Nonlinear PID Controller Design for a 6-DOF UAV Quadrotor System

TL;DR

This paper introduces a nonlinear PID controller for a 6-DOF UAV quadrotor, utilizing a detailed nonlinear model and genetic algorithm tuning to improve stability, energy efficiency, and trajectory tracking accuracy.

Contribution

It presents a novel NLPID control design for all six degrees of freedom of a UAV, with parameters optimized via GA and stability analysis included.

Findings

NLPID outperforms linear PID in speed and energy efficiency

Simulation results confirm improved steady-state error and trajectory tracking

Stability conditions are established for the nonlinear controllers

Abstract

A Nonlinear PID (NLPID) controller is proposed to stabilize the translational and rotational motion of a 6-DOF UAV quadrotor system and enforce it to track a given trajectory with minimum energy and error. The complete nonlinear model of the 6-DOF quadrotor system are obtained using Euler-Newton formalism and used in the design process, taking into account the velocity and acceleration vectors resulting in a more accurate 6-DOF quadrotor model and closer to the actual system. Six NLPID controllers are designed, each for Roll, Pitch, Yaw, Altitude, and the Position subsystems, where their parameters are tuned using GA to minimize a multi-objective Output Performance Index (OPI). The stability of the 6-DOF UAV subsystems has been analyzed in the sense of Hurwitz stability theorem under certain conditions on the gains of the NLPID controllers. The simulations have been accomplished under MATLAB/SIMULINK environment and included three different trajectories, i.e., circular, helical, and square. The proposed NLPID controller for each of the six subsystems of the 6-DOF UAV quadrotor system has been compared with the Linear PID (LPID) one and the simulations showed the effectiveness of the proposed NLPID controller in terms of speed, control energy, and steady-state error.