mirror of
https://github.com/iNavFlight/inav.git
synced 2025-07-13 11:29:56 +03:00
79 lines
4.5 KiB
Markdown
79 lines
4.5 KiB
Markdown
# PID tuning
|
|
|
|
Every aspect of flight dynamics is controlled by the selected "PID controller". This is an algorithm which is
|
|
responsible for reacting to your stick inputs and keeping the craft stable in the air by using the gyroscopes and/or
|
|
accelerometers (depending on your flight mode).
|
|
|
|
The "PIDs" are a set of tuning parameters which control the operation of the PID controller. The optimal PID settings
|
|
to use are different on every craft, so if you can't find someone with your exact setup who will share their settings
|
|
with you, some trial and error is required to find the best performing PID settings.
|
|
|
|
A video on how to recognise and correct different flight problems caused by PID settings is available here:
|
|
|
|
https://www.youtube.com/watch?v=YNzqTGEl2xQ
|
|
|
|
Basically, the goal of the PID controller is to bring the craft's rotation rate in all three axes to the rate that
|
|
you're commanding with your sticks. An error is computed which is the difference between your target rotation rate and
|
|
the actual one measured by the gyroscopes, and the controller tries to bring this error to zero.
|
|
|
|
Note that:
|
|
|
|
* For fixed wing, a PIFF controller is used. Some documentation is available in the wiki and legacy release notes.
|
|
* The INAV Configurator provides conservative example PID settings for various aircraft types. These will require tuning to a particular machine.
|
|
|
|
## PIDs
|
|
|
|
**The P term** controls the strength of the correction that is applied to bring the craft toward the target angle or
|
|
rotation rate. If the P term is too low, the craft will be difficult to control as it won't respond quickly enough to
|
|
keep itself stable. If it is set too high, the craft will rapidly oscillate/shake as it continually overshoots its
|
|
target.
|
|
|
|
**The I term** corrects small, long term errors. If it is set too low, the craft's attitude will slowly drift. If it is
|
|
set too high, the craft will oscillate (but with slower oscillations than with P being set too high).
|
|
|
|
**The D term** attempts to increase system stability by monitoring the rate of change in the error. If the error is rapidly converging to zero, the D term causes the strength of the correction to be backed off in order to avoid overshooting the target.
|
|
|
|
|
|
## TPA and TPA Breakpoint
|
|
|
|
TPA stands for Throttle PID Attenuation and according to [AlexYork.net](http://blog.alexyorke.net/what-is-tpa/):
|
|
|
|
> "TPA basically allows an aggressively tuned multi-rotor (one that feels very locked in) to reduce its PID gains when throttle is applied beyond the TPA threshold/breakpoint in order to eliminate fast oscillations.."
|
|
|
|
Note that TPA is set via CLI or on the PID TUNING tab of the GUI. tpa_breakpoint is set via CLI
|
|
|
|
Also note that TPA and tpa_breakpoint may not be used in certain PID Controllers. Check the description on the individual controller.
|
|
|
|
TPA applies a PID value reduction in relation to full Throttle. It is used to apply dampening of PID values as full throttle is reached.
|
|
|
|
**TPA** = % of dampening that will occur at full throttle.
|
|
|
|
**tpa_breakpoint** = the point in the throttle curve at which TPA will begin to be applied.
|
|
|
|
An Example: With TPA = 50 (or .5 in the GUI) and tpa_breakpoint = 1500 (assumed throttle range 1000 - 2000)
|
|
|
|
* At 1500 on the throttle channel, the PIDs will begin to be dampened.
|
|
* At 3/4 throttle (1750), PIDs are reduced by approximately 25% (half way between 1500 and 2000 the dampening will be 50% of the total TPA value of 50% in this example)
|
|
* At full throttle (2000) the full amount of dampening set in TPA is applied. (50% reduction in this example)
|
|
* TPA can lead into increase of rotation rate when more throttle applied.
|
|
|
|
|
|
|
|
|
|
**How and Why to use this?**
|
|
|
|
If you are getting oscillations starting at say 3/4 throttle, set tpa breakpoint = 1750 or lower (remember, this is assuming your throttle range is 1000-2000), and then slowly increase TPA until your oscillations are gone. Usually, you will want tpa breakpoint to start a little sooner then when your oscillations start so you'll want to experiment with the values to reduce/remove the oscillations.
|
|
|
|
## PID controllers
|
|
|
|
INAV has a single built-in PID controller. The PID controller scaling
|
|
means that Betaflight PIDs should be comparable.
|
|
|
|
Note that very old INAV versions had more PID controllers. These have been removed.
|
|
|
|
|
|
## RC rate, Pitch and Roll Rates (P/R rate before they were separated), and Yaw rate
|
|
|
|
### RC Rate
|
|
|
|
An overall multiplier on the RC stick inputs for pitch, rol;, and yaw.
|