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I am trying to make a simple simulation where an iiwa arm picks up foam bricks from a tower. However I have been running into issues finding a way to generate multiple bricks and moving them. The block of code below is how I am currently generating this tower, but this results in the bricks being unable to move the Z plane that they are generated on.

sdf = FindResourceOrThrow("drake/examples/manipulation_station/models/061_foam_brick.sdf")
z=0.35
for i in range(2):
        planar_joint_frame = plant.AddFrame(FixedOffsetFrame("planar_joint_frame", plant.world_frame(), RigidTransform(RotationMatrix.MakeZRotation(np.pi/2),[-0.4, 0.2, z])))
        instance = parser.AddModelFromFile(sdf, f"object{i}")   
        plant.AddJoint(PlanarJoint(f"joint{i}", planar_joint_frame, plant.GetFrameByName("base_link", instance), damping=[0,0,0]))
        z+=0.05

Is there another way to generate multiple models that can be manipulated by the iiwa arm?

Carlos
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1 Answers1

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If you want them free to move in 3D, then you don't want to add the planar joint. In fact, you don't need any joint (for them to be free). You probably want something as simple as

for i in range(2):
  instance = parser.AddModelFromFile(sdf, f"object{i}")

??

Russ Tedrake
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  • We wanted to set the positions for each of the blocks. Adding the instance alone let the block fall from the origin. Is there a function we could use to move where the blocks spawn? – Carlos Aug 09 '21 at 17:06
  • Please take a look at https://manipulation.csail.mit.edu/clutter.html#example1 (there is a 3D version just below it). It sounds like your goal is similar. – Russ Tedrake Aug 13 '21 at 10:58