Redes de Petri en la automatización de una máquina tampográfica de plásticos

Se documenta la implementación de la rutina de programación de una máquina para tampografía Comec-1998 usada para la impresión de piezas de plástico. El ciclo de trabajo comprende tres rutinas: batido de tinta, operación de ciclo sencillo y operación de ciclo continuo; programadas con tres cilindros, cuatro finales de carrera y dos temporizadores. Después de identificar los elementos para el ciclo de trabajo, se establecen las condiciones para generar los estados. Las transiciones en la red de Petri sirven para ir de un lugar a otro, usando la Automatización de las Redes de Petri y los conceptos de la Lógica de Pase de Tokens. Un PLC Siemens S7-200 se programó en programa KOP Ladder, dada la simplicidad y facilidad al pasar de la red de Petri al diagrama de lógica cableada

Extension based limited lookahead supervision of discrete event systems

Abstract Supervisory control of discrete event systems using limited lookahead has been studied by Chung-Lafortune-Lin, where control is computed by truncating the plant behavior up to the limited lookahead window. We present a modification of this approach in which the control is computed by extending the plant behavior by arbitrary traces beyond the limited lookahead window. The proposed supervisor avoids the notion of pending traces. Consequently the need for considering either a conservative or an optimistic attitude regarding pending traces (as in the work of Chung-LafortuneLin) does not arise. It was shown that an optimistic attitude may result in violation of the desired specifications. We demonstrate here that a conservative attitude may result in a restrictive control policy by showing that in general the proposed supervisor is less restrictive than the conservative attitude based supervisor. Moreover, the proposed approach uses the notion of relative closure to construct the supervisor so that it is non-blocking even when the desired behavior is not relative closed (Chung-LafortuneLin assume relative closure). Finally, the proposed supervisor possesses all the desirable properties that a conservative attitude based supervisor of Chung-Lafortune-Lin possesses. We illustrate our approach by applying it to concurrency control in database management systems

Lower Bound for the Duration of Event Sequences of Given Length in Timed Discrete Event Systems

The Supervisory Control Theory (SCT) of Discrete Event Systems (DES) provides a framework for synthesizing a DES supervisor to ensure a DES plant satisfies its design specification. In SCT, supervisor synthesis is performed offline before the functioning of the plant. Generally, the size of the plant and the specifications models are large resulting in supervisors that need huge computer memory for storage -- usually unavailable in embedded systems. A solution to this problem proposed in the literature is Limited Lookahead Policy (LLP). In LLP, the supervisory control commands are calculated online during the plant operation. After the occurrence of each event, the next control command is calculated based on the plant behaviour over a limited number of events into the future. In practice such frequent LLP computation would not be feasible as multiple events can occur consecutively over a short duration, not leaving enough time for LLP computation between them. To tackle this issue, a method is proposed called LLP with Buffering where the supervisory control commands are calculated online and buffered in advance for a predefined window of events in future. Determining the correct size of the buffer is crucial in order to achieve a trade-off between the on-board memory requirement and the computational resources and also ensuring that new supervisor commands are computed before the buffer runs out empty. The size of the buffer primarily depends on (1) the execution time of the code for supervisor calculation and (2) the (fastest) rate of event generation in the plant. This thesis focuses on the second factor. Previously, the minimum execution duration of event sequences has been calculated experimentally. The experimental approach is not exhaustive and thus results in an overestimate in the value of the minimum execution duration of event sequences. In this thesis, a model-based approach to the computation of the minimum duration is proposed which begins by transforming the untimed model of the plant under supervision into a timed automaton (TA) by incorporating timing information of the events. Next, an exhaustive symbolic matrix-based search algorithm is proposed where all the event sequences from every mode of the TA model are traversed to determine the minimum execution duration of the event sequences. The proposed method avoids the reachability analysis of TA needed to determine the reachable clock regions for each mode. The number of these regions is exponential in the number of events. Instead, the method uses reachability on the graph of the untimed model (polynomial in the number of events). This algorithm runs faster but provides an underestimate for the minimum execution duration of event sequences. Next, a two-degree-of-freedom solar tracker system is used as a plant to analyse the timing behaviour of the events and the implementation of LLP with buffering. In this study, the model-based and experimental methods have been used together to choose a suitable buffer size. The resulting LLP supervisor with buffering has been successfully implemented

Autonomy in the real real-world: A behaviour based view of autonomous systems control in an industrial product inspection system

The thesis presented in this dissertation appears in two sequential parts that arose from an exploration of the use of Behaviour Based Artificial Intelligence (BBAI) techniques in a domain outside that of robotics, where BBAI is most frequently used. The work details a real-world physical implementation of the control and interactions of an industrial product inspection system from a BBAI perspective. It concentrates particularly on the control of a number of active laser scanning sensor systems (each a subsystem of a larger main inspection system), using a subsumption architecture. This industrial implementation is in itself a new direction for BBAI control and an important aspect of this thesis. However, the work has also led on to the development of a number of key ideas which contribute to the field of BBAI in general. The second part of the thesis concerns the nature of physical and temporal constraints on a distributed control system and the desirability of utilising mechanisms to provide continuous, low-level learning and adaptation of domain knowledge on a sub-behavioural basis. Techniques used include artificial neural networks and hill-climbing state-space search algorithms. Discussion is supported with examples from experiments with the laser scanning inspection system. Encouraging results suggest that concerted design effort at this low level of activity will benefit the whole system in terms of behavioural robustness and reliability. Relevant aspects of the design process that should be of value in similar real-world projects are identified and emphasised. These issues are particularly important in providing a firm foundation for artificial intelligence based control systems

Stocks for All

Public stock markets are too small. This book is an effort to rescue public stock markets in the EU and the US. There should be more companies with publicly-traded shares and more direct share ownership. Anchored in a broad historical study of the regulation of stock markets and companies in Europe and the US, the book proposes ways to create a new regulatory regime designed to help firms and facilitate people’s capitalism

Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90)

The proceedings of the SOAR workshop are presented. The technical areas included are as follows: Automation and Robotics; Environmental Interactions; Human Factors; Intelligent Systems; and Life Sciences. NASA and Air Force programmatic overviews and panel sessions were also held in each technical area

Arquitectura asimétrica multicore con procesador de Petri

Se ha determinado, en una arquitectura multi-Core SMP, el lugar donde incorporar el PP o el HPP sin alterar el ISA del resto de los core. Se ha obtenido una familia de procesadores que ejecutan los algoritmos de Petri para dar solución a sistemas reactivos y concurrentes, con una sólida verificación formal que permite la programación directa de los procesadores. Para esto, se ha construido el hardware de un PP y un HPP, con un IP-Core en una FPGA, integrado a un sistema multi-Core SMP, que ejecuta distintos tipo de RdP. Esta familia de procesadores es configurable en distintos aspectos: - Tamaño del procesador (cantidad de plazas y transiciones). - Procesadores con tiempo y procesadores temporales. - Arquitectura heterogénea, que permite distribuir los recursos empleados para instanciar el procesador según se requiera, y obtener un ahorro sustancial. - La posibilidad de configurar el procesador en pos de obtener los requerimientos y minimizar los recursos. Muy valorado en la construcción de sistemas embebidos. En los sistemas con alta necesidad de concurrencia y sincronización, donde se ha evaluado este procesador, las prestaciones han mostrado una importante mejora en el desempeño. El procesador tiene la capacidad de resolver simultáneamente, por conjuntos múltiples disparos, lo que disminuye los tiempos de consulta y decisión, además los programas ejecutados cumplen con los formalismos de las RdP extendidas y sincronizadas, y los resultados de su ejecución son determinísticos. Los tiempos de respuesta para determinar una sincronización son de dos ciclos por consulta (entre la solicitud de un disparo y la respuesta).Facultad de Informátic