Relative velocity control and integral line of sight for path following of autonomous surface vessels: Merging intuition with theory

Abstract

The integral line-of-sight guidance law for path following applications of autonomous surface vessels is presented in a unified manner, merging intuitive and theoretical aspects of this valuable control technique. Straight line path following scenarios of underactuated surface vessels in the presence of unknown constant irrotational ocean currents are considered. The integral line-of-sight guidance and two feedback controllers are combined into a cascaded configuration where the integral effect in the line-of-sight guidance is introduced to counteract the disturbance. The chosen integration law is defined to reduce the risk of wind-up effects, and it is shown that the integral action in the line-of-sight guidance law performs a vectorial sum between the vessel relative velocity and the unknown current velocity to compensate for the drift. Moreover, only relative velocities are used in the feedback loop since the ocean current is assumed constant and irrotational. Redefining the vessel model with relative velocities significantly simplifies the control system compared to the approach based on absolute velocities. Closed-loop uniform local exponential stability is achieved for path following of straight line paths. Furthermore, in steady state, the presented guidance law paired with measurements of the absolute speed and the relative speed of the vessel yields to an estimation of the ocean current. Simulations are presented to support the theoretical results.

Velocity Controller for a Class of Vehicles

“…Note that the control algorithm (11) is realized in the vehicle body-frame. The obtained results can be transformed next into the earth-frame using the kinematic relationship (6). Proof.…”

“…As it arises from [5] the velocity control system (for guided motion control system) based on velocity tracking is useful for marine vehicles. Surge and yaw relative velocity control of ships can be also based on velocity tracking idea [6]. Some velocity controllers for an autonomous underwater vehicle were proposed in [8].…”

Waypoint guidance control for underwater snake robots exposed to ocean currents

“…In this paper, the same idea will be used in order to steer the underwater snake robot to a desired orientation. Motivated by [22], [23], in [18] the integral LOS method was proposed for USRs where the integral action was added to compensate for the disturbances by the ocean current. As it was shown in [18], the desired orientation for the USR is given by…”

Horizontal-Plane Trajectory-Tracking Control of an Underactuated Unmanned Marine Vehicle in the Presence of Ocean Currents

“…Some exceptions are [15,17,22,23,25,37,42], but these studies do not present any details about the trajectory-tracking differences between the symmetric and asymmetric model of the UMV. Meanwhile, as we can see from [2], ocean current is one of the most important environmental disturbances for an UMV working in the infinitely vast ocean; however, few studies have explicitly addressed ocean current in controller design, and no detailed descriptions of distinct trajectory-tracking control performances in the presence of different ocean-current velocities and direction angles have been presented. The well-known persistent exciting (PE) condition is required in [13, 17-19, 22, 24, 28, 38, 41], though the methods proposed in [11,37] only need a mild PE condition; complete elimination of the PE condition is still difficult in trajectory-tracking control of an underactuated UMV.…”

“…For many years, the scientific, commercial, and naval sectors have shown considerable interest in the design and development of unmanned marine vehicles (UMVs), which can be used to perform a multitude of different tasks, such as mineral resources sampling, offshore oil and gas operations, ocean engineering maintenance, and military reconnaissance [1][2][3][4]. As described in [5], UMV is usually used as a generic term to describe unmanned/autonomous underwater vehicles (UUV/AUV) and unmanned/uninhabited surface vessels (USV).…”