Have you ever wondered how an unmanned quadrotor helicopter is able to fly? This paper introduces the subject of designing robust control systems for these popular aircraft, summarizing recent approaches, and then providing a novel new one.

The first four pages are accessible to almost anyone with a technical background. Pseudocode and flowcharts are included for the particle swarm optimization (PSO) algorithm used to select the optimal parameters of the backstepping controller (described in a block diagram). Then, the paper goes into the mathematical model of a quadrotor helicopter in detail, but the mathematics quickly gets deep enough so that many nonspecialists will have a hard time following the details. Many understandable figures show the predicted performance of the design, and there is a very readable section on evaluating the algorithm on a quadrotor simulator in Simulink with MATLAB used to implement the PSO algorithm.

The paper was written for control system engineers. It combines different techniques in a novel, new manner, but it would be stronger if the authors had implemented the algorithms and flight tested them.