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1

Sliding Mode Control-Based MPPT and Output Voltage Regulation of a Stand-alone PV System

Manuel Nelson Luis, İnanç Nihat

Power Electronics and Drives

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2022

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Vol. 7 (42)

159--173

EN

When it comes to reducing emissions caused by the generation of electricity, among different renewable energy sources, the solar energy gains prominence, due to its geographical availability, simplicity of implementation, and absence of physical moving parts. However, the performance of photovoltaic systems is dependent on environmental conditions. Depending on temperature and solar irradiation, the photovoltaic (PV) system has an operating point where maximum power can be generated. The techniques that are implemented to find this operating point are the so-called maximum power point tracking (MPPT) algorithms. Since weather conditions are variable in nature, the output voltage of the PV system needs to be regulated to remain equal to the reference. Most of the existing studies focus either on MPPT or on voltage regulation of the PV system. In this paper, the two-stage PV system is implemented so that both MPPT and voltage regulation are achieved simultaneously. Additionally, an improved version of the perturb and observe (P&O) algorithm based on artificial potential fields (APF), called APF-P&O, is presented. According to the results of the simulations carried out in MATLAB/Simulink software, the APF-P&O method is more efficient than the conventional method.

2

Self-adaptive asymmetrical artificial potential field approach dedicated to the problem of position tracking by nonholonomic uavs in windy enivroments

Kownacki Cezary

Acta Mechanica et Automatica

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2021

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Vol. 15, no. 1

37--46

EN

Artificial potential fields (APFs) are a popular method of planning and controlling the path of robot movement, including unmanned aerial vehicles (UAVs). However, in the case of nonholonomic robots such as fixed-wing UAVs, the distribution of velocity vectors should be adapted to their limited manoeuvrability to ensure stable and precise position tracking. The previously proposed local asymmetrical potential field resolves this issue, but it is not effective in the case of windy environments, where the UAV is unable to maintain the desired position and drifts due to the wind drift effect. This is reflected in the growth of position error, which, similar to the steady-state error in the best case, is constant. To compensate for it, the asymmetrical potential field approach is modified by extending definitions of potential function gradient and velocity vector field (VVF) with elements based on the integral of position tracking error. In the case of wind drift, the value of this integral increases over time, and lengths and orientations of velocity vectors will also be changed. The work proves that redefining gradient and velocity vector as a function of position tracking error integrals allows for minimisation of the position tracking error caused by wind drift.

3

Motion control and collision avoidance algorithms for unmanned surface vehicle swarm in practical maritime environment

Zhuang Jiayuan, Zhang Lei, Qin Zihe, Sun Hanbing, Wang Bo, Cao Jian

Polish Maritime Research

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2019

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nr 1

107--116

EN

The issue of controlling a swarm of autonomous unmanned surface vehicles (USVs) in a practical maritime environment is studied in this paper. A hierarchical control framework associated with control algorithms for the USV swarm is proposed. In order to implement the distributed control of the autonomous swarm, the control framework is divided into three task layers. The first layer is the tele-operated task layer, which delivers the human operator’s command to the remote USV swarm. The second layer deals with autonomous tasks (i.e. swarm dispersion, or avoidance of obstacles and/or inner-USV collisions), which are defined by specific mathematical functions. The third layer is the control allocation layer, in which the control inputs are designed by applying the sliding mode control method. The motion controller is proved asymptotically stable by using the Lyapunov method. Numerical simulation of USV swarm motion is used to verify the effectiveness of the control framework.

4

Evaluation of near-collisions in the Tagus River Estuary using a marine traffic simulation model

Rong H., Teixeira A., Soares C. G.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2015

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nr 43 (115)

68--78

EN

This paper evaluates near ship-ship collision situations in the Tagus River Estuary using a simulation model of ship navigation in restricted waters. The simulation model consists of a ship collision avoidance model based on the Artificial Potential Field (APF) method, which has been improved to account for the lateral distribution of traffic along the route, the ship type and length and speed development of the ships along the trajectory. AIS data of ships entering and leaving the port of Lisbon are analysed to obtain the main characteristics of traffic parameters used as input for the traffic simulation model, such as: the routes of the vessels, speed distribution along the routes, traffic density and characteristics of the ships in each route, among others. First, the improved model of ship navigation and the Monte Carlo simulation technique are used to simulate the marine traffic in the Tagus River Estuary. Then, the concept of “ship domain” is used as collision criterion to determine the number of near collisions and the locations where they are most likely to occur. Finally, the simulation results are compared to the ones obtained from raw AIS data to assess the capability of the simulation model for marine traffic risk analysis.

5

Motion planning for wheeled mobile robot using potential field method

Żylski W.

Journal of Theoretical and Applied Mechanics

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2004

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Vol. 42 nr 3

695-705

EN

A potential field method in the real-time approach toward avoidance of obstacles for a mobile robot has been developed. A collision-free path and goal-seeking behaviour are calculated using an artificial potential field method. The proposed reactive nevigation approach is based on the coordination of elementary responses. To avoid convex obstacles, the navigator generates a "reaching the middle of the collision-free space" and goal-seeking behaviours. A control strategy based on artificial potential fields that generates a trajectory to be followed by a mobile robot that represents a reference for the robot at the same time is proposed. The effectiveness of the proposed method is numerically verified by a series of experiments on the emulator of the wheeled mobile robot Pioneer-2DX.

PL

W pracy rozważa się problem generowania bezkolizyjnej trajektorii ruchu mobilnego robota w czasie rzeczywistym z zastosowaniem sztucznego pola potencjalnego. Analizuje się elementarne zachowanie mobilnego robota, takie jak: osiągnij środek wolnej przestrzeni oraz idź do celu. Wygenerowana trajektoria ruchu umożliwiająca omijanie przeszkód wypukłych uwzględnia elementarne zachowania robota. Stanowi ona trajektorię zadaną, która realizuje układ sterowania. Efektywność zaproponowanego rozwiązania została numerycznie zweryfikowana na emulatorze mibilnego robota kołowego Pioneer-2DX.