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What is the difference between pose goal ,joint goal, and space joint goal.

asked 2020-08-18 16:54:11 -0500

saztyga gravatar image

I was following Moveit tutorials ,

i am confused about these 3 terms , plz let me know.

ubantu 18.04 3.28.2 , ROS Melodic.

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answered 2020-08-18 17:59:37 -0500

fergs gravatar image

I think there only 2 things here - and they are two different ways to specify what the success criteria for the planner are:

  • "joint goal" or "joint space goal" (same thing) - this means your goals are defined based on what angle each joint should be in at the end of the plan.
  • "pose goal" - this means your goal is defined on the final pose of the end effector. MoveIt will do Inverse Kinematics (IK) to find the joint angles required to reach this goal.

The reason it is called "joint space" is because the "configuration space" is defined by the number of joints in your robot arm and their allowable range of motions. The "configuration space" is a widely used notion in mathematics and planning - so you can find lots more information if you want to delve into that later, but really, all you need to decide now is: do you have a goal based on where the end effector should be? or based on what angle the joints should each be set to?

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Thank You for the response sir, so in pose goal approach we provide XYZRPY and moveit will do rest of the job, but in joint goal we need to provide value to each joint in order to get xyzrpy?

saztyga gravatar image saztyga  ( 2020-08-18 18:28:57 -0500 )edit

That is correct. Generally if you're trying to do XYZRPY of the end effector, you'd just use the pose goal. The joint space goals are really for putting the arm in a specific known configuration (for instance, a "ready" pose that tucks the arm out of the way of the camera, etc).

fergs gravatar image fergs  ( 2020-08-22 09:41:07 -0500 )edit

Thank you sir. . Now its Crystal clear to me. . Thanks a lot

saztyga gravatar image saztyga  ( 2020-08-22 15:02:53 -0500 )edit

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Asked: 2020-08-18 16:54:11 -0500

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Last updated: Aug 18 '20