Title: Line-of-Sight Guidance Laws for 2-D and 3-D Path Following of Aircraft and Marine Craft
Speaker: Thor I. Fossen, Department of Engineering Cybernetics, Norwegian University of Science and Technology (NTNU) 

Date: September 25, 2023
Time: 2 pm
Location: FEUP – Room B023

Abstract: Autonomous underwater vehicles (AUVs), uncrewed aerial vehicles (UAVs), and uncrewed surface vehicles (USVs) rely heavily on guidance systems to accomplish desired motion control scenarios such as path following and path tracking. The AUV and UAV control objective for path-following is to follow a predefined path in 3-D. For ships and USVs, it is common to specify a 2-D desired planar path parametrized by straight lines and circle segments (Dubins path). A popular and effective way to achieve convergence to the desired path is to implement a look-ahead line-of-sight (LOS) guidance law mimicking an experienced navigator. In this context, the LOS guidance law is derived from a 3-D amplitude-phase representation of the North-East-Down differential equations using Lyapunov stability theory. Alternatively, the vehicle’s position can be modeled as an ideal particle, which can be forced to converge and follow a desired geometrical path by controlling the vehicle’s azimuth and elevation angles. This is referred to as guidance-based path following. The main advantages of LOS guidance laws over Serret-Frenet moving particle methods are simplicity and a small computational footprint. For the LOS guidance laws, uniform semiglobal exponential stability (USGES) can be proven using Lyapunov stability theory. Exponential stability guarantees strong convergence and robustness properties to perturbations. Vehicle path-following control systems can be implemented using commercial heading and altitude/depth autopilots in series with the LOS guidance laws. This presentation provides an overview of LOS guidance laws for 2-D and 3-D path following, including recent results on integral LOS (ILOS) and adaptive LOS (ALOS). The ILOS and ALOS guidance laws compensate for drift forces due to wind, waves, and ocean currents in heading autopilots. Case studies involving marine craft exposed to stochastic ocean currents illustrate the performance of the guidance laws.

Biography: Thor I. Fossen is a professor of guidance, navigation, and control (GNC) at the Department of Engineering Cybernetics, Norwegian University of Science and Technology (NTNU), Trondheim. He received an M.Sc. in Marine Technology in 1987 and a Ph.D. in Engineering Cybernetics in 1991. Besides cybernetics, Fossen’s field of research is aerospace engineering and marine technology. This includes GNC systems for uncrewed vehicles (AUV, UAV, USV), robotics, vehicle dynamics, and inertial navigation systems. He has been a Fulbright scholar in flight control at the Department of Aeronautics and Astronautics of the University of Washington, Seattle. Fossen is the author of the Wiley textbook Handbook of Marine Craft Hydrodynamics and Motion Control (2021). He is one of the co-founders and former Vice President of R&D of the company Marine Cybernetics, which DNV acquired in 2012. He is also a co-founder of ScoutDI (2017), which develops drone-based systems for fully digitalized inspections of industrial confined spaces. The Institute of Electrical and Electronics Engineers elevated him to IEEE Fellow in 2016. He received the Automatica Prize Paper Award in 2002 and the Arch T. Colwell Merit Award in 2008 at the SAE World Congress. He was elected to the Norwegian Academy of Technological Sciences (1998) and the Norwegian Academy of Science and Letters (2022).

[Limited spots available based on room capacity]