Real-time and fault tolerance in distributed control software

Closed loop control systems typically contain multitude of spatially distributed sensors and actuators operated simultaneously. So those systems are parallel and distributed in their essence. But mapping this parallelism onto the given distributed hardware architecture, brings in some additional requirements: safe multithreading, optimal process allocation, real-time scheduling of bus and network resources. Nowadays, fault tolerance methods and fast even online reconfiguration are becoming increasingly important. All those often conflicting requirements, make design and implementation of real-time distributed control systems an extremely difficult task, that requires substantial knowledge in several areas of control and computer science. Although many design methods have been proposed so far, none of them had succeeded to cover all important aspects of the problem at hand. [1] Continuous increase of production in embedded market, makes a simple and natural design methodology for real-time systems needed more then ever

CSP design model and tool support

The CSP paradigm is known as a powerful concept for designing and analysing the architectural and behavioural parts of concurrent software. Although the theory of CSP is useful for mathematicians, the programming language occam has been derived from CSP that is useful for any engineering practice. Nowadays, the concept of occam/CSP can be used for almost every object-oriented programming language. This paper describes a tree-based description model and prototype tool that elevates the use of occam/CSP concepts at the design level and performs code generation to Java, C, C++, and machine-readable CSP for the level of implementation. The tree-based description model can be used to browse through the generated source code. The tool is a kind of browser that is able to assist modern workbenches (like Borland Builder, Microsoft Visual C++ and 20-SIM) with coding concurrency. The tool will guide the user through the design trajectory using support messages and several semantic and syntax rule checks. The machine-readable CSP can be read by FDR, enabling more advanced analysis on the design. Early experiments with the prototype tool show that the browser concept, combined with the tree-based description model, enables a user-friendly way to create a design using the CSP concepts and benefits. The design tool is available from our URL, http://www.rt.el.utwente.nl/javapp

A new model for solution of complex distributed constrained problems

In this paper we describe an original computational model for solving different types of Distributed Constraint Satisfaction Problems (DCSP). The proposed model is called Controller-Agents for Constraints Solving (CACS). This model is intended to be used which is an emerged field from the integration between two paradigms of different nature: Multi-Agent Systems (MAS) and the Constraint Satisfaction Problem paradigm (CSP) where all constraints are treated in central manner as a black-box. This model allows grouping constraints to form a subset that will be treated together as a local problem inside the controller. Using this model allows also handling non-binary constraints easily and directly so that no translating of constraints into binary ones is needed. This paper presents the implementation outlines of a prototype of DCSP solver, its usage methodology and overview of the CACS application for timetabling problems

Schedulability analysis of timed CSP models using the PAT model checker

Timed CSP can be used to model and analyse real-time and concurrent behaviour of embedded control systems. Practical CSP implementations combine the CSP model of a real-time control system with prioritized scheduling to achieve efficient and orderly use of limited resources. Schedulability analysis of a timed CSP model of a system with respect to a scheduling scheme and a particular execution platform is important to ensure that the system design satisfies its timing requirements. In this paper, we propose a framework to analyse schedulability of CSP-based designs for non-preemptive fixed-priority multiprocessor scheduling. The framework is based on the PAT model checker and the analysis is done with dense-time model checking on timed CSP models. We also provide a schedulability analysis workflow to construct and analyse, using the proposed framework, a timed CSP model with scheduling from an initial untimed CSP model without scheduling. We demonstrate our schedulability analysis workflow on a case study of control software design for a mobile robot. The proposed approach provides non-pessimistic schedulability results

City strategy : final evaluation

The City Strategy (CS) concept was first announced in the 2006 Welfare Reform Green Paper – A new deal for welfare: Empowering people to work. CS was designed at a time of growth in the national economy to combat enduring pockets of entrenched worklessness and poverty in urban areas by empowering local institutions to come together in partnerships to develop locally sensitive solutions. It was premised on the idea that developing a better understanding of the local welfare to work arena would allow partnerships to align and pool funding and resources to reduce duplication of services and fill gaps in provision. The ‘theory of change’ underlying CS suggested that such an approach would result in more coordinated services which would be able to generate extra positive outcomes in terms of getting people into jobs and sustaining them in employment over and above existing provision. CS was initially set to run for two years from April 2007 to March 2009 in 15 CS Pathfinder (CSP) areas, varying in size from five wards in one town through single local authority areas to subregional groupings of multiple local authority areas, across Great Britain. In July 2008, the Secretary of State for Work and Pensions announced an extension for a further two years to March 2011. In April 2009, two local areas in Wales, which were in receipt of monies from the Deprived Areas Fund (DAF), were invited by the Department for Work and Pensions (DWP) to form local partnerships with a similar remit to the CSPs, albeit more limited in scope – to develop locally sensitive solutions to economic inactivity, to the CSPs. During the period that the CS initiative was operational, economic conditions changed markedly with a severe recession, followed by fragile recovery. The CSPs had to cope with ongoing changes in policy throughout the lifetime of the CS initiative, including a General Election and a new Coalition Government at Westminster early in the fourth year. While policy changes are a fact of life for local practitioners operating in the welfare to work arena, the global recession in 2008/09 marked a fundamental change in the context in which local partnerships operated

Branching: the Essence of Constraint Solving

This paper focuses on the branching process for solving any constraint satisfaction problem (CSP). A parametrised schema is proposed that (with suitable instantiations of the parameters) can solve CSP's on both finite and infinite domains. The paper presents a formal specification of the schema and a statement of a number of interesting properties that, subject to certain conditions, are satisfied by any instances of the schema. It is also shown that the operational procedures of many constraint systems including cooperative systems) satisfy these conditions. Moreover, the schema is also used to solve the same CSP in different ways by means of different instantiations of its parameters.Comment: 18 pages, 2 figures, Proceedings ERCIM Workshop on Constraints (Prague, June 2001

Process evaluation of five integrated offender management pioneer areas

A qualitative process evaluation of five Integrated Offender Management (IOM) pioneer areas was undertaken to assess implementation of IOM, identify approaches to implementation and capture the lessons learnt. The findings indicated that IOM enabled structural changes, transforming the delivery of offender management. There was considerable commitment and enthusiasm for IOM at the sites, whilst acknowledging barriers to development such as definition, resourcing, governance and clarity of agency roles. Since the evaluation took place, the political and criminal justice landscape has changed somewhat, supporting a more locally driven approach which can draw on the learning directly from the pioneers which were shaped and delivered locally