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 Post subject: My Quadruped Project
PostPosted: Sat Sep 17, 2011 7:59 am 
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Hi, I have started working on a hexapod project because I find multi-legged creatures more interesting than bipeds. I saw the A-Pod, Phoenix and the other hexapods on the lynxmotion site and I thought why not, I'll make one as well.

I have uploaded pictures of one of the legs of the robot, all the parts that make that leg and I will shortly be uploading a short video of two of the legs sort of working.

Thanks for looking! :D


Attachments:
Leg assembled.jpg
Leg assembled.jpg [ 718.99 KiB | Viewed 3152 times ]
Parts for one leg.jpg
Parts for one leg.jpg [ 789.41 KiB | Viewed 3152 times ]

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 Post subject: Re: My Hexapod Project
PostPosted: Sat Sep 17, 2011 8:18 am 
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Here is the video of the two legs moving.



What does everyone think so far? It's not much, but it's a start.

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 Post subject: Re: My Hexapod Project
PostPosted: Sun Sep 18, 2011 5:17 pm 
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Its looking really cool! I like the design of your legs. Ill keep an eye on how your project is coming along :)


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 Post subject: Re: My Hexapod Project
PostPosted: Mon Sep 19, 2011 9:10 am 
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Thanks. I've currently got 4 legs assembled but my router broke down so I haven't been able to make the body. :( . However, it gives me time to work on the code for making it walk and do other things and the body should be ready in a few days (I'll be using a friends router).

Thank you for showing interest!

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 Post subject: Re: My Hexapod Project
PostPosted: Tue Sep 20, 2011 5:01 am 
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Ok I've got another problem. I know this is supposed to be my project but I require some help (just a little bit). I have some code here which I got from a Biped BRAT tutuorial and I wan't to know what the "TOINT" part meant and also what the numbers in the brackets next to the aServoOffsets mean/stand for. Here is the chunk of code:

Code:
hservo [lefthip\TOINT (-lefthippos*stepsperdegree) + aServoOffsets(3)\TOINT lhspeed, |
         righthip\TOINT (righthippos*stepsperdegree) + aServoOffsets(0)\TOINT rhspeed, |
         leftknee\TOINT (-leftkneepos*stepsperdegree) + aServoOffsets(4)\TOINT lkspeed, |
         rightknee\TOINT (rightkneepos*stepsperdegree) + aServoOffsets(1)\TOINT rkspeed, |
         leftankle\TOINT (-leftanklepos*stepsperdegree) + aServoOffsets(5)\TOINT laspeed, |
         rightankle\TOINT (rightanklepos*stepsperdegree) + aServoOffsets(2)\TOINT raspeed]
   ;hservowait [lefthip,righthip,leftknee,rightknee,leftankle,rightankle]


Thank you for the help!

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Last edited by akdabaous on Fri Jan 06, 2012 12:14 pm, edited 1 time in total.

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 Post subject: Re: My Hexapod Project
PostPosted: Tue Sep 20, 2011 8:55 am 
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This is a conversion from floating point (real numbers) to integers. This version of the brat program is probably using floating point math to do the calculations. For example StepsPerDegree may be defined like 166.6

Note: that in many of the programs some of us try to avoid floating point math as the underlying hardware has no support for floating points. So we often do our math with fixed point where we may keep our values like positions or angles in something like 10ths of a degree or maybe 100ths... So instead of:
Code:
TOINT (-lefthippos*stepsperdegree)


You may see something like:
Code:
(-lefthippos1*stepsperdegree1)/100

Where the 1 at the end of the variable is a reminder to us that the value is 1 decimal place...

Hope that helps.

Kurt

P.S. - Don't worry, all of us with our own projects often ask for help. :lol:


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 Post subject: Re: My Hexapod Project
PostPosted: Wed Sep 21, 2011 4:19 am 
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Thank you, I think I understand it. I am trying to write the code for the hexapod for only a Basic Atom Pro (and not using the PS2 remote controller or other boards in conjuction with the Bot Board II).

Here is an update on the project so far:


Attachments:
File comment: I'm starting with a quadrapod and then working my way up to a hexapod.
Four legs attached to bottom part of body.JPG
Four legs attached to bottom part of body.JPG [ 495.32 KiB | Viewed 3042 times ]

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 Post subject: Re: My Hexapod Project
PostPosted: Wed Sep 21, 2011 8:49 am 
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Ok, here we go - the completed quadrapod (WAHEY)!

I'll be working on the code during the next few days and I should have it working by the weekend or Monday at the latest (provided nothing unexpected happens).


Attachments:
File comment: The completed quadrapod.
Completed Quadrapod.JPG
Completed Quadrapod.JPG [ 356.8 KiB | Viewed 3029 times ]

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 7:18 am 
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I've started programming it with simple commands and so far I have got it to sway from side to side - I've named it the "Spider Dance". (Okay it's missing four legs but the "Quadrapod Dance" doesn't sound very nice). :mrgreen:

Here is a photo of the quadrapod with new shiny black legs (the other red ones were quite flimsy but the new ones are much stronger). I'll upload a video of it shortly. How's it looking so far?

P.S. I was bored so I wrote my name in Arabic (that's as much as I can do in the language).


Attachments:
File comment: New shiny legs for the quadrapod.
New legs.jpg
New legs.jpg [ 657.3 KiB | Viewed 3000 times ]

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 9:22 am 
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It doesn't look like your legs can move very far forward or backward. You might need to cut some of the body out to get a full range of motion. Other than than, cool project! Keep it up! :D

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 11:07 am 
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Um yeah, I was hoping no-one would notice that. I realised that about an hour after I cut it out and I currently have a new more efficient design which I will be cutting out soon.

Thank you for the comment! :mrgreen:

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 11:34 am 
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I'm sorry to be the bearer of bad news, but I just noticed the servos you are using are HS-422. The really long femurs are going to be too much for them. The femurs on our 3DOF legs are much shorter and they require 485 servos as the minimum. I would recommend scaling it way down, or getting more powerful servos. :(

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 12:33 pm 
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Oh ... Ok. I'll buy some more powerful servos and then it should be good to go (well, good enough for some basic movement).

Thank you for the tip. :D

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 Post subject: Re: My Hexapod Project
PostPosted: Thu Sep 22, 2011 2:56 pm 
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Also, it's easier to make a hexapod walk then a quadruped. Read the threads.

Alan KM6VV

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 Post subject: Re: My Hexapod Project
PostPosted: Fri Sep 23, 2011 9:31 am 
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Ok. I am going to buy some more powerful servos but I am unsure of which ones to purchase. I was thinking of purchasing HS-5485HB High Torque Digital servos but does anyone suggest anything else? The dimensions of the quadrapod are:

length = 24cm
width = 50cm (end of one fully extended leg to the other on the opposite side)

I hope they are of some use.
Thank you for the help! :D

P.S. Could someone post some information on good high current battery packs (something with about 4-5A) and with roughly 6-7.2V. Thank you again!

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Last edited by akdabaous on Fri Sep 23, 2011 9:55 am, edited 1 time in total.

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