A numerical parameter match approach for harmonic retrieval is presented to improve the demerits of harmonic retrieval methods, such as complicated calculation, low precision and false frequency appearance. The theory deduction and computer simulation are given to show the validity of the approach, and the implementary steps are offered. Based on the characteristics of the motor vibration fault signals exhibiting cyclostation and harmonic information, the numerical harmonic retrieval method can not only search fixed frequency but also match fault characteristic frequency. By the amplitude modulation fault examples, the degrees of modulation variation are employed to validate the availability of the approach in rotating machinery fault diagnosis.
REBCO coated conductors (REBCO CCs), the second-generation high-temperature superconducting (2G HTS) tapes, are subjected to electromagnetic stress in an electromagnetic environment, and tremendous stress can damage tapes such that lose their superconductivity. This paper uses the numerical method to simulate the electromagnetic response and related mechanical properties of the quasi-isotropic strand (Q-IS) under the applied magnetic field and carrying current and their combination. The simulation is based on the Kim model in which the critical current density is related to the magnetic field. First, the stress distribution of the superconducting core inside the Q-IS under the applied magnetic field and if transport current is given. According to the different magnetic field amplitudes and current amplitudes, the influence of the copper sheath and the filling layer thickness on the maximum stress of the Q-IS is studied. Also calculated the current distribution, magnetic field penetration, and stress distribution of the Q-IS under the conditions of transporting direct current (DC) and applying a 2 Hz sinusoidal alternating current (AC) magnetic field. The performance of the Q-IS is entirely different in the rising and falling durations of the magnetic field. Stress concentration occurs at the four corners of the superconducting core. The left and right sides of the superconducting core with relatively large stress and deformation are easily damaged.
In order to realize high speed control of some ac servo system, aimed at all kinds of uncertain factors such as greatly changing moment and torque, and strong impact torque. Therefore, for gaining good speed tracking characteristics, adaptive disturbance observer is adopted to observe load torque disturbance and speed variation. Stability of closed loop system is guaranteed by design of control tractics to satisfy track control requests of rocket launcher servo system. Simulation results indicate that this method can ideally observe disturbance and reduce output of controller, thus control performance of the system is improved and is greatly meaningful.
In order to realize high precision position tracking control in some dc servo system, aimed at all kinds of uncertainties, a disturbance torque compensation control tactics is put forward. In other words, friction model is approximated online by fuzzy system and identification result is taken as compensation item of control algorithm. Besides, adaptive fuzzy compensation PID algorithm is utilized. Simulation results show that compared with conventinal PID control, this control tactics can enhance dynamic performances and steady-state precision, satisfying performance requests.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.