Hi,
I have been trying to control a simple double bar pendulum in torque mode. The system involves 2 rectangular bars, 1 base and 2 revolute(continuous) joints. I have made a controller plugin for this and i am sending the gravity compensation torques which has to be applied at the joints to maintain the balance. There are two strange things which are happening,
1. The amount of torque required to maintain the balance of the pendulum is exactly twice of which i compute with my model. I am using the same model for visual and dynamic (for each bar), but in the case of visual the mass is very less. So i don't understand why it requires twice the amount of torque.
2. I am able to balance the pendulum only when the base is kept static, when i uncheck the static option for base and run the simulation, the 2 bars are maintained in position, but the complete system tilts to the right side and falls. The CoG of the complete system remains within the base only and there is no possibility to have a tilting moment, but still this happens. I need this one to be working, as i am planning to use it for controlling other floating base systems like Humanoids.
It would be great if you can give me an explanation for the first one and suggest me some solution for the second one.
In the below attached link, i have included the following things
1. System setup (image)
2. Static simulation (video)
3.Dynamic simulation (video)
https://www.dropbox.com/sh/v2glu3kgidb0 ... BCrra?dl=0
with regards,
Rajesh S
Torque Control for floating base systems
Re: Torque Control for floating base systems
Hello Rajesh,
difficult to say... can you post the scene?
Are you sure the COM of the 3 elements are correctly placed? Did you try to see if the results are different when using a different physics engine (e.g. Vortex)?
Cheers
difficult to say... can you post the scene?
Are you sure the COM of the 3 elements are correctly placed? Did you try to see if the results are different when using a different physics engine (e.g. Vortex)?
Cheers
Re: Torque Control for floating base systems
Thank you for your reply.
I am importing the model using URDF plugin and i found some mistake in my urdf file, which offsets the COM position of the links in V-REP. So, the error indeed was due to the COM position offset.
Now i have corrected the urdf file and the COM position seems to be fine, but i am not able to balance the pendulum. May be i have re-tune the PD gains. I will get back to you after doing that.
Thank you again for your suggestion.
I am importing the model using URDF plugin and i found some mistake in my urdf file, which offsets the COM position of the links in V-REP. So, the error indeed was due to the COM position offset.
Now i have corrected the urdf file and the COM position seems to be fine, but i am not able to balance the pendulum. May be i have re-tune the PD gains. I will get back to you after doing that.
Thank you again for your suggestion.