Posts Tagged Mini Sumo

Some Random Stuff

Posted by Roko in Mini Sumo v6, Quadruped, Robotics on May 9th, 2009

GPS Module and Antenna

U-Blox GPS and Satantel Antenna

One of my friends working on a GPS project of his own managed to aquire some Sarantel Helical antennas, and got some for me as well. I’m planning on using them with the U-blox GPS module I have had sitting around. (I originally bought the GPS module for a MUAV autopilot I’ve been slowly designing, but when I got busy with work it got put aside and technology outpaced my design. For the MUAV autopilot I’m now intending on using a smaller, lighter GPS module which has freed up this one for service on my Quadruped). I’m still mulling around on choosing an LNA to throw in between the radio and antenna to improve sensitivity, so the PCB design is stalled until I make a selection.

Four Legs in progress 2

Teaser Photo

Although the GPS is “technically” able to attain a GPS lock indoors according to the literature, I’m not going to count on that. The camera will be used for indoor navigation and world modeling (I’ll post more on the progress of that later), while the GPS will be used primarily for outdoors navigation. The main reason for this is I’m thinking of having a go at the Robo Magellan competition put on by the Seattle Robotics Society. Although for the general flat environment a small walker is at a huge speed disadvantage to the larger wheeled or tracked rovers that typically enter, I’m more interested in the technical challenge of designing a robust and adaptive walking/navigation algorithm for the robot than winning.

Populated Mobo

Mini Sumo Brain

As a bit of an unrelated note, here’s a picture of the populated circuit board for my mini sumo. Now that there’s no pressing deadline to get the robot working, I’ll have more time to fiddle with this board and get FreeRTOS up and running on the LPC2138 to manage the data and computational requirements of some of the more complicated sensors I’m throwing into this sumo robot for no other reason than “because I thought it would be a good technical challenge”

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2009 Western Canadian Robot Games I

Posted by Roko in Mini Sumo v6, Robotics on May 5th, 2009

Super-Secret-Backup-Plan-1

The HC12 Motor Controller Board modified as a sumo controller

I spent the second half of last week scrambling to get my mini sumo robot, 1.21 Gw into a working condition for the robot games. I populated the circuit boards mentioned in an earlier post but as I grew low on time I decided to put those aside for this year. Instead of trying to teach myself a new architecture (LPC2138), I decided to concentrate on programming the robot using a board I was familiar with, my HC12 based motor controller design. (This was the prototype motor controller for my Quadruped walker, so I had some base code already written for it, which went a long way towards getting my sumo robot programmed in a little over a day)

May 2009 Weigh In

331 Grams!

I made the decision to forgo edge sensors for this competition, and instead chose to make the robot as aggressive as possible, the theory being that if I push the  opposing robot off the edge before my robot gets to the edge, I won’t need edge sensors. In the end, I managed to get a working robot, measuring 98mm wide by 97mm  long, and weighing in at only 331 grams!.After I finish the actual controller board I intend to use on this robot, I’ll have to make some weights to bring it closer to the 500 gram limit.

In the end, I placed first in the advanced mini sumo category, though I had some good competition! For more videos, check out the WCRS website. I will try to post my own pictures and videos when I get a chance.

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Mini Sumo PCBs…

Posted by Roko in Mini Sumo v6, Robotics on April 28th, 2009

BlankPCB

Bare PCBs

After
MockUpPCB

Fitting the PCB in the body...

a rushed PCB design marathon, I got my PCBs in last week, built by the good folks at APCircuits. The stencil came in shortly after. Since I made the PCBs into a panel, I had to cut them appart and file down the edges so that it would fit in the chassis. Overall the PCBs turned out nicely. I built them up and can sucessfully load code into the LPC2138. (No pictures of the completed circuit board yet). Things are comming togethor nicely.

You’ll also notice on the silk screen that I have given this robot a more creative name than Mini Sumo Version 6. I now call it “1.21Gw,” pronounced, of course, much as Doc Brown pronounced it in the timeless classic (no pun intended) “Back to the Future”

Now to finish it up and write some basic code for the robot games this weekend.

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It’s not a robot until it looks like a robot.

Posted by Roko in Mini Sumo v6, Robotics on April 15th, 2009

Flycutting the Delrin Body

Flycutting the outside of the Chassis

The long weekend was a busy one with lots of progress made on the mini sumo. I sat down in front of the mill, and machined the robot’s body out of a single piece of 1″ thick Delrin, a task requiring a lot of care to not mess up, as one slip up has the potential to ruin the entire part, and hours of work.All in all, I think it turned out very well. Delrin machines very well, although does require a vacuum cleaner close by to continually clean up all the chips that accumulate, especially considering how much material I removed….

I also spun the two aluminum motor mounts, and cut the stainless steel base plate that seal off the bottom of the body. Still a lot of work to do on the chassis, and the circuit design is progressing slowly.. Now it’s just a race against time to get the PCBs made, circuits debugged, and a rudimentary program written up to get the robot running for the games. It’ll be tight, but I think It will be ready…

Here are some additional pictures…

Delrin Body Bottom

Bottom view of the Chassis

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Delrin Body Front

Front view, with motor mounts and hub vissible

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Milling the inside of the Delrin Body

Milling out the inside of the Chassis, where the electronics and batteries will go

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Adventures in Mold Making Part II

Posted by Roko in Mini Sumo v6, Robotics on April 8th, 2009

TireInMold

Removing the prototype tire from the mold

After
FirstTire

The first tire.

16 painful-to-wait hours, I cracked open the mold to check out the first prototype tire. It turned out very nicely, and much better than my previous adventures so many years ago. (Maybe when i get a chance I’ll dig up some of my old stuff to use as a comparison).

The traction on these tires is amazing, and the dark blue colour looks cool, however I think I’ll use a bit less pigment next time. The tricky part will be maintaining a consistent amount of pigment, since I only have one tire mold and will have to mix up a new batch for each tire I make. Making another mold would take valuable time away that I need to work on the chassis and electronics design if I’m to have any chance of finishing in time for the WCRG…

Note the air bubble that caused a missing piece in the tire.. Since this was a prototype tire that I plan to rip apart to test the strength, I wasn’t too concerned about fixing that part while molding it.

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Adventures in Mold Making Part I

Posted by Roko in Mini Sumo v6, Robotics on April 7th, 2009

DelrinBlank

Somewhere in this piece of Delrin is a mini-sumo robot chassis.

It’s been a while since my last post, but I’ve been working away hard at designing and a little bit of machining for my Mini Sumo. It’s proving to be quite a challenge to fit all the electronics and sensors I want into the small package of a mini sumo robot only 25mm tall, but I think I’ve figured out how to shoe-horn the electronics in there.

I’m planning to do some fairly sophisticated sensors, but that’s a topic for another day, and likely after the games as I likely have to run a temporary brain for this competition as time is too tight to get a PCB turn.

Tire Mold

The finished tire mold

I have made decent headway on the chassis, having made more wheel blanks, and made a mold so that I can cast my own polyurethane tires. The mold itself is made from Delrin on the mill, held togethor by four screws, and kept in alignment with 6 dowel pins. The center slug was spun on a lathe, and forms the bottom of the mold, as well as a means to seat the wheel directly in the center of the mold. A top plate from scrap polycarbonate is screwed on to keep the top finish of the wheel nice.

Delrin is a really nice material to work with on a hobby mill and lathe, and it was relatively easy if somewhat time consuming to bore out the 25mm diameter hole for the robot.

MoldRelease2

Brushing on the Mold Release

6 or 7 years ago was the last time I cast polyurethane for sumo tires, I reckon, so I figured what I had lying around was no longer good. A bunch has changed since then, and a stop to a local mold making shop with some samples had me settled on Smooth-On Reoflex 30.  Other people have used various Reoflex durometers for sumo robot tires as well. Feeling in a spendy mood, I also decided to buy some blue pigment.

Excitedly, at the end of the work day I got home with the polyurethane in it’s shiny box, which I’d bought over lunch hour, and prepared the mold. After collecting all the things I would need to cast my tires, I found that the really Old AIrbrus lying around wouldn’t spray the mold release agent anymore, so I cheated and used a brush instead. After waiting for the mold release to dry, I clamped the mold pieces together, popped in a wheel, and started mixing some polyurethane.

MoldReady

Ready to pour the polyurethane!

This new stuff works better than what I’d used previously, and was less viscous and as such did not get as many air bubbles trapped in it while mixing. An added benefit was that I could use some over-sized syringes I had lying from an old ink-jet cartridge re-filling kit.

A word of caution when using pigment for polyurethane, however: The “SoStrong” pigment.. Is, just as the name would imply, oddly, So Strong. I used a few drops, which was a few drops too many. The end result was a very dark mix. But, as this is a prototype tire that I plan to rip appart to test strength, I wasn’t too concerned.

Now the tire is sitting in the mold. With a 16 hour de-molding time, It should be ready tomorrow roughly around lunch… We shall see how it turned out then.

For now, here are some other links you may find useful with regards to polyurethane sumo tires:

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Mini Sumo Motor Mounts

Posted by Roko in Mini Sumo v6, Robotics on March 26th, 2009

Well, it’s been a while since I’ve updated, and I have gotten a little bit of work done on the robots in between ice diving adventures, and working on the Jeep. Most of the progress made has been playing with software (Investigating webcams and OpenCV for Spyder’s machine vision) and hardware design (PCB layouts for Spyder’s many circuits.)

Motor Mount 4

Motor Mount Prototype

Today
Motor Mount 3

Motor Mount Prototype

, however, I sat down and got some machining work done for my mini sumo. I was wrestling (no pun intended) with the idea of how to mount the motors, and eventually decided to make a flanged sleeve for the motor to fit inside, which will then be securly attatched to the frame of the robot. The first attempt turned out pretty good, although not quite perfetct, as I didn’t properly square it off in one of the steps. It’s useable, but I’ll have to decide wether or not I want to make another one.

So, things are slowly comming a long. I’m afraid I won’t have all the circuitry I wanted to put into the mini sumo done in time for the robot games (chiefly goverened by the long lead time for budget PCB’s from batchPCB), but hopefully I can at least get something that will run arount the ring. I suppose as a backup, I do have my H-Bridge prototype board I could use to control it.. Complete with high-efficiency H-Bridge, and a powerful little 9s12 to control it all… Hmm..

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Mini Sumo Beginnings

Posted by Roko in Mini Sumo v6 on February 3rd, 2009

As with many projects, a mini sumo has been several years in the making, and has undergone several design revisions without actually having time to begin construction. But, finally, I took a bit of a break from the quadruped to start work on a mini sumo robot in the past couple days.

Aluminum Wheel Stock sized

Start of a wheel

I had some round aluminum stock sitting around, and felt like playing around with the lathe. I got my trusty hack-saw out, cut off a chunk of aluminum, chucked it up on the lathe, and started spinning. Over the course of one evening, I came up with a basic wheel and hub assembly to go with the Maxon 17:1 gear motors I’ve had lying around for almost a year now, waiting for a sumo robot to be built around them. This is the same Maxon motor many people use, and I had to contend with the same issue, that the motor length itself is half the maximum width of a mini sumo robot (About 50mm). This called for making a hollow wheel that would slide over the motor.

I made a two piece assembly, with a hub that is attached to the motor with a set screw, and a wheel that is attached to the hub with several 2-56 screws.

Wheel Bore Action Shot sized

Boring in Action

Overall, the boring went well on the lathe, but was definately a learning experience. The process itself was tedious, starting with drilling out a center hole using drill bits of incremental sizes until I had a center hole large enough to fit the boring tool, then slowly boring out a 21mm depth, 0.1-0.2mm at a time, slowing down as I approached the desired tolerance.

The tool itself chatters easily if you’re not careful, but I managed to produce a mostly clean bore. I’ll have to experiment/research a bit more on the best chip rates for turning aluminum stock…

Making the inner hub itself was easy to do, simply turning down the outside of a piece of aluminum, then using a couple drill bits to center drill a hole to about 2.85mm, then using a reamer to finish the center hole at a nice, clean 3mm to fit the shaft. A 4-40 set screw fit nicely, though I did have to file down a fraction of a millimeter that was sticking out from the hub itself, as that part of the hub fit with close tolerance into the wheel itself.

Wheel Assembly Parts sized

Prototype Wheel Parts

[caption id="" align="alignright" width="150" caption="Prototype Wheel Assembly"]Wheel Assembly Assembled sized[/caption]Using a milling machine to precisely drill the holes that I would then use to tap and mount the actual wheel to the hub helped keep everything nice and accurate. Once finished, the wheel and hub aligned very well, and I had a completed wheel assembly.. Now to finish the other wheel, make a tire mold, mold the tires, mount the motors to a chassis, and make a brain for it all.. Hopefully I can have a basic robot ready in time for this year’s Robot Games.

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Upcoming 2009 IEEE Robot Games

Posted by Roko in Robotics on February 2nd, 2009

The 2009 IEEE/WCRG Robot games have been announced for May 9th, 2009. I used to be an avid participant, but first school and then work travel got in the way and as such I’ve only managed to make it out once in the past few year.

This year, I’m hoping to have a mini-sumo ready in time, one that I’ve been designing in the back of my head for several months (years?) now. I’ve had some tiny Maxon motors sitting around that I bought a year ago with the hopes of finding time to start this robot, and today took a break from the quadruped to finally start machining the wheels. I’ll try and post details later.

Anyways, if you can make it out to Calgary for May 9th, it’s definatley worth checking out the Robot Games. If you have spare time, make a robot to compete! It doesn’t have to be perfect, it’s more fun building a robot than winning…

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