Elastic Links Research Articles

Introducing Series Elastic Links for Affordable Torque-Controlled Robots

Robotics has the potential to become a revolutionary technology in the next future and if we want to spread it among the population we must start accounting for affordability in robot research and design. Plastic robots are an emerging example of affordable design where expensive metal structures are replaced by low-cost plastic materials. Plastic materials are not only cost effective but, thanks to their inherent compliance and lightweight, lead to significant advantages in terms of safety and force controllability. Inspired by the idea of series elastic actuator (SEA) this letter introduces the new concept of series elastic link (SEL), which exploits the inherent flexibility of plastic links to implement series compliance. This letter elaborates on the concept of SEL and highlights a parallelism with SEAs. Then, focusing on a single-DOF setup it shows that, beyond their economic advantage, SELs lead to enhanced safety and more accurate force control with respect to traditional SEA implementations. The proposed argumentations are theoretically supported and experimentally validated.

Конструкция плиты для сборных дорожных покрытий

Experience in the operation of prefabricated concrete pavements with intensive traffic of heavy vehicles has shown that despite a high strength of the concrete slabs themselves it is necessary to arrange strong foundations. While laying concrete on the ground residual deformations are accumulating in it due to pressures which are initiated by elastically bending plates when vehicles are passing that leads to formation of voids under the plate and cracks in the plate itself. In order to increase rigidity of the plate (reduction of its settlement during the passage of vehicles) the author has proposed to arrange plates with two longitudinal ribs, and the plates themselves are to be laid on loose soil mixed with cement. The ribs are proposed to be placed on roll bars, i. e. symmetrically with respect to a longitudinal axis of the plate at a distance from each other which is equal to the distance between wheels of the calculated vehicle on one axis. In order to determine dependence of plate rigidity on a shape and a size of a cross section in longitudinal ribs calculations have been made while using a PC “Lira” and a finite element method. A finite element model of the plate has included 19152 nodes and 18943 finite elements. An elastic foundation has been modeled by vertical elastic links which are in every bottom node. The plate has been loaded with a load which is equivalent to the load from a calculated vehicle wheel at four points: a wheel in the middle of the plate; a wheel on the corner of the plate; two wheels at the same time on the line which is perpendicular to the longitudinal axis of the plate and located at the beginning (or end) of the plate; two wheels at the same time on the line which is perpendicular to the longitudinal axis of the plate and passing through its center. The following forms of a longitudinal rib having the same crosssectional area have been studied at the beginning: triangular, oval (semicircle) and rectangular. In the context of plate rigidity increase the most optimal form has been a triangular shape. Height differences in such a plate are the least in case of load action. So, for example, in comparison with a typical plate (plate without longitudinal ribs), presence of longitudinal ribs of triangular cross – section increases plate rigidity by an average of 50 % depending on the location of the calculated wheel on the plate (39–64 %). After determining an optimal shape of cross section for longitudinal ribs the dependence has been found for plate rigidity and it depends on a height of longitudinal triangular ribs. While having a constant volume of the plate and a constant a size of the rib base (32 cm) (approximate width of a calculated vehicle wheel) a rib height and a plate thickness have been changed. The calculations have made it possible to determine dependence of the plate rigidity on a height of a longitudinal rib. It has been determined that as for the given volume and dimensions of the plate the optimal rib height is 25 cm.

Soap film spanning electrically repulsive elastic protein links

Soap film spanning electrically repulsive elastic protein links

Use of mechanical models for the analysis of antivibration mounting

The paper considers a two-stage vibration isolation of rotary machines including rotor-frame elastic linkage. It proposes internal elastically inertial vibration protection inbuilt between a rotor and a frame. The method of dynamic compliance is used to define forces influencing the frame. The proposed vibration motor can be used for rotary actuators of compact devices. The main objective of the study is to increase the motor torque and durability.

Design and dynamic problems of traction drive of electric locomotive 2ES10 and proposals on its modernization

The analysis of design and dynamic features of the traction drive of the freight electric locomotive 2ES10 is carried out. The study found that the main disadvantages of the drive are the complexity of manufacturing and the lack of elastic links, damping perturbations from the path. A new drive scheme with dynamic load damping is proposed and patented.

Multisoliton Dynamics in the Sine-Gordon Model with Two Point Impurities

Collective variables method is used to derive a set of differential equations to describe the dynamics of a kink in the sine-Gordon model with two identical point impurities taking damping into account. It is shown that the scenarios of kink interaction with the waves localized on the impurities, found from the reduced model, are similar to those obtained earlier by numerical integration of the continuous sine-Gordon equation. For the case of the kink passage through the region with the impurities, the structure and properties of the arising on impurities long-lived four-kink multisolitons are analyzed. For the approximate analytical description of the two bound impurity-localized nonlinear waves, the system of differential equations for harmonic oscillators with elastic link is obtained. The analytical model qualitatively reproduces the results of the sine-Gordon equation numerical simulation. The cases of large and small distances between impurities are analyzed. The results of our study uncover new features of the kink-impurity interaction which is important for a number of applications where the sine-Gordon model is used.

Space dependent adhesion forces mediated by transient elastic linkages: New convergence and global existence results

In the first part of this work we show the convergence with respect to an asymptotic parameter ε of a delayed heat equation. It represents a mathematical extension of works considered previously by the authors [14–16]. Namely, this is the first result involving delay operators approximating protein linkages coupled with a spatial elliptic second order operator. For the sake of simplicity we choose the Laplace operator, although more general results could be derived. The main arguments are (i) new energy estimates and (ii) a stability result extended from the previous work to this more involved context. They allow to prove convergence of the delay operator to a friction term together with the Laplace operator in the same asymptotic regime considered without the space dependence in [14]. In a second part we extend fixed-point results for the fully non-linear model introduced in [16] and prove global existence in time. This shows that the blow-up scenario observed previously does not occur. Since the latter result was interpreted as a rupture of adhesion forces, we discuss the possibility of bond breaking both from the analytic and numerical point of view.

Modelling and Analysis of Characteristics of a Piezoelectric-Actuated Micro-/Nano Compliant Platform Using Bond Graph Approach.

The piezoelectric-actuated flexure-based compliant platform is commonly adopted in many fields of micro and nanotechnology. In this paper, bond graph modeling, and kinematic and dynamic characteristics of a piezoelectric-actuated micro-/nano compliant platform system are investigated. During modeling, the bond graph model of the piezoelectric actuator (PZT) is derived by considering both the electrical domain and the mechanical domain. Considering the compliances of flexure hinges and elastic linkages, as well as the input ends, the bond graph model for the bridge-type displacement amplification mechanism in the compliant platform is established by combining pseudo-rigid-body (PRB) model theory and elastic beam theory. Based on the interactions between the PZT subsystem and compliant platform subsystem, the kinematic performance of the proposed compliant platform system is evaluated through both computer simulations and experimental tests. Furthermore, the frequency responses, dynamic responses and load capacity of the compliant platform system are studied. This paper explores a new modeling method for a piezoelectric-actuated compliant platform system, which can provide an effective solution when analyzing the micro-/nano system.

Network blocking probability-based evaluation of proposed spectrum assignment strategy for a designed elastic optical network link

Elastic optical networks (EONs), which are spectrum-efficient new generation optical networks, have been replacing traditional dense wavelength division multiplexing-based networks in backbone networks. The allocation of spectral resources while overcoming spectrum contiguity and continuity constraints is a challenging task in EONs. This paper presents a RSA simulation framework for a designed EON link, and the performance of existing spectrum assignment (SA) strategies (first fit, random fit and last fit) has been evaluated. This paper further presents a SA strategy based upon the relative difference between available spectrum slots width and the required slot width for an incoming traffic demand. The performance of proposed SA technique has been evaluated by carrying out simulations using the designed RSA simulation framework under different network load conditions. The comparative analysis with existing SA strategies shows that the proposed strategy is successful in reducing network blocking probability effectively.

Compositive Optimal Control for the Seismic Response of a Long-Span Triple-Tower Suspension Bridge

In the design of super-long-span suspension bridges, the floating system is commonly adopted. However, this system may lead to the excessive earthquake-excited longitudinal displacement (LD) at the end of the main girder, which in return could result in pounding damage at expansion joints. In this paper, Taizhou Bridge, the triple-tower suspension bridge with the longest main span in the world, is taken as an example to demonstrate the effectiveness of three different approaches (elastic links, viscous dampers, and their combination) of mitigating the possible excessive LD. The finite element code ABAQUS is used to build the numerical model of the bridge and calculate the dynamic characteristics as well as the seismic responses. Then, 24 cases with different parameters of elastic links and viscous dampers are investigated and it is observed that the mitigation effect of the 24 cases varies significantly with different parameters. To obtain the optimized mitigation effect for seismic responses, including the LD of the girder, the LD and shear force of all towers, in the 24 cases, the modified analytic hierarchy process (AHP) method is introduced to realize the compositive optimal control of the triple-tower suspension bridge. Results show that the 24th case is the optimal one in which the LD of the girder is reduced significantly while the inner force of towers does not get excessive increase.

Eigenvalue and eigenmode synthesis in elastically coupled subsystems

A method to synthesize the modal characteristics of a system from the modal characteristics of its subsystems is proposed. The interest is focused on those systems with elastic links between the parts which is the main feature of the proposed method. An algebraic proof is provided for the case of arbitrary number of connections. The solution is a system of equations with a reduced number of degrees of freedom that correspond to the number of elastic links between the subsystems. In addition the method is also interpreted from a physical point of view (equilibrium of the interaction forces). An application to plates linked by means of springs shows how the global eigenfrequencies and eigenmodes are properly computed by means of the subsystems eigenfrequencies and eigenmodes.

Four-dimensional analysis by high-speed holographic imaging reveals a chiral memory of sperm flagella.

Here high-speed Digital Holographic Microscopy (DHM) records sperm flagellar waveforms and swimming paths in 4 dimensions (X, Z, and t). We find flagellar excursions into the Z-plane nearly as large as the envelope of the flagellar waveform projected onto the XY-plane. These Z-plane excursions travel as waves down the flagellum each beat cycle. DHM also tracks the heads of free-swimming sperm and the dynamics and chirality of rolling of sperm around their long axis. We find that mouse sperm roll CW at the maximum positive Z-plane excursion of the head, then roll CCW at the subsequent maximum negative Z-plane excursion. This alternating chirality of rolling indicates sperm have a chiral memory. Procrustes alignments of path trajectories for sequences of roll-counterroll cycles show that path chirality is always CW for the cells analyzed in this study. Human and bull sperm lack distinguishable left and right surfaces, but DHM still indicates coordination of Z-plane excursions and rolling events. We propose that sperm have a chiral memory that resides in a hypothetical elastic linkage within the flagellar machinery, which stores some of the torque required for a CW or CCW roll to reuse in the following counter-roll. Separate mechanisms control path chirality.

Pinching in Steel Rack Joints: Numerical Modelling and Effects on Structural Response

The structural behaviour of beam-to-column joints plays a key role in the seismic response of frame structures. Regarding to steel storage pallet racks, experimental tests have highlighted that the hysteresis loop of their joints is characterized by the pinching, with the consequence of a reduction of the dissipated hysteretic energy and load carrying capacity. In this paper the authors propose a simplified numerical pinching model capable to simulate the mechanical response of beam-to-column joints under cyclic loads. To develop and check this model, several comparisons are performed with both literature data and experimental results of laboratory tests. The proposed model is characterised by three links placed in parallel: two “composed links” describe the non-linear bending moment-rotation curve of the joint, and a linear elastic link transfers the axial and shear force from the beam to the column. The model is appropriate for predicting the down-aisle seismic response of rack systems and it can be easily implemented in commercial software packages, commonly used for non-linear seismic vulnerability analyses. Moreover, features of the model can be estimated from a few structural data and it does not require to perform expensive cyclic experimental tests. For a deeper understanding of the effects of pinching in the seismic response and to highlight the potentiality of the proposed model a case-study example is also considered. The case-study concerns a rack system, whose beam-to-column joints are modelled using two numerical approaches which differ in the deterioration of the rotational stiffness of joints. Non-linear dynamic analyses, with simulated ground acceleration time-histories, have been carried.

Deep learning approaches for mining structure-property linkages in high contrast composites from simulation datasets

Data-driven methods are emerging as an important toolset in the studies of multiscale, multiphysics, materials phenomena. More specifically, data mining and machine learning methods offer an efficient toolset for extracting and curating the important correlations controlling these multiscale materials phenomena in high-value reduced-order forms called process-structure-property (PSP) linkages. Traditional machine learning methods usually depend on intensive feature engineering, and have enjoyed some success in establishing the desired PSP linkages. In contrast, deep learning approaches provide a feature-engineering-free framework with high learning capability. In this work, a deep learning approach is designed and implemented to model an elastic homogenization structure-property linkage in a high contrast composite material system. More specifically, the proposed deep learning model is employed to capture the nonlinear mapping between the three-dimensional material microstructure and its macroscale (effective) stiffness. It is demonstrated that this end-to-end framework can predict the effective stiffness of high contrast elastic composites with a wide of range of microstructures, while exhibiting high accuracy and low computational cost for new evaluations.

A Problem of Axisymmetric Torsion of a Multilayer Plate with Elastic Links between the Layers

By using the method of compliance functions and the Hankel transformation of the first order, we propose a procedure for the solution of the problem of torsion of a multilayer plate with elastic links between the layers. Two auxiliary functions connected with the transforms of stresses and displacements at the points of the top boundary of the layer are introduced for each layer. The recurrence relations for the auxiliary functions and the compliance functions of neighboring layers of the plate are constructed. For a two-layer plate, we analyze the influence of the coefficients of elastic links and the geometric and mechanical parameters of layers on the distribution of stresses at points of the common boundary of the layers.

Symbolic linearization and vibration analysis of constrained multibody systems

A computer algebraic approach for linearization of the equations of constrained multibody systems is discussed in this paper. Based on linearized differential equations, the Newmark method is applied to calculate steady-state periodic vibrations of the parametric vibration of constrained dynamical models. The numerical calculation is also demonstrated on a model of a mechanism with elastic connecting link.

De-multiplexing the required spectrum in a traffic demand into multiple non-adjacent granular spectrums for dynamic traffic grooming in EON

An elastic light-trail, the advanced version of a traditional light-trail, is one of the most recent dynamic traffic grooming technologies in an elastic optical network. In such networks, Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology to execute the RSA (routing and spectrum assignment) algorithm and implement an elastic light-trail as a result. However, the reconfigurable optical add-drop multiplexers (ROADMs) and bandwidth variable Wavelength Selective Switches (WSSs) are required to implement an optically switched and spectrum varying elastic lightpath. In addition to the hardware equipment mentioned above, Add Drop Couplers (ADC) and optical ON/OFF switches (OS) are required to facilitate elastic light-trail in an elastic optical network. Hereafter, deployment of Add Drop Couplers (ADC) and optical ON/OFF switches incurs a significant network cost to facilitate elastic light-trail implementation. Toward the approach for eliminating this costly hardware setup, we have highlighted the fragmentation problem that occurs in spectrum domain in an optical fiber link. In this problem, the entire spectrum range in an elastic optical link is fragmented into several non-contiguous free spectrum slots at an instance during a data transportation session. In this regard, we have proposed “Multiple multi-hop non-contiguous elastic lightpath - MMNCEL” algorithm, where the required spectrum B of a traffic demand r(s, d, B, T) is sliced into n distinct granular spectrums {b1, b2, … bn} according to the current availability and status of fragmented spectrum slots in an elastic optical link. Moreover, to setup an elastic lightpath, the algorithm allocates the same range of spectrum from every optical link in a route to preserve Spectrum Continuity Constraint (SCC), whereas, at each hop in a multi-hop elastic lightpath the algorithm performs opto-electrical conversion. In this paper, our objective is to achieve maximum network throughput in an elastic optical network without deploying ADC and optical ON/OFF switches. However, in this work, we have investigated optical spectrum utilization efficiency for the proposed MMNCEL, existing elastic light-trail (Multi-hop Elastic Light-trail algorithm - MELT) and elastic lightpath (Multi-hop elastic Lightpath algorithm - MEL), and performed comparison measurements preciously.

Slim NoC

Emerging chips with hundreds and thousands of cores require networks with unprecedented energy/area efficiency and scalability. To address this, we propose Slim NoC (SN): a new on-chip network design that delivers significant improvements in efficiency and scalability compared to the state-of-the-art. The key idea is to use two concepts from graph and number theory, degree-diameter graphs combined with non-prime finite fields, to enable the smallest number of ports for a given core count. SN is inspired by state-of-the-art off-chip topologies; it identifies and distills their advantages for NoC settings while solving several key issues that lead to significant overheads on-chip. SN provides NoC-specific layouts, which further enhance area/energy efficiency. We show how to augment SN with state-of-the-art router microarchitecture schemes such as Elastic Links, to make the network even more scalable and efficient. Our extensive experimental evaluations show that SN outperforms both traditional low-radix topologies (e.g., meshes and tori) and modern high-radix networks (e.g., various Flattened Butterflies) in area, latency, throughput, and static/dynamic power consumption for both synthetic and real workloads. SN provides a promising direction in scalable and energy-efficient NoC topologies.

Torsional vibrations of shafts of mechanical systems

The aim of the research is to compare the calculated dependencies for determining the equivalent rigidity of a mechanical system and to come to an agreement on the methods of compiling dynamic models for systems with elastic reducer couplings in applied and classical oscillation theories. As a result of the analysis, it was revealed that most of the damage in the mechanisms and their details is due to the appearance of oscillations due to the dynamic impact of various factors: shock and alternating loads, unbalanced parts of machines, etc. Therefore, the designer at the design stage, and the engineer in the process of operation should provide the possibility of regulating the oscillatory processes both in details and machines by means of creating rational designs, as well as the use of special devices such as vibration dampers, various vibrators with optimal characteristics. A method is proposed for deriving a formula for determining the equivalent stiffness of a double-mass oscillating system of a multistage reducer with elastic reducer links without taking into account the internal losses and inertia of its elements, which gives a result completely coinciding with the result obtained by the classical theory of small mechanical oscillations and allows eliminating formulas for reducing the moments of inertia of the flywheel masses and the stiffness of the shafts.

МАТЕМАТИЧНА МОДЕЛЬ ДЛЯ ДОСЛІДЖЕННЯ МЕХАНІЗМУ ПРИВОДА РОТОРА РОТОРНОГО ЕКСКАВАТОРА ЕР–315

Запропонована методика розрахунку динамічних навантажень у електромашинній та механічній системах привода ротора екскаватора. В методиці враховуються електромагнітні процеси у двигуні, податливість пружних ланок, коливання мас, демпфування у пружних ланках. Наведені результати розрахунків перехідних процесів у електромашинній та механічній системах.