closed loop with obj files

Official Python bindings with a focus on reinforcement learning and robotics.
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chrischii
Posts: 4
Joined: Fri Dec 25, 2020 6:11 pm

closed loop with obj files

Post by chrischii »

Hi all,
first of all Merry Xmas!

I am new to pybullet and want to perform a collision detection self contact and contact with several closed loop systems installed next to each other.The geometry is created in Creo and exported as obj files.

I read now tons of sites and have several questions:


1. I came to the conclusion, that the urdf file import in not possible for closed loop systems. Is that correct?
2. Because of 1, I have generated a .py file where I define a CollisionShape for each component like shown below

Code: Select all

                 p0 = p.createCollisionShape(p.GEOM_MESH,
							   halfExtents=[0, 0, 0],
							   fileName="obj/part0.obj",
							   collisionFramePosition=shift0,
							   meshScale=meshScale)
I assembled the individual shapes to

Code: Select all

    mla = p.createMultiBody(body_Mass,p0,visualShapeId,basePosition,baseOrientation,
                        linkMasses=link_Masses,
                        linkCollisionShapeIndices=linkCollisionShapeIndices,
                        linkVisualShapeIndices=linkVisualShapeIndices,
                        linkPositions=linkPositions,
                        linkOrientations=linkOrientations,
                        linkInertialFramePositions=linkInertialFramePositions,
                        linkInertialFrameOrientations=linkInertialFrameOrientations,
                        linkParentIndices=indices,
                        linkJointTypes=jointTypes,
                        linkJointAxis=axis)	
Is there a way to define and pin a base part, similar to the import option "useFixedBase" for urdf import? If not, how can I specify which part should be the base and how can I fix it?

3. If I use pybullet headles, how can I detect collisions / get an output somewhere, e.g. textfile

Thanks in advance for your help
chrischii
Posts: 4
Joined: Fri Dec 25, 2020 6:11 pm

Re: closed loop with obj files

Post by chrischii »

Problem partially solved.
closed loop is not possible for urdf, but creating a constraint after importing the urdf works.
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