Interactive computer methods for design optimization

Two interactive methods for design optimization are discussed in this paper. The first method is implemented by the computer program GDOPT and is an essentially manual search procedure based on graphical searches of the design space within user-defined planes. In contrast, the computer program ADOPT consists of the more effective nonlinear programming techniques available and the search is mostly under computer control. The user observes progress on a graphical display and is able to modify the search procedure as desired. These two interactive methods make an extensive use of computer graphics to display search results in the form of graphs, contour plots, sensitivity curves, and search trajectories. The designer interacts with the programs through these displays and is an active participant in the decision making process. It is believed that this integrated approach to design optimization can result in an enhanced understanding of the design problem and an effective convergence to the optimum design. An example is presented which illustrates the effectiveness of this interactive technique.     

Development methods for trusted computer systems

Conclusion Well-designed computer systems can be safer than hardwired alternatives, and computer systems can control processes which are too complex for hardwired solutions, or where the hardwired solution is uneconomic.     

Software design methods for distributed computer control

The design of software for distributed computer control systems (DCCS) is a field which has benefited greatly from certain software engineering concepts and methodologies that are used in computer science. This paper aims at reviewing some of the more commonly used software tools that help the control engineer to simplify software design for distributed control. The paper describes the current situation, and the tools which are now available.     

Modular design of information encipherment for computer systems

The application of Vigenere ciphers to the design of enciphering systems for computer systems is presented. Considerations are based on two theorems which enable the generalization of Vigenere ciphers giving the lower bound on the probability of breaking a key. The application of theorems to the design of an enciphering module, that makes possible, in a simple way, the design of arbitrarily complex enciphering systems is shown. Such modular design easily permits fitting the degree of protection to the requirements of the user. The enciphering process with the use of an enciphering module is compared, qualitatively, with the DES recommended by the U.S. National Bureau of Standards.     

Mathematical methods to study the polling systems

Reviewed were the mathematical methods that are used to investigate the polling systems which found wide application in modeling and design of various transport and industrial processes. Emphasis was made on the models of polling systems used to investigate the wireless broadband networks. The polling systems were classified; presented were stochastic models and methods of investigating discrete-time and continuous-time systems, systems with cyclic, periodic, and random queue polling, as well as the methods of their optimization.     

Mathematical methods for the design of telephone directory content and distribution

This paper contains a mathematical model and an associated heuristic solution algorithm for the problem of dividing a geographical area into exhaustive and possibly overlapping subsets representing telephone directory content and distribution. The objective function is nonlinear in terms of the zero-one integer assignment variables. Some of the constraints, representing the requirement that the subsets be simply connected, cannot be formulated analytically. As the complexity of the model precluded exact analytic solutions a sequential optimization procedure has been developed which leads to good, but not necessarily optimal results. The computer program implementing the algorithm is also described.     

A scheme for the realization of graphical computer aided design systems

We present some of the problems encountered in the study of CAD systems in an electro-mechanical company, and propose a methodology based entirely on a detailed object study. In the first part of this paper we analyse the traditional design process in the company and define the most important functions of a CAD system. In the second part, we show how a functional hierarchical decomposition of the product helps us to realize the CAD system, and then we describe the practical application.     

Special issue on the use of computer algebra systems for computer aided control system design

The importance of the continuing and growing need in the systems and control community for reliable algorithms and robust numerical software for increasingly challenging applications is well known and has already been reported elsewhere (IEEE Control Systems Magazine, Vol. 24, Issue 1). However, we have all had the experience of working on a mathematical project where an increased number of symbolic manipulations was needed. In a simple case, the required computation might have been to compute the Laplace transform or the inverse Laplace transform of a function, or to find the transfer function matrix for a given system topology where parameters are included. In a more demanding situation the required computation might have been to find the parametric family of solutions of a polynomial matrix Diophantine equation resulting from a variety of control problems such as those associated with stabilization, decoupling, model matching, tracking and regulation, or to compute the Smith McMillan form of a rational transfer function matrix in order to obtain a better insight into a number of structural properties of a system. The desire to use a computer to perform long and tedious mathematical computations such as the above led to the establishment of a new area of research whose main objective is the development: (a) of systems (software and hardware) for symbolic mathematical computations, and (b) of efficient symbolic algorithms for the solution of mathematically formulated problems. This new subject area is referred to by a variety of terms such as symbolic computations, computer algebra, algebraic algorithms to name a few. During the last four decades this subject area has accomplished important steps and it is still continuing its evolution process.     

Open-loop discretization methods for control systems design

In this paper, a unified theory is presented which addresses essential aspects of the open-loop discretization procedure. Initially, factors which affect the generation and propagation of discretization errors are identified by analytical, heuristic and experimental arguments. Following this, a discretization algorithm is presented which takes these factors into account. The fundamental idea of the discretization method is the replacement of the analogue integrators of the prototype continuous-time system by discrete-time approximations. This is done in such a way as to optimize a given cost function with respect to a given input. Unlike many discretization schemes presented in the literature, the procedure developed attempts to first determine the magnitude of the expected discretization errors, and then discretize with an appropriate complexity, giving the designer control over the order of the discrete-time system. This appears to be an effective means of designing filters with low complexity which still retain essential properties of the prototype system. An emphasis of this work is to view the discretization process from a control theory and engineering perspective. This results in a number of new perspectives relating to the discretization process.     

Mathematical modeling for optimal design of in-building distributed antenna systems

In-building Distributed Antenna System (IB-DAS) has proven to be one of the most promising In-Building Solutions (IBS) to provide coverage and capacity for indoor users. We consider optimal deployment of the passive IB-DAS, focusing on mathematical optimization models based on integer programming, for the topology design and optimal equipment selection of IB-DAS. The models minimize the cable cost and keep the transmit power at each antenna within a given interval defined for coverage and interference control. The models can deliver optimal solutions to systems of which the size is of practical relevance. To improve the time efficiency, we develop preprocessing techniques that integrate the building layout data into the system modeling. Application of the models to realistic IB-DAS deployment demonstrates the effectiveness of the models.     

The design of distributed control computer systems

The top-down approach in the design of Distributed Control Computer Systems, DCCS, is presented. The starting point of the study is three statements: (i) the design approach should be production process control oriented; (ii) for real time process control applications, computer networks require an efficient communication subsystem, the most important features of which are high reliability and short message transmission times and (iii) recent research has shown that the tools and methodologies used in both computing and control should be complementary to each other in order to solve some of the distributed control computer system/distributed computer control system design problems. The paper contains the design problems of distributed control computer systems, the presentation of the methods and tools for the study and design of the DCCS, the top-down approach in the design of the DCCS, and examples of two design stages.