Author Topic: Help with a mining robot  (Read 376 times)

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Offline newroboticsuserTopic starter

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Help with a mining robot
« on: June 03, 2014, 08:23:12 AM »
So I decided that I wanted to build a robot that could dig and travel underground. There are obviously a number of different matters to consider, such as how it would move underground, the material it would be made from (it might have to be strong enough that it won't be crushed by the weight of the dirt), how it senses, and how it is powered. One of the fundamental systems I am considering is its drilling system. Considering that the robot will be very small, only about 3 cm in width and height, I decided that the drill is small enough that I could use a drill bit or an auger bit. The primary question that I have is if a drill bit is what I ought to use, or if there is something else that has been made for this particular application.

Offline jwatte

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Re: Help with a mining robot
« Reply #1 on: June 03, 2014, 10:10:34 AM »
That sounds like a project with a lot of fun challenges!
So, the auger digs into the dirt in front of it. Where does that dirt go? It has to be displaced for the bot to be able to move forward.
Also, how will you power this? For how long?
What prevents the body of the robot from spinning instead of the auger; how is it counter-anchored?

Offline newroboticsuserTopic starter

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Re: Help with a mining robot
« Reply #2 on: June 03, 2014, 12:28:19 PM »
Most certainly has a lot of fun challenges, I have found myself engrossed in the project for some time now.

I have been thinking about how the dirt is to be displaced. The width and height of the robot will be nearly the same as the diameter of the drill system. Having continuous tread wheels on the front, I could have the dirt pushed along the sides of the robot. It also occurred to me that the robot could have a width and height that is a slight bit greater than the drill which it possesses. Doing that, I could make the front of it triangular, as to facilitate the movement of the dirt along the robot. I also thought about having a smaller drill system on the back, with the back being somewhat triangular too, moving in in the other direction as the first drill in order to help push dirt behind it.

In order to keep the robot from spinning as opposed to the bit, I was thinking about having two drill bits, both 1.5 centimeters in length, half of the width and height of the robot. That would secure the robot, but would also allow dirt to pack in places where the drill does not occupy. I could make those inclined, which might allow the dirt to move more easily.

I was thinking about making it battery powered. There are a number of high energy density batteries (such as from the site that I will post below), which might possibly offer more energy capacity than I will even need. I will be driving about 4 or 5 motors, which will, say, take a little bit more than 30mA. I would reckon a total load there of 200 mA. There is also the current requirements that will be required for pressure sensors on the front (I am actually going to drive the vehicle into an anthill, just to see what's inside) and for a gyroscope. The only other load I can think of is the rc system. I don't have the knowledge to make it autonomous so I will need to drive it myself. Sending commands from some above ground controller won't be too difficult, I will just need to make it very powerful. Receiving info from the robot will be a different matter, and will require more power the deeper into the ground I go. I was going to make a larger model first and test how much power is consumed by sending information the deeper into the ground it goes. As for the length of time, I don't intend to use it for very long periods of time, but, say, an hour on a particular day.

I also have been considering tethering it, and having a power chord that attaches to it. This will require more force to move, however, the deeper into the ground it goes. I wondered about wirelessly transmitting power to it (I was told that a Tesla Coil was made with this purpose in mind), however, that would be another project in and of itself.

I apologize if the message was too lengthy, I have considered many different issues, and many different solutions to those issues, but these are the best that I have come up with

Link: http://www.batteryspace.com/A123-System-Nanophosphate-LiFePO4-26650-Rechargeable-Cell-3.2V-2500-mAh.aspx

Offline jwatte

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Re: Help with a mining robot
« Reply #3 on: June 03, 2014, 08:28:13 PM »
I'd love to see a motor that can dig into dirt at only 30 mA! Could you post a link?

Quote
I could make the front of it triangular, as to facilitate the movement of the dirt along the robot.

Interesting. Does the dirt compress?

Offline newroboticsuserTopic starter

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Re: Help with a mining robot
« Reply #4 on: June 04, 2014, 04:33:05 PM »
This is a no-load rating. I actually don't know how much current would be used while it is digging. As for the actual motor that I am using, I need to figure out the required speed of the drill in RPMs. I've never actually needed to drill through dirt before, so I don't know how much current will be drawn.

The only reason I would make the front triangular is if the actual body is larger than the diameter of the two drills. I'm hoping that I can make the drills the same diameter as the body of the robot. I would have continuous treads that would travel across the length of the robot which would also, theoretically, move the dirt behind the robot while also pushed forward by the treads. I don't think that the dirt would compress.

I noticed a number of 30mA gearbox motors, and I figured that they would be able to provide more torque:

http://www.amazon.com/260RPM-12GA-Shaft-Geared-Motor/dp/B009IN0AUU/ref=sr_1_1?ie=UTF8&qid=1401920981&sr=8-1&keywords=3v+gearbox+motor+3mA

Offline jwatte

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Re: Help with a mining robot
« Reply #5 on: June 04, 2014, 05:26:47 PM »
Quote
I need to figure out the required speed of the drill in RPMs

I'd also worry about the required power needed to drill in dirt at that RPM. It may be that small motors with low current ratings will not be able to deliver the needed power without melting/burning. In fact, it may be that even small motors with large current ratings will melt/burn :-)
A bit of it depends on what kind of dirt, I suppose. A very light, airy loam is likely much easier than hard-packed wet clay.

Offline newroboticsuserTopic starter

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Re: Help with a mining robot
« Reply #6 on: June 04, 2014, 07:23:05 PM »
I do consider that. However, I don't think that I will need a very high RPM rating. I am not drilling through steel, or wood. Moreover, I am trying to displace the dirt from the front to the back, I don't think that I will need a high speed for that, but a higher torque. That's also why I say that I don't know the RPM, because I think that it will be a good deal lower than a conventional drill's RPM rating.

You may be right, of course. What I was going to do is perform trials before actually making the robot that I speak of. For example, I need to know the resistance of the dirt that I intend to drill into. I could, with that in mind, make a drill and drill bit of the settings I describe (3cm for the larger model, which I intend to use in order to work out the kinks in the design, and I might try and experiment with a 120RPM gearbox motor) and see what happens when I try to push it into a small tub of dirt. Then I will proceed to make the aforementioned model in order to work out potential flaws in the drive system, power systems, etc.

As for the dirt, this isn't hardened clay. I live in Michigan, and the dirt here is very soft, and, in fact, fairly wet. It should be a good deal easier to dig into. Also, I intend to dig into an anthill, the tunnels should have made the dirt considerably looser, and, if the tunnels are big enough, I might find myself travelling through shafts, rather than digging. This is actually why I am putting pressure sensors on the robot.

Offline jkerns

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Re: Help with a mining robot
« Reply #7 on: June 05, 2014, 07:12:05 AM »
I would think you would want to use a low speed to drive the drills and use an auger type (http://www.traditionalwoodworker.com/1_4-Wood-Auger-Bit-for-Hand-Brace/productinfo/310-0600/) rather than a twist drill which are designed to turn at high speed.

As you suggest, trials would be step 1 to see what it takes to actually turn the drill.

(Note, the site above was just a random selection that had a picture of what I was looking for - not a recommendation as a source)
I get paid to play with robots - can't beat that with a stick.

http://www.ltu.edu/engineering/mechanical/bachelor-science-robotics-engineering.asp

Offline newroboticsuserTopic starter

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Re: Help with a mining robot
« Reply #8 on: June 05, 2014, 09:15:20 AM »
I was going to make my own drill and drill bit, figuring that I could use a dremel to make one out of plastic. The actual design I was going to have mirror the step drill bit design, except having it as a continuous spiral. Essentially, it was going to take that same conic shape, but spiral along the cone. Of course, it may turn out that an auger bit would be better suited, so I may turn to that.

Offline georgeecollins

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Re: Help with a mining robot
« Reply #9 on: June 10, 2014, 01:02:20 PM »
Some guys at Carnegie-Melon worked on a self burying robot.  They have some interesting ideas. 

https://www.youtube.com/watch?v=Yuw2jW5QwVQ


 


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