Control of a Non-Holonomic Marine Robot for Isoline Tracking in an Unknown Environmental Field
Аннотация
This paper addresses motion control of a nonholonomic autonomous surface vessel navigating in an uncertain environment to locate and track an isoline of an unknown scalar field. The robot is modeled as a differential-drive catamaran equipped with a single-point sensor providing field measurements only at its current location. The objective is to reach and repeatedly follow the isoline where the field assumes a specified value, despite lacking access to the gradient or global structure of the field. A sliding-mode control strategy, originally developed for Dubins-type land robots, is adapted to the marine setting. The control is implemented through discrete switching of the propeller thrusts, accounting for realistic hydrodynamic constraints, limited actuation, and external disturbances. The resulting strategy ensures convergence to the isoline and stable tangential motion along it. High-fidelity simulations using the Otter USV model validate the approach in scalar fields of varying complexity, including multi-peak configurations and fields with sharp curvatures. The results confirm the method's robustness under moderate disturbances and expose its limitations in lowgradient or drift-dominated scenarios. The findings contribute to environmental monitoring applications using autonomous marine platforms under minimal sensory input.