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Parallel SCARA Robot

Posted by anhanyoung 
Parallel SCARA Robot
April 12, 2019 02:14AM
Hello everyone!

Yes, I am new to the forum.

I came across a few parallel SCARA robots as I was looking for a new project to work on, as I just finished with my 3-D printed robotic arm.

My inspiration was drawn from this youtube video

From my understanding, 2 servos will be needed (which I have recently ordered, I went with teknic). I was planning on using an Arduino uno but realized that I could only control one servo at a time using an Arduino. I am leaning towards a raspberry pi now as I have read some people having success with this. If someone has had success with possibly a Arduino Mega, please let me know!

I have been teaching myself reverse kinematics since it seems to be necessary in order to move the two arms with an end effector to a specific point. Though, I am kind of thinking of using Solidworks and finding my angles from there. (Please let me know if there is a better way to go about it).

I noticed that one servo is lifted above another. I am assuming this is because it helps one of the arms clear the other in order to create a 360 work envelope? Is there a specific distance that the motors should be placed and lifted? I am having a difficult time finding any information about this. From my previous knowledge, I am assuming that the length of the arms would dictate how far the servos would need to be in order to create a 360 work envelope? I suppose what I am here for is to ask for advice in building one from scratch.

Thank you so much in advance! I appreciate any advice!
Re: Parallel SCARA Robot
May 02, 2019 11:57AM
I consider building a similar thing.

I suppose you have figured out that controlling such a beast is non-trivial. It does many moves through singularities and by inertia of the arms ends up on the "other side". I think some rotational encoder in the middle joints of the arms would be a good idea to know where outer arms actually are.

Thinking out loud a bit:

I think the sum of the length of the outer arms must be the same as the sum of the length of the inner arm plus the distance between the inner mounting points.i.e. if the inner arm point straight out the head will be in the center between the inner mounting points.

If the inner arms are shorter you can never do the "flip". If the inner arms are longer you will end up with the inner arms in an awkward, and poor resolution, position where they point inwards.

Another option is to do like [www.youtube.com] , long inner arms and short outer arms. Do the "flip" on the side.

Parallel scaras are tricky.
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