Hi guys,
I want to simulate a robot that grasps a plug an unplugs it.
There are some questions about the general approach:
1. Regarding the grasping: How is grasping using a joint velocity/force accomplished?
Tutorial (motionPlanningAndGraspingDemo): by defining a joint velocity for the gripper: when does the gripping stop? I can see that there are force sensors implemented in the finger tips but do they influence the gripping?
Tutorial (ur4WithRG2Grasping): by defining both a joint velocity and a joint force: does the gripping automatically stop when the force is reached?
2. Regarding the modeling of the plug: Do you have a general idea on how to do this? I thought about first modeling plug and socket using some stl files. And then incorporating the contact by defining friction factors/sticky contact etc. in the material properties?
Thank you so much!
Best regards
Approach for simulation of robot unplugging a plug
Re: Approach for simulation of robot unplugging a plug
Hello,
what you are trying to do is really not trivial. Maybe you should first try with simpler tasks. Typically, grasping is very difficult to achieve in a realistic manner, and depending on the physics engine you are using, will require adjusting many parameter, and even adjusting the way the gripper itself operates (think of how a hand works: it is a complex task for the whole hand, and each finger has a control of its own + a global control). So oftentimes, grasping is emulated by simply detecting that the gripper is close to the object to grasp, and open, then attaching the object to the gripper via a force/torque sensor (i.e. rigidly attaching it), faking the grasping with the fingers.
The plug is also not trivial if you have experience with physics engines. Using meshes that interact with each other (e.g. friction) will give you very poor results, even if those meshes are convex. Better would be to use pure primitive shapes for that task (e.g. cuboids that are appropriately grouped in order to form a hole, or a pin for instance. If unpluggin a plug, you could also imaging the plug mounted on a prismatic joint that applies to force, or drag. When the plug is pulled enough, you could detach the plug from the joint and it would not be constrained anymore.
Cheers
what you are trying to do is really not trivial. Maybe you should first try with simpler tasks. Typically, grasping is very difficult to achieve in a realistic manner, and depending on the physics engine you are using, will require adjusting many parameter, and even adjusting the way the gripper itself operates (think of how a hand works: it is a complex task for the whole hand, and each finger has a control of its own + a global control). So oftentimes, grasping is emulated by simply detecting that the gripper is close to the object to grasp, and open, then attaching the object to the gripper via a force/torque sensor (i.e. rigidly attaching it), faking the grasping with the fingers.
The plug is also not trivial if you have experience with physics engines. Using meshes that interact with each other (e.g. friction) will give you very poor results, even if those meshes are convex. Better would be to use pure primitive shapes for that task (e.g. cuboids that are appropriately grouped in order to form a hole, or a pin for instance. If unpluggin a plug, you could also imaging the plug mounted on a prismatic joint that applies to force, or drag. When the plug is pulled enough, you could detach the plug from the joint and it would not be constrained anymore.
Cheers