CoppeliaSim forums

Hi
I'm trying to study and learn the SLAM algorithm and I'd like to implement this algorithm in Kuka youbot which is a robot with omni wheel platform.

For now I have problem with the Robot Motion Model... I'm a bit confused about which model is suitable for this robot..and how can I implement it. I tried to get the Odometery-Based but I don't know if this robot has the encoder how can I program it in V-REP, how can I measure the distance that it moves and the orientation.
If is not or it is possible... what should I do... I'm just a bit lost :-( If it's not how can I get the velocity for the Velocity-Based model... or should I look for sth else?
I was wondering if any one could guide me that what should I look for? Or any suggestion?

besides of the uncertainty and noise I would like to know how program this robot for the accurate movement,for instance I want to have this robot rotates exactly 90 degree.. or moves forward exactly 10 cm.

P.s: It also has Laser scanner and 3d camera- But for now I'm using proximity sensors to make it simpler.. later I will consider the laser scanner.. but for this phase I just want to overcome on the motion issue not sense one. and just in the simulator... but later on I need to implement my algorithm in the real robot which I don't have access to it for now.

Thanks in advance

Hello,

the YouBot uses omnidirectional wheels which operate in a special way. I am sure those equations can be found in most mobile robotics literature, or even in the YouBot user manual. One special point is that you have 4 robot variables (4 wheel velocities) but only 3 robot position variables (x,y and gamma). Meaning that one motion variable is dependent on the 3 others.

You need to know:

• wheel diameter
• spacing between front wheels
• spacing between front and rear wheels
• the orientation of the smaller wheels (45 degrees)

With that, you can find out the equations that link the 4 wheel velocities to the robot position/orientation.
Maybe someone already did the math here and could give a hand? (we would love to help out, but this is related to control, and this is not our speciality, nor do we have time to concentrate on all existing control algorithms ;) )

Cheers

Thanks for reply.
you mean with that equation I can find out how many centimeters the robot moved and how many degree it is rotated after a command? u know since every time is a bit different in the simulator I cannot find it in hit and miss way. I need to have this measurements so accurate due to have an accurate algorithm.
Btw, does Kuka have encoders for its wheels? if not how it measures the distance that it passes?

And about the Motion Model... I hope sb who already worked on the AI special SLAM or localization with the omni wheels comes and helps me by some tips. :-)