Trajectory Measurements Research Articles

A Multi-Point Distance-Bounding Protocol for Securing Automatic Dependent Surveillance-Broadcast in Unmanned Aerial Vehicle Applications

The Automatic Dependent Surveillance-Broadcast (ADS-B) protocol is being adopted for use in unmanned aerial vehicles (UAVs) as the primary source of information for emerging multi-UAV collision avoidance algorithms. The lack of security features in ADS-B leaves any processes dependent upon the information vulnerable to a variety of threats from compromised and dishonest UAVs. This could result in substantial losses or damage to properties. This research proposes a new distance-bounding scheme for verifying the distance and flight trajectory in the ADS-B broadcast data from surrounding UAVs. The proposed scheme enables UAVs or ground stations to identify fraudulent UAVs and avoid collisions. The scheme was implemented and tested in the ArduPilot SITL (Software In The Loop) simulator to verify its ability to detect fraudulent UAVs. The experiments showed that the scheme achieved the desired accuracy in both flight trajectory measurement and attack detection.

Precision survey of the readout strips of small-strip Thin Gap Chambers using X-rays for the muon spectrometer upgrade of the ATLAS experiment

The instantaneous luminosity of the Large Hadron Collider (LHC) will be increased by a factor of 5 to 7 after a series of upgrades of the CERN accelerator complex. In anticipation to the increased collision rate at the interaction point, the muon end-cap inner station of the ATLAS detector will be replaced with the so-called New Small Wheels (NSWs) during the LHC shutdown of 2019/2020. The NSWs combine the Micromegas and small-strip Thin Gap Chambers (sTGC) technologies. The sTGC detector modules are arranged in trapezoid wedges of 4 detector planes with total active areas varying between 3 and 5 m2 per plane. Over 1000 azimuthal cathode strips are read out on each plane for precision muon trajectory measurements. The positioning of individual strips must be known to within 100 microns to satisfy the performance targets of this ATLAS upgrade. Non-conformities of the sTGC strip-pattern are therefore measured on finished wedges using an X-ray gun precisely positioned at reference points. The working principles and the spatial resolution measurement of this technique are presented.

A Wireless Trajectory Measurement System for Unicondylar Knee Arthroplasty

During unicondylar knee arthroplasty surgery, the tibial prosthesis is fixed and the angle of distal femoral prosthesis relative to the prosthetic gasket is changed to generate the force line trajectory, which is important for doctors to judge the appropriate position of the implants. In this article, we propose a wireless force line trajectory measurement system for unicondylar knee arthroplasty, which includes the pressure sensors array, the control and processing data circuits, the radio frequency transmitter, and the data recorder. Data from 20 sensors are processed and transmitted wirelessly, and the force line trajectory is displayed on the screen in real time. The least squares fitting algorithm is proposed, with which we obtain the pressure distribution, the maximum pressure points, and the force line trajectory. We adopt field programmable gate array to implement the algorithm with lower-upper decomposition to fit the trajectory faster and transmit less data to save power. The average current consumption of the system is 1.37 mA in the operating mode. Dimensions of the data transmission module are length 70 mm, width 35 mm, and height 4 mm. The total uncertainty of the system measurement force line trajectory is 0.92 mm. Experimental results show that the system meets the requirement of real-time measurement of the force line trajectory during the surgery.

Measurement and calculation of particle trajectory of liquefied soil under wave action

In offshore areas, the silty soil seabed can be liquefied under cyclic wave loads, and the liquefied soil fluctuates with the upper water body with the same period. Similar to the movement of water, the fluctuation orbit of liquefied soil particles is elliptical with a horizontal major axis, and the orbit radius gradually decreases with depth. Although some researchers have constructed theories to describe the fluctuation of liquefied soils, no corresponding data have been verified in wave flume tests on silty soils under visual conditions. In this paper, the particle trajectory of liquefied soil is observed to be elliptical under the condition of small-amplitude waves in shallow water by wave flume tests. The vertical displacement of liquefied soil particle motion is measured by the falling ball method, which provides validation data for the theoretical calculation results. In addition, the results of the double-layer fluid wave theory are compared with the experimental data. For engineering applications, an analytical solution for particle motion and the displacement of liquefied silty soil under wave action is given by using the small-amplitude wave theory and the method of setting a reference surface of fluid wave depth. The vertical displacement of liquefied soil particles calculated by the analytical solution is smaller than that calculated by the double-layer fluid wave theory and larger than that calculated from the experimental results.

Measurement of Spatial Stability in Precision Grip.

The purpose of the protocol is to indirectly evaluate the direction of the finger force during manipulation of a handheld object based on the biomechanical relationships in which deviated force direction causes center of pressure (COP) replacement. To evaluate this, a thin, flexible, and high spatial resolution pressure sensor sheet is used. The system allows measurement of the COP trajectory in addition to the force amplitude and its temporal regulation. A series of experiments found that increased trajectory length reflected a sensorimotor deficit in stroke patients, and that decreased COP trajectory reflects a compensatory strategy to avoid an object slipping from the hand grip in the elderly. Moreover, the COP trajectory could also be decreased by dual task interference. This article describes the experimental procedure and discusses how finger COP contributes to an understanding of the physiology and pathophysiology of grasping.

Vision-Based Measurement and Prediction of Object Trajectory for Robotic Manipulation in Dynamic and Uncertain Scenarios

Vision-based measurement and prediction (VMP) are the very important and challenging part for autonomous robotic manipulation, especially in dynamic and uncertain scenarios. However, due to the potential limitations of visual measurement in such an environment such as occlusion, lighting, and hardware limitations, it is not easy to acquire the accurate positions of an object as the observations. Moreover, manipulating a dynamic object with unknown or uncertain motion rules usually requires an accurate prediction of motion trajectory at the desired moment, which dramatically increases the difficulty. To address the problem, we propose a time granularity-based vision prediction framework whose core is an integrated prediction model based on multiple [i.e., long short-term memory (LSTM)] neural networks. At first, we use the vision sensor to acquire raw measurements and adopt the preprocessing method (e.g., data completion, error compensation, and filtering) to turn raw measurements into the standard trajectory data. Then, we devise a novel integration strategy based on time granularity boost (TG-Boost) to select appropriate base predictors and further utilize these history trajectory data to construct the high-precision prediction model. Finally, we use the simulation and a series of dynamic manipulation experiments to validate the proposed methodology. The results also show that our method outperforms the state-of-the-art prediction algorithms in terms of prediction accuracy, success rate, and robustness.

Magnus force of rotating microscopic magnetic particles

Dropping the particles in fluids in the presence of a rotating magnetic field, researchers deduce force from trajectory measurements for particles as small as 80 μm.

Visualization of two-dimensional liquid sheets issued into subsonic gaseous crossflow

Flow dynamics of two-dimensional liquid sheets discharged into low-speed gaseous crossflow were experimentally investigated. The flow characteristics of liquid sheets were visualized by taking advantage of diffused backlight shadowgraphy and high-speed photography. Three injectors with an equal thickness of 0.35 mm and aspect ratios of 30, 60 and 90 were manufactured and tested at different flow conditions. A full discussion about the flow characteristics of two-dimensional liquid sheets in the presence of transverse airflow is provided. Visualizations revealed that the liquid sheets represented a unique concave-like structure that was named as inflated sheet. This special characteristic was not previously seen on any other circular or non-circular liquid jets and therefore made the flow dynamics of liquid sheets in subsonic crossflow very distinguished. The inflated sheet was found to transform from an enclosed structure into an open structure. The open inflated sheet was disturbed by different breakup mechanisms including sheet rupture, bag breakup, and Rayleigh–Taylor instability. Based on the observed phenomena, the flow was grouped into five regimes including biconvex, enclosed inflated sheet, open inflated sheet, bag breakup/sheet rupture, and multimode breakup. Furthermore, it was found that the droplet region was bifurcated due to the different breakup mechanisms acting simultaneously upon the sheet. Measurements of sheet trajectory were performed and the effects of momentum ratio and Weber number were studied. It was found that Weber number was only effective at low values, while momentum ratio remarkably impacted the trajectory.

PROBLEMS OF DIFFERENTIAL AND TOPOLOGICAL DIAGNOSTICS. PART 5. THE CASE OF TRAJECTORIAL MEASUREMENTS WITH ERROR

Proposed work is the fifth work of the cycle on differential and topological diagnostics. The article gives an estimate of the errors method of direction fields in the case of not accurate trajectory measurements, but trajectory measurements with an error are limited by the modulus of a given a smooth function of time, and in case this error is a random variable distributed according to the normal law with fixed parameters. We show that in these more complex cases, you can specify the best number of required trajectory measurements, inwhich the proposed algorithms of diagnostics will work constructively, and the malfunction will be determined unambiguously.

Determining the Orbit Onboard a Space Vehicle

Methods and algorithms for determining the orbit of a space vehicle onboard using the measurements of global navigation satellite (NS) systems are considered. Methods and algorithms for obtaining radio navigation measurements in the case of the highly dynamic orbital motion are described. The celestial mechanics interpretation of measurements is given. Algorithms for the three-phase processing of trajectory measurements that improve the reliability and accuracy of determining the orbit are proposed. A mathematical model of a simulator of the satellite navigation signals is developed. The computational results are presented.

Additive Manufacturing of Conformal Microstrip Antenna Using Piezoelectric Nozzle Array

Inkjet printing technology is widely used in the manufacture of conformal structures, such as load-bearing antennas or frequency-selective surface radomes. It is particularly promising for preparing conductive patterns on non-developable surfaces. Existing printing technologies employ a single nozzle and a five-axis linkage technique for printing, which is time-consuming. In this study, a conformal plane printing technology based on the arrayed nozzle was developed to prepare conductive patterns on a non-developable surface. The technique actualizes fast printing of passive circuits on a conformal surface, such as a microstrip antenna. Compared to printing techniques employing a single nozzle, the proposed method greatly improves the printing efficiency on conformal surfaces. Specifically, we first developed a model for the driver waveforms and the printing injection parameters via simulation. Subsequently, the accuracy of the computational fluid dynamic simulation results was validated by comparing them with the experimental measurements of droplet trajectory captured using a camera. Next, a droplet spreading model was established, considering energy conservation principles. Finally, a conformal surface printing technology using arrayed nozzles was developed based on the injection parameter and droplet spreading models. The effectiveness and feasibility of the proposed printing method were further validated via simulation and experimental tests of return loss.

Hand dexterity assessment based on mouse pointer trajectory measurements in children with learning disabilities

We present an investigation of the systematic differences in upper limb motor skills between children with learning disabilities (LDs) and children without LDs. The study comprised point-and-click experiments, one-dimensional (1D), and two-dimensional (2D), conducted with mouse and joystick. Eighty (80) children with LDs and forty-six (46) children without LDs participated in the experiments. We utilized our input device evaluation application (IDEA) system to track the mouse pointer and calculate ten trajectory parameters: movement time, index of difficulty, throughput, movement variability, missed clicks, movement direction change, target re-entry, movement offset, task axis crossing, and movement error. The statistical analysis of the mouse pointer trajectory parameters using the hierarchical logistic regression model detected the children with LDs with a 70% success rate in the 2D experiment with the mouse.

THE OPTIMIZATION METHOD OF FUZZY AUTOMATIC CLASSIFICATION IN THE PROBLEM OF COMBINING THE ASSESSMENTS OF TRAJECTOR MEASUREMENTS IN THE RADAR SYSTEM

The paper describes the application of the optimization method of fuzzy automatic classification in the problem of combining estimates of trajectory measurements in a radar system. By a radiolocation system the author mean an automated hierarchical technical complex that combines, using communication tools, a set of asynchronously functioning radiolocation tools, as well as central and intermediate points that collect, process and issue trajectory radiolocation information. It must be borne in mind that in conditions of tracking tight groups of air targets, with relatively small intervals and distances, it is not always possible to obtain trajectory information of the required quality. The main reason for this is the difficulty in determining the values of the correlation matrices of errors in estimating the parameters of the state vector of air targets. The task becomes more complicated as the number of intermediate processing points increases when it is brought to the final consumer. The main goal of the article is to increase the accuracy of estimates of trajectory measurements in a radiolocation system. The research is done by means of the mathematical tool of fuzz-set theory, namely, by optimizing fuzzy automatic classification. The article demonstrates that using fuzzy automatic classification under a priori parametrical uncertainty in the law of trajectory measurement errors, when determining weight coefficients, can improve the accuracy of estimates in these conditions up to 30 % compared with methods based on the application of the probabilistic approach. The results obtained allow us to justify the prospects of using optimization methods of fuzzy automatic classification in the tasks of processing trajectory information. In addition, the advantage of the proposed method is its low computational complexity and ease of implementation, which is especially important while maintaining a large number of airborne objects.

Design and applications of drilling trajectory measurement instrumentation in an ultra-deep borehole based on a fiber-optic gyro

Abstract. The working environment in hot dry rock boreholes, encountered in deep geothermal investigation drilling and ultra-deep geological drilling (up to 5000 m), is very difficult at the present stage. We have developed a drilling trajectory measuring instrumentation (DTMI), which is based on the interference fiber-optic gyro (FOG). This can work continuously, for 4 h, in an environment where the ambient temperature does not exceed 270 ∘C and the pressure does not exceed 120 MPa. The DTMI is mainly divided into three parts: an external confining tube, a metal vacuum flask, and a FOG measurement probe. Here, we focus on the mechanical design, strength, and pressure field simulation analysis for the external tube, the structural design and temperature field simulation analysis for the vacuum flask, and the FOG Shupe error analysis and compensation in the temperature field. Finally, through the engineering applications of the SK-2 east borehole of the China Continental Scientific Drilling (CCSD) project and the geothermal well of Xingreguan-2, the data measurements of the drilling trajectory were used to analyze the stability of the DTMI. The instrument realizes long-duration, high-stability work in the process of making trajectory measurements in an ultra-deep hole. The instrument has the characteristic of anti-electromagnetic interference and enables work to be carried out in the blind zone of existing technologies and instrumentation. Therefore, DTMI has great potential in the promotion and development of geological drilling technology.

Paths of the cervical instantaneous axis of rotation during active movements-patterns and reliability.

The instantaneous helical axis (IHA) is a characteristic of neck movement that is very sensitive to changes in coordination and that has potential in the assessment of functional alterations. For its application in the clinical setting, normative patterns must be available, and its reliability must be established. The purpose of this work is to describe the continuous paths of the IHA during cyclic movements of flexion-extension (FE), lateral bending (LB), and axial rotation (AR) and to quantify their reliability. Fifteen healthy volunteers participated in the study; two repetitions were made on the same day (by different operators) and over an 8-day interval (by the same operator) to evaluate the inter-operator and inter-session reliability, respectively. The paths described by the IHA suggest a sequential movement of the vertebrae in the FE movement, with a large vertical displacement (mean, 10cm). The IHA displacement in LB and AR movements are smaller. The paths described by the IHAs have a very high reliability for FE movement, although it is somewhat lower for LB and RA movements. The standard error of measurement (SEM) is less than 0.5cm. These results show that the paths of the IHA are reliable enough to evaluate changes in the coordination of intervertebral movement. Graphical abstract A video photogrammetry system is used to record the cyclic movements of the neck, from which the continuous trajectories of the associated instantaneous helical axis (IHA) are calculated. We have analyzed the movements of flexion-extension (FE), lateral flexion (LB), and axial rotation (AR) for a sample of 15 healthy subjects. The measurements have been repeated with two different operators (in the same session) and in two separate sessions (same operator). IHA displacement patterns have been obtained in each movement, and the reliability of the measurement of such IHA trajectories has been estimated.

Measurement of the Coordinates of Radio Emission at High Frequencies by Goniometric and Goniometric-Range Finding Methods

The coordinates of radio emission sources at high frequencies are measured using a two-position system of azimuthal-meridional direction finders by a goniometric method. Active antenna lattices of vertical vibrators and synchronized coherent radio receivers with frequency conversion are used in the direction finder stations. The amplitude and phase discrepancies are minimized by preliminary calibration of the receiver channels at the frequencies of the direction finder signals. The measurement results are used to study the mean square deviations of the radio source coordinates for emission of the type for meteorological information from airport networks in the Russian Federation and neighboring countries, radio stations with standard frequencies and times, and telecoded and continuous transmissions. The attainable accuracy of the measurements is analyzed as a function of spatial position of the direction finders, path lengths, and fluctuations in the electrical parameters and spatial distribution of the ionized layers of the atmosphere leading to changes in the beam trajectories and anomalous errors in measurements of the ray trajectories and anomalous errors in measurements of the directions of arrival of the radio waves at different times of the year and day. It is shown that in the lower part of the high frequency band the error in measuring the coordinates of the radio sources by the goniometric system is 4.7%, and that as the frequency approaches the upper boundary this indicator increases by a factor of 1.2. Range finding of signals at a single point in space and measuring the height of the layers of the atmosphere using vertical ranging stations yields coordinates of the radio sources by the goniometric-range finding method. Measurements of the coordinates of objects by the goniometric-range finding method can be carried out with a mean square deviation equal to 11–13% of the distance.

Is abdominal vascular calcification score valuable in predicting the occurrence of colorectal anastomotic leakage? A meta-analysis.

Anastomotic leakage (AL) is a catastrophic surgical complication affecting the prognosis of patients after colorectal surgery. We aimed to determine the value of the arterial calcification (AC) score in predicting AL. Medline and Embase were searched through November 2019. The odds ratio (OR) and 95% confidence interval (CI) were used to estimate the association between AC and AL after colorectal surgery. The fixed-effects model or random-effects model was adopted for data pooling. Subgroup analyses were conducted to assess the effect of different aortoiliac trajectories. Four studies involving 496 patients were included. The calcium volume and calcium score measurements of different trajectories revealed a significant difference with regard to the left and right common iliac arteries, the superior mesenteric artery, and the left common iliac artery. Calcification of the internal iliac artery significantly increased the risk of AL compared with no AL (OR = 1.005; 95% CI 1.002-1.009; P = 0.005), as did calcification of the left internal iliac artery (OR = 1.009; 95% CI 1.002-1.016; P = 0.011), but not of the common iliac artery (OR = 1.001; 95% CI 1.000-1.001; P = 0.317) or common and internal iliac artery (OR = 1.000; 95% CI 1.000-1.000; P = 1.000). AC is associated with increased risk of AL following colorectal surgery. CRD42019141236.

Development of Portable Shallow Hole Inclinometer in Coal Mine

Due to the special requirements of borehole measurement work in coal mines, in this paper, a portable shallowhole inclinometer is developed in response to the current situation of shallow borehole trajectory measurement relying on the pushing of drilling machine. This instrument is mainly composed by three parts of inclinometerprobe tubes, orifice display controllers, and conveying rods. The probe tube can be used to measure the attitude parameters such as the inclination, azimuth and tool facing angle of the borehole, and the orifice display controller works synchronously and records the drilling depth and measuring time.Finally, the track of the current borehole can be displayed in the mine. The test results show that the instrument is stable, reliable, and practical.

Australian Lidar Measurements of Aerosol Layers Associated with the 2015 Calbuco Eruption

The Calbuco volcano in southern Chile (41.3° S, 72.6° W) underwent three separate eruptions on 22–23 April 2015. Following the eruptions, distinct layers of enhanced lidar backscatter at 532 nm were observed in the lower stratosphere above Buckland Park, South Australia (34.6° S, 138.5° E), and Kingston, Tasmania (43.0° S, 147.3° E), during a small set of observations in April–May 2015. Using atmospheric trajectory modelling and measurements from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) space-borne lidar and the Ozone Mapping Profiler Suite (OMPS) instrument on the Suomi National Polar-orbiting Partnership (NPP) satellite, we show that these layers were associated with the Calbuco eruptions. Buckland Park measurements on 30 April and 3 May detected discrete aerosol layers at and slightly above the tropopause, where the relative humidity was well below saturation. Stratospheric aerosol layers likely associated with the eruptions were observed at Kingston on 17 and 22 May in narrow discrete layers accompanied by weaker and more vertically extended backscatter. The measurements on 22 May provided a mean value of the particle linear depolarisation ratio within the main observed volcanic aerosol layer of 18.0 ± 3.0%, which was consistent with contemporaneous CALIOP measurements. The depolarisation measurements indicated that this layer consisted of a filament dominated by ash backscatter residing above a main region having likely more sulfate backscatter. Layer-average optical depths were estimated from the measurements. The mean lidar ratio for the volcanic aerosols on 22 May of 86 ± 37 sr is consistent with but generally higher than the mean for ground-based measurements for other volcanic events. The inferred optical depth for the main volcanic layer on 17 May was consistent with a value obtained from OMPS measurements, but a large difference on 22 May likely reflected the spatial inhomogeneity of the volcanic plume. Short-lived enhancements of backscatter near the tropopause of 17 May likely represented the formation cirrus that was aided by the presence of associated volcanic aerosols. We also provide evidence that gravity waves potentially influenced the layers, particularly in regard to the vertical motion observed in the strong layer on 22 May. Overall, these observations provide additional information on the dispersal and characteristics of the Calbuco aerosol plumes at higher southern latitudes than previously reported for ground-based lidar measurements.

Razvoj metode za utvrđivanje veličine zazora u kliznim ležajevima

Introduction/purpose: The purpose of this paper is to present the importance of applying a new diagnostic method with a monitoring system and its capability to reliably determine when and where the problem will occur related to the wear of plain bearings in further operation of the plant, to offer a quality assessment of how the system will continue to function over time, to predict causes of failures and how to eliminate them as well as to provide time for planned maintenance of technical systems. Method: The new method solves the problem of sliding bearing diagnostics by measuring the dynamic trajectories (orbit) of the sleeve in the sliding bearing. Modern methods of technical diagnostics based on the measurement of dynamic parameters and electrical quantities and their analysis enable the support of measuring systems and measurement sensors from different manufacturers. Results: Measurements of the dynamic trajectories of sleeves in sliding bearings determine the values characterizing: normal condition, initial clearance size, further clearance increase, bearing clearance sizes, the moment when the state parameters are close to the upper limit of the allowable clearance, and the specific clearance size when further plant exploitation can cause system failure. Conclusion: The new diagnostic method and monitoring systems can be widely applied in all technical fields: internal combustion engines, hydroelectric power plants, thermal power plants, process plants, and in many other areas. Many monitoring systems, compatibility of devices and equipment of different manufacturers are supported by hardware and software. The calculations of theoretical and experimental dynamic parameters were verified. The method has a wide range of possibilities of application.