Quadrotor cascade PID controller automatic tuning

Abstract

Integrating systems are commonly encountered in many applications, among them are the unmanned aerial vehicles. This paper proposes an automatic tuning scheme for cascade PID control of integrating systems with application to unmanned aerial vehicles. Using relay feedback control in a closed-loop setting, the auto-tuner systematically finds the system's closed-loop frequency response, open-loop frequency response and integrator plus delay model. PID controller parameters are subsequently determined using a set of simple tuning rules. Because the tuning rules contain the desired closed-loop time constant as a performance specification together with desired gain and phase margins, the auto-tuner designed is naturally suited for a cascade PID control system where the inner-loop control system typically has much faster response speed than the primary control system, which can be readily achieved by adjusting the two desired time constants. Experimental results obtained from the auto-tuner application on a quadrotor Unmanned Aerial Vehicles (UAV) are used to demonstrate the efficacy of the proposed approach.