Implementation and Deployment Evaluation of the DMAMAC Protocol for Wireless Sensor Actuator Networks

The increased application of wireless technologies including Wireless Sensor Actuator Networks (WSAN) in industry has given rise to a plethora of protocol designs. These designs target metrics ranging from energy efficiency to real-time constraints. Protocol design typically starts with a requirements specification, and continues with analytic and model-based simulation analysis. State-of- the-art network simulators provide extensive physical environment emulation, but still have limitations due to model abstractions. Deployment testing on actual hardware is therefore vital in order to validate implementability and usability in the real environment. The contribution of this article is a deployment testing of the Dual-Mode Adaptive MAC (DMAMAC) protocol. DMAMAC is an energy efficient protocol recently proposed for real-time process control applications and is based on Time Division Multiple Access (TDMA) in conjunction with dual-mode operation. A main challenge in implementing DMAMAC is the use of a dynamic superframe structure. We have successfully implemented the protocol on the Zolertia Z1 platform using TinyOS (2x). Our scenario- based evaluation shows minimal packet loss and smooth mode-switch operation, thus indicating a reliable implementation of the DMAMAC protocol.publishedVersio

Implementation and Deployment Evaluation of the DMAMAC Protocol for Wireless Sensor Actuator Networks

The increased application of wireless technologies including Wireless Sensor Actuator Networks (WSAN) in industry has given rise to a plethora of protocol designs. These designs target metrics ranging from energy efficiency to real-time constraints. Protocol design typically starts with a requirements specification, and continues with analytic and model-based simulation analysis. State-of- the-art network simulators provide extensive physical environment emulation, but still have limitations due to model abstractions. Deployment testing on actual hardware is therefore vital in order to validate implementability and usability in the real environment. The contribution of this article is a deployment testing of the Dual-Mode Adaptive MAC (DMAMAC) protocol. DMAMAC is an energy efficient protocol recently proposed for real-time process control applications and is based on Time Division Multiple Access (TDMA) in conjunction with dual-mode operation. A main challenge in implementing DMAMAC is the use of a dynamic superframe structure. We have successfully implemented the protocol on the Zolertia Z1 platform using TinyOS (2x). Our scenario- based evaluation shows minimal packet loss and smooth mode-switch operation, thus indicating a reliable implementation of the DMAMAC protocol.publishedVersio

Fault detection of a wind turbine generator bearing using interpretable machine learning

Introduction: During its operational lifetime, a wind turbine is subjected to a number of degradation mechanisms. If left unattended, the degradation of components will result in its suboptimal performance and eventual failure. Hence, to mitigate the risk of failures, it is imperative that the wind turbine be regularly monitored, inspected, and optimally maintained. Offshore wind turbines are normally inspected and maintained at fixed intervals (generally 6-month intervals) and the program (list of tasks) is prepared using experience or risk-reliability analysis, like Risk-based inspection (RBI) and Reliability-centered maintenance (RCM). This time-based maintenance program can be improved upon by incorporating results from condition monitoring involving data collection using sensors and fault detection using data analytics. In order to properly carry out condition assessment, it is important to assure quality & quantity of data and to use correct procedures for interpretation of data for fault detection. This paper discusses the work carried out to develop a machine learning based methodology for detecting faults in a wind turbine generator bearing. Explanation of the working of the machine learning model has also been discussed in detail.Methods: The methodology includes application of machine learning model using SCADA data for predicting operating temperature of a healthy bearing; and then comparing the predicted bearing temperature against the actual bearing temperature.Results: Consistent abnormal differences between predicted and actual temperatures may be attributed to the degradation and presence of a fault in the bearing.Discussion: This fault detection can then be used for rescheduling the maintenance tasks. The working of this methodology is discussed in detail using a case study

Stabssjefene og stabsorganiseringen i Reagan-administrasjonen

THE CHIEF OF STAFFS AND THE STAFF STRUCTURING IN THE REAGAN- ADMINISTRATION. In this paper I am going to put the focus on the chief of staffs and the different staffing models used in the Reagan-administration. During the Reagan presidency four different chief of staff served in the administration. In this paper the emphasis is going to be on the two first. James Baker and Donald Regan. I have found this limitation necessary partly because the whole length of the administration would be to extensive for the limitations this paper sets. Partly because Baker and Regan respectively where the two chief of staffs that served longest in the administration. And in their own way they were going to put their own mark on the administration. It is generally agreed that the American president roughly has three main different models for staff structure. The first is called a formalistic model or a hierarchic staff structure under a strong chief of staff. The second is called a competitive model and the last is called the collegial model. Under different chiefs of staffs the Reagan administration used all three models. The first period of the administration bears the characteristics of a collegial model. Three to four central participants in reality divided the traditional responsibilities of a chief of staff. No single individual or participant dominated operations in the white house. We can characterise that the power in this period to a certain extent ebbed and flowed between the central participants. At the beginning of the second period we can see an rather original movement in the administration. Finance minister Donald Regan, and chief of staff Baker meet in secret and decide to change jobs. The president is told almost in hindsight. The change in chief of staff were going to have fundamental impact on the administration. Where staff structure previously had been characterised of a more collective model the staff structure goes throe a major restructuring. The new chief goes on to centralise the staff structure under a more hierarchical chain of command. More and more levels of power is centralised in the hands of one man, the chief of staff. The purpose of this paper is then to try to present both a theoretical and the empirical framework to be able to come near the question what staff structure served the administration best. The principal way of doing this has been to present two different hypotheses, and identify some criteria's for measuring this question against

A Survey of 802.15.4 TSCH Schedulers for a Standardized Industrial Internet of Things

Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revolution. These concepts require extensive connectivity far beyond what is provided by traditional industrial networks. The Industrial Internet of Things (IIoT) bridges this gap by employing wireless connectivity and IP networking. In order for wireless networks to meet the strict requirements of the industrial domain, the Time Slotted Channel Hopping (TSCH) MAC is often employed. The properties of a TSCH network are defined by the schedule, which dictates transmission opportunities for all nodes. We survey the literature for these schedulers, describe and organize them according to their operation: Centralized, Collaborative, Autonomous, Hybrid, and Static. For each category and the field as a whole, we provide a holistic view and describe historical trends, highlight key developments, and identify trends, such as the attention towards autonomous mechanisms. Each of the 76 schedulers is analyzed into their common components to allow for comparison between schedulers and a deeper understanding of functionality and key properties. This reveals trends such as increasing complexity and the utilization of centralized principles in several collaborative schedulers. Further, each scheduler is evaluated qualitatively to identify its objectives. Altogether this allows us to point out challenges in existing work and identify areas for future research, including fault tolerance, scalability, non-convergecast traffic patterns, and hybrid scheduling strategies

A Survey of 802.15.4 TSCH Schedulers for a Standardized Industrial Internet of Things

Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revolution. These concepts require extensive connectivity far beyond what is provided by traditional industrial networks. The Industrial Internet of Things (IIoT) bridges this gap by employing wireless connectivity and IP networking. In order for wireless networks to meet the strict requirements of the industrial domain, the Time Slotted Channel Hopping (TSCH) MAC is often employed. The properties of a TSCH network are defined by the schedule, which dictates transmission opportunities for all nodes. We survey the literature for these schedulers, describe and organize them according to their operation: Centralized, Collaborative, Autonomous, Hybrid, and Static. For each category and the field as a whole, we provide a holistic view and describe historical trends, highlight key developments, and identify trends, such as the attention towards autonomous mechanisms. Each of the 76 schedulers is analyzed into their common components to allow for comparison between schedulers and a deeper understanding of functionality and key properties. This reveals trends such as increasing complexity and the utilization of centralized principles in several collaborative schedulers. Further, each scheduler is evaluated qualitatively to identify its objectives. Altogether this allows us to point out challenges in existing work and identify areas for future research, including fault tolerance, scalability, non-convergecast traffic patterns, and hybrid scheduling strategies

Field trials of two 802.11 residual bandwidth estimation methods

Ad hoc networks have attracted much attention due to their decentralized architecture and potential mobility. The latter promise has sparked research aimed towards routing and quality of service (QoS) admission schemes. The volatile links that are inherent to these networks have however spawned a need for a cross-layering service below IP for local route and QoS decision making, or information dissemination to participating hosts. We have conducted field trials of an active and a passive estimation method implemented in a real wireless driver to estimate the residual bandwidth. Through these tess we show how residual bandwidth estimates can be obtained in an 802.11 wireless network and identify the strenghts and weaknesses of their underlying methods. The implemented wireless driver collects per link bandwidth data, local retransmission count and expected transmission tim

A Survey of 802.15.4 TSCH Schedulers for a Standardized Industrial Internet of Things

Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revolution. These concepts require extensive connectivity far beyond what is provided by traditional industrial networks. The Industrial Internet of Things (IIoT) bridges this gap by employing wireless connectivity and IP networking. In order for wireless networks to meet the strict requirements of the industrial domain, the Time Slotted Channel Hopping (TSCH) MAC is often employed. The properties of a TSCH network are defined by the schedule, which dictates transmission opportunities for all nodes. We survey the literature for these schedulers, describe and organize them according to their operation: Centralized, Collaborative, Autonomous, Hybrid, and Static. For each category and the field as a whole, we provide a holistic view and describe historical trends, highlight key developments, and identify trends, such as the attention towards autonomous mechanisms. Each of the 76 schedulers is analyzed into their common components to allow for comparison between schedulers and a deeper understanding of functionality and key properties. This reveals trends such as increasing complexity and the utilization of centralized principles in several collaborative schedulers. Further, each scheduler is evaluated qualitatively to identify its objectives. Altogether this allows us to point out challenges in existing work and identify areas for future research, including fault tolerance, scalability, non-convergecast traffic patterns, and hybrid scheduling strategies

Field trials of two 802.11 residual bandwidth estimation methods

Ad hoc networks have attracted much attention due to their decentralized architecture and potential mobility. The latter promise has sparked research aimed towards routing and quality of service (QoS) admission schemes. The volatile links that are inherent to these networks have however spawned a need for a cross-layering service below IP for local route and QoS decision making, or information dissemination to participating hosts. We have conducted field trials of an active and a passive estimation method implemented in a real wireless driver to estimate the residual bandwidth. Through these tess we show how residual bandwidth estimates can be obtained in an 802.11 wireless network and identify the strenghts and weaknesses of their underlying methods. The implemented wireless driver collects per link bandwidth data, local retransmission count and expected transmission tim