Safe Torque Off function for grippers

Sergio 2017-06-16

Hallo everybody, speaking with a customer of ours it came out a discussion about safety applied to Universal Robots equipped with Robotiq grippers.
An interesting request was to have an additional safety function inside the gripper (maybe a double 24V signal) that could trigger a sudden Safe Torque Off mode when requested by the external safety PLC.
The idea was to stop immediately the movement of the gripper without having to activate it again when the emergency is released.
This function is not only intended to ease the safety certification of the application, but, more important, it speeds up and eases a lot the use of the gripper by untrained people.
I'd like to have you opinions.

Thank you very much
Sergio

Etienne_Samson 2017-06-16

@Sergio would it be OK if it was a software thing ?
You could use the function rq_stop(). This function will stop any motion of the Gripper without the need of re-activation. When you want the Gripper to resume it's motion you use rq_go_to().

Sergio 2017-06-20

@Etienne_Samson thank you very much for your reply. Actually I am afraid that the software function cannot be classified nor certified as safe, because it relies on the program of the robot. This feature should be activated directly by a safet device.

Etienne_Samson 2017-06-20

@Sergio understood, I don't have any way of doing this since the Gripper is not a safety rated device. All we can do is write the register to have it stop. If you need to force it to stop then there is no other way but to cut power. When you do so you always need to re-activate (relative encoders).

Sergio 2017-06-20

@Etienne_Samson yes Etienne, thank you. Maybe for future development. Sergio