[PD] Calculating Inverse Kinematics Using Expr

cyrille henry ch at chnry.net
Wed Jan 25 17:10:31 CET 2017

```hello,

I think expr did not compute long expression in the order you want it to.
with more parenthesis, result are different.
see attachement
cheers
c

Le 25/01/2017 à 17:03, me.grimm a écrit :
> Hello,
>
> I am trying to calculate inverse kinematics in 2D space with 2 DOF according to this tutorial(1) and formulas within using [expr]. For some reason my calculations for "c2" using [expr] deliver quite a different result than the excel sheet calculation that the tutorial provides.
>
> What am I doing wrong here? It may be I don't quite understand how "^" is used?
>
> Using:
> Linkage 1 length of 5
> Linkage 2 length of 4
>
> and plotting my the end of joint 2 at (3.56, 6.43) I should get c2 to equal 0.3254625 but get 0.25 with [expr]. Because of this further calculations to get joint angles are also off, obviously.
>
> attached is patch.
>
> but maybe someone has already done this type of work which might save me some trouble...
>
> cheers
> m
>
>
> (1) http://www.societyofrobots.com/robot_arm_tutorial.shtml#inverse_kinematics
>
> --
> ____________________
> m.e.grimm, m.f.a, ed.m.
> syracuse u., tc3
> megrimm.net <http://megrimm.net>
> ____________________
>
>
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