Emiliano Sisinni

Design and Implementation of a Wireless Fieldbus for Plastic Machineries

Fieldbus systems are well known in the industrial automation world. Due to the increasing demand for scalability and capability of working in harsh environment, the use of wireless communication is gaining in importance. In the past, some efforts were pursued to encapsulate wired standards over wireless link, but their diffusion is limited by reliability and predictability requirements. In addition, event-driven protocols borrowed from the consumer world (as IEEE802.11 or IEEE802.15.4) are not well suited for some industrial applications. In this paper, authors present the design and the experimental evaluation of a wireless real-time communication protocol that tries to overcome these limits. It exploits standard hardware to lower cost and implements a hybrid medium access strategy. Time Division Multiple Access scheduling is used to ensure time deadlines respect, while Carrier Sense Multiple Access with Collision Avoidance is used for acyclic communications, as those involved in network management. It has been successfully adopted for temperature monitoring in plastic machineries. The prototype network adopts star topology and can manage up to 16 nodes with a refresh time of 128 ms.

Automation of Distribution Grids With IEC 61850: A First Approach Using Broadband Power Line Communication

The IEC 61850 standard allows for a structured grid automation system where critical tasks like grid protections, renewable energy sources management, synchronized measurements, and monitoring applications share the communication network. So far, the use of IEC 61850 has been mainly limited to the primary substations, but more interesting could be the coordinated actions between primary and secondary substations in order to quickly react to faults and to reduce service downtimes for final customers. Unfortunately, the communication networks between primary and secondary substations are today only partially deployed. Considering this context, the broadband power line over medium voltage grid (MV-BPL) could be a suitable solution for closing the communication gaps between substations that use IEC 61850. The main objective of this paper is to present the outcomes of the first phase of a project whose final goal is the implementation in real grids of distribution grid automation based on IEC 61850. A new and comprehensive set of experiments on a real (and in service) medium voltage grid in Italy has been designed and carried out. The practicability of IEC 61850 communication over the distribution grid is assessed comparing the time characteristics of the MV-BPL against the transfer time classes of the IEC 61850, determining which IEC 61850 services may be transported over MV-BPL. The experimental long-term analysis highlights that more than 90% of the service requests are transferred on the network with a round-trip time lower than 40 ms even in the case of four hops, a time which is compatible with the IEC 61850 fast automatic interactions on MV grid.

Improving simulation of wireless networked control systems based on WirelessHART

Recently, WirelessHART (2007) and ISA100.11a (2009) have been proposed as communication standard for a wireless fieldbus. However, Wireless Networked Control Systems performances are hard to verify in the real world, since test beds are expensive and difficult to implement. This paper proposes the use of a co-simulation framework based on the interaction of TrueTime, together with a cross layer wireless network simulator based on OMNET++. In particular, OMNET++ models show accurate aspects of network and devices, for improving overall coexistence management. A sample system controlled by a WirelessHART network has been considered; the analysis of the control performance and coexistence immunity of WirelessHART with respect to the traditional IEEE802.15.4, has been done.

A New and Fast-Readout Interface for Resistive Chemical Sensors

The main issue concerning metal oxide (MOX) gas sensors is mostly related to the wide range of resistive values that the sensors can show. In addition, some sensors could have baseline resistive values up to tens of gigohms. To avoid the use of expensive picoammeters or the use of circuits adopting scaling factors, different solutions have recently been proposed, exploiting the resistance-to-time conversion (RTC) technique. They show good linearity and are suitable for the integration in a chip together with the elaboration unit, but they may require long measurement time (tens of seconds) if high resistance values need to be estimated. In addition, they may suffer the influence of a sensor parasitic capacitance, in parallel with the resistive component. In this paper, a new method is proposed to reduce the measuring time, keeping the advantages offered by the RTC approach and including a parasitic capacitance estimation feature. Particularly, an effective architecture, based on moving thresholds, has been proposed, simulated, and experimentally tested with commercial resistors (values between 1 M¿ and 100 G¿) and capacitors (values between 1 and 47 pF). Finally, a fast sensor transient, due to a rapid change in the heating power, has been acquired with the proposed instrument and compared with a similar transient analyzed with a classical RTC approach. This test has shown the applicability of the interface for solutions requiring detailed information of the sensor response, such as the characterization of new sensors (e.g., nanowires) or the behavior analysis during nonstandard thermal profiles.

A CCII-Based Low-Voltage Low-Power Read-Out Circuit for DC-Excited Resistive Gas Sensors

In this paper, we propose a low-voltage (LV) low-power (LP) oscillating circuit suitable for the read-out of DC-excited resistive gas sensors, based on Second Generation Current Conveyors (CCIIs). This low-cost fully integrable front-end is able to evaluate the resistive behavior of gas sensors, without any preliminary calibration, operating a Resistance to Time ( R-T) conversion and exciting the sensor with a DC voltage. Through the use of CCIIs, all the Current-Mode (CM) benefits in LV LP integrated architecture design are achieved. The developed interface, designed at transistor level, is able to operate with a low supply voltage (plusmn0.75 V), showing a low power consumption of about 700 muW, and, hence, it is suitable for portable applications. Both CADENCE simulations on the designed integrated solution and experimental results, achieved using a PCB prototype, have shown a linear characteristic and a good agreement with theoretical expectations, for more than four decades of resistive variation. Experimental measurements, conducted employing low cost commercial components (AD844 as CCII and Figaro TGS 2600 device as resistive gas sensor), have confirmed the good performances of the developed read-out circuit as resistive gas sensor interface.

On the Seamless Interconnection of IEEE1588-Based Devices Using a PROFINET IO Infrastructure

Several types of industrial Real-Time Ethernet (RTE) networks could be present in the same plant. This work deals with the clock synchronization problems that arise when different RTE network infrastructures are interconnected. Specifically, this paper is focused on the exploitation of PROFINET IO Conformance Class C infrastructure for the interconnection of other industrial communication devices or measurement instruments that use IEEE1588 for clock synchronization. Actually, such devices (e.g., LXI instruments, EtherNet/IP devices, etc.) cannot be satisfactorily synchronized if directly connected to the PROFINET infrastructure, because of the large time errors (up to 100 μs). The solution proposed in this paper is an intelligent clock synchronization converter that has fewer limitations if compared with other systems, like boundary clocks. The basic idea is the creation of a “black-box” (a sort of remote bridging device) for the interconnection of IEEE1588 nodes through a PROFINET IO host plant, with zero-configuration on both systems. The proposed approach differs from boundary clock since its goal is to keep the PROFINET IO and the IEEE1588 synchronization domains separated, exploiting the possibility to tunnel the IEEE1588 time information through the PROFINET IO infrastructure with sufficient precision. In order to verify the practical feasibility of the proposed solution, LXI Class B instruments have been connected to the infrastructure of a real PROFINET IO network. The results show that the standard deviation of the synchronization accuracy is only 10 ns higher than the one measured in the case of a dedicated (separated) network for the LXI instruments.

A Bluetooth-based sensor network with Web interface

In this work a Bluetooth-based sensor network is presented. Based on a Piconet, the proposed network supports web-server capabilities allowing the wireless sensors to be accessed by commercial browsers through the Internet. An experimental setup has been realized using three temperature sensors and related information has been viewed by PC clients. Measurements about power dissipation, maximum wireless communication distance and response time confirm the proposed network feasibility and effectiveness.

New Architecture for a Wireless Smart Sensor Based on a Software-Defined Radio

Today, wireless sensor technology is based on monolithic transceivers that optimize cost but have a rigid hardware architecture. In this paper, a new architecture for wireless sensors is presented. It is based on a software-defined radio concept and shows impressive adaptability to external conditions. The proposed architecture, which is called the wireless ultrasmart sensor (WUSS), enables the use of a software programmable transceiver, which can simultaneously manage multiple radio communication channels or standards. In addition, the WUSS architecture can mix the flexible communication part of the smart device with the sensor conditioning part. This combination represents a new generation of general-purpose sensors for microwave measurements in the gigahertz range (e.g., displacement and position sensing) with enhanced versatility since the same radio-frequency front end is both used to communicate and make measurements. Experimental results demonstrate the feasibility of the proposed architecture. A prototype shows the following abilities: managing multiple protocols using a single antenna, interfacing standard sensors, making delay and phase measurements with a standard deviation of 3 ns, and assigning the time of arrival to incoming radio signals with an error on the order of 20 ns.

Investigating WirelessHART coexistence issues through a specifically designed simulator

In this paper, the WirelessHART communication scheme is investigated. The protocol is at first described, in order to underline the key aspects of its design; then, a simulation tool is presented: it enables analysis that accounts for both protocol and physical layers issues. In particular, interference effects on protocol choices can be easily analyzed. The experimental results, obtained from simulations, highlight improvements of WirelessHART with respect to IEEE 802.15.4 standard, concerning the Packet Error Ratio (PER) degradation of interfering networks.

Timestamping of IEEE 802.15.4a CSS Signals for Wireless Ranging and Time Synchronization

Accurate positioning and distributed time synchronization for short-range personal area networks (PAN) are expected to boost the impact of mobile wireless systems in a variety of applications. At the moment, wireless ranging and time synchronization are often addressed independently. The two main underlying reasons are: 1) the different accuracy requirements for time-of-arrival measurements and local clock correction and 2) the intrinsic difficulty to timestamp the received radio frames with uncertainty lower than some nanoseconds due to the joint effect of clock resolution, wideband noise, clock frequency offsets, and multipath propagation. Of course, if the influence of such phenomena were minimized, time synchronization could benefit from accurate one-way ranging and vice versa. One of the most recent and promising communication schemes to reach this goal is chirp spread spectrum (CSS) modulation. Indeed, this is also one of the alternative physical (PHY) layers for PANs recommended in the amendment IEEE 802.15.4a-2007, recently included in the standard IEEE 802.15.4-2011. In this paper, the features of IEEE 802.15.4a CSS signals for low-level timestamping are analyzed both theoretically and through simulations under the effect of various uncertainty contributions. Accordingly, an effective solution for frame timestamping at the symbol level is proposed. Some experimental results based on a software defined radio implementation of the IEEE 802.15.4a PHY layer confirm that CSS can be successfully adopted both for time synchronization and ranging.