How to properly Configure friction

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zhy149
Posts: 132
Joined: 14 Apr 2021, 20:18

How to properly Configure friction

Post by zhy149 »

Hello,

I want to perform two-finger gripper pick and place operations on cubes and other objects, but I'm having issues to properly configure frictions and other parameters so that the gripper can pick a cube or some other objects up. So, I'd like to know what is the principle and what parameters should I take care of when performing such actions? PS: I may also change the density of an object.
Thank you very much!

coppelia
Site Admin
Posts: 10339
Joined: 14 Dec 2012, 00:25

Re: How to properly Configure friction

Post by coppelia »

Hello,

object grasping is quite difficult to realize, since it involves various parameters, often specific to a given physics engine, and grasping/picking can work nicely with one engine and fail with the other engines. So it is an iterative task where you'll have to try to adjust those engine specific parameters, but also adjusting common parameters such as finger mass/inertia, and exerted torque/force, including motor controller is quite relevant.

As an example also, when performing two-finger picking, try to design your two fingers as a hand holding chopsticks, rather than two arms holding each one chopstick: in both situations you'll have two active joints, but grasping with the first method will be more stable:

Code: Select all

hand --> joint(center) --> finger1 --> joint(open/close) --> finger2
In above example, only one joint needs to be actuated to open/close the fingers. The second joint is only used to keep the two fingers centered in the hand. So one joint can be used in force/torque mode, while the other could be used in position control mode. Compare this with the other situation:

Code: Select all

hand --> joint1 --> finger1
     --> joint2 --> finger2
In above situation, it is more complicated to correctly control and synchronize the two joints.

Cheers

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