Vrep simulation of sit-to-stand motion

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Lil_macha
Posts: 6
Joined: 03 Mar 2020, 13:21

Vrep simulation of sit-to-stand motion

Post by Lil_macha »

Hello,

I am still relatively new to VREP and I would like to seek assistant with my current task at hand. I am currently trying to simulate a person with a sit-to-stand motion using 'Working Bill' . How can i achieve this?

So far, I noticed that by changing the child script i can change the position and orientation of Bill but he is not in a sitting position as accurately as i hoped it would be.

I tried using 2 different starting positions :
A. He is in a standing position (as default) but only squats down awkwardly without completing the motion when running the simulation.

B. His parts are rearranged so that he assumes a sitting position similar to 'Sitting_Bill' but then awkwardly squats down when running the simulation.

> Any advice. Regards

coppelia
Site Admin
Posts: 7911
Joined: 14 Dec 2012, 00:25

Re: Vrep simulation of sit-to-stand motion

Post by coppelia »

Hello,

modifying working Bill can work, but then you need to carefully check how the model operates, since there are several IK calculations (damped) that handle postures and/or positions of different body elements. A probably better option would be to use sitting Bill, memorize all joint positions, then modify the model so that it stands, then alternate from the sitting joint states to the standing joint states, with some appropriate interpolation between those two states (and additionally maybe also some velocity ramp during that movement).

Cheers

Lil_macha
Posts: 6
Joined: 03 Mar 2020, 13:21

Re: Vrep simulation of sit-to-stand motion

Post by Lil_macha »

Hi, thanks for the reply.

Can I request some justification on the following, ( just so I can get a clearer picture of your idea ) :
1. How do I modify the sitting_bill model to stand, do I edit the child script, do i add tips and targets to the build, or are there any other methods I'm not aware of?
2. What do you mean by alternating between sitting joint states to standing joint states and how?

Regards.

coppelia
Site Admin
Posts: 7911
Joined: 14 Dec 2012, 00:25

Re: Vrep simulation of sit-to-stand motion

Post by coppelia »

The sitting Bill has many joints. Try to change the angle of those joints and you will see. The idea is to then programatically change the joint angles to give you a smooth sit-stand-sit-stand movement. The RML functions might come in handy. Have a look at this scene for examples how to use the RML functions.

Cheers

Lil_macha
Posts: 6
Joined: 03 Mar 2020, 13:21

Re: Vrep simulation of sit-to-stand motion

Post by Lil_macha »

Thanks for the reply.

The RML really helped

Regards.

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