GRAB-E

Let's Make Robots Robots
1

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!

Wanders around and grabs your stuff

  • Actuators / output devices: Tamiya dual gearbox, 18g servo
  • Control method: automomous
  • CPU: Picaxe 28x1
  • Operating system: Picaxe basic
  • Power source: 4 AA cells
  • Sensors / input devices: none yet
  • Target environment: indoors
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/grab-e
2

Nice Tracks
I like the track design. Waiting for video.

3

LUV At first Sight

Where can i get those trax?

Also, for the butt-wheel, you could get a swivel wheel…they tend to come with a decent-enough sized wheel to go outdoors or over carpet…

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Video on build blog
I have a couple of preliminary videos on the build blog. I will post more finished videos here eventually.

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It’s this set from Tamiya. I

It’s this set from Tamiya. I think I bought mine from Amazon.com, but I’m sure you can find it elsewhere.

 

6

I haven’t tried a swivel

Thanks for the idea. I haven’t tried a swivel wheel, but I’m not sure it would work any better than the roller ball. Maybe it would.

Kinda waiting for inspiration on the rear-end of this thing. It may never change from the current config.

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Inspired by the half-track

One of the inspirations for this drive system is the half-track vehicle. In real world, human operated vehicles, half-tracks had many of the advantages of a full-tracked vehicle, but allowed a driver not trained in tracked vehicles to use a normal steering wheel.

The rear tracks were synced to the front steering wheel, and adjusted relative speed as the steering wheel was turned. For robotics application there’s no driver so this advantage goes away.

I do think the shorter track length provides an advantage in my bot, since the rear wheel swivels almost frictionlessly on smooth floor.

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Added video of a test drive.
Added video of a test drive. Looking good so far.

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New Robot Picture
Replaced the bot’s profile picture with one showing his new track configuration with the tensioner pulley.

10

I like it!
I like it!

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RE:
2 thumbs up!!!

12

I like your tracks

I like your tracks configuration,I might modify mine too :wink:

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Thanks. If you search the

Thanks. If you search the site you’ll see quite a few tracked robots with a triangular configuration. I think the popularity of WALL-E and (for those who remember) Johny 5 contribute to this. There is a practical reason for this configuration though. The shorter track base makes turning much easier.

Challenges I ran into were track tensioning and alignment.

You can see the small idler pulley I added for tensioning, which works fine. It can be adjusted a bit by loosening the mounting screws and shifting the pulley’s axle.

I ran into alignment issues when I replaced the two stock Tamiya axles (front wheels share one, rear wheels share one) with independent axles for each of the four “road wheels”. Although this axle configuration gave great ground clearance, it frequently led to the tracks falling off. I eventually gave up and went back to the stock Tamiya axles (glad I never cut them) and everything was fine.

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The idler pulley are similar

The idler pulley are similar to the one on cars and are great. I like these tracks too and the are cheap to buy. Your grippers and pan/tilt servo works fine too. Will eventualy come out with something new too. Will keep watching your progress my friend. Good job :slight_smile:

15

Nice claw

Nice claw

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Thanks. I’m working on a IR

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

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Option to the roller ball

I like the bot. Tracked vehicles rock. The video’s music makes me feel like having a sexy party as well :slight_smile: 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.

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Thanks, JAX. More to come

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’!

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Combining the sweep sensor

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.

20

Actually, the grabber only

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.