Underground Drone Recommendation

[navin000]

Hi I am looking to purchase a drone for exploring underground inaccessible(un-supported) areas of a operating mine site. There are obviously many limiting factors to get a drone running compared to flying in open spaces like;

• No GPS
• Effectively total darkness.
• No retrieval possible if drone crashes
• Walls in every direction
• No line of sight to the drone.

The main purpose is to gain information of the rock condition in these inaccessible areas due to safety. Ideally the drone would need

• To take video footage of the cave in total darkness ie have lights or low light cameras
• have the ability to hit (and survive) or automatically avoid the sides of the cave.
• Ideally immune to dust, and humid environments.

Being new to the world of drones I was hoping the experts on this forum who breathe drones would know if there is anything out there that would be up to the task. I was leaning towards the Phantom 4 but its avoidance tech is limited to the forward direction only and would be totalled if it ascended into the roof.

 

[GJH105775]

Hmmmm, sounds like you would need a caged frame. Also sounds like you are going to have some serious problems getting a signal in there. I'd suggest the smallest possible frame that you can get the battery life you need.

What are the characteristics of the cave? Are you going to have a lot of rock between you and it, and are there a lot of twist and turns? Perhaps even a 3D mapping setup with autonomous flight could be used that way GPS would not be as important and nor would signal.


Provide as much info as possible hahaha. This is going to be a challenge. Might even do a few mini quads or land rovers to repeat the signal. Perhaps even making some cheap repeaters to drop as you go one time then making return trips without that added weight. Any ham guys know if you can use ultra-low frequencies for this?

 

[navin000]

The main purpose would be to fly into a blasted void which is connected to a supported drive that the operator can stand in safely. The void is approximately a cylinder on its end with a circular base of 12m diameter and 20m high to the roof, the area will be semi filled with rubble. Access would be a 2x1m hole with the operator approximately 10m from the entrance to the void.

So its less for exploring long stretches of caverns. It would be a more local void inspection after initial void creation and effectiveness of additional explosives at intervals to form the shape we need.

The cage is an excellent idea. Is avoidance technology there for 360 coverage or is it still in its infancy?
Below is a link to a droid flying inside a stope(cave) to get the idea. That someone has tried. (Not mine)

The operator in the video seem to have line of sight (You can see the high-vis reflecting). We would we further out to mitigate risk in case of a rock fall event.

 

[GJH105775]

Check this out, I think the lower frequencies would be needed if you could penetrate the rock.

Realistically on multirotors and planes we often use what is called a LRS (Long Range System) which uses:

1. 5.8GHz
   1. Small antenna
   2. Free band (no HAM license)
   3. Most common FPV frequency
   4. Cheap
   5. Clearest picture
   6. Does not penetrate well and is plagued with multipath propagation (mitigated with polarized antennas like cloverleaf or skew planar)

2. 2.3/2.4GHz
   1. Usually used for control, but is often considered superior for FPV due to increased range and a clear picture
   2. Free band (no HAM license)
   3. small antenna
3. 1.3GHz
   1. Great range
   2. little lower quality video
   3. anteans are bigger and more suited to bigger multirotors or planes
   4. Little more costly equipment
4. 900MHz
   1. Long range
   2. Terribly big antennas suited for larger planes
   3. not very clear picture
5. 433MHz
   1. Almost only used for control
   2. really long range (50 miles is not too unusual in good conditions)
   3. great penetration of trees, and reasonable hills
   4. will almost certainly go further than your video feed
   5. not too costly if you have a modular transmitter
6. 72MHz
   1. Free band (no HAM license)
   2. really good penetrating capabilities
   3. Super cheap in comparison to most

I think you could add multiple U/S sensors around it to keep the craft off of walls and ceilings, check this video out. It should be opensource:

 

[GJH105775]

As for obstacle avoidance I'm going to ask someone really quick who may be able to give you an answer or better enlighten you.

 

[Jon McBride]

It is very possible to set up avoidance on ship. Currently using a DJI Matrice with the guidance system installed. Avoidance parameters could be setup to allow for tighter space, but they work in conjugation with optical sensors as well.