High-Order PI Control Tuning for Multicopter UAVs Using Ant Colony Optimization

Multicopter unmanned aerial vehicles (UAVs) are increasingly employed in various civil and military applications where performance and stability requirements are becoming more demanding. Most commercial flight controllers use Proportional-Integral-Derivative (PID) control strategies, which provide reliable and stable performance for typical UAV operations. However, emerging applications that demand faster dynamic response may require enhanced control architectures. This paper investigates a high-order Proportional-Integral (PI) control structure that incorporates multiple proportional gains and a single integral gain to improve the attitude control performance of a quadcopter UAV. The proposed controller is derived from the Proportional-IntegralPlus (PIP) formulation-commonly used in process control-while omitting its delay-compensation terms, as multicopter dynamics generally do not exhibit significant system delays. The PIP controller is derived from state-space formulations, enabling it to control systems with significant inertia or coupling such as in multicopter dynamics and UAVs in general. The performance of the proposed high-order PI controller is compared with that of a conventional PID controller under equivalent tuning conditions. Simulation results demonstrate that the high-order PI controller offers two main advantages: (1) improved noise rejection in the presence of measurement disturbances, and (2) a faster transient response, making it particularly suitable for high-speed UAV missions such as racing and defense operations.