Showing papers by "Stefano Rinaldi published in 2014"

A Servo-Clock Model for Chains of Transparent Clocks Affected by Synchronization Period Jitter

Abstract: Industrial networks for distributed monitoring, control, and automation purposes require high-accuracy clock synchronization in topologies including long chains of cascaded nodes. Unfortunately, accuracy typically degrades as the number of devices and the distance from the synchronization reference node (i.e., the master or grandmaster) grows, because of the accumulation of multiple uncertainty contributions. To mitigate this problem, the so-called transparent clocks are used in some synchronization protocols, such as the precision transparent clock protocol used in PROFINET IO isochronous real time networks and the precision time protocol version 2, standardized as IEEE 1588-2008. In this paper, an optimal servo-clock in the mean square sense is proposed. The controller relies on both a Kalman filter that estimates the clock state difference with respect to the master and a static-state feedback assuring mean square stability even under the effect of significant fluctuations of the synchronization period. Several multiparametric simulation results in a case study based on the features of PROFINET IO devices confirm that excellent performance can be achieved with the proposed approach.

Synchronization requirements of a Power Quality measurement system for the distribution grid

Abstract: Power Quality (PQ) measurement is becoming more and more important at distribution level due to the increasing presence of renewable energy sources with an intermittent generation. Some regulatory frameworks in Europe - as the Italian regulation - are starting to address this issue, and the installation of PQ meters is becoming mandatory in HV/MV substations. The measurements data provided by the PQ meters placed in HV/MV grid can be correlated to identify the source of the disturbances only if the measurements instruments are time synchronized. The Italian regulation requires the PQ meters have to be synchronized using a GPS receiver, with a time synchronization uncertainty below 20 ms. The paper investigates the synchronization requirements of a power quality measurement system in order to propose a cost-effective network based time reference instead of costly GPS solutions. Some real examples from a field test area in Italy are used as input for parameters definition.

Multipath redundancy for industrial networks using IEEE 802.1aq Shortest Path Bridging

Abstract: The paper deals with redundancy networks for industrial automation systems, which are becoming more and more similar to network from other communication domains such as computing, office and telecommunications. The paper is focused on the use of emerging IEEE 802.1aq Shortest Path Bridging (SPB). A concurrent multipath communication across the same SPB mesh network, eliminating the waste of resources of other redundancy protocols (e.g. the Rapid Spanning Tree Protocol) has been proposed and analyzed. Novel performance indicator are proposed to compare the SPB solution with already existing redundancy protocols. Finally, both generic examples and industrial specific examples are given, highlighting the advantages of SPB with respect to other industrial solutions, especially when upgrading traditional networks with ring topology.

Timestamp Validation Strategy for Wireless Sensor Networks Based on IEEE 802.15.4 CSS

Abstract: Network time distribution relies on timestamping, which is employed by local nodes to assign a time value to incoming timing packets. Clearly, any error affecting the timestamp has a direct impact on the final synchronization accuracy of the system. In wireless sensor networks (WSNs), impairments affecting the wireless physical layer are the primary cause of such timestamping errors, and it would be advantageous to flag suspect timestamp values before feeding them into a synchronization algorithm. This paper discusses a new strategy for validating timestamps in a WSN based on IEEE 802.15.4 chirp spread spectrum. The considered system employs physical-level timestamping, which generates one timestamp for each symbol belonging to a packet. Such set of timestamps is processed using a Kalman filter (KF) that compares them with predicted values, employing statistical thresholds referred to the KF innovation process. Experimental results obtained over a long observation period shows that even in a noisy environment with several interfering communication sources, the algorithm is able to detect untrusted timestamps.

Acquisition and elaboration of cardiac signal in android Smartphone devices

Abstract: Today, the broad proliferation of Smartphones and Tablets has determined a wide availability of software applications for numerous purposes Thanks to this, Smartphones are now essential devices for many aspects of everyday life and not just advanced mobile phone terminals The presence of powerful processing units, embedded sensors as well as the availability of many standard communication interfaces has recently attracted the interest of the scientific community Several projects based on Smartphone systems have been proposed in different fields and many more application scenarios are being explored A critical aspect still unresolved is the possibility of acquiring external information, such as data from other sensors Due to their nature of consumer devices, Smartphones provide digital and high level communication interfaces, such as USB and Bluetooth Sensor interface is therefore possible if a suitable front-end able to digitize sensor data and to handle the communication with the Smartphone is employed In order to lower the complexity and the cost of the front-end as well as to reduce its power consumption, an effective method for the acquisition of external sensor signals through the Smartphone audio input is proposed in this paper As a proof of concept, a sensor system composed by a photoplethysmographic sensor for cardiac signal monitoring and a pair of electrodes for tissue impedance estimation has been used Specific software routines for Android operating system have been developed to process the acquired sensor signals providing visualization, data storage and simple data analysis, and thus demonstrating the feasibility of the proposed approach

Integration of Bluetooth HandsFree Sensors into a Wireless Body Area Network Based on Smartphone

Abstract: Generally speaking, invasive methods (such as chest belts) are used to collect data on people physical conditions, limiting the real-time monitoring, useful for example during sport trainings. To overcome the limitations of existent solutions, the external biometric sensors can be placed in a Bluetooth headset and the stream of biometric data transmitted to the smartphone when there is no call. In order to interface the sensors to iOS as well as Android based devices, Bluetooth HandsFree profile, the only widely supported, has been used to transmit the stream of data. The bandwidth available for the data stream is between 20 Hz and 4 kHz, but a Signal to Noise Ratio on the order of 30 dB can be obtained only in the bandwidth between 100 Hz and 1 kHz, as experimentally evaluated. Typically, the biometric sensors have a bandwidth below the 100 Hz, thus they requires a careful signal conditioning. A prototype, using a Photoplethysmographic sensor, has been developed to demonstrate the feasibility of this approach. The stream of real-time data obtained from the sensor are collected and then visualized to the final user, using dedicated applications, for iOs as well as for Android.

Improving availability of distributed PMU in electrical substations using wireless redundant process bus

Abstract: Protection and measurement systems in electrical substations are requested to have high availability. When considering an all-digital substation protection system, all the components and infrastructure devices (instrument transformers, processing units, merging units, intelligent electronic devices, communication network and synchronization source) contribute to the overall availability level. In particular, in this paper the availability of a distributed phasor measurement unit inspired by the standards IEC 61850, is investigated. A cost-effective solution to enhance distributed PMU reliability by means of redundancy using an IEEE 802.11 wireless network is proposed. The process bus has a wireless backup for both time synchronization protocol and sampled values packets carrying measurement information. Results are reported for a wireless network that uses software based timestamping for PTP synchronization.

Low-power wireless interface for handheld smart metering devices

Abstract: Advantages of smart metering are well known: more control of resource usage, accurate bills and better budgeting. For this reason roll out plans have been created not only for electricity, but also for gas distribution. In such a scenario, some additional difficulties arise due to the need of a wireless and autonomous functioning of meters. In particular, measurement techniques and communication protocols must take into account limited power source availability. In this work the need of a low power handheld device for maintenance (and monitoring) in the context of gas smart metering is addressed. The proposed architecture exploits smart devices (e.g. smartphones or tablets) as user-friendly terminals. Low power consumption is ensured using inductive coupling for data transmissions. A proof-of-concept prototype has been realized confirming the effectiveness of the proposed solution. In particular the consumption of the interface does not affect the overall system lifetime.

Improving syntonization of synchronous ethernet nodes using multiple paths

Abstract: The joint use of clock synchronization and syntonization can provide extremely high accuracy in industrial and telecom applications. However, in typical implementations of Synchronous Ethernet , only one frequency source at a time is selected for node syntonization (even in the presence of redundant networks with multiple paths), thus losing useful information. In this paper, an algorithm able to synthesize a frequency reference from the fusion of multiple signals over different network paths is presented and validated through simulations. The results confirm that the proposed algorithm is able to improve both frequency stability and robustness of the generated reference signal.

Wireless Sensor Network Based on wM-Bus for Leakage Detection in Gas and Water Pipes

Abstract: In the last years, energy saving is one of the dominant themes of public opinion, and thus the technological research is focused on this topic. The only adoption of new and more efficient technologies does not solve problem of the losses introduced by the carriage gas or water. In all countries, the losses of water in waterworks and in the urban carriage networks are great, but this problem is particularly acute in Italy, where, for example, the water losses overtake 30 % of the total amount of the water flowing in pipes. In the following, a solution based on WSN for the monitoring of the leakages, mainly in gas pipe, using the wM-Bus communication technology, has been proposed.

Inexpensive time dissemination using magnetically coupled resonators

Abstract: Synchronization is an important feature in wireless sensor networks, often needed to enable correct operation. In this paper, the usage of magnetic field coupling is explored, to provide Time of Flight information, useful to develop a timestamp based clock distribution system. In particular, the proposed approach can be easily implemented using very low-cost hardware, despite the good performance that can be obtained. Experimental results show very good short-term stability; standard deviation of consecutive signal burst inter-arrival time is in the sub-nanosecond region. The results have been compared with a similar commercial solution using low frequency wakeup receiver; in this case, standard deviation of signal bursts inter-arrival times is on the order of few microseconds.

Characterization of Multi-sensor System for Noninvasive Measurement of Vital Parameters

Abstract: A simple, portable, and low-cost system for noninvasive measurement of vital parameters, based on two sensors conveniently combined in a unique compact-in-size and low-power structure, has been presented and characterized in this work. The proposed solution allows both sensors to fit in a small structure, in order to be applied on the earlobe (or analogue body part of a person) in a clip-like fashion, making it suitable for portable and battery-operated systems. The two involved sensors are as follows: a photoplethysmographic (PPG) sensor, used to optically measure the change in volume of blood in the arteries, thus to acquire information about heart beating, and a sensor composed by two electrodes, used to perform an impedance measurement, thus to monitor the dielectric properties of biological tissues and fluids, like blood flow.