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# Using stiffness model in computation of FK/IK

Hello,

The RoboDK software, for calibration of robots, could consider joint stiffness parameters. I wonder how to include these parameters in computation of forward/inverse kinematics?

We have written our own codes for motion planning and control of our robots. For (geometric) calibration of our robots, we use RoboDK, but so far, we have not included the stiffness parameters.

Now for better accuracy, we want to include stiffness as well. I believe the stiffness parameters should be used to modify the DH parameters before computation of FK and IK. However, the change in DH parameters is a function of both stiffness parameters and joint torques. The software reports the stiffness parameters, but I wonder how to calculate the joint torques.

Any guidance on this subject will be appreciated.

Thank you,
Hossein

P.S.
In [Nubiola, Bonev; RCIM 2013], the found stiffness is used to modify the DH parameters (table 4); however, it is required to compute tau_i as well (Eqs. 9 and 10).
Hi Hossein,

The method is described in the paper you mentioned:
https://www.sciencedirect.com/science/ar...4512000816

You can use RoboDK to identify these stiffness values. More information here:
https://robodk.com/doc/en/Robot-Calibrat...acker.html

Albert
(12-18-2020, 08:14 AM)Albert Wrote: Hi Hossein,

The method is described in the paper you mentioned:
https://www.sciencedirect.com/science/ar...4512000816

You can use RoboDK to identify these stiffness values. More information here:
https://robodk.com/doc/en/Robot-Calibrat...acker.html

Albert

Hi Albert,

The software reports the robot parameters like attached image.

I believe it is assumed that the center of gravity of each link is on/along its x axis ( c = [COG ; 0 ; 0]), and mass of some links are negligible (Mass=0). Am I right?

Best,
Hossein

Attached Files Thumbnail(s)

Hi Hossein,

Please note that we won't comment any further on that matter.
I'm pretty sure you understand.

Have a great day.

Jeremy
Find useful information about RoboDK and its features by visiting our Online Documentation and by watching tutorials on our Youtube Channel

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