Flexure joint stiffness in Sawyer

[LSMM 1]

Hello!

I am currently trying to make a model of Sawyer including some dynamic parameters. As it is possible to find for Baxter (in http://sdk.rethinkrobotics.com/wiki/Hardware_Specifications), I am looking for the joint stiffness and damping parameters of the joints of Sawyer (with flexure springs). Is there a similar page for the Sawyer (could not manage to find it....) or did someone did some measurements and could share its results?
Thanks in advance,

 

[Yichao 1]

Thank you for your request!

Would you mind briefly explaining why these specs are needed?

[LSMM 1]

Hello Yichao,

I would need this parameters in order to make a model of Sawyer. For research purposes, I am trying to build a home made feedforward controler for the robot which takes into account flexibility in joints. For now, once I compute the inverse dynamics with my home made code (using torque control or position control for trajectory tracking), the robot doesn't move as expected and has some large overshoot in some of its joints. I would like to see if by modelling correctly the joint stiffness and (viscous) friction, I can manage to control the robot better.

I hope I made my self understandable?

[Yichao 1]

Thanks for the explanation! Let me check with our Controls Team about the specs you requested. 

[Emmanuel 0]

Hello Yichao,

 

I would also be interested in discovering the exact stiffness values corresponding to the Sawyer's Series Elastic Actuator springs, since there are several stiffness-related stability conditions that need to be respected, in order to guarantee the selection of active impedances yielding a stable closed-loop design.

 

Kind regards,

Emmanuel

[Emmanuel10 0]

Dear Yichao,

 

May I inquire whether you have been able to obtain the Sawyer's joint passive stiffness values?

 

Kind regards,

Emmanuel