Initial Pitch Angle Research Articles

Pitch Angle Estimation of Monocular In-vehicle Camera Using Drive Recorder Video

In recent years, the movement for the development and commercialization of autonomous driving vehicle is rapidly getting higher. In order to spread autonomous driving vehicles, it is necessary to evaluate safety, and we must create a scenario for that. Therefore, we aim to extract parameters for scenario creation from near-miss incident data. In this research, we propose a method of pitch angle estimation of monocular camera using drive recorder video for the measurement relative distance. First, estimate initial pitch angle estimation from lane parallelism. Next, in a scene where the pitch angle changes due to sudden braking, the estimation method is switched. Here, the pitch angle is estimated from feature point matching.

Resonance Interaction of Relativistic Electrons with Ion-Cyclotron Waves. I. Specific Features of the Nonlinear Interaction Regimes

We analyze the resonant interaction of relativistic electrons with ion-cyclotron waves in the Earth radiation belts. Finite-length wave packets with variable frequencies and different amplitude profiles are considered. Specific features of the nonlinear interaction regimes are analyzed on the basis of solving numerically a system of equations of the particle motion along with the efficiency of this interaction for a single pass of the particle through the wave packet. In the first part of this work, the peculiarities of the trajectories of individual particles are analyzed. The influence of the shape of the wave packet on the well-known regimes, such as particle trapping by the wave field and particle phase bunching, which leads to a non-zero average variation in the pitch angle in an inhomogeneous medium, are considered. It is shown that a long stay of a particle near the separatrix on the phase plane in the region far from the saddle leads to a strong decrease in the pitch angle of the particle in the absence of the trapping as well. This nonlinear regime (directed scattering) is possible for comparatively low initial pitch angles. In this case, the value of the pitch angle decrease depends on the initial phase of the particle. It is shown that the trajectories corresponding to the directed scattering can be regarded as a transitional type of trajectories, between the trajectories of the untrapped and trapped particles. Quantitative estimates of variations in the pitch angle are obtained, and it is confirmed that the directed scattering and trapping of particles by the wave field can lead to electron precipitation into the loss cone.

A finite deformation theory for the climbing habits and attachment of twining plants

Twining plants, using their special attachment structure to cling to a support and grow upward to capture more sunshine without losing stability, have fascinated many scholars. A mechanics model to interpret this natural selection phenomenon based on the finite deformation theory is developed here. Results show the pitch angle of the twiner, the elongation in the stem and the radius ratio of the twiner to its support play an important role in the twining habit. To get more sunshine overhead, twiners tend to increase the initial pitch angle but to decrease the final twining angle to maintain their positions and stability. By taking into account of the tuning of the interfacial strength with the microstructure, the maximum values of the elongation and the support radius are determined, over which twiners will lose their ability to wind around. The proposed model and the results can not only clarify the mechanism of climbing habits and attachment, but also show the potential applications for the twining-mimic designs.

Design and landing dynamic analysis of reusable landing leg for a near-space manned capsule

To improve the landing performance of a near-space manned capsule under various landing conditions, a novel landing system is designed that employs double chamber and single chamber dampers in the primary and auxiliary struts, respectively. A dynamic model of the landing system is established, and the damper parameters are determined by employing the design method. A single-leg drop test with different initial pitch angles is then conducted to compare and validate the simulation model. Based on the validated simulation model, seven critical landing conditions regarding nine crucial landing responses are found by combining the radial basis function (RBF) surrogate model and adaptive simulated annealing (ASA) optimization method. Subsequently, the adaptability of the landing system under critical landing conditions is analyzed. The results show that the simulation effectively results match the test results, which validates the accuracy of the dynamic model. In addition, all of the crucial responses under their corresponding critical landing conditions satisfy the design specifications, demonstrating the feasibility of the landing system.

Analytical forms of the first 14 moments of the cosmic ray Fokker–Planck equation

The Fokker–Planck transport equation describing the motion of energetic particles through a plasma is explored analytically. The latter equation provides a pitch-angle and position-dependent distribution function of the charged particles. In the current paper the first 14 moments of this equation are computed exactly for an arbitrary initial pitch angle. Such analytical forms are required in nonlinear treatments of perpendicular transport and other scenarios in plasma physics and astrophysics.

Experimental approach to investigate the constrained recovery behavior of coiled monofilament polymer fibers

The aim of this work is to propose a new approach for investigating the thermo-mechanical behavior of coiled oriented polymer fibers with fixed ends and promote an understanding of the actuation response of coiled polymers in constrained recovery applications. In the proposed experimental methodology, a coiled fiber was pre-stretched by 50% and the distance between its ends remained constant, then it was subjected to a heating-cooling cycle ranging from 30 °C to 120 °C and the induced restoring force was measured. Based on these measurements, axial deformation and shear strain were obtained from full-field displacements extracted by the digital image correlation method from images of the coiled fiber. Three coiled fibers with different initial pitch angles were manufactured, and samples with lengths of 15 mm and 20 mm were tested. Bias angles and coil radius were also estimated using the experimental data associated with the helical spring theory. Results show that significant shape changes can be noticed above the glass transition temperature (47 °C), and these changes induce variation in the resultant forces. The effects of thermal softening and thermal contraction for a modest negative thermal expansion coefficient became evident at temperatures ranging from ∼47 °C to ∼90 °C, while the response of a coiled homochiral polymer fiber was achieved at temperatures close to 90 °C. During the cooling process, saturated states of the axial deformation and shear strain of the coiled fibers were observed at temperatures between 120 °C and 100 °C.

Accuracy Analysis of the Analytical Solution for the Lunar Lander Terminal Guidance Problem

An analysis of the accuracy and reliability of the proposed analytical solution for the lunar lander terminal guidance problem was carried out. The analytical solution for 3D terminal guidance problem was obtained for a constant acceleration trajectory and thrust vector orientation programs, which are essentially linear with time. In order to achieve 6 terminal conditions (position and velocity terminal vector components) 6 guidance law parameters were used: time-to-go, braking deceleration, initial pitch angle and pitch rate, initial yaw angle and yaw rate. The simulation results of the lunar lander terminal guidance using the proposed analytical solution were presented. The analysis of the proposed terminal guidance scheme and some similar schemes were carried out by mathematical modeling of the landing maneuver from a certain initial state to the desired spot near the lunar surface. By varying the initial position and the velocity parameters, when the terminal point was fixed, the statistic characteristics of the terminal guidance solution errors in the terminal position and velocity were estimated. An analysis of the simulation results validates the basic performance of the proposed terminal guidance scheme for the lunar pinpoint landing. Estimates of the terminal guidance accuracy for the proposed scheme exceed the corresponding estimates for the alternative considered schemes. The next phase of this research will be intended for studying the influence of variations in the initial prelanding orbit parameters (obliquity, ascending node longitude, argument of periapsis, periapsis height, apoapsis height) on the terminal guidance accuracy.

Surface-to-air missile path planning using genetic and PSO algorithms

Optimization algorithms use various mathematical and logical methods to find optimal points. Given the complexity of models and design levels, this paper proposes a heuristic optimization model for surface-to-air missile path planning in order to achieve the maximum range and optimal height based on 3DOF simulation. The proposed optimization model involves design variables based on the pitch programming and initial pitch angle (boost angle). In this optimization model, we used genetic and particle swarm optimization (PSO) algorithms. Simulation results indicated that the genetic algorithm was closer to reality but took longer computation time. PSO algorithm offered acceptable results and shorter computation time, so it was found to be more efficient in the surface-to-air missile path planning.

Active participation of variable speed wind turbine in inertial and primary frequency regulations

Power systems have increasingly exhibited a need for a potential frequency governor with virtual inertial control (VIC) and primary frequency regulation (PFR) functions in recent years, due to the increased penetration of wind turbines that almost have no frequency response. In this paper, a novel integrated frequency governor applied to a wind turbine is proposed to provide fast active power support and scheduled power allocation for both temporary inertial response and continued PFR. Below rated wind speed, an initial pitch angle is calculated firstly to preset a proper de-loading level for PFR in response to frequency drops, according to the presented relations of CP-λ-β. Under the de-loading operation conditions, the de-loading power tracking curve is replaced by the defined VIC curves, and the inertial response is then obtained by rapidly shifting the VIC curves. Based on analysis of the mechanical characteristics of wind turbines with frequency droop, a primary frequency control strategy facilitated by the regulation of pitch angles is additionally proposed. A preset β/f droop curve is added to the de-loading pitch controller to regulate the mechanical power for scheduled power allocation, and thus satisfying the P/f droop demand of system PFR. Finally, the experiments and simulation results demonstrate that by using the proposed frequency governor a doubly fed induction generator (DFIG) based wind turbine can provide both temporary virtual inertia and continued load sharing to improve the dynamic frequency stability of the power grid with high wind power penetration.

Robustness analysis on aerial deployment motion of a Mars aircraft using multibody dynamics simulation: effects of wing-unfolding torque and timing

ABSTRACTThis paper investigates the effects of the design variables of an aerial deployment mechanism on the robustness of the aerial deployment through a multibody dynamics simulation. The aircraft is modelled as three joined rigid bodies: a right wing, a left wing and a centre body. A spring-loaded hinge is adopted as an actuator for deployment. The design variables are the hinge torque and the deployment timing. The robustness is evaluated using a sigma level method. The margins for the safe deployment conditions are set for the evaluation functions. The dispersive input variables are the initial drop velocity, the surrounding gust velocity, the initial pitch angle and the initial height. The design point with a deployment torque scale valueFof 0.7 and a right-wing deployment delay timeTSRof 1.0 s can safely deploy in the low-torque deployment condition. This design point is able to accomplish both a safe deployment and a lightweight deployment mechanism.

THE IBEX RIBBON AND THE PICKUP ION RING STABILITY IN THE OUTER HELIOSHEATH. I. THEORY AND HYBRID SIMULATIONS

ABSTRACT The nearly circular band of energetic neutral atom emission dominating the field of view of the Interplanetary Boundary Explorer (IBEX ) satellite, is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath and the interstellar space beyond. Several models for the PUI dynamics of this mechanism have been proposed, each requiring either strong or weak scattering of the initial pitch angle. Conventional wisdom states that ring distributions tend to generate waves and scatter onto a shell on timescales too short for charge exchange to occur. We performed a careful study of ring and thin shell proton distribution stability using theoretical tools and hybrid plasma simulations. We show that the kinetic behavior of a freshly injected proton ring is a far more complicated process than previously thought. In the presence of a warm Maxwellian core, narrower rings could be more stable than broader toroidal distributions. The scattered rings possess a fine structure that can only be revealed using very large numbers of macroparticles in a simulation. It is demonstrated that a “stability gap” in ring temperature exists where the protons could retain large gyrating anisotropies for years, and the wave activity could remain below the level of the ambient magnetic fluctuations in interstellar space. In the directions away from the ribbon, however, a partial shell distribution is more likely to be unstable, leading to significant scattering into one hemisphere in velocity space. The process is accompanied by turbulence production, which is puzzling given the very low level of magnetic fluctuations measured in the outer heliosheath by Voyager 1.

Numerical Simulation of Water-Landing Performance of a Regional Aircraft

The water-landing performance of a regional airplane with high wing and high tail is studied using the numerical simulation method. In the simulation, the Reynold-averaged Navier–Stokes equations with the realizable turbulence model are solved by the finite volume method. The volume-of-fluid method is used to capture the water–air interface, and the six-degree-of-freedom model and the global moving mesh method are used to deal with the relative motion between the water and the airplane. In the result section, a typical water-landing process is studied in detail, and the effects of initial pitch angle and initial descent velocity on the water-landing performance are presented and analyzed. A large initial pitch angle is suggested to improve the safety during water landing.

Using orbital tethers to remediate geomagnetic radiation belts

AbstractThe Van Allen radiation belts pose a hazard to spacecraft and astronauts, and similar radiation belts around other planets pose a hazard to interplanetary probes. We discuss a method of remediating these radiation belts first proposed by Danilov and Vasilyev, and recently improved by Hoyt, Minor, and Cash, where a long, charged tether is placed in orbit inside a radiation belt. In this approach, an electric field of the tether scatters the belt particles into a pitch angle loss cone leading to absorption of the particles in the atmosphere. A test particle calculation is presented which computes the scattered pitch angle of belt particles as a function of initial pitch angle and gyrophase for different particle energies. The moments of the resulting distribution of scattered angle versus initial pitch angle are used to compute the number density of the belt as a function of time using a Fokker‐Planck diffusion approximation. Finally, we use the characteristic timescales of scattering for particles of different energies to discuss the feasibility of using such a system of tethers as a long and short‐term remediation solution.

A NEW MODEL FOR THE HELIOSPHERE’S “ IBEX RIBBON”

We present a model for the narrow, ribbon-like enhancement in the emission of ~keV energetic neutral atoms (ENA) coming from the outer heliosphere, coinciding roughly with the plane of the very local interstellar magnetic field (LISMF). We show that the pre-existing turbulent LISMF has sufficient amplitude in magnitude fluctuations to efficiently trap ions with initial pitch-angles near 90°, primarily by magnetic mirroring, leading to a narrow region of enhanced pickup-proton intensity. The pickup protons interact with cold interstellar hydrogen to produce ENAs seen at 1 AU. The computed width of the resulting ribbon of emission is consistent with observations. We also present results from a numerical model that are also generally consistent with the observations. Our interpretation relies only on the pre-existing turbulent interstellar magnetic field to trap the pickup protons. This leads to a broader local pitch-angle distribution compared to that of a ring. Our numerical model also predicts that the ribbon is double-peaked with a central depression. This is a further consequence of the (primarily) magnetic mirroring of pickup ions with pitch-angles close to 90° in the pre-existing, turbulent interstellar magnetic field.

Calculations of the integral invariant coordinates <I>I</I> and <I>L</I>* in the magnetosphere and mapping of the regions where <I>I</I> is conserved, using a particle tracer (ptr3D v2.0), LANL*, SPENVIS, and IRBEM

Abstract. The integral invariant coordinate I and Roederer's L or L* are proxies for the second and third adiabatic invariants, respectively, that characterize charged particle motion in a magnetic field. Their usefulness lies in the fact that they are expressed in more instructive ways than their counterparts: I is equivalent to the path length of the particle motion between two mirror points, whereas L*, although dimensionless, is equivalent to the distance from the center of the Earth to the equatorial point of a given field line, in units of Earth radii, in the simplified case of a dipole magnetic field. However, care should be taken when calculating the above invariants, as the assumption of their conservation is not valid everywhere in the Earth's magnetosphere. This is not clearly stated in state-of-the-art models that are widely used for the calculation of these invariants. The purpose of this work is thus to investigate where in the near-Earth magnetosphere we can safely calculate I and L* with tools with widespread use in the field of space physics, for various magnetospheric conditions and particle initial conditions. More particularly, in this paper we compare the values of I and L* as calculated using LANL*, an artificial neural network developed at the Los Alamos National Laboratory, SPENVIS, a space environment online tool, IRBEM, a software library dedicated to radiation belt modeling, and ptr3D, a 3-D particle tracing code that was developed for this study. We then attempt to quantify the variations between the calculations of I and L* of those models. The deviation between the results given by the models depends on particle initial position, pitch angle and magnetospheric conditions. Using the ptr3D v2.0 particle tracer we map the areas in the Earth's magnetosphere where I and L* can be assumed to be conserved by monitoring the constancy of I for energetic protons propagating forwards and backwards in time. These areas are found to be centered on the noon area, and their size also depends on particle initial position, pitch angle and magnetospheric conditions.

Electron impact ionization in the Martian atmosphere: Interplay between scattering and crustal magnetic field effects

Precipitating electrons are typically the dominant source of energy input into Mars' nighttime upper atmosphere, with consequences for atmospheric and ionospheric structure, composition, chemistry, and electrodynamics. Mars' spatially heterogeneous crustal magnetic fields affect the fluxes of precipitating electrons, via both the magnetic mirror force and Gauss' law of conservation of magnetic flux. We use a kinetic electron transport model to examine ionization rate profiles that result from the combination of these magnetic effects and elastic and inelastic scattering by atmospheric neutrals. Specifically, we calculate ionization rates as a function of altitude, crustal magnetic field strength, and the initial energy and pitch angle of the precipitating electrons, covering the relevant ranges of these parameters. Several complex behaviors are exhibited, including bifurcating ionization peaks with distinct characteristics and energy-dependent and crustal field strength-dependent increases in ionization with decreasing pitch angle. Elucidating such behavior is important for understanding the effect of Mars' unique crustal fields on the Mars upper atmosphere and ionosphere, both to predict the consequences of measured electron precipitation and to enable, for the first time, downward coupling of global plasma models with thermosphere-ionosphere models.

Investigation of scaling properties of a thin current sheet by means of particle trajectories study

AbstractA thin current sheet (TCS), with the width of an order of thermal proton gyroradius, appears a fundamental physical object which plays an important role in structuring of major magnetospheric current systems (magnetotail, magnetodisk, etc.). The TCSs are nowadays under extensive study by means of space missions and theoretical models. We consider a simple model of the TCS separating two half‐spaces occupied by a homogenous magnetic field of opposite sign tangential to the TCS; a small normal component of the magnetic field is prescribed. An analytical solution for the electric current and plasma density in the close vicinity of the TCS has been obtained and compared with numerical simulation. The number density and the electric current profiles have two maxima each. The characteristic spatial scale zS of the maxima location was investigated as a function of initial pitch angle of an incoming charge particle. The effect of the thermal dispersion of the incoming proton beam have been taken into consideration.

Particle acceleration at a reconnecting magnetic separator

While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. The effect upon particle behaviour of initial position, pitch angle and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains several free parameters and we study the effect of changing these parameters upon particle acceleration, in particular in view of the final particle energy ranges which agree with observed energy spectra.

SYNCHRO-CURVATURE RADIATION OF CHARGED PARTICLES IN THE STRONG CURVED MAGNETIC FIELDS

It is generally believed that the radiation of relativistic particles in a curved magnetic field proceeds in either the synchrotron or the curvature radiation modes. In this paper we show that in strong curved magnetic fields a significant fraction of the energy of relativistic electrons can be radiated away in the intermediate, the so-called synchro-curvature regime. Because of the persistent change of the trajectory curvature, the radiation varies with the frequency of particle gyration. While this effect can be ignored in the synchrotron and curvature regimes, the variability plays a key role in the formation of the synchro-curvature radiation. Using the Hamiltonian formalism, we find that the particle trajectory has the form of a helix wound around the drift trajectory. This allows us to calculate analytically the intensity and energy distribution of prompt radiation in the general case of magnetic bremsstrahlung in the curved magnetic field. We show that the transition to the limit of the synchrotron and curvature radiation regimes is determined by the relation between the drift velocity and the component of the particle velocity perpendicular to the drift trajectory. The detailed numerical calculations, which take into account the energy losses of particles, confirm the principal conclusions based on the simplified analytical treatment of the problem, and allow us to analyze quantitatively the transition between different radiation regimes for a broad range of initial pitch angles. We argue that in the case of realization of specific configurations of the electric and magnetic fields, the gamma-ray emission of the pulsar magnetospheres can be dominated by the component radiated in the synchro-curvature regime.

Research on Assessment Method of Airbag Cushion System for Airdropping Equipment

Based on thermodynamics theory and finite element method, a finite element model of equipment and its airbag cushion system is established and verified experimentally. The simulation results are obtained under the same conditions of the airdrop test and the simulation results agree very well with the experimental results, which indicate the established model is valid for further research. Because nonlinear model of airbags cushion system is very complicated, the calculation takes tens of hours of CPU time. As a result, the large-scale calculation is impossible. In order to overcome this problem, surrogate models are employed instead of the complex finite element model based on extended latin hypercube method and radial basis function. Initial velocity, initial heeling angle, initial pitch angle, lateral velocity and gradient are variables, while maximum acceleration, maximum heeling angle, maximum pitch angle and maximum airbag pressure are responses. Considering the influence of landing condition, Monte Carlo method and surrogate model are used to calculate landing success probability of airdropping equipment under multi-condition. The landing success probability calculated is 95.84%. Acceleration is the primary contributor to cushion performance, while pressure inside airbag is secondary contributor.