Relative Lateral Position Research Articles

An estimation method for vision-based autonomous landing system for fixed wing aircraft

In this paper, we propose a vision-based estimation method for autonomous landing of fixed-wing aircraft for Advanced Air Mobility. The concept of autonomous flight with minimal human intervention has gained significant interest with a particular focus on autonomous landing. The goal is to overcome the limitations of existing instrument landing systems and reduce reliance on GNSS during aircraft landing. The proposed system leverages the following techniques for high-performance and real-time operations in various real-world environments and during all stages of landing. A deep learning segmentation model was directly learned, created, and used for robust runway recognition performance against environmental changes around the runway. Algorithms were designed to adapt to different flight stages considering the varying information offered by image data when the aircraft is in mid-air and on the ground. The relative lateral position from the aircraft to the runway was estimated using bird’s-eye-view conversion and inverse projection techniques instead of conventional perspective-n-point methods for reducing the recognition error occurring from the conversion between 2D image and 3D world. Finally, the mixed-precision technique was used for the segmentation model to improve inference speed and ensure real-time operation in real-world deployment. Estimation stability and reliability were improved by using a Kalman Filter to cope with sensor uncertainties caused by the real-world flight environment. Consequently, we show that the average error in the lateral position estimation by the proposed method is comparable to the accuracy of a single GNSS and demonstrate successful autonomous landing of our test aircraft with a set of flight tests.

Procjena krivulje oštetljivosti čelične okvirne konstrukcije kod različitih potresa

The aim of this study is to investigate the effect of two categories of earthquake events on the fragility curves of steel building construction (structures with different number of stories) by considering relative lateral displacement as a damage criterion. The categories used to describe the change in the relative lateral position were chosen to be slight, moderate, extensive, and complete. Increased seismic demand increases the probability of exceeding. In other words, the greater the maximum earthquake acceleration, the higher is the probability of exceeding (PoE). In a 3-story structure, the increase in PGA increases the PoE of the structure at extensive failure levels. The fragility curves for the 2nd category earthquakes show a shift from the sleeping mode (gradual increase) to the standing state (rapid increase) compared to the 1st-class earthquakes in the 5-story model. Increasing the number of stories increases the PoE of extensive and large failures. The PoE of the extensive mode in the 7-story model was 10 and 15.5 % higher than that in the 5- and 3-story models, respectively. However, for the complete damage state, the PoE in the 5-story model was 6 and 7 % more than that in the 7- and 3-story models, respectively. Therefore, it can be concluded that increasing the number of stories increases the PoE, but this increase is more evident for the extensive failure level.

Safety of Raised Pavement Markers in Freeway Tunnels Based on Driving Behavior

Raised pavement markers (RPMs) are among the common safety features of roads, playing an important role in preventing and reducing traffic crashes. RPMs are regarded as an effective measure for reducing the high crash rate and mortality in freeway tunnels in China. In this study, a driving simulator experiment was conducted to investigate the safety of RPMs in a freeway tunnel. Two different RPM layouts were designed and compared to a control with no RPMs, and 32 drivers participated in the driving simulator experiments. The speed, relative speed difference, lateral position, accelerator power, acceleration, and pupil area were used as indicators of the response characteristics of drivers to RPMs, and the interaction of tunnel length, tunnel zone, and RPM alternatives was discussed. The results indicate that a significant interaction effect exists between tunnel length, tunnel zone, and RPM alternatives. RPMs could help reduce driver anxiety, boredom, and fatigue caused by the dark and monotonous tunnel driving environment, and improve driver alertness and consciousness of speed. Also, the driving risk increases with increasing tunnel length (1800 m to 3500 m).

Starshade formation flying II: formation control

Several starshade concepts for imaging exo-Earths would operate at the second Earth–Sun Lagrange point (L2) and consist of a starshade flying in formation tens to hundreds of thousands of kilometers from a telescope. The starshade would need to maintain meter-level lateral alignment with the line of sight from telescope to target star. A companion paper describes an optical sensing scheme using a pupil imaging camera in the telescope that can sense the relative lateral position to a few centimeters. A full flight-traceable formation flying framework that leverages this sensor is presented. In particular, a two-dimensional “disk deadbanding” algorithm is introduced for lateral control. The framework also maximizes the drift time between thruster burns to reduce interruption to scientific observations. The main sources of uncertainty affecting the control performance are compared, and it is found that spacecraft mass uncertainty is a driving factor. The formation flying environment is also analyzed to identify conditions that lead to worst-case differential gravity and solar radiation pressure disturbances. Finally, for a representative observation scenario with the Wide Field Infrared Space Telescope, this control system is tested through Monte Carlo simulations. The results show robust meter-level control with essentially optimal drift time between thruster burns.

Human Ability to Judge Relative Size and Lateral Position of a Sound Reflecting Board Using Click Signals: Influence of Source Position and Click Properties

In human echolocation, acoustic signals provide information enabling people to perceive the physical environment. Little is known about the relation between properties of click signals used for echolocation purposes and the effect of source position on the resulting echolocation performance. In this work, echolocation performance is studied for two different echolocation tests: board size identification and board lateralization. The used artificial source is placed in front of the mouth and in front of the chest. Three different synthesized test signals are used: two narrow band signals and one broadband click signal. Impulse responses were recorded in an anechoic room for each individual participant, and listening tests were carried out afterwards by playing post-processed individualized signals using headphones. Results show better performance with the sound source at the chest position in both experiments, with the difference in performance most prominent in the board size identification test. In the board lateralization test, the broadband click results in eminent better performance over narrow band click signals. This suggest that broadband and chest positioned signals seem favorable over narrow band and mouth positioned signals

Ghost reduction in CP-SSOCT having multiple references using Fourier-domain Shift and Sum.

We propose, test and validate a novel Fourier-domain based method for ghost image artifacts reduction in a common-path SSOCT system having multiple adjacent reference planes. Common-path probes with imaging systems containing high-index sapphire ball or other lenses produce multiple fixed references due to Fresnel reflections from the lens surfaces. The multiple reference planes produce multiple and overlapping OCT images. Since such ghost artifacts are the result of the superposition of multiple identical images having different amplitudes and spatial shifts, one can correctly shift and sum the images in the Fourier-domain once the relative amplitude and lateral position between the reference planes are known. This theory and numerical testing are presented to elucidate our method. We then validate the potential effectiveness using OCT imaging experiments.

Detection and Tracking of Road Barrier Based on Radar and Vision Sensor Fusion

The detection and tracking algorithms of road barrier including tunnel and guardrail are proposed to enhance performance and reliability for driver assistance systems. Although the road barrier is one of the key features to determine a safe drivable area, it may be recognized incorrectly due to performance degradation of commercial sensors such as radar and monocular camera. Two frequent cases among many challenging problems are considered with the commercial sensors. The first case is that few tracks of radar to road barrier are detected due to material type of road barrier. The second one is inaccuracy of relative lateral position by radar, thus resulting in large variance of distance between a vehicle and road barrier. To overcome the problems, the detection and estimation algorithms of tracks corresponding to road barrier are proposed. Then, the tracking algorithm based on a probabilistic data association filter (PDAF) is used to reduce variation of lateral distance between vehicle and road barrier. Finally, the proposed algorithms are validated via field test data and their performance is compared with that of road barrier measured by lidar.

Electroactive Tuning of Double‐Layered Metamaterials Based on π‐Conjugated Polymer Actuators

Novel electroactive metamaterials working in the terahertz (THz) and microwave frequency ranges are demonstrated utilizing π‐conjugated polymer actuators. Metamaterials are artificial composite materials based on subwavelength resonant elements called “meta‐atoms.” The resonant character of meta‐atoms typically restricts their operating frequency to a narrow range, therefore it is crucial to make them tunable in order to develop practical devices. A promising tuning scheme is based on changing the mutual position of meta‐atoms in a composite. When two meta‐atoms are placed in close vicinity such that their near‐fields interact, their resonant characteristics can be tuned by altering their relative position and/or orientation. Here linear actuators made from heavily doped polypyrrole films are utilized to change the relative lateral position of two THz metasurfaces, and accordion‐shaped origami actuators are used to change the distance between two microwave meta‐atoms. In both cases significant tunability of the resonances is obtained by the application of a control voltage. This approach here may open a new direction for creating tunable metamaterials based on a rich variety of π‐conjugated polymer actuators.

Lateral matching of periodic front and back textures in thin film silicon solar cells

We systematically study the influence of the relative lateral position of the front and back periodic textures on the light absorption in microcrystalline Si thin film solar cells by finite difference time domain method. We show that there is an optimum lateral position match between the periodic front and back textures, which allows maximum light absorption to be obtained in the Si thin film solar cells. A relative lateral shift between the front and back periodic textures breaks the symmetry of the conformal cell structure, which can result in more wave modes in the Si thin film solar cells.

Nonlinear dynamic image-based visual servoing of a quadrotor

This paper proposes a dynamic image-based visual servoing (IBVS) control law for a quadrotor unmanned aerial vehicle (UAV) equipped with a single fixed on-board camera facing downward. The motion control problem is to regulate the relative lateral position of the vehicle to a stationary target located on the ground. The control law is termed dynamic as it is based on the dynamics and kinematics of the vehicle. The proposed design uses a nonlinear input-dependent change of state coordinates and its error dynamics are proven to be locally exponentially stable with an estimate provided for the region of attraction. Experimental and simulation results demonstrate the method's ease of on-board implementation, performance, and robustness. The simulation and experimental results include a comparison with an established dynamic IBVS method. This comparison shows the proposed method can provide similar performance with the benefit of reduced complexity.

Complex local Moho topography in the Western Carpathians: Indication of the ALCAPA and the European Plate contact

Seismic data from deep refraction and wide-angle reflection profiles intersecting the Western Carpathians show distinct upper-mantle Pn phases with anomalous apparent velocities identified in the first and later arrivals. Their systematic analysis indicates that such phases are present in numerous seismic sections both for in-line and off-line shots. They are observed in data from profiles intersecting the Carpathians in the west at the contact with the Bohemian Massif; similar feature was also found in data at the northern edge of the Carpathians at the contact with the North European Platform. Modelling of these anomalous Pn phases shows that they originate due to local structural anomalies of the Moho discontinuity detected in several places along the Western Carpathian arc. Such anomalies are located in close lateral proximity of the Pieniny Klippen Belt representing the contact between the stable European Plate in the north and the ALCAPA (Alpine–Carpathian–Pannonian) microplate in the south. Thus, the complex local Moho topography modelled from the Pn phases suggests tectonic relation to the formation of the Carpathian orogen. The result is supported by correlation with the large-scale Carpathian conductivity anomaly modelled in the Carpathians at a mid-crustal level. Relative lateral position of these two structures together with the Pieniny Klippen Belt at the surface delineates a zone affected by deformations at various depths along the whole Western Carpathian arc.

2B31 Steering Control without Using Measurement of Lateral Velocity of Combination Vehicle(The 12th International Conference on Motion and Vibration Control)

In this paper, an adaptive steering controller for combination vehicles is proposed with using the wheel steering of semitrailer, the front and rear wheel steering of tractor without the measurement of lateral velocity of vehicle. The developed controller does not require any accurate knowledge of all vehicle parameters. The relative lateral position is measured and the controller is designed without using lateral velocity measurements. At first, we propose a new dynamic expression suitable for the design of a stable adaptive steering controller without using the lateral velocity. Next, we develop an ideal vehicle model as the reference vehicle model. In order to realize that the ideal vehicle model can have a good steering performance even when the drivers' steering characteristics vary, an evaluation function is introduced. Then, an ideal vehicle model is developed by using a trail and error approach so that the value of the evaluation function for the ideal vehicle model becomes smaller compared with that for the passive vehicle. At last, we develop an adaptive steering controller so that the behavior of the actual combined vehicle can track that of the ideal vehicle model. The effectiveness of the proposed steering controller is verified via computer simulations.

A Self-separation Algorithm using Relative Speed for a High-density Air Corridor

Self-separation algorithms in a high density air corridor are discussed. The air corridor is considered to be a tube or band shaped airspace connecting congested airports, high demand city area etc. In the corridor, only aircraft capable of self-separation are allowed to fly in the same direction. An appropriate self-separation algorithm is indispensable for the safety and high traffic throughput. In this paper, a self-separation algorithm that leads aircraft to determine its heading change direction according to the relative speed is newly introduced in addition to a basic air corridor self-separation algorithm. The basic algorithm refers to the relative lateral position of aircraft for conflict avoidance based on the assumption that all aircraft intend to fly along the corridor. The algorithm leads the aircraft to change their heading angles. Through numerical traffic simulations, the algorithm based on the relative speed leads the aircraft to form groups consisting of aircraft with similar speed. It has been clarified that the safety and efficiency have been considerably improved.

Development of objective discomfort evaluation indicators for a task-oriented motion using less constrained motion concept: application to automotive pedal clutching task

This paper presents a method to develop objective discomfort evaluation indicators for a task oriented motion using the concept of less constrained movement. The basic idea is to compare imposed and less constrained movements in order to identify relevant biomechanical parameters for defining objective discomfort indicators. The task of automotive pedal clutching was chosen for illustrating the proposed method. Based on discomfort questionnaire and motion analysis of the experimental data, four discomfort indicators were proposed. Two of them were based on the ankle joint angle around flexion/extension axis at the beginning and the end of the clutch pedal depression. The third one was defined using knee flexion/extension joint torque at the end of the clutch pedal depression. The last indicator was defined as the relative lateral position of the heel compared to the average pedal lateral position for less constrained configurations. A global discomfort function was also defined as a weighted sum of all indicators. Globally, the proposed global discomfort indicator succeeded in differentiating the tested configurations in agreement with experimental observation. As expected, less discomfort rating is obtained for less constrained movement when compared with the corresponding imposed one.

Hyperelastic pressure sensing with a liquid-embedded elastomer

A hyperelastic pressure transducer is fabricated by embedding silicone rubber with microchannels of conductive liquid eutectic gallium–indium. Pressing the surface of the elastomer with pressures in the range of 0–100 kPa will deform the cross-section of underlying channels and change their electric resistance by as much as 50%. Microchannels with dimensions as small as 25 µm are obtained with a maskless, soft lithography process that utilizes direct laser exposure. Change in electrical resistance is measured as a function of the magnitude and area of the surface pressure as well as the cross-sectional geometry, depth and relative lateral position of the embedded channel. These experimentally measured values closely match closed-form theoretical predictions derived from plane strain elasticity and contact mechanics.

Ab initiostudy on the surface chemistry and nanotribological properties of passivated diamond surfaces

Experimental findings indicate that the impressively low friction and wear of diamond in humid environments are determined by the surface passivation. In this paper, we investigate the relationship between the surface chemistry and the nanotribological properties of diamond surfaces. We consider the $(2\ifmmode\times\else\texttimes\fi{}1)\text{-C}(001)$ surface taking into account different terminations constituted of hydrogen, oxygen, and hydroxyl groups. We analyze the adsorbate geometry and the polarization of the surface bonds. We discuss the stability of the different surface terminations in different conditions, which account for the presence in the environment of ${\text{H}}_{2}$, ${\text{O}}_{2}$, and ${\text{H}}_{2}\text{O}$ molecules in different concentrations and we present the surface phase diagram. Finally, we report the calculated adhesion energy between the passivated surfaces and analyze its variation as a function both of the surface separation and of the surface relative lateral position. In this way, we provide information on the effect of the different adsorbates on the interaction between diamond surfaces and on the magnitude and anisotropy of friction forces.

NOVEL PELLICLE SURFACE PATTERNS ON EUGLENA OBTUSA (EUGLENOPHYTA) FROM THE MARINE BENTHIC ENVIRONMENT: IMPLICATIONS FOR PELLICLE DEVELOPMENT AND EVOLUTION(1).

Euglena obtusa F. Schmitz possesses novel pellicle surface patterns, including the greatest number of strips (120) and the most posterior subwhorls of strip reduction in any euglenid described so far. Although the subwhorls form a mathematically linear pattern of strip reduction, the pattern observed here differs from the linear pattern described for Euglena mutabilis F. Schmitz in that it contains seven linear subwhorls, rather than three, and is developmentally equivalent to three whorls of exponential reduction, rather than two. These properties imply that the seven-subwhorled linear pattern observed in E. obtusa is evolutionarily derived from an ancestral bilinear pattern, rather than from a linear pattern, of strip reduction. Furthermore, analysis of the relative lateral positions of the strips forming the subwhorls in E. obtusa indicates that (1) the identity (relative length, lateral position, and maturity) of each strip in any mother cell specifies that strip's identity in one of the daughter cells following pellicle duplication and cell division, (2) the relative length of any given pellicle strip regulates the length of the nascent strip it will produce during pellicle duplication, and (3) pellicle pores develop within the heels of the most mature pellicle strips. These observations suggest that continued research on pellicle development could eventually establish an ideal system for understanding mechanisms associated with the morphogenesis and evolution of related eukaryotic cells.

Least Squares Method Applied to Rail Vehicle Contact Condition Monitoring

Abstract The dynamics of a railway vehicle are driven by the geometry and conditions at the wheel-rail contact. Typically the condition and shape of the wheel and rail are monitored separately and off-line. The work presented here is part of ongoing research into on-line model-based estimation of parameters in the wheel-rail contact dynamics. This paper outlines a practical approach to estimating a nonlinear function within a dynamic system by using a piecewise cubic functions. The parameters for the cubic functions are estimated with a least squared approach applied to the dynamic measurements taken from the system. A simplified plan-view wheelset and suspended mass model is introduced to use as an application of this technique. A contact geometry term, conicity, which is a nonlinear function of the relative lateral wheel-rail position, is included in the rail vehicle model. The conicity is successfully estimated using the least-squares method outlined in the paper.

Feedback based simultaneous correction of imaging artifacts due to geometrical and mechanical cross-talk and tip-sample stick in atomic force microscopy

This paper presents a feedback scheme that simultaneously corrects, in real time, for the imaging artifacts caused by cantilever and photosensor misalignments as well as misinterpretations in relative lateral position of the tip with respect to the sample due to the tip-sample stick in atomic force microscopy (AFM). The optical beam bounce method, typically used in AFM for imaging, is sensitive to inaccuracies of cantilever geometry and the relative misalignment of the laser source, cantilever, and the laser sensitive diode from the intended design. These inaccuracies, which contribute to the geometrical cross-talk between the normal and the lateral signals, become prominent at the atomic and subnanometer scales, and thereby impede high resolution imaging studies. The feedback scheme accounts for these artifacts and makes imaging insensitive to, in fact, practically independent of these inaccuracies. This scheme counteracts the lateral twisting dynamics of the cantilever, and as a result, it avoids the misinterpretation problem of the relative lateral position of the cantilever tip from the sample and thereby avoids the corresponding imaging artifacts that are typically prominent in contact mode friction force microscopy (FFM). The feedback scheme consists of simultaneously regulating the normal as well as the lateral cantilever deflection signal at their respective set points. This not only removes the imaging artifacts due to geometrical misalignments, mechanical cross-talk, and irregular sliding but also the corresponding compensatory control signal gives a more accurate real time measure of the lateral interaction force between the sample and the cantilever as compared to the lateral deflection signal used in FFM. Experimental results show significant improvement, and in some cases, practical elimination of the artifacts. The design and implementation of a split piezoassembly needed for the lateral actuation for the feedback scheme are also presented.

Robust disturbance rejection via P-D state feedback Example for lane keeping of highway vehicles

The problem of robust disturbance rejection (RDR) using a Proportional plus Derivative (P-D) state feedback controller is studied for the case of single-input single output (SISO) linear systems with nonlinear uncertain structure. The linear systems are considered to be subjected to nonmeasurable disturbances. Sufficient conditions for the problem to have a solution are established. A family of P-D feedback controllers solving the problem is analytically determined. Sufficient conditions for the solution of the RDR problem with simultaneous robust stability are also established. Furthermore, the latter problem together with normality and asymptotic command matching is solved. The problem of lane keeping of highway vehicles was the motive for the derivation of all the above results. In particular, the problem of zeroing the relative lateral position of a vehicle travelling along a highway is formulated here as an RDR problem. The curvature of the road plays the role of the unknown disturbance. The problem of rejecting robustly the influence of the road curvature to the lateral position is proved to be always solvable, using a P-D feedback controller. The controller is analytically determined using a finite step algorithm. Furthermore, the free responses of the vehicle’s relative lateral position and lateral velocity are proved to be expressed only in terms of arbitrary modes. The general set of P-D feedback controllers solving the problem is proved also to guarantee robust stability of the closed-loop system. Using the infinity norm, the good performance of the rest of the vehicle’s variables, namely the yaw angle, the yaw rate and the front steering angle, is proved. Simulation results illustrate the good performance of the RDR over a wide range of system uncertainties and measurement errors.