Avalanche Research



Introduction

Avalanche rescue operations are inherently very dangerous operations for rescuers and searchers. The terrain is difficult to navigate on foot and there is high risk and probability of secondary avalanches or “hang-fire”. Searchers put themselves in dangerous positions in unstable environments. The ability to utilize a UAS in this situation would allow searchers to remain clear of potentially dangerous areas and give them more time to assess the area before approaching on foot. Through my experiments I look to test the viability of using avalanche beacons with UAS operations.  

Experimentation 

The experiments will utilize beacons made by BackcountryAccess along with the DJI Matrice 600 UAS. The beacons being used are the BCA Tracker 3 and the Tracker S, two of the most popular beacons used by recreational and professional athletes in the backcountry. The beacons are designed to transmit a signal when the user is skiing, snowmobiling or hiking in the back country. In the event of an avalanche and the user is trapped the beacon will be transmitting a signal that can be picked up by other searching beacons. When in search mode the beacons pick up the signal of the transmitting beacon allowing for searchers to find the target on foot. By using a UAS in this operation it will hopefully allow for faster search times while also allowing the searcher to maintain a safe distance from the search area. There are big obstacles that must be addressed in order for the beacons to properly work with the UAS these main research questions are:

How will the beacon mount to the UAS?
How will we shield the beacon/ UAS from electromagnetic interference?
Will there be any issue of frequencies interfering with drone or beacon?
-       Most likely no the matrice transmits on 2.4 or 5.8GHz while the beacons transmit on 457KHz
What will be the best mission plan for the UAS?
-       Altitude?
-       Pattern?
Will the beacon be able to transmit far enough to be useful?

To start experimentation, I will begin with ground tests to ensure there will be no interference that will be directly effecting the aircraft and its ability to fly safely.

Tracker 3 vs Tracker S

BCA Tracker 3
BCA Tracker S

Images courtesy of backcountryaccess.com

Moving Forward

Moving forward I will begin by creating a few different prototypes for mounting these beacons to a DJI Matrice 600 UAS. These prototypes will be created in Fusion 360 and 3D printed. 3D printing allows for me to quickly make prototypes and easily make alterations if needed. The current goal is to be able to fly an XT2 thermal sensor in the front of the UAS and mount a GoPro or other DJI camera to monitor the activity on the beacon. The use of the GoPro will allow a third member of the flight team to monitor the beacon on a mobile phone from the GoPro feed. I will be posting each prototype and the pros and cons of how they operate.

Week 1: Prototypes/ Ideation

Before doing any in flight testing I will be creating a mount that will allow me to attach an avalanche beacon to an m600 UAS. What I was looking for in a mount is the option to change the angle of the beacon to test which orientation provides the most accurate readings. I am also looking to be able to hard mount the beacon to the platform but also be able to use the mount on a cable system from the UAS in the event interference is too high when hard mounted. 

Drafting

My prototyping phase began with creating a few rough sketches of ideas for mounts I thought may work well. This also allowed me to document measurements of mounting rails and measurements of the beacons. With these measurements I am able to design a multiple mounts that have different capabilities.  Figure 1 shows a first rough sketch of a case that will hold the beacon in place and allow it to be mounted in different configurations to the M600. I began with designing this simple case to allow me to learn Fusion 360, the CAD software I will be using to make the prototypes. 

Figure 1: First Sketch
Figure 2 shows a second sketch ideation that would only allow the beacon to be hard mounted to the M600, this sketch shows the dimensions of the mounting rails on the M600 which are 149.4mm apart on center and are 12mm in diameter. While this sketch is not exactly what I am looking for in the mount it allows me to work out some ideas and understand the dimensions of the product.
Figure 2: Second Sketch
Figure 3 shows a third rough sketch that is most accurate to a mount I am interested in using, it allows the beacon to change orientation as well as removing the beacon case from the mount and being able to use it on a cable system to further the distance from the drone to reduce interference.
Figure 3: Third Rough Sketch 

Next Steps

After brainstorming and creating designs I am pleased with I will be moving to designing these prototypes in Fusion 360. I will start with simple designs to learn the software since I have not used Fusion 360 before. From here I will be 3D printing these prototypes and running test flights.

Week 2-4: Learning Fusion 360/ Fusion 360 Models

From my rough sketches I will be creating multiple designs in Fusion 360. I have not used Fusion 360 software before so I will begin with some simple designs to learn the software and get a feel for how to create models in Fusion 360. I will not be posting images of the first drafts as they are just simple boxes/ cases for the beacon. Figure 4 shows a model that was created from the ideation sketch Figure 2 in my Week 1 post. I used this model to learn a lot of the features of Fusion 360, this model will not be 3D printed as is has many features that prevent it from being printed correctly. The main issues for 3D printing this model would be the overhanging features such as the arms that would connect to the mounting rails. The main issue with this model is that it would only work as a hard mount to the M600. If there are issues with orientation or interference with this mount then there is nothing the user can do to fix those problems.

Figure 4: Fusion 360 Model #1
Figure 5 and 6 show the mount that I will be 3D printing as my first prototype this model is from my rough sketch in Figure 3 from week 1. This model features a 2 piece design that will allow me to hard mount to the M600 with the use of the top piece, as well as using other mounting systems such as cables when using the case/ box for the beacon.


Figure 5: Fusion 360 Model #2
Figure 6: Fusion 360 Model #2

Next Steps

From the Fusion 360 models I will be 3D printing the mount and running test flights.

Week 5: 3D Printing and Mounting

As I mentioned in my previous post I will be 3D printing the Fusion 360 Model from Figures 5 and 6. This is the most versatile model and prototype I have made and I am pleased with the design, the next step is to now test the viability of this mount. Figure 7 shows the 3D printed mount with the Avalanche Beacon in the case. The mount printed successfully and all measurements were accurate in order to mount to the M600 and fit the beacon and the GoPro. The cut out on the face of the mount will allow the user to view the information screen on the beacon, this screen shows the distance in meters you are away from the beacon you are searching for. As mentioned in my first post there will be a GoPro mounted to the front of the beacon case in order to view a live stream of the beacon screen from a phone. I used wing nuts to fasten the beacon/ case to the top mounting piece in order for quick orientation changes.


Figure 7: 3D Printed Mount

Figures 8, 9 and 10 show the beacon fully mounted to the M600 with the GoPro mounted as well. This will be the set up I will be using for my first test flights. As you can see from the figures there is aluminum tape lining the inside of the case as well as taped to the top of the mount. The goal is to reduce the amount of interference between the drone and the beacon.

Figure 8: The avalanche beacon fully mounted to the M600, for the first test runs I will be testing the beacon in the vertical (facing directly down) orientation. 

Figure 9: Side view of the beacon fully mounted to the M600.

Figure 10: Back view of the beacon mounted to the M600, the safety chord is wrapped around the mounting rails as an emergency attachment incase anything on the mount fails. 


Test Runs

Video Feed


Above is a video feed from the first test runs to see the viability of the designed mount and avalanche beacons. As seen in the video feed there are significant issues present with interference between the UAV and the beacon. We see some promising readings at the beginning of the video at lower altitude. When we gain altitude we see a significant drop off in accuracy of readings. This is most likely a combination of interference and also difficulty with the signal associated with the distance from the search beacon and transmitting beacon. These issues must be addressed in a few ways to effectively use the beacon in combination with the UAV.

Ideas to decrease interference

  • Different materials for insulation (currently using aluminum tape)
  • Different material for mounting (metals instead of 3D printing)
  • Use a cable system for mounting to increase distance from the UAV
  • Retractable cable system using servo and a pulley
  • Use insulation directly on the surface of the Beacon
  • Beacon antenna alteration to transmit direct vs omni-direct
For the next test runs the quickest variables to test would be to use cables to increase the distance between the Beacon and the UAV. The mount for the beacon is already created so in order to test cables the box will be removed from the bracket and 4 holes drilled into the box to attach 4 cables. The 4 cables on the corners of the box will allow the beacon to be mounted vertically down or horizontally but will keep the beacon from swaying with the movement of the UAV. This will also help for flight characteristics being unaffected.

The best way to test the effectiveness of this will be to start the UAV and have the beacons transmitting, we can then walk around the UAV on the ground to determine a distance in which there is minimal interference. One this distance is determined cables can be made to length.

If these test runs prove to be ineffective the next step will be to use new materials for the box the beacon is housed in. Typical metals that are used for shielding electromagnetic waves are: steel, copper, aluminum, nickel and zinc. For availability purposes aluminum will be the easiest metal to test and is fairly easy to work with.

Future Developments (Quarantine) 

For future developments to use avalanche beacons with UAV's in search operations the best option would be to create a UAV specific search beacon. There is not a UAV specific search beacon on the market currently. Some companies are able to use aircraft such as helicopters with transmitting and locating features. Being able to use UAV's instead of helicopters could drastically reduce cost and will allow for easy deployment of searches.

The best option for creating a UAV specific beacon would be a beacon that is able to transmit readings to an app such as DJI Ground Station Pro that can be viewed by the pilot. It is also possible to use a third team member to view just the beacon feed from a phone or ipad.

Ideation 

A UAV specific beacon would be best used on a cable system actuated by a servo that can lower and raise the beacon to be out of interference range and can also be retracted if it is affecting flight characteristics. I believe an antenna that only transmits away from the UAV, either forwards or downwards, would be the best option. The beacon will also need to have a bit of a stronger signal than the ones used in these experiments. The beacons used have a recommended range of about 40 meters. This becomes a problem when the UAV will need to increase altitude due to terrain or other obstacles.





















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