Unmanned Aerial Vehicle Off-site Landing System

Abstract

The present invention is entitled "Unmanned Aerial Vehicle Off-Site Landing System". The present invention provides a fixed-wing unmanned aircraft and an operating method thereof. The fixed-wing unmanned aircraft may include, but is not limited to: a fault detection system, the fault detection system being configured to detect a fault in one or more of a plurality of components; a performance evaluation system communicatively coupled to the fault detection system, the performance evaluation system being configured to determine a performance level of the fixed-wing unmanned aerial vehicle based on the fault in the one or more of the plurality of components; and a trajectory generation system communicatively coupled to the fault detection system and the performance evaluation system, the trajectory generation system being configured to generate a landing trajectory of the fixed-wing unmanned aerial vehicle based on the determined performance level of the fixed-wing unmanned aerial vehicle, wherein when the determined performance level is below a predetermined threshold, the landing trajectory includes a stall maneuver, the stall maneuver being configured to minimize the lateral energy of the fixed-wing unmanned aerial vehicle.

Description

Technical Field

[0001] The present disclosure relates generally to aircraft, and more particularly to unmanned aerial vehicles and landing thereof. Background Art

[0002] Unmanned aerial vehicles play an increasing role in cargo transportation, reconnaissance and various other uses. Due to the nature of unmanned aerial vehicles, i.e., there are no passengers on board, unmanned aerial vehicles generally have lower safety standards than manned aircraft. Although lower safety standards are acceptable for unmanned aerial vehicles themselves, there is still the potential for damage to people and property on the ground when an unmanned aerial vehicle malfunctions. Summary of the invention

[0003] In one embodiment, for example, a fixed-wing unmanned aerial vehicle is provided. The fixed-wing unmanned aerial vehicle may include, but is not limited to: a fault detection system configured to detect a fault in one or more of a plurality of components; a performance evaluation system communicatively coupled to the fault detection system, the performance evaluation system configured to determine a performance level of the fixed-wing unmanned aerial vehicle based on the fault in the one or more of the plurality of components; a trajectory generation system communicatively coupled to the fault detection system and the performance evaluation system, the trajectory generation system configured to generate a landing trajectory of the fixed-wing unmanned aerial vehicle based on the determined performance level of the fixed-wing unmanned aerial vehicle, wherein when the determined performance level is below a predetermined threshold, the landing trajectory includes a stall maneuver configured to minimize the lateral energy of the fixed-wing unmanned aerial vehicle.

[0004] In another embodiment, for example, a method of operating a fixed-wing unmanned aerial vehicle having a plurality of components is provided. The method may include, but is not limited to: detecting one or more faults in the plurality of components by a fault detection system; determining a performance level of the fixed-wing unmanned aerial vehicle based on the one or more faults detected by a performance evaluation system; and generating a landing trajectory of the fixed-wing unmanned aerial vehicle by a trajectory generation system, wherein when the determined performance level is below a predetermined threshold, the landing trajectory includes a stall maneuver configured to minimize the lateral energy of the fixed-wing unmanned aerial vehicle.

[0005] In yet another embodiment, for example, a fixed-wing unmanned aerial vehicle having a plurality of components is provided. The fixed-wing unmanned aerial vehicle may include, but is not limited to: a fault detection system configured to detect faults in one or more of the plurality of components, wherein the fault detection system continuously monitors the fixed-wing unmanned aerial vehicle for new faults and when the faults are resolved; a communication system including at least one data communication system and at least one voice communication system; and a processor communicatively coupled to the control system and the fault detection system, the processor configured to determine a performance level of the fixed-wing unmanned aerial vehicle based on the one or more detected faults when the fault detection system detects the one or more faults, wherein the processor is further configured to determine a performance level of the fixed-wing unmanned aerial vehicle based on any new faults received from the fault detection system and from any resolved faults received by the fault detection system continuously update the performance level, and when the performance level of the unmanned aerial vehicle is below a predetermined threshold, determine that an off-site landing is necessary, wherein the processor is further configured to: continuously update the determination that an off-site landing is necessary based on the update to the determined performance level, and cancel the determination that an off-site landing is necessary when the performance level increases above the predetermined threshold; when an off-site landing is necessary, generate a voice warning using the voice communication system, the voice warning including at least one of a pre-recorded message and a voice synthesized message; when an off-site landing is necessary, determine the maximum range of the fixed-wing unmanned aerial vehicle based on the performance level of the unmanned aerial vehicle; based on the performance level of the fixed-wing unmanned aerial vehicle and The maximum range determines whether a predetermined off-site landing site is within the maximum range of the unmanned aerial vehicle, the predetermined off-site landing site including a designated area for off-site landing; based on the determined performance level of the fixed-wing unmanned aerial vehicle, the type of landing site associated with the predetermined off-site landing site, and the type of fault detected, determines a path to the predetermined off-site landing, wherein the path is determined in accordance with: determining, by the processor, when a trajectory that allows the fixed-wing unmanned aerial vehicle to come to a complete stop within a defined area within the predetermined off-site landing site can be constructed based on the performance of the fixed-wing unmanned aerial vehicle, wherein the path is configured to include the trajectory; and when the trajectory cannot be constructed to allow the fixed-wing unmanned aerial vehicle to come to a complete stop within a defined area within the predetermined off-site landing site. When a fixed-wing unmanned aerial vehicle comes to a complete stop within a confined area within a predetermined off-site landing field, determining a trajectory that minimizes the lateral energy of the fixed-wing unmanned aerial vehicle within the predetermined off-site landing field, the trajectory including a pitch that causes the fixed-wing unmanned aerial vehicle to stall as the fixed-wing unmanned aerial vehicle approaches the ground; when the predetermined off-site landing field is within the determined maximum range of the unmanned aerial vehicle, generating a command to the control system to guide the unmanned aerial vehicle to the predetermined off-site landing field using the determined path; and when the predetermined off-site landing field is outside the determined maximum range of the unmanned aerial vehicle, generating a command to the control system to guide the unmanned aerial vehicle away from a populated area. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The specific embodiments will be described below with reference to the following drawings, in which like numerals represent like elements, and in which:

[0007] Figure 1 is a block diagram of an unmanned aerial vehicle according to one embodiment;

[0008] Figure 2 is a flow chart illustrating an exemplary method for operating an off-board landing system according to one embodiment;

[0009] Figure 3 shows an exemplary trajectory for landing at an off-site landing site when the unmanned aerial vehicle is able to land at the off-site landing site while remaining within the boundaries of the site, according to one embodiment;

[0010] Figure 4 shows an exemplary trajectory for minimizing the lateral energy of an unmanned aerial vehicle according to one embodiment; and

[0011] Figure 5 The expression g(H f ) relative to the leveling height H f An exemplary value curve of L1 and L2 is shown, and a manner of obtaining minimum and maximum flare heights based on given values ​​of L1 and L2. DETAILED DESCRIPTION

[0012] The following specific embodiments are merely exemplary in nature and are not intended to limit the invention or the application and use of the invention. As used herein, the word "exemplary" means "used as an example, instance or illustration". Therefore, any embodiment described herein as "exemplary" is not necessarily to be understood as being preferred or advantageous over other embodiments. All embodiments described herein are exemplary embodiments provided to enable those skilled in the art to make or use the invention, without limiting the scope of the invention as defined by the claims. In addition, it is not intended to be bound by any express or implied theory presented in the aforementioned technical field, background technology, summary of the invention or the following specific embodiments.

[0013] Thus, an unmanned aerial vehicle and an off-board landing system are discussed herein. The off-board landing system detects faults in components of the unmanned aerial vehicle and determines how to land the unmanned aerial vehicle based on these faults. Landing may include, for example, maneuvers that minimize the lateral energy of the unmanned aerial vehicle, as discussed in further detail below.

[0014] Figure 11 is a block diagram of an unmanned aerial vehicle (UAV) 100 according to one embodiment. The UAV 100 discussed herein is a fixed-wing unmanned aerial vehicle, which may also be referred to as a fixed-wing drone. However, certain features of the UAV 100 may be generally applied to a rotation-based UAV or manned aircraft. The UAV 100 includes a plurality of components 110, including any combination of an engine system, a flight data system, an inertial reference system, a global positioning system, a power system, a fire detection system, a communication system, a landing system, etc. Depending on the size and purpose of the UAV (e.g., payload delivery, reconnaissance, etc.), the components 110 of the UAV 100 may vary. In one embodiment, for example, the component 110 may include a fuel system 112. As discussed in further detail below, the fuel system may be instructed to discharge any fuel therein to reduce the risk of a fire during an emergency landing.

[0015] When one or more components 110 of the unmanned aerial vehicle experience a failure, an off-landing may be necessary, depending on which component is experiencing the failure and to what extent the failure occurs. An off-landing refers to landing at a location other than a runway. Therefore, the UAV 100 also includes an off-landing system 120. As discussed in further detail below, the off-landing system 120 continuously monitors the failure of the components 110 of the UAV 100, evaluates the performance of the UAV 100, and, if necessary, determines the location of an off-landing and the trajectory of the off-landing.

[0016] The off-board landing system 120 includes one or more processors 130. The one or more processors may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), a physical processing unit (PPU), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microprocessor, or any other logic unit and any combination thereof. The one or more processors 130 may be dedicated to the off-board landing system 120, or may be shared by one or more of the components 110 of the UAV 100. As discussed in further detail below, the off-board landing system 120 includes various systems. The system may include its own one or more processors 130, or may share one or more processors with one or more other systems within the off-board landing system 120 or within the UAV 100.

[0017] The off-board landing system 120 also includes a memory 140. The memory 140 may be any combination of non-volatile memory units and volatile memory units. A portion of the memory 140 may be a cloud-based memory located remotely from the UAV 100. The memory 140 may store a terrain database 142 that may be used by the off-board landing system 120 to determine an off-board landing location, as discussed in further detail below. The memory 140 may also include non-transitory instructions for implementing the off-board landing system 120, as discussed in further detail below.

[0018] The off-board landing system 120 includes a fault detection system 150. The fault detection system 150 continuously monitors the status of the component 110 of the UAV 100. The fault detection system 150 may include components that are dedicated to the fault detection system 150 and / or components that may be shared by one or more other components 110 in the UAV 100. For example, the fault detection system 150 may include a fire detection system, a flap position sensor, an engine system, an electrical system, a flight control system, a navigation system, a communication system, and other components for monitoring the status of other on-board systems and environmental conditions, etc., or any combination thereof. In one embodiment, for example, the component 110 of the UAV 100 may form part of the fault detection system 150 by self-reporting any faults to the off-board landing system 120.

[0019] The off-board landing system 120 also includes a performance evaluation system 160. The performance evaluation system 160 determines a performance level of the UAV based on any one or more faults determined by the fault detection system 150. The performance evaluation system 160 may include one or more processors 130 and memory 140 dedicated to the performance evaluation system 160 or shared with one or more other systems on the UAV 100.

[0020] The performance level of the UAV 100 may define how the off-board landing system 120 responds to a detected fault. Some faults may be small enough to allow the off-board landing system 120 to continue normal operation of the UAV 100 to the destination. Other faults may require an immediate off-board landing. Table 1 lists exemplary components 110 with exemplary faults and corresponding performance levels.

[0021]

[0022] Table 1

[0023] The faults listed in Table 1 are non-exhaustive and may vary between various UAVs 100 depending on the components 110 present on the UAV 100. In addition, the performance level of the UAV 100 in response to certain faults may vary. In other words, different UAVs may respond to the same fault in different ways. For example, a UAV 100 may be equipped with an inertial tracking system that may allow the UAV 100 to continue to a destination for at least a period of time if a global positioning system (GPS) experiences a fault, while a UAV 100 without an inertial tracking system may have to perform an off-site landing if it experiences a GPS fault.

[0024] In this exemplary embodiment, the performance levels are the destination, the nearest landing site, and the nearest off-site landing site. The destination performance level will indicate that the UAV 100 has enough remaining performance to continue to the original destination as planned.

[0025] The nearest landing site performance level indicates that the UAV 100 has enough remaining performance to attempt a normal landing at the nearest landing site. In this case, the nearest landing site is a runway or a dedicated landing site, which includes a sufficiently flat surface of a predetermined length at which the UAV 100 can attempt to land. The landing site can be a runway at an alternate airport (i.e., not the destination airport). The predetermined length can vary depending on the performance of the UAV 100. For example, as shown in Table 1 above, when the braking control system experiences a fault, a longer landing site may be necessary. In order to be considered capable of landing, the UAV 100 should have directional, lateral and longitudinal control, and sufficient data for automatic path control and landing can be obtained. The data may include, for example, positioning, altitude, heading, airspeed, flight path angle, etc.

[0026] The most recent off-site landing site performance level indicates that the UAV 100 does not have the performance to perform normal landing procedures, which triggers an off-site landing, as discussed in further detail below. An off-site landing site may be any site that minimizes collateral damage to personnel or property on the ground.

[0027] In addition to determining the performance level of the UAV 100, the performance evaluation system 160 may determine the overall performance of the UAV 100. Depending on which component 110 of the UAV 100 experiences a failure and to what extent the failure occurs, the overall performance of the UAV 100 may vary. The overall performance of the UAV 100 determined by the performance evaluation system 160 may help determine which landing site or off-site landing site to select and the trajectory (i.e., flight path) to use for landing.

[0028] The off-site landing system 120 also includes a site selection system 170. The site selection system 170 may include one or more processors 130 and a memory 140 dedicated to the site selection system 170 or shared with one or more other systems on the UAV 100. In one embodiment, for example, the memory 140 may store a terrain database 142 indicating the locations of potential landing sites and off-site landing sites. In one embodiment, for example, the terrain database 142 may store all potential landing sites and off-site landing sites along a known route of the UAV 100. This method may be used when the UAV 100 is traveling along a familiar route (e.g., cargo delivery between two locations). In another embodiment, the terrain database 142 may store terrain data, such as elevation data, obstacle data, populated areas, sensitive areas (e.g., oil processing plants), unpopulated areas (e.g., deserts, rivers, oceans), etc. In this embodiment, the site selection system 170 may evaluate the terrain database to determine an on-site or off-site landing site based on the performance of the UAV 100 at the time of the failure and the terrain surrounding the UAV 100. Any combination of site selection methods may be used depending on the typical use case of the UAV 100.

[0029] The performance evaluation system 160 can also determine the maximum range of the UAV 100 based on the detected fault. The maximum range can be calculated based on factors including the type of fault, engine status, remaining onboard fuel, fuel flow, battery status, UAV altitude and speed, wind, etc. A margin can be added to the maximum range to account for inaccuracies and uncertainties. For example, for a complete loss of engine fault, the maximum range can be the maximum parking glide distance (with margin); for a power system fault, the maximum distance is determined by the remaining battery power; for a fuel leak fault, the maximum distance can be calculated by estimating the time remaining before all fuel is exhausted, then multiplying that time by the speed, and then adding it to the aircraft glide performance. When multiple sites are within the maximum range of the UAV 100, the site selection system 170 can select a landing site or an off-site landing site that is closest to the current location (or last known location) of the UAV 100. However, the nearest landing site or off-site landing site may not be the best choice. The site selection system 170 may receive overall performance data from the performance evaluation system 160 to determine a landing site or off-site landing site that matches the performance of the UAV 100. For example, different landing sites may have different lengths, different approach angles, etc. due to terrain or obstacles, etc. Therefore, given the performance of the UAV 100 received from the performance evaluation system 160, the site selection system 170 may select the nearest landing site with a length corresponding to the capable stopping distance of the UAV 100. For example, the performance evaluation system 160 determines that the UAV 100 is still able to perform a landing maneuver, but only off-site landing sites are within range, considering that there will not be many off-site landing sites to choose from in this case, the site selection system 170 may prioritize the off-site landing sites by size, surface type, etc., and select the nearest off-site landing site that can perform the landing maneuver. In one embodiment, for example, even when the UAV 100 is not experiencing a malfunction, the site selection system 170 may continuously determine the nearest landing site or off-site landing site and the trajectory to the site. Thus, in the event of a component failure, the off-board landing system 120 can immediately guide the UAV 100 toward a pre-selected landing site or an off-board landing site with minimal delay.

[0030] The performance of the UAV 100 may also affect whether a trajectory to the selected site can be constructed. Therefore, the off-site landing system 120 also includes a trajectory generation system 180. As discussed in further detail below, the trajectory generation system 180 determines whether a trajectory to the selected site within the performance range of the UAV 100 can be constructed based on data from the performance evaluation system 160. When a trajectory to the selected landing site cannot be constructed, the trajectory generation system 180 requests a new landing site from the site selection system 170. If there is no landing site within the performance range of the UAV 100 (based on the maximum range of the UAV 100 or a trajectory to a landing site within the performance range of the UAV 100 cannot be constructed), the trajectory generation system 180 generates a trajectory toward an off-site landing site that minimizes potential collateral damage, as discussed in further detail below. Based on the performance of the UAV 100, if the UAV 100 cannot perform an off-site landing, the trajectory generation system 180 generates a flight path that guides the UAV 100 toward the least populated area within the maximum range of the UAV 100.

[0031] The off-site landing system also includes a communication system 190. The communication system 190 can utilize any wireless communication protocol. The communication system 190 includes at least one system capable of transmitting audible voice messages. Since the UAV 100 is an unmanned vehicle by definition, the audible voice message may include a pre-recorded audible voice message, a text-to-audio processed voice message (i.e., voice synthesized) or a combination thereof. In the case where the UAV 100 experiences a fault, the processor 130 may cause the communication system 190 to output an audible voice message on a channel that is usually monitored by other aircraft. This audible message allows other pilots of other aircraft in the area to be notified of the fault that the UAV 100 is experiencing and the predicted trajectory of the UAV 100 determined by the trajectory generation system 180, so that the pilots can evaluate whether they need to take action on their own aircraft.

[0032] Figure 22 is a flow chart illustrating an exemplary method 200 for operating an off-site landing system according to one embodiment. At takeoff, the fault detection system 150 begins monitoring any faults of the components 110 of the UAV 100. (Step 202). The fault detection system 150 may actively monitor for faults, passively monitor for faults, or a combination thereof. The fault detection system 150 may actively monitor for faults using various sensors or other detection devices configured to monitor one or more components 110 of the UAV 100. The fault detection system 150 may passively monitor for faults by receiving self-reported faults. In other words, one or more components 110 of the UAV 100 may be configured to self-report faults to the fault detection system 150. When no faults are detected, the fault detection system 150 continues to monitor for faults, and the UAV 100 continues its current mission.

[0033] When the fault detection system 150 detects a fault, a report is generated by the processor 130 and transmitted via the communication system 190. (Step 204). The report may include a data-based report, an audible voice report, or a combination thereof. The data report may be transmitted to the operator of the UAV 100 and air traffic control. The data report may include, for example, a flight identifier associated with the UAV 100 and any available data about the fault. The voice report may include one or more of a pre-recorded voice message and a text-to-audio voice message that provides any available data about the fault through a voice channel that is typically monitored by the aircraft. As described above, by providing a voice message, the UAV 100 may notify other pilots that may be in the fault area, thereby allowing other pilots to operate their aircraft to avoid the UAV 100 when necessary.

[0034] The processor 130 and / or the component 110 itself may then attempt to recover from the fault. (Step 206). Certain components 110 may have recovery procedures that may be initiated when a fault is detected. The recovery procedures may vary depending on the component 110 and the type of fault that has occurred. For example, an engine restart procedure may be initiated to recover from an engine fault; a fire extinguishing system may be initiated for a detected fire; a reset of a power switch may be initiated for a power system fault. When the fault is fully recoverable, the processor 130 generates a report and the UAV may continue to the original destination as planned. (Step 208). The report may be data-based, voice-based, or a combination thereof, and contain information about the fault recovery.

[0035] When the fault is only partially recoverable or unrecoverable, the performance evaluation system 160 determines the performance level and maximum range of the UAV 100. (Step 210). The performance level of the UAV 100 is based on the component 110 that failed, the extent to which the component failed (e.g., completely or partially), and the presence of any other component 110 that can serve as a backup for the failed component 110. In one embodiment, for example, a lookup table can be stored in the memory 140, which associates each potential fault with a performance level. In one embodiment, for example, the performance level can be a destination, a landing site, an off-site landing, and a fly-off. However, the number of performance levels and their corresponding definitions may be different. For example, in one embodiment, the destination performance level may require a minimum set of control surfaces to meet the directional, lateral, and longitudinal maneuverability required for a safe landing. However, some faults may include cascading faults that reduce the performance level of the UAV 100. In other words, some faults of the component 110 may cause other components to have less than all functions. For example, a complete loss of the GPS system would not directly affect the operability of the engines or flaps, however, a complete loss of the GPS system may cause the UAV 100 to lose the ability to navigate, and therefore lose the ability to land at the original destination. Table 1 above lists a number of failures along with corresponding performance levels. However, as described above, failures of components 110 of UAV 100 and corresponding performance levels associated therewith may vary between UAVs 100, depending on the components 110 of the respective UAV 100.

[0036] The lookup table may further associate the remaining performance of the UAV 100 with the corresponding fault as performance data. The performance data may define, for example, which maneuvers and operations the UAV 100 is capable of performing, which components 110 are operable, and the degree to which the components 110 are operable. For example, a failure of one component 110 may completely or partially disable another component 110 that may not have experienced the failure. As discussed in further detail below, the performance data may be used when generating a trajectory of the UAV 100.

[0037] The performance evaluation system 160 determines the maximum range of the UAV 100 based on the detected fault and / or the performance data. In one embodiment, a lookup table may associate the detected fault with the performance data and with a method for calculating the maximum range given the fault and current altitude of the UAV 100 and any other relevant factors. For example, when the fault is the loss of all engines, the maximum range may be based on the maximum stop glide distance of the UAV 100; for a power system fault, the maximum distance is determined by the remaining battery charge; for a fuel leak fault, the maximum distance may be calculated by estimating the time remaining before all fuel is exhausted. The determined range is then multiplied by the speed factor of the UAV and then added to the glide performance of the UAV 100.

[0038] In one embodiment, for example, the performance evaluation system 160 may not wait for the recovery procedure to complete before beginning to evaluate the performance level of the UAV 100. As discussed in further detail below, the off-board landing system continuously monitors the recovery and updates the flight plan of the UAV 100 as the UAV 100 recovers from a failure or experiences more failures.

[0039] When the performance evaluation system 160 determines that the performance level is the original destination (step 212), the processor 130 generates a report with any updated information and continues to the destination as planned. (step 208). The report may include a data report, a voice report, or any combination thereof, and may include one or more of any information about the fault, trajectory, etc. of the UAV 100. The process then returns to step 202, and the fault detection system 150 continues to monitor for any new faults.

[0040] When the performance evaluation system 160 determines that the performance level is landing (step 214), the site selection system 170 determines whether the landing site is available and selects the landing site for evaluation. (Step 216). If the landing site is within the maximum range of the UAV 100 and within certain performance of the UAV 100, the landing site can be selected for evaluation. For example, the site selection system 170 can consider the length of the landing site, landing performance, weather conditions, traffic information, ground equipment, etc. For example, if the nearest landing site within the range of the UAV 100 is a runway at an airport, but the UAV 100 cannot land normally, the site selection system 170 may not select the airport to avoid interfering with the operation of the airport.

[0041] When there is an available landing site for evaluation, the trajectory generation system 180 attempts to build a trajectory to the selected landing site based on the performance of the UAV 100 and one or more detected faults. (Step 218). In one embodiment, for example, the trajectory generation system 180 includes a flight management system (FMS), or otherwise collaborates with the FMS to build a trajectory. The trajectory includes a flight path to the landing site and a landing path for landing. The trajectory generation system 180 adds additional variables to the trajectory based on the faults and performance of the UAV 100. For example, if the UAV 100 is on fire, but its performance is not currently affected, the trajectory generation system 180 can generate a trajectory with a steep descent path at a speed higher than normal to suppress the fire and land as quickly as possible. As another example, the trajectory generation system 180 generates a trajectory from the current position to intercept a predefined approach and landing path to the landing site, which predefined path can be free from terrain and traffic constraints.

[0042] When the trajectory generation system 180 is unable to construct a trajectory to the selected site or the constructed trajectory is longer than the maximum range that the UAV 100 can achieve, the process returns to step 216 and the site selection system 170 determines whether another landing site is available. (Step 220). For example, a trajectory to the selected site within the maximum range may not be constructed when terrain clearance is not feasible or the path generated due to turns or terrain avoidance is longer than the maximum range.

[0043] When the trajectory generation system 180 is able to construct a trajectory to the selected site (step 220), the processor 130 generates and transmits an updated report via the communication system 190, and proceeds along the trajectory to the selected landing site. (step 222). As described above, the report may include a voice-generated report to inform pilots of other aircraft in the area about the UAV 100 and the trajectory.

[0044] The processor then continues to monitor whether the recovery procedure is successfully completed. (Step 224). As described above, the off-site landing system 120 may not wait for the recovery procedure to complete before starting the process of changing the route of the UAV 100. Some recovery procedures may take a long time to complete. Other recovery procedures may not succeed on the first attempt. Therefore, by continuously monitoring the recovery, when a failure is detected, the off-site landing system 120 provides the UAV 100 with the best possible opportunity to recover and perform a normal landing. If it is determined that the recovery procedure is successful, the process returns to step 210 to re-determine the performance of the UAV 100. Depending on the failure, the degree of recovery, and the newly determined performance of the UAV 100, the performance level of the UAV 100 can be upgraded, or the UAV 100 can be returned to the destination performance level, or the off-site landing or lower state can be upgraded to the landing site performance level, thereby reducing the possibility of damage to the UAV 100 and any collateral damage to other property.

[0045] When the recovery procedure has not been successful, the fault detection system 150 continues to monitor for any new faults. (Step 226). Certain faults may cause new faults to occur. For example, an ongoing fire onboard the UAV 100 may disable a previously fully operational component 110. When a new fault is detected, the process returns to step 204 where the new fault is reported, followed by the initiation of the recovery procedure and the determination of a new capability level of steps 206 and 210. When no new faults have occurred, the process returns to step 224 where the processor 224 continues to actively initiate the recovery procedure and monitor its success.

[0046] When no landing site is available (from step 216), or when the performance level is determined to be off-site landing or lower, the site selection system 170 determines whether an off-site landing location is available. (Step 228). The site selection system 170 may determine that an off-site landing location is available when the off-site landing location is within the maximum range of the UAV 100 and within the performance of the UAV 100.

[0047] When there are no off-site landing sites within the maximum range, when there are off-site landing sites within the maximum range but within the performance of the UAV 100, or when the UAV 100 is unable to perform an off-site landing based on the performance level, the processor 130 of the off-site landing system 120 generates a command to fly the UAV 100 away from a populated or sensitive area and generates a report if possible. (Step 230). When the UAV 100 is unable to perform the maneuver for an off-site landing, the performance level of the UAV 100 may be less than the off-site landing performance. For example, if the UAV 100 loses all flight control, the off-site landing system 120 can generate a variable thrust command to maneuver away from densely populated or sensitive areas; if the UAV 100 is completely stuck on the pitch axis, the off-site landing system 120 can generate a sharp direction command to avoid densely populated areas before the UAV 100 experiences a complete loss of control; the UAV 100 loses its position, the UAV 100 can maintain its heading and wait for a defined period of time to see if the position can be recovered, if not recoverable, the off-site landing system 120 can generate a command to maintain the heading or track to fly to a vast uninhabited area such as a desert or ocean. As described above, the report can be a data report, a voice report, or a combination thereof. The memory 140 can store the position along the route of the UAV 100, where the UAV 100 can aim at a sparsely populated or unpopulated area. Then, the process proceeds to step 224 to determine whether the UAV 100 can recover from the failure.

[0048] When an off-site landing site is available, the trajectory generation system 180 attempts to establish a trajectory to the off-site landing site. (Step 232). The trajectory generated by the trajectory generation system 180 is based on the performance of the UAV 100 and data corresponding to the off-site landing site. The data of the off-site landing site includes the terrain of the off-site landing site, the terrain around the off-site landing site, the size of the off-site landing site, and the type of the off-site landing site. The terrain of the site itself and the surrounding area may include both man-made objects (e.g., buildings, power lines, etc.) and natural objects (e.g., mountains, hills, trees, etc.). The terrain data is used to generate a trajectory that attempts to avoid both man-made and natural obstacles that may prevent the UAV 100 from landing within the off-site landing site.

[0049] The size of the off-site landing field includes the dimensions of the off-site landing field. The trajectory generation system 180 can use the dimensions of the off-site landing field to determine the length of the off-site landing field in the approach direction. The length is used to ensure that the UAV 100 can land and stop within the off-site landing field to minimize any collateral damage to areas outside the off-site landing field.

[0050] The trajectory generated by the trajectory generation system 180 may vary depending on the terrain data, the size of the off-site landing site, the type of off-site landing site, and the performance of the UAV. For example, when the UAV 100 is experiencing degraded control (such as loss of pitch control), the trajectory generation system 180 may generate a trajectory that uses the engine to adjust the speed and remain on the generated flight path. As another example, if the UAV 100 has lost all altitude and / or height data, the trajectory generation system 180 may generate a horizontal trajectory until it is within the area of ​​the off-site landing site and then performs a circular descent until landing. Another example is that if the off-site landing site is a river, the trajectory generation system 180 may generate a water landing trajectory with the landing gear retracted.

[0051] In many cases, the ideal trajectory includes a maneuver that minimizes the lateral energy of the UAV 100. In a typical landing situation, the aircraft lands with minimal vertical energy, making the landing relatively gentle to make the passengers feel comfortable and avoid damaging the aircraft. Therefore, a typical landing procedure for a fixed-wing aircraft includes a large lateral energy. In the case where the landing needs to be interrupted due to congestion on the runway, for example, a large lateral energy is maintained. However, when the UAV 100 is guided to an off-site landing site, the UAV 100 either does not have the performance to perform a traditional landing, or may not be able to reach a suitable landing site. In this way, the priority of the off-site landing system 120 is not a gentle landing, but a reduction in the risk to people and property on the ground. Therefore, the maneuver that minimizes the lateral energy of the UAV 100 is not necessarily designed to reduce the payload of the UAV 100 or the damage to the UAV 100 itself, but by reducing the area that the UAV 100 may hit when landing off-site, the impact area of ​​the UAV 100 when landing on the off-site landing site is minimized. However, the trajectory generation system 180 may first evaluate whether a trajectory can be generated that minimizes the vertical descent speed while bringing the UAV 100 to a complete stop within the off-site landing site before maneuvering to minimize the lateral energy of the UAV 100.

[0052] Figure 3 An exemplary trajectory for landing at an off-site landing site is shown when the UAV 100 is able to land at the off-site landing site while remaining within the boundaries of the site. Figure 3As shown, the trajectory includes a flare maneuver designed to reduce damage to the UAV 100 while still allowing the UAV 100 to come to a complete stop within the field. For a normal autoland performed at a landing field (i.e., a runway), the length available for landing is fixed, the approach flight path angle and the final approach speed are fixed, and typically the flare trajectory is a fixed exponential curve that reduces the vertical speed to a target landing vertical speed (e.g., starting at 50 feet above the runway threshold). As discussed in further detail below, when landing at an off-site landing field, the flight path angle, the final approach speed are variable, and therefore the flare trajectory is variable to ensure that the UAV can come to a stop within the off-site landing field at a minimum vertical speed.

[0053] As described above, depending on the size of the off-site landing site, the terrain of the off-site landing site, and the performance of the UAV 100, such as Figure 3 The landing depicted in the video is not always possible. Figure 4 An exemplary trajectory for minimizing the lateral energy of UAV 100 is shown. Figure 4 As shown, the trajectory includes a flare maneuver designed to stall the UAV 100, thereby ensuring that the UAV 100 stops within the confines of the off-site landing site with minimal lateral energy. In one embodiment, for example, the processor 130 can generate instructions to bleed fuel from the fuel system 112 before performing the stall maneuver to reduce the chance of a fire during landing.

[0054] The trajectory generation system 180 may first try to Figure 3 An ideal trajectory is constructed that lands the UAV 100 within the off-site landing site at an acceptable descent rate while achieving a complete stop within the off-site landing site. The trajectory determined by the trajectory generation system includes, for example, the leveling height H f and trajectory time constant τ.

[0055] The height of the ideal flattened trajectory is given by:

[0056] h(t)=H f ×e -t / τ

[0057] (Formula 1)

[0058] where h(t) is the height above ground level at the off-site landing site as a function of time t, with t being the value from Figure 3 The flare trajectory shown begins at the time it begins and ends when the UAV 100 is expected to touch the ground, H f is the altitude at which the flare maneuver begins, and τ is a time constant, which will be discussed in further detail below.

[0059] Vertical velocity V of ideal trajectory zis the derivative of the height h(t) and is calculated according to the following formula:

[0060]

[0061] According to formulas (1) and (2), the vertical velocity V can be derived. z The formula is:

[0062]

[0063]

[0064] The target landing vertical speed V of the ideal trajectory ztp It can be determined by the following formula:

[0065]

[0066] Where htp is a constant of landing height, which can be set to 0<htp<H f For example, in one embodiment, when htp is set to 1 meter, the actual leveling height may be H f -1 to ensure a satisfactory landing.

[0067] Assume that UAV 100 begins to level off with an airspeed of V0 and a flight path angle γ0 of an ideal trajectory. The vertical velocity at the start of the flare is V z0 =V0×sin(γ0). From formula (3), the time constant τ can be derived as:

[0068]

[0069] Therefore, the trajectory generation system 180 can be based on equations (4) and (5) by increasing H f , reduce V0 or reduce γ0 to reduce the vertical velocity V of the ideal trajectory ztp However, these parameters cannot be adjusted arbitrarily, because the landing distance X is td Affected by them:

[0070]

[0071] Since UAV 100 is expected to land at an off-site landing site, X td Subject to the following restrictions: X min ≤X td ≤X max .X min is a predetermined point after which the UAV 100 must land to ensure that the UAV 100 does not land outside of the collision zone. min Can be based on OK. Xmax is the calculated point before which the UAV 100 must land to ensure that the UAV 100 can come to a complete stop within the collision zone. OK X max In these formulas, L1 is X a and X min , Xa is the aiming point (i.e., the point at which the UAV 100 is pointing before the flare maneuver begins), and L2 is X a and X max The difference between (V x0 , L), where L is the length of the collision station. The total braking distance (TBD) of the site can be determined by TBD = L-L1-L2.

[0072] Therefore, the trajectory generation system 180 attempts to find H that satisfies the following formula f Values:

[0073]

[0074] If L2<-L1, then there is no H that satisfies all three of the formulas of Formula 7. f , V0, and γ0. When L2 < -L1, the required braking distance is too long to achieve a complete stop in the collision zone. Therefore, in these cases, the trajectory generation system 180 generates a new trajectory that minimizes the lateral energy, such as Figure 4 As shown, and as discussed in further detail below, L2=h(V0, γ0, L) is a monotonically decreasing function of V0, which corresponds to the situation that the larger the initial V0, the longer the required braking distance.

[0075] In order to determine H that satisfies Formula 7 f , the trajectory generation system can determine H according to the following formula f f(H f ) function:

[0076]

[0077] Depending on the performance of the UAV 100, the trajectory generation system 180 determines H in different ways. f At the lateral velocity V x is one of the controlled variables during leveling and is controlled to V x (t)≡V x0 =V0×cos(γ0), then:

[0078]

[0079] in And 0<htp<H f, and g(Hf) is the normal landing trajectory. and Greater than zero, g(H f ) is a monotonically increasing function, which can be expressed as Figure 5 Draw as shown. Figure 5 Shows the expression Relative to H f An exemplary value curve of and a method for obtaining the minimum and maximum leveling heights based on L1 and L2. In one embodiment, for example, the trajectory generation system 180 may use a mapping method to determine the minimum leveling height H f_gmin and maximum leveling height H f_gmax In other words, the trajectory generation system 180 plots g(H f ) to determine H f_gmin and H f_gmax .

[0080] The trajectory generation system 180 is intended to generate a trajectory that lands the UAV 100 as close to Xmin as possible within the off-site landing site (i.e., the point after which the UAV 100 must land to ensure that the UAV 100 does not land outside the landing site), wherein the acceptable descent rate is no greater than V ztp_max In other words, as seen in the following cases, the trajectory generation system 180 first attempts to generate a trajectory with a value no greater than V ztp_max The UAV 100 is brought down at a descent rate of 100 to minimize damage to the UAV 100. However, when a trajectory is not available, the trajectory generation system 180 generates a trajectory such as Figure 4 The trajectory shown is used to minimize the lateral energy of UAV 100.

[0081] In the event that a failure of component 110 of the UAV results in an inability to control airspeed V0 while maintaining the desired flight path angle, trajectory generation system 180 may determine the flare altitude H according to the following equation: f :

[0082] Step 1: Pass Get H f_gmin .

[0083] if Among them, H c is the current altitude of the aircraft, go to step 6, otherwise go to step 2.

[0084] Step 2: Calculate L2=h(V0, γ0, L). If L2<-L1, go to step 6, otherwise execute steps 3 to 5.

[0085] Step 3: Pass Get H f_gmax

[0086] Step 4: Calculate H by the following formula f_smmin To meet the drop rate limit:

[0087]

[0088] Step 5: If H c <H f_smin , go to step 6,

[0089] Otherwise continue:

[0090] If H f_smin ∈[H f_gmin , H f_gmax ], then H f =H f_smin -htp. In this case, the UAV 100 descends at a rate Land in the area and achieve a complete stop within the off-site landing area.

[0091] End step.

[0092] Otherwise, if H f_smin <H f_gmin , then H f =H f_gmin -htp. In this case, the UAV 100 descends at a rate Land on xmin and come to a complete stop within the off-site landing area.

[0093] End step.

[0094] Otherwise, if H f_smin >H f_gmax , go to step 6.

[0095] Step 6: The trajectory generation system 180 generates instructions to make the UAV 100 level off at Hf1 to stall, such as Figure 4 In this case, the UAV came to a complete stop within the off-site landing field.

[0096] End step.

[0097] In the case where the UAV 100 is able to control itself to satisfy the velocity constraint V0 and the flight path angle γ0 before initiating the flare, V0 and H f Determined by the following steps:

[0098] Step 1: Pass Get H f_gmin .

[0099] if Go to step 4, otherwise perform steps 2 to 3.

[0100] Step 2: Calculation

[0101] Calculate V 0_max_L2 =h -1 (-L1, L, γ0);

[0102] Get V 0_max =min(V 0_max_sink_rate , V 0_max_L2 ) and V 0_min =V stall .

[0103] Step 3: Select Then H f_gmin -htp. In this case, the UAV 100 descends at a rate Land at Xmin and come to a complete stop in the off-site landing area. End the procedure.

[0104] Step 4: The trajectory generation system 180 generates instructions to make the UAV 100 level off at Hfl to stall, such as Figure 4 In this case, the UAV came to a complete stop within the off-site landing field.

[0105] End step.

[0106] Assume that due to the performance of UAV 100, V x is not a controlled variable during the flare maneuver and 0 < V x (t)<V x0 =V0×cos(γ0). Therefore, in this case, the trajectory generation system 180 will modify the above formula 8 as follows:

[0107]

[0108] Therefore, in this case, when And g(H f )≤L2, then -L i ≤f(H f )≤L2. l(H f ) is a monotonically decreasing function. Therefore, the trajectory generation system 180 can obtain Therefore, when When V x is unknown, but it can be assumed that f(H f ), which allows the trajectory generation system 180 to generate a trajectory that causes the UAV 100 to land closer to Xmin at a lower level-off altitude.

[0109] When the airspeed V0 is uncontrollable while maintaining the required flight path angle, level off the altitude H f Determine by following these steps:

[0110] Step 1: Calculate L2=h(V0, γ0, L). If L2<-L1, go to step 5, otherwise execute steps 2 to 4.

[0111] Step 2: Pass Get H f_gmax ;

[0112] Step 3: Calculate H by the following formula f_smin To meet the drop rate limit:

[0113]

[0114] Step 4: If H c <H f_smin , go to step 5,

[0115] Otherwise continue:

[0116] If H f_smin ≤min[H f_lmax , H f_gmax ], then H f =H f_smin -htp. In this case, the UAV descends at a descent rate Land and come to a complete stop within the off-site landing area.

[0117] End step.

[0118] Otherwise, if H f_smin >min[H f_lmax , H f_gmax ], go to step 5.

[0119] Step 5: The trajectory generation system 180 generates instructions to make the UAV 100 level off at Hfl to stall, such as Figure 4 In this case, the UAV comes to a complete stop within the off-site landing field. End step.

[0120] In the case that the UAV 100 is able to control itself to satisfy the velocity constraint V0 and the flight path angle γ0 before initiating the flare, when V0 is selected, the trajectory generation system 180 considers V0, L2, and V 0_max_sink_rate The relationship between:

[0121]

[0122] Once V0 is selected, its corresponding boundary V 0_max_sink_rate It is also determined by the trajectory generation system 180. In order to meet the descent rate requirement, the following conditions should be met:

[0123] V 0_max_sink_rate -V0≥0

[0124] So that: m(V0) = V 0_max_sink_rate -V0

[0125] get:

[0126]

[0127] Since from

[0058] /

[0056] and

[0128] From

[0060]

[0129] therefore,

[0130] Therefore, when m(V0)=0, the trajectory generation system 180 can obtain V 0_max_L2 Through the above analysis, the trajectory generation system 180 can determine V0 and H in this case through the following steps: f :

[0131] Step 1: Pass Get V 0_max_L2 ;

[0132] calculate

[0133] Get V 0_max =min(V 0_lmax_sink_rate , V 0_max_L2 ) and V 0_min =V stall .

[0134] Step 2: Select Then In this case, the UAV 100 descends at a rate V ztp =V ztp_max Land at an off-site landing area and come to a complete stop at the off-site landing area.

[0135] End step.

[0136] The above trajectory calculations are exemplary only and represent possible trajectory calculations based on the assumption that certain faults exist in UAV 100. Different faults that result in different performance may require different trajectories, such as Figure 3 and Figure 4Landing or stalling at an off-site landing field as indicated.

[0137] refer to Figure 2 If the trajectory generation system 180 is unable to create a trajectory for one of the two landing maneuvers, the processor 130 returns to step 228 to determine whether another off-site landing site is available. (Step 234). When the trajectory generation system 180 is able to generate a trajectory, the processor 130 instructs the UAV 100 to proceed along the trajectory via a control signal and report the trajectory using the communication system. (Step 236). As described above, the report may include a data report and / or a voice-based report to inform other pilots of aircraft in the area about the trajectory of the UAV 100. The processor 130 then proceeds to step 224 to determine whether the UAV 100 has recovered from the failure.

[0138] Thus, the off-site landing system 120 of the UAV 100 is capable of effectively landing the UAV 100 on a landing site or even an off-site landing site during certain failures, while also generating a trajectory that minimizes collateral damage to ground elements when a failure of the UAV 100 reduces the UAV's ability to perform a landing.

[0139] Although at least one exemplary embodiment has been presented in the aforementioned specific embodiments of the present invention, it should be understood that there are a large number of variations. It should also be understood that an exemplary embodiment or multiple exemplary embodiments are only examples and are not intended to limit the scope, applicability or configuration of the present invention in any way. On the contrary, the aforementioned specific embodiments will provide a convenient roadmap for implementing the exemplary embodiments of the present invention for those skilled in the art. It should be understood that, without departing from the scope of the present invention as set forth in the appended claims, various changes may be made to the functions and arrangements of the elements described in the exemplary embodiments.

Claims

1. A fixed-wing unmanned aerial vehicle having multiple components, comprising: a fault detection system configured to detect a fault in one or more of the plurality of components; a performance evaluation system communicatively coupled to the fault detection system, the performance evaluation system configured to determine a performance level of the fixed-wing unmanned aerial vehicle based on the fault in the one or more of the plurality of components; and a trajectory generation system communicatively coupled to the fault detection system and the performance evaluation system, the trajectory generation system configured to generate a landing trajectory for the fixed-wing unmanned aerial vehicle based on the determined performance level of the fixed-wing unmanned aerial vehicle, wherein when the determined performance level is below a predetermined threshold, the landing trajectory includes a stall maneuver configured to minimize lateral energy of the fixed-wing unmanned aerial vehicle.

2. The fixed-wing unmanned aerial vehicle according to claim 1, further comprising: a communication system communicatively coupled to the fault detection system, the performance evaluation system, and the trajectory generation system, the communication system configured to generate and transmit a voice report including at least one of a pre-recorded message and a speech synthesized message based on the detected fault, the determined performance level, and the generated landing trajectory.

3. The fixed-wing unmanned aerial vehicle of claim 1 , wherein the trajectory generation system is further configured to determine when a landing trajectory can be generated according to the performance level of the fixed-wing unmanned aerial vehicle, the landing trajectory comprising a trajectory that causes the fixed-wing unmanned aerial vehicle to land in an off-site landing field and causes the fixed-wing unmanned aerial vehicle to completely stop in the off-site landing field, and the trajectory generation system is configured to generate the landing trajectory including the stall maneuver when the landing trajectory cannot be generated.

4. The fixed-wing unmanned aerial vehicle according to claim 1, wherein: The fault detection system is further configured to continuously monitor for new faults and recovery from faults; The performance evaluation system is further configured to continuously update the performance level of the fixed-wing unmanned aerial vehicle based on any new faults monitored by the fault detection system and any recoveries from faults; and The trajectory generation system is further configured to generate an updated trajectory for the fixed-wing unmanned aerial vehicle based on the updated performance level. 5 . The fixed-wing unmanned aerial vehicle of claim 1 , wherein the plurality of components includes a fuel system, wherein the fuel system is configured to dump fuel prior to the stall maneuver of the landing trajectory. 6 . The fixed-wing unmanned aerial vehicle of claim 1 , wherein the performance evaluation system is further configured to determine a maximum range of the fixed-wing unmanned aerial vehicle based on the detected fault.

7. The fixed-wing unmanned aerial vehicle of claim 1 , further comprising a site selection system communicatively coupled to the performance evaluation system, the site selection system configured to select a potential off-site landing site based on the determined maximum range of the fixed-wing unmanned aerial vehicle.

8. A method of operating a fixed-wing unmanned aerial vehicle having a plurality of components, the method comprising: detecting, by a fault detection system, one or more faults in the plurality of components; determining, by a performance evaluation system, a performance level of the fixed-wing unmanned aerial vehicle based on the detected one or more faults; as well as A landing trajectory for the fixed-wing unmanned aerial vehicle is generated by a trajectory generation system, wherein when the determined performance level is below a predetermined threshold, the landing trajectory includes a stall maneuver configured to minimize lateral energy of the fixed-wing unmanned aerial vehicle.

9. The method according to claim 8, further comprising: A voice report is generated and transmitted by a communication system communicatively coupled to the fault detection system, the performance evaluation system, and the trajectory generation system, the voice report including at least one of a pre-recorded message and a speech synthesized message based on the detected fault, the determined performance level, and the generated landing trajectory.

10. The method of claim 8, further comprising determining, by the trajectory generation system, when a landing trajectory can be generated according to the performance level of the fixed-wing unmanned aerial vehicle, the landing trajectory comprising a trajectory for landing the fixed-wing unmanned aerial vehicle in an off-site landing field and bringing the fixed-wing unmanned aerial vehicle to a complete stop in the off-site landing field, the trajectory generation system being configured to generate the landing trajectory including the stall maneuver when the landing trajectory cannot be generated.

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