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View Full Version : Getting started on a quadruped need advise



Nelsontheunholy
04-13-2009, 01:33 PM
Hi guys

I have started work on a quadruped bot and need some help to get me started. Right now I am looking at 4dof legs with a pair of pan + tilts one for the head and another back mounted for some onboard weaponry and am thinking of using HS-475HB servos along with a bot board 2 coupled to a ssc-32 servo control with atom pro running it all. I have started working on the basic design in autodesk inventor but wanted to know if that is the best solution for doing the basic layout or is there a 3d cad program better suited for my needs. Also does anyone have the cad files for the HS-475HB servo as it would make it tons easier to get the layout up and running and start plotting the parts. The prototype I am gonna built out of acrylic most likely and once I am satisfied everything is running good I will get some aluminum parts laser cut. Your help is much appreciated. Call this all project Battle Tortoise!!!!

Adrenalynn
04-13-2009, 01:39 PM
I don't suspect you're going to get a quad working on 475's. I'm not the quad walker expert around these parts, but I think the general wisdom is 645's at the minimum.

Nelsontheunholy
04-13-2009, 03:31 PM
i was thinking about that but those are considerably more expensive I suposed I get what I pay for idk does anyone have cad files for both so i can try some layouts???

Adrenalynn
04-13-2009, 03:57 PM
They're a standard size servo. There wouldn't be a layout for both, or I guess the "Glass half full" side is: One layout fits all.

Yes, you get what you pay for. It this case, you get a quad that walks on the one hand, or a some expensive smoke and something that lays on the floor and flops around a little in its death-throws on the other. Of course, that gets even more expensive if you want it to do it more than once...

sthmck
04-13-2009, 04:48 PM
I have a website that details the build of my quad mech. Unfortunately because of finals and other pressing matters it hasnt been updated in a while so you wont find anything interesting on it. I was just wondering if you were dead set on using regular servos? The reason I ask is because bioloid servos are awesome. I am using them on my quad and I dont think I would ever use any other servos.

Nelsontheunholy
04-13-2009, 05:43 PM
aww so the 645 is a standard servo size cool I am going to do my taxes then get busy on this

DresnerRobotics
04-13-2009, 06:03 PM
I agree with the "use bioloid servos" advice from Sthmck. The AX-12s aren't much more expensive than the HS-645 and are a MUCH better servo all around. They do add a bit of complexity to programming though.

Adrenalynn
04-13-2009, 06:16 PM
The 645's are a fraction of a mm taller than the 475's. Maybe 0.5mm max, my micrometer is packed at the moment, but when I dig it out, I'll take an exact measurement.

There's a model of the futaba in our DataCenter, you could probably use that and just expand the height that fraction of a mm I'll report tonight (if someone doesn't beat me to it)

Nelsontheunholy
04-13-2009, 06:34 PM
anyone have a standard servo cad file handy then???

Nelsontheunholy
04-13-2009, 06:52 PM
lol cool. i will take a look

darkback2
04-13-2009, 10:05 PM
Hey,

I put together a tutorial on how to participate in mech warfare (http://forums.trossenrobotics.com/showthread.php?t=3099)...I know that isn't exactly what you are after, but the plans and PDF files for making both of my mechs...both quads...are up and downloadable including software for controlling the robot, and a price list for all of the parts.

As for the AX-12 vs HS-645s, the plans for both of the robots I have posted use standard hobby servos. That said, the hexapod that charlie (http://forums.trossenrobotics.com/showthread.php?t=2481)is based on used hs 475s for the lift servos, and 645 for moving the legs back and forth. Using a levered leg design made that possible.

If your going with a standard leg design, 645s are what I would guess to be the minimum. Squidword (http://forums.trossenrobotics.com/showthread.php?t=3100) started out with 645s, and while they worked, he couldn't carry much of a payload. I ended up going overboard and getting 5990s...

Another idea is to get servos over time. I know it isn't as satisfying as getting them all at once, but I'm planning on getting 1 5990 a month over the next year. That way the bank isn't broken. In the mean time I used tower pro mg995s...(wouldn't recommend them) and HS 645s which I pulled out of a hexipod.

I guess the real question is, what is your budget like? remember, the more degrees of freedom you have, the longer your legs will be, and the more powerful servos you will need. Similarly, the fewer legs you have the more powerful your servos will need to be.

Hope this helps.

DB

Nelsontheunholy
04-13-2009, 11:15 PM
actually I am really considering him for mech warfare as the back mounted pan and tilt could host a number of fun ways to obliterate other bots. I have a friend that works for a fab company that specializes in hi grade components and he may be able to hook me up with scrap titanium sheeting bits for use with most of the smaller brackets which would seriously cut down on weight but yet add strength

Nelsontheunholy
04-13-2009, 11:31 PM
as far as budget I am gonna be mostly buying parts one at a time you know. I am probably gonna start out with a bot board and ssc-32 and a couple of servos to start as this way as I build the components I can atleast test them to make sure they actually work. I do have a company 401k that I contribute like 50 bucks a paycheck too but they match that so at the end of the year I will have a good chunk of change to buy everything.

Nelsontheunholy
04-13-2009, 11:39 PM
but really I am not sure what I want out of a bot at the moment I may just spring and get a hexapod not sure which one I would want though I am liking the phoenix but not liking the lack of a pan tilt mechanism for it.

darkback2
04-14-2009, 10:59 AM
Your going to dip into your 401k to build a robot!? Wow...and I thought I was bad.

As for your quad, Take some time to figure out what your goal is. There is nothing worse than getting there only to find out that there isn't where you want to be. Trust me I've been there.

Also, depending on your experience level, you may be more interested in a bioloid kit. The kid would allow you to build a whole range of robots, thus you do not necessarily have to have one particular robot in mind. Also, I'm starting to think the dynamixel path is a decent one to go down. check out this connector (http://www.trossenrobotics.com/robotis-bioloid-usb2dynamixel.aspx). You can use it to control AX-12 servos...that way you could still get just a couple at a time...

In anycase, I'm sure you'll figure something out.

Have fun.

DB