Showing papers by "Cornel Sultan published in 2021"

Constrained Control of Moored Ocean Current Turbines With Cyclic Blade Pitch Variations

Abstract: In this article, a new method to control an ocean current turbine (OCT) is examined. The key innovation, inspired by helicopter control, is to use cyclic blade pitch angle variations. Output variance constrained controllers are designed for OCT flight control and their performance is analyzed.

Modeling and Stability of a Laser Beam-Driven Sail

Abstract: Traveling to distant stars has long fascinated humanity, but vast distances limited space exploration to our solar system. The Breakthrough Starshot Program aims at eliminating this limitation by traveling to Alpha Centauri, which is 4.37 light-years away. The idea is to accelerate a sail to relativistic speeds using a laser beam aimed at the sail. Stable beam-riding requires dynamic stability analysis of the sail. Currently, sail dynamic stability is not well understood and there is no agreement on the proper shape of the beam-driven sail. Here we study dynamic stability of a beam-driven sail modeled as a rigid body whose shape is parameterized by a sweep function. We analyze the stability of the beam-driven sail using linear system theory and deduce some crucial parameters of the sail. We estimate the region of attraction (ROA) using Lyapunov theory and Sum-of-square (SOS) programming. Simulation results validate our theoretical analysis.

Integrated Path Planning and Tracking Control of Marine Current Turbine in Uncertain Ocean Environments.

Abstract: This paper presents an integrated path planning and tracking control of marine hydrokinetic energy harvesting devices. To address the highly nonlinear and uncertain oceanic environment, the path planner is designed based on a reinforcement learning (RL) approach by fully exploring the historical ocean current profiles. The planner will search for a path to optimize a chosen cost criterion, such as maximizing the total harvested energy for a given time. Model predictive control (MPC) is then utilized to design the tracking control for the optimal path command from the planner subject to problem constraints. The planner and the tracking control are accommodated in an integrated framework to optimize these two parts in a real-time manner. The proposed approach is validated on a marine current turbine (MCT) that executes vertical waypoint path searching to maximize the net power due to spatiotemporal uncertainties in the ocean environment, as well as the path following via an MPC tracking controller to navigate the MCT to the optimal path. Results demonstrate that the path planning increases harnessed power compared to the baseline (i.e., maintaining MCT at an equilibrium depth), and the tracking controller can successfully follow the reference path under different shear profiles.