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Flight Sim Motion Enhancement - Projector Articulation - Page 2

DIY Motion Platform Articulated Projector

DIY Flight Sim Projector Articulation Mechanism

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Articulation Mechanism

 

The projector articulation mechanism I opted for is shown on the CAD image right (click image for bigger picture). The projector is "ceiling" mounted to the underside of a support plate which is pinned at the rear and supported at the front by three tie rods. The tie rods form a partial Stuart mechanism driven by the three RC Servos. Controlled movement of the servos can induce vertical, horizontal and tilt movements of the projector which are reproduced and magnified at the projected image. As you can see this particular mechanism is very simple and lends itself well to DIY builds.

 

The required range of motion of the servos is small and although I've used Hitec HS-515BB units I think that servos with a smaller stroke but higher resolution operating range could be an improvement as this would contribute to further smoothness in the projector motion.

 

 

Although simple to build the mechanism must be constructed with some precision to ensure that the movements in the three degrees of freedom are clean and largely uncoupled. The precision is achieved through accurate positioning of the servos, ties rods and projector.

 

I've drafted a couple of engineering drawings which show the mechanism assembly and part dimensions. The pdf's are password protected and the password is: Projector. If you are interested in trying this build make sure to read the notes on the drawings carefully.

 

BFF Motion Driver Projector Articulation

Mechanism Assembly Drawing

BFF Motion Driver Projector Articulation

Mechanism Part Details

 

Servo Control

 

Servo ControllerThe servos are driven from the V2 BFF Motion Driver through a Pololu Servo Controller. I've used both their 8 and 16 channel servo controllers with satisfactory results. For details of the servo controller wiring and how to connect the servos to the controller read the User's Guide provided with the controller.

 

There are one or two important points to make here.

  • The servos should be connected to channels 1, 2 and 3 on the controller if driven by the V2 Motion Driver. The Assembly drawing above shows how the servos are numbered on the mechanism.

  • I powered the controller from a 12V battery using a Dimension Engineering Sport BEC for the servo supply and with a separate direct tap from the same battery for the controller's logic supply.

  • The DTR/RTS reset enable jumper on the 8 channel Pololu controller should be removed.

  • IMPORTANT - Use a 12V battery dedicated to this system - do not tap into batteries already used for driving a motion platform or otherwise connected through motor controllers and electronics to the same driving PC!

In operation the servos will audibly "chatter" as they support and move the projector - if you fly with headphones this will not be a problem.

 

Projector Motion Drive Software

 

BFF Motion Platform Driver SoftwareThe drive algorithms for the projector motion have been incorporated into V2 of the BFF Motion Driver software. The motion cues for the articulation mechanism are output on a separate Serial COM channel from the main motion platform cue output and can be used with or without the main drive as is required. For operation of the BFF Motion Driver see the driver web pages.

 

The status of the visual system cues are reported in the driver window and adjustment sliders are provided for fine position set up and for simple scaling of the projector motion cues see below). The cues are customisable in much more detail by adjusting parameters in a configuration file - see the User Manual for more details.

 

The algorithms use live flight data extracted from the flight sim to calculate horizontal, vertical and tilt movements of the projected display. The motions are similar in some respects to those found with the dynamic head movements feature of MS FSX but they incorporate a number of different parameters and, importantly, the system causes the whole visual frame to move rather than causing head motion just within a fixed visual frame. This is a key element of the motion immersion effect.

 

The display horizontal movements are derived from the lateral and yaw movement of the aircraft, display vertical movement is derived from heave and pitch motion and tilt from aircraft roll. For use with FSX I find that it is best to disable the head movement within the sim with the exception of a reduced amount of fore/aft acceleration effect. The driver will work with FS9 also and I'm currently working on an X-Plane version.

 

To get the system operating the output COM port is set in the config file and the servo controller connected to the COM port on the driver PC. The servo motion cues become active once the Motion Driver is running and switched to "Drive" mode. The sliders can be used to make fine adjustments of the display position and to apply simple scaling to the movement magnitudes - more detailed manipulation of the cues (say to sharpness of response, saturation/cutoff levels etc) is done by altering the config file parameters.

 

 

Possible Uses in DIY Rigs

 

I am currently using the projector articulation system with the motion Platform 3 which has a single projector display. I think it would be also worth experimenting with as an enhancement to simple fixed desktop flight sim setups which use a single projector to display the main screen against a wall or screen. Other combinations of projector setups, say with mirrors or in different orientations should also be possible. I think this is a really interesting technique that could add interesting motion effects at fairly low cost to a number of flight sim set ups.

 

If you do have a shot at implementing the method do let me know how you get on. The motion driver is in the early stages of it's use and I can consider improvements and additional features if needed - for example to drive other than Pololu servo controllers.

 

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Page Published 22nd December 2008

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