Pitch autopilot design for an autonomous aerial vehicle in the presence of amplitude and rate saturation

In this article, a new composite anti-windup (AW) compensator scheme is proposed to tackle the rate and amplitude saturations in an autonomous aerial vehicle (AAV). The actuator input saturation is a practical and critical challenge in the controller design of autonomous vehicles. Nowadays, modern anti-windup compensators are presenting practical remedies to cope with input amplitude and rate saturation. Meanwhile, Riccati-based compensators can be a suitable choice due to their high performance and simplicity. Therefore, this article proposes an integrated approach by combining the anti-windup amplitude and rate methods to deal with the aforementioned problems. First, the basic controller function on the linear model is examined. It is shown that this controller behaves well so long as there is no saturation. However, when saturation occurs, its performance is decreased and even becomes unstable. By modifying the controller via the proposed method, the controller efficiency is increased significantly. The proposed method has been implemented on an autonomous aerial vehicle with 6-degrees of freedom (6DOF). Through various simulation scenarios, it is shown that the proposed method can show proper behavior in the case of a nonlinear and close-to-reality model of the system. In addition, the proposed controller efficacy has been investigated in a comprehensive Monte Carlo simulation and it is shown that the proposed method keeps its efficiency against the practical uncertainties of the system behavior.