Jorge L. Ortega-Arjona

The Secure Pipes and Filters Pattern

Many applications process or transform a stream of data. Such applications are organized as a sequence of different stages, which may be independent enough to be simultaneously carried out. The original Pipes and Filters pattern and the Parallel Pipes and Filters pattern describe those actions. We present here the Secure Pipes and Filters pattern as a secure version of the original patterns, which contains a minimal set of security mechanisms to provide a set of basic security functions. The Secure Pipes and Filters pattern includes ways to add security controls at each stage of processing, controlling that only predefined operations are applied to data streams, as well as securing data movement.

Bounded communication between nodes of a networked control system as a strategy of scheduling

In a networked control system, several nodes exchange information through a network, to achieve specific control goals and thus increasing network traffic. This affects the overall system performance. Several approaches try to satisfy requirements of both control and communication performance. Particularly, some methodologies have been proposed to save bandwidth. One of such methodologies has been scheduling, which has been studied in depth through the last decade. Commonly, the objective of using scheduling to save bandwidth is to accurately use the computing resources. This paper shows two scheduling strategies, one performing static scheduling and the other carrying out dynamic scheduling, in order to expose the advantages of using dynamic scheduling in an ad hoc implementation. Both strategies execute on a real-time distributed system, and both are able to modify the frequency of transmission as well as the periods of tasks in individual components. Hence, both of them tend to impact on the quality of performance of the system, due to network use. The first scheduling strategy modifies the periods of task, and network access is assigned through a static scheduling algorithm. On the other hand, the second strategy, schedulability, is dynamically achieved by controlling the rate of frequency transmission into a frequency region, bounded by minimum and maximum transmission rates. Numerical simulations are used as implementations of both strategies.

Reconfiguration control strategy using Takagi–Sugeno model predictive control for network control systems – a magnetic levitation case study

Abstract This paper presents a reconfiguration control strategy for network control systems that makes use of a fuzzy Takagi–Sugeno model for predictive control. The dynamic behaviour of a network control system is modelled by using a real-time implementation of the scheduling algorithm. Here, this is applied for a magnetic levitation system, as a plant that is also modelled using a fuzzy Takagi–Sugeno approach. Thus, this paper covers several design issues, such as how to model a computer network, a plant, and a reconfiguration control strategy, as well as how the reconfiguration control strategy is modified using the fuzzy approach.

A Comparison of Two Software Architectures for General Purpose Mobile Service Robots

This paper exposes a set of tools which can be used to quantitatively evaluate the required effort to update the software system that operates a general purpose service mobile robot. These tools are used to compare a Blackboard-based and a Peer-to-Peer architectures in the context of mobile robotics. The analysis consider the development cost for an update, as well as the response time for both architectures. The results show that it is regularly simpler to maintain a robotics software system with Blackboard architecture than when a Peer-to-Peer architecture is used. Also results show that there is no noticeable change in the response time or performance of the robot when using any architecture.

A consensus routing algorithm for mobile distributed systems

This paper introduces a consensus routing algorithm based on an availability function. Such a function obtains a consensus among a group of nodes by evaluating the idle time in the scheduler of each node, along with the general conditions of the network and determining the next step of the route. In this regard, the algorithm proposed here makes it possible to avoid flooding while reducing bandwidth use and keeping changes of the network only at a local scale.

Study of routing algorithms considering real time restrictions using a connectivity function

The paper focuses on the study of a mobile distributed system that is characterized by frequently changing topology. The routing algorithms [4,5,1] for such a system should be, in general, fully adaptive. Additionally, it is important to know the state of the task scheduler of each node in order to determine whether it acts as a router. Traditionally, existing routing algorithms [3,2] resort to the path discovery process for each modification in topology.

Applying architectural patterns for parallel programming an N-body simulation

The Architectural Patterns for Parallel Programming is a collection of patterns related with a method for developing the coordination structure of parallel software systems. These architectural patterns take as input information (a) the available parallel hardware platform, (b) the parallel programming language of this platform, and (c) the analysis of the problem to solve, in terms of an algorithm and data. In this paper, it is presented the application of the architectural patterns along with the method for developing a coordination structure for solving an N-Body Simulation. The method used here takes the information from the problem analysis, selects an architectural pattern for the coordination, and provides some elements about its implementation.

Applying architectural patterns for parallel programming: solving the two-dimensional wave equation

The Architectural Patterns for Parallel Programming is a collection of patterns related with a method for developing the coordination structure of parallel software systems. These architectural patterns are applied based on (a) the available parallel hardware platform, (b) the parallel programming language of this platform, and (c) the analysis of the problem to solve, in terms of an algorithm and data. In this paper, it is presented the application of the architectural patterns along with the method for developing a coordination structure for solving the Two-dimensional Wave Equation. The method used here takes the information from the problem analysis, applies an architectural pattern for the coordination, and provides some elements about its implementation. This paper is aimed to those who are working with the Patterns for Parallel Software Design. Nevertheless, it presents only a part of the method, at the architectural level, for solving the Two-dimensional Wave Equation. Other two further design issues should be addressed at the communication and synchronization levels, which are not presented here.

Fault localization using neural networks and observers for autonomous elements

Fault detection and isolation (FDI) has become a useful strategy for determining fault appearance and on-line reconfiguration. However, unknown scenarios during on-line performance are still an open field for research. Different methods, such as knowledge-based techniques or analytical redundancy, have been followed. Nevertheless, both methods present inherent drawbacks for isolation. The present paper introduces a combined approach of model- and knowledge-based methods, using an autonomous element for isolation of unknown scenarios during on-line stage. The contribution is to integrate both methods to accomplish fault localization for unknown scenarios, based on previous information. Faults are constrained to certain bounded frequency response.

Modelling of Networked Control Systems

This chapter shows models for time delays and others network imperfections generated into NCS and how they are integrated into control, scheduling or codesign algorithms. First, a time delay model is presented using a generalized exponential distribution based function with data collect from non-deterministic networks. After, three NCS models are presented, each incorporates information about the network imperfections with the ultimate aim of generating a corrective action. We present models based on control, communication and codesign methodologies. Finally, a neuro-fuzzy identification is presented to model the system states and estimate the parameters of the NCS based on multi-sampling periods.