robots.net blog for slap.fish

28 Feb 2007

Wed, 28 Feb 2007 10:47:40 GMT

Steady progress on 48k's electronics - the card cage backplane is mechanically complete, and partially wired - and I now have 3 of the cards complete.

The first is a PSU/standby/timer card, which has two MCUs - this will monitor the PSU voltages and create recharge requests to the main CPU, and oversee the recharging once the robot has 'docked' and the main CPU relinquished control and the robot powered down (standby mode).

The second complete card is the MCU for handling the compressed air supply - a deceptively complex task. The problem with an on-board compressor is the large surge of power required to start it when the reservoir is already pressurised - there are two air valves which need to be carefully controlled, as well as the main compressor motor. I thought this would be a simple card to program.. wrong!

Third up is the card (containing 4 MCUs) which will handle the steering and drive motor controls - lots of quadrature encoders to keep track of, but ultimately an exercise in position/speed control.

Did get some time to do some initial experiments with I2C communications - and although it's a little more software intensive with PICs than I'd anticipated, it'll do the job of providing a main communication channel between all the cards quite well.

..still plenty to do before I can really get down to properely programming it all though.

- My lathe is now up and running again, upgraded with a 3 phase motor + inverter instead of the unreliable standard DC motor (burnt out the second one before xmas). As any machinist knows, small Chinese metalworking tools are good value - but don't ever rely for heavy use - at least until you've 'debugged' them and made improvements.. my little 7x12 has had many hours spent on it (a project in itself), and is quite literally a different machine. I've a few changes to the mill in mind as well! I tested out the new motor making up some parts for my fathers model R/C boat that I offered to install the motor/R/C equipment etc. into - no shortage of power now. The soft start is useful as well - but sadly, games of 'dodge the chuck key' are no longer possible - it just falls out safely instead of hurtling at your head like an enraged 5 ounce metal wasp that's smelt your ice cream. I feel I can live without that though.

Back onto robotics now - A Boebot joined the throng of projects competing for spare time. This is my first experience of the Basic Stamp (version 2), and I must say I'm really impressed me with the speed and ease with which you can have it doing some clever stuff. I liked it so much I've now got a second one to experiment with. They're very difficult to beat in terms of ease of use - and it's nice to be able to play around and get real results quickly.. something that programming PICs in ASM definitely isn't.

3 Jan 2007

Wed, 3 Jan 2007 16:52:24 GMT

A new year, and things are gathering momentum.

Since the last entry, I've been working on the pneumatic compressor controller, and the first of the MCUs which has the task of overseeing the system power/recharge strategy - as well as some smaller functions which I've grouped together as it will have it's own standby PSU - like system clock/standby/hibernation modes, and a few others.

I've been developing using Microchip 16F876 devices and an ICD2 clone under MPLAB/Assembler - and so far this combination is perfectly suited to the lower level MCUs, so I'll probably be staying with this setup for most of the first layer - the pneumatics, drive and steering - and all of the associated encoders and other feedback are all doable, it seems - and importantly, I2C communications to the next layer in the heirarchy are supported also.

Other parts like the card cage/backplane, and battery power distribution are coming together.

In other news, I've also added another robot arm to the menagerie - a UMI RTX just like this one:

http://users.telenet.be/emlab/Foto's/rtx2.jpg

I've had it moving and knocking things off shelves using RS232 - and writing some more code that has it doing something a little more constructive is a future project. A nice task for it would be waiting at the recharge outlet for when 48k needs a top-up, and having the arm wake up and plug in the charger sounds like a good challenge in robot cooperation - which is another area of interest.

6 Oct 2006

Fri, 6 Oct 2006 10:54:48 GMT

Ok, no stories about house decorating this time, I promise.

I've actually just aquired a working robot arm - a Teachmover, like so: http://www.questechzone.com/microbot/teachmover.htm

It's one of those classic stepper/cable driven arms, popular with universities etc. No manual, but the teach pendant is easy to use, and after a little googling, I had it repeating sequences quite quickly - I have some partial information on the RS232 interface commands, but if anyone else reading has experience with one of these, or any any information, I'd be interested to hear from you!

It joins the other arm I have - a slightly larger TQ MA2000 aka 'The Open University Robot' - which is in need of a new controller and some mechanical attention (needs new wrist servos and a replacement gripper, as the old one was pneumatic only), as I bought it non-functional - that's currently packed away, as a future project.

Anyway, it's a neatly put together little arm that has the features of more serious 'proper' arms that cost 10 times as much, and a big step up from those battery powered toys and kits you can get that strain under their own weight and wobble around when you sneeze in the next room. Surpisingly rigid, and can pick up a few ounces without a problem. Quite apart from the fact I enjoy mucking around with this kind of stuff anyway, I got it (and the other TQ arm), to study and help give me some ideas (and hopefully avoid any pitfalls) for designing the arm for 48k - which will be a far larger and more serious piece of kit, and which I want to get right, first time - considering the time and money involved.

11 Sep 2006

Mon, 11 Sep 2006 13:27:00 GMT

It was my daughters sixth birthday party yesterday - and foolishly, we 'threw' it at home.. haha. Anyone who's ever had a kids party at their own house, grimace.... now; Solidarity, brother.

In the second half - after all the kids were fuelled up with sugar - and I was the object of some collective vengence I couldn't quite understand or manage to escape from (just being in the garden was enough, I suspect), I inadvisedly played the 'Team Monster' part too well - and our neighbours son (same age) played his Action Man character perfectly - and felled me with a left hook to the unmentionables, bless him. Whilst in the recovery position - our other neighbours daughter, one year younger - yelled 'kick him in the goolies!!' - and although I thought this was commendable, and in the party spirit, thought it was rather out of character for a fairy. She did make me a cup of 'monster tea' whilst I recuperated in the 'dungeon' though, nice one Hollie. Anyway.. you get the general idea - feigning immobility (actually that bit was for real), sleep, or death, did no good - and after 45 minutes of that I felt like a Pinata... I'm sure this tradition was invented after parents realised if the kids had something else to beat up on, they could avoid all that awkward writhing around in agony - damn fine idea if you ask me. In England we're not so clever, see - plus the mere suggestion of a hitting a paper mache donkey with sticks would bring down the wrath of a small army of little people upon us, kids here seem to prefer a live target that they can get groans of pain out. Next year I'll hire a clown for them to beat up, and somewhere that isn't our house for them to beat it up in - mostly for reasons of forensic evidence.

Talking of the the house - it is finally finished.

Wow.. Still can't quite believe it myself - 4 months it's taken, and if I live to never see another plasterboard screw, or half a bag of cement et cetera (it's a looong list) - I'll be happy.

This week, I will mostly be working on getting a pretty good pathalogical hatred of painting going - I conservatively started at 'dislike' - and after approx 16 cummulative hours so far, I've already got my teeth grinders merit badge - yay me.

I estimate another 100 hours or so to go - after which Defcon 1 will be long gone and I'll be continuously mashing the big red button, oooh yes. My only relief will be screaming 'Paaaint... Bruuush!!' at Jehovas Witnesses when they come round at Xmas for their annual attempt at explaining how, in fact - I've actually got it all wrong. This year I've cancelled Richard Dawkins, and decided to argue in the style of an enraged decorator you see - and although right now it seems a fair way off, when the time comes I'm gonna do this particular idiom with feeling, and possibly with bells on (no really - they hate that drunken seasonal stuff).

Enough of that, anyway - you probably want to know something more Robot-related ? Well, 48k is still in the garage - although now looking more like it (rightfully) owns it - rather than merely happening to be also in it - as was the case up until recently, what with all the other stuff being stored in there. Some of the kids (see above) were suitably impressed, even though it didn't look like a 'real' robot (False Maria has a lot to answer for). I have a lot of getting up to speed to do - the lathe and mill in the shed need a freshen up after their time off - not that there's much more metalwork to be done, hopefully. What's nice though, is that after a long break, looking closely again at it - I get a rush of enthusiasm to think of how I've designed & built this thing - and can't wait to crack on once again, checking up on Robots.net once in awhile during the summer has helped keep the creative engine idling, and now it's raring to go again.

Actually, talking of robots - I think there is a niche for kids birthdays.. like these security droids that roam banks at night or something. Tactical support for childrens entertainers would be welcome, don't you think ? I see there is some consideration for lightly arming security robots, though I think that would be inappropriate for a kids party - as they'd need to be *definitely* armed.

6 Jul 2006

Thu, 6 Jul 2006 14:23:25 GMT

not much progress on 48k for awhile - I'm in the midst of major house renovation/extensions, which, amongst other things, means that every scrap of storage space is packed full of boxes - including the spare rooms.. one of which will become the new workroom, and doubtless will be the last I'm allowed to finish and get my bench and equipment set back up again.. woe..

still.. despite all the moving around, 48k has stayed on it's stand in the garage like the very heavy, very complicated looking, shiny, and extremely dangerous if fallen on by thing that it is.. like it's somehow immune to the chaos going on around - which seems somehow gratifying.

During the course of the work on the house - every single builder, carpenter, bricklayer, plumber, electrician, apprentice thereof and general gawker has asked the same questions, in the same order - without fail.

What is it ? What does it do ?

Despite giving quite a few different variations on the same general theme(s) that qualify for answers (remote control robot, robot for retrieving small objects, robot for roving around autonomously, robot for throttling neighbourhood cats that dare to defocate under the rhododendrons, robot for world domination as long as there are no steps etc.) - I know they all think I'm not quite all there.. in the nicest possible sense of course - though I've noticed they do scrutinise free cups of tea just a little more closely afterwards.. hmmm. There is often a third question (perhaps optional ?) - which is 'So what do *you* do ?' - I'm not quite sure I ought to wonder too hard on why they ask that one.

anyway.. in another month or so I may be able (allowed?) to get back to it - does anyone know the typical ultrasound signature of the average un-house-trained cat ?

1 Mar 2006

Wed, 1 Mar 2006 10:50:03 GMT

I promised a more up to date picture of 48k - so:

latest pic

It's in a somewhat 'stripped' state at the moment - the arm base joint, batteries, and electronics housings are missing - but it shows the mechanical layout clearer.

There is very little in the way of actual control elements in place yet - but I thought people might appreciate seeing a bit more of what's involved in the actual mechanics, as this is an area often overlooked. I for one like to see how something works under the skin.. a robots 'bones' if you like - the hardware solution is just as interesting to me as the software.

a couple more, showing some details:

drivetrain suspension

---

I will be remounting the arm base joint and batteries soon - and then onto connecting up the pneumatics.. then it'll be on it's wheels and under power for the first time sometime soon [rubs hands and laughs like Vincent Price].

15 Feb 2006

Wed, 15 Feb 2006 11:30:29 GMT

Some background on 48k - here are a few pics showing a somewhat disjointed progression of the build:

http://homepage.ntlworld.com/retro.spect1/robot.JPG http://homepage.ntlworld.com/retro.spect1/rob1.jpg http://homepage.ntlworld.com/retro.spect1/rob2.jpg http://homepage.ntlworld.com/retro.spect1/rob6.jpg http://homepage.ntlworld.com/retro.spect1/rob7.jpg http://homepage.ntlworld.com/retro.spect1/rob8.jpg http://homepage.ntlworld.com/retro.spect1/rob9.JPG

You can see that early on, I'd planned on driving the wheels via differentials and a single motor - that was changed in favour of a gearhead motor per wheel, arranged to drive the wheels directly (via couplings). Most recently, I have altered the drive arrangements again to a belt system, which means the drive train now has some allowance for slip built it, and any shock torques are unlikely to damage the gearheads - an extra 2:1 was used as it was looking increasingly likely that climbing a 15 degree incline was going to be close to exceeding the motors capabilities.

Last night I had the first wheel under power, using the new layout, and it works great - another added benefit of belt drive is I can quickly disengage the tensioner, effectively disconnecting drive, and allowing a freewheel mode - which I'm sure will come in useful when it's finally out and about, and I need to tow it home on a rope - picking it up will not be an option!

9 Feb 2006

Thu, 9 Feb 2006 10:48:04 GMT

Well, 'Hello World'... I've been regularly checking up on Robots net for a couple of years now - but have finally motivated myself into joining.

I am currently working on this:

http://homepage.ntlworld.com/retro.spect1/rob9.JPG

This picture is a little old now, and I will endevour to get something more up to date on my site soon.

It is (will be) an autonomous Rover - as you can see it is no small undertaking, and the project is in it's 3rd year, I will add it to the list of robots when I feel it qualifies - for now, I am still tinkering with the mechanics, and getting them just right, before I set it down and get out the way (it will be in excess of 100kgs when fully built).. a Rover shaped hole in the wall is a distinct possibility in the future - not to mention me running down the road frantically warning people out the way.

Excuse my irreverence.. it IS a serious project - I, however, am constrained otherwise as, being only a hobby - it is the only way to remain sane. How else does one keep smiling, night after night in the shed - setting titanium turnings alight and picking aluminium swarf from surprising places ?

By the way - the large assembly torward the front is the base joint for a substantial arm, which I have provisionally pegged at a 5kg payload, fully extended (approx 1 meter)