How to achieve grasping an object in simulation?

[LuserBen]

Hi, I see that robotiq grasps the object well in gazebo in your models. Do you use gazebo_grasp_plugin?
I use gazebo_grasp_plugin to help robotiq pick an object in gazebo, but it usually has no effect.
So can you tell me how you solved it. Thank you.

[neka-nat]

Hi,
Yes. I also use gazebo_grasp_plugin and I set the plugin parameters so that the robot can grasp.
In this repository, it is set as follows.

neka-nat/robotiq_85_gripper@8a41bd1

[LuserBen]

Hi, @neka-nat. Thanks for your sharing.
I find the reason that the issue is not on the parameters, maybe on the plugin.
If the object is in the middle of the gripper(x = y, because I get the object state by gazebo service /get_model_state, there is no position error of the object), left finger and right finger will arrive target pose at the same time but without counting contact points in 'close' process. So I add a position offset (x != y), one finger will contact the object first, then another finger. It works.

[neka-nat]

Did you actually try to experiment with varying the parameters?

I don't remember such a bug happened.
However, grasping with the plug-in is very unstable and it often happened that the robot could or couldn't grasp at the same position.

[LuserBen]

@neka-nat
At the begining, the robot get the object state by gazebo service /get_model_state, gripper can not grasp the object. So I tried different parameters, but it still did not work. Then I get the object position by kinect v1, position errors lead to x != y, this time it works.
So I add a position offset (x != y), one finger will contact the object first, then another finger. It works.
You can have a try, object (for me object is cube, so problem is obvious) in the middle of two fingers or not.
I send a comment in JenniferBuehler/gazebo-pkgs#9. floor 51.