SHADOW MODELLING ALGORITHM FOR PHOTOVOLTAIC SYSTEMS ANALYSIS AND SIMULATION

In this paper, an algorithm capable of modelling shadows from nearby obstructions onto photovoltaic arrays is proposed. The algorithm developed is based on the calculation of the solar position in the sky for any given instant in order to obtain the shadow projection for any object point. The convexity properties of objects and their shadows are used to allow a precise three-dimensional solution with reduced computational power without the need to consider a vast grid of points. The idea is extended to provide the shading patterns for a desired range of time and to calculate the eciency rate of the irradiation power incident on the array in comparison to the non-shadowed case. The algorithm has interesting applications, such as optimizing array positioning and orientation, evaluating the impact of new obstructions on pre-existing array installations, allowing precise and practical data for control strategies and MPPT techniques for partially shaded systems, calculating more realistically constrained payback scenarios and nding the optimal PV array interconnection. The results obtained are illustrated by a numerical example, in which the eects of a nearby building in the irradiation received by a photovoltaic array throughout the year is analyzed.

Digital Design Automation to Support In Situ Embedding of Functional Objects in Additive Manufacturing

Additive manufacturing (AM) offers designers access to the entire volume of an artifact during its build operation, including the embedding of foreign objects, like sensors, motors, and actuators, into the artifact to produce multifunctional products from the build tray. However, the application of embedding requires extensive designer expertise in AM. This research aims to develop a tool to automate design decisions for in situ embedding, eliminating the need for ad hoc design decisions made by experts. Two unique approaches are proposed in this work: shadow projection and voxel simulation. Both of these approaches follow a three-stage methodology to achieve design automation by (1) identifying the optimum orientation for the object, (2) designing cavity, and finally (3) designing the shape converter for a flush surface at the paused layer. The two approaches differ in Stages 2 and 3. Where the shadow projection approach employs a series of point cloud manipulation to geometry of the embedded object, the voxel simulation approach simulates the process of insertion of the embedding geometry into the part voxel by voxel. While both proposed approaches are successful in automating design for embedding complex geometries, they result in tradeoffs between final designs and the time for computation. Computational experiment with six test cases shows that designers must strategically choose from one of the approaches to efficiently automate the digital design for embedding.

To see the invisible: Image of the event horizon within the black hole shadow

How the supermassive black hole SgrA* in the Milky Way Center looks like for a distant observer? It depends on the black hole highlighting by the surrounding hot matter. The black hole shadow (the photon capture cross-section) would be viewed if there is a stationary luminous background. The black hole event horizon is invisible directly (per se). Nevertheless, a more compact (with respect to black hole shadow) projection of the black hole event horizon on the celestial sphere may be reconstructed by detecting the highly redshifted photons emitted by the nonstationary luminous matter plunging into the black hole and approaching the event horizon. It is appropriate to call this reconstructed projection of the event horizon on the celestial sphere for a distant observer as the “lensed event horizon image”, or simply the “event horizon image”. This event horizon image is placed on the celestial sphere within the position of black hole shadow. Amazingly, the event horizon image is a gravitationally lensed projection on the celestial sphere of the whole surface of the event horizon globe. As a result, the black holes may be viewed at once from both the front and back sides. The lensed event horizon image may be considered as a genuine silhouette of the black hole. For example, a dark northern hemisphere of the event horizon image is the simplest model for a black hole silhouette in the presence of a thin accretion disk.

Quadcopter localization and health monitoring method based on multiple virtual silhouette sensor integration

With the widespread deployment of quadcopters, the flight safety issue attracts increasingly public and academic attentions. This article presents a quadcopter flight regime extraction algorithm for quadcopter localization and health monitoring using imageries captured by general purpose monocular cameras. First, contour information is extracted from quadcopter shadows on the ground. In order to better illustrate the three-dimensional silhouette information contained in shadow contour on the ground, a virtual sensor named Shadow Projection Tunnel is designed. Then, multiple Shadow Projection Tunnels are generated according to the extracted silhouette information and corresponding light source positions. Finally, three-dimensional quadcopter positions and flight regimes are extracted based on the aggregation between multiple Shadow Projection Tunnels. The proposed method is validated to be accurate and efficient in monitoring quadcopter position and flight regimes based on the comparative analyses. In comparison with traditional quadcopter health monitoring methods, the proposed method has advantages on deployment convenience, system robustness, precision expandability, and scenario adaptability, making it an ideal solution for quadcopter monitoring in outdoor scenarios.

3D Image Formation in Transmitted Partially Coherent and Incoherent Light Applied to Dimensional Inspection

The peculiarities of 3D objects image formation with clear shadow projection based on the constructive theory of 3D objects formation under illumination by partially coherent and perfectly incoherent light are investigated. Threshold algorithms for determining the position of boundaries of geometric 3D objects are developed, algorithms taking into account object thickness, light source angular sizes, and projection system angular apertures. These algorithms are based on the application of a true (calculated) threshold or a standard one using the corrective component for thresholds. Cases of weak and strong 3D object volumetricity for partially coherent and incoherent illumination are studied. The analytical equations for these algorithms are given. It is shown that the use of algorithms can significantly improve the measurement accuracy of the extended objects.