D.F. Garcia

Worst-case utilization bound for EDF scheduling on real-time multiprocessor systems

Presents the utilization bound for earliest deadline first (EDF) scheduling on homogeneous multiprocessor systems with partitioning strategies. Assuming that tasks are pre-emptively scheduled on each processor according to the EDF algorithm, and allocated according to the first-fit (FF) heuristic, we prove that the worst-case achievable utilization is 0.5(n+1), where n is the number of processors. This bound is valid for arbitrary utilization factors. Moreover, if all the tasks have utilization factors under a value /spl alpha/, the previous bound is raised, and the new utilization bound considering /spl alpha/ is calculated. In addition, we prove that no uniprocessor scheduling algorithm/allocation algorithm pair can provide a higher worst-case achievable utilization than that of EDF-FF. Finally, simulation provides the average-case achievable utilization for EDF-FF.

A novel real-time fuzzy-based diagnostic system of roll eccentricity influence in finishing hot strip mills

This paper proposes a method for the diagnosis of roll eccentricity influence on the strip thickness at the exit of a finishing hot strip mill (FHSM). Each exit strip thickness defect is related to one roll of the FHSM, allowing the implementation of an optimal policy for the substitution and maintenance of the rolls, while maintaining the required quality level of the strip. This policy allows the minimization of roll changes and the concentration of several changes at the same time, reducing production costs. Fuzzy logic is used to compare spectra, looking for common patterns, which enables a totally-automated diagnostic system. Likewise, as part of the solution, a novel estimate of roll eccentricity, based on a least-squares algorithm has been developed, which provides higher accuracy than classical algorithms as well as a drastic reduction in the time required to perform eccentricity tests.

A toolset for visualization and analysis of parallel real-time embedded systems based on fast prototyping techniques

This paper describes a toolset, whose objective is to provide full support for the analysis and testing of temporal behavior in the development of parallel realtime systems. The development approach supported by the toolset is based on an incremental prototyping technique combined with successive analyses and tests of the temporal behavior of prototypes carried out along the development cycle. The toolset is composed of three main tools: a prototyper, a monitor and visualizer/analyzer. Most current monitoring and analysis tools are oriented to measure and visualize the behavior of software entities (mainly processes) and the utilization of hardware resources, that is, the elements of the system design. In addition to this, this toolset incorporates a graph based model that provides a functional view of the behavior. This is expressed in terms of the sequences of activities executed by the system in response to the main external environment events (reactive aspect of real-time systems). Moreover, the toolset provides a powerful means to design and test the system under development in an incremental manner.

Specification, design and Modula-2 implementation of a low cost industrial control system

Abstract The purpose of this paper is to show the application of modern software engineering techniques to the construction of a small/medium size package for real time control. This package, denoted by SCM (acronym of “Sistema de Control Modular”), has been written in Modula-2 and presents all advantages offered by this high-level structured programming language. It has been implemented on a PC-AT compatible computer.

Real-time flatness sensor based on a linear-vision multiprocessor system (RV-05)

There has been an increase in the development of image processing applications in steel industries. In this paper, the authors describe a measurement system to obtain flatness defect indexes of products in hot strip mills. This system has been developed with lasers and linear-scan cameras. Every line scan camera is connected to a line scan processor board. All boards are in an industrial personal computer (industrial-PC) which governs the operation of boards. Moreover, it is possible to use an additional digital signal processor to accelerate the computation of algorithms. Flatness measurement devices, based on the optical triangulation principle, have been installed successfully by some manufacturers e.g. IRSID Lasershape, CRM Rometer, etc.<<ETX>>

A real-time expert system architecture based on a novel dynamic task scheduling technique

Computational characteristics of real-time expert systems have limited its integration in real-time control and monitoring environments. The computation time required to complete inferences carried out by expert systems present high variability, which usually leads to severe under-utilization of resources when the schedule of inferences is based on their worst computation times. Moreover, the event-based aperiodic activation of inferences increases the risk of transient overloads, as during critical conditions of the controlled or monitored environment the arrival rate of events increases. The dynamic scheduling technique presented in this article obtains statistical bounds of the time required to complete inferences on-line, and uses these bounds to schedule inferences achieving highly effective utilization of resources. In addition, this technique handles transient overloads using a robust approach. During overloads this technique completes nearly as many inferences as other dynamic scheduling techniques, but shows significantly better effective utilization of resources. The specific real-time architecture presented in this work, based on component object model (COM) technology, completes our approach to the problem of building efficient real-time rule-based systems suitable for controlling or monitoring complex industrial processes.

Flatness defect measurement system for steel industry on a real-time linear-image processor

There has been an appreciable increase in development of image processing applications in steel industries. In this paper, we are going to describe a measurement system to get flatness defect indexes of products in hot strip mills. This system has been developed with lasers and linear-scan cameras. Every line scan camera is connected to a line scan processor board. All boards are in an industrial personal computer (industrial-PC) which governs the operation of boards. Moreover, it is possible to use an additional digital signal processor to accelerate the computation of algorithms. Flatness measurement devices, based on the optical triangulation principle, has installed successfully by some manufacturers like Lasershape, CRM Rometer, etc.<<ETX>>

Different Control Strategy Results of an Hydro-Power Plant, using Ada

In the present paper, we show how we have implemented, using Ada language programming, different control strategies based on pole assignment and optimal criterions, for an hydro-power plant. We have solved the servodesign problem either by a feedforward control or by handling errors. An adaptive control procedure based in an I/O minimal structure is proposed, with the robustness of having a twenty four hours continuously performance with the object of being applicable industrially without the switch off from the adaptive loop. This control strategies can be used in the case we are presenting, replacing some techniques classier already proved.

A User-Customizable Supervision Level for Improving the Applicability of Explicit Self-Tuning Controllers

Abstract This paper is devoted to the analysis, development and evaluation of protection mechanisms, which have to be incorporated in self-tuning controllers so that they can operate correctly in industrial applications (section 1). The analysis begins with the definition of the problems which arise from the industrial utilization of this kind of controllers and the extension of the general loop structure of a self-tuning controller in order to incorporate the mentioned protection mechanisms (section 2). Next, a detailed study of the protection functions -supervisions-, is accomplished. The first one is the supervision of the start-up phase (section 3). Subsequently, the supervision of the parameter estimator is analized (section 4), carrying out a comparative study of the methods available at present, in order to preserve the estimator integrity. In the synthesis step supervision (section 5), the fiability of the new estimated model is analized, determining if it is adequate to synthesize a new controller. This leads to cautious controllers. It is also verified if the control law leads to an instable loop when it is combined with the estimated model (section 6). To achieve this, the behaviour of the loop’s signals, u(t) and y(t), is supervised. Next (section 7), the complete configuration selected for the supervision level is summarized. In order to show the effectiveness of this supervisor, several illustrative examples of its operation are presented. Finally (section 8), the conclusions obtained from this work are resumed.

Development and Application of Observers Based on Complex Mathematical Models For Hot Strip Mill Reheat Furnaces

Abstract The main objective of the article is to detail the current investigations to improve the control and supervision system of two identical walking-beam furnaces of a hot strip mill of the Ensidesa factory located in Aviles, Spain. The paper is structured as follows: in the first section the problem to be solved is introduced. The second part includes a brief description of the two furnaces. The following section is devoted to the development of a mathematical model for a generic continuous furnace. This represents the dynamic behaviour of the furnace, and it can be also used for obtaining of the steady-state behaviour of the furnace. These models allow the development and approximate evaluation of several control strategies before they are applied for online control. The next part is devoted to the development of observers for the furnace charge, based on simplifications of the dynamic model developed in the third section. At present, a very simple model is being implemented for on-line control. A comparative study between this simple observer and more elaborate ones is presented. Particularly, the on-line use posibilities of a more accurate two-dimensional slab model are analyzed. In the 5th section, the present control system is briefly described, performing an analysis of the possibilities offered by the new observer in order to close a control loop through them. In the next section the implementation of the mathematical model and some results of its application are illustrated. Finally, the conclusions obtained from this work are reviewed.