Rotor Radius Research Articles

Performance Evaluation of Enhanced Slotted AlohaCA Protocol on Planet Mars

The launch and successful operation of the Mars Cube One (MarCO) CubeSat in May 2018 heralded a new era in solar system exploration and the setup of the first Interplanetary CubeSat Network (ICN). The success of this mission could give rise of an Interplanetary DTN–Based CubeSat network, in which the CubeSat Nanosatellite, as DTN custody node, plays the role of Data Mule to collect data from rovers on a planet such as Mars. In order to maximize the contact volume which is the amount of transmitting data from rovers to the CubeSat during its pass over their service zone, we will need to design an efficient MAC protocol. This research focuses on the simulation and evaluation of the performance of the Slotted AlohaCA MAC Protocol on the planet Mars compared to Earth taking into account the different properties between the two planets, such as radius, mass and speed of rotation of the Nanosatellite in its orbital at the same altitude. We have conducted many simulations using the NS2 simulator that takes into consideration the spatial dynamic behavior of the Nanosatellite, which is dependent on motion of the Nanosatellite in its orbit. Three appropriate performance measures are evaluated: Throughput, stability and power consumption. The obtained simulation results on the planet Mars show an improvement on performance of the Slotted AlohaCA on the planet Mars compared to Earth.

Three-Dimensional Reachability Set For a Dubins Car: Reduction of the General Case of Rotation Constraints to the Canonical Case

In mathematical control theory, a Dubins car is a nonlinear motion model described by differential relations, in which the scalar control determines the instantaneous angular rate of rotation. The value of the linear velocity is assumed to be constant. The phase vector of the system is three-dimensional. It includes two coordinates of the geometric position and one coordinate having the meaning of the angle of inclination of the velocity vector. This model is popular and is used in various control tasks related to the motion of an aircraft in a horizontal plane, with a simplified description of the motion of a car, small surface and underwater vehicles, etc. Scalar control can be constrained either by a symmetric constraint (when the minimum rotation radii to the left and right are the same) or asymmetric constraint (when rotation is possible in both directions, but the minimum rotation radii are not the same). Usually, problems with symmetric and asymmetric constraints are considered separately. It is shown that when constructing the reachability set at the moment, the case of an asymmetric constraint can be reduced to a symmetric case.

듀얼 스위블 휠 기반의 전 방향 이동 로봇의 개발 및 그 주행성능 시뮬레이션

Omnidirectional driving wheel mechanisms include omni-wheels, mecanum wheels, swivel wheels, and ball wheels. However, this driving wheel technology encounters challenges such as slip, load distribution, floor surface compatibility, and contact friction. In this paper, a dual swivel wheel-based mobile robot design for omnidirectional motion is presented. By using the double-wheel structure, the torque required for each module can be divided into two parts. In addition, the low contact friction with the floor surface enables easy changes in the direction during rotation. To design the mechanics of the dual swivel wheel-based mobile robot and verify its driving performance, a robotics simulation environment was constructed using the Unity engine and ROS2. Through simulations, omnidirectional driving performance, steering precision, minimum radius of rotation, and positional precision were studied.

Micromotion Feature Extraction with VEMW Radar Based on Rotational Doppler Effect

Micro-Doppler (m-D) analysis is the most effective mechanism for detecting rotating targets or components; however, it fails when the target rotation plane is perpendicular to the radar line of sight (LOS). The vortex electromagnetic wave (VEMW) provides a unconventional structure of wavefront phase modulation on the cross-plane of the radar LOS, on which the radial m-D vanishes while the rotational Doppler (RD) appears. In the absence of the position of rotation center, this paper focuses on the micromotion parameters estimation based on RD effect for rotating target, and then proposes an estimation procedure, referred to as the two-step method. The micromotion parameters of the rotating target include the rotation attitude, the rotation radius and the position of the rotation center while the latter is coupled to the former two. Firstly, the micromotion parameters are roughly estimated based on the RD curve parameters obtained from the time-frequency (TF) spectrum of the received signal. Secondly, the maximum likelihood estimation (MLE) is used to accurately estimate the micromotion parameters. In addition, the Cramér–Rao bound (CRB) of parameter estimation is derived. The simulation studies the influencing factors of estimation performance and verifies that the proposed estimation method can provide excellent estimation accuracy of the micromotion parameters.

Phase-Resolved Flowfield Measurements of a Coaxial Counter-Rotating Rotor in Hover

The flowfield of a coaxial counter-rotating rotor in hover was measured using particle image velocimetry. The goal of the measurements was to investigate the flow features of coaxial rotors, including interaction between the rotors, and to measure inflow over the rotor radius and azimuth. The phase-resolved measurements were performed at several azimuthal index angles behind the rotor blades, with 500 instantaneous flow realizations per azimuth. Axial velocity profiles extracted from the phase-averaged flowfields exhibited the effect of bound circulation associated with blade passage, the trailed vortex sheet, and the effect of the blade tip vortex. Tip vortex characteristics were extracted from the measurements and were shown to compare well with semi-empirical models in most cases. The measured inflow was captured well by blade element momentum theory when the mutually induced velocities were accounted for. The lower rotor was found to behave more like an isolated single rotor, whereas tip vortices from the upper rotor convected faster radially inward and downstream than the lower rotor tip vortices. Upper and lower rotor tip vortices exhibited similar core radii ranging from 12 to 18% of the rotor blade chord, and they grew at a similar rate. However, this vortex growth rate was different from that of an isolated single rotor.

Research on Optimization of Profile Parameters in Screw Compressor Based on BP Neural Network and Genetic Algorithm

In order to accurately calculate the geometric characteristics of the twin-screw compressor and obtain the optimal profile parameters, a calculation method for the geometric characteristics of twin-screw compressors was proposed to simplify the profile parameter design in this paper. In this method, the database of geometric characteristics is established by back-propagation (BP) neural network, and the genetic algorithm is used to find the optimal profile design parameters. The effects of training methods and hidden layers on the calculation accuracy of neural network are discussed. The effects of profile parameters, including inner radius of the male rotor, protection angle, radius of the elliptic arc, outer radius of the female rotor on the comprehensive evaluation value composed of length of the contact line, blow hole area and area utilization rate, are analyzed. The results show that the time consumed for the database established by BP neural network is 92.8% shorter than that of the traditional method and the error is within 1.5% of the traditional method. Based on the genetic algorithm, compared with the original profile, the blow hole area of the screw compressor profile optimized by genetic algorithm is reduced by 54.8%, the length of contact line is increased by 1.57% and the area utilization rate is increased by 0.32%. The CFD numerical model is used to verify the optimization method, and it can be observed that the leakage through the blow hole of the optimized model is reduced, which makes the average mass flow rate increase by 5.2%, indicating the effectiveness of the rotor profile parameter optimization method.

Aerodynamic analysis on unsteady characteristics of a ducted fan hovering in ceiling effect

Ducted fans have been widely used in unmanned aerial vehicles (UAVs) for various operations due to the high efficiency, low noise and high safety. Proximity effects caused by the confined environment, including the ceiling effect (CE), bring significant interference to the aerodynamic performance of ducted fans, which serves as a main challenge to stability. In this study, the computational fluid dynamic simulation with the sliding mesh technique and the Unsteady Reynolds Averaged Navier-Stokes (URANS) method is conducted to evaluate the ceiling effect. Time-averaged simulation results show that the ceiling effect results in the increase of both rotor thrust and duct thrust. Transient simulation results show that there is a critical distance of 0.4 rotor radius. The ceiling effect leads to little fluctuation in thrust for distances greater than 0.4 rotor radius, but substantial unsteadiness in the flow field for distances less than 0.4 rotor radius. The unsteady movement of vortex structures results in thrust fluctuations with frequencies typically lower than the blade passing frequency of 200 Hz. The fluctuation accounts for up to 40% of the total thrust. The results are essential to the flight controller design and UAV path planning for enhancement of flight stability in ceiling effect.

Numerical investigation on unsteady characteristics of ducted fans in ground effect

Ducted fans are widely used in various applications of Unmanned Aerial Vehicles (UAVs) due to the high efficiency, low noise and high safety. The unsteady characteristics of ducted fans flying near the ground are significant, which may bring stability problems. In this paper, the sliding mesh technology is applied and the Unsteady Reynolds Averaged Navier-Stokes (URANS) method is adopted to evaluate the influence of ground on the aerodynamic performance of ducted fans. The time-averaged results show that the ground leads to the decrease of duct thrust, the increase of rotor thrust and the decrease of total thrust. The transient results show that there exist small-scale stall cells with circumferential movements in ground effect. The stall cells start to appear at the blade root when the height is 0.8 rotor radius distance, and arise at both the blade root and tip when the height drops to 0.2. It is found that the unsteady cells rotate between blade passages with an approximate relative speed of 30%-80% of the fan speed, and lead to thrust fluctuations up to 37% of the total thrust. The results are essential to the flight control design of the ducted fan flying vehicle, to ensure its stability in ground effect.

Parameter Combination Optimization of the Lateral Straw Clearing and Throwing Knife Based on Discrete Element Simulation

In order to explore the laws of corn straw lateral moving and throwing, it is necessary to identify the main factors that restrict improvements in the quality of straw clearing and reductions in power consumption and then optimize the knife parameter combinations; in this paper, the kinematic analysis of single-stage lateral moving and throwing of corn straw was carried out, and the mathematical model for the collision process between the knife and straw is established. Key factors affecting the lateral moving and throwing efficiency of straw were determined according to the model analysis. A parameter combination optimization test was conducted with three-factor and five-level quadratic regression orthogonal rotation center combination test methods and discrete element virtual simulation, taking into account the edge angle of cutting, the rotation radius of the knife, and the rotation speed of the knife roller as test factors and the straw clearing rate and power consumption as performance evaluation indexes. The test results showed that at a travel speed of 7.2 km/h when the edge angle of cutting was 65°, the rotation radius of the knife was 420 mm, and the rotation speed of the knife roller was 538~600 rpm, the straw clearing rate was ≥85%, and power consumption was ≤1.5 kW. The field test was carried out to verify the optimized results, and the test results showed that the test values of the performance evaluation indexes were all in the ranges of the optimized interval. These research results lay down the foundation for the design of lateral straw clearing and throwing knives.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Biomechanical Comparison of Two Surgical Repair Techniques of the Distal Biceps Tendon

This study aimed to characterize the relationship between the distal biceps tendon force and the supination and flexion rotations during the initiation phase and to compare the functional efficiency of anatomic versus nonanatomic repairs. Seven matched pairs of fresh-frozen cadaver arms were dissected to expose the humerus and elbow while preserving the biceps brachii, elbow joint capsule, and distal radioulnar soft tissue complex. For each pair, the distal biceps tendon was severed with a scalpel and then repaired with bone tunnels placed at either the anterior (anatomic) or the posterior (nonanatomic) aspect of the bicipital tuberosity on the proximal radius. A supination test with 90° of elbow flexion and an unconstrained flexion test were conducted on a customized loading frame. The biceps tension was applied incrementally at 200 g per step, whereas the radius rotation was tracked with a 3-dimensional motion analysis system. The tendon force needed to produce a degree of supination or flexion was derived as the regression slope of the tendon force-radial rotation plots. A two-tailed paired t test was performed to compare the difference between the anatomic repair and the nonanatomic repair cadavers. Significantly greater tendon force was required to initiate the first 10° of supination with the elbow in flexion for the nonanatomic group compared with the anatomic group (1.04 ± 0.44 N/degree vs 0.68 ± 0.17 N/degree, P= .02). The average nonanatomic to anatomic ratio was 149% ± 38%. No difference existed between the two groups in the mean tendon force needed to produce the degree of flexion. Our results show that anatomic repair is more efficient in producing supination than nonanatomic repair, but only when the elbow is in 90° of flexion. When the elbow joint is not constrained, the nonanatomic supination efficiency improved, and the difference between the techniques was not significant. The present study added to the body of evidence in comparing anatomic versus nonanatomic repair of the distal biceps tendon and serves as a foundation for future biomechanical and clinical studies in this topic. Given no difference when the elbow joint was not constrained, one could argue that surgeon comfort and preference could guide which technique to use when addressing the distal biceps tendon tears. More studies will be needed to clearly define whether there will be a clinical difference between the two techniques.

Spectrum characteristics and temperature measurement error of FBG sensor based on rotor temperature monitoring system

For real-time temperature monitoring of a generator or electric motor rotor, the effects of rotation on the reflection spectrum of a polyimide-coated Fibre Bragg Grating (FBG) were analyzed using formulas. The measurement error resulting from the low-speed operation was evaluated, combined with the finite element method. Secondly, the key design of the FBG sensors and the mating part of the fiber optic rotary joint (FORJ) were investigated. The temperature of a rotating shaft was monitored to test the reliability of the measurement system. With a resolution of 0.1℃, the system was able to achieve an error of 0.5℃ over a range of 30-180℃. Finally, the critical conditions for the application of polyimide-coated and metal-coated FBGs were discussed. The results show that the variation of the center wavelength is more sensitive to the radius of the small-sized rotor, and the rotation speed of the large-sized rotor. It is at higher speeds that the thickness of the coating has a more pronounced effect on error, demonstrating that the accuracy of FBGs used in high-speed rotors could be rapidly improved by reducing the thickness of the metal coating. The reported results provide a basis for the thermal monitoring performance of FBG sensors during rotation.

The quantum nature of the weak interaction

From the fundamental noνα = 1 formula, the up quark was identified as an exchange particle based on its mass, which implies that the particle is newly formed and not, as the current theory says, transformed from the d quark through ß-decay. The quark rotation most possibly imparts a fast oscillatory rotation to the quarks (weak interaction), which in turn imparts the rotation to the nucleon. The transferred rotation is partially decoupled from the quarks, which means that the transferred rotation velocity does not depend on the oscillation velocity of the quark structure, but on its radius r, where r is the virtual quantized radius of the quark rotation or quark oscillation. In case of the week interaction, when the quarks begin to oscillate, the rotation is partially decoupled from the individual quarks and transferred to the triple quark structure in the transverse direction to the main axis of rotation. From this, a unified formula for the gravitation and EM forces could be deduced.

Quantitative Analysis of Deformity in Digital Model of Congenital Radioulnar Synostosis

The deformity of congenital radioulnar synostosis is quite complicated and difficult. This study aims to find out the related factors of the "forearm rotation angle" (FR) which relate to the severity of congenital radioulnar synostosis (CRUS), and try to quantify the internal relations of each deformity and help to understand the reconstruction method in surgery treatment of this disease. This study is case series research. We established 48 digital three-dimensional forearm bone models of 48 patients with congenital radioulnar synostosis classified as Cleary and Omer type 3. All the patients were treated at our institution from January 2010 to June 2016. In total, 10 independent deformities (the rotation angle of forearm; the internal rotation, radial, and dorsal angulation of radius and ulna; the relative length of osseous fusion at PRUJ; the relative dislocation distance of distal radioulnar joint; the relative area of proximal radial epiphysis) involved in the CRUS complex deformity were measured. Pearson correlation analysis for each deformity which was mentioned above was performed, and multivariate linear regression analysis was also performed with FR as the dependent variable and the other deformities as the influential factors. The "dorsal angle of radius" (DAR, 21.69° ± 21.55°) had the strongest correlation with the FR (79.72° ± 40.39°), the Pearson correlation coefficient was 0.601 (p < 0.01), the internal rotation angle of the radius (IRAR, 82.69° ± 54.98°) had a moderate correlation with FR, the Pearson correlation coefficient was 0.552 (p < 0.01). A forearm deformity equation was established: FR=35.896 + 0.271 DAR + 0.989 IRAR. The dorsal angulation deformity of radius may be the most important deformity that effects the severity of CRUS and should be correct in the first place during reconstruction operation.

Torque Assessment of Multiphase AFPM Machines With Experimental Validation for YASA Topology

This work presents a theoretical and experimental study on the electromagnetic torque of multiphase axial-flux permanent-magnet (AFPM) machines. Initially, a torque equation&#x00A0;is obtained through four different methods. The first method follows the definition of electromagnetic power, the second uses the magnetic shear stress, the third is based on the concept of co-energy, and the fourth applies the principle of Lorentz force. Although these methods are based on different assumptions, they lead to the same generalized torque equation, which depends on four parameters: i) the fundamental air gap induction; ii) the electrical loading defined for an arbitrary rotor radius; iii) the ratio of inner and outer rotor radius; iv) the cubic power of the outer rotor diameter. The torque equation&#x00A0;is then validated using finite element (FE) analyses and experimental results obtained with a 32-pole/30-slot yokeless and segmented armature (YASA) machine. For this machine, the coils can be connected according to different arrangements so that the phase number can be chosen as three, five, or fifteen. The results show that the torque equation&#x00A0;derived here provides sufficient accuracy in practical cases and that it can be applied to machines with phase numbers higher than three.

Rheological Performance of High-Temperature-Resistant, Salt-Resistant Fracturing Fluid Gel Based on Organic-Zirconium-Crosslinked HPAM

Development of low-cost, high-temperature-resistant and salt-resistant fracturing fluids is a hot and difficult issue in reservoir fluids modification. In this study, an organic zirconium crosslinker that was synthesized and crosslinked with partially hydrolyzed polyacrylamide (HPAM) was employed as a cost-effective polymer thickener to synthesize a high-temperature-resistant and salt-resistant fracturing fluid. The rheological properties of HPAM in tap water solutions and 2 × 104 mg/L salt solutions were analyzed. The results demonstrated that addition of salt reduced viscosity and viscoelasticity of HPAM solutions. Molecular dynamics (MD) simulation results indicated that, due to electrostatic interaction, the carboxylate ions of HPAM formed an ionic bridge with metal cations, curling the conformation, decreasing the radius of rotation and thus decreasing viscosity. However, optimizing fracturing fluids formulation can mitigate the detrimental effects of salt on HPAM. The rheological characteristics of the HPAM fracturing fluid crosslinking process were analyzed and a crosslinking rheological kinetic equation was established under small-amplitude oscillatory shear (SAOS) test. The results of a large-amplitude oscillation shear (LAOS) test indicate that the heating effect on crosslinking is stronger than the shear effect on crosslinking. High-temperature-resistant and shear-resistant experiments demonstrated good performance of fracturing fluids of tap water and salt solution at 200 °C and 180 °C.

A comprehensive theoretical model for the centrifugal effect of nonlinear beam-type piezoelectrical energy harvesters in rotational motions

Currently, beam-type piezoelectric energy harvesters (PEHs) are being widely studied to realize rotational energy harvesting with high-efficiency performance. However, few theoretical models completely reveal the mechanism of the centrifugal effect, which results from the centrifugal force acting on the tip mass of beam-type PEHs. To fill in this research gap, a theoretical model has been established to describe its dynamic behaviors in this paper, and also account for the impacts of the installation angle and the rotational radius on the centrifugal effect. According to the proposed theoretical model, influences of the centrifugal force on dynamic characteristics and power generations are explored. Theoretical results demonstrate that the installation angle has a significant influence on components of the centrifugal force. Namely, the axial component can stiffen or soften the piezoelectric beam and the transverse component can be regarded as an excitation force, influencing the dynamic behaviors of beam-type PEHs. In addition, experiments of an asymmetric beam-type PEH with different installation angles are performed to validate the effect of the centrifugal effect and the magnetic force on its performance. Experimental results demonstrate that adjusting the installation angle to realize different centrifugal effects can change the effective frequency range and also be beneficial for power generation. Additionally, the asymmetric tri-stability due to the magnetic force can reduce the potential barrier to increase the effective frequency bandwidth. Overall, this paper reveals the mechanism of the centrifugal effect, and further provides theoretical insights into high-efficiency design and optimizations for beam-type PEHs in rotational motions.

Design and Analysis of a Novel 2-DOF Rotation–Translation Precision Positioning Stage

This paper presents the design, modeling, simulation, and experimental testing of a novel 2-DOF precision micro-positioning stage. A compact parallel structure is proposed and the rotation stroke of the stage is improved by reducing the rotation radius. Compared with other positioning stages, the developed stage has the advantage of large rotation stroke, compact structure, and high resonant frequency, and it can realize various positioning functions with fewer piezoelectric actuators. The simplified flexibility equation of the composite bridge mechanism was obtained through the equivalent replacement of the composite hinge, and then the transmission ratio and input stiffness analysis model of the stage are further established. Then, the simulation and experiment verify the accuracy of the model. The significant size parameters of the stage are determined according to the sensitivity analysis and verified by FEA. To decouple the rotation and translation, we establish the scale factor. The experimental results reveal that the workspace of the stage is 22.90 mrad × 95.03 μm. The step response time is 80 ms and the rotation resolution is 5 μrad under open-loop control.

Electrically Tunable Gyrohelitrons with Crossed Fields

The generation frequency is ω ≈ k ω н in classical gyrotrons, where ω н = е B 0 / m is the electron cyclotron rotation frequency in a uniform longitudinal magnetic field with induction B 0 , e is the electron charge, m is the electron mass, k = 1, 2, 3… is the cyclotron frequency working harmonic number. Thus, the generation frequency ω being tuned is possible only by changing B 0 . This way is very inconvenient. It’s necessary a solenoid additional (control) winding. That difficulty can be eliminated in gyrotrons with crossed fields - electric 0 and magnetic 0 , here 0 ⊥ 0 . The frequency can be tuned by changing E 0 . This possibility can be realized at least two ways: a gyrotron based on a coaxial resonator with radial field E 0 ; a four-mirror gyrotron on traveling Т -waves with transverse in respect the traveling wave direction to uniform crossed fields – electric 0 and magnetic 0 . The single-screw electron flow has a rotation frequency , for the first gyrotron type, where , , Δ V is the potential difference between the inner (radius b 1 ) and outer (radius b 2 ) coaxial conductors, r 0 is the electron flow rotation radius. Thus, the generation frequency ω ≈ k ω н is determined by both B 0 and Δ V . Moreover, at Δ V = 0 the device becomes a classical high-orbit gyrotron, at B 0 = 0 a classical helitron. Therefore, at B 0 ≠ 0 and Δ V ≠ 0 it should be called a gyrohelitron, the generation frequency of which is tuned electrically - by changing Δ V . The article presents the design schemes of a gyrohelitron and a two-beam four-mirror gyrotron. In both cases, piezoelectric devices realize synchronous tuning of the frequency, just it allows the devices becoming fully electrically controllable. The following results were obtained for the gyrohelitron. Resonator field – H 211 , interaction on the second harmonic ω s ; a) narrow-band tuning 10 %: maximum efficiency – 55 %, minimum efficiency – 25 %; β 0 = v 0 / c = 0.27; q = v 0 ⊥ / v || = 2; b) broadband tuning 58 %: maximum efficiency – 18 %, minimum efficiency – 14 %; β 0 = v 0 / c = 0.2; q = v 0 ⊥ / v || = 2. The given results for the gyrohelitron indicate that it is promising to use electrical frequency tuning in a coaxial gyro-BWT and the amplification band in a gyro-TWT, since these devices do not require piezoelectric tuning of electrodynamic structures.

The Effect of Rotor Radius Ratio on The Performance of Hybrid Vertical Axis Wind Turbine Savonius-Darrieus NREL S809

This research aims to know the effect of the Rotor Radius Ratio on the performance of the hybrid Vertical Axis Wind Turbine Savonius-Darrieus NREL S809 model using the Computational Fluid Dynamics method. Two-bladed Savonius is used as an internal rotor, and three-bladed Darrieus NREL S809 as an external rotor. Turbine model performance is analyzed through the value of the Moment Coefficient and Power Coefficient. The result shows that the increase in the Rotor Radius Ratio value causes an increase in the initial Moment Coefficient but a decrease in the maximum Power Coefficient value. At the initial TSR, the Rotor Radius Ratio 0.5 model has the best Moment Coefficient value among all variations but has the lowest maximum Power Coefficient value.