Elevation Tracking Research Articles

Global analysis of active defense technologies for unmanned aerial vehicle

This paper explores active defense for UAVs globally, with the main emphasis on detection and countermeasure technologies. Questionnaires were administered to 139 individuals in the USA, and the results were analyzed with the help of the Statistic Package for Social Sciences (SPSS), including reliability analysis, descriptive frequency, and regression analysis. The results concerning Hypothesis 1 concerning technological detection impact on the adequacy of UAV defense are the following. Analyzing the data, it was established that detection technology influences UAV defense significantly with F =12. 27 and a signification p, therefore, is less than 0,001. Total regression analysis showed that In relation to this aspect, the regression coefficient (b = 0. 292, p <. 001) shows that detection technology has a positive influence on UAV defense and accounts for 8. Two percent of the total aggregated variation across the defense effectiveness of the participating countries (R² = 0. 082) could solely be attributed to these potentates. Thus, the findings of Hypothesis 2 prove that countermeasure technology also plays another major role in the defense of UAVs. Analysis of variance for the model revealed that technology used in countermeasures tremendously impacts UAV defense with F = 113. 465, and the calculated p is less than 0. 000; hence, the findings are highly significant. Thus, the regression coefficient (b = 0.782, p < 0.000) indicates a significant contribution of countermeasure technology influencing the reduction rate, which amounts to 45 %. 14% of the variance in UAV defense effectiveness gives a coefficient of determination of 0.453. Based on these findings, developing detection and countermeasure technologies are crucial to improving UAV defense systems. The research findings suggest that azimuth and elevation tracking and invariant pattern recognition technologies used in this system can be enhanced to enhance the effectiveness of a UAV countermeasure system.

Adjusted linear quadratic regulator-proportional-derivative control of Quanser’s three degrees of freedom helicopter based on flower pollination algorithm under external disturbances

External disturbances, saturation of actuator motors, and limits of certain angular movements are commonly encountered in robotic systems, particularly those involving flight, and they present the most common and influential factors affecting the stability and performance of these systems. In this paper, a hybrid controller for a three-degree-of-freedom (3-DoF) helicopter is designed and applied to this flying robot system, taking into account the previously mentioned constraints. The proposed hybrid controller integrates proportional-derivative (PD) control with an adjusted linear quadratic regulator (ALQR) using the flower pollination algorithm (FPA) optimization method. Simulation results of travel (λ), elevation (ε), and pitch (ρ) responses, as well as experimental results of elevation and travel tracking responses under external disturbances using the bench-top Quanser’s (3-DoF) helicopter, demonstrate the robustness and good performance of the controlled system using the proposed method. The effectiveness of the proposed method is compared to several methods in the literature.

Rotating solar furnace

A rotary solar furnace is conceptually introduced. In contrast to a conventional solar furnace, where the concentrator is fixed, in a rotary solar furnace both the concentrator and the heliostat rotate in concentric circular path around the concentrator's focus such that at each instant of time they face each other. The angular velocity of this motion equals the angular velocity of the Sun's projection line onto the Earth. In this dynamic solar furnace, the Sun appears always right above the heliostat. Consequently, the heliostat needs only a single-axis elevation tracking to redirect the sunlight along the concentrator's optical axis. This implies that the amount of harvested energy is maximal while the focus remains fixed in space. The daily concentrated radiation energy is analytically computed for each day of the year given the geographical latitude. It is shown the daily energy increase percentage crucially depends on the day of year and geographical latitude. This increase percentage reaches it maximum value in the summer solstice, which is slightly above 140 percent, for instance, in Tehran, Iran.

FLAP Heliostat

Heliostats represent a major cost share of concentrating solar power (CSP) plants with central receiver. They are essential for system efficiency and strongly influence maintenance cost and service life. Since CSP facilities require direct solar radiation, suitable installation sites can eminently be found in desert regions. However, dusty conditions may greatly reduce the performance of the plant due to soiling of the heliostat’s reflective surface and / or irreversible degradation caused by abrasive sand particles. A novel heliostat called FLAP, developed specifically for desert environments, is presented in this paper. It was designed with an emphasis on maximum manufacturing and maintenance cost reduction, yet improved service life in mind. The essential innovation of the FLAP heliostat is the patented foldable reflector support structure consisting of two panel sections that are oriented face-to-face when being in lay-down stow position. Folding of the panels is accomplished by means of a mechanism comprising a simple yet effective 4-bar linkage. To avoid costs for additional drives, the device is actuated by the one single central linear actuator that is also used for elevation tracking. Furthermore, wind loads are minimized due to the low profile of the heliostat structure in stow position, resulting in material and hence overall cost savings.

A multi-sensor cooperative detection target tracking method based on radar-optical linkage control

Radar is a common means of tracking a target, and with active enemy interference, it often causes the target to lose its track, thus causing the radar to lose continuous tracking of the target. To improve the tracking effect, a multi-sensor cooperative detection target tracking method based on radar photoelectric linkage control was established. The study is based on radar photoelectric linkage, constant velocity (CV), constant acceleration (CA) and current statistical model (CSM) as the mathematical model of moving targets for this study. Improved interactive multi-model (IMM) and standard IMM were compared for targets in different motion states, as well as single sensor electronic support measures (ESM) and multi-sensor electronic support measures (ESM), infrared search and track (IRST). The research results show that in variable speed motion, the improved IMM algorithm and multiple sensors are used for target tracking. The azimuth and elevation tracking errors of the target are low, which can effectively solve the problem of model mismatch during the conversion of motion modes such as CV and CA. The azimuth and elevation image curves fluctuate smoothly, and have high stability. This method can achieve better tracking results.

Novel high precision low-cost dual axis sun tracker based on three light sensors

This study aims to test a new type of dual axes solar tracker based on just three Light Dependent Resistors (LDR) as optical sensors in order to achieve a high precision sun tracking that satisfies the requirements of solar concentration systems. This new system is integrated into a solar concentrator that uses a set of Fresnel mirrors and an evacuated tube collector as an absorber so that it can be used as a solar water heater. The 3D-printed support that holds LDRs have three compartments to maintain the three LDRs firmly in their place. One is placed on the left and the other on the right side of the support. These two LDRs are responsible for the azimuthal tracking while the third LDR is placed in the center and its responsibility is elevation tracking. This central LDR is covered under an alveolus hollow tube with a length of 45mm crossed all along its center with a 0.4mm slot that lets sun rays reach the central LDR at the bottom of the alveolus hollow tube. A setup was made to collect data based on a pyranometer and three thermocouples positioned at specific points on the evacuated tube collector to record the temperature variation.

Graphical Ray Tracing Formulation of New Center Oriented Spinning Elevation Tracking Technique for Heliostat

Graphical Ray Tracing Formulation of New Center Oriented Spinning Elevation Tracking Technique for Heliostat

COLREG-Compliant Collision Avoidance for Unmanned Surface Vehicle Using Deep Reinforcement Learning

Path Following and Collision Avoidance, be it for unmanned surface vessels or other autonomous vehicles, are two fundamental guidance problems in robotics. For many decades, they have been subject to academic study, leading to a vast number of proposed approaches. However, they have mostly been treated as separate problems, and have typically relied on non-linear first-principles models with parameters that can only be determined experimentally. The rise of deep reinforcement learning in recent years suggests an alternative approach: end-to-end learning of the optimal guidance policy from scratch by means of a trial-and-error based approach. In this article, we explore the potential of Proximal Policy Optimization, a deep reinforcement learning algorithm with demonstrated state-of-the-art performance on Continuous Control tasks, when applied to the dual-objective problem of controlling an autonomous surface vehicle in a COLREGs compliant manner such that it follows an a priori known desired path while avoiding collisions with other vessels along the way. Based on high-fidelity elevation and AIS tracking data from the Trondheim Fjord, an inlet of the Norwegian sea, we evaluate the trained agent's performance in challenging, dynamic real-world scenarios where the ultimate success of the agent rests upon its ability to navigate non-uniform marine terrain while handling challenging, but realistic vessel encounters.

A Heuristic Approach for Tracking Error and Energy Consumption Minimization in Solar Tracking Systems

This paper proposes a methodology for optimizing a class of robotic solar tracking systems with two degrees of freedom using a heuristic approach. The proposal allows a balance to be found between the energy consumption and tracking accuracy in the tracking system. The main purpose is the behavior modification of the system through the combination of two manipulation strategies, one associated with the energy savings and the other with the tracking error. The heuristic approach was implemented in a solar tracking system with the end effector connected to a solar measurement device. Four energy-saving strategies and three tracking strategies were developed, simulated, and implemented in the system. The simulation results show that the resulting strategy combination (tracking error and energy saving approach) led to 31.55% energy savings compared to the reference values, with a tracking error of 0.06°. Moreover, the experimental assessment of the same combination led to 26.98% energy is being saved, with an azimuthal tracking error of 0.062° and elevation tracking error of 0.071°. The preceding values support the aim of the presented proposal to significantly reduce energy consumption while concurrently achieving a competitive tracking error.

A Study on Performance Improvement of Target Motion Analysis using Target Elevation Tracking and Fusion in Conformal Array Sonar

A Study on Performance Improvement of Target Motion Analysis using Target Elevation Tracking and Fusion in Conformal Array Sonar

Effect of Tracking Error of Double-Axis Tracking Device on the Optical Performance of Solar Dish Concentrator

In this paper, a flux distribution model of the focal plane in dish concentrator system has been established based on ray tracking method. This model was adopted for researching the influence of the mirror slope error, solar direct normal irradiance, and tracking error of elevation-azimuth tracking device (EATD) on the focal spot characteristics (i.e., flux distribution, geometrical shape, centroid position, and intercept factor). The tracking error transmission law of the EATD transferred to dish concentrator was also studied. The results show that the azimuth tracking error of the concentrator decreases with the increase of the concentrator elevation angle and it decreases to 0 mrad when the elevation angle is 90°. The centroid position of focal spot along x-axis and y-axis has linear relationship with azimuth and elevation tracking error of EATD, respectively, which could be used to evaluate and calibrate the tracking error of the dish concentrator. Finally, the transmission law of the EATD azimuth tracking error in solar heliostats is analyzed, and a dish concentrator using a spin-elevation tracking device is proposed, which can reduce the effect of spin tracking error on the dish concentrator. This work could provide fundamental for manufacturing precision allocation of tracking devices and developing a new type of tracking device.

Modeled Tradeoffs between Developed Land Protection and Tidal Habitat Maintenance during Rising Sea Levels.

Tidal habitats host a diversity of species and provide hydrological services such as shoreline protection and nutrient attenuation. Accretion of sediment and biomass enables tidal marshes and swamps to grow vertically, providing a degree of resilience to rising sea levels. Even if accelerating sea level rise overcomes this vertical resilience, tidal habitats have the potential to migrate inland as they continue to occupy land that falls within the new tide range elevations. The existence of developed land inland of tidal habitats, however, may prevent this migration as efforts are often made to dyke and protect developments. To test the importance of inland migration to maintaining tidal habitat abundance under a range of potential rates of sea level rise, we developed a spatially explicit elevation tracking and habitat switching model, dubbed the Marsh Accretion and Inundation Model (MAIM), which incorporates elevation-dependent net land surface elevation gain functions. We applied the model to the metropolitan Washington, DC region, finding that the abundance of small National Park Service units and other public open space along the tidal Potomac River system provides a refuge to which tidal habitats may retreat to maintain total habitat area even under moderate sea level rise scenarios (0.7 m and 1.1 m rise by 2100). Under a severe sea level rise scenario associated with ice sheet collapse (1.7 m by 2100) habitat area is maintained only if no development is protected from rising water. If all existing development is protected, then 5%, 10%, and 40% of the total tidal habitat area is lost by 2100 for the three sea level rise scenarios tested.

Simulations of reflected sun beam traces over a target plane for an azimuth–elevation tracking heliostat with fixed geometric error sources

For a heliostat with geometric errors, the reflected central solar ray from the mirror surface center forms a curved error trace on the target plane during the day rather than staying fixed on one target point. A general azimuth–elevation tracking angle formula has been developed for a heliostat with a mirror-pivot offset and other typical geometric errors. This tracking angle formula is re-rewritten here as a series of easily solved expressions. This azimuth–elevation tracking angle formula is then used in a new complete geometric model of the sun-beam tracking errors for an azimuth–elevation tracking heliostat to simulate the sun beam tracking error trace on the target plane for a heliostat with fixed geometric errors. Here, the analysis is for a point sun and a point heliostat (or the heliostat considered as a small optical flat). The mirror surface center is defined as the orthogonal projection of the heliostat pivot on the mirror surface plane. The reflected sun-beam centre in the target plane is defined as the intersection of the mirror-surface-centre reflected central solar ray with the target plane. Due to a position tracking error in the target plane depending on the position and the orientation of the specific target plane, the position tracking error is further converted to the angular tracking error in the reflection direction to facilitate evaluation of the heliostat tracking performance. Simulations for the artificial #78 heliostat in the Beijing solar tower system on June 21st are shown to illustrate this heliostat tracking error model. This heliostat tracking error model can be used to reveal the effect of various geometrical errors in pedestal tilt etc. on the location of the beam at the target, and thus is useful in setting limits on the various geometrical errors. Essentially this paper allows one to estimate the offset of the reflected solar beam centre due to specific geometrical tracking errors, once the beam centre is computed by some other means. It also allows one to determine a limit on each error or set of errors which are allowable for a given purpose.

Properties of a general azimuth–elevation tracking angle formula for a heliostat with a mirror-pivot offset and other angular errors

The solar field of a central receiver system (CRS) is an array of dual-axis tracking heliostats on the ground beside or around a central tower, with each heliostat tracking the sun to continuously reflect the solar beam onto the fixed tower-top receiver. Azimuth–elevation tracking (also called altitude–azimuth tracking) is the most common and popular tracking methods used for heliostats. A general azimuth–elevation tracking angle formula was developed previously for a heliostat with a mirror-pivot offset and other typical geometric errors. The angular error parameters in this tracking angle formula are the tilt angle, ψt, and the tilt azimuth angle, ψa, for the azimuth axis from the vertical direction, the dual-axis non-orthogonal angle, τ1 (bias angle of the elevation axis from the orthogonal to the azimuth axis), and the non-parallel degree, μ, between the mirror surface plane and the elevation axis (canting angle of the mirror surface plane relative to the elevation axis). This tracking angle formula is re-rewritten here as a series of easily solved expressions. A more numerically stable expression for the mirror-center normal is then presented that is more useful than the original mirror–normal expression in the tracking angle formula. This paper discusses some important angular parametric properties of this tracking angle formula. This paper also gives an approach to evaluate the tracking accuracy around each helistat rotational axis from experimental tracking data using this general tracking angle formula. This approach can also be used to determine the heliostat zero angle positioning errors of the two rotational axes. These supplementary notes make the general azimuth–elevation tracking angle formula more useful and effective in solar field tracking designs.

Accurate altitude–azimuth tracking angle formulas for a heliostat with mirror–pivot offset and other fixed geometrical errors

High precision tracking formulas were developed for a receiver-oriented toroidal heliostat with the standard spinning-elevation tracking geometry in a previous paper. The spinning-elevation tracking geometry included some mirror–pivot offset, orthogonal intersecting rotational axes and the elevation axis being parallel to the mirror surface plane. This paper analyzes the tracking accuracy of these standard spinning elevation tracking formulas to show that they are accurate with negligible tracking error. Hence, the mirror-surface-center normal obtained from these formulas is accurate for any dual-axis tracking heliostat. Then, the accurate mirror-surface-center normal information is used to determine general altitude–azimuth tracking angles for a heliostat with a mirror–pivot offset and other geometrical errors. The main geometrical errors in a typical altitude–azimuth tracking geometry are the azimuth axis tilt from the vertical, the non-orthogonality between the two heliostat rotational axes, the non-parallel degree between the mirror surface plane and the altitude axis, and the encoder reference errors. An actual heliostat in a solar field is used as an example to demonstrate use of the general altitude–azimuth tracking formulas, with the tracking angles for this heliostat on typical days graphically illustrated. The altitude–azimuth tracking angle formulas are further verified by an indoor laser-beam tracking test on a specially designed heliostat model.

Elevation trends and shrink–swell response of wetland soils to flooding and drying

Given the potential for a projected acceleration in sea-level rise to impact wetland sustainability over the next century, a better understanding is needed of climate-related drivers that influence the processes controlling wetland elevation. Changes in local hydrology and groundwater conditions can cause short-term perturbations to marsh elevation trends through shrink–swell of marsh soils. To better understand the magnitude of these perturbations and their impacts on marsh elevation trends, we measured vertical accretion and elevation dynamics in microtidal marshes in Texas and Louisiana during and after the extreme drought conditions that existed there from 1998 to 2000. In a Louisiana marsh, elevation was controlled by subsurface hydrologic fluxes occurring below the root zone but above the 4 m depth (i.e., the base of the surface elevation table benchmark) that were related to regional drought and local meteorological conditions, with marsh elevation tracking water level variations closely. In Texas, a rapid decline in marsh elevation was related to severe drought conditions, which lowered local groundwater levels. Unfragmented marshes experienced smaller water level drawdowns and more rapid marsh elevation recovery than fragmented marshes. It appears that extended drawdowns lead to increased substrate consolidation making it less resilient to respond to future favorable conditions. Overall, changes in water storage lead to rapid and large short-term impacts on marsh elevation that are as much as five times greater than the long-term elevation trend, indicating the importance of long-term, high-resolution elevation data sets to understand the prolonged effects of water deficits on marsh elevation change.

Doppler-based detection and tracking of humans in indoor environments

In this paper, the principles of Doppler processing to detect and track human movers in indoor environments are presented. The topics discussed include the micro-Doppler characteristics of humans, the azimuth, elevation and range tracking of humans using Doppler, spatial and frequency diversity, the effect of walls, and the characteristics of dynamic clutters from non-humans. The studies are supported by simulation and measurement results.

Reconfigurable leaky-mode/multifunction patch antennastructure

A reconfigurable aperture where different types of antennas and arrays with multiband coverage and multiple functions share a common planar physical aperture is proposed. Using either conventional or MEMS switches, a microstrip-based leaky-mode antenna array can easily be reconfigured to patch antennas operating at multiple frequency bands, as well as monopulse radars for both azimuth and elevation tracking. The feasibility of the concept has been demonstrated by prototype design and measurement of a single-channel X-band leaky-wave/S- and C-band patch antenna structure.

Development of direct broadcasting satellite reception system for a small car

To realize the DBS (Direct Broadcasting Satellite) reception system for a small car, we have developed an antenna system concentrating on “Miniaturization” and “Low-cost”. In this paper, an outline and the features of the developed antenna system are described. It can be mounted on a small car, and is a small, low-cost antenna whose design is simplified by adopting the planar beam tilt antenna and abolishing elevation tracking.

A single-layer slotted leaky waveguide array antenna for mobile reception of direct broadcast from satellite

This paper proposes a single-layer slotted leaky waveguide array antenna for mobile DBS reception. A single-layer feed structure is proposed, where the feed waveguide is in the same layer as the radiating waveguides. This results in the simple fabrication of slotted waveguide arrays, suitable for mass production. Short radiating leaky waveguides are used to get a large beam-tilting angle of about 50/spl deg/ for the horizontal installation of the antenna and a beamwidth broad enough to dispense with mechanical steering in the elevation plane. A prototype antenna sized 30 cm by 21 cm has a maximum of 74% efficiency and more than 69% efficiency within the DBS band. It also has a broad l-dB beamwidth of 7.5/spl deg/ in the elevation plane, which enables clear DBS reception by a picture tube display over about one-third the area of Japan without elevation tracking.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>