Let's Make Robots!

GRAB-E

Wanders around and grabs your stuff

Update 2011-10-06: Melty, melty

Poor GRAB-E. His foolish creator left him in the garage for a few days after taking him home from a trip. The hot summer sun melted his polymorph sonar bracket and parts of this tracks.

Last night I got around to carefully picking off the slagged polymorph. I remounted the sonar with hot glue for now. New tracks just arrived this afternoon, so hopefully I can fit him up today.

I also tried out some new NiZn batteries in GRAB-E. They are AA sized and have a nominal voltage of 1.6V. Fully charged, they are about 1.8V. Since I used a LDO voltage regulator and a 4xAA battery pack, these work out great. Now GRAB-E starts off at 7.2V instead of 6V, and runs for a lot longer. Also, since the motors run directly from the batteries, he should really kick it into high gear now!

While testing out the new batteries with the old melted tracks removed, I noticed a distinct wobble in one of the drive sprockets. I tried to unbend it, but I probably just made it worse. Ideally, I should take him all apart and try to bang the shaft straight again. Realistically, I might not see much of an improvement for all that work. I'll try the new tracks and see if he runs OK.

Update 2011-07-13: Integrated IR circuit and updated code

I moved the interface circuitry from a breadboard to one of those little circular protoboards from Radio Shack. It's only about 5/8th of an inch (or 1.5cm) in diameter. Getting everything on was a tight fit, but now it is hot glued to the little wooden block behind his sonar. 

As usual, check GRAB-E's build blog for more detail. I'll add new pictures and video soon.

Update 2010-09-30: New Head

I replaced GRAB-E's head and reduced my servo count by one by combining his sonar sweep with his claw. Check GRAB-E's  build blog for more detail.

Update 2010-09-12: The CLAW!!!!

GRAB-E finally gets some equipment to match his moniker.

Update 2010-02-04: Uploaded new primary image.

Still building, but here is GRAB-E. So-named because of the WALL-E style track configuration and the fact that I will build my first gripper for this bot.

You can also view the build blog for this bot.

I added a video showing GRAB-E's manueverability.

GRAB-E was originally somewhat of a distraction from my more complex plans for the Mr. Basic Challenge 2, which never really got finished (but will, someday!). I was up at 4 AM and I needed to do something fun that didn't involve load fabrication noises from the basement. 

CHASSIS

Based on a Tamiya Remote Control Robot Construction Set. I sacraficed my earlier (incredibly lame) robot for this one. I've reconfigured the tracks from the original to a triangular set up with the drive sprocket at the top and two idlers below. You can see the track setup in the main picture.

Dragging behind an Arexx roller wheel purchased from DAGU. This rear wheel works great, but definitely limits GRAB-E to an indoor, smooth floor environment. I'd be interested to hear ideas on a different approach that would let me take better advantage of the tracks and open this bot up for a greater variety of terrain.

The advantage of this set up is manuverability. The shorter track length makes turning easier.

 

BRAINS

Originally I sacraficed the brains from my Start Here Robot. Those brains eventually when to Robot Leader, and I have nowI built a new set of brains based on the Picaxe-40x2 loaded on the Picaxe-40/28 protoboard. Stacked beneath the protoboard is a DAGU Mr Basic motor controller board. The open space on that board has power regulation, a power switch, servo interfaces, etc.

SENSORS

I added an SRF05 sweeping ultrasonic range finder using a home-made pan-tilt based on the DAGU sensor brackets.

GRABBER

I finally built the grabber from which the bot gets his name. It is based on a single servo, with a plastic gear mounted where the servo horn should be. The gear is coupled with an orange piece of plastic that is actually a throw-away bit from a Canon ink cartridge. the driven gear is meshed with an identical one (also mounted to an orange claw bit). The second gear/claw is held on with a simple metal frame I banged together and hot glued to the servo. I hope to improve this setup later.

The whole mess is in turn hot glued to another DAGU sensor mount forming GRAB-E's wrist. I modified a DAGU sensor mount to work as the up/down control for the grabber arm. Check the build blog for more info on the sensor mount mod.

Later I may add pressure and position sensors so GRAB-E can be more precise. For now, I'm happy I have a decent mechanical design that lets him grab stuff.

More coming soon!

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why dont you put the electronicts on top of the gear motors so it does not need a caster

I think he'd be too top-heavy if I did that, but thanks for the suggestion.

Like the new avatar, very brooksware2000 lol !

Nice Bot,
Do you have details/pictures of the building of the claw? Where did you get the gears?  I'm interested in creating a claw too, and am debating some of the variables.  For example, I have a toy claw.

The joints are pretty nice, they'll keep the fingers parallel with one another through the whole grip.  I do like your solution too - especially the re-purposing printer-ink parts !   

I found this thing in the garbage (who would have thrown it away!) and will begin dissecting it for interfacing with a servo.

To the LAB !

Hey Grog,

That's a really nice toy claw. I've got a couple toy claws I would like to use, but they don't have that parallel jaw feature. I'll have to look for a couple like that. I could really use that for Robot Leader (poor guy still has no hands!).

GRAB-E's grabber is dead simple. I had a set of plastic gears lying around. I think I ordered them from the Electronic Goldmine. I just superglued the ink cartridge parts to the gears. One gear is mounted right where the servo horn goes and attached with a screw.

The second claw is a little tougher. I banged together a bracket from some scrap metal. It wraps around the servo, but has a little space near the top where the other claw is. A machine screw is inserted upwards through a hole in the bracket. Then I slide the bracket and screw assembly onto the servo. The other gear-claw assembly is mounted on the machine screw and attached with a small nut. I had to set the bracket carefully for the gears to mesh. It is only held on with hot glue.

Honestly, it was one of those temporary prototyping ideas that never got made into a nicer finished product. I may find that the gears slip and that I need to make a better bracket. Now that I have some experience with polymorph, I may refabricate the bracket for a cleaner, more precise result. That probably won't happen unless the current one misbehaves. I'm lazy that way. ; j

Combining the sweep sensor and gripper sounds like a great way to solve the problem.   will you need to extend your sweep comfort zone to account for the gripper sweeping too?   I love the repurposing on the toner cartidge tabs.

Actually, the grabber only has one degree of freedom (up and down), plus open and close of course.  The sonar has two degrees of freedom (sweep and up/down).

I'll need to use the sonar to guide GRAB-E so he lines up with whatever he wants to grab.

I like the bot. Tracked vehicles rock. The video's music makes me feel like having a sexy party as well :) Anyhow, have you considered using a tailwheel assembly from an RC airplane as a replacement? There are many options as far as size, caster, wheels, etc. While not necessarily cheap there's something out there for almost any application.

Thanks, JAX. More to come for GRAB-E soon!

For the moment his steel roller in the back is doing fine. I really want to focus on getting the IR detector working and get GRAB-E grabbin'!

Nice claw

Thanks. I'm working on a IR object detector, so he'll know when something is within his grasp.