Design of a Robust Observer-based DP Control System for an ROV with Unknown Dynamics Including Thruster Allocation

Abstract

This paper is concerned with developing a DP control system in the presence of thruster rate limits and saturation constraints. The proposed control system consists of a robust controller together with an extended-state observer (ESO) so that only an acceptable estimate of inertia matrix is required for control system design. Extended-state observer is used to estimate unknown dynamics and velocities of ROV. A robust controller based on sliding mode methods is proposed for DP control system. Furthermore, thrust allocation algorithm is considered in DP control system synthesis to take into account thruster system constraints namely, saturation and rate limits. Three sets of simulations are carried out to evaluate the performance of the proposed control system and comparisons are made with simple PD-type controllers. The results show that thruster constraints have stringent effects on performance of DP control systems. It is also shown that robust controllers maintain better accuracies despite these limits and constraints and compensate for these discrepancies more effectively.