Amplitude Angle Research Articles

Standing wave drift of hemispherical resonator with quality factor non-uniformity under a ring electrode excitation

Hemispherical Resonator Gyroscope (HRG) is a classical high precision Coriolis Vibration Gyroscope (CVG), which performs attitude estimation of carrier by detecting the precession of standing wave of resonator, thus, the drift of standing wave of resonator has a great influence on the output accuracy of gyroscope, where the quality factor non-uniformity of resonator is one of main error sources. Ring electrode is a classical excitation structure of HRG because the standing wave can precess freely under its excitation, which makes the gyroscope have more accurate scale factor, larger measurement range and better dynamic characteristics. In this paper, the equations of motion of an ideal resonator excited by a ring electrode are derived by the elastic thin shell theory and Lagrange mechanical principle, then the corresponding equivalent mechanical model is established. According to the “average method”, it can be seen that the ideal resonator excited by the ring electrode works in integral mode, and any position in the circumferential direction of resonator can be a working point, which means that the quality factor non-uniformity has a great effect on the drift of standing wave. Therefore, the equations of motion of resonator with quality factor non-uniformity under the ring electrode excitation are deduced by the equivalent mechanical model, and the drift model of standing wave is established by the “average method”, it can be found that both the amplitude of quality factor non-uniformity and angle between the “inherent damping axis” and antinode axis of standing wave can affect the drift rate of standing wave. Moreover, the drift model indicates that if the input angular rate does not reach the threshold, the precession angular rate of standing wave will appear “self-locking” phenomenon, that is, the gyroscope will lose the integral effect.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ БЕЗКОНТАКТНИХ МАГНІТО-ЕЛЕКТРИЧНИХ ДВИГУНІВ ЗВОРОТНО-ОБЕРТАЛЬНОГО РУХУ

The paper describes the structure and mathematical model of a specialized brushless magnetoelectric motor of return-rotary motion. The analysis of the parameters of the mathematical model is carried out and the methods of their experimental determination are described. Experimental frequency dependences of the rotor oscillations angle amplitude and the stator current effective value have been obtained. Based on the obtained parameters, the frequency characteristics of the motor were calculated and compared with the experimental dependences. Experimental oscillograms and calculated curves of stator voltages and currents are presented. References 7, figures 8.

FEATURES AND PRINCIPLES OF THE DEVELOPMENT OF BRUSHLESS MAGNETOELECTRIC SYSTEMS OF THE RETURN-ROTARY MOTION

The paper reviews the results of studies of brushless magnetoelectric systems of return-rotary motion, carried out for many years at the Electrodynamics Institute of the National Academy of Sciences of Ukraine. Structures of specialized brushless magnetoelectric motors with elastic magnetic coupling between the stator and the rotor are presented. An example of structural optimization of the motor is given. The electromechanical characteristics of the motors of the return-rotary motion are described and the indexes of their efficiency are proposed. An example of the formation of functional dependences for motor control in an open-loop system is given. Structures of the system for automatic control of the rotor oscillations angle amplitude and stator current limitation, as well as a system for vector control of the auxiliary winding current for active compensation of reactive alternating torque of the main rotor are presented. Examples of calculation of transient responses of the main parameters of the motor are given. Reference 11, figure 9.

A novel signal to image transformation and feature level fusion for multimodal emotion recognition.

Emotion is one of the most complex and difficult expression to be predicted. Nowadays, many recognition systems that use classification methods have focused on different types of emotion recognition problems. In this paper, we aimed to propose a multimodal fusion method between electroencephalography (EEG) and electrooculography (EOG) signals for emotion recognition. Therefore, before the feature extraction stage, we applied different angle-amplitude transformations to EEG-EOG signals. These transformations take arbitrary time domain signals and convert them two-dimensional images named as Angle-Amplitude Graph (AAG). Then, we extracted image-based features using a scale invariant feature transform method, fused these features originates basically fromEEG-EOG and lastly classified with support vector machines. To verify the validity of these proposed methods, we performed experiments on the multimodal DEAP dataset which is a benchmark dataset widely used for emotion analysis with physiological signals. In the experiments, we applied the proposed emotion recognition procedures on the arousal-valence dimensions. We achieved (91.53%) accuracy for the arousal space and (90.31%) for the valence space after fusion. Experimental results showed that the combination of AAG image features belonging to EEG-EOG signals in the baseline angle amplitude transformation approaches enhanced the classification performance on the DEAP dataset.

Flying With Damaged Wings: The Effect on Flight Capacity and Bio-Inspired Coping Strategies of a Flapping Wing Robot

Insects wings are subject to wear and tear from collisions and environmental disturbances during flight. They can tolerate both symmetrical and asymmetrical wing damages while maintaining flight capability to some extent. Drawing inspiration from nature's adaptation capabilities, we investigated the consequences of wing damage on a flapping wing micro air vehicle by quantifying the changes in wing kinematics, lift generation, control torque offset, and aerodynamic damping variations in flight tests with intact and damaged wings. For the proposed vehicle, the wing damage affected the lift generation significantly. Compared to the intact wings, the damaged ones result in increased stroke angle amplitude in order to compensate for lift loss and torque imbalance, which causes an increase in power consumption accordingly. Furthermore, asymmetric damages usually require a larger amount of additional control effort for flight stabilization compared to symmetric cases. In addition, aerodynamic damping varies as the wing areas change. All these aspects pose challenges in flight control. An adaptive controller is proposed to cope with the wing damage induced detrimental effects on flight capacity. Flight tests were conducted to validate the control performance. As a result, the robot can effectively overcome such challenges even in the case of a maximum unilateral lift loss of up to $\approx$ 22%. Such a result matches the performance of hovering hawkmoths, which can handle torque asymmetry up to 22.3 $\pm$ 7.8%. To the best of our knowledge, this is the first demonstration of FWMAVs to handle significant wing asymmetry in hover flight.

Validation of the Velocity Optimization for a Ropeway Passing over a Support

In this paper, we present a successful experimental validation of the velocity optimization for a cable car passing over a support. We apply the theoretical strategy developed in a previous work, refined by taking into account in a simple manner the hauling cable dynamics. The experiments at the ropeway Postal–Verano (South Tirol, Italy) have shown a significant reduction of the pendulum angle amplitude for both the descent and the ascending rides, as predicted from simulations. Furthermore, we measured a smoother progress of the torque at the driving engine during the vehicle support crossings.

Study of anti-swing control of ship cranes based on time delay feedback

2 tons 3 meters ship crane as the research object, establish the complete mathematical model of ship crane, and design the time-delay feedback control algorithm to eliminate payload swing on the basis of the built mathematical model. First, a high-precision potentiometer is used to measure the in-plane and out-of-plane oscillation of the payload. Measuring devices for the rotary angle and variation amplitude angle are created, and the anti-swing control hardware system is built by the sensing unit and the High-Speed Data Acquisition hardware system. Secondly, the control software on the VB platform is developed using the time-delay feedback algorithm. Experimentally study the effect of time-delayed feedback controller on payload swing elimination, and use induction method to get the optimal control parameters of the time-delayed feedback control algorithm. At last, the AMEsim-ADAMS co-simulation platform was built to evaluate the payload sway of the ship crane under simulated working conditions. The results show that: the hardware and software systems for anti-swing control built-in the paper can give the real-time and the exact payload swing angles. The method of adding time-delay feedback control signal to the slewing operation signal can achieve better anti-swing effects than the others. At the same time, the delayed feedback control algorithm still has a nice control effect in the case of virtual ship deck motion.

Effects of Modified Ultrafiltration on Thromboelastographic Profile after Pediatric Cardiac Surgery

Modified ultrafiltration (MUF) is still used after pediatric cardiopulmonary bypass (CPB) in some pediatric cardiac surgery centers to decrease transfusion requirements. Other potential benefits of MUF include clearance of inflammatory markers and improvement in myocardial function. Our hypothesis is that MUF will hemoconcentrate coagulation factors and improve thromboelastography (TEG) parameters after pediatric CPB. Patients younger than 6 months were prospectively enrolled over a year. TEG was carried out before MUF, after MUF, and after protamine administration. Paired t tests were conducted to compare values pre-MUF and post-MUF as well as post-MUF and post-protamine administration. Thirty patients were enrolled in the study, with 20 (67%) neonates in the cohort. Seven arterial switch operations and nine Norwood procedures were found to be performed among the cohort. Reaction time (R), angle (α), and maximum amplitude (MA) were significantly worse post-MUF compared with pre-MUF (p < .001). They improved significantly after protamine administration compared with post-MUF (p < .001). The amount of fluid removal was significantly associated with a worse post-MUF R, angle, and MA and worse post-protamine administration, angle, and MA but with no effect on post-protamine R. MUF caused worsening of TEG parameters that is reversed by protamine administration.

Effects of Modified Ultrafiltration on Thromboelastographic Profile after Pediatric Cardiac Surgery.

Modified ultrafiltration (MUF) is still used after pediatric cardiopulmonary bypass (CPB) in some pediatric cardiac surgery centers to decrease transfusion requirements. Other potential benefits of MUF include clearance of inflammatory markers and improvement in myocardial function. Our hypothesis is that MUF will hemoconcentrate coagulation factors and improve thromboelastography (TEG) parameters after pediatric CPB. Patients younger than 6 months were prospectively enrolled over a year. TEG was carried out before MUF, after MUF, and after protamine administration. Paired t tests were conducted to compare values pre-MUF and post-MUF as well as post-MUF and post-protamine administration. Thirty patients were enrolled in the study, with 20 (67%) neonates in the cohort. Seven arterial switch operations and nine Norwood procedures were found to be performed among the cohort. Reaction time (R), angle (α), and maximum amplitude (MA) were significantly worse post-MUF compared with pre-MUF (p < .001). They improved significantly after protamine administration compared with post-MUF (p < .001). The amount of fluid removal was significantly associated with a worse post-MUF R, angle, and MA and worse post-protamine administration, angle, and MA but with no effect on post-protamine R. MUF caused worsening of TEG parameters that is reversed by protamine administration.

Trailing-edge boundary layer characteristics of a pitching airfoil at a low Reynolds number

The periodic variation of the flow pattern and the boundary layer characteristics near the trailing edge of a pitching NACA (National Advisory Committee for Aeronautics) 0012 airfoil are examined experimentally in this study. The mean pitching angle and pitching amplitude were 0° and 7.5°, respectively, and the reduced frequency varied from 0.094 to 0.157. Static cases with various angles of attack were tested for reference. All the tests were conducted at a low Reynolds number of 66000. Particle image velocimetry was used as the primary measurement for flow visualization and boundary layer analysis. The periodic development of the flow pattern close to the trailing edge within one pitching cycle was monitored. The instantaneous flow patterns acquired at certain phase angles are compared with the static cases, demonstrating the influences of the pitching motion, including the lag effect on the boundary layer. A vortex street is observed as the airfoil achieves certain pitching angles, leading to the largest boundary layer displacement thickness at the corresponding side. As the pitching angle increases, transition of the boundary layer at the trailing edge occurs at a higher incidence compared with the static cases. Increasing the pitching frequency would lead to the decrease in the vortex structure strength and delayed boundary layer transition near the trailing edge.

Numerical study on energy-extraction performance of a flapping hydrofoil with a trailing-edge flap

Unlike traditional rotary turbines, the flapping hydrofoil energy harvesters can capture kinetic energy from flowing fluids by undergoing combined heaving and pitching motions. In this paper, a new type of flapping hydrofoil energy harvester whose trailing-edge can deflect upwards during downstroke flapping cycle and downwards during the upstroke has been proposed. The energy-extraction performance of the proposed flapping hydrofoil then was investigated by numerical simulations based on the two-dimensional incompressible Navier-Stokes equations at a Reynolds number of 4.7×105. Influences of various characteristic parameters including deflection angle amplitude, flap length, gap width on the energy-extraction efficiency of the proposed flapping hydrofoil were analyzed. The present results show that the heaving force is the most dominant contributor to total power output of the flapping hydrofoil and it can be greatly increased due to the deflection of TEF. It is also found that there exist optimal deflection angle amplitude and TEF length which can significantly improve the energy-extraction efficiency at moderate to high values of reduced frequency. Moreover, the smaller the gap width, the higher the efficiency can be achieved. As a result, the maximum energy-extraction efficiency of the flapping hydrofoil with optimized TEF can be increased by approximately 23.5% compared to the conventional flapping hydrofoil-based current energy harvester.

Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

We investigate the onset of temporal dynamics of a fluidic oscillator (FO) in the laminar regime at very low Reynolds number (Re=Uhi/ν, where U and hi are the velocity and channel height at inlet, and ν is the kinematic viscosity of the fluid). Both two- and spanwise-periodic-three-dimensional simulations are performed using high-order spectral element methods to characterise the flow inside the FO cavity and the outcoming jet. While the flow remains steady and symmetric for sufficiently low Re, the two-dimensional FO undergoes a symmetry-breaking Hopf bifurcation at ReH2=75.7 that results in a space-time symmetric periodic solution. The remnant space-time symmetry is later broken in a pitchfork bifurcation of limit cycles at ReP2=294.2. Taking three-dimensionality into consideration results in an early spanwise-invariance disruption at about Re3≃68 of wavelength 13hi that retards the onset of the oscillation to ReH3=82.1. This effect is little representative of actual FO implementations, which are typically much narrower than the wavelength of the spanwise instability observed at these low Re. Contrary to what happens with FOs in the turbulent oscillatory regime, the oscillation frequency of the output jet in the laminar regime is found to decrease with Re. The mechanism that drives the oscillation, however, remains the same: as the high speed flow inside the cavity attaches to one of the internal walls through the Coandă effect, the feedback channels divert part of the momentum back, which pushes the incoming flow against the opposite wall. The alternate deviation of the flow inside the cavity to one or the other side results in the periodic flipping of the output jet. The pressure contribution to net momentum at the end of the feedback channels is found to be double that of the advective momentum flux at the early time-periodic regime but both become comparable as Re is increased. The jet sweeping angle amplitude is more pronounced for the two-dimensional FO as compared to three-dimensional at a fixed given Re, the Coandă effect being only partially fulfilled in the latter case. In both cases the sweep amplitude increases with Re. The instability of the output jet, which becomes slightly chaotic already at very low Re, is responsible for triggering the cavity instability that drives the oscillation slightly earlier than it would, should outside noise be suppressed altogether.

An Online Estimation Method for Both Stator Inductance and Rotor Flux Linkage of SPMSM Without Dead-Time Influence

It is essential to estimate stator inductance and rotor flux linkage online for fault diagnosis and high-performance control of surface-mounted permanent magnet synchronous machine (SPMSM). Current injection method is a popular way to estimate the two parameters. However, the dead-time influence of voltage-source-inverter (VSI) and the stator inductance variation caused by injected current could not guarantee the converge of the estimation. To solve the above two problems, a method of injecting square-wave angle for online parameter estimation is proposed in this paper. Firstly, the theory of eliminating dead-time influence with and without square-wave angle injection is analysed. Next, the least square algorithm is adopted to estimate stator inductance without injection. Then the rotor flux linkage is estimated with injecting square-wave angle. The saturation effect on estimation is also analyzed and both parameters are estimated without acquiring any nominal values. At last, the appropriate amplitude and frequency of square-wave angle are determined by the parameter error and convergence analysis. The proposed method is evaluated with simulation and extensive experiments under various speed and load conditions. It is noteworthy that not less than two parameters are estimated without the dead-time influence and the injection will not cause inductance variation, which is different from the previous work.

Analysis on dynamic eccentricity effect and torsional performance of steel reinforced concrete frame with special-shaped column

Based on the seismic simulation shaking table test of steel reinforced concrete frame model with special-shaped column, the lateral-torsional vibration response, dynamic eccentricity effect and nonlinear torsion response law of the model structure are studied. The results show that, under the action of three-way earthquake, the Y-direction and X-direction horizontal torsion coupling phenomena occur in the high-order vibration mode of the model structure, and the accidental eccentric torsion has a light influence on the seismic performance of the special-shaped column structure which does not exceed the height limit. The nonlinear torsion analysis shows that the inter-storey displacement angle of the model structure is affected by floor position, eccentricity and ground motion intensity. As the eccentricity and seismic intensity increases, the inter-storey torsion Angle of the model structure increases constantly. In case the relative eccentricity is less than or equal to 0.5 and the peak acceleration is less than or equal to 0.62g, then the amplitude of the inter-storey torsion Angle of the model increases slightly; In case the relative eccentricity is more than 0.5, then the lateral-torsional coupled effect of earthquake response of the structure is obvious, and the influence of eccentricity on torsion effect of the model structure is more obvious. The results show that steel reinforced concrete frame with special-shaped column has good ductility and torsion resistance.

A general process model for unanticipated state recognition of a telescope drive system

Abstract This paper presents a three-layer general process model for unanticipated state recognition in a telescope drive system, consisting of an anticipated fault diagnosis layer, an unanticipated normal state isolation layer, and an unanticipated fault state recognition layer. It is proposed for the first time to subdivide the unanticipated state into an unanticipated normal state and an unanticipated fault state in this paper, and to study their theories separately. Unanticipated normal state isolation rules based on angle deviation and amplitude deviation are established, as are unanticipated fault state recognition rules based on angle deviation and deviation contribution factor. Finally, normal operation data of the Antarctic Survey Telescope (AST3-3) combined with fault implantation was used to verify the validity of the model. The results show that the method can effectively carry out isolation of the unanticipated normal state and identification of the unanticipated fault state.

CO2 artificial pneumothorax on coagulation and fibrinolysis during thoracoscopic esophagectomy.

Background:CO2 artificial pneumothorax creates a sufficient operative field for thoracoscopic esophagectomy. However, it has potential complications and continuous CO2 insufflation may impede coagulation and fibrinolysis. We sought to compare the effects of CO2 artificial pneumothorax on perioperative coagulation and fibrinolysis during thoracoscopic esophagectomy.Methods:We investigated patients who underwent thoracoscopic esophagectomy with (group P, n = 24) or without CO2 artificial pneumothorax (group N, n = 24). The following parameters of coagulation–fibrinolysis function: intraoperative bleeding volume; serum levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1), thromboelastogram (TEG), D-Dimer; and arterial blood gas levels were compared with two groups.Results:Group P showed higher levels of PaCO2, reaction time (R) value and kinetics (K) value, but significantly lower pH value, alpha (α) angle and Maximum Amplitude (MA) value at 60 minutes after the initiation of CO2 artificial pneumothorax than group N ((P < .05, all). The t-PA level after CO2 insufflation for 60 minutes was significantly higher in group P than in group N (P < .05), but preoperative levels were gradually restored on cessation of CO2 insufflation for 30 min (P > .05). There was no significant difference in D-dimer.Conclusion:CO2 artificial pneumothorax during thoracoscopic esophagectomy had a substantial impact on coagulation and fibrinolysis, inducing significant derangements in pH and PaCO2.Trial registration:The study was registered at the Chinese clinical trial registry (ChiCTR1800019004)

Vehicle coupled bifurcation analysis of steering angle and driving torque

The mechanism of vehicle dynamics steering bifurcation has almost been confirmed. But the present steering bifurcation mechanism cannot explain the bifurcation phenomena caused by the driving torque. As a result, the vehicle coupled bifurcation analysis of the steering angle and driving torque has not been studied. Based on the five degrees of freedom (5DOF) vehicle system dynamics model with driving torque involved, the vehicle dynamics equilibriums under different driving torque and driving mode were searched by a hybrid method in this paper. The hybrid method combined the real-coded Genetic Algorithm with Quasi-Newton gradient method. According to the definition of static bifurcation of nonlinear systems, the equilibrium bifurcation of 5DOF vehicle system was confirmed. Then, the 5DOF vehicle system model was transformed into autonomous equation with the front wheel steering angle as intermediate variable. From the two aspects of constant steering angle amplitude and constant driving torque, the bifurcation diagrams of different driving mode were calculated. The vehicle coupled bifurcation characteristics of steering angle and driving torque were analyzed. The results show that the values of the driving torque will directly affect the bifurcation characteristics of vehicle dynamics system. The coupled feature of the front wheel steering angle and driving torque effect on vehicle bifurcation is obvious.

Effect of the torsional vibration depending on the number of cylinders in reciprocating engines

This paper is aimed to explore the effect of increasing the number of pistons on the torsional vibration analysis of inline reciprocating machines with simplifications of equivalent masses to the connecting rod and crankshaft. A mathematical model of a mechanism of two degrees of dynamic freedom has been used to develop the equations of motion of the rotating and reciprocating parts of the single and multi-cylinder engine. Different configurations of single-cylinder and multi-cylinder engines are considered with the number of cylinders ranging from 1 to 6. The model of the crankshaft is established with the use of Lagrange's equations valid for a single and multi-pistons engine. This work shows the relation between the angular displacement of the crank angle and the twist angle of the crankshaft concerning three different damping coefficients. The maximum amplitude occurred with an engine of 2-cylinders while the minimum amplitude occurred with the single-cylinder engine. The twist angle does not depend upon the increasing number of the pistons. The torsional vibrations of the crankshaft by using 3 or more cylinders are significant in magnitude with values near to unity. Besides, the greatest amplitude of twist angle with odd cylinders and the reduction in the torsional vibration may be obtained for engine designs with even cylinders.

Effect of viscosity on the avalanche dynamics and flow transition of wet granular matter

The dynamic behaviour of granular flows is important in geo-mechanics and industrial applications, yet poorly understood. We studied the effects of liquid viscosity and particle size on the dynamics of wet granular material flowing in a slowly rotating drum, in order to detect the transition from the avalanching to the continuous flow regime. A discrete element method (DEM) model, in which contact forces and cohesive forces were considered, was employed to simulate this flow behaviour. The model was validated experimentally, using glass beads in a wooden drum and water–glycerol mixtures to tune the liquid viscosity. The DEM simulations showed comparable results to the experiments in terms of average slope angle and avalanche amplitude. We observed that the avalanche amplitude, flow layer velocity and granular temperature decrease as the liquid viscosity increases. This effect is more pronounced for smaller sized particles. The increase in viscous forces causes the flowing particles to behave as a bulk, pushing the free surface towards a convex shape. In addition, avalanches become less pronounced and the granular flow transitions from the avalanching regime to the continuous regime. The avalanching flow regime is marked by intermittent rigid body movement of the particulate bed and near-zero drops in the granular temperature, while no rigid body movement of the bed occurs in the continuous flow regime. We identified the avalanching-continuous flow transition region as a function of a dimensionless granular Galileo number.

Предотвращение возможности возникновения резонансных режимов движения для низковысотных спутников класса CUBESAT

Resonant modes of motion, manifested as a significant increase in the oscillation amplitude of the spatial angle of attack, can result in the failure of the CubeSat mission. This paper is concerned with the study of the resonant motion modes of aerodynamically stabilized CubeSat nanosatellites in low circular orbits with small inertia and mass asymmetry. In contrast to axisymmetric bodies of rotation, resonances in CubeSat nanosatellites can be caused not only by small asymmetry, but they also arise due to the form factor of the rectangular parallelepiped. Formulas have been obtained to determine the critical values of the nanosatellite longitudinal angular velocity at which the conditions for the emergence of resonant motion modes are fulfilled. An approach is proposed to prevent possible resonances for CubeSat nanosatellites.