Elastic Torque Research Articles

Development of an Automatic Elastic Torque Control System Based on a Two-Mass Electric Drive Coordinate Observer

Development of control system based on digital twins of physical processes is a promising area of research in the rolling industry. Closed-loop control systems are developed to control the coordinates of two-mass electromechanical systems in order to limit the dynamic loads on the equipment of main rolling lines. These control systems are based on observers (digital shadows) that indirectly detect (reconstruct) the roll speed and the elastic torque of the shaft (spindle) in real time. Notably, observers are required to work fast in order to reconstruct transients attributable to shock (impact) loads. Literature review shows that the known observers, which use complex algorithms to compute coordinates, do not respond fast enough. The paper analyzes the kinematic diagram of Mill 5000, a plate rolling mill. It presents oscillograms that prove that the elastic torque does oscillate as the rolls grip the strip dynamically. The authors hereof have developed an observer that reconstructs the coordinates of the uncontrolled mass (the shaft) and the spindle torque from the parameters of the controlled mass, namely the torque and speed of the motor. The paper further rationalizes an approach that consists of simulating the processes on a model to further directly configure them on the object. The authors analyze the transients of the reconstructed two-mass system coordinates, which are associated with the rolls gripping the strip. The paper compares data against oscillograms recorded on the mill itself. The accuracy is satisfactory. The proposed observer has been used to developed a three-loop automatic speed control system for the uncontrolled mass. Controller configurations are substantiated. The paper shows coordinates obtained by simulation modeling as functions of time. It further presents experiments run on Mill 5000; the conclusions are that the amplitude and oscillations of the elastic torque drop significantly. The paper concludes with recommendations on industrial adoption of the observer and the novel electric drive coordinate control system. Study presented herein substantiates and implements a concept of developing algorithms that solve specific problems and are readily implementable on the existing equipment without need for additional computing devices. The contribution of the paper consists of stating and solving the problem of developing and testing an automatic elastic torque control system for the shaft of a heavy-duty rolling mill. This system has been implemented in the form of algorithms that run in the software of the existing industrial controllers (PLCs). It is simple and performs well. It does not need additional sensors or computers to be implemented, nor does it rely on complex computational algorithms. Such algorithms are based on computational tables that require a priori data on numerous process parameters. In our literature review, we have not come across any industrial implementation of such algorithms on hot-rolling mills.

Orientational Correlations in Active and Passive Nematic Defects.

We investigate the emergence of orientational order among +1/2 disclinations in active nematic liquid crystals. Using a combination of theoretical and experimental methods, we show that +1/2 disclinations have short-range antiferromagnetic alignment, as a consequence of the elastic torques originating from their polar structure. The presence of intermediate -1/2 disclinations, however, turns this interaction from antialigning to aligning at scales that are smaller than the typical distance between like-sign defects. No long-range orientational order is observed. Strikingly, these effects are insensitive to material properties and qualitatively similar to what is found for defects in passive nematic liquid crystals.

Nonlinear vibration of the spiral bevel gear under periodic torque considering multiple elastic deformation evaluations due to different bearing supports

This paper investigates two parameters effect on vibrational responses of the spiral bevel gear. Changing the gear system overall stiffness (GSOS) considering elastic deformation and periodic torques are the two parameters which are represented as the main goals of this study. In order to investigate the effects of shaft stiffness and elastic deformation, two different cases with different support locations are considered. The first case is presented by locating the support close to the gear, and in the latter one, the distance between gear and support is increased. Besides, to study the effect of torque, two main types are considered: constant and periodic excitation torque. To illustrate the dynamic behavior, the governing differential equations are solved numerically according to the Runge–Kutta method. The equations are nonlinear due to backlash and time-varying coefficients as the results of GSOS variation. Vibrational phenomena are illustrated by means of bifurcation diagrams, RMS, and Poincaré maps. Particular vibrational behaviors such as “chaos” and “period-doubling” phenomena are illustrated with details. By investigating the effect of shaft stiffness, results show that when the support is far away from gear, the vibration response increased by 67.5%. Moreover, while the input torque is constant, the support movement does not cause undesirable responses such as chaotic or period-doubling responses. The periodic torque causes undesirable responses such as chaos and bifurcation and period-doubling responses.Article HighlightsWhat is done in the present paper can be mentioned in three main parts:The nonlinear dynamics of the spiral bevel gear pair under two different support situations is investigated in this paper.To scrutinize the dynamic behavior of the spiral bevel gear-pair in a nearly real situation, the input driver torque is periodically variable.The results show that the spiral bevel gear pair may comprise chaotic response with periodic torque excitation if the bearing supports locate far enough from the gears.

Conversion to Extension Contracture as a Means of Correction of Severe Flexion Contracture of the PIP Joint Using a Modified Dynamic External Fixator.

Background: This is a retrospective case series investigating the outcomes using a dynamic external fixator (DEF) for treatment on severe flexion contractures at the proximal interphalangeal (PIP) joint. Severe flexion contractures of the PIP joint occurring after multiple operations and neglected over a long period of time are difficult to treat. The recurrence of contracture, even after successful treatment, is inevitable in patients with severe cases. In this study, we defined the severity of PIP joint contracture based on the active range of motion (ROM), soft tissue condition, and duration of the contracture. We also illustrated the strategy, results, and complications of using a DEF with rubber bands in these severe cases. Methods: We studied 11 fingers of 10 patients with PIP joint contracture treated by DEF. These were fixed at a small arc and neglected for an average 4.1 years (range, 1-9 years). The temporal Kirshner wire (K-wire) fixation after achieving an extension via DEF was maintained for 9.1 weeks on average. We retrospectively reviewed the results of these patients with an average 2-year follow-up. Results: Our method yielded favorable results upon retrospective evaluation. The average active ROM of the affected PIP joint improved from 90/96° to 34/83° with a functional arc and good patient satisfaction. The elastic force induced by strong rubber bands was safe and effective. The first step of joint space widening was the key to obtaining a successful joint extension afterwards. Serious progression of osteoarthritis at the PIP joint and pin-site fracture were a complication in each one case. Conclusions: In this study, we evaluate the surgical strategy of using DEFs powered by elastic torque from rubber bands to treat severe cases of flexion contractures of fingers. We first created extension contracture intentionally, followed by promoting flexion movement during follow-up in this group of patients.

Adaptive neural backstepping control for flexible-joint robot manipulator with bounded torque inputs

Aiming at tracking control with bounded torque inputs of the flexible-joint robot manipulators, we propose a generalized saturated adaptive controller based on backstepping control, singular perturbation decoupling and neural networks. First, by using the singular perturbation theory, the full-order rigid-flexible dynamics of the robot manipulator is decoupled into a slow subsystem and a fast subsystem. Second, saturated sub-controller by backstepping method is proposed for the slow subsystem, where the projection-type parameter adaptation and a class of saturation functions are applied to make the torque inputs bounded, and a saturated neural network approximator is involved to simplify the control law and to compensate for the uncertain nonlinearity. Third, for fast subsystem, a new filtered tracking error of the elastic torque is used in the fast control law to make the boundary layer subside quickly. In addition, explicit but strict stability analysis is given for the system. Finally, comparisons indicate that the proposed controller results in a more satisfactory tracking performance with keeping the control inputs bounded within the given range all the time and superior anti-disturbance capability.

Nonequilibrium Dynamics of a Magnetic Nanocapsule in a Nematic Liquid Crystal.

Colloidal particles in nematic liquid crystals show a beautiful variety of complex phenomena with promising applications. Their dynamical behaviour is determined by topology and interactions with the liquid crystal and external fields. Here, a nematic magnetic nanocapsule reoriented periodically by time-varying magnetic fields is studied using numerical simulations. The approach combines Molecular Dynamics to resolve solute–solvent interactions and Nematic Multiparticle Collision Dynamics to incorporate nematohydrodynamic fields and fluctuations. A Saturn ring defect resulting from homeotropic anchoring conditions surrounds the capsule and rotates together with it. Magnetically induced rotations of the capsule can produce transformations of this topological defect, which changes from a disclination curve to a defect structure extending over the surface of the capsule. Transformations occur for large magnetic fields. At moderate fields, elastic torques prevent changes of the topological defect by tilting the capsule out from the rotation plane of the magnetic field.

Frictional Granular Matter: Protocol Dependence of Mechanical Properties.

Theoretical treatments of frictional granular matter often assume that it is legitimate to invoke classical elastic theory to describe its coarse-grained mechanical properties. Here, we show, based on experiments and numerical simulations, that this is generically not the case since stress autocorrelation functions decay more slowly than what is expected from elasticity theory. It was theoretically shown that standard elastic decay demands pressure and torque density fluctuations to be normal, with possibly one of them being hyperuniform. However, generic compressed frictional assemblies exhibit abnormal pressure fluctuations, failing to conform with the central limit theorem. The physics of this failure is linked to correlations built in the material during compression from a dilute configuration prior to jamming. By changing the protocol of compression, one can observe different pressure fluctuations, and stress autocorrelations decay at large scales.

Influence of a Gap in a Mill Stand’s Drive Line on the Elastic Torque

The elastic torque in a section of the drive line with a gap is determined for a mill stand, in the case of variable external rolling torque. A correction factor is introduced to take account of the gap.

Programmable Transformation and Controllable Locomotion of Magnetoactive Soft Materials with 3D-Patterned Magnetization.

Magnetoactive soft material (MASM) is distinguished for multifunctional shape manipulations under magnetic actuation, thereby holding a great promise in soft robotics, actuators, electronics, and metamaterials. However, the current research of MASM with continuum hard-magnetic profiles focuses little on the transformation mechanism, high dimensional shape transformation, and multistable locomotion. Herein, we developed a systematic methodology for programmable transformation and controllable locomotion of MASM with 3D-patterned continuum magnetization. An iterative computational model based on the equilibrium between magnetic torque and deformation-induced elastic torque was developed for precise prediction of MASM transformation. Multidimensional and complex shape manipulation ability of MASM was demonstrated by magnetically actuated transformations, including 1D to 2D, 2D to 3D, and 3D to 4D transformations of solid MASM, 2D to 3D pattern transformation of MASM-based elastin-like mesh, and 3D to 4D transformation of MASM-based cuboidal lattice. Multistable and controllable locomotion of MASM was verified by multimodal locomotion behaviors of a scallop-inspired robot for wall climbing in a dry frame and drug delivery in wet stomach, including roll, open, and close under self-locked and unlocked states.

In Situ Compatibilization of Polyamide 6/Carboxylated Acrylonitrile Butadiene Rubber Blends with Polyhedral Oligomeric Silsesquioxane

AbstractThe aim of the study is to prepare thermoplastic elastomer composites of polyamide (PA6) with carboxylated acrylonitrile butadiene rubber (XNBR), compatibilized with polyhedral oligomeric silsesquioxane with epoxy groups (POSS‐epoxy). The addition of POSS‐epoxy, particularly 3.5 phr, improved the specialty characteristics of the PA/XNBR thermoplastic‐elastomer blend. The PA/POSS/XNBR mainly showed a considerable improvement in the elastic torque. The in situ compatibilization is confirmed by density and oil swelling analyses. The structural property relationships of the vulcanized thermoplastic, measured by XRD, DSC and Raman spectroscopy, revealed there are changes in the chemical structure induced by the molecular interactions of PA‐POSS‐XNBR. The Raman spectra confirmed the presence of silane in the PA/XNBR blend. The crystallinity results obtained from the XRD spectra of the PA/XNBR blend are modified by the POSS‐epoxy, corroborating the oil swelling results.

Fretting test rig with variable normal force

Fretting is small amplitude reciprocating sliding between surfaces, and it may quickly causes surface cracks, which can continue growing under cyclic loads, until the structure breaks entirely as a result of the fretting fatigue. Fretting can also produce hardened wear particles as a result of adhesive wear, which then accelerates abrasive wear. In this case, the community uses the term fretting wear. The design of heavily loaded contacts, susceptible to fretting, is a difficult task because there is no generally accepted design guide. More extensive fretting research is needed to create them. This paper introduces detailed design phases for a equipment (rig) for a variable normal force fretting test. Supporting high radial and normal forces such that there is minimal run-out between the specimens was the most significant design challenge. The combination of a hydrostatic radial bearing and elastic torque shaft was selected for the detail design phase based on FE-analyses, calculations, and overall evaluation. The frame of the test rig consists of the main frame, which supports mainly the normal force and two torque frames, which support torque cylinders. Many solutions, which were found to be working in the current "ring-ring" apparatus of Tampere University, could be utilized in the new test rig like the tapered connections of the specimens, the elastic rod of the torque lever, axial displacement plate, and contact pressure adjustment system. The designed test rig enables fretting tests with 0 Hz to 20 Hz cycle frequency so that normal and tangential force or displacement can be controlled independently of each other. The normal force cannot change from compression to tension dynamically, but the adhesive force of the contact can be measured by slowly increasing the tension force. The designed fretting test rig fulfills all essential requirements, which were set.

Effect of viscoelastic properties on passive torque variations at different velocities of the knee joint extension and flexion movements.

This study aimed to investigate the rate of passive torque variations of human knee joint in the different velocities of knee flexion and extension movements. Ten healthy men were invited to participate in the tests. All passive torque tests were performed for the knee joint extension and flexion on the sagittal plane in three different angular velocities of 15, 45, and 120°/s; in 5 consecutive cycles; and within 0° to 100° range of motion. The electrical activity of knee joint extensor and flexor muscles was recorded until there was no muscle activity signal. A Three-element Solid Model (SLS) was used to obtain the viscose and elastic coefficients. As the velocity increases, the stretch rate in velocity-independent tissues increases, and the stretch rate in velocity-dependent tissues decreases. By increasing the velocity, the resistance of velocity-dependent parts increases, and the velocity-independent parts are not affected by velocity. Since the first torque that resists the joint movement is passive torque, the elastic and viscous torques should be simultaneously used. It is better to perform the movement at a low velocity so that less energy is lost. The viscoelastic resistance of tissues diminishes. Graphical abstract.

Curing, thermal and mechanical properties of waste tyre derived reclaimed rubber–wood flour composites

The usage of polymer composites has increased dramatically with the years, especially composites with recycled waste materials since they aid in reducing the environmental pollution. The current study focuses on the use of both waste reclaimed rubber (RR) and wood flour (WF) to make sustainable polymer composites. The curing, thermal, mechanical and morphological properties of the composites were studied. Results showed that the cure rate index and elastic torque of the samples increased with the amount of WF. The mechanical properties of RR–WF composites decreased with increasing wood flour content and tensile strength dropped from 3.33 MPa to 1.35 MPa due to poor interfacial adhesion between WF and RR matrix. The glass transition temperature of styrene–butadiene rubber fraction in composites shifted from ∼15 °C to 10 °C with the addition of WF showing incompatibility between the two phases. The scanning electron microscopy results confirmed incompatibility behavior within the composites as shown by pull-out characteristics of WF from the RR matrix at high content. The results showed that the composite with 10 phr of WF has superior thermal stability, water absorption, and mechanical properties compared to other composites.

CHARACTERIZATION AND CORRELATION OF THE NETWORK CHAIN DENSITY TO THE PROPERTIES OF FLUOROELASTOMER RUBBER

ABSTRACTThe concentrations of triallyl isocyanurate (TAIC) in a peroxide-curable fluoroelastomer terpolymer containing 67 wt% of fluorine were varied to generate compounds of differing crosslink densities. Experimental analysis was undertaken using rheometry, hardness, stress–strain (Mooney–Rivlin), equilibrium solvent swell, and low-field nuclear magnetic resonance (NMR) using the double quantum (DQ) technique. Increasing the TAIC concentration caused a systematic rise in rheometry elastic torque, hardness, and tensile strength, whereas both elongation at break and swelling levels decreased. These results are concurrent with an enhanced overall level of crosslinking, which was confirmed by the steady increase of the Mooney–Rivlin C1 values. DQ NMR analysis using hydrogen and fluorine probes and subsequent application of fast Tikhonov regularization to the corrected intensity data were particularly useful in discerning the inhomogeneous nature of the compound morphology. The spatial distribution of the crosslink density suggests that the compound consists of small, highly crosslinked/entangled polymerized TAIC domains embedded within the elastic crosslinked matrix. A concentration of 3 phr of TAIC is optimal according to compression set testing.

A high transmittance and fast response in-plane switching liquid crystal display with the zero-azimuth anchoring layers on the electrodes

An in-plane switching (IPS) liquid crystal display (LCD) containing the zero-azimuth anchoring layers formed only on the electrodes and rubbed polyimide (PI) covered on the other areas was successfully developed. This configuration was realized using photoreactive PI with photo-radical generation units and the mask exposure technique. The maximum transmittance (Tmax) of this LCD was 1.12 times higher than that of a conventional IPS LCD. This was attributed to a large aperture in the voltage-on state because the nematic liquid crystals (NLCs) on the electrodes were barely anchored to the surface, such that the NLCs could be rotated by applying a small in-plane electric field above the electrodes, and by an elastic torque caused by the twisted NLCs between the electrodes. Furthermore, the response times of this LCD were equivalent to those of a conventional IPS LCD because the NLCs between the electrodes quickly recovered to their initial orientation after removing the electric field, and the NLCs on the electrodes followed this movement. This novel LCD is termed a ‘partially zero-azimuth anchoring IPS (PZ-IPS) LCD’, which is the first practical LCD utilizing these weak anchoring characteristics in the history of LCDs.

Orientation Dependent Interaction and Self‐Assembly of Cubic Magnetic Colloids in a Nematic Liquid Crystal

AbstractSpherical microparticles dispersed in nematic liquid crystals have been extensively investigated in the past years. Here, experimental studies are reported on the elastic deformation, colloidal interaction, and self‐assembly of hematite microcubes with homeotropic surface anchoring in a nematic liquid crystal. It is demonstrated that the colloidal interaction and self‐assembly of cubic colloids are orientation dependent. In a notable departure from the conventional microspheres, the microcubes stabilize diverse structures, such as bent chains, branches, kinks, and closed‐loops. The microcubes reorient under external rotating magnetic field, thereby experiencing an elastic torque in the medium, which allows us to measure the magnetic moment through competition between elastic and magnetic torques. The findings envisage that the faceted magnetic colloids in liquid crystals are potential for developing new functional magnetic materials with specific morphologies.

A new control method of flexible-joint manipulator with harmonic drive

Considerable elasticity and nonlinear friction caused by harmonic transmission challenge the performance of flexible-joint manipulators. The uncertain dynamics of manipulator and the inadequate measurable states also limit the controller design. A new control method is proposed to address these problems, achieving the precise motion control of the flexible-joint manipulator. The method consists of three cascaded controllers: an adaptive controller, a torque-tracking controller, and a motor controller. The adaptive controller was adopted to generate the desired torque ensuring the robustness for uncertain dynamics. The torque-tracking controller derived the position compensation for motor control according to the torque error. As the elastic torque is under control, the vibration caused by harmonic drive can be eliminated. The motor was controlled based on poles-assignment method and friction compensation. The Kalman observer based on the Brownian motion model observed both velocity and the high-order derivatives of torque sensing. The stability of the control method was strictly proved. Calibration was performed on each joint to obtain the required joint stiffness and motor friction parameters. The control method was verified on a single joint and the frequency response of the system was obtained. The results show that the controller has good performance. The controller was realized on the self-developed seven-degree-of-freedom manipulator. The results reveal that the controller has high-precision tracking performance.

Colloidal interactions and unusual crystallization versus de-mixing of elastic multipoles formed by gold mesoflowers

Colloidal interactions in nematic liquid crystals can be described as interactions between elastic multipoles that depend on particle shape, topology, chirality, boundary conditions and induced topological defects. Here, we describe a nematic colloidal system consisting of mesostructures of gold capable of inducing elastic multipoles of different order. Elastic monopoles are formed by relatively large asymmetric mesoflower particles, for which gravity and elastic torque balancing yields monopole-type interactions. High-order multipoles are instead formed by smaller mesoflowers with a myriad of shapes corresponding to multipoles of different orders, consistent with our computer simulations based on free energy minimization. We reveal unexpected many-body interactions in this colloidal system, ranging from de-mixing of elastic monopoles to a zoo of unusual colloidal crystals formed by high-order multipoles like hexadecapoles. Our findings show that gold mesoflowers may serve as a designer toolkit for engineering colloidal interaction and self-assembly, potentially exceeding that in atomic and molecular systems.

Dynamic Torque Limitation Principle in the Main Line of a Mill Stand: Explanation and Rationale for Use

This paper substantiates why it is necessary to limit the dynamic loads in stand shafts when closing angular gaps. The paper is a feasibility study of a concept developed specifically to limit each of the factors that affect amplitude of the dynamic torque; limitations applied are determined on a case-by-case basis. The research team studied the components of elastic torque in a dual-mass electromechanical system of Mill 5000 caused by vibrations arising from the elasticity of transmission as well as from the vibrations caused by elastic collision itself. It is shown that the lowest possible pre-acceleration is necessary for decreasing the dynamic coefficient at a near-nominal load torque. A principle of limiting dynamic loads when closing an angular gap is proposed, which implies collecting tachograms of an electric drive subjected to positive or negative acceleration before and after the fed metal is captured. The research team has developed drive control principles to implement this approach. The recommendation is to upgrade the electric drives of the reversing stand in Mill 5000.

Limitation of dynamic loads in the mine hoist based on the elastic torque feedbacks

In this article the results of a study of the efficiency of using feedbacks on the elastic torque are presented using the example of a three-mass calculating scheme. Feedbacks are synthesized based on the solution of the inverse dynamic problems according to given law of variation of the elastic torque in order to limit the dynamic loads in a single-end mine hoist. It is shown that the application of the proposed method of synthesis allowed determining not only the structure but also the parameters of feedback, which provide the desired character of transient processes. The results of a numerical study of the effectiveness of the proposed control system for limiting dynamic loads in the mine hoisting machine C1.2×1.0 are presented.