Maria do Rosário Calado

An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

This 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.

Vibration analysis of a linear switched reluctance actuator

The main drawback of switched reluctance machines acceptance is the acoustic noise produced. Research efforts to minimize vibrations in this type of electric machines concentrate mainly on the rotational configuration and only a few works can be found focusing on linear actuators. This paper presents the results of finite elements analysis of vibration frequencies for a linear switched reluctance actuator. The results obtained serve as reference and support for experimental modal analysis and characterization of vibrations and acoustic noise in this type of machines.

Numerical Modal Analysis of Vibrations in a Three-Phase Linear Switched Reluctance Actuator

This 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 1.2u2009kHz 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.

Particle Swarm Optimization for photovoltaic model identification

This paper proposes a comprehensive modeling and parameters extraction method of solar photovoltaic module based on the Particle Swarm Optimization algorithm. The characteristic curves of photovoltaic panel are obtained by using only the information provided by the manufacturer data-sheet, avoiding the need to carry out experimental data. The performance and the accuracy of the proposed method are evaluated by applying the one-diode model and the results are compared with those obtained by the well-known Lambert W function. The proposed method shows a higher performance.

Glowworm Swarm Optimization for photovoltaic model identification

This paper presents a new algorithm for finding the parameters that characterize a photovoltaic panel by using the Glowworm Swarm Optimization algorithm. This new algorithm shows great simplicity, flexibility and precision, being able to precisely locate the global optimum point or multiple global optimum points, independently of the initial conditions. The approach here adopted allows the utilization of the algorithm in several existing models to characterize a photovoltaic panel in the current literature.

A Simple yet Effective Semi-Anechoic Chamber for the Acoustic Characterization of an LSRA

This 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 peoples activities, other machinery operation, etc. The average attenuation achieved is better than 30 dB for a noise source place 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.

Improved distributed system for analysis of vibrations in linear switched reluctance actuators

Research efforts have been taken to characterize the vibrations in switched reluctance machines but only a few works focus on the linear configuration. This paper proposes a realtime data acquisition system to monitor and analyze the vibrations in this type of machines with special focus on the linear switched reluctance actuator. The system is based on the Texas Instruments MSP430F54xx family of microcontrollers and comprises a modular network of accelerometer sensors, distributed along the mechanical structure of the machine. The sensors modules communicate with the Host PC via USB 2.0 protocol and data is collected and processed in MATLAB®.

The IEEE Model for a Ground Rod in a Two Layer Soil – A FEM Approach

The calculation of a ground electrode resistance, using a two layer soil model, has been widely presented in literature. Several methods had been used. Formulas for grid in two layers soil using the synthetic-asymptote approach have been developed in (Salama et al., 1995). Berberovic explored the Method of Moments in the calculation of ground resistance, using higher order polynomials approximation in the unknown current distribution in (Berberovic et al., 2003), and the Galerkin’s Moment Method with a variation was used in (Sharma & De Four, 2006). Another theoretical tool commonly used is the Boundary Element Method, as in (Colominas et al., 1998, 2002a, 2002b; Adriano et al., 2003). These authors transformed the differential equation that governs the physical phenomenon into an equivalent boundary integral equation. The Matrix/Integration Method for calculating the mutual resistance segment in one and two layered soil was adopted by (Coa, 2006) and an optimised method of images for multilayer soils was used in (Ma et al., 1996). Even in the study of ionization phenomena, the two layer ground model was used in (Liu et al., 2004). In general these works used the theory of images, which implies infinite series for the expanded Green function as in (Berberovic et al., 2003). Recently, a work presented the effect of low resistance materials filling in a pit surrounding a rod, working with two different soil resistivity’s (Al-Arayny et al., 2011). This type of research was also presented in (Zhenghua et al., 2011), that even considered the use of electrolytic materials. A Finite Element Method (FEM) application to grounding can also be found in (Manikandan et al., 2011) to the analysis of wind turbines grounding. In this chapter the FEM is presented in a theoretical basis for cylindrical symmetry problems, using a ground rod resistance calculation as an example. Comparison with experimental result is also made.

Sliding Mode Position Controller for a Linear Switched Reluctance Actuator

More than never, the automation of industrial processes has high technical requirements. Today, most of the fabrication processes must operate with an efficient and precise control of different parameters like: velocity, position and torque. Simultaneously, the controller must be immune enough to the outside world perturbations typically found in industry. At the same time, the kind of movement required by today processes is beyond the simple rotational configuration. Linear actuators are making their appearance in the industry, being already a reality and a truly available option that designers and engineers can consider. The traditional conversion method used to transform rotational motion into linear displacement is no more acceptable. In the old days, linear displacement was obtained from a rotational motor shaft, after mechanical conversion by a specific mechanism containing pulleys, worm gears and belts. The presence of these components diminishes the robustness and reliability of the industrial processes. The ac induction motor has good robustness and low fabrication cost. Over the past decades it has replaced, with great success, the conventional brushed DC motor in servo-type applications. Although this change allowed process reliability improvement, for instance, problems related with the motor brushes are eliminated, the introduction of an electronic power drive increases systems complexity, raising other problems. The switched reluctance machine (SRM) can be classified as a current-controlled stepping motor of the variable-reluctance type. This technology is one of the most recent options in the field of variable speed actuators. Consumer products, aerospace, and automobile industries are today taking advantage from SRM drives characteristics. Advances in power electronics and the use of microelectronics and microprocessors allowed the development of different control strategies, such as nonlinear, adaptive, variable structure, and fuzzy, contributing to the popularity that SRM drives actually enjoy. The SRM is a rugged and reliable actuator, that can be produced at a low cost, presents a simple and robust structure and can operate in a wide speed range, in all four-quadrant, without a considerable reduction of efficiency. These characteristics make it an attractive alternative to permanent-magnet brushless and induction motor drives (Corda, J. et al. (1993)). Its main constructive characteristic is the absence of winding on the rotor of the machine, giving it a potential advantage over conventional machines. Furthermore, the SRM

Instrumentation Requirements for Automatic Power Quality Analysis and Dissemination

Nowadays, electrical energy quality in power systems is a major concerning problem [1], and must be monitored and analyzed. In the recent past, the power quality supplied to an electrical system wasn’t a priority, and only had reflection in system reability. Recently, the scenario tends to be changing and is necessary to identify, process, save and disseminate, preferentially in an automated way, the anomalies, causes and origins. This is the only way to involve all entities within the electrical energy sector, working in co-operation to achieve the required power quality. In the past, few applications were sensitive to power supply’s disturbances. Nowadays, because of the electronic equipment proliferation, it is necessary to execute a rigorous control of the energy quality supplied to the processes. The great majority of the equipments that includes microprocessed components, or any other kind of electronic regulation and command, are sensitive to power supply disturbances. However, they are also responsible for the energy quality deterioration supplied to other devices sharing the same installation. This circumstance can, in a limit situation, provoke disturbances in neighboring plants.