Let's Make Robots!

TankBot

Fire Fighter competition

This is my first robot. It's supposed to compete in the Penn State Abington Fire Fighter competion 2013 (missed the 2012).

 Current TankBot image

Update:

  The copper sides were a little too thin and the RC servos a little too hard to mount.  Now I've got 3/4" (probably pine - from the Home Depot cull bin) and VEX 2-wire motors.

 

  Anyone have a recommendation for a low cost but reasonably accurate quadrature encoder?  I might just go with a pair of the VEX Optical Shaft Encoders but at $20 a pair (plus shipping) that's an expensive option.  Since this is my first robot I don't have any idea what kind of resolution I'll need.  I will have decent hardware support since the Cortex-M4 has built-in hardware based Quadrature Encoder Interfaces but so far as pulses per revolution go; all I know is the VEX encoders are 90 pulses per revolution with a max rate of 1700 pulses per second.

  I've heard of using the encoders out of a mouse but the mechanics of getting everything put together, aligned, and reasonable light-tight might outweigh the cost of the VEX encoders.

 

Update on 4/18/2013

tankBot hardware complete

  I finished the hardware on time for the Penn State 2013 Fire Fighting Robot competition but the software was no where near ready.  The robot has an STM32F4Discovery board (with custom IO board) for controlling Pan and Tilt for the camera and fire extinguisher as well as full H-bridge drivers for the tank tread drive motors.  I ended up using Vex quadrature encoders; for the cost it was worth avoiding the grief of building my own.  Power is a 12V 5Ahr SLA battery.  The black box on the right is the Wandboard Dual.  It has a dual core Cortex-A9.  It reads the camera input and tells the STM32F4 board what to do via an RS-232 link.

 

Here's some better images of the custom IO control board.  PS -- I don't recommend hand soldering fine pitch SMT, it isn't easy but the three power supplies all work so it is possible...

Custom IO Control board

 

  Once I get some software written for it I hope to post some video.

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chrisc had a similar question and he learned it wasn't quite as difficult to produce as he thought.

http://letsmakerobots.com/node/32443

Scan both his page here and the blog page that covers his build. You should get some solid ideas on constructing the encoders.

If you put an axle in the middle of robot, lower than other 2, you will get less friction  ;).

I see you use a tamyia kit... the medium wheels in lower axles...

If you use the bigger wheels in the aditional middle axle, maybe solve your problem ;)

(sorry my bad english :D)

Diy tank tracks? There are a number of options. I believe the easiest is to use pairs of bike chains connected by bars of your preference using something like M3 bolts and nuts. You may need to add rubber to your connectors to make sure you have traction on all of the surfaces you want traction on.

I've been looking at Do-It-Yourself tank tracks online but I'm not sure if I can manage it in the small amount of space I have.  The max size of the 'bot is 12.5 " x 12.5" x 12.5" and I'm already 10" wide with just the body.

I was responding to this on my phone, you would need to upgrade your rolling hardware. The DIY tracks can have their width controlled by the length of the connector that you use.

This is the style I am thinking of: http://letsmakerobots.com/node/21908

`Looks like the Vex tracks may cost the same or more than DIY with bicycle chain.  What do people use for the rolling hardware?  One nasty problem I had with the tracks I used was it kept coming off the rollers.

nice body I like it!

 

Nice job especially on the body.  I reminds me of a miniature version of the sand crawlers from Star Wars.  - Hal (kingart3)

Thanks.  I had a steel and a copper plate left over from another project and a tank-like robot seemed like a better first robot than a walker like the AT-AT (less likely to fall over).  Although I think an AT-AT that can fit into a 12" x 12" x 12" cube will be my next robot.  That's part of the reason for the dual CPU approach.  The Cortex-M4 is for handling the body with the Cortex-A8 handling the "thinking".  My goal is to have the A8 tell the M4 "Go this direction this many units" and such.  That way all the details about _how_ to move stay in the M4.