Jos Knockaert

Compact Personal Distributed Wearable Exposimeter

A compact wearable personal distributed exposimeter (PDE) is proposed, sensing the power density of incident radio frequency (RF) fields on the body of a human. In contrast to current commercial exposimeters, our PDE, being composed of multiple compact personal wearable RF exposimeter sensor modules, minimizes uncertainties caused by the proximity of the body, the specific antenna used, and the exact position of the exposimeter. For unobtrusive deployment inside a jacket, each individual exposimeter sensor module is specifically implemented on the feedplane of a textile patch antenna. The new wearable sensor modules high-resolution logarithmic detector logs RF signal levels. Next, on-board flash memory records minimum, maximum, and average exposure data over a time span of more than two weeks, at a one-second sample period. Sample-level synchronization of each individual exposimeter sensor module enables combining of measurements collected by different nodes. The system is first calibrated in an anechoic chamber, and then compared with a commercially available single-unit exposimeter. Next, the PDE is validated in realistic conditions, by measuring the average RF power density on a human during a walk in an urban environment and comparing the results to spectrum analyzer measurements with a calibrated antenna.

Synchronous Wearable Wireless Body Sensor Network Composed of Autonomous Textile Nodes

A novel, fully-autonomous, wearable, wireless sensor network is presented, where each flexible textile node performs cooperative synchronous acquisition and distributed event detection. Computationally efficient situational-awareness algorithms are implemented on the low-power microcontroller present on each flexible node. The detected events are wirelessly transmitted to a base station, directly, as well as forwarded by other on-body nodes. For each node, a dual-polarized textile patch antenna serves as a platform for the flexible electronic circuitry. Therefore, the system is particularly suitable for comfortable and unobtrusive integration into garments. In the meantime, polarization diversity can be exploited to improve the reliability and energy-efficiency of the wireless transmission. Extensive experiments in realistic conditions have demonstrated that this new autonomous, body-centric, textile-antenna, wireless sensor network is able to correctly detect different operating conditions of a firefighter during an intervention. By relying on four network nodes integrated into the protective garment, this functionality is implemented locally, on the body, and in real time. In addition, the received sensor data are reliably transferred to a central access point at the command post, for more detailed and more comprehensive real-time visualization. This information provides coordinators and commanders with situational awareness of the entire rescue operation. A statistical analysis of measured on-body node-to-node, as well as off-body person-to-person channels is included, confirming the reliability of the communication system.

In situ testing of large machines: Alternative methods for conducted emission measurements

On the legal aspect, the new European Directive on ElectroMagnetic Compatibility 2004/108/EC concerns also large machines. On a technical point of view, the special situation to characterise the EMC behaviour of large machines imply that current procedures are complex and very expensive, and in some cases even not possible. Adapted measuring methodologies and procedures are needed. As a response to this situation and within the European R&D Frameworks, the TEMCA2 project aimed to develop new and adapted methodologies for the assessment of EMC related to this type of industrial large machinery.

Comparing MCSA with vibration analysis in order to detect bearing faults — A case study

Condition Monitoring on rotating electrical machines has proven to be economically beneficial in the last decades, especially for industrial production processes. Vibration analysis has already become a reliable and commercial tool to perform condition monitoring or predictive maintenance. Stator current analysis, a newer technology that is still being developed can possibly open new perspectives and opportunities in the world of predictive maintenance. This technology is also known as Motor Current Signature Analysis or MCSA. In this paper the advantages and disadvantages of both technologies are listed and compared from a practical point of view, supplemented with a case study. The case study contains a bearing fault detection in an induction machine driven by a frequency converter. The machine drives a fan with varying torque and speed conditions.

Using an industrial hardware target for Matlab generated real-time code to control a torsional drive system

Recent developments enable easier transfer of Matlab/Simulink based controller design into real-time code for standard industrial hardware targets. This paper evaluates this design method using state of the art industrial components - embedded controller, high speed remote I/O, Ethernet based industrial network - in a torsional drive system.

Single point outer race bearing fault severity estimation using stator current measurements

Although numerous valuable research has been conducted by many authors, the relation between evolving mechanical faults and their fault-indicating reflections in the electrical signals of rotating electric machinery still requires extensive attention. This lack of information implies serious obstructions in the evolution of applying motor current signature analysis as a complete and reliable condition monitoring technology. However, as previous research of the authors resulted in the construction of a unique test-bench where specific mechanical faults can be introduced into an 11kW induction machine with high reproducibility and accuracy, the relations between evolving mechanical faults and their reflections in the stator current can be investigated and quantified experimentally. Using this mechanical fault-emulator, experiments where conducted where the severity of a single point outer race bearing fault and its corresponding signature in the stator currents spectral fault-components are accurately analyzed. These evolving faulty components are trended and characterized, resulting in the desired quantification of the mechanical fault-severity. Based on these results, it is possible to inversely estimate the severity of single point outer race bearing problems by acquiring nothing more then the stator current time-functions.

A Vector Impedance Meter Method to Characterize Multiconductor Transmission-Line Parameters

For analyzing and simulating the behavior of multiconductor transmission lines, a measurement of the transmission-line parameters is needed. In this paper, an accurate method for measuring the full capacitance, inductance, resistance, and shunt-resistance matrices by a vector impedance meter is described. The method has been applied for frequencies in a range from 20 kHz up to 30 MHz.

Attenuation effect with non-linear loads for small stand-alone grids

This paper presents the effect of non-linear loads on the overall voltage quality in small powered stand-alone (islanded) systems. The iterative effect between current and voltage distortion is related to the sources impedance and this study illustrates the different harmonic behavior between power electronic (PE) inverters and electro-mechanical generators directly coupled to the load. A 2,5kW nominal power islanded system with non-linear loads is evaluated with both cases. The PE inverter is an off-the-shelf grid-interactive inverter designed for a combination of battery storage and solar power. The electro-mechanical generator is a synchronous machine with external speed and excitation control. Due to their inherently different behavior and output topology the attenuation effect is shown to be completely different with important complications for reliable operation of such systems.

Low-cost PROFIBUS DP Slave Shield for embedded controllers

The presented PROFIBUS DP Slave Shield creates a link between a PROFIBUS DP network and a microcontroller or embedded controller. The hardware can be used as an extension module for different embedded controllers with sufficiently fast IO. The system opens possibilities to connect virtual systems or Hardware-In-the-Loop systems running real-time MATLAB models to a PROFIBUS DP network running up to 12 Mbps. Measurement of signal timing and latency shows that the shield itself does not introduce significant latency.

Design of an Arduino based low-cost error generator for PROFIBUS DP

This paper briefly discusses the design of a low-cost, versatile and configurable error generator for PROFIBUS DP. Using a PROFICORE ULTRA oscilloscope trigger pulse, a small circuit designed around an Arduino MEGA 2560 disrupts messages on the industrial network, without adding an extra slave.