Federated Robust Embedded Systems: Concepts and Challenges

The development within the area of embedded systems (ESs) is moving rapidly, not least due to falling costs of computation and communication equipment. It is believed that increased communication opportunities will lead to the future ESs no longer being parts of isolated products, but rather parts of larger communities or federations of ESs, within which information is exchanged for the benefit of all participants. This vision is asserted by a number of interrelated research topics, such as the internet of things, cyber-physical systems, systems of systems, and multi-agent systems. In this work, the focus is primarily on ESs, with their specific real-time and safety requirements. While the vision of interconnected ESs is quite promising, it also brings great challenges to the development of future systems in an efficient, safe, and reliable way. In this work, a pre-study has been carried out in order to gain a better understanding about common concepts and challenges that naturally arise in federations of ESs. The work was organized around a series of workshops, with contributions from both academic participants and industrial partners with a strong experience in ES development. During the workshops, a portfolio of possible ES federation scenarios was collected, and a number of application examples were discussed more thoroughly on different abstraction levels, starting from screening the nature of interactions on the federation level and proceeding down to the implementation details within each ES. These discussions led to a better understanding of what can be expected in the future federated ESs. In this report, the discussed applications are summarized, together with their characteristics, challenges, and necessary solution elements, providing a ground for the future research within the area of communicating ESs

Federated Embedded Systems – a review of the literature in related fields

This report is concerned with the vision of smart interconnected objects, a vision that has attracted much attention lately. In this paper, embedded, interconnected, open, and heterogeneous control systems are in focus, formally referred to as Federated Embedded Systems. To place FES into a context, a review of some related research directions is presented. This review includes such concepts as systems of systems, cyber-physical systems, ubiquitous computing, internet of things, and multi-agent systems. Interestingly, the reviewed fields seem to overlap with each other in an increasing number of ways

Optimization of Manufacturing Cells Using Discrete Event Models

As the name suggests, this thesis is concerned with flexible manufacturing systems (FMS) and their way of living. More specifically, the main objective of this workis to generate working schedules for the moving objects of the manufacturing cells. These schedules should be optimal in some sense, while situations involving several moving objects blocking each other or colliding should be avoided.If such working schedules could be generated automatically and efficiently, the flexibility together with the productivity of the manufacturing cells would be affected positively. To guarantee safe FMS functionment, production cells are modeled in terms of discrete event systems (DES), whereafter supervisory control theory helps to prevent undesirable behaviour. The modeling procedure is done automatically, leaving the field open for the efficiency considerations. In this work, several methods for exploring DES in search for a time optimalworking sequence, based on the ideas of mixed integer linear programming, A* search and visibility graphs, are presented and studied with respect to their efficiency and robustness. In the final part of this work, the focus is shifted towards the reduction of the acceleration load imposed on the moving objects in a production cell. Thisleads to a decrease of strain on the manufacturing equipment, thus prolonging the productive life of the FMS. Naturally, the acceleration reduction should be, and thus is, done without compromising such qualities of the working schedule as time optimality, collision- and deadlock avoidance

Optimization of Manufacturing Cells Using Discrete Event Models

As the name suggests, this thesis is concerned with flexible manufacturing systems (FMS) and their way of living. More specifically, the main objective of this workis to generate working schedules for the moving objects of the manufacturing cells. These schedules should be optimal in some sense, while situations involving several moving objects blocking each other or colliding should be avoided.If such working schedules could be generated automatically and efficiently, the flexibility together with the productivity of the manufacturing cells would be affected positively. To guarantee safe FMS functionment, production cells are modeled in terms of discrete event systems (DES), whereafter supervisory control theory helps to prevent undesirable behaviour. The modeling procedure is done automatically, leaving the field open for the efficiency considerations. In this work, several methods for exploring DES in search for a time optimalworking sequence, based on the ideas of mixed integer linear programming, A* search and visibility graphs, are presented and studied with respect to their efficiency and robustness. In the final part of this work, the focus is shifted towards the reduction of the acceleration load imposed on the moving objects in a production cell. Thisleads to a decrease of strain on the manufacturing equipment, thus prolonging the productive life of the FMS. Naturally, the acceleration reduction should be, and thus is, done without compromising such qualities of the working schedule as time optimality, collision- and deadlock avoidance

Optimal Coordination of Flexible Manufacturing Systems, with Automatic Generation of Collision- and Dealock-Free Working Schedule

The ever more rapidly changing markets pose high demands on the modern industry, often making it necessary to have varied and frequently updated product portfolios. As a consequence, modern industrial systems need to be easily adaptable to different kinds of products, which makes the use of flexible manufacturing systems (FMS) increasingly popular. An FMS generally contains a number of moving actors, such as production robots, conveyor belts, etc, that can be configured for different tasks. However, a big challenge with FMS is their high complexity, which makes FMS coordination a time and resource demanding undertaking. In this thesis, the challenge of FMS coordination is accepted, with the goal of developing methods for automatic and off-line generation of a correct, safe and time optimal working logic for the moving actors of a given FMS. This means that the order of operations in the studied FMS should minimize the total cycle time of the system and respect all specifications, while avoiding collisions and blocking situations between the moving actors.To represent possible and specified FMS behavior, deterministic finite automata (DFA) models are used. A method to automatically generate such models is presented, whereafter much work is laid at developing optimization methods, applicable to DFAs. While we start out with considering normal FMS behavior, a method for treating FMS that suffer from uncontrollable operations, such as machine breakdown or manually ordered product inspection, is also presented. When relating our results to the real world, we noted that the optimal control logic often induces uneven movement patterns to the FMS actors. This inconvenience is thus studied and amended.Finally, combining our results with some existing techniques, a framework for automatic generation of control code from 3D simulation models of FMS is presented. In developing this framework, functionality common to most robot simulation environments is used where possible to facilitate the portability of the approach between different simulation tools

Time-Optimal Coordination of Flexible Manufacturing Systems Using Deterministic Finite Automata and Mixed Integer Linear Programming

Abstract Automation and flexibility are often mentioned as key concepts in modern production industry. To increase the level of flexibility, deterministic finite automata (DFA) can be used to model, specify and verify the production systems. Often, it is also desirable to optimize some production criteria, such as for example the cycle time of a manufacturing cell. In this paper, a method for automatic conversion from DFA to a mixed integer linear programming (MILP) formulation is first presented. This conversion is developed for a number of DFA structures that have shown to be useful in practical applications. Special attention is paid to reducing the search region explored by the MILP solver. Second, a conversion from the MILP solution to a DFA supervisor is described. This allows to combine the advantages of DFA modeling with the efficiency of MILP and supervisory control theory to automatically generate time-optimal, collision-free and non-blocking working schedules for flexible manufacturing systems

Velocity balancing in flexible manufacturing systems

Practical incentives motivate the development of optimal working schedules in manufacturing environments. Most often, such development is focused on time optimality issues, without concern for how the resulting schedules are executed. In practice, this often leads to an unnecessarily high amount of acceleration during a production cycle, which affects negatively the productive life of the manufacturing equipment. In this paper, we present and compare several methods to reduce the acceleration load in a production cell by processing a given working schedule, without compromising such features of the schedule as cycle time optimality, collision- and deadlock avoidance

Velocity Balancing in Flexible Manufacturing Systems

Practical incentives motivate the development of optimal working schedules in manufacturing environments. Most often, such development is focused on time optimality issues, without concern for how the resulting schedules are executed. In practice, this often leads to an unnecessarily high amount of acceleration during a production cycle, which affects negatively the productive life of the manufacturing equipment. In this paper, we present and compare several methods to reduce the acceleration load in a production cell by processing a given working schedule, without compromising such features of the schedule as time optimality, collision- and deadlock avoidance