Longitudinal and Feedforward Controller Design Based on Linear Matrix Inequalities for a Mini Aerial Vehicle

Abstract

This paper presents the design of a multi-input multi-output (MIMO) optimal proportional–integral–derivative (PID) controller and a feedforward controller to enhance disturbance rejection and reference tracking in a mini aerial vehicle (MAV). The feedback controller is developed using linear matrix inequality (LMI) constraints within an iterative framework for tuning the PID parameters. In addition, a feedforward control strategy is proposed to further improve performance in reference tracking and disturbance rejection. The feedforward controller is designed under LMI constraints to minimise the H_∞ norm of the transfer function matrix relating disturbances (or set-points) to the output (error). This optimisation problem is challenging due to its non-convex and nonlinear nature. Therefore, the main contribution of this paper is to propose a method based on utilising frequency sampling techniques, iterative algorithms and convex optimisation formulation to guarantee optimal solutions for reference tracking and disturbance rejection within specified constraints, which is crucial for preventing irreversible damage in control systems and also enhances the manoeuvrability of the MAV.