On 29-Jun-05, at 10:59 AM, Douglas S. Blank wrote:

We are finalizing our Python Robotics software for the summer, and I was wondering about the state of the grippers in Gazebo and Stage (not the latest CVS versions necessarily, but the last semi-stable versions).

In Gazebo 0.5.2, I have tried to manually pick up a block using the Pioneer simulated gripper in pioneer2dxGrip.world. If I rotate the robot, the block falls from the gripper. Is there a way to increase the pressure to better grip the block? Can you stack the blocks, or is it just me?

In Stage 1.6.4, the gripper now moves, but it appears that objects cannot be picked up. Is this correct? If so, what needs to be added so that objects can be picked up and moved? What needs to be added to consume them?

If I recall correctly (SF seems to be down right now), there isn't a Stage 1.6.4 release yet, and grippers only exist in CVS. I'm working on gripping and pushing whenever I get a chance. Most things are in place, but the logic of when and how to push objects is still to be worked out. In Stage 1.3.x  the gripper paddles didn't interact with the world at all,. I'm trying to do a little better this time, but the motion of multiple bodies gets nasty very quickly. 

As for consuming, I'm implementing a gripper stack with configurable size. Stack size 1 is a regular gripper. Stack size n > 1 means that you can grab up to n objects and drop them in reverse order of grabbing. Stack size -1 means unlimited stack size, so you can 'consume' objects indefinitely. 

I estimate the grippers will be useable in another 2 or 3 weeks, unless someone chips in. I have only a few hours a week to work on Stage, and a couple of other features to finish first.


Thanks for any information (or patches :),


Douglas S. Blank,         Assistant Professor
dblank@brynmawr.edu,            (610)526-6501
Bryn Mawr College,   Computer Science Program
101 North Merion Ave,       Park Science Bld.
Bryn Mawr, PA 19010  dangermouse.brynmawr.edu

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