Elastic Links Research Articles

Design and Performance Analysis of a Tea Impurity Eliminator

The present tea production technology is extensive and unsanitary as tea processing has the issues of easily mixing in hair, animal hair, and other debris problems. The production enterprises can only use a large number of workers to manually sort the tea, requiring large labor for low efficient and unideal sorting results. Hence, tea production enterprises urgently need to solve this problem to meet the product to meet the quality requirements of health food. In this paper, the design and development of the vibration motor of the key components in the tea impurity removal unit were studied. The specific work is as follows. The dynamic analysis of the movement of the material on the vibrating working surface is performed, the motion state of the tea declutter vibration machine is determined as throwing motion, and the structure scheme of the elastic link eccentric type vibration machine is designed. The structure scheme of the elastic link eccentric vibration motor was modeled by Inventor 3D design software, and the suitable parameters were selected for trial production of a prototype.

Local-to-non-local transition laws for stiffness-tuneable monoatomic chains preserving springs mass.

Recently, non-local configurations have been proposed by adding beyond nearest neighbour couplings among elements in lattices to obtain roton-like dispersion relations and phase and group velocities with opposite signs. Even though the introduction of non-local elastic links in metamaterials has unlocked unprecedented possibilities, literature models and prototypes seem neither to provide criteria to compare local and non-local lattices nor to discuss any related rules governing the transition between the two configurations. A physically reasonable principle that monoatomic one-dimensional chains must obey to pass from single- to multi-connected systems is here proposed through a mass conservation law for elastic springs thereby introducing a suitable real dimensionless parameter [Formula: see text] to tune stiffness distribution. Therefore, the dispersion relations as a function of [Formula: see text] and of the degree of non-locality [Formula: see text] are derived analytically, demonstrating that the proposed principle can be rather interpreted as a general mechanical consistency condition to preserve proper dynamics, involving the spring-to-bead mass ratio. Finally, after discussing qualitative results and deriving some useful inequalities, numerical simulations and two-dimensional FFTs are performed for some paradigmatic examples to highlight key dynamics features exhibited by chains with finite length as the parameters [Formula: see text] and [Formula: see text] vary.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'.

Analysis of the periodicity of movements of mechanisms with elastic links of variable length

Abstract Elastic dynamic systems with open kinematic chains are effectively described by a recursive model of the generalized Newton–Euler method with the provision of computational algorithms with a degree of complexity proportional to the dimension of these systems, i.e. O(n). Such systems, in particular, are elastic manipulators, some of which are discussed in this article. In the case when elastic dynamical systems have closed kinematic circuits, the application of a numerical analysis strategy without reversing the mass matrix is extremely difficult. The analysis of the simplest type of elastic mechanisms with closed circuits, such as a crank–slide mechanism and a four–pin mechanism with elastic connecting rods, revealed a peculiar picture of the periodicity of the functions of elastic movements of connecting rods, which differs significantly from the periods of operation of the mechanisms themselves. In this article, the properties of the periodicity (or pseudo-periodicity) of the elastic displacement function of mechanisms with elastic links of variable length are investigated using examples of numerical dynamic analysis of crank–rocker mechanisms.

ПОЗИЦИОНИРОВАНИЯ РАБОЧЕГО ОРГАНА МАНИПУЛЯЦИОННОЙ РЕАБИЛИТАЦИОННОЙ СИСТЕМЫ ПРИ НАЛИЧИИ ТРЕМОРА КУЛЬТИ ЧЕЛОВЕКА

The problem of accurate positioning of objects using an active prosthesis hand is not widely investigated, where many factors can play a significant role in degrading of the prosthesis accuracy. An unorthodox rehabilitation system equipped with manipulator with elastic links aimed to help people without brushes in performing fine tool movements has been developed. In this system, a force/torque sensor is securing a physical hard connection between the stump and the prosthesis. In such human-prosthesis systems many factors contribute to tool positioning error, but when high accuracy is required, the human tremor in the residual stump becomes a key factor affecting the accuracy of the tool fine movements. Mathematical model of this system is developed and the error resulted by stump tremor is isolated. Depending of the force/torque sensor, two control strategies are presented in order to perform high accuracy working organ movement between two points. The first is to use the sensor to collect involuntary stump movements caused by the tremor. The second is to use the sensor as an input for the control system by recording all stump movements. In computer simulation, the effect of three main types of human tremor on the manipulation accuracy of the rehabilitation system is observed. As a result, a positioning accuracy of 0.1 mm is achievable by meeting some design criteria that would element the resonance effect in the system

Origami-inspire quasi-zero stiffness structure for flexible low-frequency vibration isolation

As an emerging technology, origami exhibits rich nonlinear static and dynamic properties. However, simulating creases remains a key challenge hindering practice application, especially for volumetric (deformable) origami. Inspired by the bistable behavior and axial-rotational coupling mechanism of triangulated cylindrical origami (TCO), this paper proposes a novel combined truss-spring structure with additional inertial mechanism (TCTS-RIM) for low-frequency vibration isolation. Unlike pure TCO, the TCTS-RIM uses elastic linkages to simulate all creases and modifies crease positions, enhancing physical realization in engineering applications and offering tunable stiffness and inertia on demand. Static analysis shows the modified truss-spring structure in TCTS-RIM has superior quasi-linear negative stiffness compared to pure TCO, which enables a very wide quasi-zero stiffness (QZS) range via linear spring compensation. The wide QZS range for different loads can be realized by setting appropriate structural parameters. From system dynamic equations, nonlinear inertia, nonlinear quadratic force, and nonlinear damping due to RIM are identified and discussed. The Alternating frequency–time harmonic balance method is used to obtain the displacement transmissibility, and its parametric influencing investigations verify that the proposed TCTS-RIM has excellent low-frequency vibration isolation performance and rich tunability. Comparative discussions show the wide QZS range significantly reduces the resonance frequency, broadens the isolation frequency band, and yields superior dynamic performance versus pure TCO isolators. Moreover, equivalent mass, anti-resonance and softening behavior induced by the rotational inertia mechanism further enhance low-frequency vibration isolation performance. An experimental prototype is built, and experimental results validate the correctness of the theoretical analyses. This work presents a simple mechanical implementation of volumetric origami, which may progress the engineering applications of origami and provide a viable approach to low-frequency vibration control.

СРАВНЕНИЕ ТЯГОВЫХ ПРИВОДОВ С ОПОРНО-ОСЕВЫМ И ОПОРНО-РАМНЫМ ПОДВЕШИВАНИЕМ ДВИГАТЕЛЯ

The problem of finding criteria for choosing between axial support and frame support drives for locomotives in the conditions of import substitution is considered. The changes in the criteria for choosing a traction drive design depending on the changes in requirements for locomotives are analyzed. The types of drives are compared according to their technological simplicity, weight and size indicators, the effect on the coupling properties of the locomotive and the damage to the track structure, taking into account the production of new traction drive designs of an integrated type with collector-free traction electric motors having an increased rotation frequency. It was found that for locomotives with collector traction motors, it is advisable to use a frame support drive with an axial gearbox or a hollow driveshaft, and when using collector-free traction motors , the axial support traction drive of an integrated layout on freight locomotives with 1250 mm wheel diameter to improve coupling properties by 12...15%, it is advisable to replace it with the one proposed by the authors, which is an aggregate-type drive with an elastic link in the shaft lines, or with frame support drives with an axial gearbox, and with a wheel diameter of 1050 mm – frame support drives with a hollow shaft on the axis. An application for a patent has been submitted for the proposed solutions.

ON THE SUPPRESSION OF VIBRATIONS IN ELASTIC LINKS OF A THREEMASS ELECTRIC DRIVE SYSTEM

The main reason for failures of technological mechanisms is associated with the failure of elements of the electric drive system. One of the main reasons for the malfunction of electric drive elements is the presence of vibrations in the elastic links of the mechanical part of the electric drive. Such phenomena mainly occur during transient processes of starting and stopping an electric drive, as well as under the influence of a load that is variable in nature. From the above, it is obvious that suppression of vibrations in the elastic links of the mechanical part is of practical interest. The most promising studies aimed at studying and suppressing vibrations in the elastic links of a three-mass electric drive system are analyzed. A comparative analysis of these studies shows that they consider the operating features of individual specific electric drive systems, which cannot provide a complete understanding of a comprehensive solution to the problem of ensuring the suppression of vibrations, arising in the mechanical part for various reasons. That is why it is necessary to evaluate the possibilities of suppressing elastic vibrations of the electric drive system, taking into account all its links. The goal of this work is to propose an approach for suppressing vibrations in the elastic links of a three-mass electric drive system. The change in the elastic moment under various characteristics of the load created by the mechanism is considered, in particular, in cases of constant moment, exponential and step laws of change. The capabilities of proportional-integral (PI) and proportional-integral-derivative (PID) controllers for suppressing oscillations are analyzed. It is substantiated that although the system stabilizes with a PID controller in a short time, it does not provide the expected result and therefore it is recommended to use a controller with a fuzzy logic due to its simple control and rather high efficiency. The results obtained can be successfully used to improve the reliability of a three-mass electric drive system.

ОСОБЛИВОСТІ ЗБУДЖЕННЯ ДИНАМІЧНИХ ПРОЦЕСІВ У ГРУПОВИХ ЕЛЕКТРОПРИВОДАХ ОБТИСКНИХ СТАНІВ

In the paper, a study of the influence of variable technological loads on the main line of the rolling mill is carried out. A mathematical model of the study of dynamic processes in group electric drives of crimping technological machine units (rolling mills) is presented. It is shown that the dependence of the moment of technological resistance on the speeds of the working rolls is determined by the dependence that takes into account the peculiarities of the technological load. The study of the influence of variable technological loads on the main line of the rolling mill showed that the drop in the coefficient of friction on the upper shaft is the most dangerous. It was found out that in these cases, there can be a significant mismatch of the speeds of the working rolls, and the drop in the moment of technological resistance on the upper roll is not compensated by the increase in the moment of technological resistance on the lower roll; therefore, self-oscillations are excited in the elastic links of the main line of the rolling mill, as well as unstable modes of oscillations. Keywords: dynamic model, group machine unit, crimping mill, rolling mill.

Anti-deadzone adaptive fuzzy dynamic surface control for planar space robot with elastic base and flexible links

In order to combat the impact of the dead zone and reduce vibration of the space robot's elastic base and flexible links, the trajectory tracking and vibration suppression of a multi-flexible-link free-floating space robot system are addressed. First, the elastic connection between the base and the link is considered as a linear spring. Then the assumed mode approach is used to derive the dynamic model of the flexible system. Secondly, a slow subsystem characterizing the rigid motion and a fast subsystem relating to vibration of the elastic base and multiple flexible links are generated utilizing two-time scale hypotheses of singular perturbation. For the slow subsystem with a dead zone in joint input torque, a dynamic surface control method with adaptive fuzzy approximator is designed. Dynamic surface control scheme is adopted to avoid calculation expansion and to simplify calculation. The fuzzy logic function is applied to approximate uncertain terms of the dynamic equation including the dead zone errors. For the fast subsystem, an optimal linear quadratic regulator controller is used to suppress the vibration of the multiple flexible links and elastic base, ensuring the stability and tracking accuracy of the system. Lastly, the simulation results verify the effectiveness of the proposed control strategy.

The dynamic analysis of fixed deep-water platform

The industrial progress is closely related with active using of hydrocarbons more than half of reserves of which lie in rock formations beneath seabed or ocean floor. For oil production at the great depth of immersion oil production fixed platforms are used most often. But using of such technological structures is not limited only to interest of oil and natural gas industry whereas they are important for navigation and military purposes. Offshore fixed platforms are exposed to effects of a high seismicity, wind, waves, strong undercurrents and an impulse impact during the movement of ice fields especially when exploitation in northern seas. The impact of different factors on the value of the period of natural oscillations ofthe offshore fixed deep-water ice-resistant platform with the depth of immersion 120 m that rests on the pile foundation was researched. Two discrete idealized models of the platform were used for the analysis: the first model that was implemented without taking into account the flexibility of the foundation and the second model where the flexibility of the pile foundation and the action of ground foundation were taking into account by the addition of elastic links that simulate the elastic connection between joints. Also, impacts of the connected mass of water media that was modeled in the form of additional distributed joints mass and the impact of the ice field that was modeled by the addition of additional links were investigated. The analysis showsthat values of periods of natural oscillations form increase by 8-20% when the flexibility of the pile foundation was taken into account; increase by 9-100% when the impact of the connected mass of water media was taken into account; decrease by 9-100% when the impact of the ice field and water media were taken into accountthat is significant when analyzing of stress-strain state of members of the structure.

Optimal mode movement of the robot manipulator on an elastic base according to the criterion of the mean square value of the acceleration of the drive torque

Previous studies of the optimization of the manipulator motion mode on an elastic base based on the criteria of the rms value of the drive torque and the rate of change of the rms value of the drive torque established that the use of optimal manipulator motion modes, which are created on the basis of higher derivatives of the characteristics of the change of the drive torque, allow to obtain more smooth movements of the boom system of the manipulator, thereby reducing its oscillations on the elastic support. At the same time, the obtained optimal modes of movement didn't completely eliminate the boom system oscillations during the change of departure. By observing the oscillations of the elastic link of the manipulator, the quality of the obtained optimal modes of movement was evaluate and the presence of residual oscillations was shown.
 This work considers the possibility of optimizing the manipulator's motion mode based on the criterion of the mean square value of the acceleration of the drive torque change. For this purpose, the second derivative of the driving torque function of the manipulator boom system drive was determined first. Such a criterion for optimizing the motion mode is an integral functional, the minimization of which is carry out by the methods of variational calculus. The regularity of the change of the driving torque it was find from the dynamic equation of motion.
 The search for the optimal motion mode of the manipulator realized through the solution of the Poisson boundary nonlinear differential equation of the fourth order.
 The results of the conducted research made it possible to clarify much better the nature of the vibrations of the manipulator boom system and, as a result, to develop a drive control system that allows the realization of the obtained optimal mode of movement.

Prospects for the use of a vibratory jaw crusher with an inclined crushing chamber for processing of brittle materials

Obtaining a powder product from brittle materials is associated with significant difficulties: an insufficient number of production capacities as well as with their low efficiency. This indicates relevance and need for research aimed at creating new designs and technological schemes. Glass containers were selected for research from among all types of glass waste. Presented are a structural diagram and description of a horizontal pendulum impact tester, on which studies were carried out on destruction of a bottle by impact load. The impact tester gives an opportunity to determine impact energy, impact speed, acceleration, movement of the impactor. An analysis of the above figures shows that one blow is enough to destroy a bottle. Rational mode is when impact load is distributed along the length of the bottle. This mode can be implemented in a vibratory jaw crusher with an inclined crushing chamber, which includes the following main elements: a passive jaw located on shock absorbers, an active jaw pivotally mounted in the body and connected to it by means of elastic links, a two-shaft inertial vibration exciter. The presented granulometric characteristic of the crushed bottle shows a high efficiency of using a vibratory jaw crusher. The yield of the product sized less than 5.5 mm was 95%, and that sized less than 100 microns - 16%. The crusher has enough parameters to adjust particle size distribution over a wide range.

Asymptotic solutions for large fractures growing parallel to a free plane

Straight 2D and disc-like cracks situated close to a parallel free plane are considered and asymptotic solutions for the stress intensity factors (SIFs) and crack opening are developed. Two asymptotic terms with respect to the small ratio of distance from the surface to the crack length/radius are derived. The derivation is based on considering the material between the crack and the free surface as an elastically supported beam or circular plate. The crack is considered to be opened either by uniform tensile stress or a pair of concentrated forces or moments representing the action of central defects (these represent for instance the crack growth from initial inclined crack or pore under compression acting parallel to the free surface). A crack with non-interacting surfaces (the conventional crack) and a crack with linear links between the surfaces are considered. Interaction with the free surface is shown to considerably increase the crack opening and SIFs, while the presence of the elastic links can reduce these crack parameters. In particular, the opening and SIFs of a crack with linear links under a pair of concentrated forces/moments exponentially vanish with the crack dimensions tending to infinity. The obtained asymptotic solutions provide a simple and accurate tool for investigating mechanisms of surface delamination and spallation (including thermal spallation and strain rockbursts).

Miniature Parallel Continuum Robot Made of Glass: Analysis, Design, and Proof-of-Concept

Parallel continuum robots (PCRs) are flexible manipulators, whose configuration is determined by the controlled deformation of their parallel-arranged elastic links. They are of great interest for micromanipulation applications due to their intrinsic compliance, their extrinsic actuation, and their miniaturization potential. This article presents the design and prototype of a miniature 3-DoF glass PCR, capable of reaching large tip-tilt angles in a tiny volume. The flexible structure is composed of three legs made of glass, each one having an extension range from 6 to 15 mm and a diameter of 125 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m. The workspace of the robot, its stiffness, and manipulability are evaluated with respect to varying geometrical proportions of the platform size with respect to the base diameter. Experimental validation shows that the platform is able to reach tip–tilt angles from -84 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> to 117 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> in a space of 15 mm wide and 10 mm high and to follow conveniently desired paths within its workspace.

Coherent movement of error-prone individuals through mechanical coupling

We investigate how reliable movement can emerge in aggregates of highly error-prone individuals. The individuals—robotic modules—move stochastically using vibration motors. By coupling them via elastic links, soft-bodied aggregates can be created. We present distributed algorithms that enable the aggregates to move and deform reliably. The concept and algorithms are validated through formal analysis of the elastic couplings and experiments with aggregates comprising up to 49 physical modules—among the biggest soft-bodied aggregates to date made of autonomous modules. The experiments show that aggregates with elastic couplings can shrink and stretch their bodies, move with a precision that increases with the number of modules, and outperform aggregates with no, or rigid, couplings. Our findings demonstrate that mechanical couplings can play a vital role in reaching coherent motion among individuals with exceedingly limited and error-prone abilities, and may pave the way for low-power, stretchable robots for high-resolution monitoring and manipulation.

Algorithm for simulation of vibration effects during track tests of aircraft and missile technology

Track high-speed ground tests of products of aviation and rocket technology make it possible to experimentally confirm the aerodynamic and strength characteristics of new aircraft or their components. Experimental installation Rocket rail track 3500, located on the territory of the Federal State Enterprise Scientific Test Range of Aviation Systems named after L. K. Safronov (FKP GkNIPAS named after L.K. Safronov), is a complex hydro-gas-dynamic engineering structure. The main part of this installation is a rail track placed on a special concrete base, which is based on piles to eliminate the influence of viscoelastic ground vibrations. Between the rails, taking into account the profile of the track, a hydrodynamic multi-level tray is made, designed for hydraulic braking of the stored track sled. The movable rocket track sled rests on slip shoes covering the top rail head. On the track sleigh, solid propellant rocket engines and the object of study are placed. The article describes the approach to the calculation of determining the dynamic loads acting on the elastic structure of the track sled with the test object. The design is represented by a schematic spatial model of elastic beams in the form of rods, plates, pipes with equivalent mass and stiffness, interconnected by elastic links. A model of non-stationary aerodynamic forces is formulated taking into account viscosity for numerical calculations of the flow around the sled structure. Programs have been developed and modeling of the aerodynamic interaction in the case of a supersonic air flow around the structure of a rocket sled has been carried out. The results of vibrational accelerations of elements, components of the sled and the test object, depending on the speed of movement, were obtained by calculation. The forms and frequencies of natural free vibrations of the sled structure are determined, and the densities of the vibration acceleration spectra are calculated.

Increasing the Technical Resource of the 152 MM Caliber Howitzer, 1981 Model by Improving the Constructive Solution of a Subassembly of the Elastic Linkage Composition

Abstract The method of increasing the technical resource of the 152 mm caliber howitzer, model 1981 aims to improve the construction solution of an essential subassembly of this product’s structure, without affecting the functioning of the howitzer and without diminishing its safety and stability in firing. For this reason, the article aims to highlight the essential aspects of the construction of the guiding and sealing piston of the 152 mm caliber, 1981 model howitzer’s recuperator, using a polymer composite material and to present how the chosen technical solution influences the technical resource of the product.

A study on the flexible Bricard mechanisms with plane-symmetric structure

The six-bar single-loop overconstrained Bricard linkages have been attracting continuous attention due to their special geometry and remarkable mobility. During the past century, a great number of papers have been published in various aspects, however, almost all of them focus on those only consisting of rigid links and joints. In this paper, the concept of ‘Flexible Bricard Mechanisms’ is introduced to extend these classical overconstrained linkages from the category of rigid-body systems to the scope of flexible ones. In these novel designs, slender elastic beams are used to replace the rigid links and joints, such that the mobility of flexible Bricard mechanisms is achieved not only via the relative motion from rigid joints, but also the large-scale deformations of elastic links. The plane-symmetric case is studied to demonstrate the realization, analysis methodology, and potential applications of this new type of Bricard mechanism. A candidate with a specialized structure is elaborated as a case study, about which a proof-of-concept prototype is developed. Preliminary experiments are conducted to verify the feasibility of the proposed idea.

Числове моделювання поступальних і обертальних коливань рдтп у стапелі під час вогневих стендових випробувань

This article dwells on results of firing bench testing of the solid-propellant rocket engine (SPRE), fastened to the thrust-measuring assembly stand. It is shown that when engine enters the steady-state mode of operation, plane (forward and rotation) vibrations of the SPRE can take place in the assembly stand due to the sudden pattern of thrust generation and displacement of the center of mass of the vibrating system from the engine axis. These vibrations distort measured values of engine thrust and pattern of its change versus time. The purpose of this work is to simulate the oscillating processes of the engine atop the assembly stand to single out in the distorted values of the measured thrust the components related to the processes in the engine and components, which are introduced into the thrust measurement by the oscillating processes in the system “assembly stand – engine”. Model of vibrating system is suggested, which consists of two rigidly connected bodies, containing elastic links, enabling forward and rotary motion and limited by the rigidity of the links. Mathematical model of the vibrating system is developed. Internal forces and moments acting in oscillatory system are defined. Method of numerical simulation of plane vibrations within the limits of the developed model is suggested. Plane vibrating motion and elastic force curve (curve based on force sensor readings) were simulated in thrust-measuring system for different cases of thrust curve and values of vibrating system parameters. Resonance condition was simulated and mutual influence of elastic parametrical link between forward and rotary vibrations was established. Impact of thrust-measuring system rigidity on peak values of force sensor readings was found out. Elastic force vibrations in thrust-measuring system with vibrating system parameters were simulated including variant of thrust change versus time, implemented during firing bench tests of one of the SPRE. It is shown that registered simulation results recreate thrust measurement results in pattern and values obtained by the force sensor during the firing bench tests, and owing to this, it was concluded that oscillating process parameters, assumed in the model, meet the actual ones. It is concluded that simulation provides objective interpretation of the thrust curve, reliable and comprehensive analysis of engine run during firing bench tests, more detailed and exact design of the assembly stand. Key words: vibrating system, plane vibrations, forward vibrations, rotary vibrations, resonance, thrust measurement.

Finite Element Model of Kinematic Pair Clearances of Elastic Linkage Mechanisms

The elastic deformation of the links in robot mechanisms affects the precision of their motion and fatigue strength. Kineto-elastodynamics (KED)-the dynamics analysis of mechanisms that considers the elasticity of their links-emerged early in studies of mechanisms and has been the subject of extensive research and applications since. However, there have been no reports on the effects of kinematic pair clearances on the elastic vibration of mechanisms. This is mainly because no finite element (FE) model has been developed for describing kinematic pair clearances in KED research of elastic linkage mechanisms. In this study, an FE model was proposed for describing kinematic pair clearances. The mass matrix of the model was obtained by considering the lumped masses of the pin and bearing. The stiffness matrix of the model was obtained based on the moduli of elasticity of the pin-bearing pair. The model was applied to KED modeling and was verified through simulation and complementary experiments. The results show that the model is suitable for KED research of elastic linkage mechanisms with small kinematic pair clearances but not suitable for those with large kinematic clearances. Our FE model of kinematic pair clearances may be useful for investigating the vibration of elastic-body robot mechanisms.