Optimal Control of an Aircraft Pitch Angle using PID and Sliding Mode Control Based on PSO Algorithm

Modeling and control of Unmanned Aerial Vehicle is undoubtedly one of the most active areas in the field of control engineering. The characteristics of aerial vehicles such as nonlinear dynamics, time variability and the structural and parametric uncertainties make flight control issue relatively a complex and important subject. One of the widely used methods in this area is sliding mode control technique. This paper proposes the design, the simulation, and the analysis of two controllers namely PID and sliding mode in order to optimally control the pitch angle of an unmanned aircraft. Initially, in order to model the dynamic system, an appropriate mathematical model is presented to describe the longitudinal motion of aircraft. Subsequently, a robust sliding mode controller is designed using particle swarm optimization (PSO) algorithm to control the pitch angle of an aircraft against the uncertainties and the external disturbances. The optimal parameters are determined by minimizing both the control signal and tracking error. Then, the performance quality of the proposed method was compared with the results of the optimal PID controller in terms of transient response characteristics. Finally, simulation results indicated that the proposed sliding mode controller can reduce the overshoot of system response and yield more robust performance than PID for the control of pitch angle.