Super Twisting vs Modified Super Twisting algorithm for altitude control of an Unmanned Aircraft System

This article proposes two control strategies to track a desired altitude of an Unmanned Aircraft System (UAS). These strategies are a Super-Twisting Sliding Mode Controller (Super Twisting-SMC) and a Modified Super-Twisting Sliding Mode Controller (Modified Super Twisting-SMC), both controllers are robusts and present a satisfactory effectiveness even under external disturbances. The Lyapunov Stability Theory is used to guarantee the asymptotic convergence of the altitude tracking error in both control laws. To demonstrate the performance of the proposed solutions, a set of simulation results and experimental results are presented. To carry out the experiments an holonomic quad-rotor UAS is used and their altitude is obtained by using a Motion Capture System. From the theoretical and experimental results it can be proved that the Modified Super Twisting-SMC presents a faster response than the Super Twisting-SMC.