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How to modify the initial position/orientation of the model from MATLAB/Simulink?

ryuki
Hello
​
I am using Adams-MATLAB/Simulink co-simulation in order to design the controller for a robot.
And I want to change the initial position/orientation of the parts of the robot model from Simulink to find the best initial position/orientation for the robot control.​
 
Is it possible? and how can I do?
Or, do I need to change the model configuration manually everytime?
 
Thank you
 
  • 0
    You could use GCONS to drive the part motions and the GCONS are allowed to have a VARVAL() as an input. That could be state vars from Matlab, i.e. a desired position.
  • 0
    But doing this in one step at the beginning of the simulation might cause ADAMS/Solver to fail. The safe way would be to move the system in a continuous way during some initial time period.
  • 0
    Thank you for the good suggestions, @Martin Kieltsch​ and @Jesper Slattengren​ .
    ​
    I learned and tried using the general constraint (GCON), and I found that it allowed me to deal with the position as one of the parameters.
    The Adams plant was exported successfully.
    ​
    But, as @Jesper Slattengren​  said, the simulation was failed.
    Probably it is because the model suddenly moves to the first constrained position from the modeled position.
    ​
    I thought providing the initializing phase is a good idea, but I have a problem.
    My model is not fixed to the ground (Floating model).
    So, I found that it is still hard for me to move the system in a continuous way before main motion simulated.
    If I want to do so, I need to constraint one part to the ground during initializing, and after that unconstraint it.
    Also, I would like to set the joint torque as input signals and the joint angle and angular velocity as output signals of the Plant.
    So it is a little different with what I want to do.
    ​
    I understand that the point is how to change the design-time variables of the model from other software.
    For example, if you use design evaluation tools in ADAMS, you can set the design-time variables (i.e. coordination, mass property, spring coefficient etc) as the design variable.
    If is it possible to set the coordination of the markers belongs to each part at the initial position as state parameter like the design variable (DV) does, I think I can change it from Matlab.
    ​
    Is there a way to do so?
    ​
    Thank you.
  • 0
    Why so complicated?
    How about trying to use an initial amount of time like 1s or so to move everything to the right position and THEN start the controlling actions ?
    That's easily done by a simple step(time,0,0,1,1)*varval(xxx) in the GCON expression.
     
    Constraining a part to ground and release it at time x:
    Lock position by a GCON with if(time-1,DXYZ(marker on part, marker on ground),0,0)
    That'll make the expression go zero at 1s and thus "release" the part.
    Then do the same with WXYZ to "lock" rotations.
     
    Later on you just plot everything with a 1s offset and everything is fine.
     
    And yes, it's possible to have Matlab create ADAMS command files that can be read to modify models at design time.
    Just haven't used that with a Cosim and thus can't tell if/how it'd work.
  • 0
    I didn't know that the model will be released if I make the GCON ​to be ZERO.
    I will try and report it.
    Thank you very much.
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