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Author

Fushun Liu

Other affiliations: Ocean University of China
Bio: Fushun Liu is an academic researcher from Qingdao University. The author has contributed to research in topics: Time domain & State-space representation. The author has an hindex of 4, co-authored 9 publications receiving 69 citations. Previous affiliations of Fushun Liu include Ocean University of China.

Papers
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Journal ArticleDOI
TL;DR: An iterative noise extraction and elimination method is proposed, to solve the difficulty of modal parameter identification caused by contaminated high-energy components in measured signals, and one can conclude that the proposed method outperforms the Fourier transform due to its limitation of fixed frequency resolution.

61 citations

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TL;DR: These monitoring campaigns of an actual in service OWT not only provide modal information support for structural maintenance and operation safety assessment, but also provide a real data reference for wind turbine design.

16 citations

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TL;DR: The proposed time-domain response estimation method provides accuracy similar to that of the regression method but outperforms the curve fitting and the realization methods, obviously because of the improperly used initial values.

7 citations

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TL;DR: Numerical results show that the proposed time-domain response estimation method can provide much more accurate time- domains responses compared with those from the traditional time- domain methods, even when the time step used is not so accurate, but also has better computational efficiency.

7 citations

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TL;DR: A new estimation method, which focuses on the efficiency of utilizing wave energy by the WUSV, is proposed and is expressed in the form of the product of several non-dimensional parameters.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: Rotor fault diagnostic techniques of a three-phase induction motor (TPIM) were presented and a method of the feature extraction of vibration signals Method of Selection of Amplitudes of Frequencies – MSAF-12 was described.
Abstract: Abstract Nowadays detection of deterioration of electrical motors is an important topic of research. Vibration signals often carry diagnostic information of a motor. The authors proposed a setup for the analysis of vibration signals of three-phase induction motors. In this paper rotor fault diagnostic techniques of a three-phase induction motor (TPIM) were presented. The presented techniques used vibration signals and signal processing methods. The authors analyzed the recognition rate of vibration signal readings for 3 states of the TPIM: healthy TPIM, TPIM with 1 broken bar, and TPIM with 2 broken bars. In this paper the authors described a method of the feature extraction of vibration signals Method of Selection of Amplitudes of Frequencies – MSAF-12. Feature vectors were obtained using FFT, MSAF-12, and mean of vector sum. Three methods of classification were used: Nearest Neighbor (NN), Linear Discriminant Analysis (LDA), and Linear Support Vector Machine (LSVM). The obtained results of analyzed classifiers were in the range of 97.61 % – 100 %.

100 citations

Journal ArticleDOI
TL;DR: Lyapunov and nonsmooth syntheses prove that the closed-loop FFE-FTC system is globally finite-time stable and achieves exact fault-tolerance and unknown rejection under input saturations.
Abstract: In this article, in the presence of unknown actuator faults, input saturations, and complete unknowns including both internal dynamics and external disturbances, exact trajectory-tracking problem of a surface vehicle (SV) is solved by creating a finite-time fault estimator based fault-tolerance control (FFE-FTC) scheme. By virtue of input saturations, smoothly saturated controls are separated from input nonlinearities including unknown faults, thereby leaving faults-mixed unknowns be exactly observed by a finite-time fault estimator (FFE). By defining an integral sliding-mode (ISM) manifold and deriving affine controls with unknown gains from smooth saturations, Nussbaum technique is deployed to synthesize a uniformly adaptive finite-time controller working in a large range outside input saturations. Within the close range where saturations are removed, an ISM-based nonsmooth controller with finite-time auxiliary compensation dynamics is devised to finely stick tracking errors to the origin. Intuitively, large- and close-range control actions are triggered by measuring the ISM error, thereby contributing to the entire FFE-FTC scheme, which achieves exact fault-tolerance and unknown rejection under input saturations. Lyapunov and nonsmooth syntheses prove that the closed-loop FFE-FTC system is globally finite-time stable. Simulation results and comparisons on a prototype SV demonstrate remarkable performance in terms of feasibly saturated controls and exact trajectory-tracking, simultaneously.

90 citations

Journal ArticleDOI
TL;DR: In this paper, a novel translation–rotation cascade control scheme is developed for path following of an autonomous underactuated ship suffering from unknown sideslip and complex disturbances.
Abstract: In this paper, a novel translation–rotation cascade control (TRCC) scheme is developed for path following of an autonomous underactuated ship suffering from unknown sideslip and complex disturbances. Salient contributions are as follows: 1) finite-time observers are devised to exactly estimate lumped unknowns including sideslip, disturbances, and virtual yaw acceleration; 2) complex unknowns are compositely compensated with finite-time convergence such that exact path following with accurate unknown rejection is achieved; 3) in lieu of detached guidance-control design in previous works, the TRCC facilitates integrated guidance-control (IGC) system in a cascade manner; 4) combining cascade analysis with Lyapunov approach, the entire IGC system is ensured to be globally uniformly asymptotically stable. Both simulation and experimental results are provided to validate the superiority of the proposed TRCC scheme.

67 citations

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TL;DR: A surge-heading guidance-based finite-time path-following control (SHG-FPC) scheme is created for an underactuated marine vehicle with complex unknowns that can greatly enhance the decision-making autonomy pertaining to guidance of kinematics and dynamics, simultaneously.
Abstract: In this paper, a surge-heading guidance-based finite-time path-following control (SHG-FPC) scheme is created for an underactuated marine vehicle with complex unknowns. In lieu of line-of-sight guidance, both surge and heading can be guided by adapting to path-following errors and this can greatly enhance the decision-making autonomy pertaining to guidance of kinematics and dynamics, simultaneously. Complex unknowns can be exactly identified by virtue of the devised finite-time uncertainty observer (FUO), by which FUO-based nonsmooth control laws are able to achieve accurate guidance tracking, and thereby, contributing to entire finite-time path-following performance with strong robustness. Simulation results demonstrate the remarkable performance of the proposed SHG-FPC scheme.

66 citations

Journal ArticleDOI
TL;DR: Simulations and comparisons in various real-world geographies demonstrate the effectiveness and superiority of the proposed DGL hybrid path planning scheme.
Abstract: In this paper, under unforeseen circumstances, a dynamics-constrained global-local (DGL) hybrid path planning scheme incorporating global path planning and local hierarchical architecture is created for an autonomous surface vehicle (ASV) with constrained dynamics. By encapsulating ASV safety area into Theta*-like heuristics, global path planning algorithm is developed to optimally generate sparse waypoints which are sufficiently clear to constraints. To deal with dynamically unforeseen environments, a local hierarchy is established by fuzzy decision-making (FDM) and fine dynamic window (FDW) layers, which are responsible for large- and close-range collision avoidance, respectively, by governing surge and yaw velocity guidance signals. With the aid of the FDW, constrained dynamics pertaining to the ASV, i.e., actuatable surge/yaw velocities and accelerations, are elaboratively embedded into local path planning, which in turn governs trackable collision-avoidance local path. By inserting virtual waypoints onto the globally optimal path, a seamless interface between global and local path-planning mechanism is devised, and thereby contributing to the entire DGL hybrid path planning scheme. Simulations and comparisons in various real-world geographies demonstrate the effectiveness and superiority of the proposed DGL hybrid path planning scheme.

61 citations