# What is the meaning of the effort or velocity on urdf model

What is the meaning of these ? (<limit effort="3" velocity="1.178465545" lower="0.0" upper="3.14"/>) on the urdf model. ı changed limit effort or velocity but nothing changed

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Those are documented here, I'll copy pasta though:

lower (optional, defaults to 0) - An attribute specifying the lower joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.

upper (optional, defaults to 0) - An attribute specifying the upper joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.

effort (required) - An attribute for enforcing the maximum joint effort (|applied effort| < |effort|). See safety limits.

velocity (required) - An attribute for enforcing the maximum joint velocity. See safety limits.

Effort is between 0 and 100 (units are %) and velocity is radians per second for revolute and continuous joints and meters per second for linear or prismatic joints.

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Effort is between 0 and 100 (units are %) and velocity is meters per second.

I'm not sure this is correct: fi velocity is in rad/s for all revolute and continuous joints, while it's m/s for linear type joints.

( 2017-11-09 07:57:46 -0500 )edit

You're right, I corrected it. Thanks.

( 2017-11-09 12:43:08 -0500 )edit

Effort is between 0 and 100 (units are %)

I'm not sure if the effort unit is correct either. Isn't it in N? And I'm pretty sure it's not limited to 100.

( 2019-11-06 12:31:29 -0500 )edit

"The effort limit is an attribute of the limit tag. In this case, a controller cannot command an effort of more than 30 N (N-m for revolute) nor less than -30 N (N-m for revolute) on the joint."

http://wiki.ros.org/pr2_controller_ma...

( 2020-05-07 13:33:38 -0500 )edit

I am quite sure it is the limit in velocity you can give to a joint. If you change it to be really high, then you'll be able to give higher velocities to your joint.

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