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Gripper states are reversed in simulation compared to reality
I have been using both the real robot (xArm6) and the simulation in Gazebo and noticed there is a problem. In section 5.7(xarm_api/xarm_msgs) it says:
Proper range of the open distance is from 0 to 850. 0 is closed, 850 is fully open. 500 is used as an example. 'ret' value is 0 for success.
When we look at the SRDF (xarm6_gripper_moveit_config/config/xarm6_with_gripper.srdf
) file, you can see that distance 0 indicates an open state, and distance 850 indicates a closed state.
<group_state group="xarm_gripper" name="open">
<joint name="drive_joint" value="0"/>
</group_state>
<group_state group="xarm_gripper" name="close">
<joint name="drive_joint" value="0.85"/>
</group_state>
This has two consequences:
- Simulation does not de facto imitate reality.
- In simulation, there is a problem with gripper control using MoveIt- errors like the one below appear, for example.
Invalid Trajectory: start point deviates from current robot state more than 0.01 joint 'drive_joint': expected: 0, current: 0.85