[Aria-users] ArAKin help! inverse values inaccurate

**Mathew Livianu <XXXXXXXX>** · **Date** **Thread**

Hello,

I am having trouble with the ArAKin package. When I give it 5 joint 
positions, it goes there with no problems. However, for many of the joint 
configurations I specify, the backwardCalculation function returns a set 
of angles that produce a different end-effector position. Here is some 
sample output from my program (C++):

*****************************************
Please select from the following options:

         1) Specify 5 Joint Angles
         2) Specify position (x, y, z)
         3) Quit
> 2
7.458790 1.315186 -12.130641
*** Got position from user: 7.458790, 1.315186, -12.130641
*** Moving arm to position given on command line.

*** Backward calculation from position given on command line
(7.4588, 1.3152, -12.1306)
  produces the following 6 joint angles:
10 -43.3749 -101.28 0 89 0
*** Forward calculation from those angles produces:
  (u,v,w) = 14.403807 2.539780 -22.451353

*********************************************************

I have used both the fixed and non-fixed mode. Only difference is that 
with the fixed mode, I get many errors from the backwardCalculation 
function (which uses 4 joints plus the fixed final joint) because it 
cannot reach the point calculated by the forwardCalculation function 
(which uses 5 joints).

I require some insight here. How do I get the arm to go to the position I 
specify with some semblence of accuracy? Am I doing something wrong? Or is 
my understanding of the system mechanics or the function operation 
incorrect?

For reference, I am using the following versions of software and hardware:

ArAKin 2.4-2 December 21, 2005
Aria Version 2.4-1 October 14, 2005
Pioneer 3AT
Pioneer 5-DOF Arm VE 1.0
Ubuntu Linux 5.10 - kernel 2.6.12-9-386

Thank you for your help,

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Mathew Livianu
Electrical and Computer Engineering
Georgia Institute of Technology
Atlanta, GA 30332
Human Automation Systems (HumAnS) Lab
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