Priority task approach for USVs' path following missions with obstacle avoidance and speed regulation

Marine robotics is becoming increasingly more effective and useful for many applications in the real world. This process of technological transfer strongly needs the actual achievement of full autonomy and high reliability of the robotics systems. Hence, many works conducted by the marine robotics community are aimed to further enhance control techniques to end up with complex autonomous systems endowed with high robustness and reliability. The present paper faces these problems, adapting and applying to unmanned marine vehicles a technique that usually is exploited for robotic manipulators. In particular, the problem of path following is addressed and a navigation guidance and control system based on a priority task approach is developed. Such a control paradigm allows to separate the different tasks required to the robot and to combine them into an overall 'emerging behaviour'. Moreover, one of its great advantages is the high system flexibility: additional control tasks can be included later, leaving the architecture unchanged. The case of three different control tasks is addressed in the present work, namely path following, obstacle avoidance and speed regulation. The approach has been validated through extensive simulative campaigns; experimental tests are planned and will be conducted in the very next future.