Current Issue : January - March Volume : 2021 Issue Number : 1 Articles : 5 Articles
The dynamic behavior of structures with piezoelectric patches is governed by partial differential equations with strong singularities.\nTo directly deal with these equations, well adapted numerical procedures are required. In this work, the differential quadrature\nmethod (DQM) combined with a regularization procedure for space and implicit scheme for time discretization is used. The\nDQM is a simple method that can be implemented with few grid points and can give results with a good accuracy. However, the\nDQM presents some difficulties when applied to partial differential equations involving strong singularities. This is due to the\nfact that the subsidiaries of the singular functions cannot be straightforwardly discretized by the DQM. A methodological\napproach based on the regularization procedure is used here to overcome this difficulty and the derivatives of the Dirac-delta\nfunction are replaced by regularized smooth functions. Thanks to this regularization, the resulting differential equations can be\ndirectly discretized using the DQM. The efficiency and applicability of the proposed approach are demonstrated in the\ncomputation of the dynamic behavior of beams for various boundary conditions and excited by impulse and Multiharmonics\npiezoelectric actuators. The obtained numerical results are well compared to the developed analytical solution....
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Flight safety is of vital importance for tilt-rotor unmanned aerial vehicles (UAVs), which can take off and land vertically as well as\ncruise at high speed, especially in different kinds of complex environment. As being the executor of the flight control, the actuator\nfailure will directly affect the controllability of the tilt-rotor UAV, and it has high probability of causing fatal personal injury and\nfinancial loss. However, due to the limitation of weight and cost, small UAVs cannot be equipped with redundant actuators.\nTherefore, there is an urgent need of fault detection and diagnosis method for the actuators. In this paper, an actuator fault\ndetection and diagnosis (FDD) method based on the extended Kalman filter (EKF) and multiple-model adaptive estimation\n(MMAE) is proposed. The actuator deflections are added to the state vector and estimated using EKF. The fault diagnosis\nalgorithm of MMAE could assign a conditional probability to each faulty actuator according to the residual of EKF and diagnose\nthe fault. This paper is structured as follows: first, the structure and model of tilt-rotor UAV actuator are established. Then, EKF\nobservers are introduced to estimate the state vector and to calculate residual sequences caused by different faulty actuators. The\nresiduals from EKFs are used by fault diagnosis algorithm to assign a conditional probability to each failure condition, and fault\ntype can be diagnosed according to the probabilities. The FDD method is verified by simulations, and the results demonstrate that\nthe FDD algorithm could accurately and efficiently diagnose actuator fault without any additional sensor....
An optimal control strategy for the random vibration reduction of nonlinear structures using piezoelectric stack inertial\nactuator is proposed. First, the dynamic model of the nonlinear structure considering the dynamics of a piezoelectric stack\ninertial actuator is established, and the motion equation of the coupled system is described by a quasi-non-integrable-\nHamiltonian system. Then, using the stochastic averaging method, this quasi-non-integrable-Hamiltonian system is\nreduced to a one-dimensional averaged system for total energy. The optimal control law is determined by establishing and\nsolving the dynamic programming equation. The proposed control law is analytical and can be fully executed by a\npiezoelectric stack inertial actuator. The responses of optimally controlled and uncontrolled systems are obtained by\nsolving the Fokkerâ??Planckâ??Kolmogorov (FPK) equation to evaluate the control effectiveness of the proposed strategy.\nNumerical results show that our proposed control strategy is effective for random vibration reduction of the nonlinear\nstructures using piezoelectric stack inertial actuator, and the theoretical method is verified by comparing with the\nsimulation results....
An intelligent proportional-derivative sliding mode controller (i-PDSMC) is presented to overcome the unmodeled\ncomplexity of the robot manipulator under an actuator. i-PDSMC is a free model intelligent control based on the ultralocal,\nsliding mode, and PD control structure. A stability condition is determined by the Lyapunov theory. A comparative study\nbetween a classical PD, an intelligent PD control, and i-PDSMC is done through a robot manipulator under actuators. The\nsimulation results prove that the proposed controller is more robust to trajectory tracking under parameter variations and\nexternal disturbances....
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