Copyright © 2009-2012 Eagle Tree Systems, LLC
http://www.eagletreesystems.com
Page 15
Safety Mode/Return to Home Information
Please read this entire section, and understand the function and limitations of the modes, before enabling a safety mode!
Important Safety Mode Information
Please read the following information about RTH, before proceeding.
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Return To Home (RTH) is an advanced feature, and is used only at your own risk.
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WARNING: Since RTH may increase the throttle setting, YOUR MOTOR MAY START SUDDENLY WITH YOUR MODEL ON THE
BENCH, OR ON THE GROUND, WHEN RTH IS TRIGGERED! RTH attempts to avoid starting the motor in this situation, by examining the
speed and altitude of the model. But, if the GPS or other sensors are misreporting altitude and/or misreporting speed, RTH could still start the
motor on the ground. ALWAYS ASSUME THAT THE MOTOR MAY START AT ANY TIME, WHEN RTH MODE IS ENABLED!
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It’s important that you turn your transmitter on before powering up the OSD Pro, if you plan on using advanced features such as RTH. The OSD
Pro needs to receive signals from your receiver during startup, or some features such as RTH may not work correctly. If the signals are not
received, the OSD Pro will put up the message “Aileron or Elevator Undetected” during startup, indicating the receiver was not detected.
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It is strongly recommended that you set the “Capture Rate” of your eLogger or Recorder to 10 samples/second, since this setting controls the rate at
which the OSD Pro receives information from the eLogger/Recorder. The more data received by the RTH feature, the better.
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RTH is a safety feature of last resort, should you lose radio contact with your model. Never rely on the RTH function to fly or navigate your
model. Never fly out of the manufacturer’s recommended range, or fly outside VLOS (Visual Line of Sight).
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When enabled, Safety Mode will activate based on the How the OSD Pro Determines when Safety Mode should be Invoked section below. Read
this section carefully!
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RTH will work best with stable, self correcting airplanes and will not work reliably with flying wings or aerobatic planes, unless you are using a
stabilization system.
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RTH will not work with traditional helicopters.
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Never intentionally turn off your radio to test RTH in the air. There is a chance that your receiver will not link back up with your radio, especially
with 2.4GHz radios, which could result in a crash. Always use one of the RTH test methods described in the manual for testing RTH.
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RTH will NOT engage if the GPS signal quality is not adequate. Failsafe Safety mode will engage instead. RTH will program your throttle to the
setting you entered for “Motor Off” during the Servo Analysis Wizard in this situation
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RTH throttle control will not engage if your altitude is less than 60 feet/20 meters above ground level, or if your speed is less than 3 MPH or 3K/H
(note that the low altitude check can be disabled via the menus, as described below).
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If you routinely fly near to the maximum range of your receiver, and have periodic link dropouts from which you are able to recover after sluggish
model performance, Safety Mode may engage when you don’t want it to. Safety mode is not intended to be used if you routinely fly beyond the
maximum range of your receiver.
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It is strongly recommended that RTH mode not be used by inexperienced pilots, until they are comfortable with all aspects of flying.
Description of the Safety Modes
There are two safety modes:
Return to Home Mode
Return to Home (RTH) attempts to recover your model if you lose radio contact, by returning the model to the home location. Both traditional fixed wing
models, and elevon or vtail models, such as flying wings, are supported.
The RTH uses enhanced implementations of Proportional, Integral, Derivative (PID) controllers to adjust the model’s altitude and direction. Specifically, a
PID controller is used for turning, and a PD controller is used for climbing. More information on PID controllers is available here:
http://en.wikipedia.org/wiki/PID_controller
.
Several parameters of the RTH PID controller are adjustable, for tuning RTH to your model. Each parameter is described on the “Safety Mode Menu” page
in the “Description of On-screen Menus” section of the manual below. Note that the default settings for tuning RTH work adequately with many models, so
you may not need to change them during the testing process.
The PID controllers use GPS course, speed, altitude and other information to attempt to return the model to home. Use of a stabilization system can greatly
improve RTH function, especially in models that are not inherently stable.
An advanced feature of RTH gives you the ability to specify two RTH altitudes, and a distance radius for switching between the two altitudes.
Failsafe Mode
In Failsafe Mode, the OSD Pro returns the servos to a pre-determined failsafe position if radio contact is lost. If your Receiver supports multiple
programmable failsafes, the OSD’s Failsafe Safety Mode is probably not useful to you. If you have a receiver that does not have failsafe capability, and
does not hold the servos at the last position (your servos move randomly if radio signal is lost), or a radio with only 1 programmable failsafe, then the
Failsafe safety mode can be used to set a failsafe on all three of your control surfaces, in the event of radio signal loss. The failsafe servo positions are
chosen during the Safety Mode Wizard, described earlier in this document. The “Level Flight” aileron/rudder and elevator settings you indicated, and the
“Motor Off” throttle setting you indicated during the wizard are recorded for use as the Failsafe Mode failsafe settings.
How the OSD Pro Determines when Safety Mode should be Invoked
