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Effective mass calculation in TS15066 
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Answered  
/ Most recent by BMatthias
in Robot Safety

2 comments 
Sebastien
Posts: 219 Handy
in Robot Safety
Hi pros,
we are working on a safety analysis for a UR10 application with Robotiq gripper. I have two questions.
1How do you treat the fact that the operator can have his hand stuck in the 2F85 gripper which has a closing force of 235N and the quasistatic limit for fingers is 140N in the TS15066.
2Are you simply doing like I do to calculate the effective mass of the robot in order to calculate the maximum speed that the robot can go at? I simply use the TS15066 formula where EffectiveMass = (Mass of robot moving part/2) + Effective Mass of robot payload.
In that formula I simple assume mass of moving par of the robot to be the weight of the robot and the effective mass of the payload to be tooling weight plus workpiece weight.
What are you pros doing?
we are working on a safety analysis for a UR10 application with Robotiq gripper. I have two questions.
1How do you treat the fact that the operator can have his hand stuck in the 2F85 gripper which has a closing force of 235N and the quasistatic limit for fingers is 140N in the TS15066.
2Are you simply doing like I do to calculate the effective mass of the robot in order to calculate the maximum speed that the robot can go at? I simply use the TS15066 formula where EffectiveMass = (Mass of robot moving part/2) + Effective Mass of robot payload.
In that formula I simple assume mass of moving par of the robot to be the weight of the robot and the effective mass of the payload to be tooling weight plus workpiece weight.
What are you pros doing?
Tagged:
1  The 2F85 gripper has a chart in its installation manual that shows the semilinear relationship between closing speed and force. You can always set a maximum allowed closing speed in a UR thread or have a monitoring variable in an event that looks at the closing speed and triggers a robot halt upon exceeding that allowable speed. If you select the proper maximum speed and closing force values and set monitors to each, that is one way to limit the force exerted on fingers. The obvious better solution is to prevent any human body part from getting that close to the robot, but if that is unavoidable then maybe try the first part of this post.
2  Sorry I can't be of help on the latter point.
Good luck!
I've noted that your post is from over a year and a half ago. Nevertheless, let me suggest a possible reference to address your second question:
https://www.robotic.dlr.de/fileadmin/robotic/albu/Khatib_IJRR95.pdf
See in particular section 4.2 in which Khatib develops the expression for the effective mass at the point of contact / point to which the Jacobian transformation applies.
The formula given in ISO/TS 15066 is an extreme simplification, which hopefully does alright in most practical cases.
Best wishes.