Field

[0001 ] The present invention relates to situational awareness, navigation and communication for low-cost unmanned aerial vehicles (UAVs) launched from guns as projectile munitions, such as rifle-grenade, grenade, shoulder launched, tank, mortar, and artillery projectiles.

Background

[0002] 'Swarms' of low-cost, gun-launched UAVs have been proposed to autonomously overwhelm an adversary. Each member of the swarm (or 'swarmbot') has to be able to navigate, communicate, and be situationally aware of its environment - its fellow swarmbots, the enemy, and friendly manned systems - and then act.

[0003] Swarmbots have critical size, weight and power constraints that preclude traditional solutions for situational awareness, navigation and communication. Traditional solutions for situational awareness, such as Light Detection and Ranging (LiDAR) and thermal infrared imaging, are simply too large and heavy to be flown on small, gun-launched UAVs. In addition, the traditional solutions of global positioning system (GPS) for navigation, and radio frequency (RF) for communication, are vulnerable to jamming. Future swarmbots need to be able to navigate and communicate when GPS and RF communication links are erratic or lost.

[0004] A need therefore exists for alternative solutions for providing low-cost, gun- launched UAVs with situational awareness, navigation and communication capabilities.

Summary

[0005] According to the present invention, there is provided an unmanned aerial vehicle (UAV), comprising:

a projectile body;

a propulsion system foldably deployable from the projectile body;

a synthetic aperture radar (SAR) system comprising a SAR antenna fixedly and non-rotatably arranged on the projectile body; and a control system connected to the propulsion system and the SAR system, wherein the control system is configured to control:

orientation of the projectile body and thus orientation of the SAR antenna; and

operation of the SAR system so that the SAR system is selectively operable in one or more of:

a situational awareness mode;

a navigation mode; and

a communication mode.

[0006] The propulsion system may comprise foldably deployable rotor arm assemblies.

[0007] The control system may comprise one or more microprocessors, an inertial measurement unit (IMU) and an altimeter module.

[0008] The SAR antenna may comprise one or more conformal linear array antenna elements mounted on one or more outer peripheral surfaces of the projectile body of the UAV.

[0009] The SAR system may operate at 77 GHz.

[0010] In the situational awareness mode, the SAR system may be selectively operable as a radar beacon to generate radar beacon signals.

[001 1 ] The radar beacon signals may be used for one or more of identifying, locating, ranging, and tracking one or more neighbouring friendly UAVs.

[0012] In the situational awareness mode, the SAR system may be selectively operable as an imaging sensor to generate a two-dimensional (2D) or three-dimensional (3D) SAR image.

[0013] In the communication mode, the SAR system may be selectively operable as a radar communication system to generate radar communication signals. [0014] The radar communication signals may be used for digital communications with one or more neighbouring friendly UAVs.

[0015] The UAV may further comprise a global positioning system (GPS) transceiver configured to generate GPS signals.

[0016] The GPS signals may be used for one or more of identifying, locating, ranging, and tracking one or more neighbouring friendly UAVs.

[0017] One or more of the SAR image, radar beacon signals, radar communication signals, and GPS signals may be fused and processed to provide the UAV with situational awareness of one or more objects in the surrounding environment.

[0018] The one or more objects may comprise one or more of neighbouring friendly UAVs, neighbouring unidentified UAVs, targets, and terrain.

[0019] In the navigation mode when the GPS signals are jammed, the SAR image may be used for navigating the UAV based at least in part on comparing terrain in the SAR image with a terrain database.

[0020] The one or more neighbouring unidentified UAVs may be identified based at least in part on comparing locations of the one or more objects in the SAR image with one or both of the GPS locations and the radar beacon signals received from the one or more neighbouring friendly UAVs.

[0021 ] The one or more neighbouring friendly UAVs and the one or more neighbouring unidentified UAVs may comprise one or more swarms of UAVs.

[0022] The present invention also provides a swarm of UAVs, comprising a plurality of the UAVs described above.

[0023] The present invention further provides a method of operating a UAV, comprising: providing a SAR system comprising a SAR antenna fixedly and non-rotatably arranged on a projectile body of the UAV; selectively providing the UAV with one or more of situational awareness, navigation and communication capabilities based at least in part on the SAR system.

[0024] The present invention also provides a method of operating a swarm of UAVs, comprising operating a plurality of the UAVs described above in a swarm of UAVs based at least in part on the SAR systems of the plurality of the UAVs.

Brief Description of Drawings

[0025] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic block diagram of a UAV according to an embodiment of the present invention;

Figure 2 is a line drawing of the UAV of Figure 1 ; and

Figure 3 is a schematic diagram of the UAV in operation.

Description of Embodiments

[0026] A UAV 10 according to an embodiment of the present invention may comprise a small, inexpensive and expendable UAV. The UAV 10 may be hand-launched and/or gun-launched. A suitable UAV 10 is, for example, a Drone-40 or Drone-80 quadcopter described in the present applicant's US patent application US 15/700,436, which is hereby incorporated by reference in its entirety. In some embodiments, the gun- launched UAV 10 may have a form factor corresponding to a 40 mm rifle-grenade munition or an 81 mm mortar munition.

[0027] Referring to Figures 1 and 2, the gun-launched UAV 10 may generally comprise a projectile body (or casing) 12, a propulsion system 14, a power source 16, a control system 18, and a SAR system 20. As described in US 15/700,436, the UAV 10 may also comprise a payload (not shown) and a propelling charge (not shown). The propulsion system 14 may, for example, comprise foldably deployable rotor arm assemblies. The control system 18 may, for example, comprise one or more microprocessors, an inertial measurement unit (IMU) and an altimeter module. The electronic components, including the SAR components, may each comprise low-cost, commercial off-the-shelf (COTS) components. The SAR system 20 may comprise a SAR antenna fixedly and non-rotatably mounted to or arranged on the body 12. The SAR antenna may, for example, comprise one or more conformal linear array antenna elements mounted on one or more outer peripheral surfaces of the body 1 2 of the UAV 10. The SAR system may, for example, operate at 77 GHz. The projectile body 12 may have a central vertical axis and the SAR antenna may have a field of view generally perpendicular to the central vertical axis.

[0028] The control system 18 may be configured to control orientation of the projectile body 12 and thus orientation of the SAR antenna, and to also control operation of the SAR system 20 so that the SAR system 20 is selectively operable in one or more of a situational awareness mode, a navigation mode, and a communication mode.

[0029] For example, in the situational awareness mode, the control system 18 of the UAV 10 may be configured to autonomously control operation of the propulsion system 14 so as to rotate the body 1 2 of the UAV 1 0 and thereby rotate the SAR antenna so that the SAR system 20 generates a SAR image of a surrounding environment. The fixed SAR antenna and the autonomously rotatable UAV 10 may collectively act or function as conventional rotating synthetic aperture radar (RoSAR) system with a conventional rotating SAR antenna. It will be appreciated that the SAR system 20 may also be selectively operated in other non-rotatable modes with fixed angular fields of view when the UAV 10 is flown non-rotationally.

[0030] In the situational awareness mode, the SAR system 20 may be selectively operable as a radar beacon to generate radar beacon signals. The radar beacon signals may be used for one or more of identifying, locating, ranging, and tracking one or more neighbouring friendly UAVs.

[0031 ] In the communication mode, the SAR system 20 may be selectively operable as a radar communication system to generate radar communication signals. The radar communication signals may be used for digital communications with one or more neighbouring friendly UAVs. The digital communications between the one or more neighbouring friendly UAVs may comprise mobile 'ad hoc' network communications, such as adaptive mesh communications. [0032] The UAV 10 may further comprise a global positioning system (GPS) transceiver 22 configured to generate GPS signals. The GPS signals may be used for one or more of identifying, locating, ranging, and tracking one or more neighbouring friendly UAVs.

[0033] Referring to Figure 3, one or more of the SAR image, radar beacon signals, radar communication signals, and GPS signals may be fused and processed to provide the UAV 10 with situational awareness of one or more objects in the surrounding environment. The one or more objects may comprise one or more of neighbouring friendly UAVs, neighbouring unidentified UAVs, targets, and terrain.

[0034] In the navigation mode when the GPS signals are jammed, the SAR image may be used for navigating the UAV 10 based at least in part on comparing terrain in the SAR image with a terrain database.

[0035] The one or more neighbouring unidentified UAVs may be identified based at least in part on comparing locations of the one or more objects in the SAR image with one or both of the GPS locations and the radar beacon signals received from the one or more neighbouring friendly UAVs.

[0036] The one or more neighbouring friendly UAVs and the one or more neighbouring unidentified UAVs may comprise one or more swarms of UAVs. A plurality of the UAVs 10 may be operated in a swarm of friendly UAVs 10.

[0037] Embodiments of the present invention provide low-cost, gun-launched UAVs that are both generally and specifically useful for providing situational awareness, communications and navigation during swarm operations in hostile environments.

[0038] Embodiments of the present invention may use a fan beam SAR antenna so that in use the UAV rotates at a constant angular velocity thereby sweeping the fan beam radar signal around the UAV enabling a SAR image to be formed of the immediate environment. The SAR may comprise millimetre (mm) wave radar that may also be used for beaconing where different UAV swarm members transmit on different frequencies in the mm-wave band to signal not only their position but their current state and intent. This beacon signal may be used by other UAVs to determine the range, position and heading (or bearing) of other swarm members. The beacon intent signalling may also be used with decentralised and autonomous planning algorithms to account for actions of other swarm members and adjust their behaviour accordingly.

[0039] The mm-wave radar of embodiments of the present invention may be jam resistant as the atmosphere heavily absorbs radiation in the 77 GHz frequency band. This may advantageously allow for clear operation over several hundred metres between swarm members and targets, however a jamming source located several kilometres away would have great difficulty in getting a jamming signal to propagate at a level high enough to disrupt the UAV swarm operations.

[0040] The SAR system of embodiments of the present invention may be used to identify key features in surrounding terrain such as roads and power lines, and this information may be used to map the UAVs position against a terrain database enabling autonomous navigation in GPS-denied environments.

[0041 ] The SAR system of embodiments of the present invention may also be used for digital communications that due to the mm-wave band are difficult to jam. This digital communications channel may be used to convey information including GPS signals from a high endurance high altitude and difficult to GPS-jam swarm member. Using this information plus local intra-swarm positioning may enable an accurate position to be obtained.

[0042] Embodiments of the present invention use the concept of RoSAR in a low-cost, gun-launched UAV to create a 360 degrees 2D SAR image which can identify all the objects around the UAV within a specific range. Instead of rotating the SAR antenna around the structure of the UAV itself, a conformal linear array antenna may be fixedly and non-rotatably mounted on the periphery of the UAV, and then the UAV may be rotated at a constant speed to provide the SAR image. This will give the drone a unique capability of intelligent situational awareness. The UAV may also be fitted with GPS which will provide the coordinates of neighbouring friendly UAVs via local encrypted radio communications. Targeted objects or unidentified UAVs may be located by comparing the locations created by the SAR image and the known GPS coordinates of friendly UAVs. [0043] For example, some embodiments of the UAV of the present invention equipped with a SAR may track, engage, and classify unmanned aerial system (UAS) targets out to 350 metres following launch from the existing SL-40 grenade launcher in a point and shoot configuration. These embodiments may be equipped with soft (high tensile fabric fired into rotors/propellers) and hard (air burst detonation up to 10 metres from the target) kill options.

[0044] When UAVs are operated in a hostile environment where all GPS satellite signals are being jammed or obscured, each neighbouring UAV may act as an RF radar beacon. In this mode, Doppler processing and communication protocols may be used to not only identify friendly UAVs, but also calculate bearings and ranges from neighbouring UAVs.

[0045] The SAR system of embodiments of the present invention may advantageously operate in the 77 GHz band (W-band), and due to its high frequency this frequency band is suitable for UAV application as the size of the system is quite small and lightweight and can be developed to fit in the space available in the Drone40. In addition, the 77 GHz band is less prone to jamming over short distances due to high atmospheric absorption. Typical systems may operate with a range less than 150 metres.

[0046] The use of SAR and beacon tracking as well as the GPS system in embodiments of the present invention advantageously enables a range of autonomous UAV applications and operations including intelligent situational awareness, digital communications and navigation.

[0047] For the purpose of this specification, the word "comprising" means "including but not limited to," and the word "comprises" has a corresponding meaning.

[0048] The above embodiments have been described by way of example only and modifications are possible within the scope of the claims that follow.