Slider Crank Research Articles

A compact wrist rehabilitation robot with accurate force/stiffness control and misalignment adaptation

Robots have been demonstrated to assist the rehabilitation of patients with upper or lower limb disabilities. To make exoskeleton robots more friendly and accessible to patients, they need to be lightweight and compact without major performance tradeoffs. Existing upper-limb exoskeleton robots focus on the assistance of the coarse-motion of the upper arm while the fine-motion rehabilitation of the forearm is often ignored. This paper presents a wrist robot with three degrees-of-freedom. Using a geared bearing, slider crank mechanisms, and a spherical mechanism, this robot can provide the complete motion assistance for the forearm. The optimized robot dimensions allow large torque and rotation output while the motors are placed parallel to the forearm. Thus lightweight, compactness, and better inertia properties can be achieved. Linear and rotary series elastic actuators (SEAs) with high torque-to-weight ratios are proposed to accurately measure and control the interaction force and impedance between the robot and the wrist. The resulting 1.5-kg robot can be used alone or easily in combination with other robots to provide various robot-aided upper limb rehabilitation.

Design of the multi-cylinder Stirling engine arrangement with self-start capability and reduced vibrations

The Franchot engine is a double acting Stirling engine that has a freely controllable phase angle and no shuttle and axial conduction losses but is inferior to the Siemens and free piston Stirling engines in terms of its ability to self-start. In addition, the Franchot engine is not widely used with the reliable slider crank mechanism due to vibrations. Here, the multi-cylinder Franchot engine is thermodynamically and mechanically studied with the simple slider crank mechanism with the aim of improving the self-start capability and to reduce the vibrations. Both instantaneous power and engine arrangements are used to judge the mechanical performance for different engine parameters and configurations. The optimal phase shifts and phase angles are derived and it is shown that both are governed by the number of cylinders. The theoretical analysis shows that by increasing the number of cylinders, different engine vibrations are reduced and the engine becomes self-starting. Hence, the Franchot engine can be superior to the Siemens engine, particularly due to the ability to remove the rocking couples for engines with more than two phases. Thus, the engine operation is stabilised and the simple slider crank mechanism can be used with the multi-cylinder Franchot engine.

A finite element model of a 3D dry revolute joint incorporated in a multibody dynamic analysis

In this work a new approach to deal with non-ideal operative aspects of spatial revolute joints by means of a three-dimensional finite element analysis (3D-FEA) is presented. The developed model incorporates the inertia of the joint components and the corresponding material properties. The fact that actual joint mechanical components present dimensional and geometrical deviations resulting from the assembly process and operative conditions lead to frequent modifications relative to the design conditions that are worth analyzing. Such nonconformities include manufacturing tolerances and assembly errors, thermal effects, local deformations and clearances that directly affect the behavior and reliability of a mechanism, as they are typically at the origin of vibrations, noise and wear. In this work, a comprehensive assessment of the current contact force models implemented in the MultiBody Dynamics (MBD) approach is performed with the aim of understanding its main flaws and weaknesses, validating the need of a new model that is able to evaluate with accuracy the contact forces obtained. Finally, a benchmark problem is presented through a 3D slider–crank mechanism, allowing for the recognition of the differences that exist when the problem is analyzed by means of the MBD and FEM formulations. For this purpose, one of the joints is modeled as non-ideal, with both radial and axial clearances, the ultimate goal of which is to combine both approaches and, thus establish a crucial and pioneering connection to solve the contact problem.

Inertial Vibration Characteristics of Track Chassis Caused by Reciprocating Motion of Crank Slider

The crank slider of self‐propelled baling machinery is used for straw compression on the crawler chassis structure. During the reciprocating motion of the crank slider, the inertia of the piston will cause a greater shock to baling machinery. In this paper, the inertia of the crank slider piston was analyzed on crawler chassis. The model and parameter values of the inertia force balance of the crank slider were established by the complete balance method. The test mode was used to analyze the natural mode and mode shape of the piston. The vertical vibration amplitudes of the crawler chassis beam were tested and used to reflect the specific inertial vibration characteristics of the self‐propelled baling machinery caused by the reciprocating motion of the piston. The inertial vibration caused by the reciprocating motion of the crank slider was eliminated by the method of weighting the tail of the track beam. Results indicated that the self‐balancing counterweight of the crank slider was 261.82 kg. The six natural modal frequencies of the piston were 4.62, 17.26, 29.82, 63.85, 83.73, and 141.58 Hz, respectively. During the reciprocating motion of the piston, the first‐order frequency of the piston would be excited by feeding auger excitation frequency of 3.77 Hz and may cause resonance. And, the vertical vibrates of track beam was based on the measuring point 6 as a fulcrum. Adding a counterweight of 265 kg at the end of the track chassis would completely eliminate the self‐propelled baling machinery inertial vibration caused by the reciprocating motion of the crank slider.

Simulation and Experimental Validation of Slider Displacement in Slider Crank Mechanism with Connecting Rod Tolerance and Joint Clearance

In this paper, a simulated analysis and an experimental validation of slider displacement in a slider crank mechanism have been done. Link tolerance and joint clearance have been considered for the analysis since these factors influence robustness of mechanism. A slider crank mechanism has been designed by specifying tolerance of connecting rod and joint clearances at slider-connecting rod and crank–connecting rod joints. Slider displacement simulations have been performed using ADAMS/View software. In order to understand the effect of speed on slider displacement, simulations have been performed at three crank speeds. All simulation results have been validated by performing experiments on the fabricated setup. It has also been observed that the joint clearance influenced variation in slider displacement is higher than the link tolerance and the speed variation. Thus, the robustly designed mechanism could be analyzed by simulating in ADAMS/View by varying the design parameters within specified ranges than by performing experimentation on fabricated setup.

Analysis and robust position control of an electromechanical control actuation system

This study investigates a modified electromechanical actuator for a guided ammunition fin control system. This modification, which is required due to space limitations, is the use of an eccentric type inverted slider crank mechanism instead of a centric type inverted slider crank mechanism. Brushless DC motor-driven mechanism is modeled experimentally. Using the obtained model, the H∞ type robust position controller is synthesized in the simulation environment and applied to the real system in hardware in the loop tests. The effectiveness of the proposed mechanism and the performance of the synthesized robust position controller are verified by comparing the pre-determined performance requirements and the obtained tests results. It has been shown that for a constant volume, the eccentric type mechanism provides about a 7.6% reduction ratio advantage over the centric type mechanism.

An approach for modelling a clearance revolute joint with a constantly updating wear profile in a multibody system: simulation and experiment

An approach for modelling a clearance revolute joint with a constantly updating wear profile in a multibody system is proposed. Before the contact analysis, the continuous geometric shape of the joint bushing is dispersed to obtain a series of uniformly distributed points of a certain density. By analysing the relative positions between the discrete points and geometric centre of the joint pin, the contact area between the bushing and pin can be estimated and the maximum contact depth can be obtained. Then, the normal contact force and the tangential friction force acting on the point of force application are calculated: after an analysis of the contact force, the wear depth on the contact discrete points is calculated based on Archard’s wear model. The location of the contact discrete point is updated to reconstruct the geometric shape of joint bushing. Finally, taking a planar slider–crank mechanism as an example, the wear characteristics and dynamic response of a revolute joint with clearance are studied by numerical simulation and experimental testing. The results verified that the extent of wear on the joint bushing profile is nonuniform, which is related to the kinetic characteristics of the mechanism. Due to wear, the joint clearance is increased, which further affects the dynamic performance of the mechanism.

Self-Balanced Double Horse Head and Rack-And-Pinion Driven Pumping Unit Based on Intermittent Power Supply Control

Considering the shortcomings of beam pumping unit, a kind of mainstream equipment serving in oilfields of China today, also known as “Kowtow Machine”, such as high energy consumption, low efficiency and disturbance caused to grid, a self-balanced double horse head rack-and-pinion driven pumping unit based on intermittent power supply control is put forward by combining the rack and pinion drive with offset crank slider with intermittent power supply motor control. This unit has the following features: (1) having the quick-return characteristics compared with the existing centric mechanism, i.e. slow move during travel under heavy load, and quick return during travel under light load, which are suitable for pumping unit; (2) utilizing the stable drive through rack and pinion, and employing the double horse head structure to keep the vertical downward force applied by counterweight to beam. Moreover, the counterweight is self-balanced, and receives no additional torque at both ends, so as to improve the force applied to beam; (3) using the microcontroller to control the start and stop of motor, which lowers the loss of motor and its power supply system, so as to reduce the consumption of electric power and enhance the utilization rate of equipment. Additionally, pumping unit is disconnected from grid when it is under no load, in order to reduce the impact on and disturbance caused to grid. We have: (1) completed the structural design of this product, which realizes the energy conservation by around 49.52% compared to the conventional beam pumping unit; (2) finished the prototype of the product after conducting a lot of work including mechanical analysis and design, Solidworks 3D modelling and AutoCAD 2D drafting, Simulink simulation, fabrication, assembly and commissioning; (3) performed the test to verify that the power of the prototype is basically consistent with that in the theoretical analysis, which preliminarily meets the expectation; (4) generalized the prospects on the future application and improvement scheme of this product.

Design and Optimization of Tubular Linear Permanent Magnet Generator with Performance Improvement Using Response Surface Methodology and Multi-Objective Genetic Algorithm

Linear generators are electric machines which generate electrical energy from linear movement. Since these machines can lift gear wheel or power train, they have begun to be used widely nowadays. Since their working areas differ according to speed and power characteristic, this study contains design and optimization of tubular linear generator for free piston practices. The design performed response surface optimization through design variables acquired as a result of sizing via interface. The association between the determined design variables and the sizes of generator output was examined. In addition, these sizes were used for objective functions of increasing efficiency, decreasing overall volume and increasing general performance and their optimum values were found by using Multi-Objective Genetic Algorithm. Initial and optimum design data were compared with Ansys Maxwell 2D. With overall performance increase, 22,78% decrease was seen in total mass, while 11,7% decrease was seen in cost. In addition, prototype linear generator was made in line with initial geometry data and it was applied with crank slider mechanism.

Multi-objective optimization of a flexible slider-crank mechanism synthesis, based on dynamic responses

ABSTRACTThis work deals with a multi-body system synthesis. A flexible slider crank mechanism has been investigated as an illustrative application. The main interest is focused on the mechanism design variables’ identification based on its dynamic responses. Three responses have been involved such as the slider velocity, the slider acceleration and the mid-point transversal deflection of the flexible connecting rod. Each of these responses has been embroiled separately in a mono-objective optimization. Subsequently, the multi-objective optimization subsuming these responses has been established. Two different optimization methods have been studied namely the genetic algorithm (GA) and the particle swarm optimization (PSO) technique. It has been proved that the multi-objective optimization presents more accurate results beside the mono-objective optimization. Compared to the GA, the PSO is more powerful and is able to identify the mechanism design variable with better accuracy, in spite of the affordable computational time allowed with the GA optimization.

Dynamic Analysis of Slider-Crank Mechanism with a Cracked Rod

The dynamical equation of the slider-crank mechanism is established by using Lagrange equation and Newton’s second law. The slider-crank mechanism with an open crack rod is investigated and then establishes the equivalent mechanics model by a massless torsional spring to simulate the influence of the crack in the rod, and the mechanism of a cracked rod is divided into two subsystems. The dynamical equation of the slider-crank mechanism with a crack rod is established. Comparing the dynamic analysis results between with and without crack in the rod, the results show that the existence of the crack leads to a great change in the motion characteristics of the slider. The calculated maximum Lyapunov exponent is positive, which shows that the movement of the slider in the crank slider mechanism with a cracked rod is chaotic.

REPEATED CONNECTIONS IN THE SCHEMES OF LINK SLIDER-CRANK MECHANISM OF GRIPPING DEVICE

Purpose. The article is aimed to carry out a structural analysis of gripping device as a mechanism with a variable structure and external unilateral constraints, as well as to determine the number of repeated connections in the internal and external contours in the mechanism diagram, and to recommend the ways to reduce them. Methodology. Solution of the set problem is realized by means of the mechanisms and machines theory using the universal structural theory of Ozols for analyzing the gripping device as a mechanism with internal and external constraints. Findings. The design of schemes of mechanical gripping devices rarely provides for a stage of structural analysis and synthesis of the mechanism. The preference is given to mandatory kinematic and kinetostatic calculations, layout and design. If structural analysis is carried out, then most often it is limited to calculating the number of the mechanism freedom degrees. The ten-link gripping device is built on the basis of coupled parallelogram slider-crank mechanism with a leading slider. The leading slider acts on the connecting rods connected by the rocker with the frame. The connecting rods bear the clamping elements of the gripping device. The added dyads form a parallelogram and provide a plane-parallel movement of the gripping elements of clamp. Structural analysis was performed using structural schemes for two states of the mechanism: before clamping the object and in the state of the clamped object. The main internal structural parameters of the kinematic scheme: the number of links - 10, the number of connections - 13, the number of contours - 4, the mobility - 1, the number of internal repeated connections - 11. The number of external connections - 12, the actual mobility of the mechanism - 1, the working mobility of the mechanism is - 0, the number of lost mobilities of the external body from the action of external connections - 6, the number of external repeated connections - 5. Originality. Structural analysis of the coupled slider crank mechanism of the gripping device as a mechanism of a variable structure with internal and external connections is carried out for the first time. It is performed contour search, analysis and elimination of useless repeated connections in the internal and external contours of the mechanism. Practical value. Practical recommendations for changing the mobility of kinematic pairs are proposed to reduce the number of repeated connections in internal contours and to provide unloading connection in the outer contour of the mechanism.

A novel tolerance analysis method for three-dimensional assembly

Three-dimensional tolerance analysis is increasingly becoming an innovative method for computer-aided tolerancing. Its aim is to support the design, manufacturing, and inspection by providing a quantitative analysis of the effects of multi-tolerances on final functional key characteristics and predict the quality level. This article proposes a novel approach for three-dimensional assembly analysis—a hybridization of vector loop and quasi-Monte Carlo method. The former is used to establish the three-dimensional assembly chain and obtain the assembly function. The latter is adopted to generate n sets of dimensional values according to the distribution of each dimension in chain. The new method is shown to inherit many of the best features of classical vector loop and quasi-Monte Carlo, combining easy-to-obtain assembly function with accurate statistical analysis. For every set of dimensional values, one sample value of a functional requirement can be computed with the Newton–Raphson iterative procedure. A crank slider mechanical assembly is shown as an example to illustrate the proposed method.

Development of constant output–input force ratio in slider–crank mechanisms

ABSTRACTIn the slider–crank mechanism whereby output piston force is produced against an input force at crank pin centre, the output force varies rapidly when the crank changes its position. For the applications that require a constant piston pushing force as in feeder mechanisms, a method is needed for identifying the parameters to keep output force at a constant value for any crank angle position. Hence in this study, two methods are shown for a slider–crank mechanism operating in horizontal plane. In the first one, a manual control process to generate a constant piston force and the resulting errors are demonstrated. In the second one, identifying the parameters of a mechanical controller for a readily available slider–crank mechanism in an open force control process and the associated error state are shown. Then, an approach to optimize the results of open force control is explained. Finally, the developed methods are generalized for any orientation of the whole slider–crank mechanism. A user friendly interface is developed to transform all the processes into a computer programme. The effectiveness of the methods are numerically illustrated on examples. The results of these examples show that ±4% deviation from the required output force can be obtained pending on the user’s ability while the optimized open force control process provides a maximum error of ±0.4% without any user intervention during operation.

Reliability optimization design of a planar multi-body system with two clearance joints based on reliability sensitivity analysis

A general method for reliability sensitivity analysis and reliability optimization design of planar slider crank mechanism with two clearance joints was presented. A continuous contact force model considering energy dissipation was employed to estimate the contact force acting on the clearance joint. The Monte Carlo method was used to analyze the reliability sensitivity. In addition, based on the Kriging method, a surrogate model was constructed with consideration of explicit function expression. The precision and reliability of the presented method have been successfully demonstrated by numerical simulation. The results show that the number and position of clearance joint considered have a great influence on the maximum allowable displacement of the slider. The changing of the reliability sensitivity for the mean and variance of several random variables has certain regularity. Compared with the determinacy optimization design, the reliability optimization design presented here shows better dynamical performances.

An Application of Yaglom's Geometric Algebra to Kinematic Synthesis of Linkages for Prescribed Planar Motion of Oriented Lines

Planar motion coordination of an unoriented line passing through a point or tangent to a conic is a well-known problem in kinematics. In Yaglom's algebraic geometry, oriented lines in a plane are represented with dual numbers. In the present paper, such algebraic geometry is applied in the kinematic synthesis of an inverted slider–crank for prescribed three and four finitely separated positions of the coupler. No previous application of Yaglom's algebraic geometry in the area of linkage kinematic synthesis is recorded. To describe the planar finite displacement of an oriented line about a given rotation pole, new dual operators are initially obtained. Then, the loci of moving oriented lines whose three and four homologous planar positions are tangent to a circle are deduced. The paper proposes the application of findings to the mentioned kinematic synthesis of the inverted slider–crank. Numerical examples show the reliability of the proposed approach. Finally, it is also demonstrated that, for a general planar motion, there is not any line whose five finitely separated positions share the same concurrency point. For the case of planar infinitesimal displacements, the same property was established in a paper authored by Soni et al. (1978, “Higher Order, Planar Tangent-Line Envelope Curvature Theory,” ASME J. Mech. Des., 101(4), pp. 563–568.)

Modelling and validation of a novel continuously variable transmission system using slider crank mechanism

Vehicle transmission system transfers torque and speed from the power source to drive wheels. Continuously variable transmission (CVT) system offers smooth ratio transition where it improves acceleration performance and reduces fuel consumption. Currently, most of the CVT system is actuated by the internal hydraulic circuit where compressibility of oil introduces non-linearity to the system causing difficulty in controlling CVT response. Therefore, a new free-hydraulic CVT system is developed to overcome the shortcomings in existing CVT. The proposed CVT system is designed based on belt-driven type which consists of two sets of variable pulley. Each set of variable pulleys is actuated by an electric motor using slider crank mechanism. The mathematical modelling of CVT mechanism is developed by using Lagrange formulation. The results from this study show that the simulation model of CVT mechanism can produce good performance behaviour in following desired radius position of the real CVT mechanism.

Synthesis of a variable stroke slider crank mechanism for a reciprocating internal combustion engine

Synthesis of a variable stroke slider crank mechanism for a reciprocating internal combustion engine

Concept development and prediction of VCR engine performance using slider crank pin mechanism based on quasi-dimensional combustion modeling

Energy, economy and pollution factor of internal combustion engine profoundly influence the development of the society. It is well known that efficiency of an internal combustion engine increases by compression ratio, and is limited due to knocking and high thermal stress development in the combustion chamber of an engine. On another side, an efficiency of internal combustion engine decreases toward the more top engine speed. Considering this, a concept is proposed which can change its compression ratio with speed. Variation in compression ratio is achieved by a change in stroke length through moving crank pin within the crank. In this paper the mechanism of operation and prediction of performance characteristics of variable compression ratio spark ignition engine with varying speed using quasi-dimensional combustion simulation mode is presented. It was observed that proposed mechanism provides better fuel efficiency at higher engine speed. Further, it is inferred that 3 mm increase in crank length results in 7% increment in thermal efficiency and 8% decrement in brake specific fuel consumption for 13 compression ratio at 6000 rpm.

Modelling and validation of a novel continuously variable transmission system using slider crank mechanism

Vehicle transmission system transfers torque and speed from the power source to drive wheels. Continuously variable transmission (CVT) system offers smooth ratio transition where it improves acceleration performance and reduces fuel consumption. Currently, most of the CVT system is actuated by the internal hydraulic circuit where compressibility of oil introduces non-linearity to the system causing difficulty in controlling CVT response. Therefore, a new free-hydraulic CVT system is developed to overcome the shortcomings in existing CVT. The proposed CVT system is designed based on belt-driven type which consists of two sets of variable pulley. Each set of variable pulleys is actuated by an electric motor using slider crank mechanism. The mathematical modelling of CVT mechanism is developed by using Lagrange formulation. The results from this study show that the simulation model of CVT mechanism can produce good performance behaviour in following desired radius position of the real CVT mechanism.