Composite disturbance observer-based backstepping stabilisation for 3-DOF ship-borne platform with unknown disturbances

ABSTRACT

A composite anti-disturbance stabilisation control scheme is presented for the ship-borne platform system with completely unknown disturbances. The completely unknown disturbances consist of external time-varying disturbances and norm-bounded unmodelled dynamics. The composite anti-disturbance control scheme is built through integrating the nonlinear disturbance observer and the robustifying term with the vectorial backstepping technique. The nonlinear disturbance observer is designed to provide the on-line estimations of external time-varying disturbances such that the disturbance compensation term is introduced into the control design. The robustifying term with the adaptive law is employed to attenuate norm-bounded unmodelled dynamics. On the basis of the vectorial backstepping technique, the composite anti-disturbance control law is derived. The composite anti-disturbance control structure consists of the outer layer with the nonlinear disturbance observer for external time-varying disturbance cancellation as well as the inner layer with the vectorial backstepping control together with the robustifying term for unmodelled dynamic attenuation. By means of the Lyapunov stability theory, it is proven that the composite anti-disturbance stabilisation controller can achieve the disturbance rejection and attenuation simultaneously. It is verified by illustrative simulations that the composite anti-disturbance stabilisation control scheme can effectively stabilise the ship-borne stabilisation platform.

KEYWORDS:

• Ship-borne platform
• disturbance observer
• robustifying term
• vectorial backstepping
• composite anti-disturbance

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported partly by the National Natural Science Foundation of China under Grants 62273172 and 61903174, partly by the Outstanding Youth Innovation Team Project of Shandong Higher Education Institution under Grant 2021KJ042, partly by the Open Project Program of Shandong Marine Aerospace Equipment Technological Innovation Center, Ludong University under Grant MAETIC2021-01, partly by Fund of Hubei Key Laboratory of Inland Shipping Technology under Grant NHHY2021003, partly by National Natural Science Foundation of China-Shandong Joint Fund under Grant U2006229, partly under Shandong Major Innovation Project under Grants 2020CXGC010701, 2020CXGC010702, 2021CXGC01070702, partly by Shandong Key development program (academician team support project) under Grant 2020ZLYS11, partly by Yantai Science and Technology Plan Project under Grant 2021ZDCX001, and partly by Yantai New and Old Kinetic Energy Conversion Research Institute Scientific Research Project under Grant 2020XJDN004.