Motion Capture System¶
What is Our Arena?¶
Our robot environment, or we call arena, has 4 Aruco tags that indicates the four reference points in the environments with known relative distances to each other. These four points are used identify the robot 2D pose in the arena with a webcam. The center of arena is the origin.
Motion Capture Setups¶
You have our R4A kit?
Our R4A kit comes with a portable motion capture tags attached with strings. You can carefully take out and stretch it.
Printing tags¶
You can print out the prepared PDF from the link below. This gives you necessary tags for your arena
Cutting tags¶
Cut the 4 tags apart along with the cut lines. If you generated Aruco tags by yourself, you need to make sure to keep white area around the tag.
Placing tags and camera¶
- Cut a string in slightly longer length (~5cm/2inch) than perimeter of the boundary you want (\(2\times Width + 2\times Length\))
- Tie the both ends of string to create a loop
- Cut 4 pieces of cardboard in a size of Aruco tag.
- Attach One cardboard to the string loop as pictured below.
- Measure the width distance to attach the second cardboard from the middle of the cardboard
- Repeat Step 4-5 to create a setup as pictured below
- Paste Aruco tag with double-sided tap at correct locations.
Warning
Please attach Aruco tags ***after*** you tape all the cardboard to the string.
Make sure you place them at the correct corners.
Now you can place your portable mocap tags on the ground or any flat smooth surface.
Tip
You can add double-sided tap on the back of tags so they don't move around.
R4A kit tags have adhesive on the back.
Each tag must be placed in the specific location as pictured below.
Distances can be any values as long as all 4 tags are in camera view.
<div style="text-align: center">
<img src="../img/arena_setup.jpg" alt="arena" style="width:50%;">
<br>
</div>
Any webcams including laptop built-in cam can work as long as they can fit all the 4 corner tags with decent resolutions. However, 30Fps or cheap webcam tends to cause a lot of blur which makes challenging to track a fast moving robots.
Testing the MoCap System¶
You need a robot tag within the 4 tag boundary to obtain its 2D position with respect to the origin.
