Older blog entries for ROB.T. (starting at number 30)

Here is a better summary of where I'm at with my project. The source is an email to the TCRG list -

>Bruce wrote:

> ps -- Rob, how is Robocities coming along? If you need some help, the > group is ready to step up and provide whatever you need. Right group :?) >

Robocities is making me cry. Major engineering hurdles, no time. Maybe the group could take my wife and kids for a few weeks? :-)

Seriously folks -

Bruce I'm looking at constructing not so much a city but a ziggurat, kind of like a square tower of Babel out of pink foamular(tm) insulation foam (how strange is that). Unfortunately planning out an entire city would be just too hard for a protocity, so if this structure is too weird for the Science Museum, hey I understand.

What I'll need is a 11' x 11' space, about 11' high. I'll need another 10' x 10' space to put the pre-build material. These dimensions can be scaled down as needed.

What we're looking at, with as many corners cut as I could manage, is 4 robots; 1 to place bricks, 1 to deliver bricks, 1 to deliver roof/floor tiles, 1 to deliver ramps. The walls will be 16" high making each level 17" high with the tiles. The roof tiles are approximately 32" x 32", the individual bricks are 8" x 4" x 8". 7 levels total with a 32" x 32" spot on the top of the building for the robots to sit when the structure is complete. The walls will actually be laid as "hallways" or "tunnels" that run through the structure; I currently have no plan for building a closing wall around these tunnels so you'll be able to see through the ziggurat structure.

Engineering hurdles-

The whole system is based on the brick laying robot because that is the robot that will move the least. One challenge was to determine if this robot would give direction, or if a computer would control the show. Having the robot give direction to the other robots was really attractive because then I wouldn't have to program any other systems like a computer. But, because I have some calibration considerations and yet I don't want to lug a computer around, I've decided to program a PDA to do the decision making in an extremely centralized method. I expect to change this in future upgrades (famous last words).

I'm trying to create an initial system with the least complexity possible to insure completion by the deadline. This means I'll be doing a lot of experimenting in the future weeks and then adding hardware/software as needed. For example initially I want to see if dead-reckoning is enough to get the protocity built, then I'll add an accelerometer, compass, etc. What I don't want to do is add stuff that I think I'll need and increasing the complexity.

Mechanically, I finally built the arm design I like the most for the brick layer, wired up the base, and I'm adding sensors and getting ready to program. This is the first robot, but don't panic yet (let me do the panicking here), this is the hard one, the other three robots will be significantly easier to build and program after this one is done.

Another problem is preparing the bricks and the tiles, and how to configure them as pre-build material that's accessible to the robots. This will probably be the last thing I work on, which means this is probably the thing that's going to get skipped and I get to hand my robots material by hand (bummer). Oh and I doubt the robots will have enough battery power to complete the structure, so I'll need to swap out the batteries without having the system lose it's place. Charging the robots is currently not an option since this will increase the complexity.

Rapid-Prototyping Boards have been a really big help, but there are still some flaws that are being worked out like my motor drivers stack on the motor interface board poorly.

Lastly, I was just relating to Jeff Sampson earlier that I don't think I've ever completed a robotics project to this degree, so some funny stuff is coming up like what software component to program first.

To sum it up - overall I would say I'm about 6 months behind but progressing nicely.


OK, 1 month to go to meet the St. Paul Science Museum/Shapiro deadline for having my robots build the first proto - robocity. I've been working like a phene, but chances are I'm not going to meet the Nov 8th deadline. Right now I'm about a month behind and I really didn't understand how much infrastructure had to be in place - it's amazing. I could put 2 or 3 guys to work and still not make it.

But that is neither here nor there, I've got a month, I've found an arm design I like for the first robot so I've started throwing the electronics together and programming it. I've got a real good idea of what needs to be done and what corners to cut. and the game ain't over.

3 Sep 2003 (updated 3 Sep 2003 at 20:36 UTC) »

So I've been soldering boards for the last month and I'm about 85-90% done. Here's a picture (See the 9/03/2003 picture on the right). OK, I might have taken a little-bit of time and upgraded my computer system to 2.4GHz P4 on an 800 MHz bus with 1Gig of RAM, 6 - USB 2.0 ports and an Ethernet port on board, a 7200 RPM 160Gig HD, DVD Rom Burner, WinTV, Windows and Office XP professional (yes, I $upport the empire), etc. - I kept my Matrox video card with the dual monitors. I'm pretty happy with it. Now understand, I didn't WANT to build this computer system, I HAD to build it - to support the robotics GUI for the Robocities ;-).

Speaking of Robocities - this month I want to get the first set of city-building robots done and build the first proto-city. I also have to test all boards I've put together. My goal is to have something to show for our next TCRG robotics meeting.

5 Aug 2003 (updated 5 Aug 2003 at 15:43 UTC) »

First of all, I brought the mechanically completed (no brain yet) bricklayer to my July TCRG robot meeting. It looks like I'll have to redesign the arm extension, but this design works pretty well. The Robocities concept is still a go.

The boards are done and on their way from Bulgaria. I just ordered all the parts for the boards, and all the motors I think I'll need. The only kicker is that one of the parts - the accelerometer, isn't due to ship until 3 days before I'm suppose to have this project finished and tested, so that's no good.

I've got some little sub projects, like making a brass cutter and an Acrylic cutter that I want to build before I build the next onslaught of robots. This sounds like a distraction, but one of my objectives for this project is to create Infrastructure tools that will allow me to build better robots faster. So that's what I'm doing today.

The ``true test'' of my faith in my robotics abilities has finally arrived.

A little background - I've been working on the Robocities concept (the concept of having multiple little robots construct a place they can ``call their own'' out of foam) and I have created a prototype bricklayer that will be a little slow but should work. The goal of this project is to introduce a book and a web page that will inspire advanced robotics hobbyists to build their own cities.

With this in mind I've opted to order the full complement of prototype boards for 10 controller sets - a total cost of $4,500 - which, in addition to some of the boards I already have, will be used to control 7 robots 4 infrastructure projects, and 1 user/computer interface. I estimate I'll need about another $2,000 to begin to raise the cities and to complete the infrastructure projects.

Normally I would simply stretch this out over the next 3 years or so and gradually get it done. But the taxes on our new home just shot up another $350 a month, and my monthly cash outlay has now exceeded my cash intake. So now I have an extreme need to make more money, which frankly, I doubt I'm going to get through mobile robotics at this time. So that means I'm going to have to either work two jobs, or get a better job, either way robotics time is going to get shelved fairly soon.

So this is it. I've opted to extend myself as far as I can go financially to get this robotics project together and out to the community, and after this, I don't know.

5 Jun 2003 (updated 7 Jun 2003 at 04:22 UTC) »

OK, college is finally over (after 16 years) and I've got me one of them there pieces of paper. So now the question is do I pursue robotics or do I get a real job (complete with career)? After talking to my wife, I've determined that I can always get a real job later, and for now I will focus on robotics.

This is good because I made one of those napkin contract (lower left corner - I might have been drinking...) with Bruce Shapiro, a guy from my robotics club with deep affiliations with our local Science Museum, indicating that if I complete my Robocities concept and he will talk to the science museum people and find a space for my creation.

I consider this a no-brainer since I was going to complete this project anyway and even go so far as to write about it.

I've already secured a lot of the proto-type boards I want to use and was working on the mechanical side of thing - when disaster struck. A little detail I ignored - commonly referred to as ``physics'' - informed me that the way I was planning to build walls would produced more torque on a particular motor then it was capable of handling.

Needless to say my carefully laid plans have been dashed on the rocks below.

So for the next day or two I'll be working on ``plan B'' which I hope works because ``plan C'' will reduce my robot's efficiency roughly in half.

So there it is folks, the nitty-gritty of robot- building in action.

I have two weeks left of school for my CS degree and then it's over ...

My second wave of boards are on their way from Olimex. It'll take me about a month to test them.

Predecessor is experiencing an ``operational pause'' due to low funds (external factors sucked my robot budget dry). I'm really not in the mood to switch projects in mid stream, but hey, finances are finances. I take some comfort in the knowledge that my other two major projects integrate nicely with the technologies developed for Predecessor. So I picked one of the other projects to work on with the remainder of this years funds - Robocities.

Robocities is a pretty cool concept - robots build a city- like structure using foam blocks. I did some extensive work on this concept about three years ago, but lost interest when my class load increased. Kept in the back of my mind as one of the ``Big Three'' projects that I want to write about, it will make a nice transitional project for intermediate hobbyists and a good collective project for universities who work on ``swarm'' robotics.

Since Robocities shares the same technologies as Predecessor, a tremendous amount of work is already done. Another plus is I can prove the concept by building one robot - three machines gets the whole thing up and going. I've ordered the motors for those machines, but I'm still developing the sensor set I'll need to make the project work.

In other news it looks like my robotics group TCRG is experiencing some frustration at low turnout and project stalls. I'm generally unable to attend meeting - lately because of school - but I should be at the next one (in a month) to share my project construction experiences. Maybe I'll even have a small Robocity Robot up and running.

I still need to order the parts, but I just sent the PCB order for the second and hopefully last order before I order all the boards for the platform (took long enough). I decided I'm not ready to solidify the design so I'll be ordering more prototyping boards instead of developing a new task-specific board for the leg.

I also bought 2 more of those swell 58 lb. batteries. Damn straight I'm going to put them on my robot, bringing the robot weight in at 232 lbs for batteries alone. Heck, that's almost a battlebot weight!

23 Feb 2003 (updated 23 Feb 2003 at 15:11 UTC) »

The DARPA Grand Challenge confrencies are posting results from the conference in the Forum. It looks like the judges expect the ~250 mile course to be run in 6 - 10 hours by the autonomous vehicles. I need 30 days so...

I'm out.

I performed some experiments on the motors I have and came up with some interesting results. Instead of a stall torque of 50 lbs. at 12V 3.5 Amps, the stall is more like 100 lbs. at ~6 amps. This is good and bad. Good because my robot is going to have plenty o' power to move around (maybe even with a payload) bad because the L298 motor driver I was planning to use ain't enough. My solution is to make my own motor driver using FETs .

After blowing up a few "test units" (10 so far) learning to work with them properly, I learned two things - A.) You've gotta tie your gates down when you aren't using them. B.) Don't play around with blowing up FETs, get a FET driver with a high-side charge pump. I did some research and determined the HIP4081A fits my purposes well - I also found out (via the internet) that a few of my TCRG hommies have already gone down this path and are using the HIP4081As now. I just placed an order with Newark for a few drivers and I'm waiting for them now.

While playing the FET game, my supposedly good gel-cell 12V 17-AH batteries from Mendelson Electronics didn't perform very well - like at all. Maybe I didn't take proper care of them, maybe I got jacked, whatever. My next move was to stop playing around with gel cells and get a decent deep-cycle 12V marine battery. I found a swell battery that put out 105 amps and at 58 lbs would be a freakin' mongo lump in the middle of my `bot. I got 2 of them and I'm going to put them both in the frame - aesthetics be damned.

I put (mostly) together what amounts to the new proto-type leg and immediately determined I need bearings. I've been hunting for them all day and finally stumbled across a bearing source on the net - I order a couple pairs to play with. Along with the bearings I need to lathe a decent aluminum axle (here is my future aluminum source ) for each leg joint (I'm up to 5 per leg). There have been many little changes to this leg design along the way and I expect there will be many more.

I came up with this modular method of prototyping boards I was going to use across the board on my robot. I've decided that would be a bad idea, and will only be using prototype boards to figure out what the standard boards will be. When I get it right I'll make a more economical board to put in the robot.

This robot project is spinning off sub-projects out of necessity. One thing I want to do is automate Kenneth Maxon's oven-soldering method. Another thing I want to do is morph my Sherline lathe into a stand-alone lathe/mill (this is mandatory). I'm trying not to lose focus and get distracted by these sub-projects, but I might take a month and bang them out. Luckily the same technologies used in this robot project are easily morphed into these sub projects. (If I say this often enough I might start to believe it).

I hope you guys don't mind my embedding the links into this entry - I sometimes use these entries to figure out what the hell I was thinking when I did/bought whatever it was that is in question. Someday I'll actually sit down and do a web site -

you know, when I have time...

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