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1

An automatic collision avoidance algorithm for multiple marine surface vehicles

Hedjar Ramdane, Bounkhel Messaoud

International Journal of Applied Mathematics and Computer Science

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2019

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Vol. 29, no. 4

759--768

EN

In recent years, unmanned surface vehicles have been widely used in various applications from military to civil domains. Seaports are crowded and ship accidents have increased. Thus, collision accidents occur frequently mainly due to human errors even though international regulations for preventing collisions at seas (COLREGs) have been established. In this paper, we propose a real-time obstacle avoidance algorithm for multiple autonomous surface vehicles based on constrained convex optimization. The proposed method is simple and fast in its implementation, and the solution converges to the optimal decision. The algorithm is combined with the PD-feedback linearization controller to track the generated path and to reach the target safely. Forces and azimuth angles are efficiently distributed using a control allocation technique. To show the effectiveness of the proposed collision-free path-planning algorithm, numerical simulations are performed.

2

Adaptive backstepping tracking control for an over-actuated DP marine vessel with inertia uncertainties

Witkowska A., Śmierzchalski R.

International Journal of Applied Mathematics and Computer Science

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2018

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Vol. 28, no. 4

679--693

EN

Designing a tracking control system for an over-actuated dynamic positioning marine vessel in the case of insufficient information on environmental disturbances, hydrodynamic damping, Coriolis forces and vessel inertia characteristics is considered. The designed adaptive MIMO backstepping control law with control allocation is based on Lyapunov control theory for cascaded systems to guarantee stabilization of the marine vessel position and heading. Forces and torque computed from the adaptive control law are allocated to individual thrusters by employing the quadratic programming method in combination with the cascaded generalized inverse algorithm, the weighted least squares algorithm and the minimal least squares algorithm. The effectiveness of the proposed control scheme is demonstrated by simulations involving a redundant set of actuators. The evaluation criteria include energy consumption, robustness, as well accuracy of tracking during typical vessel operation.

3

Zastosowanie macierzy pseudo odwrotnej w metodach alokacji pędników układu dynamicznego pozycjonowania statku

Witkowska A.

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

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2014

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Nr 40

145--148

PL

Układy kontroli alokacji pędników stanowią ważną część systemów dynamicznego pozycjonowania na statku. Określają one sygnały sterujące nastawami pędników, na podstawie uogólnionego wektora sił wzdłużnej, poprzecznej i momentu skręcającego, uzyskiwanych z prawa sterowania. W artykule przedstawiono wybrane algorytmy kontroli alokacji pędników, różniące się sposobem wyznaczania macierzy pseudo odwrotnej oraz algorytm bezpośredniej alokacji. Omówiono wpływ zastosowanych metod na wydajność ekonomiczną oraz jakość regulacji układu dynamicznego pozycjonowania statkiem

EN

Control allocation systems are an important part of the dynamic positioning of ships. They define the control signals based on generalized vector of forces longitudinal, transverse and torque derived from the control law. The article presents selected control allocation algorithms, based on different ways of determining the pseudo inverse matrix to optimize the operation of these devices, and discusses the economic efficiency and control quality of the dynamic positioning system.

4

Sliding mode methods for fault detection and fault tolerant control with application to aerospace systems

Edwards C., Alwi H., Tan C. P.

International Journal of Applied Mathematics and Computer Science

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2012

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Vol. 22, no. 1

109-124

EN

Sliding mode methods have been historically studied because of their strong robustness properties with regard to a certain class of uncertainty, achieved by employing nonlinear control/injection signals to force the system trajectories to attain in finite time a motion along a surface in the state-space. This paper will consider how these ideas can be exploited for fault detection (specifically fault signal estimation) and subsequently fault tolerant control. It will also describe applications of these ideas to aerospace systems, including piloted flight simulator results associated with the GARTEUR AG16 Action Group on Fault Tolerant Control. The results demonstrate a successful real-time implementation of the proposed fault tolerant control scheme on a motion flight simulator configured to represent the post-failure EL-AL aircraft.

5

Reconfigurable control design with integration of a reference governor and reliability indicators

Weber P., Boussaid B., Khelassi A., Theilliol D., Aubrun C.

International Journal of Applied Mathematics and Computer Science

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2012

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Vol. 22, no. 1

139-148

EN

A new approach to manage actuator redundancy in the presence of faults is proposed based on reliability indicators and a reference governor. The aim is to preserve the health of the actuators and the availability of the system both in the nominal behavior and in the presence of actuator faults. The use of reference governor control allocation is a solution to distribute the control efforts among a redundant set of actuators. In a degraded situation, a reconfigured control allocation strategy is proposed based on on-line re-estimation of the actuator reliability. A benefit of incorporating reliability indicators into over-actuated control system design is the smart management of the redundant actuators and improvement of the system safety. Moreover, when the fault is severe, an adaptation approach using the reference governor is proposed. The reference governor unit is a reference-offset governor based on a discrete-time predictive control strategy. The idea is to modify the reference according to the system constraints, which become stricter after the occurrence of an actuator fault. The proposed approach is illustrated with a flight control application.