Chapter 13 - A nonlinear PID controller design for 6-DOF unmanned aerial vehicles

Abstract

A nonlinear proportional integral derivative (NLPID) controller is proposed to stabilize the translational and rotational motion of a six-degree of freedom (DOF) unmanned aerial vehicle (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 is 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 that more closely resembles the actual system. Six NLPID controllers are designed, each for roll, pitch, yaw, altitude, and the position subsystems, where their parameters are tuned using a genetic algorithm (GA) to minimize a multiobjective output performance index. The stability of the 6-DOF UAV subsystems has been analyzed in the sense of the Hurwitz stability theorem under certain conditions on the gains of the NLPID controllers. The simulations have been accomplished under the MATLAB®/Simulink environment and include 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 one, and the simulations showed the effectiveness of the proposed NLPID controller in terms of speed, control energy, and steady state error.