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betaflight/docs/development/PID Internals.md
2015-02-07 16:58:50 +01:00

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### IO variables
gyroData/8192*2000 = deg/s
gyroData/4 ~ deg/s
rcCommand - -500-500 nominal, but is scaled with rcRate/100, max +-1250
inclination - in 0.1 degree, default 50 degrees (500 units)
axisPID - output to mixer, will be added to throttle(1000-2000), output range is <minthrottle, maxthrottle> (default <1150 - 1850>)
### PID controller 0, "MultiWii" (default)
## Leveling term
error = constrain(2*rcCommand[axis], limit +- max_angle_inclination) - inclination[axis]
P = constrain(P8[PIDLEVEL]/100 * error, limit +- D8[PIDLEVEL] * 5)
I = intergrate(error, limit +-10000) * I8[PIDLEVEL] / 4096
## Gyro term
P = rcCommand[axis];
error = rcCommand[axis] * 10 * 8 / pidProfile->P8[axis] - gyroData[axis] / 4; (conversion so that error is in deg/s ?)
I = integrate(error, limit +-16000) / 10 / 8 * I8[axis] / 100 (conversion back to mixer units ?)
reset I term if
- axis rotation rate > +-64deg/s
- axis is YAW and rcCommand>+-100
## Mode dependent mix(yaw is always from gyro)
HORIZON - proportionally according to max deflection
Gyro - gyro term
Angle - leveling term
## Gyro stabilization
P = -gyroData[axis] / 4 * dynP8 / 10 / 8
D = -mean(diff(gyroData[axis] / 4), 3) * 3 * dynP8 / 32