Automatic imaging of solar power generation devices using an aircraft and automatic flight of the aircraft to carry out the imaging

Abstract

Aspects of the disclosure relate to automated imaging of a solar power generating device using an aircraft (20). In one aspect, there is a method (440) for automated imaging of a PV array (310) using an aircraft (20), where the PV array (310) corresponds to target points (350) for the aircraft (20). The method (440) includes positioning the aircraft (20) at one of the target points (350) corresponding to the PV array (310) and controlling the aircraft (20) for autopilot between the target points (350) to capture a visual dataset of the PV array (310). The autopilot includes aligning a field of view (225) of a camera (222) of the aircraft (20) to a PV array subsection of the PV array (310), determining a scanning direction (360) for moving the aircraft (20) between the target points (350), and capturing a visual dataset of the PV array (310) using the camera (222) starting from the PV array subsection as the aircraft (20) moves along the scanning direction (360) between the target points (350).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims the benefit of Singapore Patent Application No. 10202103967Y, filed April 19, 2021, which is incorporated by reference herein in its entirety.

[0002] The present disclosure relates generally to automated imaging of photovoltaic (PV) devices using aircraft and automated flight of the aircraft to perform same. More particularly, the present disclosure describes various embodiments of aircraft and methods for automated imaging of PV devices and automated flight of the aircraft to perform imaging of PV devices. [Background technology]

[0003] Solar panels find widespread use worldwide. However, due to high initial capital investment costs, solar panels installed in the field must work properly and efficiently for a given period of time to ensure a return on investment. Therefore, it is important to maintain the quality of solar panels installed in the field. Due to the mass deployment of solar panels in solar farms (or, in general, photovoltaic (PV) installations), and due to remote deployment of solar panels, such as on residential rooftops, it is often difficult to monitor the performance of individual solar panels. To detect defects in solar panels, various imaging techniques are available, such as visible, thermal (infrared), ultraviolet (UV) fluorescence, photoluminescence (PL), and electroluminescence (EL) imaging. For example, EL inspection is used during PV manufacturing for quality control.

[0004] For EL measurements, a PV module is connected to a power supply and placed under forward bias. The emitted near-infrared light is captured by a camera sensitive in the near-infrared wavelength range. Some of the common methods for EL measurements use mobile trailer or stationary tripod-mounted cameras. However, these methods are time-consuming and not feasible for large-scale PV installations. PV installations often have a lifespan of more than 25 years, and EL measurements may need to be performed multiple times during the lifespan, especially during critical milestones such as post-construction commissioning, inspections before liability or warranty periods end, and technical due diligence for asset transactions and insurance claims. EL measurements are a valuable tool for grading the performance and degradation of PV modules, but existing methods are time-consuming and extremely labor-intensive. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2021137764 Summary of the Invention [Problem to be solved by the invention]

[0006] Thus, a need exists for improved alternatives to address or mitigate at least one of the above-mentioned problems and / or shortcomings. [Means for solving the problem]

[0007] According to a first aspect of the disclosure, there is an aircraft and a method for automated imaging of a PV array using the aircraft, the PV array corresponding to a target point for the aircraft. The aircraft includes a controller for implementing the method, which includes positioning the aircraft at one of the target points corresponding to the PV array, and controlling the aircraft for autopilot between the target points to capture a visual dataset of the PV array. The autopilot includes aligning a field of view of a camera of the aircraft to a PV array subsection of the PV array, determining a scanning direction for moving the aircraft between the target points, and using the camera to capture the visual dataset of the PV array starting from the PV array subsection as the aircraft moves along the scanning direction between the target points.

[0008] According to a second aspect of the disclosure, there is an aircraft and a method for automated flight of the aircraft to perform imaging of a set of PV arrays. The aircraft includes a controller for performing the method, the method including determining flight paths between target points for capturing visual datasets of the PV arrays, each PV array corresponding to one or more target points, controlling the aircraft for automated flight along the flight paths to each of the target points, and controlling the aircraft for automated piloting at each of the one or more target points to capture a visual dataset of each PV array using a camera of the aircraft.

[0009] According to a third aspect of the disclosure, there is an aircraft and a method for automatic flight of the aircraft and automatic imaging of a set of PV arrays using the aircraft. The aircraft includes a controller for implementing the method, which includes determining a flight path between target points for capturing a visual dataset of the PV arrays, each PV array corresponding to a pair of start and end target points, controlling the aircraft for automatic flight along the flight path to each start target point of the PV arrays, and controlling the aircraft for automatic piloting between each start and end target point of each PV array to capture a visual dataset of the PV array using a camera of the aircraft. The automatic piloting includes aligning a field of view of the camera to a PV array subsection of the PV arrays, determining a scanning direction for moving the aircraft between the start and end target points, and capturing a visual dataset of the PV array using the camera starting from the PV array subsection as the aircraft moves along the scanning direction between the start and end target points.

[0010] Thus, an aircraft and method for autonomous flight and autonomous imaging of PV arrays in accordance with the present disclosure is disclosed herein. Various features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description of embodiments thereof, by way of non-limiting examples only, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0011] [Figure 1] 1 is an exemplary setup for a UAV to capture a visual dataset of a PV array. [Figure 2A] FIG. 1 is a block diagram illustrating a system architecture of a system for controlling a UAV to capture a visual dataset. [Figure 2B]The optical subsystem of a UAV, including the camera. [Figure 3A] 1 is a floor plan diagram of a PV installation including a PV array. [Figure 3B] 1 is a floor plan diagram of a PV installation showing flight paths to the PV array. [Figure 4] 1 is a flowchart of an exemplary process for automated flight of a UAV and for automated capture of a visual dataset. [Diagram 5] 1 is a perspective diagram of a model of a PV installation for obtaining an obstacle outline. [Figure 6] 1 is a plan view diagram of a PV array showing target points and target views. [Figure 7A] FIG. 1 is a plan view diagram of a PV array in front of a UAV, the UAV moving along a lateral scanning direction. [Figure 7B] FIG. 1 is a plan view diagram of a PV array next to a UAV, with the UAV moving along a forward scanning direction. [Figure 8] 1 is a side view diagram of a PV array and a UAV for deriving parameters for the UAV to scan the PV array. [Figure 9] 1 is a side view diagram of multiple PV arrays tilted in different directions. [Figure 10] 1 is a plan view diagram of a flight path around or over an obstacle to a PV array. [Figure 11] A triangular flight matrix for reordering the flight path between the home base and the target point. [Figure 12A] 1 is a plan view diagram of a flight path, with a camera following the flight path. [Figure 12B] 1 is a plan view diagram of a flight path with the camera pointing to a target view corresponding to the next target point. [Figure 13]1 is a plan view diagram of a UAV temporarily losing sight of a target view as the UAV approaches the target point. [Figure 14] 1 is a plan view diagram for determining a circular path around a target point toward the target point. [Figure 15A] 1 is a plan view diagram of a circuitous path that forms a shorter helical path. [Figure 15B] This is a plan view diagram of a shortened circular route. [Figure 16] FIG. 13 illustrates the FOV of the camera pointing to an incorrect target view as the UAV approaches the PV array. [Figure 17] FIG. 1 illustrates an interactive map for controlling a UAV. [Figure 18] FIG. 13 illustrates the FOV of a camera showing the polygonal outline of a PV array subsection. [Figure 19] 1A-1C are side and top view diagrams of a PV array and a UAV for deriving misalignment parameters for aligning the FOV of the cameras. [Figure 20] 1 is a side view diagram of a PV array and a UAV with different current pitch angles of the camera relative to the tilt angle of the PV array. [Figure 21] FIG. 13 illustrates the FOV of a camera with different positions of the PV array subsection inside the FOV. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] For purposes of brevity and clarity, the description of the embodiments of the present disclosure is directed to an aircraft and method for automatic flight and automatic imaging of a PV array according to the drawings. Although aspects of the present disclosure will be described in conjunction with the embodiments provided herein, it will be understood that they are not intended to limit the present disclosure to these embodiments. To the contrary, the present disclosure is intended to cover alternatives, modifications, and equivalents to the embodiments described herein, which are included within the scope of the present disclosure as defined by the appended claims. Moreover, in the following detailed description, specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be recognized by individuals of ordinary skill in the art (i.e., those skilled in the art) that the present disclosure can be practiced without the specific details and / or with multiple details resulting from the combination of aspects of a particular embodiment. In many instances, well-known systems, methods, procedures, and components have not been described in detail so as not to unnecessarily obscure aspects of the embodiments of the present disclosure.

[0013] In embodiments of the present disclosure, the depiction of a given element in a particular figure, or consideration or use of a particular element number, or reference thereto in corresponding explanatory material, can encompass the same, equivalent, or similar element or element number identified in another figure or explanatory material associated therewith.

[0014] References to "one embodiment / example," "another embodiment / example," "some embodiments / examples," "some other embodiments / examples," etc., indicate that the embodiment / example so described may include a particular feature, structure, attribute, property, element, or limitation, but not all embodiments / examples necessarily include that particular feature, structure, attribute, property, element, or limitation. Moreover, repeated use of the phrase "in one embodiment / example" or "in another embodiment / example" does not necessarily refer to the same embodiment / example.

[0015] Terms such as "comprising," "including," and "having" do not exclude the presence of other features / elements / steps than those listed in an embodiment. The recitation of certain features / elements / steps in mutually different embodiments does not indicate that a combination of these features / elements / steps cannot be used in an embodiment.

[0016] As used herein, the terms "a" and "an" are defined as one or more than one. The use of " / " in the figures or related text is understood to mean "and / or" unless otherwise indicated. The term "set" is defined as a non-empty, finite organization of elements that mathematically exhibits a cardinality of "at least one" in accordance with known mathematical definitions (e.g., a "set" as defined herein can correspond to a unit, a singlet, or a single element set, or a multiple element set). Recitation of a numerical value or range of values ​​for a particular measurement herein is understood to include or be a recitation of an approximate numerical value or range of values.

[0017] 1 illustrates an exemplary inspection setup 100 for imaging and capturing a visual dataset of a PV installation or system 10 mounted on the roof of a building. The visual dataset can be processed to obtain a processed image of the PV installation 10. An air vehicle (e.g., an unmanned aerial vehicle (UAV) 20) is deployed to capture a visual dataset of the PV installation 10 for inspection. The UAV 20 includes a main body 210, a propulsion device 230 attached to the main body 210 for actuating movement, including flight, of the UAV 20, and an optical subsystem 220 mounted to the main body 210 for capturing the visual dataset.

[0018] In the inspection setup 100, the imaging of the PV installation 10 includes electroluminescence (EL) measurements and the visual data set includes an EL visual data set. The PV installation 10 includes one or more PV arrays 11 and one or more PV strings 12 across the PV arrays 11. Each PV array 11 includes one or more PV devices or modules 14. One or more of the PV modules 14 are arranged in one or more of the PV strings 12. Each PV string 12 can extend across the one or more PV arrays 11 and each PV array 11 can form part of one or more PV strings 12. In the embodiment as shown in FIG. 1, the PV installation 10 includes a plurality of PV arrays 11 and four PV strings 12. An exemplary PV array 11 is shown with each PV string 12 extending across the PV array 11. The PV array 11 includes two rows of several PV modules 14. The PV array 11 and the PV strings 12 are arranged along a longitudinal axis 10a. The PV strings 12 are connected to a combiner box 16, which combines the electrical output of the PV strings 12. The combiner box 16 is connected to an inverter, which is then connected to the power grid. A larger PV installation 10 can include multiple combiner boxes 16, which are then connected to the inverter. Alternatively, the PV installation 10 can omit the combiner box 16, and the PV strings 12 are instead connected directly to the inverter. The inverter converts the combined electrical output from DC to AC before feeding it into the power grid. In this way, electricity generated by the PV modules 14 is fed into the power grid. During EL testing, the PV strings 12 are disconnected from the power grid.

[0019] The setup 100 further includes a switcher box 32, which includes one or more channels 34. In the embodiment as shown in FIG. 1, the switcher box 32 includes three channels 34, and each PV string 12 of the PV installation 10 is connected to each channel 34 of the switcher box 32. The setup 100 further includes a power supply 36, which is connected to the switcher box 32. The setup 100 can optionally omit the switcher box 32 and the PV strings 12 can be directly connected to the power supply 36. The power supply 36 is configured to supply electricity (e.g., up to 1500 volts, etc.) and a minimum current (e.g., equal to 10% of the short circuit current of the PV module 14, etc.) to each PV string 12. Preferably, each PV string 12 is supplied with 100% of the short circuit current of the PV module 14. However, this is not necessary. For example, each PV string 12 may be supplied with a current equal to 60% of the short circuit current of the PV module 14. Measurements of the PV module 14 at multiple currents may be used to estimate the electrical characteristics of the PV module 14 and to identify current dependent defects.

[0020] The channels 34 can be selectively activated (e.g., by a field worker or by remote control) to selectively supply current to the PV string 12 from a power supply 36 that places the PV string 12 under a forward bias condition. When placed in a forward bias condition, one or more PV modules 14 in the PV string 12 emit light (otherwise known as electroluminescence (EL)) and thus produce an EL signal detectable by the optical subsystem 220.

[0021] Additionally, it should be noted that multiple PV strings 12 can be connected to one channel 34. For example, all three PV strings 12 of a PV installation 10 can be connected to a single channel 34. In this scenario, all three PV strings 12 are simultaneously placed under forward bias conditions and an EL visual data set is captured for the entire PV installation 10. Notably, the amount of current provided by the power supply 36 is lower in this scenario compared to when each channel 34 is connected to a respective PV string 12, but this does not affect the PV strings 12 that are placed under forward bias conditions.

[0022] 2A illustrates a system architecture 200 of a system 200 for controlling a UAV 20. The system 200 includes a UAV 20 and a remote device 260 that communicates with the UAV 20. In addition to the optical subsystem 220 and the propulsion device 230, the UAV 20 further includes an on-board processing subsystem 240 and a power supply 242 (e.g., a set of batteries). The power supply 242 is connected to and powers the optical subsystem 220, the propulsion device 230, and the on-board processing subsystem 240. A controller 250 is communicatively connected to the optical subsystem 220 and the propulsion device 230 and is configured to control the optical subsystem 220 and the propulsion device 230 to perform various functions.

[0023] 2B, the optical subsystem 220 includes a camera 222 having an optical axis 222a. For example, the camera 222 is operable to capture monochromatic images and / or videos. The camera 222 is sensitive in the near infrared and / or short infrared (NIR, SWIR) EL wavelength bands and is suitable for capturing EL visual data sets in such wavelength bands. The camera 222 includes a focusing lens 223, which is also suitable for use in the NIR / SWIR EL wavelength bands. The lens 223 may include a motorized focus lens, a voltage controlled polymer lens, or a liquid lens. The lens 223 allows the controller 250 to adjust the focus of the lens 223 depending on the distance of the lens 223 to the PV array 11. The focus of the lens 223 may be adjustable, either mechanically or electrically driven. The camera 222 may further include a lens filter to filter out any unwanted spectrum of light.

[0024] The optical subsystem 220 further includes an optical distance measuring device, such as a light detection and ranging (Lidar) device 224. The Lidar device 224 has an optical axis 224a, which is aligned with the optical axis 222a of the camera 222. The Lidar device 224 is operable to measure the distance of the optical subsystem 220 from the PV array 11.

[0025] The optical subsystem 220 further includes a focused light source (e.g., laser 226 or LED, etc.). The laser 226 has an optical axis 226a, which is also aligned with the optical axis 222a of the camera 222. The laser 226 is arranged to emit light in the visible spectrum and has a beam divergence not larger than the field of view (FOV) of the camera 222, which minimizes optical interference from the laser 226. Moreover, the laser 226 allows for low power operation, emits light in a narrow wavelength band, and produces a focused shape that is easily identified. The focused shape may be symmetrical or asymmetrical. An asymmetrical shape advantageously allows for easier identification of where the camera 222 is pointing and also allows for determining the rotation of the camera's FOV.

[0026] The optical subsystem 220 further includes a single-axis gimbal 228, which mounts the optical subsystem 220 to the main body 210 of the UAV 20. The controller 250 controls the gimbal 228 to raise / lower the optical axis 222a of the camera 222 in one degree of freedom (i.e., pitch angle). For example, but not limited to, the gimbal pitch can have an angular range of ±35°. Alternatively, the optical subsystem 220 can be mounted to the main body 210 via a two-axis or three-axis gimbal 228, allowing additional degrees of freedom (i.e., yaw and roll angles) for adjusting the optical axis 222a of the camera 222 and providing enhanced stability of the FOV.

[0027] 2A, the propulsion device 230 of the UAV 20 includes four sets of propellers 232 driven by respective motors 234, enabling the UAV 20 to fly and perform aerial maneuvers such as rotating about the yaw axis 210a of the aircraft. As shown in FIG. 1, the yaw axis 210a is a vertical axis that runs through the middle portion of the main body 210 when the UAV 20 is upright, and the roll axis 210b runs through the back and front 20a of the UAV 20. The pitch axis is perpendicular to the yaw axis 210a and the roll axis 210b.

[0028] The on-board processing subsystem 240 includes a controller 250 and a memory unit 252. The controller 250 is configured to perform a particular function (as described further below) according to a set of instructions stored in the memory unit 252. The controller 250 receives information from the optical subsystem 220, including the distance from the PV array 11 to the Lidar device 224 and the visual feed of the camera 222. Using the information received from the optical subsystem 220, the controller 250 is configured to operate the optical subsystem 220 and the propulsion device 230 to perform a function. Once the EL visual dataset is captured, the UAV 20 can transmit the EL visual dataset to the remote device 260 or can return to the home base 330 and transfer the EL visual dataset for further processing to obtain a processed EL image. The remote device 260 includes a processor 262 and a memory unit 264, which stores instructions for executing a software application or mobile app to remotely control the UAV 20. For example, the remote device 260 may be a computer, a laptop computer, a mobile phone, or a tablet device.

[0029] There are various ways to control the flight motion of the UAV 20, such as by controlling the motor speed of the propellers 232, the UAV height or altitude, the UAV speed, and the UAV position. For example, for UAV speed control, the UAV 20 receives instructions including a velocity vector to fly at a defined speed and direction. For example, for UAV position control, the UAV 20 receives instructions including GPS coordinates and flies to those coordinates. Similarly, the gimbal 228 can be controlled to adjust the pitch, yaw, and roll angles of the camera 222 by speed control (e.g., controlling the gimbal pitch speed to adjust the pitch angle) or by position control (e.g., directly controlling the pitch angle position).

[0030] In some embodiments, the controller 250 is configured to directly control the flight control of the UAV 20 and the steering of the camera 222, and is also configured for image processing of the visual feed captured by the camera 222 (e.g., to align the camera 222 as described further below). In some other embodiments, the remote device 260 performs the flight control and image processing and sends instructions to the controller 250 for the UAV 20 to execute those instructions. The remote device 260 executes software thereon and communicates directly with the UAV 20 to control the UAV 20. In some other embodiments, the remote device 260 communicates with a handheld remote controller (e.g., a joystick device, etc.), which then communicates with the UAV 20 for flight control. The UAV 20, the remote device 260, and the remote controller can communicate with each other via suitable wired or wireless communication protocols. Non-limiting examples of wireless communication protocols include Bluetooth, Wi-Fi, telecommunications networks (e.g., 4G, 5G, and LTE, etc.), and peer-to-peer or server-based networks. The remote device 260 can be used to communicate with the channels 34 and selectively activate them to supply current to the PV strings 12 and place them under a forward bias condition.

[0031] In many embodiments, the UAV 20 is deployed to perform EL inspection of the PV installation 300, as shown in FIG. 3A, preferably at night or under low natural light conditions so that electroluminescence can be more easily captured. The PV installation 300 has multiple PV arrays 310 to be measured, each similar to the PV array 11 shown in FIG. 1. The PV installation 300 includes multiple PV strings 312 (S1, S2, S3) across the PV array 310 and are connected to two connection points 316 (P1, P2). The connection points 316 can be inverter or combiner boxes or other structures that connect the PV strings 312. Each PV array 310 includes multiple PV devices or modules 314 that are connected in series along each PV string 312. The PV strings 312 can be matched in a single PV array 310 or across multiple PV arrays 310.

[0032] The channels 34 can be selectively activated (e.g., by a field worker or by a remote device 260) to selectively supply current to the PV strings 312, which places the PV strings 312 under a forward bias condition. One EL visual data set (I1 to I6) can be generated for all PV arrays 310 and the current supplied to each PV string 312. The PV installation 310 further includes obstacles 320 (e.g., buildings and trees, etc.), which must be avoided by the UAV 20 during flight. Each obstacle 320 can be defined by a boundary 322 and a safety margin 324 outside the boundary 322. The home base 330 marks the location where the UAV 20 normally takes off and lands.

[0033] As further shown in FIG. 3B , the UAV 20 flies along a flight path 340 above the PV installation 300 to capture an EL visual dataset of the PV array 310. The flight path 340 (shown in dashed lines) includes a number of waypoints (n1 through n14) starting from and ending at the home base 330. The flight path 340 further includes one or more target points 350, each corresponding to a PV array 310, for capturing the EL visual dataset of the PV array 310. More specifically, when the UAV 20 is positioned at the target point 350, the camera 222 points toward the corresponding PV array 310, and a PV array subsection of the PV array 310 is within the camera's field of view (FOV) 225. The UAV 20 travels along a scanning path 360 (shown in dotted lines) to capture an EL visual dataset of one or more PV array subsections of the PV array 310, thereby completing the EL visual dataset of the PV array 310. The UAV 20 then flies along the flight path 340 to the next target point 350 and captures the EL visual data set of the next PV array 310.

[0034] UAV 20 is preferably configured with a flight plan detailing a flight path 340 and target points 350 for automated flight along flight path 340 and for automated capture of the EL visual dataset of the PV array 310. More preferably, a pilot of UAV 20 is able to remotely control channels 34 and supply current to the PV strings 312 without being on-site. However, it will be appreciated that UAV 20 can still perform automated flight and automated capture of the EL visual dataset in cooperation with an operator (or pilot) manually controlling channels 34.

[0035] FIG. 4 is a block diagram for an example process 400 for automated flight of UAV 20 over PV installation 300 and for automated capture of an EL visual dataset of PV array 310.

[0036] DATA function The process 400 includes a method 410 that represents a DATA function. The DATA function determines information needed for the UAV 20 to image and capture a visual dataset of the PV array 310. In many embodiments, the DATA function determines information for EL measurements and for capturing an EL visual dataset of the PV array 310. Information determined in the DATA function can be shared among various EL measurement contractors, and missing / inaccurate information can be obtained from previous EL visual datasets, processed EL images, and / or on-site physical measurements at the PV installation 300. Information can be categorized into UAV information, image information, and obstacle information.

[0037] The UAV information includes location details for locating the home base 330 of the UAV 20. The location details may include geographic coordinates of latitude and longitude. The UAV information also includes a safe height relative to the home base 330 at which it is safe for the UAV 20 to fly. The UAV information also includes a minimum distance between the UAV 20 and any obstacles 320 nearby the flight path 340 to prevent collisions.

[0038] The image information includes details of the EL visual data sets (e.g., I1 to I6) to be captured along with the corresponding PV strings 312 (S1 to S3), connection points 316 (P1, P2), and currents to be supplied to the PV strings 312. For example, and as shown in FIG. 1, the EL visual data set I1 corresponds to the PV string S1 and connection point P1, and the EL visual data set I4 corresponds to the PV string S2 and connection point P2. The image information further includes the tilt angle, azimuth angle, and height of the PV array 310 to be measured. Depending on the geographic location of the PV installation 300, the PV array may not be aligned in a true horizontal direction to maximize the exposure of the PV modules 314 to solar radiation. The tilt angle refers to the vertical tilt angle of the PV array 310 relative to the true horizontal plane. The azimuth angle refers to the horizontal rotation angle of the PV array 310 relative to a reference direction (e.g., due north) above the true horizontal plane. Height refers to the vertical height difference between the PV array 310 and the home base 330.

[0039] The obstacle information includes location details (e.g., geographic coordinates of latitude and longitude) of the boundaries 322 of the obstacles 320 in the PV installation 300. In a 3D perspective, the boundaries 322 of each obstacle 320 can be described using a prism model with a polygonal base. The obstacles 320 are objects in the vicinity of the flight path 340 that must be avoided by the UAV 20 during the measurement of the PV array 310. The obstacle information further includes a safety margin 324 for each obstacle 320, which may depend on the size of the obstacle 320. For example, a larger obstacle 320 will typically have a wider safety margin 324 to reduce the risk of collision with the UAV 20. The obstacle information further includes a height of each obstacle 320 relative to the home base 330. The obstacle height can be obtained from technical drawings and / or measured using a measurement device such as a Lidar device. For example, the Lidar device 224 of the UAV 20 may be used for such purposes.

[0040] There are various ways to obtain the boundary 322 of the obstacle 320. For example, as shown in FIG. 5, the PV installation 300 is modeled as a 3D digital surface model (DSM) 370 in a perspective view. The DSM is intersected by a horizontal intersection plane 372 at an intersection height 374, which is equal to the UAV safe height minus the UAV minimum distance listed in the UAV information above. The result of this intersection is a set of polygons above the intersection plane 372 that can be used to describe the boundary 322. Alternatively, the boundary 322 can be described by manual or machine-guided tracing of image edges in a 2D orthomosaic map, which correspond to the boundary 322. Still alternatively, the location coordinates of the corners of the obstacle 320 can be measured using a GPS-enabled mobile device.

[0041] PLAN Function The process 400 includes a method 420 representing a PLAN function. The PLAN function generates an imaging measurement plan for the UAV 20 to capture a visual dataset of the PV array 310. In many embodiments, the PLAN function generates an EL measurement plan for EL measurements and for capturing the EL visual dataset of the PV array 310. The EL measurement plan includes location details of the target point 350 and flight maneuvers to be performed by the UAV 20 to fly between the home base 330 and the target point 350 to capture the EL visual dataset of the corresponding PV array 310. The process 400 further includes methods 430 and 440 describing flight maneuvers. In particular, the method 430 represents a TOUR function for automated flight of the UAV 20 for EL measurements of the PV array 310, and the method 440 represents a SCAN function for automated EL measurements of each PV array 310. The TOUR and SCAN functions are described in more detail below.

[0042] In the EL measurement plan, each PV array 310 corresponds to one or more target points 350 for positioning the UAV 20 to capture the EL visual dataset of the PV array 310. As shown in FIG. 6, in some embodiments, the PV array 310 corresponds to a pair of target points 350 (shown as A' and B'). The PV array 310 further includes side points 352 (shown as A and B), which correspond to the target points A' and B', respectively. When the UAV 20 is positioned at the target points A' and B', the camera 222 is pointed to the side points A and B, respectively, and the optical axis 222a of the camera is aligned with the surface normal of the PV array 310. In many cases, the PV array 310 is rectangular and the UAV 20 will fly along the longer side to capture the EL visual dataset. Target points A' and B' define the initial and final positions of UAV 20, and side points A and B define the target view of camera 222 as UAV 20 moves between target points A' and B' during EL measurements. Side points 352, which are along the longer sides of PV array 310, can be acquired from intermediate positions on the shorter sides. By capturing an EL visual data set of PV array 310 while facing side points or target views 352, camera 222 is more likely to capture the edge of the PV array subsection within camera FOV 225. This facilitates the determination of a scanning path or direction 360 for moving UAV 20 in the opposite direction (i.e., from A' to B' or vice versa), as will be further described below in connection with the SCAN function.

[0043] The EL measurement plan further includes the tilt angle, azimuth angle, and height of the PV array 310. The tilt angle (α tilt ) and azimuth angle (α bearing ) is the pitch angle (α pitch ) and yaw angle (αyaw When the camera 222 faces forward (i.e., facing the front 20a of the UAV 20), the yaw angle (α yaw ) can be set equal to the yaw angle of the UAV 20 about the yaw axis 210a. pitch ) is the angle between the camera's optical axis 222a and the true vertical direction. pitch ) is positive when the camera 222 faces the front 20a of the UAV 20, and is negative when the camera 222 faces the back of the UAV 20. roll ) is assumed to be zero when the UAV 20 is aligned in a true horizontal plane.

[0044] There are two possible scanning directions 360 for moving the UAV 20 along the array axis 10a to capture an EL visual data set of the PV array 310. Figure 7A shows the PV array 310 at the front of the UAV 20, which moves along a sideways scanning direction 360a. Figure 7B shows a vertical alternative, where the PV array 310 is to the side of the UAV 20, which moves along a forward scanning direction 360b. Thus, the scanning direction 360 (sideways or forwards) depends on the placement of the UAV 20, the camera 222, and the PV array 310.

[0045] 7A, the UAV 20 and the camera 222 are both facing forward, i.e., the camera 222 faces the front 20a of the UAV 20. The gimbal 228 adjusts the tilt angle (α tilt ) to match the pitch angle (α pitch ) can be used to adjust the camera yaw angle (α yaw ) is the azimuth angle (α bearing) for optimal capture of the EL visual data set, with reference to FIG. 8, the optical axis 222a of the camera should be perpendicular to the surface of the PV array 310. If the PV array 310 is not tilted (i.e., α tilt =0), the UAV 20 flies directly above the PV array 310 while the camera 222 is in a nadir position and the pitch angle is zero (α pitch When the PV array 310 is tilted, the distance between the target point 350 and the target view 352 (d xy ) can be defined as follows, where d L is the distance between the UAV 20 and the PV array 310 along the surface normal. Furthermore, when the PV array 310 is rotated relative to the azimuth angle (α bearing ), the corresponding target point 350 of the PV array 310 is shifted by an azimuth angle (α bearing ) in the opposite direction to the shift angle (α shift ) will be shifted. d xy = d L sin(α tilt ) α shift = α bearing + 180°

[0046] With respect to the forward scanning direction 360b as shown in FIG. 7B, the UAV 20 and camera 222 are oriented vertically, i.e., the camera 222 is oriented sideways perpendicular to the front 20a of the UAV 20. If the gimbal 228 is multi-axis, the gimbal 228 adjusts the tilt angle (α tilt ) to match the roll angle (α roll Alternatively, the UAV 20 can be used to adjust the roll angle (α roll When the camera 222 is perpendicular to the UAV 20, the camera's yaw angle (α yaw ) is perpendicular to the azimuth angle (αbearing ) plus the azimuth angle (α bearing ), the corresponding target point 350 of the PV array 310 is shifted by an azimuth angle (α bearing ) and the shift angle (α shift ) will be shifted. α yaw = α bearing + 90° α shift = α bearing + 270°

[0047] In the same manner as the obstacle 320, the PV array 310 is an object with which the UAV 20 must avoid collision. The perimeter of the PV array 310 can be mapped in a similar manner to the obstacle 320. The height (d z ) is the current flight height (d baro ), the distance between the UAV 20 and the PV array 310 along the surface normal (d L ), and the pitch angle (α pitch ) can be estimated during the flight of the UAV 20. d z = d baro - [d L cos(α pitch )]

[0048] The camera 222 typically faces forward in the same direction as the front 20a of the UAV 20. In certain geographic regions, such as areas close to the equator, the PV array 310 can be tilted in different directions. The PV array 310 is often tilted differently to allow rainwater to flow away from the PV array 310, rather than to maximize exposure to solar radiation. As shown in FIG. 9, these differently tilted PV arrays 310 will require the forward-facing camera 222 to align to different pitch angles depending on the tilt angle of the PV array 310. The UAV 20 must be rotated 22 about the yaw axis 210a to change the pitch angle of the camera 222 according to the various tilt angles, which can be time consuming and likely to confuse the pilot. To address this issue, in some embodiments, the gimbal 228 is configured to change the camera 222 between a forward facing and a rear facing orientation, thereby changing its pitch angle without rotating 22 the UAV 20. In some other embodiments, the optical subsystem 220 of the UAV 20 may include two cameras 222, one facing forward and the other facing backward. Equivalent parameters for the backward facing camera may be obtained from those for the default forward facing camera, as follows: d xy ' = -d xy α pitch ' = -α pitch

[0049] The image sensor of the camera 222 used for EL measurements generally has an aspect ratio different from 1. For example, an image sensor with 640x512 pixels has an aspect ratio of 1.25. As shown in Figures 7A and 7B, the image sensor allows the camera's FOV 225 to capture the EL visual data set in portrait mode 235 or landscape mode 245. In portrait mode 235, a smaller but higher resolution subsection of the PV array 310 is captured in each EL visual data set. In landscape mode 245, a larger but lower resolution subsection of the PV array 310 is captured in each EL visual data set. Also, portrait mode 235 allows the UAV 20 to fly closer to the PV array 310 and at a lower height than landscape mode 245 due to the smaller FOV 225. The PV array subsection refers to the portion of the PV array 310 that is captured by the image sensor at any one time. A PV array subsection may include one or more PV modules 314 or portions thereof.

[0050] As shown in Figs. 6 and 8, the imaged distance (d img ) (which is the distance between the long sides of the PV array 310) represents the imaged distance of the nadir projection. The imaged distance (d FOV0 ) can be calculated as follows:

[0051]

number

[0052] To ensure that the PV array subsection is completely captured within the image sensor, additional space perpendicular to the scanning direction 360 is provided and the adjusted imaged distance (d) is adjusted so that the short side of the PV array subsection is completely within the camera's FOV 225. FOV For example, a space factor of 1.2 (f space ) allows for 10% extra space on each side. d FOV = d FOV0 f space

[0053] Camera FOV225 angle (α FOV ) perpendicular to the scanning direction 360, the distance (d L ) becomes:

[0054]

number

[0055] TOUR FUNCTION The UAV 20 may be equipped with obstacle detection and collision avoidance devices (such as, for example, Lidar device 224). These devices improve safety during operation because they can cause proximity alerts and prevent the UAV 20 from moving towards a detected obstacle 320. However, such obstacle detection devices may be unreliable, especially for semi-transparent obstacles 320 (such as, for example, glass structures and trees). EL measurements of the PV array 310 are usually performed at a height of approximately 4 to 15 meters (which is not above many buildings and trees), and therefore the risk of collision with these obstacles 320 is higher and it is important to mitigate this risk.

[0056] The process 400 includes a method 430 that represents a TOUR function for automated flight of the UAV 20 for imaging of a set of PV arrays 310. In many embodiments, the TOUR function performs automated flight of the UAV 20 for EL measurements. The TOUR function performs automated flight maneuvers between waypoints along the flight path 340 while avoiding obstacles 320 along the flight path 340 based on the EL measurement plan from the PLAN function. These waypoints include target points 350 corresponding to the PV arrays 310 for measuring the PV arrays 310 and a home base 330 for the UAV 20 to take off for EL measurements and land after capturing the EL visual dataset.

[0057] The TOUR function includes determining a flight path 340 between target points 350 for capturing an EL visual dataset of a PV array 310, with each PV array 310 corresponding to one or more target points 350. Each target point 350 has its coordinates, the height (d z ), and the camera yaw angle (α yaw ) and pitch angle (α pitch ) When the UAV 20 is positioned at a target point 350, the camera 222 is oriented to face a corresponding target view 352 (such as, for example, side points A and B discussed above).

[0058] Each flight path 340 between the target points 350 (particularly those shown in dashed lines in FIG. 3B ) is determined as the shortest route that avoids all known obstacles 320 (e.g., by going around or above them, etc.). The flight paths 340 can be calculated using a 3D spline function. The length of the flight path 340 is minimized by adjusting the positions of the knots of the 3D spline function, so that the flight path 340 does not cross any obstacles 320 and the flight path 340 is above a predefined minimum height 341. For each flight path 340, the number of knots is iteratively increased until a valid flight path 340 that meets these conditions (i.e., the flight path 340 does not cross any obstacles 320 and is above a predefined minimum height 341) can be found. As shown in the example in FIG. 10 , the shortest flight path 340 can be around or above 326 the obstacles 320. Optionally, the height 328 of the obstacle 320 can be arbitrarily altered to a value much greater than its actual height in order to cause the UAV 20 to go around the obstacle 320 rather than over it.

[0059] Alternatively, the flight path 340 can be calculated using a 2D spline function for a predefined constant height of the flight path 340, where the predefined constant height is above a predefined minimum height 341. The flight path 340 has a number of knots that are iteratively increased until a valid flight path 340 that does not intersect with any obstacles 320 can be found.

[0060] The TOUR function includes controlling UAV 20 for automated flight to each of the target points 350 along flight paths 340. Since all flight paths 340 between the target points 350 are determined (e.g., using a 3D spline function to find the shortest flight path 340), UAV 20 can be controlled for automated flight along these flight paths 340 such that the automated flight minimizes the overall flight duration.

[0061] 3B with several PV arrays 310 and corresponding target points 350, there are many permutations of target points 350 for planning flight path 340. UAV 20 is configured to capture six EL visual datasets (I1 to I6) of PV arrays 310. Since an EL visual dataset scanned by camera 222 from one target point 350 to another target point 350 is equivalent to scanning in the reverse direction, EL visual datasets captured in the forward direction (e.g., from target point A' to B') are denoted as EL visual datasets (I1 to I6) and those captured in the reverse direction (e.g., from target point B' to A') are denoted as EL visual datasets (I1' to I6'). The flight path 340 and flight duration between the home base 330, the target points 350 for capturing the forward EL visual data set (I1 to I6), and the target points 350 for capturing the reverse EL visual data set (I1' to I6') can be determined using the TOUR function.

[0062] As shown in FIG. 11, a triangular flight matrix 355 between these positions is calculated, indicating the flight duration between the home base 330 and the target point 350 (in both directions). The number of possible flight paths 340 is a non-repeating permutation (n!) with sequences that are not mirrors of each other (factor of 1 / 2). Additionally, the camera 222 can be used to fly in either the forward or reverse direction (2 n ), where n is the number of EL visual data sets (i.e., n=6), then the total number of possible flight paths 340 (N) is:

[0063]

number

[0064] When n=6, N=23040. There are 23040 permutations to scan the EL visual datasets (I1 to I6) of all PV arrays 310. Using a computational algorithm (e.g., brute force or k-nearest neighbors), an optimal flight sequence of target points 350 can be determined. Target points 350 in the optimal flight sequence minimize the overall flight duration of flight path 340, allowing EL measurements to be completed more quickly.

[0065] During the automated flight along the flight path 340, the camera 222 faces the front 20a of the UAV 20, and the yaw angle (α yaw) is the same as the yaw angle of the UAV 20. In one embodiment as shown in FIG. 12A, the orientation of the camera 222 is fixed and follows the flight path 340. In one embodiment as shown in FIG. 12B, the camera 222 is oriented such that the camera 222 always points at the PV array 310 corresponding to the next target point 350 to which the UAV 20 is flying. More specifically, the camera 222 always points at a target view 352 corresponding to the next target point 350 as the UAV 20 flies along the respective flight path 340 to the next target point 350, allowing the camera 222 to detect the EL signal from the PV array 310 early before the next target point 350 is reached. This supports the navigation by the pilot of the UAV and allows early correction of the flight path 340 if necessary (especially when flying at night or under low natural light conditions). To be able to detect the EL signal early, the UAV 20 should fly high enough above the PV array 310. Thus, the predefined minimum height 341 should be the maximum height 328 of the obstacle 320 along the flight path 340 plus a safety margin 324. The Lidar device 224 may measure the height of the UAV 20 relative to the roof of the obstacle 320. If the measured distance is within the safety margin 324, the UAV 20 should hover above the obstacle 320. If the measured distance is above the safety margin 324, and optionally below another larger value, an alert or warning message may be sent to the UAV pilot.

[0066] When the UAV pilot is at home base 330 and the UAV 20 is flying away from home base 330 towards target point 350, the pilot and camera 222 will face the same general direction. When the UAV 20 is returning to home base 330, the pilot and camera 222 will face the opposite direction. The yaw angle of the UAV 20 can be rotated by 180° so that the back of the UAV 20 faces the pilot, and the pilot and camera 222 continue to face the same general direction. This configuration allows for more intuitive manual control of the UAV 20 by the pilot, if desired.

[0067] When the UAV 20 is flying towards the target point 350, the maximum flight speed depends on the current distance between the UAV 20 and the target point 350 and the slope or curvature of the flight path 340. If the UAV is near the target point 350 or within a predefined distance from the target point 350, the flight speed will be gradually reduced to avoid overshooting and missing the target point 350. If the slope of the flight path 340 is too steep, the flight speed will also be reduced to avoid deviating from the flight path 340. The flight speed will be gradually reduced as the UAV 20 approaches the target point 350. Also, the flight height will be gradually reduced until it reaches a predefined minimum height 341 or within a distance d L gradually decreases until it reaches a predefined value.

[0068] In an embodiment as shown in FIG. 12B, the camera 222 is oriented such that it always faces the target view 352, which corresponds to the target point 350. However, in certain cases when the UAV 20 is approaching the target point 350, the camera 222 may not be able to keep facing the target view 352 all the time. Two possible cases are illustrated in FIG. 13. In case A, at position 1, the camera 222 faces the target view 352. After flying over the target view 352 towards the target point 350, the camera 222 changes its yaw angle (α yaw ) changes only slightly. As such, in position 2, the originally forward-facing camera 222 is now facing backwards, away from the target view 352. The UAV 20 continues to fly to the target point 350, and in position 3, the UAV 20 turns, allowing the camera 222 to face forward at the target view 350. Thus, between positions 2 and 3, the camera 222 temporarily loses sight of the target view 352. In order to keep the camera 222 always pointing at the target view 352, the yaw angle of the UAV 20 would need to change very quickly as it flies over the target view 352. However, as seen in case B, the rate at which the yaw angle of the UAV 20 is changed is too slow to keep the camera 222 aligned with the target view 352. In both cases A and B, the camera 222 loses view of the target view 352 for a short duration.

[0069] To address this issue of temporarily losing the target view 352, the flight path 340 to the target point 350 includes a circular path 342 that circles or circles around the target point 350 toward the target point 350. This allows the UAV 20 to circle or circle around the target point 350 as the UAV 20 approaches the target point 350 during automated flight along the circular path 342. The circular path 342 may include a target turning circle that is tangent to the target point 350. The length of the circular path 342 or the arc length of the target turning circle depends on the yaw angle (α) of the camera 222 in front of and at the target point 350. yaw The radius of the target turning circle is determined by the angular difference between the camera's yaw angle (α yaw ) and pitch angle (α pitch ) and by the minimum turning radius of the UAV 20 at the flight speed when the UAV 20 enters the circuit path 342. The algorithm for determining the circuit path 342 is described below with reference to four cases A to D, as shown in FIG.

[0070] i. Draw a first line 343 between the target point 350 and the corresponding target view 352. As shown in case A, the first line 343 is drawn based on the camera yaw angle (α yaw ) is consistent with

[0071] ii. Draw a second line 344 perpendicular to the first line 343 and through the target point 350 .

[0072] iii. Draw a third line 345 through the target view 352 perpendicular to the first line 343.

[0073] iv. Draw two target turning circles 346 that are tangent to the first line 343 on both the left and right side of the first line 343. The centers of the target turning circles 346 intersect with the second line 344.

[0074] v. The sector of the target turning circle 346 between the target point 350 and the target view 352 is referred to as the upper part, and the other sector is referred to as the lower part. Thus, there are four zones, which are generated by the two target turning circles 346 and separated by a first line 343 and a second line 344 (the upper left (TL) zone, the upper right (TR) zone, the lower left (BL) zone, and the lower right (BR) zone).

[0075] vi. The radius of the target turning circle 346 is determined such that the circumference is below the third line 345. If the circumference is above the third line 345, the target turning circle 346 must be shifted downward until they touch the third line 345. This ensures that the camera 222 can continue facing forward to see the target view 352. In case D, when the UAV 20 reaches the target point 350, the camera 222 changes from facing forward to facing backward to see the target view 352.

[0076] vii. For every UAV 20 position along the flight path 340, there are four tangents 347 that intersect the UAV 20 and are tangent to the target turning circle 346. The tangents 347 that are further away from the target point 350 are referred to as outer tangents and the tangents 347 that are closer to the target point 350 are referred to as inner tangents.

[0077] viii. As shown in case B, if the UAV 20 is in the TL zone, the UAV 20 follows the outer tangent 347 of the left target turning circle 346. If the UAV 20 is in the TR zone, the UAV 20 follows the outer tangent 347 of the right target turning circle 346. As shown in case C, if the UAV 20 is in the BR zone, the UAV 20 follows the inner tangent 347 of the right target turning circle 346. If the UAV 20 is in the BL zone, the UAV 20 follows the inner tangent 347 of the left target turning circle 346.

[0078] ix. As shown on the right side of FIG. 14, in each of cases A through C, UAV 20 follows a respective tangent line 347 and approaches target point 350 while camera 222 continues to face target view 352. UAV 20 continues along tangent line 347 until it touches target turning circle 346. UAV 20 then follows the arc of target turning circle 346 until it reaches target point 350 or first line 343. If UAV 20 reaches first line 343 first, UAV 20 continues to move linearly along first line 343 until it reaches target point 350.

[0079] Yaw angle (α yaw ) and pitch angle (α pitchThe rate of change of the rotational path 342 can be maintained constant as the UAV 20 flies along the circular path 342 to the target point 350. As shown in FIG. 15A, the UAV 20 is in the TR zone and flies along the outer tangent 347 of the right target turning circle 346. As the flight speed gradually decreases as the UAV 20 approaches the target point 350, the constant rate will cause a larger difference between the yaw and pitch angles the closer the UAV 20 is to the target point 350. This allows the radius of the target turning circle 346 to gradually decrease as the UAV 20 approaches the target point 350. This, in turn, results in the circular path 342 forming a shorter spiral path and a shorter flight duration.

[0080] Alternatively, as shown in FIG. 15B , the orbital path 342 can be shortened by flying the UAV 20 instead along the inner tangent 347 of the right target turning circle 346 and by flying over the PV array 310. The UAV 20 is initially in the TR zone with the camera 222 facing forward to the target view 352. As the UAV 20 flies over the PV array 310 and specifically over the target view 352 towards the target point 350, the camera 222 changes from a forward facing to a rear facing orientation. This allows the camera 222 to continue facing the target view 352 as the UAV 20 flies over the target view 352 and arrives at the target point 350.

[0081] The target points 350 may be very close to each other without any obstacles 320 between them, such as target points 350 corresponding to adjacent PV arrays 310. A pair of target points 350 are adjacent to each other, and the flight path 340 between them can be simplified to a straight line shift. This is because the target points 350 have the same height, yaw angle (α yaw ), and pitch angle (α pitch) while allowing the UAV 20 to fly along a straighter flight path 340 for a shorter flight duration.

[0082] The TOUR function includes controlling the UAV 20 for autopilot at each one or more target points 350 to capture the EL visual dataset of the respective PV array 310 using the camera 222. Thus, when the UAV 20 reaches a target point 350 (e.g., target point A', etc.) and is looking at a corresponding target view 352 (e.g., target view A, etc.), the UAV 20 is controlled for autopilot at target point A' to capture the EL visual dataset of the corresponding PV array 310. In this autopilot, the UAV 20 can move from target point A' (looking at target view A) to target point B' (looking at target view B) to capture the EL visual dataset of the PV array 310 bounded by side points A and B. The scanning path 360 of this autopilot is shown in FIG. 3B as a dotted line and is further described below in method 440 or the SCAN function.

[0083] In some cases, the EL measurement plan from the PLAN function may contain errors, such as incorrect coordinates for the target point 350. For example, the target point 350 should correspond to a particular target view 352, but if the coordinates for the target point 350 are incorrect, such as due to measurement errors, the UAV 20 may not be pointing at the correct target view 352 when it arrives at these coordinates via the TOUR function. Instead, as shown in FIG. 16 , the UAV 20 will be pointing at an incorrect target view 354 as it approaches the PV array 310. As the UAV 20 approaches the PV array 310, the camera 222 may detect an EL signal from the PV array 310, and a PV array subsection may appear within the camera's FOV 225. However, as the UAV 20 approaches the PV array 310, the PV array subsection shifts out of the FOV 225, resulting in the camera 222 losing the EL signal and the FOV 225 focusing on an incorrect target view 354. As the UAV 20 approaches the PV array 310, when the PV array subsection is visible in the FOV 225, a reference point 380 on the PV array subsection currently visible in the FOV 225 can be determined. For example, the reference point 380 is the center 522 of the rectangle 520 described below with respect to the SCAN function. When the UAV 20 gets close enough to the PV array 310, the PV array subsection disappears from the FOV 225 and the reference point 380 cannot be determined. The reference point 380 of the PV array subsection last visible in the FOV 225 before it disappeared (i.e., the last reference point 380) is converted to a corrected target point 350 based on the current position and orientation of the UAV 20.

[0084] The UAV 20 can be controlled to move from the current target point 350 (having incorrect coordinates and facing an incorrect target view 354) to the corrected target point 350. The UAV 20 at the corrected target point 350 will face the last reference point 380 and the PV array subsection will be visible in the FOV 225, allowing the UAV 20 to continue the SCAN function. In one embodiment, the TOUR function determines the last reference point 380 and the corrected target point 350 upon losing the PV array subsection from the FOV 225. The TOUR function also recalculates the flight path 340 from the current position of the UAV 20 to the corrected target point 350, and automatically moves the UAV 20 from the current position to the corrected target point 350. In another embodiment, after determining the last reference point 380 and the corrected target point 350, the corrected target point 350 is displayed on the remote device 260 controlling the UAV 20. The pilot then selects the corrected target point 350, recalculates the flight path from the current position of the UAV 20 to the corrected target point 350, and controls the UAV 20 to move to the corrected target point 350. Additionally, after losing the EL signal, a warning message can be sent to the remote device 260 to alert the pilot and provide an option to correct the target point 350 based on the last reference point 380.

[0085] Thus, the TOUR function controls the UAV 20 to fly towards the target point 350 to capture the EL visual dataset of the corresponding PV array 310. If the EL signal of the PV array 310 is detected by the camera 222, the TOUR function proceeds to method 440 or SCAN function of the process 400 to capture the EL visual dataset of the PV array 310. After capturing the EL visual dataset of the PV array 310, the UAV 20 flies towards the next target point 350 via the TOUR function to capture the EL visual dataset of the next PV array 310. However, if the EL signal is not detected, this may mean that the PV array 310 is inactive or the target point 350 is incorrect. The TOUR function then proceeds to correct the target point 350 as described above. However, if the PV array 310 is still not detected by the camera 222 despite this correction, the TOUR function can proceed to method 450 of the process 400, which represents a FIND function to find the closest active PV array 310 with an EL signal. Details of the FIND function are described in PCT application WO2021137764, which is incorporated herein by reference.

[0086] As described above, the TOUR function performs automated flight maneuvers along the flight path 340 based on an EL measurement plan that includes location details of the target point 350 and flight maneuvers. In some situations, an EL measurement plan does not exist or does not include sufficient details about the target point 350 and / or flight maneuvers. The target point 350 will be determined based on the pilot's interaction with the remote device 260 that controls the UAV 20. Software running on the remote device 260 displays an interactive map 500 as shown in FIG. 17. When the UAV 20 is flying and the camera 222 views the PV array 310, the PV array subsection appears in the interactive map 500. The pilot can select a side point 352 of the PV array subsection. The software then generates the target point 350 based on the selected side point 352 and the current position and orientation of the UAV 20, as well as the transformation of the final reference point 380 to the corrected target point 350 described above. The pilot selects another function, calculates a flight path 340, and controls the UAV 20 to fly toward the generated target points 350. Thus, through the interactive map 500, the TOUR function can generate a series of target points 350 and calculate their flight paths 340 based on selected points (e.g., side points 352, etc.) of the PV array 310. This requires more manual control by the pilot, but eliminates the need for an EL measurement plan or the need to know the target points 350 in advance.

[0087] SCAN Function The process 400 includes a method 440 representing a SCAN function for automated imaging of a PV array 310 using a UAV 20, where the PV array 310 corresponds to target points 350 for the UAV 20. For example, the target points 350 include target points A′ and B′, which correspond to target view 352 or side points A and B, respectively, of the PV array 310, as shown in FIG. 6 . In many embodiments, the SCAN function performs automated EL measurements of the PV array 310.

[0088] The SCAN function includes positioning the UAV 20 at one of the target points 350 corresponding to the PV array 310. For example, the UAV 20 is controlled using the TOUR function for automatic flight along the respective flight path 340 to the target point 350 (e.g., target point A', etc.). The SCAN function further includes controlling the UAV 20 for automatic navigation between the target points 350 to capture the EL visual dataset of the PV array 310. For example, the UAV 20 performs automatic navigation along a lateral scanning direction 360 from target point A' to target point B' to capture the EL visual dataset.

[0089] The SCAN function can be divided into six incremental levels of automation (Level 0 to Level 5) for automated EL measurements, with SCAN function Level 0 requiring full manual control by the UAV pilot and SCAN function Level 5 requiring minimal manual control or being fully automated.

[0090] At SCAN capability level 0, the UAV 20 is manually controlled by the pilot and flown between target points 350 (e.g., between target points A' and B'). The pilot also manually aligns the camera's optical axis 222a to be perpendicular to the PV array 310. For optimal EL measurements, the pilot sets the distance between the UAV 20 and the PV array 310 such that the short side of the PV array subsection is completely within (preferably filling) the FOV 225. The pilot can also manually adjust various parameters of the camera 222, some of which are described in PCT application WO2021137764 (incorporated herein by reference). Non-limiting examples of camera parameters include camera focus, exposure, signal-to-noise ratio, and sharpness.

[0091] In SCAN capability level 1, alignment of the PV array subsection with the FOV 225 is performed via autopilot after the UAV 20 is positioned at the target point 350. The autopilot includes aligning the FOV 225 with the PV array subsection (i.e., the portion of the PV array 310 currently being captured by the image sensor of the camera 222). As shown in FIG. 18, the EL signal of the forward-biased PV array 310 in the FOV 225 is typically significantly larger than the inactive background 510, so that the EL signal of the PV array subsection of the PV array 310 can be identified and aligned with the FOV 225.

[0092] In some embodiments, aligning the FOV 225 includes detecting the polygonal outline of the PV array subsection. Because the PV modules 314 are rectangular and the PV array 310 is typically arranged in a regular manner, the EL signal or image of the PV array subsection can be outlined by a polygon (such as a square, or more preferably a rectangle). If the camera's optical axis 222a is nearly perpendicular to the PV array 310, the polygon will have a center 522 (x R , y R ), width (w R ), height (h R ), and the rotation angle (α R ) can be approximated as a rectangle 520 having

[0093] As an example, detecting the polygon outline (rectangle 520) can be described by an image processing algorithm as follows: The image processing algorithm includes converting the EL image frame of the PV array subsection from the EL visual dataset (if it originally has multiple color channels) to monochrome or grayscale. The image processing algorithm includes binarizing the EL image frame by setting all image intensities above a predefined threshold to a non-zero value (e.g., 1) and setting other image intensities to zero. Otsu's method for automatic image thresholding can be used to obtain this threshold. The image processing algorithm further includes detecting contours around all non-zero objects in the binarized EL image frame, and a rectangle 520 is defined around the detected contours. More specifically, the image processing algorithm excludes small objects from the detected contours and finds the smallest rectangle 520 around all remaining detected contours to exclude objects from non-EL sources.

[0094] Referring to FIG. 19, the step of aligning the FOV 225 includes determining the pitch angle misalignment (m 225 ) based on the detected polygon outline (rectangle 520 ). pitch The step of aligning the FOV 225 further includes calculating the pitch angle misalignment (m pitch ) to change the camera pitch angle (α pitch More specifically, the rectangle 520 is aligned with the longitudinal center (y c ) and is centered on the longitudinal center (y R ) is the longitudinal center of FOV225 (y c ) is coincident with the lateral centerline passing through the pitch angle misalignment (m pitch ) can be calculated as follows:

[0095]

number

[0096] In some embodiments, instead of detecting the polygon outline, the step of matching the FOV 225 includes calculating an image histogram of the EL image frame and calculating the center of the EL image frame based on the image histogram. For example, the EL image frame center (y R The EL image frame center (y ) can be calculated from the center of the peak obtained from the sum of the row and column average values ​​in the image histogram. R ) and size can be calculated, but the rotation angle (α R ), may be missing, but this, as well as other missing information, can be obtained through other methods or sources. Alternatively, in some embodiments, bounding box techniques can be used to detect the PV array subsection or each PV module 314 within the PV array subsection.

[0097] In SCAN function level 1, the autopilot adjusts the camera pitch angle (α pitch ) to automate the alignment of the FOV 225 with respect to the PV array subsections. The pilot manually controls the UAV 20 to make other adjustments to improve the alignment of the FOV 225 with respect to the PV array subsections.

[0098] At SCAN function level 2, the autopilot optimizes the alignment of the FOV 225 to the PV array subsection. More specifically, aligning the FOV 225 may include aligning a pair of guide lines 530 of the FOV 225 to the PV array subsection. In an embodiment in which the SCAN function is performed along the side-to-side scanning direction 360a, the guide lines 530 are aligned at a distance (d T ) offset by the smaller offset distance (d T ) allows the PV array subsection to fill a larger area of ​​the FOV 225, but requires the camera 222 to have better positional stability and accuracy. T ) is the overall height (h FOV ) is approximately 10% of the total.

[0099] The rectangle 520 can be rotated relative to the PV array subsection, and aligning the FOV 225 includes determining the rotational misalignment (m) between the rectangle 520 and the PV array subsection based on the offset guide lines 530 and the rotated rectangle 520. yaw ) can be included in calculating the rotational misalignment (m yaw ) is the rotation angle (α R ) and the offset guide wire 530. The step of aligning the FOV 225 is calculated from the minimum angular difference between the rotational misalignment (m yaw) (e.g., by rotating the UAV 20 about the yaw axis 210a) to determine the yaw angle (α yaw )

[0100] The step of aligning the FOV 225 is based on the current pitch angle (α pitch ) and the desired pitch angle, the roll axis misalignment (m y In particular, the desired pitch angle is calculated by multiplying the tilt angle (α tilt ) is equivalent to the current pitch angle (α pitch ) is the desired pitch / tilt angle (α tilt ) (Case A), equal to (Case B), and less than (Case C). The step of aligning the FOV 225 involves adjusting the roll axis misalignment (m y ) along the roll axis 210b. y If the roll axis misalignment (m) is negative, then the UAV 20 must be shifted backward along the roll axis 210b, away from the PV array 310. y ) is positive, then the UAV 20 should be shifted forward along the roll axis 210b, toward the PV array 310.

[0101] The step of aligning the FOV 225 involves determining the vertical misalignment (m z )

[0102]

number

[0103] If the PV array subsection fills too small an area within the FOV225, vertical misalignment (m z ) is negative, and the UAV 20 should be shifted vertically downward to enlarge the PV array subsection within the FOV 225. However, if the distance between the UAV 20 and the PV array 310 is below a predefined minimum safe distance, a negative vertical misalignment (m z ) should be reset to zero to prevent the UAV 20 from colliding with the PV array 310. If the PV array subsection fills too large an area in the FOV 225, the vertical misalignment (m z ) is positive, and the UAV 20 should be shifted vertically upward to shrink the PV array subsection within the FOV 225. However, the vertical misalignment (m z ) is positive, and the roll axis misalignment (m y If m is positive, this means that the UAV 20 is vertically too close to the PV array 310, and the roll axis misalignment (m y ) should be reset to zero to prevent the UAV 20 from colliding with the PV array 310.

[0104] At SCAN capability level 2, the autopilot automates the alignment of the FOV225 by one or more of the following misalignment parameters: pitch angle misalignment (m pitch ), rotational misalignment (m yaw ), roll axis misalignment (m y ), and vertical misalignment (m z). Adjustments of the UAV 20 and / or camera 222 with the misalignment parameters for alignment with the PV array subsection can be made by speed control and / or position control as described above. Once the PV array subsection edge is aligned with the guide line 530 through the autopilot, all misalignment parameters are reset to zero, causing the UAV 20 to hover at the appropriate location. The pilot can manually control the UAV 20 to perform other alignment adjustments or override the autopilot, if necessary. For example, the pilot may need to counter an alignment action by the autopilot due to an inaccurate or erroneous calculation of the misalignment parameters.

[0105] At SCAN capability level 3, after the FOV 225 is aligned with the PV array subsection, the autopilot controls the movement of the UAV 20 to move the UAV 20 along the PV array 310 and capture an EL visual dataset of the PV array 310. The autopilot includes determining a scanning direction 360 for moving the UAV 20 between the target points 350. For example, if the locations of the target points A' and B' are known in advance, the scanning direction 360 can be determined from the known locations, and the UAV 20 is controlled to move from the start target point A' to the end target point B'.

[0106] In some embodiments, the scanning direction 360 is adjusted to account for the pitch axis misalignment (m x ) can be determined based on the pitch axis misalignment (m x ) can be calculated as follows:

[0107]

number

[0108] With the PV array subsection aligned inside the FOV 225, a scanning direction 360 can be determined if a side point 352 of the PV array subsection is inside the FOV 225. Referring to FIG. 21 , in case A, the left side point 352 is inside the FOV 225 and is located at the lateral center (x R ) is the horizontal center of FOV225 (x c ) to the right of the longitudinal centerline (i.e., x R >x c ), the scanning direction 360 will be a lateral direction to the right. In case C, the right side point 352 is inside the FOV 225 and is located at the lateral center (x R ) is to the left of the longitudinal centerline of the FOV225 (i.e., x R <x c ), the scanning direction 360 will be a lateral direction to the left. In case B, the side point 352 is not visible inside the FOV 225 (i.e., x R ≒x c ), the pilot must manually shift the UAV 20 along the pitch axis (parallel to the scanning direction 360) until one of the side points 352 comes into view.

[0109] After determining the scanning direction 360 (i.e., either a lateral direction to the left or to the right), the autopilot includes capturing an EL visual dataset of the PV array 310, starting with the PV array subsection, as the UAV 20 moves along the scanning direction 360 between the target points 350. More specifically, at different points along the scanning direction 360, the UAV 20 captures an EL visual dataset (including a series of EL image frames and / or videos) of a different PV array subsection. The autopilot can gradually increase the UAV movement speed as the UAV 20 moves along the scanning direction 360 to minimize jerky movement. Additionally, the autopilot may continue to calculate the misalignment parameters as the UAV 20 moves along the scanning direction 360 and may reduce the movement speed if the misalignment parameters violate certain predefined conditions (e.g., if the absolute values ​​of the individual misalignment parameters are too large, which may suggest that the FOV 225 is no longer properly aligned with the PV array subsection). The autopilot may stop capturing when the UAV 20 reaches another target point 350 (end target point B').

[0110] At SCAN function level 4, the SCAN function may include receiving geolocation data of the UAV 20. The geolocation data (e.g., from a GPS module in the UAV 20) improves the positioning of the UAV 20 during autopilot. The pitch axis misalignment (m x) increases, the travel speed decreases, and the UAV 20 should stop at the end target point B'. However, due to the inertia of the UAV, the deceleration may be insufficient to overcome the travel speed as the UAV 20 approaches the end target point B'. This is due to the pitch axis misalignment (m x ) continues to increase, causing the UAV 20 to overshoot the ending target point B'. Moreover, the UAV 20 may overshoot and hover at a position where the PV array subsection is not visible in the FOV 225. Without any PV array subsections visible in the FOV 225, autopilot cannot be implemented and the UAV 20 may not be able to fly to the next target point 350 to continue capturing the EL visual data set. To combat this challenge, the SCAN function may include returning the UAV 20 to its last position based on geolocation data, where the PV array subsection was last visible in the FOV 225 and / or where the pitch axis misalignment (m x ) was below a predefined absolute value (for example, 0.7).

[0111] In some cases, the PV array 310 may have gaps and / or broken PV modules 314, resulting in some areas of the PV array 310 without any EL signal, and the UAV 20 will not be able to detect these areas for EL measurements. If these areas exceed the overall width (w FOV ), the autopilot may stop capturing the EL visual dataset before or after UAV 20 reaches end target point 350. For example, the autopilot may stop capturing at the start of those areas that do not have any EL signal from the perspective of FOV 225 as UAV 20 moves along scanning direction 360.

[0112] At SCAN functionality level 5, details of the target points 350 and the orientation of the UAV 20 and camera 222 to align with each target point 350 and the corresponding PV array 310 in the target view 352 are known in advance (e.g., from the PLAN functionality).

[0113] The SCAN function includes positioning the UAV 20 at one of the target points 350 corresponding to the PV array 310. For example, the UAV 20 is controlled using the TOUR function for automatic flight to the starting target point 350. The SCAN function includes controlling the UAV 20 for automatic piloting between the target points 350 to capture an EL visual data set of the PV array 310. The automatic piloting includes aligning the camera's FOV 225 to a PV array subsection of the PV array 310 and determining a scanning direction 360 for moving the UAV 20 between the target points 350. When the orientation of the UAV 20 and the camera 222 is known in advance, the FOV 225 will be properly aligned upon positioning of the UAV 20 at the starting target point 350, and the scanning direction 360 is also known (from the starting target point 350 to the ending target point 350). The autopilot includes capturing an EL visual dataset of the PV array 310 starting from the PV array subsection as the UAV 20 moves along a scanning direction 360 between a start target point 350 and an end target point 350. Thus, SCAN capability level 5 fully automates the EL measurements of the PV array 310, starting capture of the EL visual dataset when the UAV 20 is positioned at the start target point 350 and ending it when the UAV 20 reaches the end target point 350.

[0114] Although the SCAN function is described herein in an embodiment in which the UAV 20 captures an EL visual data set while moving along a sideward scanning direction 360a (see FIG. 7A), it will be appreciated that various aspects of the SCAN function are equally or similarly applicable to the forward scanning direction 360b (see FIG. 7B). It will also be appreciated that the calculations of the misalignment parameters and alignment adjustments may be modified accordingly with respect to the forward scanning direction 360b. For example, the pitch angle (α pitch ), the roll angle (α roll ) is the tilt angle (α tilt ) The roll angle misalignment parameter is used to match the pitch angle misalignment (m pitch For example, the guide lines 530 are calculated at distances (d T ) on the left and right sides.

[0115] COMBI function In some embodiments, the TOUR function and the SCAN function can be combined as a COMBI function or method 460 of the process 400. The COMBI function provides a method for automatic flight of the UAV 20 and automatic imaging of a set of PV arrays 310 using the UAV 20. The COMBI function can be initiated when a complete measurement plan from the PLAN function is available. In many embodiments, the COMBI function performs automatic flight of the UAV 20 and automatic EL measurement of the PV arrays 310 using the UAV 20, and the COMBI function can be initiated when a complete EL measurement plan is available.

[0116] The COMBI function includes determining a flight path 340 between target points 350 for capturing the EL visual dataset of the PV arrays 310, each PV array 310 corresponding to a pair of start and end target points 350 (e.g., target points A' and B'). The COMBI function includes controlling the UAV 20 for automatic flight along the flight path 340 to the respective start target points 350 of the PV arrays 310. The COMBI function includes controlling the UAV 20 for automatic flight between the respective start and end target points 350 of the respective PV arrays 310 for capturing the EL visual dataset of the PV arrays 310 using the camera 222. For each PV array 310, the autopilot includes aligning the camera FOV 225 with a PV array subsection of the PV array 310, determining a scanning direction 360 for moving the UAV 20 between a start target point 350 and an end target point 350, and capturing an EL visual dataset of the PV array 310 using the camera 222 starting from the PV array subsection as the UAV 20 moves along the scanning direction 360 between the start target point 350 and the end target point 350.

[0117] It will be appreciated that various aspects of the TOUR and SCAN functions described above may be equally or similarly applied to the COMBI function and vice versa, and will not be described further for purposes of brevity.

[0118] As described above, the channels 34 can be selectively activated (e.g., by a field worker or by the remote device 260) to place the PV strings 312 under a forward bias condition and to generate an EL signal from the PV array 310. Preferably, the remote device 260 can control the UAV 20 and the channels 34 such that the execution of the EL measurement plan via the COMBI function can be fully automated with minimal or no human intervention. However, even if the COMBI function is fully automated, the pilot and other field workers should continue to observe the UAV 20 to ensure safety management and prevent accidents. For example, the remote controller held by the pilot can include a deadman switch that must be pressed continuously or periodically. For example, the UAV 20 can be configured with another camera or eye tracker that tracks the pilot's eye to ensure the pilot's attention to the UAV 20.

[0119] After completing the SCAN or COMBI function, the captured EL visual dataset of the PV array 310 can undergo further image processing to obtain a processed EL image of the PV array 310. An example of such image processing is described in PCT application WO2021137764, which is incorporated herein by reference. For example, a raw EL image from the EL visual dataset can be extracted and sent for an image enhancement process. Multiple processed EL images of the PV array subsections can be aligned and combined to form a combined processed EL image of the corresponding PV array 310. The processed EL image of the PV array 310 can be mapped onto a base map of the PV installation 300 for better visualization of the processed EL image for the PV installation 300.

[0120] Details of the processed EL images (e.g., image characteristics, current used for EL measurement, and the identifier of each PV array 310) can be stored on a database for further analysis. This database allows quantitative comparison of the processed EL images with past EL images of the same PV array 310. For example, the pixel intensity histogram of the EL image depends on the current as well as the camera parameters (e.g., exposure time, gain, ISO, aperture, and transmittance of the lens 223). The pixel intensity has a predetermined range of values ​​(e.g., 0 to 255 for an 8-bit camera 222), and these values ​​can be mapped to absolute luminance values ​​based on a technical standard. Since the characteristics of the EL image can vary depending on the type of camera 222 and the camera characteristics, different EL images of the same PV array 310 can be mapped according to absolute luminance values ​​for quantitative comparison. This technical standard can also be used by different EL measurement contractors so that their EL images are comparable to others.

[0121] The embodiments of the present disclosure herein describe a process 400 for automatic flight of the PV array 310 and automatic imaging of the PV array 310 (e.g., EL measurement, etc.). The process 400 describes various key functions, including DATA, PLAN, TOUR, SCAN, and COMBI functions, as well as various automation levels of the SCAN function. The automatic flight and imaging reduces the overall time it takes to complete imaging of the PV array 310. The UAV 20 can perform the process 400 and operate independently with minimal or no human intervention. Thus, the process 400 is feasible for imaging of large PV installations 300 with many PV arrays 310. More PV arrays 310 can be measured at a faster rate and with less personnel, thereby improving overall efficiency. Also, the quality of the EL visual dataset and the processed EL image will be better because the UAV 20 is properly aligned with the PV array 310 by the autopilot.

[0122] In the preceding detailed description, embodiments of the present disclosure relating to aircraft and methods for automated flight and imaging of PV arrays according to the present disclosure have been described with reference to the figures provided. Although these embodiments have been described with respect to EL or electroluminescence measurements of PV arrays, the aircraft and methods described herein can be used with other imaging techniques (e.g., visible, thermal (infrared), ultraviolet (UV) fluorescence, and photoluminescence (PL) imaging, etc.). For example, with respect to PL imaging, the photoluminescence of the PV array can be generated by a light source instead of a power supply. For example, with respect to UV fluorescence, a fluorescent signal from the PV array can be generated by illuminating the PV array with UV light. It will be recognized that various aspects of the embodiments described herein with respect to EL imaging or measurements can be applied in a similar or analogous manner to other imaging techniques (e.g., visible, infrared, UV, and PL imaging, etc.).

[0123] The description of various embodiments herein is not intended to call out or be limited to only specific or particular expressions of the present disclosure, but is merely intended to illustrate non-limiting examples of the present disclosure. The present disclosure serves to address at least one of the above-mentioned problems and issues associated with the prior art. Although only some embodiments of the present disclosure are disclosed herein, it will be apparent to those skilled in the art upon consideration of the present disclosure that various variations and / or modifications can be made to the disclosed embodiments without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure and the appended claims are not limited to the embodiments described herein. [Explanation of symbols]

[0124] 10 PV equipment 10a Longitudinal axis 11 PV array 12 PV strings 14 PV modules 16 Combiner Box 20 Unmanned Aerial Vehicle (UAV) 20a UAV20 Front 32 Switcher Box 34 Channels 36 Power supply section 100 Inspection Setup 200 Optical Subsystem 210 Main body part 210a Yaw axis 210b Roll axis 220 Optical Subsystem 222 Camera 222a optical axis 223 Focusing Lens 224 Lidar devices 224a optical axis 225 Camera Field of View (FOV) 226 Laser 226a optical axis 228 Gimbal 230 Propulsion Devices 232 Propeller 234 Motor 235 Portrait Mode 240 On-Board Processing Subsystem 245 Landscape Mode 250 Controller 252 Memory Unit 260 Remote Devices 262 processor 264 Memory Unit 300 PV equipment 310 PV array 312 PV string 314 PV Module 316 connection points 320 Obstacles 322 Border 324 Safety Margin 326 Upper 328 Maximum height of obstacle 320 330 Home Base 340 Flight Path 341 Minimum Height 343 First Line 344 Second Line 345 The Third Line 346 Target Turning Circle 347 Tangent line 350 Target Points 352 Side Point, Target View 354 Incorrect target view 355 Triangular Flight Matrix 360 Scanning path, scanning direction 360a Sideways scanning direction 360b forward scanning direction 370 3D Digital Surface Models (DSM) 372 Horizontal intersecting plane 374 Intersection Height 380 Reference Points 400 processes How to represent the 410 DATA function 420 How to represent the PLAN function How to represent the 430 TOUR features How to represent the 440 SCAN function How to represent the 450 FIND function 460 COMBI function 500 interactive maps 510 Inactive Background 520 rectangle 522 Center of rectangle 520 530 Guide Line A, B side points, target view A' Starting target point B' End target point BL Bottom Left Zone BR Lower Right Zone d baro Current flight height of UAV20 d FOVAdjusted Imaged Distance d FOV0 Imaged distance within the camera's FOV225 d img Imaged Distance d L The distance between the UAV 20 and the PV array 310 along the surface normal d T Offset Distance d xy The distance between the target point 350 and the target view 352 d z PV array 310 height h R height I1-I6 EL visual dataset I1'~I6' Reverse EL visual data set m pitch Pitch Angle Misalignment m y Roll axis misalignment m yaw Rotational Misalignment m z Vertical Misalignment n1~n14 Waypoints P1, P2 connection points S1, S2, S3 PV strings TL Top Left Zone TR upper right zone w R width x c Horizontal center of FOV225 x R Horizontal center of rectangle 520 y c Longitudinal center of FOV225 y R Longitudinal center of rectangle 520 α bearing Azimuth angle of PV array 310 α FOV Camera FOV225 angle α pitch Pitch angle of camera 222 α R Rotation angle α roll Roll angle of camera 222 α shift Shift angle α tilt Tilt angle of PV array 310 α yaw Camera yaw angle

Claims

1. 1. A method for automated electroluminescence (EL) imaging of a PV array using an aircraft, the PV array corresponding to a target point for the aircraft, the method comprising: positioning the aircraft at one of the target points corresponding to the PV array; controlling the aircraft for autopilot between the target points to capture a visual data set of the PV array; Including, The autopilot implemented by the aircraft comprises: aligning a field of view (FOV) of a camera of the aircraft to a PV array subsection of the PV array; positioning a target viewpoint of the PV array corresponding to said one of the target points within the aligned FOV; determining a scanning direction for moving the aircraft between the target points with reference to the positioned target viewpoints; capturing the visual data set of the PV array using the camera, starting with the PV array subsection, as the aircraft moves along the scanning direction between the target points; A method comprising:

2. The method of claim 1 , wherein matching the FOV comprises detecting a polygonal outline of the PV array subsection.

3. aligning the FOV includes calculating a pitch angle misalignment based on a contour of the detected polygon; and aligning the FOV includes adjusting a pitch angle of the camera according to the pitch angle misalignment such that the polygon outline is centered on the FOV. The method of claim 2.

4. aligning the FOV includes calculating a roll axis misalignment based on an angular difference between a current pitch angle and a desired pitch angle of the camera; and aligning the FOV includes steering the aircraft along a roll axis with the roll axis misalignment such that an optical axis of the camera is perpendicular to the PV array. The method according to claim 2 or 3.

5. 5. The method of claim 2, wherein aligning the FOV comprises aligning a pair of guide lines of the FOV to the PV array subsection, the guide lines being offset from an edge of the FOV.

6. aligning the FOV includes calculating a rotational misalignment between the polygon outline and the PV array subsection based on the offset guide lines and the polygon outline; and aligning the FOV includes adjusting a yaw angle of the camera according to the rotational misalignment. The method according to claim 5.

7. The method of claim 5 or 6, wherein aligning the FOV comprises calculating a vertical misalignment based on the offset guide lines and the polygon outline.

8. 8. The method of claim 1, wherein the scanning direction is determined based on a pitch axis misalignment between the aligned FOV and the PV array subsection.

9. 9. The method of claim 1, wherein the autopilot comprises: calculating misalignment parameters as the aircraft moves along the scanning direction; and reducing a speed of movement of the aircraft if the misalignment parameters violate a predefined condition.

10. The method of claim 1, further comprising the steps of: receiving geolocation data for the aircraft; returning the aircraft to a previous position based on the geolocation data; Further comprising: The method of claim 1 , wherein at the previous position the PV array subsection was last visible in the FOV.

11. 1. An aircraft for automated electroluminescence (EL) imaging of a PV array, the aircraft comprising: a propulsion device for actuating movement of the aircraft; a camera for capturing a visual dataset of the PV array, the PV array corresponding to a target point for the aircraft; and a controller communicatively connected to the camera and the propulsion device; Including, The controller: configured to position the aircraft at one of the target points corresponding to the PV array; configured to control the aircraft for autopilot between the target points to capture the visual data set of the PV array; The autopilot implemented by the aircraft comprises: aligning a field of view (FOV) of a camera of the aircraft to a PV array subsection of the PV array; positioning a target viewpoint of the PV array corresponding to said one of the target points within the aligned FOV; determining a scanning direction for moving the aircraft between the target points with reference to the positioned target viewpoints; capturing the visual data set of the PV array using the camera, starting with the PV array subsection, as the aircraft moves along the scanning direction between the target points; Including, aircraft.

12. 1. A method for automated flight of an aircraft to perform imaging of a set of PV arrays, the method comprising: determining flight paths between target points for capturing visual datasets of the PV arrays, each PV array corresponding to one or more target points; controlling the aircraft for automated flight along the flight path to each of the target points; controlling the aircraft for autopilot at each of the one or more target points to capture the visual data set of each PV array using a camera on the aircraft; Including, the autopilot implemented by the aircraft includes moving the aircraft along a scanning direction determined with reference to a target viewpoint of the PV array corresponding to each one of the target points from each one of the target points.

13. Each flight path is calculated using a 3D spline function, the length of each flight path is minimized by adjusting the positions of the knots of the 3D spline function, such that the flight paths do not intersect with any obstacles and are above a predefined minimum height; the number of knots is iteratively increased to determine the flight path that does not intersect any obstacles and is above the predefined minimum height; The method of claim 12.

14. controlling the aircraft for automated flight includes controlling the camera to always point at the PV array corresponding to a next target point as the aircraft flies to the next target point along each of the flight paths; each flight path to each target point includes a circular path around and toward the target point; each flight path to each target point includes a circular path around and toward the target point; 14. The method according to claim 12 or 13.

15. 15. The method of claim 14, wherein the aircraft is controlled to fly along an outer tangent to the target turning circle, and controlling the aircraft for automatic flight includes reducing a flight speed of the aircraft as the aircraft approaches the target point such that a radius of the target turning circle decreases and the orbital path forms a shorter spiral path.

16. 15. The method of claim 14, wherein the aircraft is controlled to fly over the PV array along an inner tangent to the target turning circle, and the camera is configured to change from a forward facing to a rear facing orientation as the aircraft flies over the PV array.

17. determining a reference point on a PV array subsection of the PV array, the PV array subsection being visible within a field of view (FOV) of the camera as the aircraft approaches the PV array; determining a last reference point of the PV array subsection that was last visible within the FOV when the PV array subsection is dropped from the FOV; converting the last reference point to a corrected target point; and recalculating the flight path from a current position of the aircraft to the corrected target point.

17. The method according to any one of claims 12 to 16.

18. 1. An aircraft for autonomous flight to perform imaging of a set of PV arrays, the aircraft comprising: a propulsion device for actuating movement of the aircraft; a camera for capturing a visual dataset of the PV array; and a controller communicatively connected to the camera and the propulsion device; Including, The controller: configured to determine flight paths between target points for capturing the visual data set of the PV arrays, each PV array corresponding to one or more target points; configured to control the aircraft for automated flight along the flight path to each of the target points; configured to control the aircraft for autopilot at each of the one or more target points to capture the visual dataset of each PV array using a camera of the aircraft; the autopilot implemented by the aircraft includes moving the aircraft along a scanning direction determined with reference to a target viewpoint of the PV array corresponding to each one of the target points from a respective one of the target points.

19. 1. A method for automated flight of an aircraft and automated electroluminescence (EL) imaging of a set of PV arrays using said aircraft, said method comprising: determining a flight path between target points for capturing a visual dataset of the PV arrays, each PV array corresponding to a pair of start and end target points; controlling the aircraft for automated flight along the flight path to a starting target point for each of the PV arrays; controlling the aircraft for autopilot between the respective start and end target points of each PV array to capture the visual data set of the PV array using a camera of the aircraft; Including, The autopilot implemented by the aircraft comprises: aligning a field of view (FOV) of the camera to a PV array subsection of the PV array; positioning a target viewpoint of the PV array corresponding to the starting target point corresponding to the PV array within the aligned FOV; determining a scanning direction for moving the aircraft between the start and end target points corresponding to the PV array with reference to the positioned target viewpoint; capturing the visual data set of the PV array using the camera, starting at the PV array subsection, as the aircraft moves along the scanning direction between the start and end target points; A method comprising:

20. 1. An aircraft for automated flight to perform automated electroluminescence (EL) imaging of a set of PV arrays, the aircraft comprising: a propulsion device for actuating movement of the aircraft; a camera for capturing a visual dataset of the PV array; and a controller communicatively connected to the camera and the propulsion device; Including, The controller: configured to determine a flight path between target points for capturing a visual data set of the PV arrays, each PV array corresponding to a pair of start and end target points; configured to control the aircraft for automated flight along the flight path to a starting target point for each of the PV arrays; configured to control the aircraft for autopilot between the respective start and end target points of each PV array to capture the visual data set of the PV array using a camera of the aircraft; The autopilot implemented by the aircraft comprises: aligning a field of view (FOV) of the camera to a PV array subsection of the PV array; positioning a target viewpoint of the PV array corresponding to the starting target point corresponding to the PV array within the aligned FOV; determining a scanning direction for moving the aircraft between the start and end target points; capturing the visual data set of the PV array using the camera, starting at the PV array subsection, as the aircraft moves along the scanning direction between the start and end target points; Including, aircraft.

Images