what does the revolute joint's effort limit be zero mean?
<joint name="joint_1" type="revolute">
<origin rpy="0 0 0" xyz="0 0 0"/>
<parent link="base_link"/>
<child link="link_1"/>
<limit effort="0" lower="-2.87979" upper="2.87979" velocity="4.36332"/>
<axis xyz="0 0 1"/>
<dynamics damping="0.0" friction="0.0"/>
</joint>
hello, from above can see the effort limit is set to zero, I want to know what does this mean? another question: now I am using an abb industrial arm in ROS, when start it's gazebo launch the arm will not fall down. I have some puzzle about this, because the arm link has it's own mass. Thank you for help!