Ruan Delgado Gomes

Embedded System Integrated Into a Wireless Sensor Network for Online Dynamic Torque and Efficiency Monitoring in Induction Motors

The system proposed in this paper aims at monitoring the torque and efficiency in induction motors in real time by employing wireless sensor networks (WSNs). An embedded system is employed for acquiring electrical signals from the motor in a noninvasive manner, and then performing local processing for torque and efficiency estimation. The values calculated by the embedded system are transmitted to a monitoring unit through an IEEE 802.15.4-based WSN. At the base unit, various motors can be monitored in real time. An experimental study was conducted for observing the relationship between the WSN performance and the spectral occupancy at the operating environment. This study demonstrated that the use of intelligent nodes, with local processing capability, is essential for this type of application. The embedded system was deployed on a workbench, and studies were conducted to analyze torque and system efficiency.

Correlation between Spectral Occupancy and Packet Error Rate in IEEE 802.15.4-based Industrial Wireless Sensor Networks

This paper aims at evaluating the communication performance of the IEEE 802.15.4 standard in an industrial environment. We investigated the correlation between Packet Error Rate (PER) and Spectral Occupancy (SO) in the network environment. For this goal, we studied the impact on SO and PER resulting from the insertion of interference from other sources within the same range of the channels defined by the standard. The results show that an IEEE 802.15.4-based sensor network can suffer large drop in performance with the addition of new sources of interference. The information provided by the experiments can be used to guide the development of new spectrum-aware techniques and protocols to mitigate the interference in IEEE 802.15.4-based industrial wireless sensor networks.

On the Impact of Local Processing for Motor Monitoring Systems in Industrial Environments Using Wireless Sensor Networks

This paper presents a theoretical study for verifying the impact of using smart nodes in motor monitoring systems in industrial environments employing Wireless Sensor Networks (WSNs). Structured cabling and sensor deployment are usually more expensive than the cost of the sensors themselves. Besides the high cost, the wired approach offers little flexibility, making the network deployment and maintenance a complex process. In this context, wireless networks present a number of advantages compared to wired networks as, for example, the ease and speed of deployment and maintenance and the associated low cost. However, WSNs have several limitations, such as the low bandwidth and unreliability, especially in harsh environments (e.g., industrial plants). This paper presents a theoretical study on the performance of WSNs for motor monitoring applications in industrial environments, taking into account WSNs’ characteristics (i.e., unreliability and communication and processing latency). The results obtained through mathematical models were analyzed together with experimental results, and it was demonstrated that employing intelligent nodes with local processing capabilities is essential for the applications under consideration, because it reduces the amount of data transmitted over the network allowing monitoring even in scenarios with high interference rate, paying off the extra latency resulting from local processing.

Real-time link quality estimation for industrial wireless sensor networks using dedicated nodes

Adaptive mechanisms, such as dynamic channel allocation or adaptive routing, are used to deal with the variations in the link quality of Wireless Sensor Networks (WSN). In both cases, the first step is to estimate the link quality, so that the network nodes can decide if a channel or route change is needed. This paper proposes a Link Quality Estimator (LQE) for Industrial WSN, and a new type of node, the LQE node, that estimates the link quality in real-time, using the Received Signal Strength Indication (RSSI), and information obtained from received data packets. The proposed LQE is capable of capturing the effects of multipath, interference, and link asymmetry. Experiments were performed in a real industrial environment using IEEE 802.15.4 radios, and models were developed to allow the use of RSSI samples to proper estimate the link quality. A comparison was performed with a state-of-the-art LQE, the Opt-FLQE, and the results showed that the proposed estimator is more accurate and reactive for the type of environment in study. Different from other LQEs in literature, in the proposed LQE the sensor nodes do not need to send broadcast probe packets. Besides, using the LQE node, the other nodes of the WSN do not need to stop their operation to monitor the link quality.

Survey and systematic mapping of industrial Wireless Sensor Networks

Abstract The Wireless Sensor Network (WSN) is an infrastructure comprised of sensing, computing, and communication devices, that obtain and process data to help understand the behavior of the monitored environment, and to react to events and phenomena that occur in it. The WSN can be used in domains such as agriculture, energy, industrial automation, medical health care, smart building, and so on. In industry, the characteristics of the wireless channel are different in comparison to other WSN environments, such as home and office environments. The use of WSN in industry is subject to typical problems of wireless communications, such as noise, shadowing, multipath fading and interference. In addition, the wireless channel in many industrial environments is non-stationary for a long term, which can cause abrupt changes in the characteristics of the channel over time. A set of standards was developed for industrial WSN, to overcome these limitations, such as WirelessHART, ISA100.11a, WIA-PA, and IEEE 802.15.4e. All the mentioned standards are based on the IEEE 802.15.4 physical layer, but define different mechanisms for the upper layers. However, according to recent publications, problems still can arise in the deployment of networks that follow the standards, because of multipath effects, and interference. This survey provides a structured overview of the standards used to implement industrial WSN, their advantages and drawbacks, and discusses the characteristics of the wireless channel in industrial environments. Finally, a systematic mapping is described, that presents results of publications about industrial WSN, and highlights important topics to be studied in this field.

Distributed approach for channel quality estimation using dedicated nodes in industrial WSN

A way to deal with the variations in the link quality of Wireless Sensor Networks (WSN) is the use of strategies for Dynamic Channel Allocation (DCA). The first step to perform DCA is estimating the channel quality, so that the network nodes can decide if a channel change is needed, and the best channel to be used. This paper proposes a distributed approach with nodes dedicated to monitor channel quality, by using the Received Signal Strength Indication (RSSI) and the Link Quality Indicator (LQI) to identify low quality channels. This approach is acceptable in industrial WSN, since the network deployment can be performed with adequate planning. Furthermore, the sensor nodes do not need to stop their operation for monitoring the channel quality. As a first step, experiments were performed in a real industrial environment to identify the relation between RSSI and LQI traces, and the Packet Error Rate for different channels, by using IEEE 802.15.4 radios operating in the 2.4 GHz band.

Comparison between Channel Hopping and Channel Adaptation for Industrial Wireless Sensor Networks.

One of the differences between the new standard IEEE 802.15.4e, in comparison to the previous IEEE 802.15.4 standard, is the use of multiple channels. The Time-Slotted Channel Hopping (TSCH) mode employs channel hopping, and the Deterministic and Synchronous Multi-channel Extension (DSME) mode employs channel hopping or channel adaptation, during the contention free periods. When using the channel adaptation as the channel diversity technique, a pair of nodes communicate using the same channel while the channel quality is good enough in terms of signal-to-noise ratio. Thus, it is necessary to evaluate the quality of the links, in order to proper use this mechanism. In this paper, three different approaches, based on the DSME protocol, were implemented and evaluated through a simulation study. The first one (CH-DSME) is based on a simple channel hopping mechanism, the second one (CA-DSME) employs channel adaptation, and the third one is a novel hybrid approach (H-DSME), that uses both channel hopping and channel adaptation. The H-DSME outperformed the other two approaches for the scenario in consideration, which shows that the use of channel adaptation is better than channel hopping for the transmission of unicast packets, when the quality of the links are monitored continuously. However, for packets transmitted in broadcast by the coordinator, the use of channel hopping is a good alternative to deal with the spatial variation in the quality of the channels.

Assessing maintainability metrics in software architectures using COSMIC and UML

The software systems have been exposed to constant changes in a short period of time. The evolution of these systems demands a trade-off among several attributes to keep the software quality acceptable. It requires high maintainable systems and makes maintainability one of the most important quality attributes. This paper approaches the system evolution through the analysis of potential new architectures using the evaluation of maintainability level. The goal is to relate maintainability metrics applied in the source-code of OO systems, in particular CCC, to notations defined by COSMIC methods and proposes metrics-based models to assess CCC in software architectures.

Performance Evaluation of Default Active Message Layer (AM) and TKN15.4 Protocol Stack in TinyOS 2.1.2.

Wireless Sensor Networks (WSN) have become a leading solution to monitor and control smart buildings, health, industrial environments, and so on. Sensor nodes in a WSN have resource constraints, presenting low processing power and, in some cases, restrictions in power consumption. The resource constraints forced the researchers to develop Operating Systems (OS) for low-power wireless devices, and one of the most important and in active use is the TinyOS. This paper presents an experimental study to evaluate the performance of TinyOS default Active Message (AM) layer protocol in comparison to the fully 802.15.4 compliant protocol stack TKN15.4 developed for TinyOS. The AS-XM1000 802.15.4 mote modules were used to compare both protocols. The results showed that TKN15.4 protocol is better in both energy consumption and packet

Application of Wireless Sensor Networks Technology for Induction Motor Monitoring in Industrial Environments

In an industrial environment, mechanical systems driven by electric motors are used in most production processes, accounting for more than two thirds of industry electricity consumption. Regarding the type of motors usually employed, about 90% are three-phase AC induction based [1], mainly due to its cost effectiveness and mechanical robustness [2].