TranslationXY2D iktype

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TranslationXY2D iktype

baxelrod

I have a planar 3 link arm that I would like to use TranslationXY2D with.  However, my arm is in the XZ plane.  I am not sure, but I think this is leading to some strange results…

 

More specifically, my 3 link planar arm is attached to a turret.  So when creating the IK database, I set the base link as the turret frame.  this generates the IK database just fine.  Then I get the Jacobian for my arm out of the IK.  When I use the Jacobian to control my arm in the Z (up) axis, it works as expected.  However, if I try to control the arm in the X (forward) direction, I get impossibly large values out of the Jacobian. 

 

Why are there no other 2D IK types for the other possible planes?  If I want to use this IK type, do I have to change my axes? 

 

Thanks,

Ben

 

Ben Axelrod

Sr. Robotics Software Engineer

iRobot Corporation

8 Crosby Drive, M/S 8-1

Bedford, MA 01730

(781) 430-3315

[hidden email]

 


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Re: TranslationXY2D iktype

Rosen Diankov
Administrator
Dear Ben,

The IK coordinate system is always built using the manipulator's base link coordinate system. Therefore, if your base link is rotated so that its XY axes align with the world XZ axes, you will get the correct IK generated. Afterwards, you'll have to be very careful with how you call the IK. When the global IkParameterization is passed to the FindIKSolution manipulator function, it gets transformed into the base link's coordinate system before being passed to the IK. There might be problems with that since we've never tested it...

There ideally would be a XZ2D IK and the extensions to ikfast should be trivial: just copy most of the code for the XY2D case and use the Z axis instead of the Y.

hope this helps,



2014/1/22 Axelrod, Ben <[hidden email]>

I have a planar 3 link arm that I would like to use TranslationXY2D with.  However, my arm is in the XZ plane.  I am not sure, but I think this is leading to some strange results…

 

More specifically, my 3 link planar arm is attached to a turret.  So when creating the IK database, I set the base link as the turret frame.  this generates the IK database just fine.  Then I get the Jacobian for my arm out of the IK.  When I use the Jacobian to control my arm in the Z (up) axis, it works as expected.  However, if I try to control the arm in the X (forward) direction, I get impossibly large values out of the Jacobian. 

 

Why are there no other 2D IK types for the other possible planes?  If I want to use this IK type, do I have to change my axes? 

 

Thanks,

Ben

 

Ben Axelrod

Sr. Robotics Software Engineer

iRobot Corporation

8 Crosby Drive, M/S 8-1

Bedford, MA 01730

<a href="tel:%28781%29%20430-3315" value="+17814303315" target="_blank">(781) 430-3315

[hidden email]

 


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