Motion Of Mechanism Research Articles

A 3D modular meta-structure with continuous mechanism motion and bistability

Mechanical metamaterials/meta-structures with bistability/multi-stability are of great potential use in engineering applications ranging from shape reconfiguration to impact mitigation. Current designs are mainly based on typical 2D bistable components with two stable states, thus having limited deformation amplitude and stiffness tunability. Here in this paper we propose an innovative 3D modular bistable meta-structure based on two different types of mechanisms with partially compatible motion ranges, which have two distinct ranges of low-stiffness mechanism motion where the two based-mechanisms are kinematically compatible, separated by high-stiffness structural deformation due to the incompatibility between the motion of base-mechanisms. By setting up the mechanism kinematics model and structure mechanics model, we are capable of programming the detailed ranges of mechanism motion and structural deformation, even to obtain a stable state for the meta-structure, while the stiffness transition can also be fine-tuned by adjusting the geometric parameters and hinge stiffness. This work is expected to introduce the concept of multi-stable mechanism as well as open a new revenue for the design of 3D modular metamaterials with customized multi-stability.

Underactuated robotic hand for a fully automatic dishwasher based on grasp stability analysis*

In this study, we propose a fully automatic dishwashing and arranging system. The user simply places the used dishes on the worktop, and the system automatically arranges them in the dish basket and cleans the dishes in the dishwasher. The washed dishes are automatically arranged on the worktop by the system. This eliminates the need to manually load and unload dishes. To realize this system, we develop a novel underactuated robotic hand for grasping multiple shaped dishes stably. The motion of the underactuated mechanism used in the robotic hand for the dishes is modeled, and stability is analyzed. The dimensions of the link used for the underactuated mechanism are determined based on the results. In addition, we conduct grasp experiments for dishes of various shapes, and an experiment on arranging dishes to confirm the effectiveness of the proposed system. The proposed hand is expected to contribute to the full automation of the dishwashing process in restaurants and other commercial kitchens as well as in the standard home.

Overcoming Kinematic Singularities for Motion Control in a Caster Wheeled Omnidirectional Robot

Omnidirectional planar robots are common these days due to their high mobility, for example in human–robot interactions. The motion of such mechanisms is based on specially designed wheels, which may vary when different terrains are considered. The usage of actuated caster wheels (ACW) may enable the usage of regular wheels. Yet, it is known that an ACW robot with three actuated wheels needs to overcome kinematic singularities. This paper introduces the kinematic model for an ACW omni robot. We present a novel method to overcome the kinematic singularities of the mechanism’s Jacobian matrix by performing the time propagation in the mechanism’s configuration space. We show how the implementation of this method enables the estimation of caster wheels’ swivel angles by tracking the plate’s velocity. We present the mechanism’s kinematics and trajectory tracking in real-world experimentation using a novel robot design.

Reconstruction of Velocity Curve in Long Stroke and High Dynamic Range Laser Interferometry.

To study the law that governs the complex movements of the mechanism in the process of automatic weapon operation, the velocity tracking test technology of photon Doppler velocimetry is introduced to accurately measure velocity, displacement and acceleration, on the condition that there are long displacement and rapid velocity change. In the traditional way, out of interference signal time-frequency (TF) transformation draws TF distribution, and then by modulus maxima frequency extraction, comes to the law of velocity change. Due to the influence resulting from the change of fundamental signal as well as that of light intensity signal in the test, based on the TF distribution obtained by TF transformation, the traditional modulus maxima frequency extraction can extract frequency signals, but they show abnormal sudden changes at some moments, making the velocity discontinuous, unsmooth and unreal, which brings obvious errors to the subsequent calculation of acceleration and accurate displacement. Addressing the above-mentioned problems, this paper proposes a ridge extracting correction algorithm based on modulus maxima frequency extraction; this method, based on a large number of experiments where rodless cylinders are used to simulate the motion of a gun automatic mechanism, conducts a detailed calculation and analysis of the experimental results. A comparison of the two algorithms’ processing results, in terms of the speed, displacement and acceleration, suggests that the ridge extracting correction algorithm successfully corrects the frequency selection error, which draws a more continuous and, therefore, effective curve of the velocity change, and by so doing, the error of the displacement test (within 1.36 m displacement) is reduced from more than 3.6% to less than 0.58%, and the uncertainty dropped 97.07%. All these show that the accurate measurement of velocity, displacement and acceleration, with sudden and rapid velocity changes considered, is realized successfully.

Kinematic and dynamic analysis and distribution of stress for seven-item mechanism by means of the SolidWorks program

This paper presents a kinematic and dynamic analysis and distribution of the stress for seven-item planar mechanism by means of the SolidWorks software. The authors of the introduced paper deal with the kinematic analysis of planar mechanisms as well as with the implementation of the vector method into the SolidWorks software program in order to determine the kinematic variables (quantities) of the individual bodies in the whole complex system. The dynamic analysis is performed on the basis of the kinematic analysis. Dynamic analysis allows us to design a system of bodies correctly and it is with the respect to the dynamic loading. For the interpretation of the introduced analysis, the seven-item planar mechanism was selected. Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on time. In relation to the kinematic and dynamic analysis and subsequent simulation of the planar as well as spatial mechanisms, it is perfect solution to use SolidWorks software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modeling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.

Kinematic and dynamic analysis and distribution of stress for six-item mechanism by means of the SolidWorks program

This paper presents a kinematic and dynamic analysis and distribution of the stress for six-item planar mechanism by means of the SolidWorks software. The main purpose of the investigation is connected with the kinematic analysis of planar mechanisms as well as with the implementation of the vector method into the SolidWorks software program in order to determine the kinematic variables of the individual bodies in the whole investigated system. The process of the dynamic analysis is based on the kinematic analysis. The dynamic analysis makes possible to design a system of bodies correctly and it is with the respect to the dynamic loading. For the interpretation of the introduced analysis, the six-item planar mechanism was used as example (representative). Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on time. In relation to the kinematic and dynamic analysis and subsequent simulation of the planar as well as spatial mechanisms, it is great solution to use SolidWorks software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modeling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.

Physical Application of Mechanical Parts and Components Simulate in Receivable Auxiliary Multifunction Mechanical Hand and Claw

Based on the analysis of current office work status and office robots, this paper proposes a design scheme of intelligent mechanical gripper which can transfer data and move objects independently to assist daily office work. It is proposed to design mechanical structure, including mechanism motion design and part structure design, and to use Autodesk Inventor to design and simulate mechanical parts and components. Dimensional and strength checks are carried out on key components, and stress analysis is simulated by using stress analysis module included in Autodesk Inventor. Finally, the mechanical structure design scheme and control system design scheme for the mechanical gripper are proposed. The overall design mainly centers on the functions expected to be completed, and innovates different organizations in combination to achieve the intended objective.

Algorithm for the cams synthesis for the slay mechanism drive

The paper presents an algorithm for the synthesis of the law of motion of the weft beat-up mechanism intended for the production of closely woven fabrics, which are currently manufactured mainly on shuttle looms. These machines have such disadvantages as significant dimensions, strong vibrations and noise during operation, as well as low performance. Shuttleless looms are devoid of such disadvantages. However, production of closely woven fabrics on such machines can face a number of problems, such as increased vibration, the machine tool turning off due to an increased beating-up strip and accelerated wear of mechanisms which, in turn, leads to a lower productivity and product quality. The conducted research allowed developing an algorithm for the synthesis of complex-profile cams of the slay mechanism drive. The use of the developed mechanism is theoretically proved and experimentally confirmed to provide the required performance and quality as well as to significantly expand the range of fabrics produced on STB shuttleless looms.

Stable Discharge Mechanism in Microarc Oxidation and Processing in Phosphate Electrolytes

Microarc oxidation (MAO) is a popular surface treatment process to generate oxide coatings with excellent mechanical properties on valve metals. As a plasma discharge technique, the discharge mechanism in MAO is different from that in the bipolar plate. Due to the alternating arcs and multiple electrolytes in MAO, it is difficult to control and optimize the coating properties. Based on the arcing mechanism and ion motion, the boundary conditions of no-arc discharge, alternating arc discharge, and continuous arc discharge are derived, and the relationship between the discharge current and breakdown current and sustained arc current is investigated. For the same electrolyte, the boundary conditions are determined by equivalent concentration and conductivity. The results show that in the stable alternating arc discharge regime, the higher the concentration and smaller the conductivity, the more intense is the discharge. According to the boundary conditions, MAO experiments are designed using phosphate electrolytes to improve the hardness of oxide coatings. By selecting electrolyte characteristics close to the continuous arc discharge boundary in the stable alternating arc discharge regime, the arc discharge is most intense and brightest and the largest energy is transferred to the Al2O3 coating. Consequently, the crystallinity and mechanical properties are improved significantly.

Simultaneous acquiring and synthesizing images through an optical fiber on a moving mechanism

The research prototypes an optical fiber-scanning mechanism for capturing fiber-acquired multiple images. First, the study develops an image processing firmware embedded in high-speed hardware for image cropping, rotation, sharpening, and stitching, especially synchronizing with the moving mechanism. Then, the embedded firmware successively builds panoramic images while iteratively acquiring images as the mechanism in motion. This research applies a 3D printing technology to prototype the mechanism components and employs servomotors for mechanism motions during the prototyping stage. Next, the mechanism guides the scanning motions to follow prescribed trajectories while capturing images of specified regions. Finally, the research embeds the firmware developed on a Linux OS platform into a high-speed controller board. The resolution tests verify that the best image resolution for the prototyped optical mechanism reaches 14.30 line pairs per millimeter, and the achievable image resolution for an inspected object is 35 μm. Through acquiring and synthesizing images simultaneously by the embedded firmware while the optical fiber-scanning mechanism is in motion, this research demonstrates that the developed system effectively constructs panoramic images for an endoscope device at a lower cost.

Application of dynamic adaptive technology based on symbolic regression to identify modal parameters of chip sorter

Cantilever structure, which needs high-frequency rotating motion, is widely used in the field of chip manufacturing. The motion stability of high-frequency rotation motion of cantilever structure directly affects the production efficiency. The traditional dynamic analysis method is no longer applicable to analyze the vibration of cantilever structure under high-frequency rotating motion. It is also urgent to control the high-frequency rotation motion of cantilever mechanism. In this paper, experiments are designed to collect strain signals of chip sorter’s cantilever under high-frequency operation, and modal parameters are extracted from time domain signals by symbolic regression algorithm. The results of modal parameter identification at high-frequency are selected as the samples, and the Gaussian process regression model of machine learning algorithm is used to train the samples. The prediction results can be used as the basis of structural stability research and vibration suppression.

Experimental Measurements on the Thermal Conductivity of Glycerol-Based Nanofluids with Different Thermal Contrasts

We report, in this work, our study of the thermal conductivity of high-viscosity nanofluids based on glycerol. Three nanofluids have been prepared with different thermal contrasts, by suspending graphene flakes, copper oxides, or silica nanoparticles in pure glycerol. The nanofluids were thermally characterized at room temperature with the 3ω technique, with low amplitudes of the temperature oscillations. A significant enhancement of the thermal conductivity is found in both the glycerol/copper oxide and the glycerol/graphene flake nanofluids. Our results question the role played by the Brownian motion in the microscopic mechanisms of the thermal conductivity of high-viscosity glycerol-based nanofluids. A similar behavior of the thermal conductivity as a function of the nanoparticle volume fraction was found for all three glycerol-based nanofluids presently investigated. These results could be explained on the basis of fractal aggregation in the nanofluids.

Multi-objective reliability-based optimal synthesis of path generating four-bar mechanisms: A cooperative game theoretic approach

In this study, a novel approach based on synergy of cooperative game theory, reliability-based design optimization (RBDO) and Monte Carlo simulation (MCS) is proposed to address the reliability-based multi-objective optimal synthesis of path generating four-bar mechanisms, taking into account the influence of dimensional uncertainty on the reliability of mechanism. Tracking error ([Formula: see text]), deviation of transmission angle from 90° ([Formula: see text]) and probability of failure of Grashof constraint are defined as three performance criteria whose minimization enhance the precision, quality of motion and reliability of mechanism, respectively. To do so, three objective functions are considered, namely, precision ([Formula: see text]), quality of motion ([Formula: see text]) and reliability ([Formula: see text]); each objective function is assigned to a player. To conduct the optimization procedure, a game model is proposed, in which the cooperative game scenario is employed by defining a Nash bargaining function to model the interaction between players. In this way, the three-objective optimum design of mechanism is cast into a single-objective optimization problem. The comparisons of the obtained results using the method of this research with those reported in the literature shows a significant improvement in reliability of mechanism, whilst both precision and quality of motion in deterministic design is maintained. Particularly, the tracking error and the deviation of transmission angle from 90° of the synthesized mechanism is 0.0006 and 666.36 respectively, whilst the reliability is guaranteed since no violation of Grashof constraint occurs in the presence of 10% parameter uncertainty.

Phase-chronometric diagnostic system for main drive of rolling mill

At present at the diagnostic of metallurgical equipment state, expert methods of evaluation are prevailed which have subject character. To solve the problem of information-metrological support of rolling mill stand effectively, a phase-chronometric method was proposed, elaborated in N.E. Bauman Moscow State Technical University. It was shown that increase of quality of measuring diagnostical information is provided by transfer from amplitude to chronometric scale and means of its realization at relative errors about 5×10‒4 % at the industrial frequency. At the phase-chronometric method, precision measuring of time intervals, correspondent to the phases intervals of the working cycle is used, depending on characteristic features of motion of a mechanism elements. In contrast to vibro-diagnostic method, by using the phase-chronometric method, the change of operation mode of rolling equipment can be defined hundred times quicker. Cyclicity of a mechanism motion and minimal scattering of measurement results at accomplishing working cycle enable to reveal stable in time diagnostic features and individual quantitative parameters values, which characterize technical state of a rolling mill. The proposed phase-chronometric system consists of an angle sensor of position (incremental encoder), system of information collection and defining of time intervals and personal computer with application software. The system of information collection and defining of time intervals is realized based on a plate, functionally uniting high-stability pulse generator, scale convertor, counter, measuring pulse generator and chrono-comparator. The embedded systems to realize the phase-chonometric metod are simple and reliable in operation. To realize the phase-chronometric method, a mathematical model was elaborated, comprising a system of differential equations, describing interaction of the package of interrelated multi-mass torsion systems. It was showed that verified mathematical model enabled quickly to reveal defects in a rolling mill operation.

The kinematics of curved profiles mating with a caged idle roller - higher-path curvature analysis

This investigation focuses on the relative motion of a force-closure higher pair mechanism, herein termed caged-roller joint and composed of a cylindrical roller meshing with two slot profiles, carved on different bodies. A distinctive feature of such a mechanism is the pure rolling velocity constraint imposed between its components to limit friction losses. This makes the caged-roller joint an ideal candidate to control the kinematics of high-speed operating devices, such as centrifugal pendulum vibration absorbers.In this paper, a theoretical framework for the motion of caged-roller joint is proposed, employing intrinsic geometry, higher-path curvature and envelope theory. For design-analysis purposes, the correlations between instantaneous invariants, slots profiles curvature properties and pure rolling conditions within the higher pairs have been established. Eventually, the obtained results have been verified for three particular curves profiles, to test their consistency and offer an immediate application.

Modelling and identification of the asymmetric hysteresis in the viscoelastic response of the fingertip under indentation: A multistate friction model with switching parameters

This paper presents a dynamic model for the identification of asymmetric hysteresis in the force response of the fingertip under cyclic local deformation of the fingertip soft tissues. Viscoelastic effects, marked anisotropy and nonlinearity contribute to the hysteretic behaviour of the force of the fingertip undergoing indentation. The fingertip force in response to an indentation stimulus varies along the loading and unloading cycles; the resulting hysteresis loops are asymmetric. The asymmetry arises from the simultaneous convexity of the branches of the hysteresis loop. The proposed model belongs to the class of multistate friction models that can effectively describe the hysteresis in the presliding regime of motion of general mechanisms with friction, by exploiting a mechanical analogy obtained through the concatenation of multiple elasto-plastic elements. The multistate model, which provides the mechanical representation of the fingertip response through a set of newly-conceived switching elements and viscoelastic blocks, can reproduce the convex and asymmetric hysteresis loops of the fingertip mechanical response, including the viscoelastic effects of stress relaxation and the influence of time interval between consecutive cycles of indentation.The model has been validated through the experimental identification of fingertip indentation tests performed on an optomechanical test-rig. This model potentially opens the way for efficient model-based control strategies of servomechanisms involved in tactile and haptic displays and interfaces.

β-MnO2 nanorods investigation of dielectric properties for electronic applications

In this study, β−MnO2 nanorods (NRs) were produced by hydrothermal method to describe the dielectric response of electronics and human health monitor applications. The structural properties of synthesized β−MnO2 NRs were identified using X-ray diffraction. Frequency variation of dielectric properties for β−MnO2 NRs was characterized by impedance spectroscopy technique. The frequency evolution of the dielectric properties for sample is associated with electrode polarization in the low frequency region. Transmission properties of β−MnO2 NRs were attributed to Kroop's theory, Maxwell-Wagner approach, viscoelastic mechanism and Brownian motion in the high frequency regime. The complex electric modulus based on Cole-Cole plots associated with equivalent RC circuit and their adapted to the Smith-Chart diagram is investigated for β−MnO2 NRs in detail. Absorption coefficient (α) and relaxation times (τ) values for the sample were recorded 0.21 and 5.1766 × 10−5 in succession. Frequency exponent (s), which is a characteristic of conductivity, was found to be compatible with the Correlated Barrier Hoping conductivity model for β−MnO2 NRs.

Geometric synthesis method of compliant mechanism based on similarity transformation of pole maps

Abstract. This paper presents a geometric synthesis method for compliant mechanisms based on similarity transformation of pole maps. Motion generation is a typical and common mechanism synthesis task, so this study takes it as the design requirement to expound the proposed method. Most of the current research work relies on numerical solution of the nonlinear Bernoulli–Euler beam model, numerical simulations or physical experiments to study the synthesis method of compliant mechanisms. There is a lack of simpler and more efficient methods to achieve motion generation of compliant mechanisms with various topologies. This study is based on pole map which is a geometric tool to describe the motion of rigid-body mechanisms. In this paper, we first demonstrate the feasibility of applying the similarity transformation of pole map to compliant mechanisms. It is proved that the pole map of compliant mechanisms has the same characteristic as rigid-body mechanisms during similarity transformation. Then we present the procedure of synthesis method in detail and expound the establishment method of function module which can avoid the functional defects of the final designed mechanism. At last, we take the compliant geared linkages and compliant four-bar linkage as examples to illustrate the novel synthesis approach. The result is an applicable and effective synthesis method for motion generation of compliant mechanisms.

Development of a control architecture for a parallel three-axis robotic arm mechanism using CANopen communication protocol

Based upon the CANopen communication protocol and the LabVIEW graphic programing procedures, this paper develops a closed-loop control architecture for a parallel three-axis (Delta) robotic arm mechanism. The accomplishments include prototyping a parallel three-axis robotic arm mechanism, assembling servomotors with associated encoders and gearsets, coding CANopen communication scripts for servomotor controllers and a host supervision GUI, coding forward/inverse kinematics scripts to compute the required servomotor rotations and the coordinates of a movable platform or the mechanism, coding tracking error compensation scripts for effective closed-loop griper control, and coding integration scripts to command and supervise the mechanism motion on the LabVIEW-based host GUI. During the development stage, this research designed and prototyped the parallel three-axis robotic arm mechanism based upon basic Delta robot kinematics. To control the mechanism effectively and accurately, this study implemented the CANopen communication protocol, which characterizes high speed and stable transmission. The protocol applies to the CANopen communication channels among the controllers and the host supervision GUI. On the LabVIEW development platform, the coded supervision GUI performs issuing/receiving messages to the CANopen-based controllers. The controllers excite the servomotors and actuate the parallel mechanism to track prescribed trajectories in a closed-loop control fashion. Meanwhile, an electromagnet attached to the movable platform of the robotic mechanism performs satisfactory picking/placing object actions.

SYNTHESIS OF HIGH-CLASS MECHANISMS OF VARIABLE STRUCTURE BASED ON DYNAMIC ANALYSIS

This paper presents the model of a high class variable structure mechanism. These mechanisms have not gained widespread acceptance in practice, despite obvious improvements in the ability to transmit motion and power. The article presents a synthesized high class mechanism. The block diagram of the formation of the mechanism is shown, the results of synthesis are presented. It is shown that with a relatively compact kinematic scheme, it is possible, with one drive, to create a system with several working links providing various technological operations, that is, on the basis of one mechanism, it becomes possible to create automatic mechanisms. In these studies, the development of a methodology for the dynamic design of the variable structure mechanism based on the analysis of dynamics and assessment of the influence of nonlinear factors on the quality of the machine as a whole was carried out. To study the motion of such variable structure mechanism, mathematical modeling of dynamics with discontinuous coefficients and nonlinear external forces is used.