Altitude Of Vehicle Research Articles

Comparison of Human-Drone Distancing Studies Across In-person and Online Modalities

Human-robot proxemics behaviors can vary based on personal, robot, and environmental factors which, along with their deployment in public-facing interactions, calls for an in-depth exploration. This paper explores the impact of altitude and safety modifications of small unmanned aerial vehicle (sUAV) on users’ comfortable interaction distance. By leveraging interaction techniques from literature like video, sound, and simulations, we explore personal space interactions in online studies (N=376) with the sUAV and the Double telepresence robot. We then compare the findings with our in-person interaction data (N=47). While in-person interactions are the ultimate goal, online methods can be used to reduce resources, allow larger sample sizes, and may lead to a more comprehensive sampling of population than would be expected from in-person studies. The lessons learned from this work are applicable broadly within the social robotics community, even outside those who are interested in proxemics interactions, to conduct future crowd-sourced experiments. The various modalities provided similar trends when compared with data from in-person studies. While the distances may not have been precise compared to those measured in the real world, these experiments are useful to detect patterns in human-robot interactions, and to conduct formative studies before committing resources to in-person testing.

Evaluation of Radio Frequency Identification Power and Unmanned Aerial Vehicle Altitude in Plant Inventory Applications

In the business of growing and selling ornamental plants, it is important to keep track of plants from nursery to distribution. Radio Frequency Identification (RFID) technology provides an easier tracking method for inventories of plants by attaching tags with unique identifiers. Due to the vast area of most nurseries, there is a need to have an efficient method of scanning RFID tags. This paper investigates the use of drones and RFID, specifically, the effects of RFID reader power and flight altitude on tag counts. The experimental setup evaluated three RFID reader power levels (15 dBm, 20 dBm, and 27 dBm), three flight altitudes (3 m, 5 m, and 7 m), the number of passes (one or two), and two plant types (‘Green Giant’ arborvitae and ‘Sky Pencil’ holly). For RFID tags, four types were used (L5, L6, L8, and L9), with two antenna types (dog-bone and square-wave) and two attachment types (loop-lock and stake). For each power level, the UAV was flown to three different altitudes of 3 m, 5 m, and 7 m above the ground. At each altitude, two scan passes were performed at a constant speed of approximately 1.5 m/s. Each plot of plants (two in total) was randomly tagged with a total of 40 RFID tags per plot. Field data were collected from September to December 2023 (on a total of eight dates). The data showed that a power level of 15 dBm and an altitude of 3 m yielded a tag count of 53%, while counts of 34% and 16% were achieved at 5 m and 7 m, respectively. At 20 dBm and an altitude of 3 m, the count accuracy across all tag types and both plants was 90%. When the altitude was increased to 5 m and 7 m, tag-count accuracy dropped to 75% and 33%, respectively. The highest count accuracy was observed at 27 dBm and an altitude of 3 m, with a reading accuracy of 98%. Tag types L6 and L9 performed better at any power level and altitude, while L5 and L8 performed well at a higher power level and lower altitude. In this experiment, canopy properties (size and shape) had no effect on the number of tags read. This study aimed to evaluate the RFID power and UAV altitude achieving the highest accuracy in scanning the RFID tags. Furthermore, it also assessed the effects of plant growth on the scanning efficiency and accuracy of the system.

Evaluation of Doppler Effect Error Affecting the Radio Altimeter Altitude Measurements

The measurement of the real altitude of aircraft is usually done using an aviation radio altimeter (ALT). A radio altimeter provides crucial information about the instantaneous (radio) altitude of aircraft, helicopter, or unmanned aerial vehicle, to the pilot or another assistance system, such as an autopilot or an anti-collision system. However, this flight altitude measurement is affected by several errors, methodological errors and the operating frequency and modulation parameters instability, or the Doppler shift error. This article is focused on the evaluation of how the Doppler effect error develops during the operation of an ALT and its potential use as an information carrier concerning a possible loss of radio altitude, leading to dangerous situations. This paper briefly explains in a theoretical and practical way how this error develops and how it can affect the process of creation of height impulses. Practical experiments were conducted and evaluated in this research, and a theoretical design of a simple circuit capable of signalization of radio altitude loss presented. As the Doppler shift error was previously recognized solely as a measurement error, it could be used in a new function as a source of supplemental warning information.

Adaptive estimation of UAV altitude in complex indoor environments using degraded and time-delayed measurements with time-varying uncertainties

A novel approach for robust Unmanned Aerial Vehicle (UAV) altitude estimation relying on laser measurements that is designed for use in complex indoor environments is proposed in this paper. Specifically, we aim to design a system with general usability inside multi-floor buildings. The multi-floor buildings are characterized by areas lacking distinct vertical geometric features to be used as reference by 3D Light Detection and Ranging (LiDAR) localization algorithms, and by areas with either flat floors or limited areas with inconsistent ground elevation. The proposed approach solves the problem of adaptive fusion of data from multiple sources with apriori-unknown confidence dependent on the current environmental properties. Whenever the environment contains enough geometric structure, altitude data from a 3D LiDAR-based Simultaneous Localization and Mapping (SLAM) algorithm are utilized. In environments that are too symmetrical for reliable SLAM operation, the approach relies mostly on measurements from a downward-facing 1D laser rangefinder, while simultaneously detecting inconsistent ground elevation areas. These measurements are fused with barometer data, Inertial Measurement Unit (IMU) data, and information from the UAV position controllers. Furthermore, our approach correctly handles the measurement delay caused by 3D LiDAR data processing that significantly differs from other sensor delays. The performance of the proposed approach has been validated in complex simulations and real-world experiments with the produced altitude estimate utilized in the control loop of the UAV. The proposed approach is released as open-source as part of the MRS UAV System.

The regional nanosatellite constellation modelling formation by a piggyback launch from different spaceports

The roadmap for constructing a regional nanosatellite constellation using the piggyback launch according to Chinese provider information has developed. For nanosatellite constellation formation to a specific purpose, it is necessary to analyse existing constellation operated similar tasks. Therefore, the software module for the Spire Global constellation orbital construction analysis was developed. The construction of Spire Global nanosatellites constellation based on orbital parameters database in the two-line element set format, satellite constellation databases and the developer site was analysed. A launch from the International Space Station and a piggyback launch were used for constellation formation. Nanosatellite deployment schemes, orbital parameters and flight parameters are investigated launches from the Taiyuan and Jiuquan Satellite Launch Centers with orbit inclination about 90°, that best correspond to the passes over Minsk (ϕ = 53°54′27″ N, λ = 27°33′52″ E) are analysed. The method of nanosatellite orbit preflight prediction at a passing launch has been developed. It involves a finding the nanosatellite state vector in the first flight day and at the time of constellation mission operate start. The launch time, satellite launch center coordinates, launch vehicle type, orbit inclination and altitude (period) are used in the method. In addition, the launch history and the satellite motion dynamics analysis on similar orbits is carried out. It was found that five launches are enough to organise a regional nanosatellite constellation with average radio visibility interruption time of at least 36 min with a maximum value of 85 min.

Sensitivity study of fiducial-aided navigation of Unmanned Aerial Vehicles

The possible applications and benefits of autonomous Unmanned Aerial Vehicle (UAV) use in urban areas are gaining considerable attention. Before these possibilities can be realized, it is essential that UAVs be able to navigate reliably and precisely in urban environments. The most common means of determining the location of a UAV is to utilize position measurements from Global Navigation Satellite Systems (GNSS). In urban environments, however, GNSS measurements are significantly degraded due to occlusions and multipath. This research analyzes the use of camera Line-of-Sight (LOS) measurements to self-describing fiducials as a replacement for conventional GNSS measurements. An extended Kalman filter (EKF) is developed and validated for the purpose of combining continuous measurements from an Inertial Measurement Unit (IMU) with the discrete LOS measurements to accurately estimate the states of a UAV. The sensitivity of the estimation error covariance to various system parameters is assessed, including IMU grade, fiducial placement, vehicle altitude, and image processing frequency.

Development and Validation of Generic Maneuvering Flight Noise Abatement Guidance for Helicopters

An extensive flight-test campaign has been conducted to look into developing actionable advice for pilots of today's vehicles to reduce their acoustic footprints. Ten distinct vehicles were tested at three different test ranges, with nine of the vehicles' data being documented here. Twelve pairs of turning conditions were tested to determine their effect on blade–vortex interaction noise. Each turning flight condition was evaluated using the peak A-weighted, band-limited (50–2500 Hz), sound pressure level measured throughout the maneuver. This metric was a surrogate for blade–vortex interaction (BVI) noise, and the difference between the peak values of each turning pair was investigated. That peak value difference was subsequently corrected by the offset from the intended vehicle altitude at turn initiation from the actual altitude at initiation. The corrected amplitudes were investigated and grouped into six validated actionable guidance principles that can be given to pilots to immediately reduce their acoustic footprint during operations. This generic guidance works by keeping the rotor well away from the wake throughout the maneuver, thus increasing miss distance and reducing the occurrence of objectionable BVI noise.

Adjustment mechanism with sliding mode for adaptive PD controller applied to unmanned fixed-wing MAV altitude

<p>This work presents an adjustment mechanism with the sliding modes technique to design a proportional derivative (PD) controller with adaptive gains. The objective and contribution are to design a robust adjustment mechanism in the presence of unknown and not modeled perturbations in the system; this perturbation can be considered wind gusts. The robust adjustment mechanism is designed with the MIT rule and the gradient method with the sliding mode theory. The adaptive PD obtained is applied to regulate unmanned fixed-wing miniature aerial vehicle (MAV’s) altitude.</p>

AL-TUNE: A Family of Methods to Effectively Tune UAV Controllers in In-flight Conditions

In the paper, a family of novel real-time tuning methods for an unmanned aerial vehicle (UAV) altitude controller in in-flight conditions. The methods allow the controller’s gains to be adapted only on the basis of measurements from a basic sensory equipment and by constructing the optimization cost function in an on-line fashion with virtually no impeding computational complexity; in the case of the altitude controller as in this paper for a hexacopter, altitude measurements were used only. The methods are not dependent on the measurement level, and present the approach in a generally applicable form to tuning arbitrary controllers with low number of parameters. Real-world experimental flights, preceded by simulation tests, have shown which method should behave best in a noisy environment when e.g. wind disturbances act on a UAV while it is in autonomous flight. As the methods can potentially be extended to other control loops or controller types, making this a versatile, rapid-tuning tool. It has been shown that a well-tuned controller using the proposed AL-TUNE scheme outperforms controllers that are tuned just to stabilize the system. AL-TUNE provides a new way of using UAVs in terms of adaptivity to changing their dynamic properties and can be deployed rapidly. This enables new applications and extends the usability of fully autonomous UAVs, unlike other tuning methods, which basically require the availability of a UAV model. The core difference with respect to other research from the field is that other authors either use a model of a UAV to optimize the gains analytically or use machine learning techniques, what increases time consumption, whereas the presented methods offer a rapid way to tune controllers, in a reliable way, with deterministic time requirements.

Distance Estimation Using Self-Induced Noise of an Aerial Vehicle

In this letter, we propose an algorithm to estimate the distance between an aerial vehicle and a large obstacle using the self-induced noise present during the vehicle's normal operation. We demonstrate the feasibility of using the proposed estimation method in real-time as a feedback mechanism to actively control the altitude of a blimp-like vehicle. The method is built upon a physics-based acoustic model of an unknown source emitting sound near an acoustically reflective surface. By placing two microphones beneath a motor-propeller system used to control the altitude of the vehicle, a real-time processing algorithm of the audio signals is presented that can accurately detect the distance from the microphones to the ground. The method is based upon computing the cross-correlation matrix of the signals on the two microphone channels. We develop a novel cross-correlation processor that is capable of filtering out the unknown source term and extracting the relevant time-delay representing the time it takes for an acoustic wave traveling from the microphone to the ground and back. Furthermore, we show that the method is also robust to the more complex noise source generated by a quadrotor in a static, tethered experiment. To the best of our knowledge, this is the first framework and demonstration of obstacle sensing onboard an aerial vehicle using only the self-generated noise.

A novel vehicle tracking and speed estimation with varying UAV altitude and video resolution

ABSTRACT In this paper, a novel vehicle tracking and speed estimation method based on aerial videos is developed. The main objective of this research is to investigate how depth features of a vehicle extracted from aerial videos by a wide residual network could be used to realize accurate tracking for estimating the speed of the vehicle. The salient characteristics of the proposed method are: (1) Traffic analysis and robust vehicle detection are possible by virtue of the use of deep neural networks. (2) Employing the state-of-the-art object detector, namely the You Only Look Once (YOLO) network, a tracking-by-detection method is then designed to detect and track vehicles. (3) The error rate of data association is reduced by associating the tracking process with a vehicle re-identification algorithm whereby the motion features are combined with depth features of the vehicle. (4) Considering the varying Unmanned Aerial Vehicle (UAV) altitude and video resolution, a novel exponential mapping model of the vehicle speed from the pixel space to the real world is presented. The accuracy of speed estimation is effectively improved by employing the least squares algorithm to fit the measurement data. Simulation results and comparative studies with the state-of-the-art methods demonstrate superior performance of the proposed approach for vehicle tracking and speed estimation.

Pole placement and LQR implementation on longitudinal altitute holding control of wing in surface effect vehicle

The longitudinal altitude holding control system (LAHCS) of wing in surface effect (WiSE) vehicle has been developed using Simulink/Matlab. The LAHCS is designed to maintain the altitude of the vehicle stands at 1 m above the surface, with a maximum allowable deviation of 0.5 m. The purpose is to gain an additional lift generated by the surface effect to increase the aerodynamic performance. This control system is investigated using two approaches, i.e., the pole placement and the linear quadratic regulator (LQR) methods. Originally, the system shows an unstable response on the phugoid mode, indicated by the positive value of its Eigen. After the pole placement method is applied, the system is stable and capable of maintaining the reference command altitude. This method produces 0.27 of the maximum altitude deviation when the disturbance, represented by the doublet input elevator ±5° is applied. Moreover, the time needed for the system to reach the steady-state response of altitude is around 2.2 seconds. In comparison, the LQR method is also applied to the system with the same scenario. Although the settling time response is quite similar to the previous result, its maximum altitude deviation is significantly reduced by around 80 %. In conclusion, both of the methods used to design the LAHCS are capable of maintaining the altitude of the WiSE vehicle always below its maximum deviation tolerance.

Identification of nonlinear time‐varying systems using wavelet neural networks

AbstractThe dynamic model of an aircraft changes significantly by altering the flight speed and the vehicle altitude. Thus, a conventional aircraft has a nonlinear time‐varying dynamic model in different regions of the flight envelope, and a dynamic model developed for a specific operating point is not valid in the entire flight envelope. This paper presents a novel identification approach that can deal with nonlinear and time‐varying characteristics of complex dynamic systems, especially an aerial vehicle in the entire flight envelope. In this regard, a set of local submodels are first developed at different operating points of the system, and subsequently, a multimodel structure is introduced to aggregate the outputs of the local models as a single model. Wavelet Neural Networks (WNNs), which combine both the universal approximation property of neural networks and the wavelet decomposition capability, are used as the local models of the proposed scheme. Also, three different approaches for determining the validity functions of the local models are introduced to allow for identifying the time‐varying dynamics of the system. The simulation results obtained for the Generic Transport Model aircraft suggest that the proposed WNN‐based multimodel structure can be used satisfactorily as the prediction model of model‐based flight control systems for long prediction horizons.

Tectonic, volcanic and hydrothermal features of a nascent rift graben in the southern Okinawa Trough

High-resolution geophysical mapping using an autonomous underwater vehicle (AUV) and surface vessel revealed tectonic, volcanic and hydrothermal features of a nascent rift graben in the southern Okinawa Trough. Ship-based bathymetry identified ENE–WSW trending lineaments at a water depth of 1900–2000 m that form a rift graben, the Ishigaki Rift, which is ~50 km long, ~7 km wide and has relief of ~100 m. Shipboard EM122 multibeam sonar detected acoustic bubble plumes and high-backscatter intensity on the seafloor along the rift. The AUV high-resolution bathymetry (2 m) and sidescan imagery revealed the presence of a ropey texture with high acoustic reflectivity, interpreted to be relatively young lava flows. Evidence of hydrothermal venting was observed at two previously unknown sites along the rift. Steep-sided spires up to 23 m in height and a mound discharging smoke-like acoustic plumes were identified. The AUV temperature sensor observed sharp temperature increases of up to ~0.13 °C around the plumes, even at the vehicle's altitude of ~100 m above the seafloor. The presence of relatively young lava flows and indicators of high-temperature hydrothermal venting and gas bubbles suggest the Ishigaki Rift is magmatically active. Compared with adjacent active back-arc rifts, the Ishigaki Rift has a shorter length, narrower width and lower relief, and occurs at a shallower water depth, suggesting that the rift is relatively young and immature. Considering that the Ishigaki Rift is located near the arc volcanic front and that other mature rifts are typically located farther from the front, it is suggested that a new axial rift system is evolving within the Okinawa Trough and that back-arc rifting processes may be gradually migrating arcward in the trough during the Quaternary.

Numerical investigations on acoustic environment of multi-nozzle launch vehicle at lift-off

The acoustic environment significantly influences the safety and reliability of the launch vehicle at lift-off. Aeroacoustic has always been the focus of attention in the field of aerospace. In the paper, the flow field and acoustic environment caused by multiple jets of the launch vehicle at lift-off are numerically simulated using the three-dimensional compressible Navier-Stokes equation, second-order Roe scheme, scale-adaptive simulation (SAS) and acoustic analogy method (FW-H). The jet noise of single-nozzle launch vehicle are numerically simulated for the verification of numerical methods solving the acoustic, and the relative error in between the numerical results and the experimental data is less than 1.6%. Then the influence of the position of the tower, the vehicle's altitude and the configuration of the deflector on the acoustic environment of the vehicle is studied. The results show that the overall sound pressure level (OASPL) reaching the vehicle with the one-sided jet deflector is larger than that of the vehicle with the two-sided jet deflector. Compared with the initial lift-off altitude, the vehicle's altitude at 12 times of the nozzle-exit's diameter can increase the acoustic load around the vehicle. However, the position of the tower has little effect on the OASPL reaching the vehicle with the one-sided jet deflector. The analysis method provides reference for noise prediction and acoustic environment control of the launch vehicle.

Detailed volcanic and tectonic morphology of Nakadomari Hill in the southern Okinawa Trough

Nakadomari Hill is an unexplored edifice in the southern Okinawa Trough back-arc basin where crustal extension by continental rifting occurs and few submarine eruptions associated with back-arc volcanism have been mapped in detail. High-resolution bathymetric mapping with an autonomous underwater vehicle (AUV) reveals that Nakadomari Hill is a submarine volcanic complex with recent lava flow eruptions. The high-resolution (2 m) bathymetry shows striking contrast between rugged terrain in the central area and the adjacent smooth terrain. The cone-shaped features in the rugged terrain are covered by ropey fabric with high acoustic reflectivity and are devoid of tectonic deformation, thus they are interpreted to be relatively younger lava domes. The cone-shaped features in the smooth terrain show low reflectivity and are dissected by ENE–WSW trending tectonic lineaments, suggesting they were formed during older volcanism. Nakadomari Hill developed through multi-stage eruptions before and after back-arc rifting and faulting. The ropey and curtain-folded morphology with high acoustic reflectivity are interpreted to be a field of lava flows and they are relatively young. The area considered to be lava flows is estimated to be over 13 km2, showing that eruptions in the southern Okinawa Trough have been extensive. An active volcanic system is supported by indicators of high-temperature hydrothermal venting. Hydrothermal plumes with concurrent sharp temperature increases of up to 0.17 °C were present even at the vehicle altitude of ~100 m above the bottom. The alignment of volcanic cone-shaped features at Nakadomari Hill is in the NNW–SSE direction which is clearly different from the orientation of local rifting (ENE–WSW). At a larger scale, the volcanic edifices west of Kume Island from the arc to back-arc are also aligned roughly in the NNW–SSE direction and they are sub-parallel to a major tectonic structure in the arc, the Kerama Gap. The agreement of the local volcanic and tectonic trends implies that magmatic focusing may have taken place along the tectonic structures of the Kerama gap and in turn caused the extensive back-arc volcanism in this area.

Development of a MEMS-based barometric pressure sensor for micro air vehicle (MAV) altitude measurement

A pressure sensor can be used for altimetry as pressure varies with altitude. In this work, a MEMS-based bulk-micromachined piezoresistive pressure sensor is developed for micro air vehicle (MAV) application. The sensor chip has meander shaped diffused piezoresistors, placed at optimum locations determined using FEM simulations for enhancing sensitivity. Post process wet bulk micromachining is carried out to realize the sensor diaphragm, while protecting the processed wafer side. Excellent sensitivity, non-linearity and hysteresis of 34.78 mV/bar, < 0.12% and < 0.2%, respectively is obtained from static characterization of optimum sensor chip. For the operating altitude range of the MAV, the variation of output voltage of pressure sensor module (obtained by integrating the sensor chip with circuitry) with altitude is characterized inside a test chamber.

Backstepping and Robust Control for a Quadrotor in Outdoors Environments: An Experimental Approach

This paper addresses the tracking control of quadrotors flying outdoors. Two control laws are combined and tested in real-time experiments. The aircraft attitude and the translational displacement are controlled using the backstepping approach, while the altitude is controlled using the sliding mode control strategy. In both cases, new modifications are introduced with respect to the existing classical algorithms. Concerning the backstepping algorithm, we introduce the dynamical model of the quadrotor in the controller design and this guarantees that the virtual input is bounded. On the other hand, the proposed sliding mode control assures that the vehicle's altitude converges in finite time to the desired reference, even when uncertainties are considered in the system. The proposed controller is tested in an outdoor environment and the experiments highlighted the controllers' reliability. Additionally, the performance of the closed-loop plant with the proposed controllers is compared with the performance given by a proportional-derivative controller.

Altitude consensus based 3D flocking control for fixed-wing unmanned aerial vehicle swarm trajectory tracking

This paper studies the 3D flocking control problem for unmanned aerial vehicle swarm when tracking a desired trajectory. In order to allow the unmanned aerial vehicle swarm to form the stable flocking geometry on a same horizontal plane, the altitude consensus algorithm is applied to the unmanned aerial vehicle altitude control channel, using the trajectory altitude as the external input signals. The flocking control algorithm is only performed in the horizontal channel to control the horizontal position of unmanned aerial vehicles. The distributed tracking algorithm, which controls the local averages of position and velocity of each unmanned aerial vehicle, is implemented to achieve the better tracking performance. The improved artificial potential field method is introduced to achieve the smooth trajectory when avoiding obstacles. The practical dynamic and constraints of unmanned aerial vehicles are also taken into account. Numerical simulations are performed to test the performance of the proposed control algorithm.

Trajectory linearization control based tracking guidance design for entry flight

A novel use of trajectory linearization control( TLC) method was introduced in the guidance law design for hypersonic vehicle entry flight. By exploiting the inherent characteristics of time scale separation of entry vehicle dynamics,altitude and velocity could be controlled separately via outer and inner loop design.In the outer loop,path angle was used as pseudo-control for controlling the altitude. In the inner loop,the flight path angle command and velocity were tracked using bank angle and angle of attack as controls. A linear time-varying controller was designed for the feedback loop to stabilize the error dynamics. Feedback gains were computed online and are the symbolical functions of reference trajectory,therefore no explicit gain scheduling or mode-switching were needed. Extensive dispersion simulations show that this guidance algorithm can achieve precise trajectory tracking and is trajectory-independent. The simulations also show that an integrated entry guidance approach which combines the use of TLC-based tracking guidance law design and on-board reference trajectory planning can significantly enhance the autonomy and adaptability of entry flight.