youBot mecanumWheel

[Thomas-Feldmeier]

https://www.kuka.com/en-de/products/mobility/kuka-omnimove-drive-technology: The wheel consists of two rims and nine free-running rollers, which are mounted at a 45 degree angle

the contactProperties in sampleWorld of youbot are strange, the mecanum wheel angle there is not 45 degrees but something else, so the speed front/back is not same as left/right. i changed them simular to robotino, and it worked.

change contactProperties in projects/robots/kuka/youbot/worlds/youbot.wbt to this:

contactProperties [ ContactProperties { material1 "InteriorWheelMat" coulombFriction [ 0, 2, 0 ] frictionRotation -0.785398 0 bounce 0 } ContactProperties { material1 "ExteriorWheelMat" coulombFriction [ 0, 2, 0 ] frictionRotation 0.785398 0 bounce 0 } ]

the controller could be improved to use something like this (simplified pseudocode of running function)

vx = speed forward/backward, m/s vy = speed left/right, m/s vrotation = turning speed, radians/s

move(double vx, vy, vrotation){ for(int i=0; i<4; i++) { motor[i]->setVelocity( (vx

• vy * ( (i==1 || i==2) ? 1 : -1)
• vrotation ( (i==1 || i==3) ? 1 : -1) distanceToRobotCentre) / radius); } }

with motor[0] = left front, motor[1] = right front, motor[2] = left back, motor[3] = right back (watch out, different order than the wheels in youBot)

radius = 0.05m = radius of boundingObject wheels distanceToRobotCentre = 0.228 + 0.158 = x-offset + y-offset of wheel relative to robot center point

DEF WHEEL1 InteriorWheel { translation 0.228 -0.158 -0.055 anchor 0.228 -0.158 -0.055 name "wheel1" sensorName "wheel1sensor" }

[Thomas-Feldmeier]

in https://cyberbotics.com/doc/guide/youbot should be some documentation about the contactProperties (like in https://cyberbotics.com/doc/guide/robotino3)

[mael25]

Thank you @Thomas-Feldmeier for raising this issue. The angle of the mecanum wheels has been corrected and the controller improved according to your suggestion in #3025.