# VTOL QuickTune

This script implements a fast VTOL tuning system for multicopters and
quadplanes. This script can be used to automate the process of
producing a good "manual tune" for the VTOL rate control parameters.

The script is designed to be used in QLOITER mode for quadplanes or
LOITER mode in multicopters, although it can also be used in other
VTOL modes.

# Parameters

The script adds 7 parameters to control it's behaviour. The parameters
are:

## QUIK_ENABLE

this must be set to 1 to enable the script

## QUIK_RC_FUNC

The RCz_OPTIONS scripting function binding to be used for this script.
Default RCz_OPTIONS binding is 300 (scripting1).

## QUIK_AXES

This is the set of axes that the tune will run on. The default is 7,
which means roll, pitch and yaw. It is a bitmask, so if you want just
roll and pitch then set this to 3. For just yaw you would set it to 4.

## QUIK_DOUBLE_TIME

This controls how quickly a gain is raised while tuning. It is a time
in seconds for the gain to double. Most users will want to leave this
at the default of 10 seconds.

## QUIK_GAIN_MARGIN

This is the percentage gain margin to use. Once the oscillation point
for a gain is found the gain is reduced by this percentage. The
default of 60% is good for most users.

## QUIK_OSC_SMAX

This is the oscillation threshold in Hertz for detecting oscillation
when a gain is raised. The default of 5Hz is good for most vehicles,
but on very large vehicles you may wish to lower this. For a vehicle
of 50kg a value of 3 is likely to be good. For a vehicle of 100kg a
value of 1.5 is likely to be good.

You can tell you have this set too high if you still have visible
oscillations after a parameter has completed tuning. In that case
halve this parameter and try again.

## QUIK_YAW_P_MAX

This sets a limit on the YAW_P rate gain. The yaw axis on most
multirotor style vehicles needs to have a much lower limit on the P
gain than the oscillation limit to ensure that enough control remains
for roll, pitch and thrust. A maximum of 0.5 is good for most VTOL
vehicles.

## QUIK_YAW_D_MAX

This sets a limit on the YAW_D rate gain. The yaw axis on most
multirotor style vehicles needs to have a much lower limit on the D
gain than the oscillation limit to ensure that enough control remains
for roll, pitch and thrust. A maximum of 0.01 is good for most VTOL
vehicles.

## QUIK_RP_PI_RATIO

This is the ratio for P to I for roll and pitch axes. This should
normally be 1, but on some large vehicles a value of up to 3 can be
used if the I term in the PID is causing too much phase lag.

If QUIK_RP_PI_RATIO is less than 1 then the I value will not be
changed at all when P is changed.

## QUIK_Y_PI_RATIO

This is the ratio for P to I for the yax axis. This should
normally be 10, but a different value may be needed on some vehicle
types.

If QUIK_Y_PI_RATIO is less than 1 then the I value will not be
changed at all when P is changed.

## QUIK_AUTO_FILTER

This enables automatic setting of the PID filters based on the
INS_GYRO_FILTER value. Set to zero to disable this feature.

## QUIK_AUTO_SAVE

This enables automatic saving of the tune if this number of seconds
pass after the end of the tune without reverting the tune. Setting
this to a non-zero value allows you to use quicktune with a 2-position
switch, with the switch settings as low and mid positions. A zero
value disables auto-save and you need to have a 3 position switch.

## QUIK_MAX_REDUCE

This controls how much quicktune is allowed to lower gains from the
original gains. If the vehicle already has a reasonable tune and is
not oscillating then you can set this to zero to prevent gain
reductions. The default of 20% is reasonable for most vehicles. Using
a maximum gain reduction lowers the chance of an angle P oscillation
happening if quicktune gets a false positive oscillation at a low
gain, which can result in very low rate gains and a dangerous angle P
oscillation.

# Operation

First you should setup harmonic notch filtering using the guide in the
ArduPilot wiki. This tuning system relies on you already having
reduced gyro noise using the harmonic notch filter. It will fail if
your noise is too high.

Install the lua script in the APM/SCRIPTS directory on the flight
controllers microSD card, then set SCR_ENABLE to 1. Reboot, and
refresh parameters. Then set QUIK_ENABLE to 1.

You will then need to setup a 3 position switch on an available RC
input channel for controlling the tune (or 2 position if you set
QUIK_AUTO_SAVE). If for example channel 6 is available with a 3
position switch then you should set RC6_OPTION=300 (scripting1) to associate the
tuning control with that switch.

If needed, the QUIK_RC_FUNC option can be used to associate the tuning switch
with a different scripting binding such as RCz_OPTION = 302 (scripting3).

You should then takeoff and put the vehicle into QLOITER mode (for
quadplanes) or LOITER mode (for multicopters) and have it in a steady
hover in low wind.

Then move the control switch you setup with option 300 (or via QUIK_RC_FUNC)
to the middle position. This will start the tuning process. You will see text
messages on the ground station showing the progress of the tune. As
the aircraft reaches the oscillation limit of each parameter it will
start a small oscillation, then it will reduce that gain by the
configured QUIK_GAIN_MARGIN percentage and then move onto the next
parameter.

With default settings the parameters to be tuned will be:

 - RLL_D
 - RLL_P
 - PIT_D
 - PIT_P
 - YAW_D
 - YAW_P

The script will also adjust filter settings using the following rules:

 - the FLTD and FLTT settings will be set to half of the INS_GYRO_FILTER value
 - the YAW_FLTE filter will be set to a maximum of 2Hz
 - if no SMAX is set for a rate controller than the SMAX will be set to 50Hz

Once the tuning is finished you will see a "Tuning: done" message. You
can save the tune by moving the switch to the high position (Tune Save). You
should do this to save before you land and disarm. If you save before the tune is completed the tune will pause, and any parameters completed will be saved and the current value of the one being actively tuned will remain active. You can resume tuning by returning the switch again to the middle position, or if moved to the low position, the parameter currently being tuned will be reverted but any previously saved parameters will remain.

If you move the switch to the low position at any time in the tune before using the Tune Save switch position, then all parameters will be reverted to their original
values. Parameters will also be reverted if you disarm before saving.

If the pilot gives roll, pitch or yaw input while tuning then the tune
is paused until 4 seconds after the pilot input stops.

# Using a Two Position Switch

Some transitters only have 2 position switches, with no 3 position
switches available. To support quicktune with a 2 position switch
please set the following:

 - set QUIK_OPTIONS to 1 to indicate the use of a 2 position switch
 - set QUIK_AUTO_SAVE to 10 to automatically save the tune 10 seconds after tuning is done

with these two options the tuning will start when the switch gives a
PWM value of over 1800. Ten seconds after tuning is complete the tune
will automatically save.



