CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. Provisional Patent Application No. 63/131112 filed on 28 December 2020 entitled METHODS AND SYSTEMS FOR MANEUVERING A ROTORCRAFT TO AVOID AIR TRAFFIC, which is hereby incorporated by reference.

BACKGROUND

[0002] The present application relates generally to unmanned aircraft, particularly rotorcraft, and more specifically to methods and systems for maneuvering a rotorcraft to avoid oncoming air traffic.

[0003] A critical component of safely integrating unmanned aircraft into the public airspace system is the ability to reliably and safely execute an avoidance maneuver to assure safe separation from other aircraft at all times. This problem is particularly challenging when attempting to optimize for slow-moving rotorcraft, e.g., a quadcopter, operating near fast moving general aviation aircraft. In such a scenario, the safest maneuver is for the rotorcraft to descend as quickly as possible to the ground or near the ground where other aircraft are least likely to navigate. The inherent aerodynamics of rotorcraft limit the vertical descent to a sub-optimal speed. Various embodiments disclosed herein relate to methods and systems for dramatically increasing that vertical descent speed, while still maintaining safe and stable flight characteristics.

BRIEF SUMMARY OF THE DISCLOSURE

[0004] A method in accordance with one or more embodiments is provided for calculating and executing an optimized avoidance maneuver by a rotorcraft in the presence of oncoming air traffic. The method includes the steps of: (a) acquiring information about a threat aircraft; (b) calculating an avoidance maneuver to avoid potential collision with the threat aircraft, wherein the avoidance maneuver comprises a travel path avoiding prop wash from the rotorcraft; and (c) executing the avoidance maneuver by the rotorcraft.

[0005] A rotorcraft in accordance with one or more embodiments comprises a power supply for powering the rotorcraft, a set of rotors driven by one or more motors, a communications module; and a control system configured to maneuver the rotorcraft by controlling operation of the rotors. The control system is also configured to: (a) acquire information about a threat aircraft; and (b) execute a calculated avoidance maneuver to avoid potential collision with the threat aircraft, wherein the avoidance maneuver comprises a travel path avoiding prop wash from the rotorcraft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 illustrates a straight down descent and an angled descent by a rotorcraft.

[0007] FIGS. 2A and 2B illustrate the effects a rotorcraft traveling directly into the turbulent air created by the propellers of the rotorcraft and traveling at an angle to the turbulent air, respectively.

[0008] FIGS. SA and SB FIG. 3A illustrate preferred directions of travel of the rotorcraft when only the current position of the threat aircraft is known, and when the velocity and/or trajectory of the threat aircraft are also known, respectively.

[0009] FIG. 4 is a simplified block diagram showing select components of a representative rotorcraft in accordance with one or more embodiments.

[0010] FIG. 5 is a flow chart illustrating an exemplary process of calculating and executing an optimized avoidance maneuver by a rotorcraft in accordance with one or more embodiments. [0011] Like or identical reference numbers are used to identify common or similar elements.

DETAILED DESCRIPTION

[0012] Various embodiments disclosed herein relate to methods and systems for calculating and executing an optimized avoidance maneuver to be performed by a rotorcraft in the presence of oncoming air traffic. As depicted in FIG. 5, an exemplary method in accordance with one or more embodiments includes the steps of: (a) acquiring information about a threat aircraft (step 40); (b) calculating the avoidance maneuver (step 42); and (c) executing the avoidance maneuver by the rotorcraft (step 44). The avoidance maneuver is performed to yield right of way to the oncoming threat aircraft as quickly and safely as possible.

Acquiring Threat Information

[0013] There are many ways to acquire information about an oncoming threat aircraft. Examples include utilizing an online ADS-b (Automatic Dependent Surveillance- Broadcast) or similar aircraft tracking service, having an integrated ADS-b or similar aircraft tracking receiver built into the system, using an onboard or ground-based sensor such as RADAR, artificial vision-based or acoustic-based sensors, or having a human on site observing the airspace.

[0014] Once an aircraft is identified as a threat by one of these (or similar) methods, the system is notified through a software interface. The notified system can be software on the rotorcraft itself, software on a ground-based sensor or system that can communicate with the rotorcraft through a wireless or wired link, or a human pilot who can communicate with the rotorcraft through a wireless or wired link. (A wired link could be used in a tethered system.) Calculating the Descent Maneuver

[0015] FIG. 1 illustrates two descent options for a rotorcraft 10. Arrow 12 depicts a straight down descent, and arrow 14 depicts an angled descent.

[0016] An ideal descent maneuver will get the rotorcraft to the ground or out of the zone conflicting with the threat aircraft as quickly as possible. Normally, the fastest way to get between two points is by traveling in a straight line. However, a rotorcraft is limited by how quickly it can descend straight down due to the effects of flying directly into its own prop wash, which is the turbulent, disturbed mass of air pushed by a propeller. As illustrated in FIG. 2A, when the rotorcraft 10 travels straight down, it is constantly traveling directly into the turbulent air created by the propellers of the rotorcraft itself.

[0017] In order to descend more quickly, a unique maneuver can be carried out such that the rotorcraft travels in a downward direction with some horizontal component. This horizontal component allows for the rotorcraft to avoid flying into its own turbulent prop wash and results in a safe descent speed which is much faster than if the vehicle were to descend straight down. As shown in FIG. 2B, when the rotorcraft 10 travels diagonally down with some horizontal motion, it does not travel into the turbulent air and therefore can travel at a much higher vertical speed while maintaining stable and safe control.

[0018] In one or more embodiments, a descent angle can be chosen such that the vehicle 10 can reach the ground at least three times faster than if the vehicle 10 descended straight down. In testing, the maximum safe descent speed for a vehicle executing a straight-down maneuver was 1.6 - 1.9 m/s depending on ambient conditions such as wind speed, temperature, and air pressure. When executing the diagonal maneuver, the maximum vertical descent speed was 5.0 - 7.5 m/s depending on the ambient conditions. Experimental data shows that using a horizontal velocity of approximately twice the vertical velocity yields a result of a well-controlled descent. This may vary with different flight vehicles. [0019] The exact flight profile of the descent maneuver can take many forms. The simplest is descending in a straight diagonal line with some fixed vertical and horizontal speed. Additional possible flight profiles include but are not limited to a downward spiral pattern, multiple straight line segments that connect at different angles, or a zig-zag pattern. These more complex flight profiles have the added benefit of minimizing overall horizontal travel by the vehicle 10 in scenarios where the operational area is limited.

[0020] Given that the vehicle 10 is descending with some horizontal component to its motion, the direction in which the vehicle 10 should travel is of importance. In the case where the vehicle 10 descends in a straight diagonal line, the heading in which to apply this horizontal motion can be optimized to further reduce the risk of aircraft collision. If only a single location is known of the threat aircraft, then the descent heading should be chosen to point away from the aircraft. If more information is known about the velocity and flight path of the threat aircraft, then the heading should be chosen to be perpendicular to the flight path such that it maximizes the distance between the rotorcraft and point of closest approach of the trajectory of the threat aircraft. FIG. BA shows that when only the current position of the threat aircraft 20 is known, the vehicle 10 preferably simply moves away from the threat. FIG. 3B shows that when the velocity and/or trajectory of the threat aircraft 20 are also known, a more optimal heading can be chosen for the vehicle 10 perpendicular to the threat aircraft's flight path.

[0021] Additional factors should be taken into account when calculating the heading of the descent maneuver. Additional factors to consider include but are not limited to (a) obstacles such as buildings or power lines, (b) no-fly zones or operational keep-out zones, and (c) high traffic areas such as major roads, parking lots, or pedestrian paths. If these types of obstacles are known to the system, a descent heading can be chosen that is as close to the optimal heading as possible without interfering with these other obstacles. Executing the Descent Maneuver

[0022] Once the system has calculated the avoidance maneuver, the rotorcraft 10 can execute it. During this time, additional alterations may be made to the path as more information is collected about the threat aircraft 20. For example, as the threat aircraft 20 changes location, the descent heading can be adjusted to maintain maximum distance between the two vehicles. Additionally, if the threat aircraft 20 passes and is no longer a threat, the avoidance maneuver may be aborted and the rotorcraft 10 can resume normal operations. The exact implementation of executing the maneuver can include, but is not limited to (a) horizontal and vertical velocity set points, (b) a series of position set points, or (c) full path trajectory planning and control.

[0023] FIG. 4 is a simplified block diagram of select components of a representative rotorcraft 10 in accordance with one or more embodiments. The rotorcraft 10 includes a control system 22 for controlling operation of the rotorcraft 10, a power supply 24 for powering the rotorcraft 10, a set of rotors 26 driven by motors 28, and a communications module 30. In one or more embodiments, the rotorcraft 10 also includes an integrated ADS-b or similar aircraft tracking receiver or a sensor such as RADAR, artificial vision-based or acoustic-based sensors 32 for acquiring information about a threat aircraft. In one or more embodiments, the rotorcraft 10 receives information about a threat aircraft from a ground-based sensor or system using the communications module

30.

[0024] The control system 22 includes a flight controller system for maneuvering the rotorcraft 10 by controlling operation of the rotors 26. The control system 22 can include one or more microcontrollers, microprocessors, digital signal processors, application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or any general-purpose or special-purpose circuitry that can be programmed or configured to perform the various functions described herein.

[0025] The processes described above (e.g., for acquiring information about a threat aircraft, calculating an avoidance maneuver, and controlling the rotorcraft to execute the avoidance maneuver by the rotorcraft) may be implemented in software, hardware, firmware, or any combination thereof. The processes are preferably implemented in one or more computer programs executing on one or more processors in a control system 22.

[0026] Each computer program can be a set of instructions (program code) in a code module resident in a random access memory of the control system. Until required, the set of instructions may be stored in another computer memory.

[0027] Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to form a part of this disclosure, and are intended to be within the spirit and scope of this disclosure. While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present disclosure to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Additionally, elements and components described herein may be further divided into additional components or joined together to form fewer components for performing the same functions. Accordingly, the foregoing description and drawings are by way of example only, and are not intended to be limiting.

[0028] What is claimed is: