Self-Triggered and Event-Triggered Set-Valued Observers

This paper addresses the problem of reducing the required network load and computational power for the implementation of Set-Valued Observers (SVOs) in Networked Control System (NCS). Event- and self-triggered strategies for NCS, modeled as discrete-time Linear Parameter-Varying (LPV) systems, are studied by showing how the triggering condition can be selected. The methodology provided can be applied to determine when it is required to perform a full (``classical'') computation of the SVOs, while providing low-complexity state overbounds for the remaining time, at the expenses of temporarily reducing the estimation accuracy. As part of the procedure, an algorithm is provided to compute a suitable centrally symmetric polytope that allows to find hyper-parallelepiped and ellipsoidal overbounds to the exact set-valued state estimates calculated by the SVOs. By construction, the proposed triggering techniques do not influence the convergence of the SVOs, as at some subsequent time instants, set-valued estimates are computed using the \emph{conventional} SVOs. Results are provided for the triggering frequency of the self-triggered strategy and two interesting cases: distributed systems when the dynamics of all nodes are equal up to a reordering of the matrix; and when the probability distribution of the parameters influencing the dynamics is known. The performance of the proposed algorithm is demonstrated in simulation by using a time-sensitive example

Distributed Fault Detection Using Relative Information in Linear Multi-Agent Networks

This paper addresses the problem of fault detection in the context of a collection of agents performing a shared task and exchanging relative information over a communication network. We resort to techniques in the literature to construct a meaningful observable system and overcome the issue that the system of systems is not observable. A solution involving Set-Valued Observers (SVOs) is proposed to estimate the state in a distributed fashion and a proof of convergence of the estimates is given under mild assumptions. The performance of the proposed algorithm is assessed through simulations

Fault detection for LPV systems using Set-Valued Observers: A coprime factorization approach

This paper addresses the problem of fault detection for linear parameter-varying systems in the presence of measurement noise and exogenous disturbances. The applicability of current methods is limited in the sense that, to increase accuracy, the detection requires a large number of past measurements and the boundedness of the set-valued estimates is only guaranteed for stable systems. In order to widen the class of systems to be modeled and also to reduce the associated computational cost, the aforementioned issues must be addressed. A solution involving left-coprime factorization and deadbeat observers is proposed in order to reduce the required number of past measurements without compromising accuracy and allowing the design of Set-Valued Observers (SVOs) for fault detection of unstable systems by using the resulting stable subsystems of the coprime factorization. The algorithm is shown to produce bounded set-valued estimates and an example is provided. Performance is assessed through simulations, illustrating, in particular that small-magnitude faults (compared to exogenous disturbances) can be detected under mild assumptions

Finite-time average consensus in a Byzantine environment using Set-Valued Observers

This paper addresses the problem of consensus in the presence of Byzantine faults, modeled by an attacker injecting a perturbation in the state of the nodes of a network. It is firstly shown that Set-Valued Observers (SVOs) attain finite-time consensus, even in the case where the state estimates are not shared between nodes, at the expenses of requiring large horizons, thus rendering the computation problem intractable in the general case. A novel algorithm is therefore proposed that achieves finite-time consensus, even if the aforementioned requirement is dropped, by intersecting the set-valued state estimates of neighboring nodes, making it suitable for practical applications and enabling nodes to determine a stopping time. This is in contrast with the standard iterative solutions found in the literature, for which the algorithms typically converge asymptotically and without any guarantees regarding the maximum error of the final consensus value, under faulty environments. The algorithm suggested is evaluated in simulation, illustrating, in particular, the finite-time consensus property

Groundwater management in land administration: a spatio-temporal perspective

Although the use of land and water is intertwined, specifics for groundwater management are not effectively dealt with in the laws and other institutional mechanisms related to land. Provisions for groundwater aspects in land management are there, but with a focus on the land itself. Land rights and restrictions are more or less static, lacking enough flexibility to incorporate the relatively short interval spatio-temporal dynamics of groundwater resources in the land management and regulation mechanisms. This leads to a gap between the scientific inputs and policy-decision making. The paper suggests the adaptation of a spatial information science based approach to bridge the gap between the technical and administrative aspects of groundwater management. The land administration domain model (LADM) provides a basic set of elements capable of supporting the inclusion of basic groundwater modeling elements into land administration, making it possible to create a support system for the management of land and water. For this purpose, spatial and temporal dimensions under the legal-administrative and spatial unit components of the standard LADM model are reviewed. The paper shows that the advancement of spatial technologies is capable of providing solutions for global issues such as groundwater resource management. As a first step towards implementation of these technologies, it is essential to include spatio-temporal dynamics properly in the standard data models. Increased knowledge of the behaviour of groundwater resources, supported by a technical system built on a land administration counterpart, could help improve greater sustainability in the use of such resources. Considering the specific arrangements of rights, parties and spatial units this could, if desired, also provide the base for a regulated private market in groundwater assets. Further research will be needed to fully operationalize and implement such data models, which ultimately could produce outputs at case study level which can help to formulate policies regarding natural resources more on the basis of technical inputs

Spatial dimensions of land administration and user rights over groundwater: case study of Kerala, India vs. Coca Cola

Supporting the management of rights related to groundwater based on input from hydrogeology software is contributing to bridging the gap between the technical and administrative aspects of groundwater management. The research reported herein is focused on a specific example (or ‘use case’ in UML terminology), resulting from a court action by Kerala State in India, against the Coca-Cola company, on the overexploitation of the local groundwater aquifer. The use case reports on the economic and policy contexts conducing to the establishment of the Coca-Cola bottling plant in Plachimada, and the ensuing court actions, triggered by the local community assembly first, and then by Kerala State authority, on the grounds of the introduction of toxic waste into the groundwater, making the water unfit for human consumption, and the depletion of the aquifer. Considering the specifics of the use case, the ISO/TC211 Land Administration Domain Model (LADM, DIS 19152) is used as a basis for the development of a specialized profile addressing the need to define laws and regulations with proper spatial and temporal dimensions, to represent the rights to groundwater use by the local communities. Two alternative scenarios are reported: the first is based in the consideration that all the different Property parcels are regulated by Private Law; the second, further develops on the consideration of groundwater as a Public Trust, thus regulating private use through the Public Law domain. The modelling here provided goes from a subset of the LADM conceptual classes to more specialized classes, and is reported through the use of class and instance level (object) diagrams. These build on the existing spatial unit package and the legal and administrative profile, demonstrating the flexibility which can be introduced by LADM. Specifically concerning the representation of spatial units, a previously proposed ‘Mixed 2D/3D’ spatial profile is further developed, addressing the needs of the use case. In combination with the ‘Level’ representation of LADM to organize spatial units, it can contribute to an easier reuse of existing, 2D based, land parcels data, into the proposed 3D and time based model architecture. Concluding, the modelling and architectural framework here reported contributes to a more informed decision in the choice of groundwater rights to be made by the law, policy and courts, taking into account societal needs and changes induced by new socio-economic contexts. The resulting institutional setting will be best informed with spatial and temporal data, and the legal solution chosen be it public or private law focused, can be recorded in a system based on the LADM standard; it allows for much flexibility and only a few specific classes need to be added and further specified in order to be implemented

The modelling of spatial units (parcels) in the land administration domain model (LADM)

The Land Administration Domain Model (LADM) is under development within the Technical Committee 211 (TC211) of the International Organisation for Standardization (ISO) and identified as ISO 19152. Within the LADM classical cadastral concepts as “parcel” and “boundary” have been extended to be able to include spatial representations of overlapping tenures or claims and also multidimensional objects (3D and 2D/3D, combined with temporal dimensions). Furthermore, a series of new representations are possible apart from topologically well structured parcels (here called spatial units). Text based, sketch based, point based, line-based, polygon based, or topological based representations of spatial units are possible. The topological spatial units are defined by a consistent topological structure(with no gaps, overlaps or intersections), which is in contrast with a set of polygons, where a consistent topological structure is not guaranteed. A line-based spatial unit is represented by a collection of lines which may be collected from different sources or surveys. A point-based spatial unit contains only the coordinates of the unit’s reference point. A text based spatial unit is not represented by coordinates, but has a spatial unit description in words, e.g. the metes and bounds system (a spatial unit description in terms of distance, direction, and landmarks). All these spatial units may have a 3D representation, and a provision is made for a mixture of 2D and 3D spatial units to co-exist. A level is a collection of spatial units with a geometric or thematic coherence. The concept of level is related to the notion of “legal independence” from ‘Cadastre 2014’. This allows for the flexible introduction of spatial data from different sources and accuracies, including utility networks, buildings and other 3D spatial units, such as mining claims, or construction works. The paper explores the LADM spatial component, which is further based on ISO standards, combined with new concepts as “boundary face string” and partially unbounded primitives. Spatial profiles and the different spatial representations are used to demonstrate the flexibility of spatial representations of this domain model; for formal and non formal land administrations systems alike. The first trial implementation of the Queensland (Australia)Digital Cadastral Database (DCDB) for 2D parcel encoding using the line-based spatial profile will be discussed in detail, together with the polygon based spatial profile for the spatial units of the Portuguese land administration

Stochastic networked control systems with dynamic protocols

We consider networked control systems in which sensors, controllers, and actuators communicate through a shared network that introduces stochastic intervals between transmissions, delays and packet drops. Access to the communication medium is mediated by a protocol that determines which node (one of the sensors, one of the actuators, or the controller) is allowed to transmit a message at each sampling/actuator-update time. We provide conditions for mean exponential stability of the networked closed loop in terms of matrix inequalities, both for investigating the stability of given protocols, such as static round-robin protocols and dynamic maximum error first-try once discard protocols, and to design new dynamic protocols. The main result entailed by these conditions is that if the networked closed loop is stable for a static protocol then we can provide a dynamic protocol for which the networked closed loop is also stable. The stability conditions also allow for obtaining an observer protocol pair that reconstructs the state of an LTI plant in a mean exponential sense and less conservative stability results than other conditions that previously appeared in the literatur

Software e Dados Abertos para o Cadastro Predial em Portugal: Antecedentes e Perspetivas face à mais recente Legislação

Os principais tipos de Cadastro Predial que atualmente coexistem em Portugal sob diferentes regimes, enquadrados em legislação passada e não revogada nas últimas dezenas de anos, são examinados aqui do ponto de vista da sua acessibilidade e tratamento na perspetiva dos modernos conceitos de Dados e de Software Abertos. Foi adotada uma estrutura baseada na evolução histórica do Cadastro Predial. Parte-se desde a transição da informação cadastral ainda em formatos convencionais, representada pelo Cadastro Geométrico da Propriedade Rústica (CGPR), para o primeiro Cadastro Predial executado em formato digital. Desta primeira fase, são reportadas a natureza, extensão e acessibilidade aos dados recolhidos, tendo em conta nomeadamente a sua incorporação no Registo Nacional de Dados Geográficos, integrado na iniciativa INSPIRE. Segue-se a definição e execução do cadastro elaborado sob o regime experimental denominado SINERGIC, e o trabalho desenvolvido a este nível no uso de ferramentas de software e dos dados recolhidos nestas operações. Referem-se também outros organismos que habitualmente recolhem informação da carácter cadastral, embora não obedeçam aos diferentes cadastros “oficiais”. Acrescenta-se uma perspetiva internacional, através da referência aos esforços da UN-Habitat e outros organismos que suportam o “Global Land Tool Network” e do seu desenvolvimento da ferramenta de código aberto STDM. Conclui-se com uma breve análise à mais recente legislação do Cadastro Simplificado, e às perspetivas de desenvolvimento de Dados Abertos e de Software Aberto de suporte ao Cadastro Predial em Portugal