ready to be used for a clinical study to examine whether controlled knee-loading could be an effective regimen for treating the stated bone-related ailments.

A Function Generation Synthesis Methodology for All Defect-Free Slider-Crank Solutions for Four Precision Points

The well-established methodology for slider-crank function generation states that five precision points can be achieved without structural error. The resulting designs, however, do not necessarily satisfy all of the kinematic requirements for designing a slider-crank linkage used in common machine applications such as driving the ram of a mechanical press. First, linkage solutions to the five precision point synthesis problem may need to change circuits to reach the precision points. Second, there is no guarantee that the input crank is fully rotatable. This paper presents a modification to the function generation synthesis methodology that reveals a continuum of defect-free, slider-crank solutions for four precision points. Additionally, the methodology allows the specification of velocity or acceleration at the precision points. Although smaller accelerations at a point of zero slide velocity are associated with longer dwell, a point having zero velocity and acceleration is shown not to be possible. Examples are included to illustrate this kinematic synthesis methodology.

Dynamic Behavior Analysis of the Slider Crank Linkage using ANSYS Workbench and MATLAB Program

This paper is concerned with the study of the kinematic and kinetic analysis of a slider crank linkage using D'Alembert's principle. The links of the considered mechanism are assumed to be rigid. The analytical solution to observe the motion (displacement, velocity, and acceleration), reactions at each joint, torque required to drive the mechanism and the shaking force have been computed by a computer program written in MATLAB language over one complete revolution of the crank shaft. The results are compared with a finite element simulation carried out by using ANSYS Workbench software and are found to be in good agreement. A graphical method (relative velocity and acceleration method) has been also applied for two phases of the crank shaft (q2 = 10° and 130°). The results obtained from this method (graphical) are compared with those obtained from analytical and numerical method and are found very acceptable. To make the analysis linear the friction force on the joints and sliding interface are neglected. All results, in this work, are obtained when the crank shaft turns at a uniform angular velocity (w2 = 188.5 rad/s) and time dependent gas pressure force on the slider crown.

Complete Solution to the Eight-Point Path Generation of Slider-Crank Four-Bar Linkages

We study the synthesis of a slider-crank four-bar linkage whose coupler point traces a set of predefined task points. We report that there are at most 558 slider-crank four-bars in cognate pairs passing through any eight specified task points. The problem is formulated for up to eight precision points in polynomial equations. Classical elimination methods are used to reduce the formulation to a system of seven sixth-degree polynomials. A constrained homotopy technique is employed to eliminate degenerate solutions, mapping them to solutions at infinity of the augmented system, which avoids tedious post-processing. To obtain solutions to the augmented system, we propose a process based on the classical homotopy and secant homotopy methods. Two numerical examples are provided to verify the formulation and solution process. In the second example, we obtain six slider-crank linkages without a branch or an order defect, a result partially attributed to choosing design points on a fourth-degree polynomial curve.

Slider-Cranks as Compatibility Linkages for Parametrizing Center-Point Curves

In synthesizing a planar 4R linkage that can achieve four positions, the fixed pivots are constrained to lie on a center-point curve. It is widely known that the curve can be parametrized by a 4R compatibility linkage. In this paper, a slider-crank is presented as a suitable compatibility linkage to generate the center-point curve. Furthermore, the center-point curve can be parametrized by the crank angle of a slider-crank linkage. It is observed that the center-point curve is dependent on the classification of the slider-crank. Lastly, a direct method to calculate the focus of the center-point curve is revealed.

Transmission ratio based analysis and robust design of mechanisms

This paper proposes an analytical approach to the robust design of mechanisms, to achieve motion and accuracy requirements given a desired transmission ratio and allowable geometrical variations. The focus is on four-bar and slider-crank mechanisms, which are common elements for the transmission of rotary motion, especially over distances, which are too big for the use of conventional elements such as gears, and motion along a predefined guide-curve, which often is a straight line. For many power transmission applications, a constant relation between the motions of an input and corresponding output element is required. For a four-bar linkage, a value of 1 is the only possible constant transmission ratio—achieved when the mechanism has a parallelogram configuration. In the case of a slider-crank linkage a constant transmission ratio can be achieved with a properly designed circular guide-curve, which makes the slider-crank essentially equivalent to a four-bar. In practice, however, as a result of variations in link lengths due to manufacturing tolerances and load-induced or thermal deformations, the transmission ratio for a parallelogram four-bar linkage will deviate substantially from its ideal theoretical value of 1. Even small changes in link lengths due to deformations or joint backlash can cause unacceptable instantaneous transmission ratio variations. The concepts presented are not limited to the design of four-bars and slider-cranks but can also be applied universally in the design of other mechanisms.

Synthesis and Steady-State Analysis of High-Speed Elastic Cam-Actuated Linkages With Fluctuated Speeds by a Finite Element Method

A cam driving a lumped inertia through an elastic slider-crank follower linkage with its actuator, a D. C. motor, has been considered in this work. An iterative procedure utilizing the finite element method developed by Midha et al. (1978) is used to synthesize the cam profile to produce a desired output motion at a given design speed and damping ratio. The elastic deflections induced by the large inertia of the linkage operating at a fluctuated high speed of the driving cam are taken into account in synthesizing the cam profile. Responses of the synthesized linkages are simulated and found to be satisfactory at the design conditions.

Synthesis and Steady State Analysis of High-Speed Elastic Cam-Actuated Linkages by a Finite Element Method

A cam driving a lumped inertia through an elastic slider-crank follower linkage with a curved beam coupler is considered. An iterative procedure utilizing the finite element method developed by Midha et al. (1978) is used to synthesize the cam profile to produce a desired output motion at a given design speed and damping coefficient. Nonlinear terms are neglected producing inhomogeneous, periodic, linear, ordinary differential equations. Responses of the synthesized linkages are simulated and found to be satisfactory at the design conditions.

Synthesis of Harmonic Motion Generating Linkages—Part II: Path and Motion Generation

This paper, a sequel to a companion paper on function generation, discusses the path and motion generation problems in the synthesis of linkages with relatively small input cranks. The point on the floating link (i.e., the coupler of a crank-rocker linkage or the connecting rod in a slider-crank linkage) traces an approximate ellipse. This fact serves as a major distinction between the method described herein and the conventional, more general, synthesis techniques. In other words, only elliptical paths may be generated by the path (or coupler) points in the synthesis of linkages with small cranks. Higher-order path and motion generation, in which velocity, acceleration, slope and the rate of change of slope of the coupler path may be specified, are also addressed in this paper.

Cam Synthesis and Analysis for an Elastic Follower Linkage

A cam driving a single lumped mass through a massless, elastic, slider-crank follower linkage is considered. A technique is developed for synthesizing the cam profile to produce a desired output motion at a given design speed. The procedure takes the elasticity and changing geometry of the linkage into account. Analysis equations are also derived to study the output motion at various speeds. The equation of motion for the output link is found to be a Hill equation whose periodicity depends on the changing geometry of the mechanism.

Inverted Slider Crank, Coupled in Tandem to Another Four Bar, to Generate a Constant Velocity Ratio

Combinations of the inverted slider-crank linkage (i.e., the Whitworth quick-return mechanism) with another of the same sort, with a scotch-yoke mechanism or with a planetary gear, are able to produce excellent function generators having a stationary value of velocity ratio. Various forms are discussed, and graphs of their characteristic motions are shown.

Concerning the trajectory of the center of mass of the four-bar linkage and the slider-crank mechanism

The path of the combined center of mass of a four-bar linkage is shown to be a coupler curve which is similar to a coupler curve of this mechanism. Also, the trajectory of the total center of mass of a slider-crank linkage is shown to be a connecting-rod curve which is similar to a connecting-rod curve of this mechanism. These properties are extended in order to determine the necessary conditions for redistributing the link masses such that the total center of mass of a given linkage remains stationary.