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DL.2 Position feedback / simulation of movement ?

Hi,

Is there a way to get feedback from a DL.2 about its current position while it moves ?

I plan to use a DL2 to in an interactive system, much like a computer game. Graphical objects (characters of the game) shall be projected onto different surfaces of a room (they move based on a user's behavior). I have a DL.2 for the projection. The program I design will both render the object (the DL.2 projects that image as it is connected to the VGA output of the computer) and control the projector's motion via ArtNet.
While this setup works fine, the system does not work as expected when the character is projected while the DL.2 moves.
This is of course due to the fact that the projector has a considerable mass and can not turn to its new position instantly. Therefor it is necessary for my application to know where the projector is pointing at at any given moment (every 1/60 second, as I'm rendering 60 frames per second). Only this way the object can be rendered in the correct place within the projected image so that it gets projected in the correct spot while the projector moves.

There are basically three options for me:

1. There is a way for the fixture to give feedback to the controlling computer about how far it has come since the command to change to a new position was sent and somebody lets me know how to get this information.

2. I could simulate the fixture's motion, as I know the position value I sent to it as well as the previous positions. This however requires some knowledge about how the controller inside of the device controls its motors, how it accelerates and decelerates, what the maximum speed is etc.
It can be very tedious to figure that out by trial and error, not to mention that it may not be accurate enough this way. It certainly would help to hear from a Highend Systems engineer how they control the DL.2's motors. I just hope that is not considered a classified trade secret.

3. I would have to build some hardware device that measures the position changes (eg. by following the signals on the stepper motors) or a completely new controller for the DL2's pan and tilt function.


For obvious reasons I would like to avoid option three, especially the more drastic approach of replacing and redesigning the controller.

I also am not optimistic that there is a way to get the feedback from the device, as I have searched a lot for it and this feature simply doesn't seem to be necessary for the usual applications.

So I'm really hoping to get some information that may help me to simulate the motion of the fixture accurately.

Regards,

Jochen
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  • 0
    Jochen,

    As you surmised, there is no way to read out the current position of the fixture.

    In your situation I would suggest using the M-Speed channel for the Motion. This will allow you to specify the time that it makes the move in. The best thing to do is pick a time that is a bit slower than what the fixture can actually move in that way it will then slow down to match the time you have specified. This makes the calculations much much easier for you.

    Otherwise predicting our motion time gets a lot more complicated as we have different accel and decel curve profiles for different situations.
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  • 0
    Jochen,

    As you surmised, there is no way to read out the current position of the fixture.

    In your situation I would suggest using the M-Speed channel for the Motion. This will allow you to specify the time that it makes the move in. The best thing to do is pick a time that is a bit slower than what the fixture can actually move in that way it will then slow down to match the time you have specified. This makes the calculations much much easier for you.

    Otherwise predicting our motion time gets a lot more complicated as we have different accel and decel curve profiles for different situations.
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