Modular variable structure adaptive backstepping controller: Design and stability analysis

This paper presents the design and stability analysis of a Modular Variable Structure Adaptive Backstepping Controller (MVS-ABC) for plants with arbitrary relative degree, using only input/output measurements. In order to improve the transient response of adaptive backstepping approach via modular design, switching laws are proposed instead of traditional integral adaptive laws. Robustness properties with respect to external disturbances are also demonstrated. Furthermore, simplified algorithms are presented, where the number of relays was significantly reduced (only one is necessary). Simulation results for an unstable system with relative degree three are shown.