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- A Simple yet Effective Semi-Anechoic Chamber for the Acoustic Characterization of an LSRAPublication . Salvado, José; Calado, M. do Rosário; Espírito Santo, AntónioThis paper presents a simple and cost effective solution of a semi-anechoic chamber suitable for the acoustic noise characterization of a Linear Switched Reluctance Actuator (LSRA). Using simple construction and assembling techniques, and low-cost materials, it allows significant acoustic isolation characteristics from the environmental noise, caused by people´s activities, other machinery operation, etc. The average attenuation achieved is better than 30 dB for a noise source placed at 1 meter distance from its walls. The overall test results demonstrate an affordable yet effective semi-anechoic chamber solution, and prove its adequacy for the specific purpose of characterizing a LSRA in terms of the acoustic noise produced.
- An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance ActuatorPublication . Salvado, José; Espírito Santo, António; Calado, M. do RosárioThis paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.
- Numerical Modal Analysis of Vibrations in a Three-Phase Linear Switched Reluctance ActuatorPublication . Salvado, José; Calado, M. Do Rosário; Espírito Santo, António; Guerman, AnnaThis paper addresses the problem of vibrations produced by switched reluctance actuators, focusing on the linear configuration of this type of machines, aiming at its characterization regarding the structural vibrations. The complexity of the mechanical system and the number of parts used put serious restrictions on the effectiveness of analytical approaches. We build the 3D model of the actuator and use finite element method (FEM) to find its natural frequencies. The focus is on frequencies within the range up to nearly 1.2 kHz which is considered relevant, based on preliminary simulations and experiments. Spectral analysis results of audio signals from experimental modal excitation are also shown and discussed. The obtained data support the characterization of the linear actuator regarding the excited modes, its vibration frequencies, and mode shapes, with high potential of excitation due to the regular operation regimes of the machine. The results reveal abundant modes and harmonics and the symmetry characteristics of the actuator, showing that the vibration modes can be excited for different configurations of the actuator. The identification of the most critical modes is of great significance for the actuator’s control strategies. This analysis also provides significant information to adopt solutions to reduce the vibrations at the design.