Why use a green ball as maker? How can I use AR code for calibration?

[TZW-056]

Thanks for your wonderful work! But I have a question for this calibration code : Why do you use a green ball as maker which I can not obtain. Can you tell me how I can use AR code for calibration which I can easily obtaion? I am newer for robotic field. Thanks for your kindly reply!

[ravijo]

@TZW-056 Thanks a lot for your words.

Any marker is fine, as long as you can track it in 3D space. Green ball is easiest to track, so I used it. See the below code snippet:

https://github.com/ravijo/multiple_kinect_baxter_calibration/blob/5b883da744799abbf78f400f40e142d8450a7c9d/src/data_collector_pc.cpp#L288

Here, you can use other markers and record that marker position with respect to camera. Hope it helps!

[TZW-056]

I am so excited for your quick and kind reply and I successfully run this repo in my workspace with a green balloon. But the result is not so satisfying. The calibration error is 9.57 cm and I do not know that exactly mean.

And I have some questions for this repo. Hope you can kindly explain for me!

1. when I run the calibration_data_collector.launch , an error occured : Couldn't record any data. Run the program again. Just like below. And [Kinect2Bridge::main] waiting for clients to connect in the kinect2_bridge.launch. I guess if the kinect v2 do not successful used. But there are Successfully detected sphere 0 times out of 5 in the calibration_data_collector.launch.
2. After successfully calibrate baxter and kinect, what should I do to conver the grasp pose in kinect coordinate system to baxter coordinate system.

Thanks for your kindly reply though I am newcomer to robotic. :smile: :+1: