Copyright 2013 Eagle Tree Systems, LLC Page 7
Figure 7 – Guardian Gain Control Dials
Figure 7A - Guardian Master Gain Control
When in 3D Mode, Orientation Stabilization is used in the Pitch, Roll and Yaw axes to keep your model on track. When in 2D Mode, Orientation Stabilization is
only used on the Pitch and Roll axes, leaving the Yaw axis (Rudder) only with Rate Stabilization. This will make the Rudder appear to be stabilizing less than the Elevator
and Ailerons (or Elevons) in 2D Mode. This is expected behavior.
Individual Axis Gain Dials
The gain control dials on the Guardian can be used for tuning the individual axes on your airframe. In addition,
they allow for the reversal of the direction of stabilization servo travel. When a dial is centered (with the
“double-dot” dial indication facing upwards, as shown in Figure 7) the gain for that axis is set to zero. This
effectively disables stabilization on that axis.
When a dial is rotated away from its centered position in the clockwise direction, the gain for that axis is
increased, and the stabilization deflection direction is set to normal. If the dial is rotated counterclockwise from
its centered position, the gain will be increased as well, but the stabilization deflection direction will be reversed.
This allows for stabilization to be tuned for any airframe, regardless of servo orientations.
If you have difficulty seeing the double-dot indication on the dials, you can either gently rotate the dials
counterclockwise and clockwise to find the approximate center point, or you can use the PC software to visualize the dial settings on your computer screen.
Stabilization “Master Gain” Control
The Master Gain control increases or decreases the effective amplitude of the Pitch/Roll/Yaw gain dials and serves as a way to easily tune all
three. If you have an RC controller that has a free analog knob or slider, this can be mapped to the Gain channel to allow for overall in-flight
stabilization gain adjustment. The higher the gain knob setting, the stronger the Guardian’s stabilization effect will be.
Another way to think about this is that it is similar to a graphic equalizer and volume control on a stereo. The individual gains are similar to the
sliders on the equalizer, while the Master Gain is similar to the overall volume control.
Though not required, ideally the Gain wire from the Guardian will be plugged into a channel controlled by a knob, slider or switch on the
transmitter. If you do not have a knob or slider on your transmitter than can be used for the Master Gain function, you may use a two or three
position switch to provide low/high or low/mid/high gains by adjusting the travel limits in your transmitter. If you have no available channel for the Gain wire, you may
leave it disconnected. In this case, the gain range of the individual gain dials is reduced to slightly
less than half of the maximum possible gain to reduce the possibility of encountering oscillation.
See the figure 7A below.
Setting the Pitch/Roll/Yaw gain dials on the Guardian and the Master Gain control on the
transmitter at maximum provides maximum stabilization.
Too high of a gain setting can result in oscillation: see the Oscillations section for
more information on this. Setting Master Gain control to the minimum will lower the
overall gain to zero, while positions in between will yield proportional gain. Lowering the
individual gain dials on the Guardian will lower the gain for that axis only and allow fine tuning.
This might be desirable if, for instance, oscillation is encountered on one axis but not the others.
One possible strategy for setting gains would be to set all three of the individual gain control dials
to maximum and the master to zero. While flying the plane with the Guardian engaged, slowly
turn up the Master Gain and watch for signs of oscillation. If oscillation is encountered, back
down the Master Gain until it ceases. With the plane on the ground, reduce the setting on the
potentiometer for the axis for which oscillation was observed. Repeat until the plane can be flown
with the Master Gain in its middle position without oscillation. If you have a plane with a wide
speed range, such as a hovering 3D aircraft, using this procedure using only the mid range on the
Master Gain will allow you later to turn it even higher when hovering or performing other slow
speed aerobatic maneuvers as oscillation is seldom a problem under these conditions.
If continuous oscillations are experienced with the Master Gain wire disconnected, switch
the Guardian off immediately with the Mode switch if necessary, and land. On the ground, reduce
the gain dial for the oscillating axis as described above.
If connecting the Gain channel on a model where the Guardian had been previously tuned without it, ensure that the position of the Master Gain knob, slider or
switch is set at slightly less than the centered position (see figure 7A) to prevent the possibility of strong oscillations on takeoff.
Oscillations
Sometimes, when the controller gains are set very high or if your model flies at a very high airspeed, oscillations can develop. If oscillations occur, turn down the Master
Gain control or the gain dial for the axis that is oscillating (i.e., the Pitch axis), until the oscillations stop. Other causes of oscillations include mechanical slop in control
surfaces and slow servos. If your model has digital servos, higher gain values may be made possible by increasing the Output Servo Pulse Frequency. See: List of Menu
Features and Options: Output Servo Pulse Frequency.
Oscillation Suppression
To help reduce pilot workload, the Guardian will automatically scale down the Overall Gain when it detects oscillations. To do this, it incrementally scales the Overall Gain
down to a minimum of 50% of its currently set value. After the oscillations are eliminated, it will slowly increase the Overall Gain back up to 100% of its set value or until
oscillations are detected again, whichever comes first.
If oscillations occur and subsequently disappear, it is recommended that you slowly reduce your gains to prevent this from happening in the future.
Do not increase the Overall Gain after an oscillation has been suppressed, since doing so will only cause more oscillations until the Oscillation Suppression is unable to
reduce the Overall Gain sufficiently to be effective.
Preventing Damage to Your Model
In-Air Recovery
The Guardian is a great tool for beginners looking for a safety net in case of lost orientation or control, however switching to 2D Mode with a combination
of too-high airspeed and gains may cause damage to the airframe.
