Federico Tramarin

Resolution Enhancement by Compressive Sensing in Power Quality and Phasor Measurement

Measurement in power systems and, particularly, in smart grids and smart microgrids is often concerned with harmonic analysis of voltage and current waveforms. The use of Fourier-based algorithms is widespread, and the limits following from the fundamental time-versus-frequency tradeoff that relates observation time to frequency resolution are well understood. This paper presents the application of an algorithm based on the principles of compressive sensing that can achieve an order-of-magnitude resolution improvement without significantly extending total observation time. For harmonic analysis in power systems, this means that accurate results can be obtained using shorter observation intervals, which allow to effectively track changes and reduce the effect of transients on measurements. The application of the algorithm to harmonics and interharmonics, as well as to phasor measurement, is considered and analyzed.

On the Use of IEEE 802.11n for Industrial Communications

In the last years, IEEE 802.11 Wireless LANs (WLANs) have proved their effectiveness for a wide range of real-time industrial communication applications. Nonetheless, the introduction of the important IEEE 802.11n amendment, which is commonly implemented in commercial devices, has not been adequately addressed in this operational framework yet. IEEE 802.11n encompasses several enhancements at both physical (PHY) and medium access control (MAC) layers that may bring considerable improvements to the performance of WLANs deployed in real-time industrial communication systems. To this regard, in this paper, we present a thorough investigation of the most important IEEE 802.11n features, addressing in particular, specific performance indicators such as timeliness and reliability, which are crucial for industrial communication systems. To this aim, after an accurate theoretical analysis, we implemented a suitable experimental setup and carried out several measurement sessions to obtain an exhaustive performance assessment. The outcomes of these experiments, on one hand, revealed that the adoption of IEEE 802.11n can actually provide significant improvements to the performance of the IEEE 802.11 WLAN in the industrial communication scenario. On the other hand, the assessment allowed to select, among the various options of IEEE 802.11n, the parameter settings which may ensure the best behavior in this specific (and demanding) field of application.

Energy Efficient Ethernet for Real-Time Industrial Networks

To increase the energy efficiency of Ethernet networks, in 2010, the IEEE published the IEEE 802.3az amendment, known as Energy Efficient Ethernet (EEE). The amendment introduces a new operational mode, defined as Low Power Idle (LPI), that allows to considerably reduce the power consumption of inactive Ethernet links. In this paper, we address the application of EEE to Real-Time Ethernet (RTE) networks, the popular communication systems typically employed in factory automation, characterized by tight timing requirements. We start with a description of the EEE basics and, subsequently, focus on the introduction of EEE in the industrial communication scenario. Then, we specifically address the implementation of effective EEE strategies for some popular RTE networks. The analysis is carried out on configurations commonly deployed at low levels of factory automation systems. The obtained results show that considerable power savings can be achieved with very limited impact on network performance.

Improved Rate Adaptation strategies for real-time industrial IEEE 802.11n WLANs

The IEEE 802.11 standard, since its earliest versions, provides the multi-rate support feature typically exploited by Rate Adaptation (RA) techniques to dynamically select the most suitable transmission rate, based on an estimation of the channel status. With the release of the IEEE 802.11n amendment, several enhancements have been introduced to the standard, notably the support for MIMO architectures, whose benefits can be effectively combined with multi-rate support. In an industrial communication scenario, the RA algorithms commonly available for general purpose applications revealed ineffective. This led to the definition of purposely designed algorithms, with the aim of improving the real-time behavior of IEEE 802.11 networks. In this paper we take into consideration these techniques, as well as some general purpose RA strategies, and analyze their implementation on an IEEE 802.11n communication system deployed in an industrial scenario. Furthermore, we propose an effective parameters tuning for the considered RA algorithms, as well as some enhancements conceived to enforce their timeliness. An exhaustive assessment, carried out via numerical simulations, shows that the improved techniques allow to achieve excellent performance.

A Dynamic Rate Selection Algorithm for IEEE 802.11 Industrial Wireless LAN

The multirate support feature has been introduced by the IEEE 802.11 standard to improve the system performance, and has been widely exploited by means of rate adaptation (RA) strategies within general purpose wireless LANs. These strategies revealed ineffective for real-time industrial communications, and alternative solutions, better tailored for such a specific field of application, were investigated. The preliminary outcomes of the analyses carried out were promising, even if they clearly indicated that further efforts were necessary. In this direction, this paper first proposes rate selection for industrial networks (RSIN), an innovative RA algorithm specifically conceived for the real-time industrial scenario with the goal of minimizing the transmission error probability, while taking into account the deadline imposed to packet delivery. Then, it describes the practical implementation of RSIN on commercial devices, along with that of other formerly introduced RA techniques. Finally, the paper presents a thorough performance analysis, carried out to investigate the behavior of the addressed RA schemes. Such an assessment was performed via both experimental campaigns and simulations. The obtained results, on one hand, confirm the effectiveness of the RA techniques purposely designed for real-time industrial communication. On the other hand, they clearly indicate that RSIN outperforms all the other strategies.

An Energy Efficient Ethernet Strategy Based on Traffic Prediction and Shaping

Recently, different communities in computer science, telecommunication, and control systems have devoted a huge effort towards the design of energy efficient solutions for data transmission and network management. This paper collocates along this research line and presents a novel energy efficient strategy conceived for Ethernet networks. The proposed strategy, which exploits the opportunities offered by the IEEE 802.3az amendment to the Ethernet standard (known as energy efficient Ethernet) is based on the possibility of predicting the future traffic from the analysis of the current data flow. In agreement with the results of such a dynamic prediction, Ethernet links can be forced into a low power consumption state for variable intervals. Theoretical bounds are derived to detail how the performance figures depend on the parameters of the designed strategy and scale with respect to traffic load. Furthermore, simulation results carried out with both real and synthetic traffic traces are presented to prove the effectiveness of the strategy, which leads to considerable energy savings at the cost of only a limited bounded delay in data delivery.

The IEEE 802.11n wireless LAN for real-time industrial communication

In the last years, IEEE 802.11 Wireless LANs (WLANs) have proved their effectiveness for a wide range of real-time industrial communication applications. Nonetheless, the enhancements at the PHY and MAC layers introduced by the IEEE 802.11n amendment have not yet been adequately addressed in the context of industrial communication. In this paper we investigate the impact of some IEEE 802.11n new features on some important performance figures for industrial applications, such as timeliness and reliability.

Strategies and Services for Energy Efficiency in Real-Time Ethernet Networks

The IEEE 802.3az amendment to the Ethernet standard, referred to as energy-efficient Ethernet (EEE), encompasses the new low power Idle operational mode that allows to strongly decrease the energy consumption of inactive links. The introduction of EEE in real-time industrial communications represents an interesting topic currently addressed by the scientific community, as well as by some standardization bodies. The outcomes of these activities are promising, since effective EEE strategies can be devised, and are able to cope with the very tight timing requirements of industrial communication. Unfortunately, the proposed analyses do not address implementation issues that, conversely, represent a crucial aspect in this scenario. Hence, in this paper, we specifically focus on practical issues concerned with the adoption of EEE strategies by real-time Ethernet (RTE) networks. At first, we address the use of commercially available network components and describe a measurement setup that can be adopted to achieve the adequate characterization of such components. Furthermore, we show that, in an RTE perspective, link activations/deactivations should be independently managed by suitably designed EEE strategies at the application level. Consequently, we defined a set of network services that have to be made available in the device drivers. Hence, we consider a generic RTE network and discuss methods for the practical implementation of those EEE strategies. A performance assessment carried out via theoretical models as well as numerical simulations shows that EEE strategies can be effectively implemented with considerable power savings at the expense of only minimal performance degradation.

Performance assessment of an IEEE 802.11-based protocol for real-time communication in agriculture

This paper investigates an original system for wireless control and monitoring of an agricultural machine. The system is implemented by means of an IEEE 802.11-based soft realtime communication architecture which enables the connection of the machine with off-the-shelf mobile devices, like widespread tablet PCs, that could hence replace traditional ad-hoc developed operator panels. The harsh surrounding environment, however, introduces severe requirements. Hence, focusing on the wireless communication behavior, the paper yields a thorough performance analysis derived by extensive experimental campaigns. By investigating the outcomes of these measurement sessions, the paper assesses some causes of performance degradation, and provides viable and easy to implement solutions to improve the overall system behavior.

System-level performance of an automation solution based on industry standards

The flexibility and reconfigurability requirements of factories and manufacturing plants of the future can be partially met by adopting technologies and solutions already available for testing and experimentation. Openness and adherence to international standards are becoming increasingly important in modern distributed production and automation systems, especially when they have to cope with ever-increasing product differentiations and short product lifecycles. However, the increased flexibility and openness should not come to detriment of the system real-time characteristics. This paper deals with a pilot mechatronic architecture for agile transport systems, which has been specifically developed to enable the study of the aforementioned aspects in the framework of the “Factory of the Future” Italian flagship project. In particular, the paper focuses on possible bottlenecks and pitfalls at the operating system and communication levels, and provides preliminary indications on how to address or mitigate them by means of solutions already available on the market.