Calling all hexapod experts for help

Lynxmotion Legged Robots
1

I’ve posted this on both the hexapodrobot forum and lynxmotion as i’m quite desperate.
Basically i’m building an hexapod as a side project to teach myself ik and some control as part of my robotics degree.

Lucky for me i only bought enough parts for 1 leg, since i can’t even get that to work.

Hopefully with your help i’ll be a ble to.
I’m using arduino for the ik calculation and a pololu servo controller for the servos.

Please help, there is something wrong with the maths and i just wanna see the robot come to life.
Thank you. (ps. bb code doesn’t work but if you follow the links you’ll see the images)

The details: i want the end of the arrow labelled 160mm to be the centre of the body, as in 0,0,0.
http://i95.photobucket.com/albums/l152/silas101/hexapod1.jpg

The formula i’ve been able to research online and seem to be able to work but doesn’t quite work.
http://i95.photobucket.com/albums/l152/silas101/hexform.png

Part of my code
fan is femur angle
tian is tibia
coxan is coxa
http://i95.photobucket.com/albums/l152/silas101/hexprog.png

Thanks again in advance.
hexprog.png

hexform.png
hexform.png716×466 14.5 KB

2

You don’t say what’s working and what’s not.

So far, your other images aren’t coming up. They will after a day or two being registered.

Not sure why you measure all the way back to the center of the 'bot.

Alan KM6VV

3

thanks for the reply.
The coxa angle works fine, the other equations give values but they aren´t close enough to the exact coordinates i wanted.

i wanted the centre of the bot as 0,0,0
but maybe thats 1 of the things i´m doing wrong aswell. i just wanted a centre point for all the legs

4

You might look at the diagram in this IK “Powerpod” thread.

lynxmotion.net/viewtopic.php?f=8&t=2534&hilit=inverse+kinematics&start=15

http://www.marconettengineering.com/HEX-Axis.JPG

You just need to compute over the lengths HipH-HipV, femur and tibia. Using those lengths, you construct the triangles, and solve them.

The old powerpod code solves them. The newer Phoenix code does as well. Cosine law, as you’ve used in your calcs.

Alan KM6VV

5

thanks for the reply, will try it again over the weekend, rough day