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aileron/rudder stick throws for RTH, so it was recommended to use only limited stick movement. However with the Guardian, the RTH limits are
set as angles, as described below, and giving the full stick movement during the wizard is necessary.
2.
For initial testing, we recommend turning on “Servo Deflection Display”. When stabilization is turned on, the present Overall Gain setting is displayed as
“G” in the servo deflections, and the present pitch and roll of the model are also displayed. Further, we recommend enabling the Artificial Horizon display,
which will help to validate that the Guardian is mounted and operating correctly.
3.
Choose your airframe type with the “Choose Model Wing Type” menu, by selecting either “Fixed Wing” or “Elevon” type. Both of these modes require
that your radio supplies un-mixed Aileron/Elevator signals. Mixed inputs to the OSD Pro are not supported with Guardian Stabilization enabled.
Note that the OSD Pro supports mixed elevon inputs when stabilization is disabled, but requires unmixed inputs when stabilization is enabled, to provide the
best stabilization experience.
4.
Enable Stabilization by setting the “ Stabilization / Elevn Mixing On?” option in the Radio Control Configuration menu to “Yes.” Warning: Never turn
this option off or on during flight if you have an elevon model, since the mixing mode will change! Adjust the stabilization gain setting instead.
5.
Orient your model as it would be during level flight. If the Artificial Horizon display is not centered on the Home indicator or is tilted, click “Reset Level
Pitch and Roll.” This step will minimize the impact of minor mounting errors with your Guardian.
6.
Configure the “Max Stab Pitch/Roll Normal” angles that the Guardian will allow your airplane to attain. For greater maneuverability, set these values to 60
degrees. For easier flight behavior, set them to around 40 degrees.
Warning: Setting these values to greater than 60 degrees will result in very responsive flight characteristics from your airframe. Going into
maneuvers that your airframe is incapable of sustaining will still result in a stall! Additionally, setting the max angles too low may make your
airplane difficult to turn.
7.
If you will be using the Return to Home feature, adjust the “RTH” Max Pitch/Roll angles. These parameters act the same as the Stabilizer Pitch/Roll angles,
but are only used for limiting the Return to Home. It is recommended that these values be around 25 degrees, depending on user preference, airframe
stability and wind conditions. Once again, a larger angle will result in a more maneuverable RTH, with a smaller turn radius, but may result in oscillations
depending on the RTH gain values.
Warning: A smaller number will result in smooth RTH behavior, but may prevent your airframe from returning in strong wind conditions or if the
Guardian is mounted improperly. It is recommended that you test RTH after changing these values.
8.
It is recommended that your Safety Mode RTH gain settings be returned to their default values, if you have changed them in the past, when flying without
the Guardian. When the Guardian is properly configured, most airframes should work with the default RTH gains.
Note: If the RTH does not turn quickly enough, increase the Max Stab Roll RTH value before changing the RTH gains. Do not exceed 35 degrees.
For further information, see the RTH section of the OSD Pro manual.
9.
The Stabilizer Pitch/Roll and Overall gains can be left at their default values of 5, 5 and 8 respectively. You will tune these gains later.
The Servo Analysis Wizard
Since Guardian Stabilization interprets your stick movements as attitude commands, rather than direct servo deflections, it is important to tell it how far your RC
controller’s sticks move in the pitch/roll axes. At the same time, the Guardian needs to know the trim conditions of your plane as well as the centered position of your
control stick. The Servo Analysis Wizard figures this out for you.
When requested to "Set Sticks for level flight,” your control stick should be centered (trimmed for level flight with stabilization turned down) and your throttle set to its
cruise level. The throttle levels are not required by the Guardian, but are required for Return to Home. Please see the OSD Pro manual for information regarding the
throttle / failsafe features of the Servo Analysis Wizard.
When asked to
"Mov Rudder/Aileron Stick Left," make sure to assert maximum servo deflection on your RC controller. The same should be done when asked to "Mov
Elev TX STICK Back(Climb).” These steps tell your OSD Pro the maximum servo deflections allowed for Guardian Stabilization. If the stick is not moved to its
maximum extents for this portion of the wizard, your control commands may be clipped, impacting performance and stability.
Note: After trimming your airplane on your RC controller, it is important to run the “Reset Cruise Sticks/Throtl” to inform the controller of the change,
otherwise Heading Hold and Center-Stick Only Stabilization may be impacted.
Reset Cruise Sticks/Throtl
It can be cumbersome to re-run the Servo Analysis Wizard after changing the trim of your airplane. To let your OSD Pro know about changes to trim, it is important to
run the “Reset Cruise Sticks/Throtl” command. This resets the center position of your control stick, as well as the cruise position of your throttle, ensuring that features
like Heading Hold and Center-Stick Only Stabilization work optimally.
Tuning Stabilization Gains
Stabilization Theory
The Guardian Stabilizer works by measuring the orientation of your model airplane relative to the local direction of Earth’s gravity. In addition, it interprets pitch and
roll attitudes commanded by the servo signals received through your elevator and aileron channels respectively.
With this information, it is able to determine the error between your requested flight attitude and your plane’s true orientation. By passing this error through a controller
algorithm and sending it as servo commands through the elevator and aileron outputs on your OSD Pro, the Guardian can turn your squirrely model into a smooth-
flying wing on rails!
Each axis has a separate control gain used to tune stabilization. These are defined by, “Stabilizer Pitch Gain,” “Stabilizer Roll Gain” and “Stabilizer Overall Gain.”
The Pitch and Roll Gains are scaled by the Overall Gain to provide individual axis tuning while also providing On-The-Fly adjustment depending on conditions and
aerodynamic performance.
In general, the higher the gain, the more responsive and resilient your plane will be to disturbances such as wind, balance and trim issues. Tuning the gains too high
however may result in oscillations of the airframe. It is recommended that the Overall Gain be used to tune the airframe until it oscillates and then be turned back
down. This will ensure the best performance while preventing future oscillations.
