Control Architecture for Segmented Trajectory Following of a Wind-Propelled Autonomous Catamaran

Abstract

An autonomous surface vehicle, based on a Prindle-19 catamaran and substituting a self-trimming vertical wing for the sail, was developed to demonstrate precision guidance and control. This vehicle, the Atlantis, was demonstrated to track straight line segments to better than 0.3 meters (one σ) when already trimmed for sail along the segment. In order to make the Atlantis useful as an autonomous vehicle, however, more complicated paths are required than simple straight line segments. A segmented trajectory is developed based on waypoints, segments, and arcs as the path primitives. A control architecture is also developed which can traverse a segmented trajectory made of linked path primitives, given reachability constraints due to wind direction.For segments where the destination is unreachable due to the wind direction a lane width is established and an on-the-fly tacking mode is used to traverse the segment while remaining within the lane width. A nonlinear model of the catamaran was simulated using Simulink, including realistic wind and current models. The control architecture was applied to the simulated catamaran using Monte Carlo simulations which demonstrated very robust segment traversal while maintaining a crosstrack error of less than one meter throughout the path.

Control System Performance of an Unmanned Wind-Propelled Catamaran

“…This architecture extends the previous work done on the Atlantis for segmented trajectory control (Elkaim and Kelbley, 2006a;Elkaim and Kelbley, 2006b). The basic controllers are each quite simple: heading hold control, non-linear heading line-of-sight guidance, a proportional integral controller with feed-forward for velocity, a bang-bang controller with hysteresis for tail angle, and a line tracking control that consists of two successive proportional control loops closed around heading and cross-track error (e¤ectively making a proportional derivative control).…”

Station Keeping and Segmented Trajectory Control of a Wind-Propelled Autonomous Catamaran

“…Using the boat, wind, and wave models outlined in [1], the PI controller discussed in Section III was used to follow the set of trajectories generated from predefined waypoints as described in Section IV. The controller monitors both the heading error Ψ and crosstrack Y to adjust the rudder position δ.…”

“…Body and control frame equations [1] were then linearized around a small variance in boat heading providing the linearized equations:Ψ…”

Guaranteed set-point computation with application to the control of a sailboat

“…A proof of this interest is the two recent sailing competitions: the Microtransat Challenge Cup [1] held in Toulouse (France), which aims at building sailboats able to cross the Atlantic ocean in an autonomous way, and the Sailbot [2], another robotic sailboat competition held in Ontario (Canada). To our knowledge, only few works have been proposed to deal with the control of a sailboat using mathematical models [8,7,15].…”