Multiple frequency response points identification through single asymmetric relay feedback experiment

In this paper a methodology to identify several points of the frequency response of a system using a single experiment is proposed. The identification is performed using the information obtained from an asymmetric relay feedback experiment. The frequency response points that are estimated correspond to the fundamental oscillation frequency induced by the asymmetric relay and its harmonics. The method is easy to implement since it only requires linear algebra operations, but relies on a proper data selection, which is largely studied, to obtain the most accurate results. The proposed method allows a Least Squares formulation, which has also been studied, and presents some benefits in terms of accuracy for certain cases. The presented results are validated experimentally using a practical identification case.This work was supported by Universitat Jaume I, Spain with grant number 18I411-Uji-b2018-39, MINECO, Spain with grant numbers DPI2017-84259-C2-2-R, RTI2018-094665-B-I00 and Ministerio de Ciencia e Innovación, Spain with grant number TEC2015-69155-R and by the State Research Agency, Spain under project PID2020-112658RBI00/10.13039/501100011033. The material in this paper was not presented at any conference. This paper was recommended for publication in revised form by Associate Editor Cristian R. Rojas under the direction of Editor Alessandro Chiuso

An estimation approach for process control based on asymmetric oscillations

[Abstract] An estimation procedure for process control has been developed based on the information obtained from the oscillations that a non-linear element as a simple relay introduces in the feedback loop. Features of the method are: (1) the procedure does not demand a priori process information, (b) non-iterative algorithms are needed to derive the process parameters, (c) only one test is needed, and (d) it allows identifying the process at a user-specified phase lag in the third quadrant. The method is presented for estimation of most common transfer functions found in chemical and process industry: integrators, first-, second- as well as processes with non-minimum-phase dynamics.Ministerio de Economía y Competitividad; PI2012-31303Ministerio de Economía y Competitividad; DPI2014-55932-C2-2-

Survey and Systematization of Secure Device Pairing

Secure Device Pairing (SDP) schemes have been developed to facilitate secure communications among smart devices, both personal mobile devices and Internet of Things (IoT) devices. Comparison and assessment of SDP schemes is troublesome, because each scheme makes different assumptions about out-of-band channels and adversary models, and are driven by their particular use-cases. A conceptual model that facilitates meaningful comparison among SDP schemes is missing. We provide such a model. In this article, we survey and analyze a wide range of SDP schemes that are described in the literature, including a number that have been adopted as standards. A system model and consistent terminology for SDP schemes are built on the foundation of this survey, which are then used to classify existing SDP schemes into a taxonomy that, for the first time, enables their meaningful comparison and analysis.The existing SDP schemes are analyzed using this model, revealing common systemic security weaknesses among the surveyed SDP schemes that should become priority areas for future SDP research, such as improving the integration of privacy requirements into the design of SDP schemes. Our results allow SDP scheme designers to create schemes that are more easily comparable with one another, and to assist the prevention of persisting the weaknesses common to the current generation of SDP schemes.Comment: 34 pages, 5 figures, 3 tables, accepted at IEEE Communications Surveys & Tutorials 2017 (Volume: PP, Issue: 99

Scenarios for the development of smart grids in the UK: literature review

Smart grids are expected to play a central role in any transition to a low-carbon energy future, and much research is currently underway on practically every area of smart grids. However, it is evident that even basic aspects such as theoretical and operational definitions, are yet to be agreed upon and be clearly defined. Some aspects (efficient management of supply, including intermittent supply, two-way communication between the producer and user of electricity, use of IT technology to respond to and manage demand, and ensuring safe and secure electricity distribution) are more commonly accepted than others (such as smart meters) in defining what comprises a smart grid. It is clear that smart grid developments enjoy political and financial support both at UK and EU levels, and from the majority of related industries. The reasons for this vary and include the hope that smart grids will facilitate the achievement of carbon reduction targets, create new employment opportunities, and reduce costs relevant to energy generation (fewer power stations) and distribution (fewer losses and better stability). However, smart grid development depends on additional factors, beyond the energy industry. These relate to issues of public acceptability of relevant technologies and associated risks (e.g. data safety, privacy, cyber security), pricing, competition, and regulation; implying the involvement of a wide range of players such as the industry, regulators and consumers. The above constitute a complex set of variables and actors, and interactions between them. In order to best explore ways of possible deployment of smart grids, the use of scenarios is most adequate, as they can incorporate several parameters and variables into a coherent storyline. Scenarios have been previously used in the context of smart grids, but have traditionally focused on factors such as economic growth or policy evolution. Important additional socio-technical aspects of smart grids emerge from the literature review in this report and therefore need to be incorporated in our scenarios. These can be grouped into four (interlinked) main categories: supply side aspects, demand side aspects, policy and regulation, and technical aspects.

International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

An automatic tuner with short experiment and probabilistic plant parameterization

A novel automatic tuning strategy is proposed. It is based on an experiment of very short duration, followed by simultaneous identification of LTI model parameters and an estimate of their error covariance. The parametric uncertainty model is subsequently exploited to design linear controllers with magnitude bounds on some closed-loop transfer function of interest, such as the sensitivity function. The method is demonstrated through industrially relevant examples. Robustness is enforced through probabilistic constraints on the H∞ norms of the sensitivity function, while minimizing load disturbance integral error (IE) to ensure performance. To demonstrate the strength of the proposed method, identification for the mentioned examples is carried out under a high level of measurement noise

PID control of an electro-mechanical friction clutch system

The main contribution of control technology in automotive powertrain system is that, it enables the whole powertrain system to be precisely controlled; thereby, improving the overall vehicle powertrain performance and sustainability. This paper describes a proportional-integral-derivative (PID) controller development for an electro-mechanical friction clutch (EMFC) system for automotive applications especially, those using continuously variable transmission (CVT). Initially, a simulation study was carried out to determine the PID preliminary parameters values derived using the Astrom and Hagglund tuning method with Ziegler-Nichols formula; then, they are manually being fine- tuned experimentally to improve the clutch engagement and disengagement control performance until satisfying engagement and disengagement process are achieved. The results of this work show that the application of Astrom-Hagglund method and Ziegler-Nichols formula is capable of providing a practical solution for obtaining initial parameters of the PD controllers of engagement and disengagement control of the EMFC system. Through optimizing of P and D parameters, the system indicated excellent performances with improvement in terms of percentage overshoot, settling time and a very small steady state error for clutch engagement and disengagement processes

A transistorized relay servo

Bidirectional control of a DC motor is achieved with standard power transistors and a simple transistorized pre-amplifier. A permanent magnet, DC motor is used as a test vehicle to illustrate the feasibility of control without an amplidyne or mechanical relay. The "bang-bang" capability of the controller to operate as a near-ideal "relay" is emphasized. The inherent flexibility allowed in selecting the switching characteristics is also demonstrated. The discussion points toward practical application and stresses the analysis of the switching characteristics and system performance. The feasibility of using this controller to operate any other type of standard DC motor is also studied.http://www.archive.org/details/transistorizedre00johnLieutenant, United States NavyLieutenant, United States NavyApproved for public release; distribution is unlimited