6.1 KiB
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.
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.