Noise and vibration assessment of permanent-magnet synchronous motors based on matching pursuit

This paper presents a noise and vibration assessment scheme for the elevator permanent-magnet synchronous motors (PMSMs) based on matching pursuit (MP) with carefully selected atoms. The atomic dictionary is developed by considering of the complication of electromagnetic noise and vibration of the elevator PMSMs. After identifying the natural frequencies by modal testing and computing the characteristic electromagnetic frequencies of the PMSMs, the impulse energy ratio based on transient components, which are extracted by projecting on the selected atoms based on the MP method, are computed and used to assess the machines. The assessing results indicate that the transient components can accurately represent the electromagnetic impulse since the distorted magnetic fields and the features are robust for quality inspection of the elevator PMSMs

A planar 3-DOF nanopositioning platform with large magnification

AbstractPiezo-actuated flexure-based precision positioning platforms have been widely used in micro/nano manipulation. A conventional major challenge is the trade-off between high rigidity, large magnification, high-precision tracking, and high-accuracy positioning. A compact planar three-degrees-of-freedom (3-DOF) nanopositioning platform is described in which three two-level lever amplifiers are arranged symmetrically to achieve large magnification. The parallel-kinematic configuration with optimised sizes increases the rigidity. Displacement loss models (DLM) are proposed for the external preload port of the actuator, the input port of the platform and the flexible lever mechanism. The kinematic and dynamic modelling accuracies are improved by the compensation afforded by the three DLMs. Experimental results validate the proposed design and modelling methods. The proposed platform possesses high rigidity, large magnification, high-precision circle tracking and high-accuracy positioning

Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture

For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications

On the General Solution of Impulsive Systems with Hadamard Fractional Derivatives

This paper is concerned with the solution for impulsive differential equations with Hadamard fractional derivatives. The general solution of this impulsive fractional system is found by considering the limit case in which impulses approach zero. Next, an example is provided to expound the theoretical result

Multiplication Operator with BMO Symbols and Berezin Transform

We discuss multiplication operator with a special symbol on the weighted Bergman space of the unit ball. We give the necessary and sufficient conditions for the compactness of multiplication operator on the weighted Bergman space of the unit ball