How to do flexible tail simulation in water environment

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el17al
Posts: 2
Joined: 07 Dec 2017, 14:38

How to do flexible tail simulation in water environment

Post by el17al » 13 Mar 2018, 11:54

Dear administrator,

I am doing a project to simulate the tail motion in a water environment. I divided the tail to several segments and each segment has 2DOF. In all the segments, only one leading vertical joint is in the Torque/Force mode. The rest of joints are in the Passive mode (Hybird Operation) with spring-damping factors,
I looked at the ACM-R5.ttt. i think that the buoyancy and drag force setup are for the simulation, but not for real water environment. I like the velocity matrices' calculation and the commands that are used to send data from the initial segment to the following body.
However, all the joints are in the Torque/Force mode. How to do that kind of simulation for Passive mode joints?

Thank you,
Ang Li

coppelia
Site Admin
Posts: 6867
Joined: 14 Dec 2012, 00:25

Re: How to do flexible tail simulation in water environment

Post by coppelia » 14 Mar 2018, 07:47

Hello,

difficult to imagine what you are trying to achieve exactly. But why do you have only a few items in force/torque mode and the rest is passive? Passive items won't be taken into account for dynamic simulation. For instance:

dynamicShape1 --> torqueJoint --> dynamicShape2 --> passiveJoint --> staticShape

In above example, you can add some auxiliary force/torque to dynamicShape1 and dynamicsShape2. For those two shapes you can also read their dynamic velocity with sim.getVelocity (i.e. the velocity computed by the physics engine).

For staticShape, you will have to read the velocity in a different way since that shape is not simulated by the physics engine (e.g. with sim.getObjectVelocity). Moreover, you can't add auxiliary forces/torques to that shape. You will have to add it to its parent shape (but you'll have to transform the torque correctly for that).

Cheers

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