Betaflight PID Tuning

Betaflight is an open-source flight controller software used in multi-rotor drones. One of the most critical components of Betaflight is the PID (Proportional Integral Derivative) controller. It is responsible for stabilizing the drone during flight by adjusting the motor RPMs in response to sensor data.

PID tuning is the process of adjusting the PID gains to optimize the drone's performance. This process involves tweaking the values of the P, I, and D gains until the drone responds smoothly to pilot input, maintains a stable hover, and can fly aggressively without oscillations.

Basic PID Controllers

Before diving into Betaflight's PID controller, let us first understand the concept of PID control. A PID controller is a control loop feedback mechanism that continuously calculates an error value as the difference between setpoint and actual value and applies correction based on proportional, integral, and derivative terms of the error.

Here is a mathematical representation of the PID controller:

Output = Kp * error + Ki * integral + Kd * derivative

where,

• Kp is the proportional gain
• Ki is the integral gain
• Kd is the derivative gain
• error is the difference between setpoint and actual value
• integral is the sum of error over time
• derivative is the rate of change of error

Betaflight's PID Controller

Betaflight's PID controller is a digital implementation of a PID control loop running on a microcontroller on the flight controller board. Betaflight offers two modes of PID control: MultiWii Rewrite (MWRE) and Betaflight Unified Target (BFT). In the MWRE mode, the PID algorithm is a modified version of MultiWii, whereas, in the BFT mode, it's a custom implementation for Betaflight.

Here is a glimpse of how Betaflight's PID controller works:

• The first step is to get data from sensors like gyroscope and accelerometer, which measure the drone's attitude (pitch, roll, and yaw).
• The second step is to calculate the error between the desired attitude (setpoint) and actual attitude from sensor data.
• The third step is to apply the error to the PID controller and calculate the output signal that will adjust the motor RPMs.
• The fourth step is to limit the output signal to a range to prevent the motors from spinning too fast or too slow.

PID Tuning in Betaflight

PID tuning can be daunting for beginners as it requires a lot of trial and error to get it right. In Betaflight, there are many ways to tune the PID gains, and here are some of them:

Betaflight Configurator

Betaflight Configurator is a graphical user interface that allows you to configure and tune Betaflight settings. To access PID settings, connect your drone to your computer, open the Betaflight Configurator, and navigate to the PID Tuning tab.

Here you can adjust the P, I, and D gains for the Roll, Pitch, and Yaw axes individually. You can also adjust the other tuning parameters like Gyro Filtering, D-term Filtering, and Feedforward.

Blackbox Logs

Blackbox is a feature in Betaflight that logs all sensor data during flight. You can use this data to analyze how your drone performs in the air and to fine-tune the PID gains. To use Blackbox, you need to have an SD card inserted in your drone's flight controller.

To view Blackbox logs, you need to use a tool like Blackbox Explorer. This tool allows you to visualize the flight data and make sense of it. You can identify the parts of the flight where your drone is behaving poorly and use the data to adjust the PID gains.

Manual Tuning

Another way to tune the PID gains in Betaflight is to do it manually by flying your drone and making small adjustments to the P, I, and D gains until you find the perfect balance between stability and agility. This method requires practice and patience, and it's best to do it in an open field away from people and property.

Conclusion

PID tuning is an essential process in Betaflight that can make or break your drone's performance. By understanding the fundamentals of PID control, how Betaflight's PID controller works, and the different ways to tune the PID gains, you can unlock your drone's full potential and take your flying skills to the next level.