KAI STRAKA 09.2026

Complete flight code for an active canard-stabilized model rocket.

SETUP

The software is MicroPython based and requires a suitable microcontroller. I used the RP2040 Zero. Additional sensors used are the MPU6050 IMU and BMP180 barometer. Note the system has no guidance platforms. The control hardware uses two servos, each controlling a pair of canards along the pitch and yaw axes, respectively. This system allows for independent pitch and yaw control, but no roll control. The flight firmware folder contains the entire code and logging files, installation is as simple as uploading all files from the folder to the microcontroller. main.py will run automatically upon controller power on, and the rest of the control loop is autonomous.

Control Logic

(note the entire system is autonomous, all steps will happen automatically) Upon startup the servos will undergo a ten second control swipe. Following this, the IMU performs a six second calibration and will determine an upwards target vector pointing in the same direction as the rocket (thus if the rocket is sitting upright, the target vector will point straight up). Following the calibration the system will automatically switch to its main PID control loop, and will attempt to stabilize the rocket along its target vector.

Canard and LED info: The canards have a deflection range of 20 degrees in either direction. If an attitude greater than 54 degrees from the target vector is achieved, the canards will lock into their norm positions until power off. A solid green LED indicates IMU calibration, a flashing blue LED indicates free canard control, a flashing red LED indicates canard lockout. A solid blue or red LED indicates system crash. All LED functions are in pixel_led.py. For more information regarding the canard / avionics design I have linked a document here.

Logging: Due to memory limitations within the microcontroller, data logging is not continuous. Instead a preset altitude trigger (8 meters) will begin noting the maximum altitude achieved, and will log this value in alt_data.txt, twenty seconds after trigger activation. Upon canard lockout the altitude at the time of lockout will also be recorded, alongside the max alt into alt_data.txt.

PID Control Loop

The PID loop runs at 1000 Hz and is responsible for stabilizing the rocket along its target vector. It uses a quaternion-based logic to perform attitude calculations. The main control loop uses two separate PID loops, one for pitch orientation and another for yaw orientation. All PID related math is done in pid_main.py. PID values can be adjusted in main.py, and must be tuned according to rocket specifications. Note this code is not exclusive to a canard-type rocket, the PID controller can be used anywhere applicable and the rest of the code applies to any dual axes servo-actuated system.

File Info

main.py: main control loop, runs automatically upon startup and is responsible for the entire calibration and control sequence. This is the most important file.

bmp_alt.py: barometer code, includes max alt logging as well as sensor initialization and usage.

mpu_imu.py: IMU code, sensor initialization and usage.

servo_func.py: includes all servo commands and setup.

Unmentioned files are responsible for background math functions and get called upon by the files above.

Below are images of the avionics stack:

Avionics Section / Custom PCB

Canard Control Swipe

Maiden Launch