How to determine the joint positions for a particular arm configuration one desires in general way?

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Shawn Yan

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Mar 16, 2017, 8:19:32 AM3/16/17
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ros-by-example volume 2, 11.19 forward kinematics,




let's say, author who wrote the book, wants to demonstrate forward kinematics, he defined a configuration he desired for arm and read the joint positions. 
So, how to do that in a general and more effective way?


Patrick Goebel

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Mar 18, 2017, 9:29:50 AM3/18/17
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Hi Shawn,

I'm not sure what you are asking.  Can you please provide a couple of examples?  Do you mean you want to figure out the joint angles that produce a given pose of the end effector?

--patrick

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Shawn Yan

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Mar 21, 2017, 8:02:58 PM3/21/17
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I want to make pi_robot can "write" HKU ,3 letters, in front of the robot( assume there is a wall in front of  it), simply by "show trail" checked. 

I refer to demo in 11.22.1 executing cartesian path, the main part of demo is showing how to use method compute_cartesian_path() and the pi_robot can write H now, though I have to modify the acceptable fraction from 1 to 0.95 (result fraction is 0.983)

when I try to make it write K, the path can't be planned.

How can I make it happen? 


在 2017年3月18日星期六 UTC+8下午9:29:50,Pi Robot写道:

Patrick Goebel

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Apr 1, 2017, 9:13:19 AM4/1/17
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Hi Shawn,

It is possible that one or more points on the K are not reachable by the kinematics of the robot's arm.  I suggest manually moving the gripper through the desired points using the MoveIt demo mode first to make sure the arm can actually reach the desired points.

--patrick

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Shawn Yan

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Apr 19, 2017, 4:46:18 AM4/19/17
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I want to let pi_robot "write" HKU, 3 letters in front of itself, "write" simply means "show trail" of right_gripper_link is checked.

I refer to the demos in 11.22.1 executing cartesian paths and partially complete the letter H (partial means the result fraction is not 1.0, I have to change the "fraction" in demo from 1.0 to 0.95 to make sure the planning succeeds, and the result fraction is 0.983 , then the real path H is deviated from the defined in the code)

How can I find a suitable path for writing HKU?
How can I visualize the reachable or dextrous workplace of the manipulator?




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Thanks & best regards.
Shawn Yan  严诗浩  
Irobotlab of SCUT   
School of Mechanical and Automotive Engineering
South China University of Technology (SCUT)                 
Cell86-156-2647-8298E-mail:429692...@gmail.com

Shawn Yan

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Apr 19, 2017, 8:49:05 AM4/19/17
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Manually, does it mean I drag the interactive point in demo mode? 
But it is not accurate at all.

How can I visualize the reachable or dextrous 3D workplace in demo mode?

Is there a functionality for teaching like what industrial robots do?

在 2017年4月1日星期六 UTC+8下午9:13:19,Pi Robot写道:

Patrick Goebel

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Apr 27, 2017, 9:18:33 AM4/27/17
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Hi Shawn,

Yes, drag in demo mode is what I meant.

As for your other two questions below, they would be very good questions for the MoveIt Google Group.

--patrick

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