Rototraslation of a cylinder

> but the zeroPoint (which is the center of the cylinder) is moving due to the TranslationEngine and so not fixed.

you have to set new position each iteration e.g. using PyRunner

> if it is possible to make the cylinder restart from the initial position after some iter

yes. You can:
- create a new at original position (and destroy the old one)
- set appropriate state.pos of the cylinder components to match the original position
- set for one iteration velocity and angular velocity such that the cylinder moves to its original position

cheers
Jan

Hi Jan and thank you for your answer.

Just to clarify:

>you have to set new position each iteration e.g. using PyRunner

Have I to define a function that compute the next position of the center (es. transl_velocity*O.dt) which is called by the command of the pyrunner at iterPeriod=1?

>create a new at original position (and destroy the old one)

How can i destroy the old cylinder? And once i generate the new cylinder, do I have to update the translational and rotational engine in order to fit the new roller or can i simply name it as the previous one so that the engine works automaticalluy?

Thanks

> Have I to define a function ...

exactly

> How can i destroy the old cylinder?

for i in rullo:
   O.bodies.erase(i) # [1]

> And once i generate the new cylinder, do I have to update the translational and rotational engine in order to fit the new roller or can i simply name it as the previous one so that the engine works automaticalluy?

you can name is the same, but you have to update rotEngine.ids and transEngine.ids
Depending on specific realization, you might also need to update the function computing new zeroPoint

cheers
Jan

[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.BodyContainer.erase

Hi!

I succeeded in doing the rototranslation of the roller pretty well also thanks to a code I found here [1] and the erasing too, but I have trouble in generating the second roller after the deleting of the previous one. Actually I was able to write a script which generates 2 rollers at the very start of the simulation which are overlapped. The simulation makes firstly the first roller move, erases it and then the second one strarts to move. However, I'd like to generate the second one after the deleting of the firt one because I think that the final simulation could be faster if I have one cylinder at a time. Here's a draft of the code.

rullo = geom.facetCylinder((0,0,0),radius=r,height=d,orientation=Quaternion((0,1,0),pi/2),wallMask=7,segmentsNumber=50,material=Mat1)
O.bodies.append(rullo)
idsr = [r1.id for r1 in rullo]

rullo1 = geom.facetCylinder((0,0,0),radius=r,height=d,orientation=Quaternion((0,1,0),pi/2),wallMask=7,segmentsNumber=50,material=Mat1)
O.bodies.append(rullo1)
idsr1 = [r2.id for r2 in rullo1]

O.engines=[
..........

  CombinedKinematicEngine(ids=idsr,label='combEngine') + TranslationEngine(translationAxis=(0,1,0),velocity=0) + RotationEngine(rotationAxis=(1,0,0), angularVelocity=0,rotateAroundZero=True,zeroPoint=(0,0,0)),

.....
   ]

transEngine, rotEngine = combEngine.comb[0], combEngine.comb[1]

def updateRoller():
 transEngine.velocity = vel
 rotEngine.angularVelocity = angVel
 rotEngine.zeroPoint += Vector3(0,1,0)*vel*O.dt
 if rotEngine.zeroPoint[1]>limit:
  for t in range(min(idsr),max(idsr)+1):
   rotEngine.zeroPoint *= 0
   transEngine.velocity = 0
   rotEngine.angularVelocity = 0
   O.bodies.erase(t)
   checker.command='step2()'

def step2():
 combEngine.ids=idsr1
 transEngine.velocity = vel
 rotEngine.angularVelocity = angVel
 rotEngine.zeroPoint += Vector3(0,1,0)*vel*O.dt

[1]: https://gitlab.com/yade-dev/trunk/blob/master/examples/test/combined-kinematic-engine.py

> but I have trouble in generating the second roller after the deleting of the previous one.

please be more specific, what have you tried and why/how it did not work

thanks
Jan

Let's suppose to define the second roller "rullo1" after deleting the previous one "rullo" as follows. After the deleting, the simulation generates 2 rollers in the position(0,0,0): one remains fixed and the other one moves correctly. I don't know why it generates 2 rollers.

def updateRoller():
 transEngine.velocity = vel
 rotEngine.angularVelocity = angVel
 rotEngine.zeroPoint += Vector3(0,1,0)*vel*O.dt
 if rotEngine.zeroPoint[1]>l3-r:
  for t in range(min(idsr),max(idsr)+1):
   rotEngine.zeroPoint *= 0
   transEngine.velocity = 0
   rotEngine.angularVelocity = 0
   O.bodies.erase(t)
   rullo1 = geom.facetCylinder((0,0,0),radius=r,height=d,orientation=Quaternion((0,1,0),pi/2),wallMask=7,segmentsNumber=50,material=Mat1)
   O.bodies.append(rullo1)
                        global idsr1
   idsr1 = [r2.id for r2 in rullo1]
   checker.command='step2()'

def step2():
 combEngine.ids=idsr1
 transEngine.velocity = vel
 rotEngine.angularVelocity = angVel
 rotEngine.zeroPoint += Vector3(0,1,0)*vel*O.dt

Thanks Jan Stránský, that solved my question.