Let's Make Robots!

Moo Bot v1.1

Navigate via sonor sensor

Moobot Update 3, Oct. 1, 2012 (Version 1.12)

I'm waiting on a mail order for a bunch of the electronics that will go into OddBot's motor controllers, but in the meantime I attempted to finish the "body" work for the bot (still have a bit more to go) as well as to begin to write some of the code for the robot using an Arduino-simulated version.

That included making a small robot head that would contain the Ping ultrasonic distance sensor, two LED arrays to indicate "happiness" and "sadness" and, just for the heck of it (not even sure what I'm going to use it for yet), a button -- er, tri-color LED -- nose. The head is also able to rotate using a small servo motor. In total, the head will rotate to calculate the direction in which it is supposed to move.  

I posted a video of the simulated robot, which should hopefully show the direction I'm attempting to go in. 

 

Moobot Update 2, Sept. 25, 2012 (Version 1.11)

 

Not much of an update to the robot itself, other than I finely crafted a lovely cardboard remote control for the Moobot strictly for the purposes of putting a demo video together of the mechnical nature of the Moobot. Admittedly it was also just pure fun to actually get the thing moving a bit. I uploaded the video to this project page. Enjoy, or mock me, at your leisure. Both are welcome (I have a pretty good sense of humor!)

 

Moobot Update 1, Sept. 21, 2012 (Version 1.1)

To the best of my knowledge so far, I have overcome the problem of having proper wheel mounts for the drill motors by hack-sawing the hell out of the original drill chucks that came with the 18V Harbor Freight drills I had purchased for the purposes of gutting their motors. Long story short, I hack sawed the plastic cover of the drill chucks to reveal their inner metal parts, which turned out to be a suitable  motor-to-wheel mount, so long as I torqued the crap out of the drill chucks to hold the screw axels I'm using for the front wheels.

I've made quite a lot of overall structural/mechanical progress since making the change. It turns out that the thing definitely drives, after testing it by directly connecting the drill batteries that came with the Harbor Freight drills to the terminals on the motors. Like others have suggested, it almost drives TOO much, haha. The motors very well may be overkill if the motor controllers and microcontroller can't tame this thing a bit.

As you may be able to see in the photo above, I did have to drill in some "grub" screws into the driving wheel in order to get better traction on the tank tracks.

Thanks to this recent post by Oddbot I believe I'm going to be able to soon hand-make the motor controllers that will ultimately tie the Harbor Freight motors to an Arduino. I have been using the program Fritzing to redesign Oddbot's circuit such that I can print out some custom PCB templates. In turn, the controllers will connect to the Arduino, which will connect to an ultrasonic distance sensor, which I will use to write a wall-avoiding AI for the bot. Yet the closer I get to a working bot, the more ideas I have for extra sensors, remote control, etc....just trying to keep it as simple as possible for now, as I know even getting a basic working robot out of this design will be some work.

After connecting the motors to the wheels, I also made the motor mounts with some scrap hobby wood and some plumbing pipe clamps, which secure the motors to the chasis:

And lastly at this point, I'm attempting to cut and fit the outer shell pieces, which I have decided will also house the microcontroller and the motor controllers once complete:

 

At this point, it's at least starting to look like a robot!  I'll post some vids of me demoing the speed of this thing at some point tomorrow (or soon after ) to demo the power this thing has.

Could be interesting trying to harness that power appropriately :)

The premise of the robot:

I was inspired by armando96's robot, which he called the AATV, and have since made an effort to the best of my ability to duplicate his build in a new robot, which I've dubbed the Moo Bot ("moo," because my last name is "Mumau," pronounced "moo-mah"). 

My general design for the robot is something like this:

I started by building the PVC tank tracks as armando96 described in this tutorial. I did not have rollerblade wheels like the kind that armando used, but I was able to find some relatively cheap caster wheels at my local Lowes (which is where I got most of the materials for my robot). 

I decided to use some weld steel for the chassis/frame. The wheels are mounted on the bottom with some wooden dowls that I drilled a center hole through.

The top of the chassis will hold the two Harbor Freight 17v drill motors, which I have tweaked using the "o-ring" hacked described in this tutorial from Dale's Homemade Robots. I plan to using plumbing pipe clamps to mount the drill, with some dowls/scrap wood as the base for the drills to give them some lift.

Altogether, the thing would look something like this from the top-down view.

The main mechanical problem I've had with building this bot is with the wheel hubs. I've tried a great many of different designs, but they all seem to fail. I'm hoping by posting my design here that someone can offer some help or ideas. At this point, I believe I may have to try to find someone who works at a machine shop to create some custom couplings with set screws.

Ultimately, I plan to use the Arduino to be the "brains" for this thing, and I'll have to devise/buy some sort of motor controller for the thing. I hope to make it autonomous by using a sonor-based sensor, which I have already purchased and tinkered with (seems to work fine). 

I plan to use this robot to test sensors and programming techniques for the Arduino. 

 

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I was looking at your motor/wheel mounts, and, was wondering what the outside diamiter of the strpped down chuck is, from the looks of the pictures, you might be able to mount a bering on the chucks, and cut a hole in the sides that fits the outside of the bering to support the axel a little better, I think with time, the stress being put on the motor assembly might tear the entire assembly to bits. Just a thought.

Very well built robot by the way :)

Aaaahaaa!!! 

L m R = Smart thinking, it's an instant standard from here on! :D

What more can I say at the moment? :) Glad to see things are moving for you.

Yeah, better traction would help a lot, and longer cords for the remote :-) Perhaps instead of cut-in-half vinyl tubing, use the full pieces, simply drill a hole through and tighten the bolt enough that it pops through one layer and hides it self inside the tube

It's quite noisy, definitely not a ninja stealth bot!

 

The YouTube video doesn't even quite do justice to the noise level, haha. It's pretty dang loud. Noise level wasn't really one of my design "requirements" but I may think about some alternatives. In the meantime, it's kind of like a flamboyantly happy robot. Like, "Hey, guys! I'm HERRREEEEEEEEEEEE!!!!! And I'm FABULOUS!!!!"

The remote is temporary. Eventually this thing will be autonomous (I hope!)

A lot of torque. I was surprised that it didn't put deeper gouges in that nice hardwood floors. :-)

With that in mind, would it have been better to use pieces of heavy rubber hose instead of the plastic pipe to make the treads? Might give less slippage too.

Yeah, my girlfriend granted me permission one time to run the ol' MooBot across our hardwoods! She even volunteered to be camera girl so I could be the driver more properly. (In any case, we rent, so I guess ultimately it's our landlord's problem!)

I agree about the hose. The PVC piping for the tracks does tend to slip. I also have been thinking about using some of that "Plasti Dip" stuff that you can get at the hardware store on the edges of the tracks. Or maybe even just some hot glue on the edges, as someone had suggested for armando's AATV bot. Decisions, decisions...

The excessive torque is a problem. I'm hoping that with the Arduino's PWM, in combination with OddBot's motor controllers, I don't always have to power them at 18V. That "remote controller" is just some momentary switches directly connecting the batteries to the motors, so it's a wee bit excessive. 

Mechanics aside, hopefully I'll soon get to the fun part -- the electronics. Just waiting on a whole bunch of components to arrive in the mail so I can assemble the motor controllers and start to hook it into the Arduino. I'll probably get a jump start on the programming in the mean time (i.e. the fun part, haha). 

I was thinking of the heavy rubber air hose like they use on pneumatic air tools. Besides eBay, you can probably also find it at your local hardware store sold in any length you want. You want stiff rubber, but not plastic for the treads to give you good friction.

Might also cut down on some of the noise.

 

Those wheels look like the ones used on skateboards. Do they have bearings in them? I used skateboard bearings on my Shrödinger robot.

Yeah I actually switched the two back wheels to rollerblade wheels, which have ball bearings in them. My previous method of like "screw through wood dowel' bearings wasn't loose enough; the motors simply locked up. And as I found out, that turns the entire thing into an arc welder, haha (the motors consume an ungodly amount of power when they're stalled; I have a small welt scar on my hand, as well as a few completely melted alligator clips, now to prove it!)

I see. BTW, vinyl was mentioned, but I was thinking oif actual rubber.

A heavy-duty rubber hose similar to this: http://i3.ebayimg.com/05/i/000/f4/2f/0643_1.JPG

should be available from your local hardware store at so much per foot price (or so much per meter or cm. in other parts of the world).