Extended state observer-based integral line-of-sight guidance law for path following of underactuated unmanned surface vehicles with uncertainties and ocean currents

Abstract

This article focuses on the problem of path following for underactuated unmanned surface vehicles (USVs) considering model uncertainties and time-varying ocean currents. An extended state observer (ESO)-based integral line-of-sight (ILOS) with an integral sliding mode adaptive fuzzy control scheme is proposed as the main control framework. First, a novel ESO is employed to estimate the surge and sway velocities based on the kinetic model, which are difficult to measure directly. Then, the adaptive ILOS guidance law is proposed, in which the integral vector is incorporated into the adaptive method to estimate the current velocities. Meanwhile, an improved fuzzy algorithm is introduced to optimize the look-ahead distance. Second, the controller is extended to deal with the USV yaw and surge velocity signal tracking using the integral sliding mode technique. The uncertainties of the USV are approximated via the adaptive fuzzy method, and an auxiliary dynamic system is presented to solve the problem of actuator saturation. Then, it is proved that all of the error signals in the closed-loop control system are uniformly ultimately bounded. Finally, a comparative simulation substantiates the availability and superiority of the proposed method for ESO-based ILOS path following of USV.

Extended bounded real lemma based sum of squares for static output feedback H∞ heading control

“…The linear state space equation of a linear system is similar as (10), the closed-loop linear system by state feedback is 14…”

“…(21) means that the nonlinear system (10) has a H ∞ performance based on HLF. By Schur complementary lemma, 20 (20) is equivalent to…”

“…Here, a novel QEBRL-SOS method is designed to obtain SOS condition without an extended matrix on the computing cost by compared with E-SOS method. Moreover, a novel HEBRL-SOS method is proposed to obtain SOS conditions for the solution of controller parameters to guarantee the robustness of (10).…”

“…Since ocean currents impact on the ship symmetry, the unmeasurable linear velocity of USV cannot be used to calculate the sideslip angle, which reduces the accuracy of trajectory tracking 9 . An extended state observer was proposed to estimate the linear velocity, and the integrated line‐of‐sight guidance law with the extended state observer was proposed to track trajectory 10 . These technologies based on state observers to estimate linear velocity provide a good solution for USV heading regulation, but it makes difficulties to controller design and stability analysis of system.…”

“…9 An extended state observer was proposed to estimate the linear velocity, and the integrated line-of-sight guidance law with the extended state observer was proposed to track trajectory. 10 These technologies based on state observers to estimate linear velocity provide a good solution for USV heading regulation, but it makes difficulties to controller design and stability analysis of system. Moreover, if the velocity is the time derivative of the position, it is inclined to amplify noise, which reduces the accuracy of heading regulation by state feedback.…”