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1

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.

2

Control input limited switched reluctance motor with auxiliary sliding mode position tracking control

Tang Chuansheng, Zhang Gang, Yang Jie, Li Tao

Journal of Power Technologies

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2020

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Vol. 100, nr 4

341--350

EN

The drive system of a switched reluctance motor (SRM) is a nonlinear one with coupling between the rotor position, inductance, and flux linkage. Moreover, the system parameters change with the external environment such as temperature, humidity, and pressure. At the same time, uncertain factors including friction, torque fluctuation, and external interference in the system, reduce system stability and reliability. To effectively improve the influence of uncertain factors on the performance of an SRM system, this study proposes an auxiliary sliding position tracking method, under the condition of limited control input. First, the mathematical model of the system was established according to the structure and characteristics of an SRM.Second, an auxiliary sliding mode position tracking controller was designed by constructing the auxiliary system and utilizing the sliding mode control theory. Finally, the effectiveness and superiority of the proposed method were verified through comparison with proportional integral differential (PID) control and the traditional sliding mode control using simulation. Results demonstrate that under limited control input, the auxiliary sliding position tracking control method still delivers rapid and error-free tracking of the position and speed for the change of model parameters. The recommended scheme has a response time 2.9 times shorter than that of PID control. Furthermore,the steady-state errors of the PID control position and speed are 0.66 rad and 1.62 rad/s, respectively. The control input of the traditional sliding mode control has greater chattering than the proposed method. When the system has interference, the designed method under the condition of limited control in-put can achieve the desired tracking command within 1.7 s. The steady-state error is 0.0044 rad, and the steady-state accuracy of the developed scheme is 10.3 times higher than that of PID control. Therefore, the proposed method enjoys both high position tracking accuracy and strong robustness to external disturbances.

3

Immersive 3D visualisation for CAD/CAM

Głowacki J.

Czasopismo Techniczne. Mechanika

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2011

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R. 108, z. 4-M/1

141-146

EN

The paper briefly introduces different approaches in Virtual Reality as applied to Machine Engineering and Virtual Machining. The description of examples of state-of-the-art in the field is followed by a presentation of a novel idea to utilise simple hardware equipment to provide immersive visualisation for regular desktop computers.

PL

Artykuł zawiera krótkie wprowadzenie do zastosowań wirtualnej rzeczywistości w narzędziach Inżynierii Maszyn i Wirtualnej Obróbki. Po opisie przykładów najnowszych rozwiązań w tej dziedzinie przedstawiono nowy pomysł na uzyskanie pewnych efektów wirtualnej rzeczywistości z zanurzeniem z wykorzystaniem prostych narzędzi i zwykłych komputerów osobistych.

4

Sliding Mode Control with Fuzzy Tuning for Position Tracking of an Electro-Hydraulic Actuator

Antić D., Nikolić V., Mihajlov M., Aleksić K.

Machine Dynamics Problems

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2002

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Vol. 26, No. 1

81-93

EN

This paper considers the position control problem of an electro-hydraulic actuator subjected to parameter uncertainties and an external disturbance. The system is described by a comprehensive model that accounts for nonlinearities and friction effects. Friction in the hydraulic cylinder and load variations are taken into account as the external disturbance. The variable structure control with a sliding mode is used in the first step of the controller design. In order to overcome known drawbacks of the sliding mode control, fuzzy logic is applied. The simulation results show good tracking performance and strong robustness.