Relative Angular Position Research Articles

Examination of load effects of an alternating current synchronous hydraulic drive

Alternating current hydraulic systems can be divided into two large groups based on the electrical analogy: synchronous alternating current hydraulic drives and asynchronous alternating current hydraulic drives. The three main building units of alternating current systems are a hydromotor, a hydrogenerator and a phase space connecting the two main units. The relative angular position of the hydrogenerator and the hydromotor is changed by the loads occurring during operation. In this article I would like to present the load effects.

Hydrodynamic force interaction of two fixed spheres in a wall-bounded linear shear flow

We examine the modulations of the drag coefficient Cd and lift coefficient Cl on a spherical particle caused by the presence of a neighboring sphere when positioned in close proximity to a wall. Data are generated through the utilization of a fast and accurate Particle-Resolved Direct Numerical Simulation (PR-DNS) method that relies on the Direction-Splitting algorithm and that was extensively validated in our prior study (Goyal and Wachs, 2023a, 2023b; Morente et al., 2023). We further validate the method in the flow configuration of the present study by comparing them with data published in the literature. We consider three Reynolds numbers Re=20, Re=50 and Re=100, which describe the flow conditions in the vicinity of the wall. The primary sphere is positioned at a distance δ from the wall, while the neighboring sphere is positioned at a constant distance from the primary sphere encompassing all possible angular positions θ. We report the modulations of Cd and Cl compared to a situation without any neighboring sphere as a function of δ, θ and Re. The inclusion of a wall intensifies the influence of the neighboring sphere on the primary sphere and significantly modifies the values of Cd and Cl. We attempt to relate the values of the modulations of Cd and Cl to the modulations in the contours of the pressure and of the spanwise vorticity on the surface of the primary sphere. We take advantage of the periodic nature of Cd and Cl as a function of the relative angular position θ of the neighboring sphere and propose a Fourier Predictive Model (FPM) to effectively represent the data using a finite number of modes in the cosine Fourier series. We show that our FPM is able to estimate the modulations of Cd and Cl excellently with a coefficient of determination R2≳0.99 in the parameter space investigated in our study.

Predictive saccades and decision making in the beetle-predating saffron robber fly.

Internal predictions about the sensory consequences of self-motion, encoded by corollary discharge, are ubiquitous in the animal kingdom, including for fruit flies, dragonflies, and humans. In contrast, predicting the future location of an independently moving external target requires an internal model. With the use of internal models for predictive gaze control, vertebrate predatory species compensate for their sluggish visual systems and long sensorimotor latencies. This ability is crucial for the timely and accurate decisions that underpin a successful attack. Here, we directly demonstrate that the robber fly Laphria saffrana, a specialized beetle predator, also uses predictive gaze control when head tracking potential prey. Laphria uses this predictive ability to perform the difficult categorization and perceptual decision task of differentiating a beetle from other flying insects with a low spatial resolution retina. Specifically, we show that (1) this predictive behavior is part of a saccade-and-fixate strategy, (2) the relative target angular position and velocity, acquired during fixation, inform the subsequent predictive saccade, and (3) the predictive saccade provides Laphria with additional fixation time to sample the frequency of the prey's specular wing reflections. We also demonstrate that Laphria uses such wing reflections as a proxy for the wingbeat frequency of the potential prey and that consecutively flashing LEDs to produce apparent motion elicits attacks when the LED flicker frequency matches that of the beetle's wingbeat cycle.

Математическая модель, алгоритм формирования вектора состояния и техническая реализация многокоординатного задающего органа внутрикамерных манипуляторов

The purpose of the study is a development of a mathematical model and an algorithm for the calculation of the state vector of a multi-axes delta-type control joystick for moving special purposes arm manipulators by a human operator in the loop. Research methods. The paper considers the existing methods of remote control of intrachambers special purpose arm manipulators with a human operator in the control loop, identifies the advantages and disadvantages of existing solutions. The task of synthesizing the optimal control stick to ensure driving of the manipulator in 3D-space was set. Today, nuclear industry enterprises widely use hermetic chambers in which copy-type electromechanical manipulators are installed. The manipulation system includes an arm manipulator installed directly in a sealed chamber, and its kinematically similar control arm. The operator manually moves the control arm, the trajectory of which is repeated inside the chamber by the arm manipulator. Taking into account moral and physical obsolescence, the introduction of modern approaches to the human-machine interaction is required. The paper proposes a mathematical model for calculation the state vector (linear and angular coordinates) of a delta-type control stick from measured information about the relative angular position in its rotational kinematic pairs. Results of the study. An algorithm for calculating the coordinates of the handle of the control stick is synthesized based on a priori information about the relative position of the elements in the delta-mechanism. Taking into account the additional discrete and proportional controls located on the handle of the control stick, the proposed algorithm and its practical implementation make it possible to introduce effective manipulator control modes. Conclusion. The main results of the work include a mathematical model and an algorithm for generating the state vector of the delta-type control stick, which allows the operator to form the linear and angular velocity vectors of the arm manipulator and its gripper movement by one hand. The technical implementation of the control stick and algorithm, as well as its test operation with a dual arm manipulator system, showed the high efficiency of the proposed solutions.

Bearing Sensor for 3D Localization and Swarm Centroid Detection

A bearing sensor measures its orientation relative to a landmark. Such sensors enable tracking and localization. Since small Unmanned Aerial Vehicles (UAVs) suffer from payload limitations, they must be equipped with lightweight sensors with low power consumption. This paper presents two implementations for bearing sensors. First, a novel vision-based sensor based on a camera and a spherical mirror that enables wide view. This sensor is lightweight and low cost ( 20 [g] and under 8 [USD]). Second, a novel, laser-based beacon together with a photo-diode based sensor which enables to better distinguish between multiple landmarks while keeping inclination mismatch robustness. We present the scheme for detecting the relative angular position of an aerial agent to a light-based landmark in 3D. We also present algorithms for the localization of a UAV, and swarm centroid detection, both using such bearing observations. Finally, we demonstrate our sensors and algorithms in real-world experiments and provide their accuracy.

Open water performance of B-Series marine propellers in tandem configurations

The hydrodynamic performance of 4-bladed B-series tandem propellers with different design configurations in open water is numerically investigated using a RANS-based CFD solver. The integration of the co-rotating aft propeller increases the resultant thrust and torque coefficients in the entire range of propeller loading. The open water efficiency at moderate to high propeller loadings is reduced, but the range of positive thrust output is increased.Due to the induced velocities and flow acceleration caused by the forward propeller, a higher pitch ratio should be adopted for the aft propeller to generate the blade forces. While the forward propeller behaves very similar to a conventional single propeller, the thrust and torque coefficients of the aft propeller show minimal variations with advance coefficient due to high induced velocities. At higher advance coefficients and blade sections closer to the hub there is greater deviation of forces generated by the aft propeller blade as compared to a single propeller of similar design. Parametric investigations are presented, highlighting the influence of axial spacing, relative angular position, pitch difference, and diameter ratio between the forward and aft propellers on the open water performance. From the present study, a pitch ratio difference of 0.3 may be maintained between the two propellers for optimal open water performance.

Numerical analysis of two-phase ferrofluid forced convection in an annulus subjected to magnetic sources

This work presents a numerical analysis of heat transfer and flow characteristics of a ferrofluid inside an annulus. The ferrofluid flow is subjected to multiple magnetic fields emanating from current-carrying wires. The inner tube of the annulus is heated uniformly while the outer tube is insulated. Two-phase modeling is conducted by incorporating Brownian, thermophoretic, and magnetophoretic effects. The dependence of ferrofluid viscosity and thermal conductivity on the magnetic field intensity and temperature is considered. The finite volume approach is applied to solve the governing equations. The influences of magnetic number, relative angular position, the number of magnetic sources, and also radius ratio of the annulus on the augmentation of heat transfer and pressure losses are examined. Numerical findings show that the applied magnetic fields induce a strong secondary flow whose magnitude may be several times higher than that of the inlet velocity. In the case of two current-carrying wires, the rate of heat transfer is enhanced by increasing the relative angular distance between the two magnetic sources and shows a maximum at Δθ=180°. It is found that there exists an optimum number of magnetic fields that maximize the rate of heat transfer. Additionally, the average Nusselt number declines as the radius ratio rises.

Scan Mirror Assembly for the Multispectral Scanning Polarimeter of Aerosol-UA Space Mission

In this paper, the scan mirror assembly for the space experiment Aerosol-UA scanning polarimeter (ScanPol) is described. The aim of the Ukrainian space mission Aerosol-UA is to create a database of the optical characteristics of aerosol and cloud particles in the Earth’s atmosphere over a long period of time. The optical characteristics of aerosol and cloud particles are derived from multiangular measurements. Multiangular scanning in ScanPol is provided by scan mirror assembly, which contains a reactive torque compensator electric motor and two scan mirrors, mounted on the shaft of the motor. The control system of the scan mirror assembly enables continuous scanning with a constant speed of the space under investigation. This control system tolerates movements of the orbiting satellite and preserves invariability of its spatial position. The polarimeter ScanPol is designed to acquire spatial, temporal, and spectral-polarimetric measurements simultaneously to minimize instrumental effects and “false” polarizations due to scene movement. Instrumental polarization, introduced by the mirrors of scan assembly, is minimized through the polarization compensated two-mirror scheme which contains two mirrors with orthogonal planes of incidence. In this paper, the polarimetric model of the polarization compensated two scan mirrors is considered. Theoretical calculations are given that substantiate the maximum allowable error of the relative angular position of the mirrors is 15 arcmin (0.25°), and the method of adjustment and control of the angular position of the mirrors is proposed. The polarization properties of mirrors are modelled in the spectral range of 370–1680 nm for bulk oxide-free aluminum. It is obtained that the maximum instrumental polarization of the unadjusted mirror system should be observed at 865 nm, and thus, the polarization characteristics of the scanning system at a given wavelength could be considered as representative for ScanPol in general. The key steps for assembling the unit are illustrated.

Viscosity Control of Magnetorheological Fluid by Power Saving Magnetizing Mechanism Using Movement of Permanent Magnet

Generally, the magnetic field applied to a magnetorheological fluid (MRF) is generated by electromagnets. Electromagnets consume electric power during MRF magnetization, which is an issue. In this study, we examine two kinds of magnetizing mechanism using a permanent magnet, instead of electromagnets, to save electric power and generate a magnetic field on the MRF. One mechanism linearly moves the permanent magnet into the magnetic circuit composed of yokes. The magnetic field intensity on the MRF is then controlled by changing the overlap between the magnet and the yokes. The other mechanism rotates a permanent magnet in the magnetic circuit. The magnetic field intensity on the MRF is then controlled by changing the relative angular position between the magnet and the yokes. These two mechanisms normally generate force or torque on the magnet toward a magnetically stable position concerning the magnet, and the force or torque causes power consumption to hold and move the magnet. We design herein special magnetic circuits and a cancelation mechanism for the force or torque that drastically reduce the power consumption during the MRF magnetization compared with an electromagnet-type magnetizing device.

Investigation of Inter-Frequency Signal Delays on Board Glonass Navigation Satellites

The problem of inter-frequency signal delays estimation of GLONASS system navigation satellites is considered. Such signal delays in the radio-frequency channel of navigation satellites are a source of instrumental error of pseudorange measuring. A method for estimating the inter-frequency signal delays is proposed, based on the calculation of the first differences of pseudorange measurements on navigation satellites, the relative angular position of which differs by no more than 1°. An experiment on estimating the inter-frequency signal delays based on the developed method was performed. The experiment is based on the use of calibrated navigation user equipment to separate errors caused by signal delays in the receiver and the navigation satellite. Furthermore, to minimize the influence of the Earth’s ionospheric layer, only those measurements that are obtained at a low value of the total electron content (TEC) are included in the processing. Pseudorange measurements from the signals of navigation satellites of the GLONASS and GPS systems were used as the initial data. The estimation results for all GLONASS orbit group satellites were compared with the form values provided as part of the navigation frame. The results of experimental studies were analyzed and the standard deviations of the delays of GLONASS orbit group were obtained. To confirm the adequacy of the results, the internal convergence of the results was verified and the error of the developed method for estimating the inter-frequency delays of navigation satellites was determined.

Modulation of Kinesin’s Load-Bearing Capacity by Force Geometry and the Microtubule Track

Kinesin motors and their associated microtubule tracks are essential for long-distance transport of cellular cargos. Intracellular activity and proper recruitment of kinesins is regulated by biochemical signaling, cargo adaptors, microtubule-associated proteins, and mechanical forces. In this study, we found that the effect of opposing forces on the kinesin-microtubule attachment duration depends strongly on experimental assay geometry. Using optical tweezers and the conventional single-bead assay, we show that detachment of kinesin from the microtubule is likely accelerated by forces vertical to the long axis of the microtubule due to contact of the single bead with the underlying microtubule. We used the three-bead assay to minimize the vertical force component and found that when the opposing forces are mainly parallel to the microtubule, the median value of attachment durations between kinesin and microtubules can be up to 10-fold longer than observed using the single-bead assay. Using the three-bead assay, we also found that not all microtubule protofilaments are equivalent interacting substrates for kinesin and that the median value of attachment durations of kinesin varies by more than 10-fold, depending on the relative angular position of the forces along the circumference of the microtubule. Thus, depending on the geometry of forces across the microtubule, kinesin can switch from a fast detaching motor (median attachment duration <0.2 s) to a persistent motor that sustains attachment (median attachment duration >3 s) at high forces (5 pN). Our data show that the load-bearing capacity of the kinesin motor is highly variable and can be dramatically affected by off-axis forces and forces across the microtubule lattice, which has implications for a range of cellular activities, including cell division and organelle transport.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ТЕМПЕРАТУРНЫХ И ТОЧНОСТНЫХ ХАРАКТЕРИСТИК ДВУСТОРОННЕГО ТОРЦЕШЛИФОВАЛЬНОГО СТАНКА

The paper proposes a methodology for experimental studies of double-sided face grinding machines on the criterion of heat resistance, including: method of simulating a grinding process; measurement of temperature; measurement of changes in relative angular position of the circles; the measurement of processing errors. The proposed methods for experimental studies of the thermal behavior and errors in the machining of a double-sided face grinder allow for fine-tuning of the machine under production conditions. At the same time, preliminary tests of a double-sided face grinder show that when grinding an industrial batch of cylindrical rollers, excessive temperatures are distributed unevenly across the machine nodes both at idle and during grinding. The ends of the spindle heads and the stand have the greatest excess temperature when working at idle, and when grinding - on the surface of the machine, located in close proximity to the grinding zone. The nature of changes in excess temperatures of characteristic points and coolant when simulating the grinding process on the machine completely coincided with the experimental data obtained on a working machine.

Two Degree-of-Freedom Fiber-Coupled Heterodyne Grating Interferometer with Milli-Radian Operating Range of Rotation.

In the displacement measurement of the wafer stage in lithography machines, signal quality is affected by the relative angular position between the encoder head and the grating. In this study, a two-degree-of-freedom fiber-coupled heterodyne grating interferometer with large operating range of rotation is presented. Fibers without fiber couplers are utilized to receive the interference beams for high-contrast signals under the circumstances of large angular displacement and ZEMAX ray tracing software simulation and experimental validation have been carried out. Meanwhile, a reference beam generated inside the encoder head is adopted to suppress the thermal drift of the interferometer. Experimental results prove that the proposed grating interferometer could realize sub-nanometer displacement measurement stability in both in-plane and out-of-plane directions, which is 0.246 nm and 0.465 nm of 3σ value respectively within 30 s.

Calculation of Commutator Curve in Steady-State Operation Mode of Traction Motor with Simple Lap Armature Winding

The article is focused on the applicable methods of the commutator curve calculation. This curve provides a basis for the evaluation of the flashover appearance tendency on a commutator. It is reported that such methods demonstrate either its limited applicability, which is determined by its narrow focus on the certain kinds of commutator motors, or incapacity to provide required calculation accuracy. The basis for the calculation method presented in the article is numerical differentiation of the curve of coil flux linkage versus its relative angular position. Usage of the proposed method allows for the good convergence of the calculated bar-to-bar voltages with the experimental ones.

Induction machine model with space harmonics for fault diagnosis based on the convolution theorem

Fault diagnosis of induction machines (IMs) requires a fast model of the machine, for adjusting fault thresholds in data-driven diagnostic methods, for computing the residuals in model-driven diagnostic systems, or for training autonomous expert systems. Due to the interaction between time and space harmonics under faulty conditions, this model must simulate very accurately the space harmonics of the air gap magnetomotive force (MMF) generated by the machine’s windings. But the computation of the phases’ inductances, taking into account the spatial harmonics of the MMF, for every angular position of the rotor, and under non-symmetrical, faulty conditions, is a time-consuming task in IMs’ models. In this paper, a very fast method for obtaining the inductances of rotating electrical machines is proposed, based on a single discrete circular convolution. With the proposed approach, the mutual inductances of two phases, taking into account the spatial harmonics of the air gap MMF, are calculated for every relative angular position using a single equation, solved with the fast Fourier transform (FFT). Asymmetrical winding distributions, and the linear rise of the air gap MMF across skewed slots are easily modeled without increasing the computation time. The proposed method is introduced theoretically and validated with an experimental test-bed using commercial induction motors with forced broken bars faults.

CFD investigation of three-dimensional flow phenomena in a JAEA 127-pin wire-wrapped fuel assembly

This paper presents a RANS (Reynolds Averaged Navier-Stokes simulation) based CFD (Computational Fluid Dynamics) investigation of the three-dimensional flow phenomena in a JAEA (Japan Atomic Energy Agency) 127-pin wire-wrapped fuel assembly. Complicated and vortical flow phenomena in the wire-wrapped fuel bundles have been elucidated by a CFD analysis with a high resolution scheme and a shear stress transport (SST) turbulence model, and by a vortex structure identification technique based on the critical point theory. The CFD results show a good agreement with the JAEA experiment results with the 127-pin wire-wrapped fuel assembly, which was implemented using water for validating the pressure drop formulas in the JAEA sub-channel analysis code, ASFRE. The generation and demise of the vortex structures in the edge, corner, and interior sub-channels were periodically synchronized with the angular positions of the wire spacers. The axial and tangential flows in the edge and corner sub-channels are much stronger than those in the interior sub-channels. The vortex structures in the edge sub-channels have higher axial and tangential velocities than those in the corner sub-channels, interior sub-channels, and the wake region generated by wire spacers. The vortex structures in the edge sub-channels are a type of longitudinal vortex, and have a larger scale than the other sub-channels. The vortex structures in the corner sub-channels have lower axial and tangential velocities than those in the edge and interior sub-channels. The turbulence intensity in the sub-channels is remarkably dominated by the magnitude of the axial velocity. The vortex structures in the edge, corner, and interior sub-channels have a higher turbulence intensity and lower vorticity than the small-scale wakes near the wire spacers. The driving forces on the wire in the X-, Y-, and Z-directions are not only dependent on the axial velocity, but are also significantly dependent on the relative angular position between the wire spacer and rod, and the relative position between the wire spacer and duct wall.

Next generation of ventricular catheters for hydrocephalus based on parametric designs.

The flow pattern of the cerebrospinal fluid is probably the most important factor related to obstruction of ventricular catheters during the normal treatment of hydrocephalus. To better comprehend the flow pattern, we have carried out a parametric study via numerical models of ventricular catheters. In previous studies, the flow was studied under steady and, recently, in pulsatile boundary conditions by means of computational fluid dynamics (CFD) in three-dimensional catheter models. This study aimed to bring in prototype models of catheter CFD flow solutions as well to introduce the theory behind parametric development of ventricular catheters. A preceding study allowed deriving basic principles which lead to designs with improved flow patterns of ventricular catheters. The parameters chosen were the number of drainage segments, the distances between them, the number and diameter of the holes on each segment, as well as their relative angular position. CFD results of previously unreleased models of ventricular catheter flow solutions are presented in this study. Parametric development guided new designs with better flow distribution while lowering the shear stress of the catheters holes. High-resolution 3D printed catheter solutions of three models and basic benchmark testing are introduced as well. The next generation of catheter with homogeneous flow patterns based on parametric designs may represent a step forward for the treatment of hydrocephalus, by possibly broadening their lifespan.

Exact laser beam positioning for measurement of vegetation vitality

PurposeThe purpose of this paper is to present a novel application for a newly developed Technical Vision System (TVS), which uses a laser scanner and dynamic triangulation, to determine the vitality of agriculture vegetation. This vision system, installed on an unmanned aerial vehicle, shall measure the reflected laser energy and thereby determine the normalized differenced vegetation index.Design/methodology/approachThe newly developed TVS shall be installed on the front part of the unmanned aerial vehicle, to perform line-by-line scan in the vision system field-of-view. The TVS uses high-quality DC motors, instead of previously researched low-quality DC motors, to eliminate the existence of two mutually exclusive conditions, for exact positioning of a DC motor shaft. The use of high-quality DC motors reduces the positioning error after control.FindingsPresent paper emphasizes the exact laser beam positioning in the field-of-view of a TVS. By use of high-quality instead of low-quality DC motors, a significant reduced positioning time was achieved, maintaining the relative angular position error less than 1 per cent. Best results were achieved, by realizing a quasi-continuous control, using a high pulse-width modulated duty cycle resolution and a high execution frequency of the positioning algorithm.Originality/valueThe originality of present paper is represented by the novel application of the newly developed TVS in the field of agriculture. The vitality of vegetation shall be determined by measuring the reflected laser energy of a scanned agriculture zone. The paper’s main focus is on the exact laser beam positioning within the TVS field-of-view, using high-quality DC motors in closed-loop position control configuration.

Vibration behavior of a two-crack shaft in a rotor disc-bearing system

The vibration response characteristics of a rotor disc-bearing system with one and two cracks are analytically investigated using a modified harmonic balance method. The analytical model is formulated considering rigid-short bearing supports to study the effects of cracks’ characteristics such as depth, location and relative angular position on selected vibrational properties, namely, critical speeds, harmonic and super-harmonic components of the unbalance lateral response and the shaft center orbit. Each crack is initially described by a breathing function proposed by Mayes and Davies, which is subsequently modified as a softly-clipped cosine function to accurately describe saturation in breathing phenomenon. The response characteristics of the cracked shaft are also compared with those of the system with an intact shaft in order to identify potential measures for detecting cracks. The results show that the presence of a second crack emphasizes changes in the critical speeds of the rotor disc-bearing system, while relative angular position of the cracks influences the shaft center orbit. The validity of the proposed analytical model and the solution method is also investigated through simulations of a finite element model of the system.

Active vibration control of an oscillator with two translational degrees of freedom using centrifugal forces created by two eccentrically rotating masses

An active mass damper for vibration control of an oscillator with two translational degrees of freedom is presented along with the corresponding closed-loop control algorithm. The damper consists of two eccentrically rotating masses. In a preferred mode of operation, the masses rotate in opposite directions with a mostly constant angular velocity about a single axis. The resulting force is a harmonic control force. Its direction is determined by the relative angular position of the masses. In previous research, a similar control algorithm for vibration control of a single degree of freedom oscillator has been proven to be effective. In this paper, the control algorithm is augmented such that it can be applied to an oscillator with two translational degrees of freedom. Various state variables are introduced and a feedback control algorithm is developed. The presented algorithm ensures that the rotational motion of the masses is smooth and that the control force has the required orientation. The algorithm is verified experimentally with a test setup for the damping of free vibrations and numerically for stochastically forced vibrations. Finally, the device is compared with a conventional active mass damper. It is shown that the power demand and the energy consumption of the presented device are smaller than those of the conventional active mass damper.