Model Identification, Dynamic Positioning, and Thrust Allocation System for the milliAmpere1 Autonomous Ferry Prototype: Field Trial Results

Autonomous electric ferries offer an eco-friendly solution for sustainable and intelligent urban mobility. Currently, these ferries are undergoing successful trial operations on short routes for passenger transportation in European and Scandinavian cities. This paper presents experimental results on model identification, thrust allocation (TA), and dynamic positioning (DP) system for the milliAmpere1 (mA1) autonomous electric ferry prototype. The mA1 is a small prototype ferry used as a test platform in several research projects at the Norwegian University of Science and Technology (NTNU). It recently went through a system upgrade and is now equipped with four symmetrically distributed azimuth thrusters. These new systems require a new mathematical model and a reliable DP and TA system to enable autonomous operation. The DP system is responsible for calculating the total force and moment required to keep position or move between waypoints. At the same time, the TA algorithm coordinates the thrusters to ensure that the resulting force they generate matches the request from the DP control algorithm. The DP is designed with a horizontal plane control law, using a feedforward plus feedback control. The TA is formulated as a quadratic programming problem, which includes cost functions for power consumption. A third-order reference guidance system is implemented to ensure smooth and continuous signals for the DP desired position, velocity, and acceleration. Additionally, system model identification was performed to determine the parameters of the actuator dynamics. Full-scale trials were conducted to evaluate the performance of the proposed system in a sheltered basin situated in Trondheim, Norway, under low-wind conditions. The field trial results indicate that the proposed approach successfully stabilized and maintained a desired trajectory.