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Modifying a transformation based on yaw-pitch-roll or phi-theta-psi

  1. Feb 14, 2014 #1
    [I've tried asking this question on math.stackexchange.com, but haven't got any responses, so I thought I'd try here]


    I’m building a model in a 3D simulation program (MSC Adams) and part of that model is a triangular platform which can translate and rotate in the virtual world, as shown in the 2 images below:

    Frame1.png

    Frame2.png

    There are some markers on this platform that, when it is at its home orientation, are aligned with the global axis system (which is the orientation of markers A, B and C in the first image). These markers move and orient with the platform so that they represent the platform’s orientation with respect to the global axis system.

    Now, I have a special marker (TOP_ORIGIN) that is coded so that it is always at the centroid of the corners of the triangle that form the platform (average of the coordinates A, B and C). What I’m trying to do is to also constrain the orientation of the marker as follows:

    • The X-Y plane is the same as the platform’s plane with the Z axis putting “up” away from the model.
    • The angle between the X axis and the vector XA is set to an angle, theta, which I calculate elsewhere.
    • The software gives me two ways of getting and setting the orientation of objects: yaw-pitch-roll (rotation about Z then rotation about the new Y, then rotation about the new X) and phi-theta-psi (rotation about Z then rotation about the new X, then rotation about the new Z).

    How can I apply these transformations to get the marker to the orientation I want?
     
  2. jcsd
  3. Feb 20, 2014 #2

    FactChecker

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    The yaw-pitch-roll transformation looks fairly standard but your description of the phi-theta-psi transformation doesn't look right. Two Z rotations is unusual, and not what I would expect from "phi-theta-psi." (P.S. I can't see what axes you are talking about because the pictures are very cluttered.)
     
  4. Mar 10, 2014 #3
    I am not sure what you are asking, amrbekhit. Do you want to convert between yaw-pitch-roll and phi-theta-psi? Can you clarify your question?
     
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