🛩️ Robust and Agile Quadrotor Flight via Adaptive Unwinding-Free Quaternion Sliding Mode Control

This repository provides the official code implementation for the manuscript:

"Robust and Agile Quadrotor Flight via Adaptive Unwinding-Free Quaternion Sliding Mode Control"
Amin Yazdanshenas and Reza Faieghi
[🎥 Video Demo]

We propose an adaptive quaternion-based sliding mode controller (AQSMC) for nano quadrotors that:

• Resolves the unwinding issue in quaternion-based controllers,
• Incorporates adaptive switching gains to handle unknown disturbances without overgrowth,
• Ensures robust and agile flight under limited onboard computation,
• Runs reliably on resource-constrained platforms like the Crazyflie 2.1.

We implement and test multiple quaternion-based sliding mode controllers, including QSMC and AQSMC, and compare them against widely used benchmark controllers such as:

• GTC – Geometric Tracking Controller,
• ESMC – Euler-based Sliding Mode Control,
• QPD – Quaternion PD for attitude + SMC for position.

Extensive hardware experiments were conducted, including:

• 3-DOF gimbal tests for isolated attitude control,
• Lemniscate trajectory tracking in 6-DOF free flight,
• Throw-launch recovery from inverted initial conditions,
• Wind disturbance rejection, and
• Sensitivity analysis across different controller tunings and scenarios.

All results demonstrate superior performance, agility, and robustness of AQSMC over the benchmark methods.

📁 Repository Structure

CrazyAQSMC/
├── crazyflie-firmware/        # Modified Crazyflie firmware with out-of-tree controllers
├── crazyflie-lib-python/      # Python scripts to log, launch, and visualize experiments
├── Robust_and_Agile_Quadrotor_Flight_via_Adaptive_Unwinding-Free_Quaternion_Sliding_Mode_Control.pdf   # Paper PDF