Hi about 2008-09 Jim answered a question about IK and the AL4RD he gave a link to a very nice article about IK and the AL4RD joints. What was nice was it gave the equations for each joint. All I found recently was inverse.xls, ik2.xls and invers03.xls which don’t give the joint equations. Can anybody help me find this article again or tell me the equations for each joint.
thnx
I can’t remember, sorry…
The part number AL4RD, is that a 4 axis arm on a round hexapod chassis? lol 
Here’s the sheet i typed up after digging through the spread sheets you mentioned. I use these equations in all of my own programs.
[code]M = sqrt(X2²+Y2²) //distance of a line between the base and wrist
A1 = arctan(Y2/X2)
A2 = Arccos((A²-B²+M²)/((A*2)*M))
Shldr = A1 + A2
Elbow = Arccos((A²+B²-M²)/((A*2)*B))
Xc = C*Cos(D)
Yc = C*Sin(D)
X2 = X - Xc
Y2 = Y - Yc
A = Length between Shouldr and elbow
B = Length between Elbow and wrist
C = Length of hand
D = Angle of the hand in relation to the ground
Real Target (x,y) //This target is at the end of the gripper.
Target = (x2,y2) //This target is for the wrist! not the end of the gripper.[/code]
These equations are for a two axis arm only. (x & y)
The equations are in the excel spread sheet too 
. If you click on the boxes, you will see them in the equation bar/text entry field. Its annoying, as you have to follow the referenced boxes, but you should be able to extrapolate everything . Please remember than excel does everything in radians and you have to convert it out.
