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  1. Data Management
  2. DM-25658

Fix the Following Error in the Rotator Simulink Model

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      Description

      Fix the following error in the rotator Simulink model. There is the problem of physical model in plant that the rotator's position will differ from the related position command gradually until the trigger of followingError (the difference >= threshold) and this stops the motion of rotator. According to the observation, this happens if the rotator moves in the negative direction.

      In the following figure, there are two targets: (1) position=1.2 deg and velocity=0.01 deg/sec and (2) position=1.5 deg and velocity=-0.01 deg/sec. The total simulation time is 20.1 sec. There is no big difference between the position command and position. The error of noNewTrackCmdError after the slew of the second target is triggered as expected.

      However, if the second target has position=-1.5 deg and velocity=-0.01 deg/sec, the following error is triggered while the rotator turns the direction to slew to the second target:

        Attachments

        1. 2016-06-01 LSST CDR - Control System Design and Analysis_1.pptx
          25.09 MB
        2. DahlModel.nb
          36 kB
        3. moveNegativePosition.png
          moveNegativePosition.png
          54 kB
        4. movePositivePosition.png
          movePositivePosition.png
          52 kB
        5. moveToNegativeFromNonZeroPoint.png
          moveToNegativeFromNonZeroPoint.png
          58 kB
        6. moveToNegativeFromNonZeroPointNoCoulombFriction.png
          moveToNegativeFromNonZeroPointNoCoulombFriction.png
          56 kB
        7. moveWithLowCoulombFriction.png
          moveWithLowCoulombFriction.png
          57 kB
        8. neg_slew_failed.jpg
          neg_slew_failed.jpg
          82 kB
        9. trackAdapNoNewTrackCmd.png
          trackAdapNoNewTrackCmd.png
          62 kB
        10. trackFollowingError.png
          trackFollowingError.png
          46 kB
        11. trackPosAndNegTargets.png
          trackPosAndNegTargets.png
          59 kB
        12. trackPosAndNegTargets2.png
          trackPosAndNegTargets2.png
          51 kB
        13. trackSolverAdap.png
          trackSolverAdap.png
          73 kB

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            Hide
            tribeiro Tiago Ribeiro added a comment -

            Can you clarify one thing for me please? How does the model compute the gravity compensation? I imagine it will need to know the inclination of the system to be able to compute it. If this is the case, where this information is coming from on the model and on the real system? 

            Show
            tribeiro Tiago Ribeiro added a comment - Can you clarify one thing for me please? How does the model compute the gravity compensation? I imagine it will need to know the inclination of the system to be able to compute it. If this is the case, where this information is coming from on the model and on the real system? 
            Hide
            ttsai Te-Wei Tsai added a comment -

            Tiago Ribeiro Please see the page 3, 18, and 19 for the discussion of gravity in:
            2016-06-01 LSST CDR - Control System Design and Analysis_1.pptx

            These are the only information I could found.

            Thanks!

            Show
            ttsai Te-Wei Tsai added a comment - Tiago Ribeiro  Please see the page 3, 18, and 19 for the discussion of gravity in: 2016-06-01 LSST CDR - Control System Design and Analysis_1.pptx These are the only information I could found. Thanks!
            Hide
            tribeiro Tiago Ribeiro added a comment -

            Uhm, ok... but none of them specify where the inclination is coming from. I think it is ok for now but we should probably investigate this to make sure the model and the real thing are getting and using this information properly. 

             

            Show
            tribeiro Tiago Ribeiro added a comment - Uhm, ok... but none of them specify where the inclination is coming from. I think it is ok for now but we should probably investigate this to make sure the model and the real thing are getting and using this information properly.   
            Hide
            ttsai Te-Wei Tsai added a comment -

            I totally agree with this comment because the information of MOOG documents is very limited. I should document it when I do the debug of the gravity model (I do not know when it will be). Thanks!

            Show
            ttsai Te-Wei Tsai added a comment - I totally agree with this comment because the information of MOOG documents is very limited. I should document it when I do the debug of the gravity model (I do not know when it will be). Thanks!
            Hide
            tribeiro Tiago Ribeiro added a comment -

            Great work done by TeWei and Mike on this ticket. I think it's good to go, we will have some additional work to follow up but it is looking good. 

            Show
            tribeiro Tiago Ribeiro added a comment - Great work done by TeWei and Mike on this ticket. I think it's good to go, we will have some additional work to follow up but it is looking good. 

              People

              Assignee:
              ttsai Te-Wei Tsai
              Reporter:
              ttsai Te-Wei Tsai
              Reviewers:
              Tiago Ribeiro
              Watchers:
              Te-Wei Tsai, Tiago Ribeiro
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              2 Start watching this issue

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