Angular Misalignment Research Articles

Nonlinear dynamic analysis of floating involute splines considering comprehensive misalignment

In this study, a bending-torsion-axial dynamic model of floating involute spline coupling was established, considering the influence of misalignment. The dynamic characteristics of the spline coupling were analyzed under a parallel misalignment of 1.0×10−4 m or 2.0×10−4 m, an angular misalignment α of 0.1° or 0.3°, and the combined misalignment. A test bench for floating involute spline couplings was constructed to verify the accuracy of the dynamic characteristics under the theory. The results revealed that misalignment had a profound impact on the dynamic characteristics of the floating spline. Under the parallel misalignment of 2.0×10−4 m and the angular misalignment α of 0.3°, the force distribution on each tooth of the spline coupling was extremely uneven, which considerably reduced its performance and service life. As the floating distance gradually increases, the stability of the system decreases dramatically. The study laid a solid numerical foundation for the design of highly reliable, precise, and durable involute spline couplings for aviation use.

Error Analysis of Heterodyne Interferometry Based on One Single-Mode Polarization-Maintaining Fiber.

Using polarization-maintaining fiber (PMF) in dual-frequency heterodyne interferometry has the advantages of reducing the laser's own drift, obtaining high-quality light spots, and improving thermal stability. Using only one single-mode PMF to achieve the transmission of dual-frequency orthogonal, linearly polarized beam requires angular alignment only once to realize the transmission of dual-frequency orthogonal, linearly polarized light, avoiding coupling inconsistency errors, so that it has the advantages of high efficiency and low cost. However, there are still many nonlinear influencing factors in this method, such as the ellipticity and non-orthogonality of the dual-frequency laser, the angular misalignment error of the PMF, and the influence of temperature on the output beam of the PMF. This paper uses the Jones matrix to innovatively construct an error analysis model for the heterodyne interferometry using one single-mode PMF, to realize the quantitative analysis of various nonlinear error influencing factors, and clarify that the main error source is the angular misalignment error of the PMF. For the first time, the simulation provides a goal for the optimization of the alignment scheme of the PMF and the improvement of the accuracy to the sub-nanometer level. In actual measurement, the angular misalignment error of the PMF needs to be smaller than 2.87° to achieve sub-nanometer interference accuracy, and smaller than 0.25° to make the influence smaller than ten picometers. It provides theoretical guidance and an effective means for improving the design of heterodyne interferometry instruments based on PMF and further reducing measurement errors.

An Analytical Framework of Multisector Rectenna Array Design for Angular Misalignment Tolerant RF Power Transfer Systems

A design procedure is presented for an angular misalignment-tolerant multisector rectenna array used as a wireless energy harvesting (WEH) system. The proposed analytical framework derives constraints on the synthesized harvested dc power pattern of the rectenna element as a solution to completely mitigate the angular misalignment. The derived constraints determine the optimal number of sectors required to ensure uniform harvesting capability across the entire azimuth plane. This is analytically verified for a conventional patch antenna used in the rectenna element of the multisector WEH system. The design constraints give <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> and 12 sectors the optimal solution for single patch and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 1$ </tex-math></inline-formula> patch array rectenna. Furthermore, a new multilayer wide-beam rectenna is proposed at 5.8 GHz requiring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=6$ </tex-math></inline-formula> sectors to mitigate the angular misalignment with 36.5% size reduction when compared with the conventional patch WEH system. The prototype of the WEH systems using the conventional patch rectenna and the proposed rectenna is fabricated and measured. The measurement results corroborate the analytical and simulation results validating the capability of the proposed framework to achieve uniform energy harvesting in the entire azimuth plane.

Dynamic Service Mechanism of Double-Row Spherical Roller Bearings Due to Self-Aligning Behavior

Spherical roller bearings (SRBs) are widely used under self-aligning operating conditions, such as rotor bending or an angular misalignment between inner and outer rings due to their self-aligning function. However, the characterization of SRBs’ self-aligning function is often ignored in the present models. The reason for this is that the self-aligning condition is essentially a fault condition, and many scholars have assumed SRBs are in an ideal operating condition. Although there is nothing wrong with this analysis theoretically, it is incapable of characterizing SRBs’ service behavior comprehensively. In this work, the Lagrange equation was introduced to model the relationship among the rollers and the inner and outer rings. The contact region in particular was characterized in detail in order to solve the problems of undetermined contact status (UCS) and the varying law of the self-aligning contact angle (SAC angle). For the experiment, a novel SRBs pedestal with a self-aligning operating condition was designed, and the relevant self-aligning function testing was carried out. A good agreement was shown between the theoretical and experimental results. The results pointed out that, if taking no account of the self-aligning function, SRBs can be regarded as angular contact ball bearings or cylinder roller bearings. The amplitude of the inner-ring motion orbit is determined by the external load, but the shape is influenced by the direction and magnitude of the SAC angle. In the example of this paper, the values of the main frequency equal 136.8 Hz. Some additional frequencies are clearly aroused under the self-aligning operating condition, whose value is approximately equal to 8.3 Hz or its integer multiples. The dynamic performance of SRBs will be substantially improved by a light axial load plus an anticlockwise self-aligning contact angle rather than a large axial preload.

A metamaterial‐incorporated wireless power transmission system for efficiency enhancement

SummaryIn this paper, an efficient wireless power transmission (WPT) system that incorporates a new negative permeability metamaterial is presented. The operating principle of the metamaterial with negative permeability is first analyzed. To improve transmission efficiency of the WPT system at the operating frequency of 13.56 MHz, a new metamaterial with three open rings is designed. By respectively placing a single metamaterial slab and double metamaterial slabs at different positions between transmitting coil and receiving coil, the performance of the proposed WPT system is evaluated by simulation work. The corresponding magnetic field distribution is also analyzed. Besides, comparison is made with the conventional WPT system without metamaterial. It is found that transmission efficiency of the proposed WPT system is obviously improved when incorporating the metamaterial since the designed metamaterial effectively focuses magnetic field towards the receiving coil. Comparing with the conventional system, the results also show that the proposed WPT system is more robust to lateral and angular misalignment of the receiving coil. With the designed metamaterial, it is found that the proposed system with double metamaterial slabs performs better than that with a single metamaterial slab.

VIBRATION ANALYSIS OF A V-BELT DRIVE IN VARIABLE CONDITIONS OF PULLEYS MISALIGNMENT

This paper deals with vibration analysis of a V-Belt drive based on altering conditions of pulleys misalignment. The main question this paper tries to answer is whether there is a direct and measurable relation between the pulley misalignment conditions and vibration of the machine. Using the ADASH vibration analyser with accelerometer sensors and laser speed sensor attached, we gathered data from our test stand purposely build for this task. Designing of the test stand is described as well as some basics of vibration measurement and belt drive operation. Next a testing methodology is described where several conditions of parallel and angular misalignment as well as different belt tension conditions were simulated using adjustability of our testing stand. Then in data analysis part we look at relations between multiple measurements of different pulley misalignment conditions viewed in time domain vibration analysis. [VSB-TUO].

A Compact 3-D Multisector Orientation Insensitive Wireless Power Transfer System

The power conversion efficiency (PCE) in wireless power transfer (WPT) degrades due to angular misalignment between the transmitter (Tx) and the rectenna (Rx) along the azimuth plane. Therefore, a compact 3-D multisector orientation insensitive WPT system is proposed to address this problem. The optimal number of sectors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> ) is determined analytically using patch antenna design equations to mitigate the effects of angular misalignment. In addition, conditions on the receiver antenna radiation pattern are investigated to enhance the performance of the WPT system. Furthermore, the observed conditions are utilized for designing a high gain WPT system at 5.8 GHz with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> sectors. The proposed WPT system provides uniform power harvesting capability in the azimuth plane and 51.2% higher power harvesting capacity than the patch antenna WPT system.

Prestress Modal Analysis under Assembling Error of Diaphragm Disc Coupling

The high-speed and high-torque diaphragm disc coupling used in coal machine-driven systems is the critical power transmission component, especially in high-speed and heavy-duty shafting. The dynamic rotor characteristics are significant. In the case of external excitation in the installation or working process of diaphragm coupling, it is inevitable to have axial deviation, angular misalignment, and radial misalignment error. Therefore, analyzing the prestress mode under the assembly error of diaphragm disc coupling is crucial. The finite element model of diaphragm plate coupling was established using ABAQUS software. The accessible way under critical speed, the mode under axial dislocation, and radial dislocation were analyzed. The results show that the assembly error of the diaphragm disc coupling will affect the first and second-order natural frequencies in a specific range but will not cause resonance.

Pengaruh besaran arus dan kecepatan las terhadap angular distorsi pada SS304 dengan GMAW

SS304 is a steel with good corrosion resistance, so it is widely used in various industrial worlds. The stainless-steel fabrication process generally uses a joining process by welding. To get a good welding result, it is necessary to choose the correct parameters to reduce the potential for welding imperfections. In the ISO 6520-1-520 standard, excessive distortion is a welding imperfection that must be avoided because it can cause angular misalignment, namely ISO 6520-1-508 standard. In this research, an experiment was conducted to determine the effect of current strength and welding speed on the angular distortion generated using GMAW. The current strength is 115, 120, and 125 A, while the welding speed is 3.6, 3.9, and 4.2mm/s. The angular distortion of the weld results is measured using a CMM (Coordinate Measuring Machine) after the material has experienced natural cooling. From the research results obtained, it is known that the greater the current strength, the greater the resulting angular distortion. On the other hand, if the welding speed is greater, the width of the weld bead and the resulting angular distortion will be smaller.

Drone-assisted collection of environmental DNA from tree branches for biodiversity monitoring.

The protection and restoration of the biosphere is crucial for human resilience and well-being, but the scarcity of data on the status and distribution of biodiversity puts these efforts at risk. DNA released into the environment by organisms, i.e., environmental DNA (eDNA), can be used to monitor biodiversity in a scalable manner if equipped with the appropriate tool. However, the collection of eDNA in terrestrial environments remains a challenge because of the many potential surfaces and sources that need to be surveyed and their limited accessibility. Here, we propose to survey biodiversity by sampling eDNA on the outer branches of tree canopies with an aerial robot. The drone combines a force-sensing cage with a haptic-based control strategy to establish and maintain contact with the upper surface of the branches. Surface eDNA is then collected using an adhesive surface integrated in the cage of the drone. We show that the drone can autonomously land on a variety of branches with stiffnesses between 1 and 103newton/meter without prior knowledge of their structural stiffness and with robustness to linear and angular misalignments. Validation in the natural environment demonstrates that our method is successful in detecting animal species, including arthropods and vertebrates. Combining robotics with eDNA sampling from a variety of unreachable aboveground substrates can offer a solution for broad-scale monitoring of biodiversity.

Does twist angle affect the properties of water confined inside twisted bilayer graphene?

Graphene nanoslit pores are used for nanofluidic devices, such as, in water desalination, ion-selective channels, ionic transistors, sensing, molecular sieving, blue energy harvesting, and protein sequencing. It is a strenuous task to prepare nanofluidic devices, because a small misalignment leads to a significant alteration in various properties of the devices. Here, we focus on the rotational misalignment between two parallel graphene sheets. Using molecular dynamics simulation, we probe the structure and dynamics of monolayer water confined inside graphene nanochannels for a range of commensurate twist angles. With SPC/E and TIP4P/2005 water models, our simulations reveal the independence of the equilibrium number density- n ∼ 13nm-2 for SPC/E and n ∼ 11.5nm-2 for TIP4P/2005- across twists. Based on the respective densities of the water models, the structure and dielectric constant are invariant of twist angles. The confined water structure at this density shows square ice ordering for SPC/E water only. TIP4P/2005 shows ordering at the vicinity of a critical density (n ∼ 12.5nm-2). The average perpendicular dielectric constant of the confined water remains anomalously low (∼2 for SPC/E and ∼6 for TIP4P/2005) for the studied twist angles. We find that the friction coefficient of confined water molecules varies for small twist angles, while becoming independent for twists greater than 5.1°. Our results indicate that a small, angular misalignment will not impair the dielectric properties of monolayer water within a graphene slit-pore, but can significantly influence its dynamics.

Geometry optimisation of highly crowned gear couplings working in high misalignment applications to reduce tooth root stresses

Crowned gear couplings are mechanical components used to transmit power between misaligned rotating shafts. Their geometry is characterised by a significant longitudinal crowning to accommodate angular misalignment. Recent studies reveal that high misalignments drastically reduce the number of teeth in contact and lead to an uneven load distribution among engaged teeth. Consequently, tooth root fracture becomes a common failure mode. Current standards only address misalignment angles below 1.5°, treating applications with greater misalignments as special cases without design guidelines or stress prediction methods. This study proposes a procedure to optimize the design of crowned gear couplings working in high misalignment applications by determining tooth root stress distribution. The geometry is analytically generated, while finite element models are used to calculate the stress distribution. Experimental validation is performed using a dedicated test rig. The obtained results are very close to the ones from the numerical model, demonstrating the suitability of the method for crowned gear couplings operating under significant angular misalignments. The optimized design reduces tooth root stress by 50%, which will increase the fatigue life of the component or enable the application of higher torque values.

ОЦЕНКА ВЕЛИЧИНЫ ОДНОВРЕМЕННО ПРИСУСТВУЮЩИХ УГЛОВОЙ И ПАРАЛЛЕЛЬНОЙ РАСЦЕНТРОВОК И ДИСБАЛАНСА РОТОРОВ ПО СИГНАЛАМ ВИБРАЦИИ

One of the important tasks of non–destructive testing of rotary mechanisms is to determine the degree of shaft misalignment. Currently, the misalignment is detected based on the analysis of the amplitude spectrum of vibration. Experimental data show that the amplitudes of the vibration components depend on the displacement of the shafts according to a law close to linear, but with different coefficients of proportionality. The coefficients depend on the design of the coupling, and are usually unknown. In well-known works, the vibration of centered shafts is modeled as a rule by introducing forces into the system at different frequencies of equal amplitude. This does not agree with the observational data, in particular with the different dependence of the amplitudes of the components on the magnitude of the misalignment. In addition, there are usually several sources of forces in the system. In particular, parallel and angular misalignment can be expressed simultaneously and create oscillations at three harmonics of the rotor speed. The imbalance of the rotor leads to the appearance of oscillations at the frequency of its rotation. The oscillations can only be summed vector-wise, i.e. taking into account the phase. Without taking into account the phases of the vibration components, it is impossible to make a correct conclusion about the magnitude of the defects present. In this paper, a method is proposed for calculating the magnitude of the parallel alignment of the shafts and the imbalance of one of them

A Misalignment Tolerance and Lightweight Wireless Charging System via Reconfigurable Capacitive Coupling for Unmanned Aerial Vehicle Applications

This letter proposes a novel capacitive power transfer system for the unmanned aerial vehicles (UAVs) with lightweight in receivers and robust misalignment tolerance characteristics. The design and analysis of a reconfigurable capacitive coupler are presented at first. The transmitter adopts four rectangular copper plates, which can be reconfigured according to the landing positions and directions. The receiver includes two hollow cylindrical copper-foil sleeves wrapped at the bottom of UAV landing gears, thereby leading to the adaption of the UAV's structure and the tolerance to lateral-, longitudinal-, and angular misalignment. Then, simulation and prototype experiments are carried out to verify the proposal. The results show that the prototype has low leakage electric flux at the UAV fuselage and can deliver 212.1 W with a dc-to-dc efficiency of 82.5%. Especially the proposal allows UAV to be powered within ±0.76 A of output current variation for different landing positions and directions, and the system dc-to-dc efficiency variation is within ±1%.

Skew of Frictional Power Transmission Flat Belt Driven by Pulleys with In-Plane Angular Misalignment

Skew of Frictional Power Transmission Flat Belt Driven by Pulleys with In-Plane Angular Misalignment

Anti-Symmetric Wing Transmitter for Angular Misalignment Insensitive Wireless Power Transfer to Biomedical Implants

This paper presents an anti-symmetric wing transmitter (ASW-Tx) for angular misalignment insensitive WPT to biomedical implants. Symmetrical field distribution on two orthogonal planes of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oxz</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oyz</i> are analyzed theoretically to obtain stable power transfer efficiency (PTE) by rotating Rx around the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oz</i> axis. Moreover, toroidal magnetic fluxes are generated by ASW to adapt with different Rx’s tilted angles on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ox</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oy</i> axes. An impedance matching network (IMN) is proposed and implemented to match ASW-Tx’s impedance to source impedance. An implantable Rx is employed to verify the ASW-Tx’s performance. Experimental measurements are carried out with selected Rx’s tilted angles (vary from 0° to 90° around <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ox</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oy</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oz</i> axis) to validate the effectiveness of proposed ASW-Tx’s. Verification results show that a stable efficiency variation was achieved with a maximum fluctuation of 4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dB</i> by rotating Rx tilted angles. Moreover, the ASW-Tx can supply power effectively with a transmission efficiency of up to -18.4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dB</i> to an implantation depth of 15 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mm</i> .

Misalignment-Resilient Propagation Model for Underwater Optical Wireless Links.

This paper proposes a multiple-lens receiver scheme to increase the misalignment tolerance of an underwater optical wireless communications link between an autonomous underwater vehicle (AUV) and a sensor plane. An accurate model of photon propagation based on the Monte Carlo simulation is presented which accounts for the lens(es) photon refraction at the sensor interface and angular misalignment between the emitter and receiver. The results show that the ideal divergence of the beam of the emitter is around 15° for a 1 m transmission length, increasing to 22° for a shorter distance of 0.5 m but being independent of the water turbidity. In addition, it is concluded that a seven-lense scheme is approximately three times more tolerant to offset than a single lens. A random forest machine learning algorithm is also assessed for its suitability to estimate the offset and angle of the AUV in relation to the fixed sensor, based on the power distribution of each lens, in real time. The algorithm is able to estimate the offset and angular misalignment with a mean square error of 5 mm (6 mm) and 0.157 rad (0.174 rad) for a distance between the transmitter and receiver of 1 m and 0.5 m, respectively.

Symmetric nonconfocal Fabry–Perot cavity with a stable long optical path length and improved tolerance for angular alignment

Engineering of optical alignment tolerance between a laser source and a Fabry–Perot (FP) cavity is of great importance in optimizing a laser analysis system and saving costs in the additional alignment task. We propose a modification of the conventional confocal FP (CFP) cavity–a symmetric nonconfocal FP (SNFP) cavity with two identical spherical mirrors separated by a distance equal to half of the common radius of curvature. Numerical analysis of the two cavities reveals that the SNFP cavity has better off-axis stability and much better angular misalignment tolerance than the CFP cavity, even with a longer optical path length (OPL). The SNFP cavity provides a six-transit path length for a basic cavity mode that supports a 1.5-fold long OPL within the same volume as the CFP cavity, which is favorable for applications requiring limits on the footprint and weight of the cavity. In addition, a ray-tracing simulation with a disk-type source having an angular Gaussian distribution (α = β = 5 deg) reveals that the emission beam profile from the SNFP cavity is narrower than that from the CFP cavity. These results are expected to help reduce cavity loss and to improve alignment efficiency between the laser source and the FP cavity.

A Review of Aviation Spline Research

Splines are irreplaceable in high-speed aviation fields due to their simplicity, reliability, and high specific power. Aviation splines are not only subjected to severe operating mechanical loads, but also sometimes operate under grease-lubricated and non-lubricated environments. All of this results in aviation splines suffering widespread failures. Since the 1960s, many researchers have carried out much research on aviation splines. The wide range of research topics demonstrates the technical challenges of understanding aviation spline. This paper reviews the research of aviation spline from the aspects of failure form, fatigue strength, surface contact stress, effects of lubrication, and misalignment on wear, as well as experiments. Relevant research shows crowned splines can mitigate the spline wear process induced by angular misalignment, and oil-lubricating splines experience almost no wear. This paper also looks forward to the future development directions of aviation splines.

Angular Misalignment Calibration for Dual-Antenna GNSS/IMU Navigation Sensor.

We address the angular misalignment calibration problem, which arises when a multi-antenna GNSS serves as a source of aiding information for inertial sensors in an integrated navigation system. Antennas usually occupy some outside structure of the moving carrier object, whilst an inertial measurement unit typically remains inside. Especially when using low- or mid-grade MEMS gyroscopes and accelerometers, it is either impossible or impractical to physically align IMU-sensitive axes and GNSS antenna baselines within some 1-3 degrees due to the micromechanical nature of the inertial sensors: they are just too small to have any physical reference features to align to. However, in some applications, it is desirable to line up all sensors within a fraction-of-a-degree level of accuracy. One may imagine solving this problem via the long-term averaging of sensor signals in different positions to ensure observability and then using angle differences for analytical compensation. We suggest faster calibration in special rotations using sensor fusion. Apart from quicker convergence, this method also accounts for run-to-run inertial sensor bias instability. In addition, it allows further on-the-fly finer calibration in the background when the navigation system performs its regular operation, and carrier objects may undergo gradual deformations of its structure over the years.