Nebojsa Pjevalica

Analog Circuitry for BLDC Motor Magnetic Saturation Diagnostic

A novel method for diagnostic of the BLDC motor magnetic saturation is proposed. It comprises of analog amplifier in the role of pure sinusoidal current source, measurement subsystem and proposed acquisition which reliably detects signal asymmetry which is directly correlated with coil saturation. Practical experimental results are presented as proof of concept with several different current excitation levels.

An Approach to Improvement of Students Learning of Computer System Engineering

This paper presents an approach to the study programs applied for the subject Logic Design of Computer Systems II. Study program of this subject is based on unified embedded engineering learning platform, E2LP. E2LP intended to cover complete process of embedded systems learning, considering modular approaches for unifying education in relevant embedded system technologies. Study approach in this subject intends to be a step forward in helping students to adopt knowledge better and to have stronger understanding of the complex and multidisciplinary approach in this course. This implies splitting course in two parts, one in which the students are introduced to the environment and taught how to use it, and second in which students are fulfilling the specific task with minor assistant help.

Real time FPGA implementation of brushless DC motor control using single current sensor

In modern industry power consumption is becoming one of the most important constraints during the development phase of the product. In motor industry, significant part of the power consumption improvement can be done in motor control. Brushless dc (BLDC) motor drives are penetrating the market rapidly. Heating, ventilation and air conditioning (HVAC) systems use conventional motor drive technology and the machines found in these devices are characterized by low efficiency and high maintenance. BLDC motor drives are characterized by higher efficiency, lower maintenance and higher cost. This paper presents the analysis, design, and implementation of a cost-effective control technique for a low cost solution, six switch three-phase inverter brushless dc motor drive using single current sensor for current control. Various parameters defined optimization path for target drive solution. Also, basic framework for low cost BLDC control IC is presented. The controller is modeled and the concept is proven using simulator. Then the verification and feasibility study are done by using field-programmable gate array prototyping on the custom board made for this research. Final simulation results along with prototype operation measurements are presented as well.

Influence of Signal Stationarity on Digital Stochastic Measurement Implementation

The paper presents the influence of signal stationarity on digital stochastic measurement method implementation. The implementation method is based on stochastic voltage generators, analog adders, low resolution A/D converter, and multipliers and accumulators implemented by xa0Field-Programmable Gate Array (FPGA). The characteristic of first implementations of digital stochastic measurement was the measurement of stationary signal harmonics over the constant measurement period. Later, digital stochastic measurement was extended and used also when it was necessary to measure time-series of non-stationary signal over the variable measurement time. The result of measurement is the set of harmonics, which is, in the case of non-stationary signals, the input for calculating digital values of signal in time domain. A theoretical approach to determine measurement uncertainty is presented and the accuracy trends with varying signal-to-noise ratio (SNR) are analyzed. Noisy brain potentials (spontaneous and non-spontaneous) are selected as an example of real non-stationary signal and its digital stochastic measurement is tested by simulations and experiments. Tests were performed without noise and with adding noise with SNR values of 10dB, 0dB and -10dB. The results of simulations and experiments are compared versus theory calculations, and comparasion confirms the theory.

Magnetic saturation of permanent magnet motor coil as key effect for initial rotor position detection

Permanent magnet (PM) motors, due to its simplicity, reliability and overall efficiency are currently taking most wanted epithet in the number of consumer appliances. In recent two decades a lot of scientific papers were published regarding sensor-less control of permanent magnet DC motors. One of the most critical challenges is start from the stand still, with or without load, due to absence of back electromotive force in the motor coils. Core magnetic effect which enables detection of position, when motor is still, is based on magnetic saturation. Aim of this paper is to give magnetic explanation of this phenomena, which is generally neglected in most of motor control related textbooks and papers as well, also most of the motor models are based on linear magnetic approximation of the coils, hiding this key effect which provides information about initial position.

An approach to modeling the hysteresis in ferromagnetic by adaptation of Preisach model

In this paper we present our work on adaptation of Preisach Hysteresis Model to better represent naturally occurring hysteresis in ferromagnetic materials. Presented model is rate independent and one-dimensional. The model takes a hybrid theoretical-empirical approach by taking maximal hysteresis loop to calibrate the canonical Preisach model. Quality of the modeled data is discussed and ways to provide a more precise model suggested. Motivation for the work was to provide free open source hysteresis model for our own experimentation, but also for others to experiment and possibly improve.

Design and Modelling of an Enclosed Array of Square Spiral Antennas for Microwave Tomography

Microwave tomography is a microwave imaging method in which the resolution is not limited by wavelength, but rather by measurement noise and modelling errors. Inversion algorithm is used for obtaining an image from the measured scattered waves. Performance improvement of the inversion algorithm is introduced by approximately modelled antennas as a point, line or plane source. Such modelling of antennas introduces modelling errors. Antenna array in the unshielded measurement chamber will pick up external interference, as well as backscattering of array’s own radiation. Multipath occurring in measurement chamber has a large impact on the measurement performance. The wave propagated through the air and reflected from the chamber walls could mask a weaker wave scattered by the object under imaging. Also, a larger number of the antennas improves inversion and gives a more accurate image. This paper proposes a novel design of enclosed measurement antenna array for microwave tomography. To obtain an accurate and efficient antenna model in 3D FDTD, a square spiral wire antenna is used in this design. A metal shield protects the process of measurement from external interference and backscattering. Between the antenna array and the metal shield an absorption wall is introduced, which decreases multipath and partially prevents signal masking. Square spiral wire antennas are overlapped and packed, giving a larger number of antennas in the same space. Enclosed antenna array is modelled in 3D FDTD. Proposed antenna array is compared with solutions found in literature. Comparison is done using metrics relevant for antenna array measurement in microwave tomography. DOI: http://dx.doi.org/10.5755/j01.eie.23.2.17999

USB controlled relay switch

This paper describes development of device that allows control of external devices(turn on/off) with PC via USB communication. Paper includes overview of the existing solutions, description of the hardware and software solution of the implemented prototype along with verification details.

Verification of frequency analysis experimental setup

In a variety of engineering tasks, accurate measurement of signal spectrum presents necessary requirement. Hardware bring-up with noise sources tracing, through DC power sources validation and profiling, AD and DA signal conversion, communication channels verification, mutual units influence checks and many other applications lean on frequency analysis results. In many real life scenarios engineers take frequency spectrum results from the measurement units as is, without deeper investigation abut measurement uncertainty, especially related to ratio between signal period and windowing function length which could introduce significant differences. Aim of this paper is to highlight two things, first is advantage of automated custom tailored test setup, which decreases probability of gross errors and second is error validation of the harmonic content of complex periodical signals. Digital high-end oscilloscope with embedded FFT function including several windowing functions is used as test unit in automation process and also for the measurement error investigation.

FPGA based development platform for implementation of brushless DC motor control

Development of motor control techniques in last decade improved motor efficiency and wider usage area of BLDC motors. In modern industry one of the most important constraints is the product price. In motor industry there are not many application specific integrated circuits (ASIC) solutions for motor control. One of reasons is very high price of ASIC development and its validation and production. To decrease the development time and time needed for validation a custom FPGA platform can be used. With the prices of FPGA components which are decreasing rapidly, such platform can even become a commercial solution. Modular and flexible design offers the opportunity to use various approaches during the development phase. Such embedded system is not designed for general processing but for specific application which makes it a good starting point in the ASIC development. This paper presents design and implementation of an FPGA based development platform for Brushless DC (BLDC) motor control using Xilinx FPGA - Virtex6. Experimental verification is performed on Hall sensor control application, as on of the most common motor control configurations.