Hrvoje Dzapo

Digital Measuring System for Monitoring Motor Shaft Parameters on Ships

The robust measuring system for the continuous monitoring of the ship motor shaft average torque, power, and rotational speed was developed and tested. The system was designed for permanent installation in ships under realistic working conditions. The strain gage sensor is employed to measure the torque, whereas the shaft rotational speed is measured by the inductive proximity switch. The strain gage signal conditioning circuit design was highly simplified by using a high-resolution SigmaDelta A/D converter (ADC). Such an approach minimizes the overall number of analog components and the input measuring chain errors. A contactless power transmission subsystem was developed based on the specifically designed rotary transformer operating at low frequency. Strain measurement results are transmitted over the near-field low-frequency capacitive link by using a specifically designed communication protocol based on the digital modulation principle. The receiver microprocessor-based unit processes the measured data and transmits the results to the monitoring human-machine interface over some commonly used industrial analog and digital communication protocols. The principal advantages of the novel measuring system design over some state-of-the-art commercial solutions are simplicity, higher accuracy, stability, reliability, simplified calibration procedure, and contactless signal transmission and processing completely in a digital form, which, hence, reduces the most common shortcomings of similar analog-based systems.

Smart home automation system for energy efficient housing

This paper presents a concept and implementation of modern smart monitoring and control system for building automatization. The system is designed to enable significant reduction of energy consumption and carbon footprint by increasing the energy efficiency of the building under control. The system consists of a Linux-based remotely accessible main embedded control unit, a custom designed programmable logic controller named littlePLC, and a propriatery low-power Wireless Sensor Network (WSN). The energy flow is optimized by using a Model Predictive Control (MPC) algorithm that runs on the main control unit. The main control unit communicates with littlePLC, which serves as an interface that controls the parameters and state of HVAC systems in the building. The feedback information for MPC is gathered by means of the WSN, which consists of various sensor node types, such as temperature, air pressure, humidity, VOC and CO2. The WSN nodes are connected in a star type network topology, with a communication HUB connected to the main control unit. The information gathered by WSN are used in the MPC algorithm in order to calculate and estimate the requirements for heat corrections, with respect to ventilation and weather predictions.

Portable wireless measuring system for monitoring motor shaft parameters

A prototype of a portable wireless measuring system for monitoring motor shaft torque, power and rotational speed was developed and tested. The system was designed to offer great flexibility for a wide variety of test and research applications as well as having broad monitoring parameter ranges. Strain gauge sensors, placed onto the revolving shaft along with a wireless radio-frequency transmitter, are employed to measure torque. Shaft rotational speed is measured by using a rotary encoder. Torque and power are calculated automatically on the receiver side from samples processed in real time and displayed to the user. Moreover, the system provides analog and digital outputs of the shaft vibration waveform for oscilloscope observation or recording on a personal computer in a digital format.

IBMS - Intelligent Building Management System Framework

The ubiquitous availability of Internet connection in residential and industrial environments enabled limitless possibilities of connecting local sensor networks using various cloud technologies to provide value-added services for intelligent management of building facilities. One of the challenges in implementing a distributed smart building management systems is to enable interoperability of many different computational platforms by providing a common protocol across the wide range of devices, with different capabilities and resources. In this paper, we present an infrastructure architecture and software framework for building large interconnected sensor networks, with primary application for building management. We establish the terminology, system elements specification, functional description of different hardware and software building blocks, define a thin common interoperability layer with established message semantic and event-driven framework, providing a modular architecture that is easy to adapt and extend. Sensor nodes are connected through the data aggregators, which communicate with the remote scalable cloud service, designed for large sensor data collecting, syncing, storage, and event processing. For testing purposes, we implemented a demo system based on open source technologies that are integrated with our IBMS framework.

Earth surface potentials measuring device for large grounding systems testing

Substation grounding system characteristics need to be examined periodically in order to check that protective functions have not been degraded over a longer period of time. The most important safety parameters are the values of touch and step voltages. However, the surface potential distribution contains additional information concerning grounding grid status and possible characteristics degradation trends. Inspection procedure needs to be well prepared prior to actual measurement during which the great deal of measuring information has to be acquired. General-purpose multimeters are inconvenient for the efficient conduction of measuring procedure and data management tasks. A novel application-specific measuring system for earth surface potentials measurement needed to be developed and realized. It consists of the smart measuring device accompanied with the integrated program environment on a personal computer for inspection planning and analysis.

UWB localization for discrimination-enabled metal detectors in humanitarian demining

Handheld metal detectors are ubiquitous devices in humanitarian demining. They are sensitive to extremely small metallic objects as in low-metallic content landmines. However, this leads to enormous false alarm rates (1 to 1000). Recent research in electromagnetic induction techniques for discrimination of hazardous metallic targets and clutter gives rise to a hope of faster, smarter and safer mine detection. These techniques require that position of the metal detectors sensor head be known to sub-centimeter accuracy. To this aim, we present and evaluate an ultra-wide bandwidth positioning embedded system. We evaluate its precision and accuracy, and show that it can be used for tracking of the sensor head with at least 40 Hz positon refresh rate. The achieved measurement uncertainty is better than 10 cm. We discuss the further improvements that can be made in such a localization system.

Capacitive sensor for respiration monitoring

Respiration monitoring of patients with chronic diseases, children, elderly, or sportsmen can be a useful tool in health condition assessment, early diagnosis of various diseases, and real-time prediction of possibly dangerous health conditions. In this paper we present a low-cost solution of respiration monitoring system, based on a custom designed capacitive sensor, which comprises of two moveable electrodes, mounted on a rigid belt attached around the persons chest. One electrode is fixed while the other one moves in a rhythm of breathing, with restriction of movement in one axis only. The electrode geometry was optimized by numeric electromagnetic simulations to provide linearity and measurable level in change of capacitance, even for case of shallow breathing. Input measuring chain is based on capacitance-to-digital (CDC) integrated circuit and it is able to capture the changes of up to several hundreds of femtofarads in full scale, with enough resolution to enable breathing rate detection, and discrimination of cases of deep, shallow, and no breathing by signal processing algorithms. The prototype measurement system was designed and tested in laboratory on several test subjects. Preliminary experiments showed that the proposed measurement system for respiration monitoring can be used for low-cost and low-power integrated solution for continuous monitoring of patients respiration.

Multielectrode measurement of conductive liquid layer thickness

This paper presents a simple low-cost measurement method for determination of a conductive liquid layer thickness with an unknown conductivity, by means of measuring the resistance between pairs of electrodes arranged in a planar multielectrode configuration. The measurement method tolerates unknown layer conductivity variations over a few orders of magnitude, without a significant impact on the measured layer thickness uncertainty. The accuracy of thickness determination was confirmed by an experiment and it is better than 300 μm in the range of 2 to 10 mm, for the electrode arrangement optimized for the target thickness range. The applications of the proposed method are numerous, ranging from the industrial quality control, process monitoring, environmental sensing etc.

Multifunctional Configurable USB Data Acquisition System

In this paper we present a low cost implementation of the modular intelligent multi-channel data acquisition system as an alternative to existing commercial solutions. The system design enables simple reconfiguration and adaptation to various measuring requirements and it is particularly applicable for educational purposes, early-stage development and scientific research. Some of important requirements in modern electronic instrumentation design that our system satisfies are flexibility for different measuring scenarios, programmable input analog channels control and connectivity to standard communication interfaces available on todays personal computers. Simple system adaptation to application-specific purposes is achieved by a careful choice of electronic components, with particular emphasis on programmable central processing unit. The implemented system also provides high level of protection against surges and overvoltages in the input measuring channel by means of analog input transient suppression and galvanic isolation between the measuring circuitry and the personal computer interface. The basic measuring hardware configuration may be extended by external plug-in analog boards.

Measurement of dissolved hydrogen concentration with clark electrode

Clark electrode is a well-known sensor for measuring concentration of dissolved oxygen in a water solution. This type of electrochemical sensor has an advantage of enabling detection of very low oxygen concentration. Although Clark electrode is typically used for measurement of dissolved oxygen, our research showed that the same electrodes can be successfully applied for measurement of other dissolved gases. We investigated a possibility of applying the same principle to dissolved hydrogen concentration measurement, and also the possibility of simultaneous measurement of both dissolved oxygen and hydrogen concentrations in the same water solution. We adapted Clark electrode sensor to measure dissolved hydrogen by choosing the appropriate polarization voltage level. We studied the influences on dissolved hydrogen measurement, such as choice of polarization voltage, temperature, salinity, and solution pH. We investigated the polarization voltage influence on sensor sensitivity and observed hysteresis in sensitivity that occurs with cyclic increase and decrease of polarization voltage. We proposed and described measurement setup that was used for experimental verification of proposed measurement method and sensor characteristics. The measurement results of sensor characteristics are presented, regarding the influences of polarization voltage, temperature dependence, salinity (fresh water and 380/00 NaCl solution) and pH value (6, 7, 8).