Heading angle and depth control of micro-ROVs using adaptive minimum-degree pole placement (MDPP) approach

Abstract

Underwater vehicles are known as complex systems with extremely nonlinear nature, and it makes them hard to control and steer. Due to uncertainty in model, strong disturbances cause by water streams, etc. Control of such devices is a hard task to accomplish in providing a precise mathematical model of a dynamic system that is the most important step in analysis and design of an autopilot. In present study, a ROV which its motion can be described in 3D space with six degrees of freedom has been considered. In spite of a great level of complexity caused by hydrodynamic forces and moments which have a highly nonlinear nature, a precise mathematical model of DST-R-100-4 with all effects of hydrodynamics terms, added mass, buoyancy forces and so on has developed. The model equations and parameters are extracted from related references. Considering the variation of system’s parameters and lack of knowledge about the variation ranges of them, an adaptive pole placement strategy is employed in order to control and achieve an acceptable performance. For this reason, online identification based on RLS method is realized and model parameters can be updated in each sampling time. To investigate the performance of the controller, simulations are performed in presence of variant parameters of the dynamic model and external disturbances. Results show a suitable performance for the designed controller.