400B. After assembly of the motor mount and motor 208, check that all bolts are all torqued down tightly and ready for flight.

Grounding Issues

This entire disclosure will repeatedly refer to various proprietary grounding strategies, of which the following is just one. It is important that all parts of the UAV 104 are properly grounded in order to prevent Electro-Static Discharge (hereinafter, ESD) built up in surrounding air, which could adversely affect readings of the detector 108. Accordingly, FIG. 5 shows a grounding Printed Circuit Board (hereinafter gPCB) 500. The gPCB 500 is sandwiched between the nut holder and the bottom plate 250 and allows the components of the UAV 104 to be grounded. Additionally, the ground connections of various servo connectors are also used.

During assembly, use a multimeter to insure low resistance between propeller mount screw hole on a rotating motor bell to a bare metal surface located inside the mounting holes of an arm 204. Resistance should be lower than 200 ohms.

For further grounding, a servo cable can be easily repurposed by removing the pins other than ground and connecting it to one of the servo pin headers for the arms, with the other end soldered to one of the gPCB's grounding pads. Coming out of the grounding gPCB 500, a singular female pin connector can be used to connect to a grounding line going to the detector coil when installed.

After assembling all of the arms 204, attach them to the center-core 112 using the following steps. As shown in FIG. 6, first set up the middle plate 600. The grounding PCB 500 will need to be installed between the nut holder and the middle plate 600. This middle plate 600 provides grounding to all the parts mounted thereto as well as a few other points to connect grounding wires from the metal detector 108. The gPCB 500 should be oriented so that the extra grounding connections are facing towards the back of the UAV 104.

Each arm 204 of the UAV 104 is mounted between the bottom 250 and middle 600 plates of the center-core 112 through two screws, thereby forming the X-pattern 224 shown in FIG. 2A.

The first two arms 204 are mounted across from each other with wing nuts on the outward mounting hole. The other two arms 204 are mounted using hex nuts. The wing nuts are used so that the UAV 104 can easily fold up into a transport case (not shown).

Between each arm 204 and the center plate 600 is a 3D printed spacer. In an embodiment, the center plate 600 can be made from carbon fiber (CF). The top spacer contains an opening for the wires coming out of the arm 204 while the bottom spacer is mostly solid and does not provide any openings.

Mount all arms 204 by installing them in the correct location/orientation, running the bolt through the two inner holes of the arm 204. The middle plate 600 is then installed on top with a wing nut or hex nut, depending on the location.

As shown in FIG. 7, the various connections coming from the hole in the top of the arm 204 need to be guided through the curved slots on the middle plate 600. FIG. 8 shows a partial view of a leg mount 800. To assemble a leg mount 800, insert a bolt 800A with a lock washer 800B, washer 800C, and 3D printed mount part 800D into the hole from the top through the arm 204 and through the 3D printed lower part 800E which needs a nut 800F inserted into the hex hole. Tighten this bolt down snugly until the lower part 800E fits along the edge of the arm securely. Once the leg mounts 800 are installed, the various legs 1000 can be screwed on and off easily.

The landing legs 1000 are configured to hold the UAV 104 off the ground thereby allowing the metal detector 108 to be mounted on the underside of the UAV 104. As shown in FIGS. 10A-10B, these landing legs 1000 can comprise a carbon fiber tube, a bottom cap which acts as a pad on the ground, and a top cap 1008 that mounts to the arm 204.

When constructing a new landing leg 1000, it is necessary to correctly drill a hole in the carbon fiber tube so that the top end cap 1040 can be secured to the remainder of the body of the landing leg 1000. To do this, use a 3D printed sleeve drilling template 904 as shown in FIGS. 9A-9C. Push the carbon fiber tube all the way into the guide, then drill a hole all the way through. A drill press is recommended to ensure the hole is straight.

FIG. 9A is a first image shows the leg 1000 next to the drill sleeve template 904. FIG. 9B shows how an upper portion 912 of the leg 1000 fits into the sleeve 904. FIG. 9C shows the final result after using the sleeve to drill a hole 908 in the upper portion 912.

As shown in FIG. 10A, each leg 1000 has a hex nut 1020 embedded into the mount for easy installation and removal. FIG. 10A is a cut-away view of portions of the leg 1000, while FIG. 10B is a fully-enclosed view of the same.

First, assemble the top cap into the end of the leg 1000 with the drilled hole. Before inserting, push a nut 1020 into the hex slot and temporarily secure it with a bolt so the nut does not fall out during assembly. When pushing the insert in, ensure that the drilled hole lines up with the hole through the insert. Slide a sleeve 1012 on between the top cap 1008 and drilled hole before installing a bolt 1004, washer 1016, washer 1024, lockwasher 1028, and locknut 1032 to secure the top of the landing leg 1000. The bottom cap can now be installed and should press all the way in by hand.

Repeat the steps for building the arms 204 and legs 1000 until a quantity of 4 is reached, as shown in FIG. 11. To re-cap from earlier, the motors 208 on two of the arms 204 will need to be clockwise spinning rotation, and the other two motors 208 will need to be counter-clockwise spinning rotation with respect to FIG. 3. All other steps will be mostly identical, except that a tilt plate orientation depends on the spinning direction of the motor 220 on each arm 204.

The legs 1000 can be easily replaced if damaged. Extras will be provided at sale each system 100, e.g. in spare parts kit packaged with every copy of the system 100 that is manufactured. The UAV 104 operates in rough environments where there is no time or means for delicate handling and TLC. Thus, the UAV 104 is arranged such that each leg 1000 can be quickly and easily unscrewed, repaired or reassembled, then screwed back onto the arm 204.

As stated earlier, the middle section of the UAV 104 is the center-core 112. As shown at least within FIG. 1B, the center-core 112 contains the FC 116, the RFD modem 120, the remote control (RC) receiver 124, the GPS unit 128, the front sensor hub 132, and the main battery 136 are all located in the center-core 112. The following will now focus on building the electronics and assembling the various plates e.g. upper plate 1300, middle plate 600, and lower (bottom) plate 250.

As shown in FIG. 12, the comm-cube 1200 connects to the center of the FC 116, on a carrier board 1204. The carrier board 1204 is carefully designed to do effective power distribution, yet retain effecting grounding pads. To that end, the carrier board 1204 has markings that show which orientation the comm-cube 1200 should face. The comm-cube 1200 is a type of brain of the FC 116, including numerous sensors as well as a microcontroller that runs specialized-computer-implementation which drive and help operate the UAV 104.

After all connections have been soldered to the carrier board 1204, the FC 116 is assembled to the underside of the top plate 1300. Orient the FC 116 so that it can be mounted to the top plate 1300. Also, the communication-cube 1200 should be facing the top plate 1300 and the connections for the FC 116 should be visible through the window in the top plate 1300. There will also be a specialized cover (not shown) located between top-plate and for the FC 116 to make it rainproof.

FIGS. 13-14 shows mounting the FC 116 to the top plate 1300 using standoffs. During assembly, four standoffs are used on each corner, and one on a middle location. For clarity, only the middle arrangement is shown in FIGS. 13-14. The standoffs space the FC 116 off of the top plate 1300. As shown in FIG. 14, during manufacture, fasten the standoff to the top plate 1300 using a lock washer 1408B and washer 1412C between a bolt 1404A. At the bottom of the spacer/standoff 1416D is the FC 116 followed by another washer 1412C, lock washer 1408B and a bolt 1404A.

A customized set of parts encase the RFD modem 120. FIG. 15 shows how to position the RFD modem 120 to function properly. Specifically, the RFD modem 120 is mounted to the bottom of the top plate 1300 with a heat sink facing down, away from the top plate 1300, and the antenna connections 1504 facing out. Mounting holes are located on the left side of the top plate 1300. Plug a connector and wiring into the RFD modem 120.

The RC receiver 124 (RC==Remote Control) is used to manually fly the UAV 104 on rare occasions. The RC receiver 124 is mounted within a customized fitted case that is then mounted to an RH side of the top plate 1300. A hole on the side of the case should align with the pairing button on the receiver.

FIG. 16 shows installing a right side battery rail 1604. Conveniently, the fasteners used for the RC receiver 124 are also used to hold this rail 1604 to the top plate 1300. The case is mounted to the top plate 1300 using two bolts with a longer one being used on a thicker side of the case.

An antenna from the RC receiver 124 will eventually be routed through a small hole in the back of the case. Then, that antenna is fed through another hole next to where its exit is routed back to the other side of the case. A small amount of hot glue can be used to affix the RC receiver 124 inside, but if so, it's important to apply the glue inside the case before pushing the RC receiver 124 to be fully inside the case.

The batteries are installed between four battery rails that are assembled to the upper plate 1300. These rails hold the battery in place during flight of the UAV 104. In the last step, the right side battery rail was installed with the RC receiver 124.

Accordingly, now install a left side rail using two bolts, washers, lock washer, and lock nuts. Next, install the inner battery rails using four bolts, washers, lock washer, and lock nuts. The right side inner rail covers an access hole that will need to be accessed later when wiring the FC 116. It is best to leave one of the bolts unassembled until wiring is complete. After wiring is complete, the bolt will need to be installed to mount the inner battery rail.

An example sensor hub 132 is shown in FIGS. 17A-C, and contains mounting locations for the rangefinder as well as other locations to mount other cameras and sensors. The sensor hub 132 is designed to mount on the front of the UAV 104 at an angle so that it can “see” ahead of the UAV 104 and adjust its altitude according to terrain. The assembly consists of the case 1708, lid, and tiltplate 1732 (FIG. 17C) to angle the case.

First the rangefinder and other electronics e.g. a camera equipped with e.g. shape-recognition software such as e.g. UXOWIEDEROW shapes need to be assembled into the sensor hub 132. It is understood that the desired UXO shapes change constantly as warfare changes. Accordingly, the system 100 works from a preconfigured shape-library which is continually updated over time. The rangefinder 1704 fits within the case 1708 with a channel 1712 for various cables 1716 to pass through.

FIG. 17C shows how the sensor hub 132 is mounted to the front of the UAV 104. The sensor hub 132 uses the tilt plate 1732 for angling it so that the rangefinder always looks a bit ahead of the UAV 104. As shown in FIG. 17C, the sensor hub 132 is mounted to the underside of the top plate 1300, on the front of the UAV 104.

FIG. 18 shows the GPS unit 128 (again, this includes GNSS, not just GPS) which is used to determine where the UAV 104 is located and inform the GCS 106. The GPS unit 128 communicates with multiple satellites to triangulate position. The GPS 128 is mounted to a 3D printed extension (riser) 1804 that puts it above the UAV 104, thereby avoiding electrical interference. Again, the expression “GPS unit” is just a label, for quick recognition only, and should not be considered limiting. Other non-GPS mechanisms can also be used.

The GPS unit 128 is mounted to the top of the riser 1804 that connects to the top of the UAV 104. As shown in FIG. 18, mount the GPS adapter plate on top of the stand using three bolts with spacer, washer, lock-washer, and locknuts. Run the cable through the riser 1804 from the top down and pass the cable through the circular cutout where the GPS stand mounts. The GPS unit 128 can then be mounted to the top plate 1300 using four bolts, spacers washers, lock washers, and locknuts.

After the GPS unit 128 is assembled to the riser 1804, this assembly can be mounted to the top plate 1300 of the UAV 104, using pre-machined holes. Use two bolts, washers, lock washers, and wingnuts to fasten the GPS unit 128 (including risertower 1804) to the top plate 1300. Wing nuts are used to easily collapse the GPS assembly tower for transportation. If collapsing is not needed, the GPS risertower 1804 can be installed with lock nuts instead.

The batteries are held to the top 1300 using e.g. two straps. These are then buckled down tightly to hold the batteries in place. The top plate 1300 will have the two battery straps extend through dedicated slots machined therein. Starting from a rear slot, feed the strap from the top down through that slot, then back out through a front slot. The buckle should be closer to the rear, facing up so that the clamp can close (verb) when a battery is installed. During manufacture, make sure this strap runs above any cables on the underside of the top plate.

FIG. 19 shows how the top 1300 and middle 600 plates are mounted using e.g. eight rubber dampeners with a short spacer on the bottom, and a long spacer on the top. The rubber dampeners are used to isolate any vibrations from the UAV motors to the FC 116.

During assembly, start with the middle plate 600 by taking the bolt 1904, add a lock washer 1908, put this bolt up through the middle plate and then add the bottom spacer 1912 to the bolt after the plate. Then screw in the dampener into the bolt after the spacer 1912. Do this for all eight dampener and spacer sets (only one of which is shown in FIG. 19).

Line up the long spacers 1916 on top of the dampener. Once all the spacers are set, align the top plate 1300 by its holes. Bolt the top plate 1300 into place by using a bolt 1920, with lock washer 1908 nearest the head of the bolt 1920, and washer 1924 that will touch the plate 1300. Screw in these bolts to the holes that are aligned with the long spacers 1916.

Two separate DC/DC converters are utilized within the UAV 104, both mounted to the front of the UAV 104 on the bottom plate 250. These are 24V DC/DC and a 12V DC/DC converters. Each is attached with a 3D printed plate with inset nuts to mount flush with the plate 240. The bottom plate 250 with the winch mount 2104 must be assembled first in order for the DC/DC converters to be mounted, because two of the mounting screws go all the way through the rod center mount.

The 24V DC/DC converter is mounted to the UAV 104. Two lock nuts and lock washers need to be pressed into the hex-shaped holes on the 24V DC/DC converter mount. The mount then needs to be assembled to the bottom plate 250.

The 12V DC/DC converter is mounted to the UAV 104 by bolting to a mount at the front of the bottom plate 250. This mount will sit beside the other DC/DC converter adapter. Two lock nuts and lock washers need to be pressed into the hex-shaped holes on top of the 12V DC/DC converter mount.

The mount then needs to be assembled to the bottom plate 250. This step is very similar to the other DC/DC converter assembly. It is best to prepare the DC/DC converters before installing on the UAV 104. After preparing the converters, they can be mounted to the DC/DC converter mounts (DCM). The mounts are located under the bottom plate 250, at the front of the UAV 104.

After the DC/DC converters are installed, the 3-pin servo connection added will need to be wired to the FC 116. The arms 204 should now be connected to the FC 116.

A connector and 2 wire servo connector is routed through a slot in the middle plate 600. In an earlier step, connectors were soldered onto the FC 116 at each corner. Plug the connectors coming from the middle plate 600 into the corresponding connector on the FC 116. Each arm 204 should have this connector. Make sure the orientation of the servo connector is correct according to the markings on the FC 116. All four arms 204 are connected the same way.

The RFD modem 120 is connected through to the FC 116. A cable from the RFD modem 120 should run to the top of the FC 116. There is a cutout in the upper plate 1300 to access ports within the FC 116. A plurality of antennas come with the RFD modem 120, and should be oriented to always stand vertical and be parallel with each other.

At this stage of assembly, the GPS unit 128 can be connected to the FC 116.

Begin Winch 2700+Detector 108

FIG. 20 show some details of the detector 108. The coils control box 2012 controls the upper/lower coils 2004, 2008 and is mounted underneath the UAV 104. This location facilitates better electrical connections to the upper/lower coils 2004, 2008.

A mounting adapter for the coils control box 2012 will need to be installed first. The mounting adapter is mounted to the underside of the bottom plate 250 using already drilled holes. Fasten the mount using two screws with flat washer on both sides of the part and plate, with a lock washer and lock nut on the topside of the bottom plate 250. To mount the coils control box 2012, use two bolts extend through the two mounting holes through the box. These bolts will fasten down into embedded locknuts in the adapter installed earlier.

The detector 108 utilizes time domain metal detection (including non-ferromagnetic items). To achieve this, it is necessary to have good signal quality. The detector 108 achieve noise reduction through a matching subtraction process, thereby compensating noise with multiple antenna coils 1004/1008.

The detector 108 is different from what was used in ground-based (cart) implementations. Such non-UAV ground-based detectors may be 2 or 3 times heavier than the detector 108. The detector 108 also has a different coil layout as the upper coil 2004 is not present on the conventional sensor. The upper coil 2004 was added because any particular UAV including the UAV 104 creates a lot of electromagnetic interference. A lot of that noise is removed by introducing the winch 2700 and moving the coils 10041008 away from the UAV 104.

Even more noise is reduced by placing a second (upper) receiver coil closer to the UAV 1004 and then subtracting the signal from the main (lower) receiver coil 1008. As the upper coil picks up mostly drone noise and the lower coil mostly the useful signal, this schema reduces noise a lot.

Power Considerations

The system 100 takes various steps to maximize power conversation, which lends to better detection-outcomes and spanning wider areas of land-mass. The winch 2700 uses no power when fully retracted or extended, it doesn't have a separate battery, and the power draw when winching is insignificant to what the drone motors consume. The power consumption of the sensor hub 132 is insignificant compared to the power consumption of a motor for the UAV 104.

FIGS. 27A-B-C show an example winch 2700, mainly its body-only, not yet installed within the system 100. The winch 2700 was developed so that the detector 108 can be retracted up to the center-core 112, or extended away from the UAV 104 during operation. The winch 2700 can also be attached and detached at will to allow easier transport. The winch 2700 consists of a mount on the center-core 112, the body of the winch 2700 which holds the motors, a paracord line 2408, and the electronics. The winch 2700 is eventually attached to the detector 108.

The winch 2700 is controlled by the GCS 106. The winch 2700 has a controller therein pre-configured with various features such as receiving winch-control commands “full up”, “full down”, “stop”, and other commends. The controller then controls a winch motor accordingly, including reading some end switches.

The GCS 106 also directs the winch 2700 to extend or retract, depending on what task the UAV 104 is doing. For example when doing a normal survey mission, the UAV 104 takes off from ground, first extends the detector 108, then does a calibration, and only then goes to the mission area. Then UAV 104 then conducts the surveys the area until the battery runs out, or the survey is finished, retracts the detector 108, and comes back to land. The entire process starts over according to the user and the GCS 106, such as but not limited to when the battery is swapped, a new mission is planned, repairs, or other of many possibilities.

When the system 100 and detector 108 is operating (e.g. at its planned destinationroute), the two coils 1004/1008 are always separated at a fixed specific distance. When the system 100 and detector 108 is in motion but not operating, or in storage, the two coils 1004/1008 are always together when retracted.

As shown at least within FIG. 20, the detector 108 consists of a smaller upper coil 2004 and a bigger lower coil 2008, with a fixed distance in between when detecting. All hardware around the detector coils 20042008 are assembled using plastic or nylon screws to increase reading accuracy.

The bottom coil 2008 is made up of the large coil and a brace that attaches the coil to the winch 2700. The back edge of the winch mount 2104 is centered on a coil support brace. During installation, while the brace is in-location, mark the locations of the 3 screw holes. Use the vertical holes in the brace to mark the 3 hole locations in the fiberglass square tubing that connects the coil 2008. Insert the fiberglass square tube into the bottom mount. While sitting in the winch mount 2104, mark the mounting holes on the tube, then drill each mark with a drill bit.

The winch mount 2104 is then assembled using nylon bolts, with nylon washers and nuts. In a later step, the paracord 2408 is fastened around a top nylon bolt in a later step.

The paracord 2408 can also be known as a “bottom rope”. A top rope (not explicitly shown herein) acts to keep the top coil 2004 at a fixed distance when extended. Meanwhile, the bottom rope (paracord 2408) is extended or retracted by the winch 2700, and controls movement of the bottom coil 2008.

The bottom coil 2008 uses some small terminals connected to the grounding wires that run around one or more coil connections. These terminals will be fastened to the coils-connection box 2012. Some connectors are added for convenient disassembly if repair or adjustment is necessary.

The top coil 2004 is assembled using custom 3D printed parts that allow it to attach to the vertical fiberglass pole. From FIG. 20, it is apparent that the top coil 2004 is smaller than the bottom coil 2008 in diameter, but their footprints are the same. When the detector collapses 108, e.g. for transport and storage, the coils 20042008 are on top of each other. When deployed, the coils 20042008 have to be a predetermined distance away from each other to operate properly.

The top coil 2004 consists of four hollow fiberglass rods. Each one feeds into a L-shaped holder that is zip tied to the top coil 2004. When tightening these zip ties, make sure the coil 2004 is centered to the winch mount 2104. These parts all meet in the middle into an X-shaped holder that has the main vertical fiberglass tube going through its middle.

Align the center piece correctly, so that the rope attaching the coils 20042008 to the winch 2700 runs through the guide hole. Make sure the coils are aligned and centered exactly. Attach the top coil 2004 to the vertical fiberglass pole 2108 by sliding it on from the top. The vertical fiberglass pole 2108 should sit on top of a bottom coil mount.

Now that the top 2004 and bottom 2008 coils are built, the detector assembly 108 needs a few more components to finish its installation, and these relate to the winch 2700.

With the top 2004 and bottom 2008 coils assembled to the fiberglass pole 2108, the winch 2700 can now be added. Handle the winch 2700 with caution. There are some sensitive electronics and mechanical switches therein that could be damaged if not careful.

Line up the winch correctly before sliding it over the vertical fiberglass winch pole 2108. There is an opening through the winch 2700 for the winch pole 2108 to slide through. Also, a set of bearings should touch the fiberglass tube when moving up and down.

The winch paracord 2408 should be coming down from the center and against the fiberglass tube. Later, attach the end of the paracord 2408 by temporarily letting the winch 2700 rest on top of the top coil 2004.

The portion of the paracord 2408 coming out of the winch 2700 will be hanging down about a foot from the bottom of the winch 2700. During assembly, feed the paracord 2408 through the guide in the top coil 2004. This guide should be directly below where the paracord comes out of the winch. With a loop on one end of the winch paracord 2408, push the loop into the slot onto a bottom coil center mount and fasten.

The winch 2700 is designed so that when the detector 108 is deployed, the distance from the center pole to the bottom of the winch 2700 to the top of a center mounting part has a predetermined range. This distance is then fine-tuned to reach optimal detection performance.

Using a top coil rope, which is separate from the paracord 2408, attach one end to the bottom of the winch 2700. There are two small holes that can be used to tie the rope with a ziptie. Add a rope weight to the top coil rope which should be able to slide on the rope. The rope weight keeps the top rope from being entangled in the various propellers of the UAV 104 when retracting the coils 20042008.

The other end of the top rope will be attached to a ropemount. The loop on the end of the rope should be just big enough to fit over a knob and be secured into place.

After the coils 20042008 are assembled to the vertical tube, a component called a top stop