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Why the robot performs the same when I adjust the Roll and Yaw?
Why the robot performs the same when I adjust the Roll and Yaw?
W
Written by Wang Daniel
Updated over 3 years ago

Why the robot performs the same when I adjust the Roll and Yaw?

It normally happens when the Pitch=±90°, it's the gimbal lock, there are 2 typical features of the gimbal lock on the robotic arm.

1. When the robot is at a pos of Pitch=±90°, adjusting the Roll of the robot will get the same result with adjusting the Yaw. You can bypass this issue by switching to the "Tool Coordinate" on UFACTORY xArm Studio or use the "set_tool_position" of the UFACTORY xArm Python or C++ SDK.

2. When the robot at a pos of Pitch=±90°, the robot will report a different Roll and Yaw with the pos you sent to the robot, but (Roll_send-Roll_report)+(Yaw_send-Yaw_report)=0 or ± 360°

Here is an example to show the feature (1).

  • Move your xArm robot to [450,0,112,0,90,180]

  • Press the Yaw+/- button of the UFACTORY xArm Studio Live Control page and observed the movement of the robot.

  • Press the Roll+/- button of the UFACTORY xArm Studio Live Control page and observed the movement of the robot.

Here is a video to show the result

Here is an example to show the feature 2

  • Move your xArm robot to [450,0,112,0,90,180]

  • Send pos [450,0,112,-80,90,-170] to the robot.

  • Check the pos of the robot, it's [ 450,0,112,100,90,10], you will find (Roll_send-Roll_report)+(Yaw_send-Yaw_report)=(-80-100)+(-170-10)= -360°

Note: If you are using xArm5, no worry about this problem.

If you'd like to know more about gimbal lock, see the page of WIKIPEDIA

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