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Static equilibrium between rigid/modal simulation

Hello,
 
The system i simulate is a propelled vehicule that is composed of two parts : first is a rigid part, the second is a flex part.
 
Until now, i started the simulations with a sim/statics command, in modal representation => the result is the nodes of the flex part move to the equilibrium positions before the transient simulation.
Good idea (or not ?...) : i use a fixed joint, only during the sim/statics command, to link my vehicule with the ground. Without the joint, the static analysis is not successful. Note that the 2 parts are linked by bushings.
 
But now, due to controls consideration, i need to do few seconds of simulation before. As there is no interest to simulate this part of the simulation in modal mode, i tried to :
  1. realize the simulation in rigid mode during few seconds
  2. then activate modal representation of the flex part
  3. realize the sim/statics command in order to obtain equilibrium of the flex part,
  4. realize the rest of the simulation
But step 3 is never successfull, even playing with activate/deactivate commands of the fixed joint and bushings.
 
Do you have any advice please ?
 
Thanks for your help.
Parents
  • I don't think you got the important part of what I was trying to convey.
    I assume that the vehicle moves in the initial dynamic simulation?
    Then when you activate the fixed joint, that will pull it back to the initial position and literally tear the system apart.
    So your script MUST look like this (assuming your fixed joint has id=13, the i_marker has id 42 and the j_marker has id 43.
    deactivate/joint,id=13
    simulate..... !initial dynamics
    ! do whatever you need to do to activate the modal representation
    marker/43,qp=0,0,0,reuler=0,0,0,RM=42 ! Move marker 43 (on ground) to coincide with marker 42 (on flex body)
    activate/joint,id=13
    sim/stat
    simulate.........
     
     
Reply
  • I don't think you got the important part of what I was trying to convey.
    I assume that the vehicle moves in the initial dynamic simulation?
    Then when you activate the fixed joint, that will pull it back to the initial position and literally tear the system apart.
    So your script MUST look like this (assuming your fixed joint has id=13, the i_marker has id 42 and the j_marker has id 43.
    deactivate/joint,id=13
    simulate..... !initial dynamics
    ! do whatever you need to do to activate the modal representation
    marker/43,qp=0,0,0,reuler=0,0,0,RM=42 ! Move marker 43 (on ground) to coincide with marker 42 (on flex body)
    activate/joint,id=13
    sim/stat
    simulate.........
     
     
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