Micro Hexapod Kit: MSR-µBug

[Matt Denton]

Well I mentioned I was working on a micro sized hexapod, actually I designed it about 4 months ago, but had to put it on hold until I had the MSR-H01 finished. I finally got arround to build the first prototype last night, and so thought it was time I shared it with you:

CAD Image


The prototype is currently based on the Hitec HS-55 micro servo. Its using a 6V NiMh 1400mAh battery within the body cavity, the SMB + HexEngine are invert mounted on top, as I found this hid the cabling better. Hooked it straight into the PS2 controller, and off it went, I will shoot some video when I get time.

First Prototype


My first dilemma with the kit is weather or not to miniaturize the electronics. I could even make the entire top body plate the SMB + HexEngine in one? or simply do a smaller version of the SMB with built in ds24, eg non socketed version.

I can already see ways that I could shave 15mm off the width of the hexapod by using LiPo batteries and different layouts, but by doing so, mounting a standard size PCB such as p.Brain-SMB or SSC32 would be very difficult as the body would no longer be large enough to carry them.

Size of the hex in the current configuration is 150 x 140 x 90 (mm) excluding the PS2 connector on the top. with better cable management this could be reduced by 5mm. I'm not sure the the total weight at the moment, but the servos seem happy and I added an additional 100g payload which didn't seem to make any difference to performance. Chassis material will be 3mm acrylic.

The aim of this desktop hexapod kit is to attract a wider audience into hexapods / robotics with an affordable starter platform, plus it would be fun to do micro mouse / robo soccer type event with a hex platform??

Haven't decide on a name yet, have these bashing around:

MSR-uHex (pronounced micro hex)
MSR-uBug (or Bugsi for short )
MSR-uH01 ( or back to the standard naming convention )


Thought suggestions etc... you know the drill.

[wattsie]

Matt,

Cool, love it, my first few attempts at hex's were micro servo versions, this was a few years back, so ill hazard a guess that micro servos are of better quality now!

Good idea to bring it down to a cheaper level, as it is a very expensive hobby (worse than my rc chopper, which is saying something!)

Will be keeping a close eye on this one....

Quite like the 'uBug' name, gives it a more friendly nature than MSR-H0.5 or something!

wattsie

[No1_sonuk]

Not so sure dedicating it to LiPo is such a good idea. I think most would rather use cheaper/less hassle NiMH.

SMB reduction could start by removing some of the unneeded servo connections. Integrating the processor would also cut some space.

[jaspinall]

µHex sounds/looks good

Acrylic body also looks good. HS-55 servos look quite cute, only weigh in at 8g a piece!!! That said, 1.1Kg-cm torque looks a bit feeble (Some *really* small/light servos here: http://www.servoshop.co.uk/index.php?pi ... area=Servo )

Agreed on the power pack thoughts, Lithium can be a bit "temperamental" if you don't have a half decent charger for it, though they do pack a decent charge density for size. Regarding shrinking things down...masses of space on the SMB is dedicated to servo connections, using regular 100thou connectors. Any thoughts of using smaller connectors? Also, dropping all the p.Brain components onto the reverse side of the SMB could allow for it to be shrunk down considerably, however this does then become a dedicated p.Brain board...

[plingboot]

!! Have these ready for christmas and i'll be first in the queue !!

Really like the idea of integrating the SMB into the top plate - if the servo connections were underneath and the 'important bit's were on top - that could be quite interesting. Still think there would need to be mount points for piggy back boards - or - could you also integrate a BS2p24 carrier into the design?

for my money i'd be happy to go with lipoly packs - partly because i've got a whole family of them sitting around - and partly because they are so small. I've got a Flightpower EVO20 800mAh, 3s 11.1V pack here - it's 34mm wide x 79mm long x 15mm deep (it's very slightly smaller, but i've rounded things up) and i've got a 7.4 pack in doors which is even smaller. As long as you use a cell alarm and a decent charger (see jason's post a few days back) I can only see advantages.

As for names - I like MSR-uH01

[BillB]

Looks good Matt,

In order to get more mass appeal I would try and hide the electronics. Miniturising the electronics would help - but it may be worth making a 'cute' domed facia to hide the electronics (think colourful Laydbirds and green bugs). In which case uBug would be a nice name.

Also - if you want to get into the MicroMouse market you will need a way to mount sensors on the front & sides of the robot (so that the legs do not knock the walls to the front & side - otherwise micromouse points will be deducted ).

BillB

[Matt Denton]

Thank you for the initial feedback... all wlecome!

Cool, love it, my first few attempts at hex's were micro servo versions, this was a few years back, so ill hazard a guess that micro servos are of better quality now!

Indeed I think they are gaining in quality, as I also tried some years back and was very disappointed with the result. I have sourced some similar servos in China, which would bring the kit price down further, however, I need to look into import duty etc, and then buy 20 off them just to see if they are good enough... there is not point in going really cheap if the servos keep breaking!

Not so sure dedicating it to LiPo is such a good idea. I think most would rather use cheaper/less hassle NiMH.

Interesting to hear people against the LiPo idea.. To be honest if I fit the batter inside the body, the LiPo only saves on size and a little weight, but does loose about 300 mah capacity compared to the 6V NiMh.

Acrylic body also looks good. HS-55 servos look quite cute, only weigh in at 8g a piece!!! That said, 1.1Kg-cm torque looks a bit feeble

Surprisingly the torque is actually not bad considering the weight of the hexapod is very low, also at 6V you get 1.3Kg torque, and the legs are pretty short. I think the hex could easily take another 100g or more payload. I will do some measurements when I get my scales back!

(Some *really* small/light servos here: http://www.servoshop.co.uk/index.php?pi ... area=Servo )

A little too small and cheap looking I think, but maybe for the nBug... Nano Bug ?

Really like the idea of integrating the SMB into the top plate - if the servo connections were underneath and the 'important bit's were on top - that could be quite interesting. Still think there would need to be mount points for piggy back boards - or - could you also integrate a BS2p24 carrier into the design?

The electronics are the biggest question at the moment. In the current configuration, custom electronics can be fitted, but if I create a dedicated miniaturised p.Brain system, then customising may be an issue, there should still be room for piggy back boards.

One of the biggest problems with servos is the size of the plug as mentioned, however having to fit custom miniature connectors would put allot of people off.

In order to get more mass appeal I would try and hide the electronics. Miniturising the electronics would help - but it may be worth making a 'cute' domed facia to hide the electronics (think colourful Laydbirds and green bugs). In which case uBug would be a nice name.

Yup a vac form cover would be nice!

So I'm thinking the name things is kind of tending towards MSR-uBug of course it could be part no. MSR-uH01 nickname the uBug ?

[jaspinall]

Hold the alt key down, then type 0181 on your numeric keypad

[Matt Denton]

Hold the alt key down, then type 0181 on your numeric keypad

.... while in text mode.... µBug nice!

[jaspinall]

<offtopic>
I tend to use an awful lot of numeric shortcuts for the documentation I write... Spark up charmap.exe, click any of the characters you might want to use (in the font of your choice, not all fonts carry the same symbols), then look down in the status area of the app, it gives you the alt-codes there

Here's my handy list

alt + 0181 = µ (mu, micro)
alt + 0176 = ° (degrees)
alt + 0169 = © (copyright)
alt + 0153 = ™ (trademark)
alt + 0174 = ® (registered trademark)
alt + 0177 = ± (plus/minus)
alt + 0137 = ‰ (promille, per million)
</offtopic>