PitLab Autopilot User manual

Autopilot – User's manual
Electrical connection
Autopilot works exclusively in combination with the OSD. All electrical
connections between the OSD and autopilot P Bs are made through a
dedicated connector on both P Bs. When purchasing a set, the two units
are electrically and mechanically connected to each other.
Autopilot can be connected to a remote control in two ways, depending
on the characteristics of the receiver and the autopilot settings.
Parallel connection of the receiver
Remote control receivers with autonomous outputs of all signals
(parallel) are connected with the autopilot in such a way that the outputs
of appropriate channels of the receiver are connected with the
corresponding input channels of the Autopilot.
NOTE: The remote control kits from different manufacturers may have
different signal sequence-for specific control elements (ailerons, gas,
direction, altitude), so connecting further signals to the autopilot, you
should pay attention to the meaning of the output from the receiver and
inputs of the autopilot.
The receiver should be connected to all the control signals, and at least
one ground and power supply wire (it is not necessary to connect all pins
of the ground and the power supply). The autopilot should also be
connected to the RSSI signal if the receiver is equipped with such output.
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Autopilot – User's manual
Serial connection of the receiver CPPM or S-Bus
If you use a receiver equipped with serial PPM output ( PPM) or S-Bus,
connection of all channels to the autopilot can be made by a single signal
cable. In this case, we connect to the receiver a ground pin, power, PPM
or S-Bus and RSSI signal if the receiver is equipped with such output.
If you connect Serial PPM signal ( PPM / S-Bus), it is necessary to set up
this signal with FPV_manager applications on your P . Please connect
autopilot board to the computer (via USB) and in configuration
application, choose the socket pin of the Serial Input PPM ( PPM) - Input
#1 or #6 or S-Bus on input #1, and make an assignment of the other
channels of signal to each function of the autopilot.
In serial mode, you can configure the unused PPM inputs as outputs of
autopilot additional channels from serial signal (output Aux 2 to Aux 5).
This eliminates the need to purchase an additional PPM/S-Bus decoder.
NOTE: Additional Aux 4 and Aux 5 outputs offer additional filtering and
option for simple gimbal control and are recommended for the control
of a pan-tilt system (camera control)
RC signal diversity
To avoid problem with RC link on long distances the both serial inputs
can be supplied by 2 independent RC receivers working as diversity.
Receivers can work in CPPM (on both # and #6 input channels) or S-
Bus mode (on # input channel). To work properly both receivers
should have the same channel order.
Document: Detailed description of diversity is described in separate
document: “Diversity in PitLab FPV System”.
Connecting the servos and motor controller
Autopilot directly controls servos in the model, and the electric motor
speed controller (ES ). These devices must be connected to the
appropriate terminals, according to their description.
Because the autopilot in stabilization and AUTO mode actively stabilizes
the position of the model in response, among others to wind gusts or
turbulence, it more intensively burdens the servos and makes them
consume significantly more power during operation. Normally used linear
voltage regulators built in motor speed controllers often are insufficiently
efficient to meet the increased demand of current and are subject to
overheating, which can lead to a malfunction of the system. For this
reason, we recommend the use of external switching controllers (UBE )
rated for 3A or more (depending on the size of the model), or motor
controllers with built-in switching UBE . In the case of external UBE
please disconnect the red wire from the plug of motor controller.
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Autopilot – User's manual
GPS Connection
Using the OSD -Autopilot set it is advisable to switch the GPS connector
from the OSD board into connector on autopilot P B. In such case the
GPS system is supplied by a pulse-UBE (like servos), relieving the linear
regulator circuit on OSD (less heat is generated on the OSD board), and
reducing the power consumption of the video set.
If you use your own GPS, connect it to the connector as described.
NOTE: Before you connect your GPS to the autopilot board you must
verify and possibly change the value of the GPS supply voltage.
The changes are made by soldering respective fields with a drop of tin.
NOTE: This option may be changed only for 3-rd party GPS module. The
default GPS voltage setting corresponds to GPSs available in the store
and sold in a set, in this case no power supply voltage change is required.
RSSI
Autopilot does not use the RSSI signal, but for the convenience of
connecting the receiver it has an input for connecting the signal to be
sent directly to the OSD board. Requirements for RSSI signal have been
escribed in the OSD manual.
NOTE: The OSD board in an earlier version (v2.1) does not receive an
RSSI signal from the autopilot, in such case the RSSI signal from the
receiver should be connected directly to the OSD terminal.
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Autopilot – User's manual
Location of auto ilot board inside a model
Autopilot has an integrated inertial unit (IMU), which allows to determine
the position of the autopilot board in three-dimensional space. This is a
bank and inclination plate (relative to the vertical - the force of gravity),
the direction the front of the plate is facing (compass direction), and the
altitude above the airport (on the basis of changes in barometric
pressure). Thanks to these properties, the autopilot can maintain (and
stabilize) the levels of model flight, and provide the OSD with information
of model tilt (artificial horizon).
However, in order for the information about the location of autopilot
board to agree with the current position of the model, the autopilot
board should be mounted in a suitable manner in a model, so that at the
fixed level flight of the model, the autopilot board was horizontally facing
the direction of flight.
Figure 1 Correct locations of the autopilot inside the model
Figure 2 Impact of incorrect autopilot location on model flight
Figure 3 Impact of incorrect autopilot location on model flight
Small by few degrees autopilot position deviation can be compensated by
settings OSD by the horizon tilt (compensation may also be made during
the flight). Perfect location (or perfect compensation) occurs when
properly trimmed, models flying straight and horizontal in autopilot OFF
mode when you turn stabilization does not change the position a
noticeably.
Autopilot board does not have to be fixed exactly in the model’s center of
gravity, we can choose other convenient place in the hull of the model.
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Autopilot – User's manual
Vibration rotection
Autopilot should be protected against vibration (which affects the
position sensors: accelerometers and gyroscopes). You can use the
dumpers, sponge, or some other own patents. Dampers should dampen
vibrations and resonances (do not use springs and rubber).
NOTE: The greater the mass of an isolated element, the vibrations are
more effectively limited, so it is best to mount flexibly the whole
"sandwich" OSD + autopilot, and not the autopilot board only.
The vibration level is checked with the engine running - if overload and
vibration exceed 2g a digit will appear on the screen showing the current
number of overload (2g, 3g, up to 8g).
Excessive vibration causes tilting ("passing out") of the artificial horizon
on the OSD, despite the fact that the model is still level. The sensors, and
algorithms of the autopilot should ensure the proper operation of up to
the overload of 5 g, but keep in mind that during the fly, there are
additional overloads (turbulence, the centrifugal force, etc.), and
generally the lower the vibration, the more accurate is the work of the
autopilot. You must therefore strive to achieve a minimum level of
vibration from the engine.
Reverses and servos concurrency
Adjusting R apparatus for controlling a particular model means to
correctly set reverses and mixers so that the control rods tilt correspond
to the appropriate control surface deflection. In the same way it is
necessary to adjust the autopilot to the specific model to ensure proper
control of autonomous flight model.
The first step is to select the type of model tail in OSD menu autopilot ->
Mixer
When one rod is attached to two servos and two control surfaces (delta,
tail V, flaperons), we can choose between two options of servos
concurrency, (in line) and (anti in line), depending on whether for the
proper control the opposite – or non-opposite movement of servos is
required.
In the second step, for each side of the rudder we set the correct channel
under OSD autopilot -> Mixers
heck the proper settings for servo and reverse concurrency after
stabilization mode is off, observing the behavior of the control surfaces
on bank and inclination of the model. When reverses and concurrency
are positioned properly, by tilting or pitching the model they must be set
in such a position that during the flight they counteract such deviation of
the model.
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Autopilot – User's manual
Figure 4 The correct setting of concurrency and servos reverses
Figure 5 incorrectly set servos concurrency
Figure 6 Incorrect setting of the reverse (correct concurrency setting
Since the rudder does not participate in the stabilization of flight, it is not
possible to set its reverse on the basis of observation of the behavior of
the model at tilts. Therefore, after any change to reverse of the rudder
the autopilot for about 1 second swings the rudder like to turn to the
right. If after the change of the reverse you see the rudder turn left, it
means that the reverse is not valid.
NOTE: As of version 2.13 of OSD firmware it is more convenient way to
set the reverse of the rudder when selecting the appropriate option in
the OSD menu and deflection in the transmitter of rudder rod to the
right.
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Autopilot – User's manual
Auto ilot modes
Autopilot mode control is done by a three-state R channel connected to
the PPM "6" output, as follows:
hannel for minimum (PPM pulse duration less than 1.2 ms): OFF
- autopilot off.
The center-channel (pulse duration 1.3 ms to 1.7 ms): STAB -
stabilization mode
hannel for maximum (pulse duration more than 1.8 ms): AUTO -
autonomous flight
Furthermore, in the autonomous flight mode you can select one of the
three throttle control position:
Gas at a minimum: AUTO - back to the starting point.
Gas in the middle: WP - flight on waypoints along the route (a
more detailed description contained later in this manual)
Gas to maximum: (*) - circulation over the current GPS point.
urrent autopilot mode is indicated on the OSD screen next to the pilot
icon.
In order or the model to automatically return to the starting point if you
have problems with a range of R circuit, FailSafe mode must be correctly
set in the R receiver :
duty cycle of operation mode channel to maximum (AUTO)
 duty cycle of gas at minimum (back to the starting point).
Document: The development of FPV System made to increase
number of sub-modes. Detailed description of all sub-modes is in
separate document: “Navigation modes in the Pitlab & Zbig FPV
System”.
Turning the auto ilot off
In the OFF mode, all R input signals are transmitted to the output
without any interference (except for disregarding false PPM pulse outside
the acceptable range of 0.8 ms to 2.3 ms).
If the autopilot is connected to only one aileron signal (input # 1 "aileron
1"), the autopilot transmits the same signal on both ailerons outputs -
works as a "Y" cable, making it easy to control two servos from one R
channel.
Stabilization of model
Stabilization of model is essential in order to prevent unexpected or
uncontrolled changes of model position. Proper configuration of
stabilization mode is also required for the correct operation of
autonomous flight mode.
In the case of model deviations from the desired position, stabilization
system forces appropriate control surface deflection to eliminate these
deviations. Proportionality of steering surfaces deflection in relation to
the position deviation is defined by setting in the OSD menu Autopilot-
>Roll stabilization and Autopilot->Pitch stabilization.
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Autopilot – User's manual
Figure 7 Illustration of operation of banking stabilization algorithm
Figure 7 Illustration of operation of inclination stabilization algorithm
The correct setting of the stabilization of the model is necessary to work
in autonomous mode of the autopilot.
We set the highest value of the roll stabilization force at which the model
is flying steadily without falling into oscillation. Too high stabilization
value is manifested by rapid fluctuations in the wings - especially with
increasing speed.
Too low roll stabilization force could prevent proper flight in AUTO mode
(unstable flight, too small or too great banking of model during turns)
We choose the mean pitch stabilization force, with which the model
aimed sharply down, after releasing the elevator stick gets back to the
level without pumping , and cutting the gas airplane glides without
deceleration and stall, and after the addition of gas attains altitude, but
also does not take up too hard.
Small values of pitch stability may cause pumping of the model and with
the model with a strong drive too rapid pulling up of the model on gas.
Too high pitch stabilization force can cause quick, short oscillating up and
down, especially at higher speeds, and also cause stall of the model
without gas, and poor ascending on gas (model accelerates, without
ascending), causing problems in autonomous flight.
Autopilot in stabilization mode does not hold directly the setpoint
direction of flight, but by keeping the level of the model largely
eliminates the unplanned deviations from the current model course.
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Autopilot – User's manual
Autonomous flight mode
In autonomous mode, the autopilot controls the model flight alone,
maintaining the right direction and altitude, as well as preventing too
rapid model banking, which could cause loss of control (framing the wing,
corkscrew, etc.).
In autonomous mode, the autopilot is flying to the point specified by the
position of the throttle (gas channel modulation). Also the distance and
the course displayed on the OSD are always relative to the currently
selected destination (base, waypoint or point of circulation).
Gas at a minimum: AUTO - back to the starting point.
Gas in the middle: WP n - flight to the route number 'n'.
Gas to maximum: (*) - circulation over the current GPS point.
Banking limit
In order to maintain control over the model it is necessary to determine
the maximum (and safe) allowed model banking during maneuvers in
autonomous mode. Make the settings in the OSD Autopilot-> Banking
Limit
Figure 9 Maximum banking of the model in autonomous flight
Too small value of the maximum banking increase the turn radius, or may
even prevent it from turning in strong wind. Too large values can cause
problems with the stability of the model in the air can cause the loss of
altitude during the turn, and cause significant deviation (delay) of the
course provided by the GPS in relation to the real course of the model, so
the model when turning to the base and starts "poking" flying to the
base.
NOTE: For models with a large agility (large aileron deflections) or with
set lower stabilization force it may be necessary to adjust the lower limit
of the banking angles.
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Autopilot – User's manual
Force of getting back on course
When in the autonomous fly the current course of the model is different
from the desired course to the base (or waypoint) the autopilot makes a
turning maneuver performed in order to return to the right course.
Accuracy of staying the course, and the deflection of the ailerons and
rudder in case of deviation from the course is defined by OSD parameter
Autopilot-> Force of getting back on course. This is illustrated in figure:
Figure 10 Illustration of the algorithm to maintain the course
The greater the deviation of the course, the stronger the swing of
ailerons and rudder causing getting back on course. This means that if
deviation of the course is high, then also the turning speed of the model
is high, and with getting closer to the expected course the speed of turn
decreases.
If this value is too low, the model will be turning slowly and will not be
coming to the course to the base. Too high a value causes the model to
perform a quick turn also when the deviation of the course is low, so that
the model significantly exceeds the course and oscillates around the
course flying zigzag.
Mixer ailerons-> direction
Turn of the model is generally obtained by ailerons, but it is also possible
to add steering with the rudder. This is done by the mixer set in the OSD
menu options Autopilot-> Mixers-> mixer ailerons- direction, that helps
to turn the model. In models with ailerons its use and value is at the
discretion of the pilot. Too large values of the mixing can cause excessive
model banking in relation to the value of the banking limit set in
autopilot menu.
NOTE: in aerobatic models where the ailerons do not turn the model, we
should set high values of aileron-direction mixer, and a small banking
value limit.
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