# LabVIEW

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## command a robotic arm

i have such a project : command of 5-joints robotic arm..so i upload the conception of this arm from solidworks to labview ( using the extension .wrl) i made the different axes of each link (in the robot simulation model builder) then i test my arm using the forward kinematics VIs,,i give the value of each joint angle then i observe the postion of the end effector of my arm..but the problem is that values of X,Y,Z obtained didn't correspond with the real position of my end effector ( the end effector can be for example in a position where X>0 but the result is X<0 !!) i think that the problem has as origin the different axes that i made (hartenberg convention !), but i can't resolve this problem

so i upload for u my VI (simple try) to undertand better my problem

thanks

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## Re: command a robotic arm

this is my VI named ''5x_essai2''

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## Re: command a robotic arm

Working with a multi-dimensional mechanical system can be confusing, as the order of the matrices is critical (since rotation matrices don't commute).  The first thing to do is to test the axes one at a time, as this is unambigous.  Move Axis N (1..5) from 0 to +1 (or the equivalent units), and from 0 to -1, and make sure it "goes in the right direction".  Then look closely at the mechanical arrangement of the axes and order your matrix transformations the same way.  Test it with pairs of axis movements, and if all pairs seem to work, you can try moving all at once (and verifying that you "got it right").

Bob Schor

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## Re: command a robotic arm

Thanks for ur reply

I verified the direction of different axes and i didn’t find problems.

The problem usually in the coordinates of my end effector, it gave me wrong results.

I know that this problem come from the stage when i made the coordinate system of each joint, ( i did these coordinate systems according to hartenberg’s convention)(i used two axes like in  figures below) but it didn’t work.i didn’t understand this ‘’  Then look closely at the mechanical arrangement of the axes and order your matrix transformations the same way’’ how can i order my matrix transformations ? it’s an output for me and it depends to the arrangement the coordinate systems of each joint.so the problem is how can i arrange the different coordinate systems of each joint !! i didn’t really find a method !

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