KK2.1.5 PID Tuning

Control Theory 101

• Open loop: No feedback

– Examples: Water faucet, stove top burner setting

• Closed loop: Some sensor to give feedback

and adjust input

– Examples: Thermostat, cruise control, servo

What is PID?

• PID = Proportional, Integral, Derivative

• Common form of closed loop control

• “P depends on the present error, I on the

accumulation of past errors, and D is a

prediction of future errors”

P – Proportional Gain

• Applies response that is proportional to the

magnitude of error between set point and

output

I – Integral Gain

• Applies response that is a function of the

magnitude and duration of the error

• Good for eliminating small steady state error

• Provides “heading hold” function on RC gyro

D – Derivative Gain

• Applies response that is a function of the

slope of the error over time

• Helps settle the system

• Allows for higher P gain

RC Flight Controller Tuning

• P gain is the primary gain to tune

– Makes the helicopter more responsive to inputs

– Oscillation, or “wag” if set too high

• I gain provides heading hold effect

– “locked” feel, eliminates drift

– Slow oscillation if set too high

• D gain damps the response

– Helps you run higher P gain

– Very high frequency oscillation if set too high

General Tuning Procedure

1. Incrementally set the P gain higher until wag

is observed.

2. Slightly reduce P gain to stable level

3. Increment D gain in small step

4. Repeat steps 1-4, D gain allows higher P gain

5. Play with I gain until the heli holds angle in

forward flight (no pitch up)

KK2 Functions

• Only PI control – no need to tune D

• Always tune with self level off

• Leave PI limits at default

• Roll and pitch are usually the same gain on

square quadcopter

KK2 Functions

• ‘Self Level’ P gain = power to self level

– Too high will produce oscillations

– Tune after primary PI gains are set

KK 2 Functions

• Stick Scaling describes stick senstivity

– Similar to dual rates on your transmitter