CIM includes the experimental shop

Integration of computers in the manufacturing process has rightfully emphasized their use in electronically conveying complex product geometry from engineering design and drafting to the design of manufacturing fixtures and part programming. The relative absence of literature and software relating to the use of micro-computers in the Experimental (prototype) Shop suggests that at best, their usage is limited and at worst, not amenable to very small lot size production quantities.

Experience with a trial program suggests the contrary. While the project described in this paper is far from a full implementation, early results suggest that micro-computers can be effectively use to:

1. 1) Improve communications between the designer and the shop.

2. 2) Assist the shop in purchasing, process planning, and control of spare part inventories.

Also included in the paper is an overview of the software as contrasted with conventional high volume production planning and inventory control systems to emphasize the fundamental differences in functional usage. The paper concludes with a discussion of future extensions to provide networking and graphic capabilities that shows promise of improving the feedback loop to Engineering Design and Manufacturing.     

An optimal gas-fired heating system

Utilizing a prescribed system configuration, this paper discusses the mathematical models of the system components used and formulates a method for controlling a domestic heating system in accordance to a prescribed criterion. The optimal problem treated is one of reducing the room temperature deviation from a prescribed reference value to zero, while at the same time minimizing the value of some predetermined performance or cost functional J. The development proceeds in essentially five steps.

1. (a) The development of the mathematical models for each of the elements of the heating system;

2. (b) Combining the mathematical models into a form which is suitable for the application of optimization techniques;

3. (c) Defining an optimization criterion which incorporates the main objective for minimizing room temperature variations with respect to a prescribed reference temperature;

4. (d) Choosing the optimization technique best suited for the problem;

5. (e) Constructing an optimal control system employing the optimization technique developed.

A numerical example compares the performance of the optimal system with a system of the conventional type which can be found in many American homes.     

A note on the combinatorial structure of the visibility graph in simple polygons

Combinatorial structure of visibility is probably one of the most fascinating and interesting areas of engineering and computer science. The usefulness of visibility graphs in computational geometry and robotic navigation problems like motion planning, unknown-terrain learning, shortest-path planning, etc., cannot be overstressed. The visibility graph, apart from being an important data structure for storing and updating geometric information, is a valuable mathematical tool in probing and understanding the nature of shapes of polygonal and polyhedral objects. In this research we wish to initially focus our attention on a fundamental class of geometric objects. These geometric objects may be looked upon as building blocks for more complex geometric objects, and which offer an ideal balance between complexity and simplicity, namely simple polygons.

A major theme of the proposed paper is the investigation of the combinatorial structure of the visibility graph. More importantly, the goals of this paper are:

1. (i) To characterize the visibility graphs of simple polygons by obtaining necessary and sufficient conditions a graph must satisfy to qualify for the visibility graph of a simple polygon

2. (ii) To obtain hierarchical relationships between visibility graphs of simple polygons of a given number of vertices by treating them as representing simple polygons that are deformations of one another.

3. (iii) To exploit the potential of complete graphs to be natural coordinate systems for addressing the problem of reconstructing a simple polygon from visibility graph.

We intend to achieve this by defining appropriate “betweenness” relationships on points with respect to the edges of the complete graphs.     

Fuzzy multiple attributes and multiple hierarchical decision making

A procedure is proposed to solve the multiple attributes and multiple hierarchical system under fuzzy environment. The approach is based on:

1. (1) fuzzy representation;

2. (2) hierarchical performance evaluation structure,

3. (3) gradient eigenvector method for rating the fuzzy criteria weighting, and

4. (4) using the max-min paired elimination method for aggregation.

To illustrate the approach, an example on the evaluation of teaching performance in higher education is solved.     

Simulation-based planning and control: From shop floor to top floor

This paper illustrates how simulation-based shop-floor planning and control can be extended to enterprise-level activities (top floor). First, the general planning and control concept are discussed, followed by an overview of simulation-based shop-floor planning and control. Analogies between the shop floor and top floor are discussed in terms of the components required to construct simulation-based planning and control systems. Analogies are developed for resource models, coordination models, physical entities, and simulation models. Differences between the shop floor and top floor are also discussed in order to identify new challenges faced for top-floor planning and control. A major difference between the top floor and the shop floor is the way a simulation model is constructed for use in planning, depending on whether time synchronization among member simulations becomes an issue or not. Another difference is in the distributed communication/computing platform. This work uses a distributed computing platform using Web services technology to integrate heterogeneous simulations and systems in a distributed top-floor control environment. The research results reveal that simulation-based planning and control is extensible to the top-floor environment’s evolving new research challenges.     

Database considerations in manufacturing systems integration

This paper deals with ideas that could form a basis for manufacturing integration. In recent times more attention is being paid to the idea of applying artificial intelligence (AI) techniques to manufacturing. However, very little attention is being paid to the proper use of these techniques. This research work explores three basic ideas:

1. 1. Applications of the entity-relationship approach to knowledge representation.

2. 2. The basic philosophy of expert database systems and

3. 3. Integration of manufacturing systems from the above two concepts.

The approaches for 1 and 2 are explained with actual implementation experiences, while a framework for integration is proposed from a more philosophical perspective.     

Discrete warehouse problem

A discrete warehouse is a collection of two-dimensional unit-square objects (robot and obstacles), which are allowed to move horizontally and vertically along grid lines. In this paper, we consider motion planning problems in a discrete warehouse with movable obstacles. In such a setup one is allowed to move some of the obstacles in order to:

1. (1) navigate the robot between an initial and a final position of the warehouse, and

2. (2) construct a clearing (path) between two specified points.

The final positions of the obstacles are unimportant for our problems.

We consider two forms of obstacle manipulations:

1. (a) remote, when the obstacles are moved by a remote mechanism, and

2. (b) contact, when the obstacles are moved only by direct contact of the robot.

We present necessary and sufficient conditions for the existence of a motion in both cases, and propose efficient algorithms for constructing feasible motions.     

A survey of simple transfer-function derivations from high-order state-variable models

The problem of the derivation of simple transfer function models from high order state variable models is reviewed. Methods of reduction are classified according to whether they involve

1. (a) the computation of the time or frequency responses

2. (b) the derivation, as an intermediate step, of a transfer function which is the ratio of two polynomials, the denominator being of the same order as the state variable model, or

3. (c) a set of characterising functions.

Particular reduction methods considered are those based on fitting the step or frequency responses, on determining the intermediate, high order transfer function and reducing it by continued fraction expansion and on fitting the moments of the impulse response. An example illustrating these methods is given. The form of the simple model, the criteria of goodness of fit and the practical difficulties involved in the use of these methods are discussed.     

iCoSim-FMS: An intelligent co-simulator for the adaptive control of complex flexible manufacturing systems

We describe an intelligent co-simulator for real time production control of a complex flexible manufacturing system (CFMS) having machine and tool flexibility. The manufacturing processes associated with the CFMS are complicated with each operation being possibly done by several machining centers. The co-simulator design approach is built upon the theory of dynamic meta-model based supervisory control with the cooperation of its own embedded intelligent blocks. The system is implemented by coupling of the centralized simulation controller (CSC) and real-time simulator for enforcing dynamic strategies of shop floor control. The posteriori adaptive co-simulator is equipped with a concurrent bilateral mechanism for simulation optimization based on appropriate control rules enhancing performance criteria simulation efficiency. A working intelligent adaptive controller prototype (iCoSim-FMS) has been developed to validate the proposed approach and compare its performance with well known FMS heuristic methods.     

Verification in loosely synchronous queue-connected discrete timed automata

We look at a model of a queue system that consists of the following components:

1. Two discrete timed automata W (the “writer”) and R (“the reader”).

2. One unrestricted queue that can be used to send messages from W to R. There is no bound on the length of the queue.

W and R do not share a global clock and operate in a loosely synchronous way. That is, the absolute value of the difference between the local time of W and the local time of R is always bounded by a positive constant. We show that the binary reachability for these systems is effectively computable, and this result is generalized to the case when there are two queues (one from W to R and the other from R to W) that operate in half-duplex. We then present some properties (e.g., safety, invariance, etc.) that can be verified for loosely synchronous queue-connected discrete timed automata and give an example of a system composed of a sensor and a controller that is verifiable using our results.     

Impact of personality and intelligence on job satisfaction of assembly line and bench work - an industrial study

A study of the impact of machine-paced (M/P) and self-paced (S/P) work on job satisfaction of 28 female industrial assembly workers was evaluated in which M/P work was confounded with simplified work and the S/P job was confounded with enriched tasks. Results indicated the following:

1. 1. Over three-quarters of workers were more satisfied in S/P jobs, while only less than one-quarter were more satisfied in M/P jobs.

2. 2. The 16PF personality test effectively predicts (0·88 multiple correlation) the satisfaction ratios of M/P to S/P jobs.

Observer-based multivariable flatness control of a cold rolling mill

The synthesis methodology developed by Kimura (1985) based on the design theory of output regulators essentially due to Wonham (1974) has been applied successfully to the flatness control system for a 6-high cold rolling mill. The system has the following remarkable features.

1. (1) The structure of the controller is simple. This makes it easy to tune the control system.

2. (2) The controller copes well with the detection time delay, and thus high performance is obtained even at a low rolling speed.

3. (3) The flatness error caused by the rolling force variation in mill acceleration and deceleration time would be kept to a minimum by the function to adjust roll bending force using the signal of rolling force.

A knowledge-based system for reactive scheduling decision-making in FMS

This paper describes research into the development of an intelligent simulation environment. The environment was used to analyze reactive scheduling scenarios in a specific flexible manufacturing systems (FMS) configuration. Using data from a real FMS, simulation models were created to study the reactive scheduling problem and this work led to the concept of capturing instantaneous FMS status data as snapshot data for analysis. Various intelligent systems were developed and tested to asses their decision-making capabilities. The concepts of History Logging and expert system learning is proposed and these ideas are implemented into the environment to provide decision-making and control across a FMS schedule lifetime. This research proposes an approach for the analysis of reactive scheduling in an FMS. The approach and system that was subsequently developed was based on the principle of automated intelligent decision-making via knowledge elicitation from FMS status data, together with knowledge base augmentation to facilitate a learning ability based on past experiences.     

An analysis of research topics in software engineering – 2006

This paper is the first in a new annual series whose goal is to answer the following question: what are the active research focuses within the field of software engineering? We considered 7 top journals and 7 top international conferences in software engineering and examined all the 691 papers published in these journals or presented at these conferences in 2006. Consequently, we have a number of findings.

(1) Seventy-three percent of journal papers focus on 20% of subject indexes in software engineering, including Testing and Debugging (D.2.5), Management (D.2.9), and Software/Program Verification (D.2.4).

(2) Eighty-nine percent of conference papers focus on 20% of subject indexes in software engineering, including Software/Program Verification (D.2.4), Testing and Debugging (D.2.5), and Design Tools and Techniques (D.2.2).

(3) Seventy-seven percent of journal/conference papers focus on 20% of subject indexes in software engineering, including Testing and Debugging (D.2.5), Software/Program Verification (D.2.4), and Management (D.2.9).

(4) The average number of references cited by a journal paper is about 33, whereas this number becomes around 24 for a conference paper.

A featured-based dynamic process planning and scheduling

The paper presents a dynamic featured-based process planning and scheduling system which is currently under development utilizing a commercial CAD system.

In this system, the product features are extracted using an AI-based feature extractor according to the shop floor capabilities. Using this system, the products can be dynamically process planned and scheduled.     

The monadic second-order logic of graphs X: Linear orderings

Graphs are finite and handled as relational structures. We give some answers to the following general questions:

1. (1) For which classes of graphs is it possible to specify a linear ordering of the set of vertices of each graph of by fixed monadic second-order formulas?

2. (2) For which classes of graphs does there exist an extension of monadic second-order logic such that a subclass L of is recognizable if and only if it is the class of graphs in that satisfy a formula of ? (In this paper, recognizability is understood in an algebraic sense, relative to a finite set of graph operations and basic graphs that generate all graphs of .)

3. (3) For which classes of graphs is it possible to construct, in every graph of the class, and by fixed formulas of a suitable extension of monadic second-order logic, its hierarchichal structure, i.e., a finite term written with the operations and basic graphs of (2), that defines the considered graph?

Applications concern dependency graphs of partially commutative words, partial k-paths, cographs, and graphs, the modular decomposition of which uses prime graphs of bounded size.     

The design of an automated material handling system for a job shop

This paper describes the application of techniques developed for the management and control of Flexible Manufacturing Systems (FMS's) to a traditional job shop manufacturing sheet metal parts on typical sheet fabricating machines. The problem was the design and evaluation of an automated material handling subsystem (MHS) to support the shop. The MHS controlled the shop loading and floor control by its choice of orders to transport and enter the shop. Detailed simulation models were used to simulate the existing shop, the shop with a MHS, and several algorithms for loading and sequencing orders through the shop. This paper describes the shop, the models developed, the algorithms tested, and the simulation results. A highlight of the study was the ease and speed with which multiple models were developed using an interactive simulation generator, CAPS. Of particular interest is the procedure for shop scheduling, downstream pull, which uses heavily loaded machines to provide sequencing alternatives with the objective of “pulling” work through them to reach more lightly loaded machines. Shop output was estimated to increase from 26 orders per day to 45, a 73% increase, and turnaround time to decrease from ten days to two days.     

Applications of power series in computational geometry

A number of algorithms are presented for obtaining power series expansions of curves and surfaces at a point. Some results on the radius of convergence are given. Two applications of series are given:

1. • for curve tracing algorithms, where a truncated series is used to approximate the curve of intersection of two surfaces

2. • to define nth degree geometric continuity, for arbitrary

A global parametrization of asymptotically stable linear systems

In this paper we construct a homeomorphism from the set of p × m transfer functions of McMillan degree n onto the open subspace of asymptotically stable linear systems. This homeomorphism yields a one-to-one correspondence between

1. (i) canonical forms for state space equivalence of minimal systems and

2. (ii) canonical forms for state space equivalence of asymptotically stable minimal systems.

Implications for the topology of various sets of asymptotically stable systems are given.     

DPP: An agent-based approach for distributed process planning

A changing shop floor environment characterized by larger variety of products in smaller batch sizes requires creating an intelligent and dynamic process planning system that is responsive and adaptive to the rapid adjustment of production capacity and functionality. In response to the requirement, this research proposes a new methodology of distributed process planning (DPP). The primary focus of this paper is on the architecture of the new process planning approach, using multi-agent negotiation and cooperation. The secondary focus is on the other supporting technologies such as machining feature-based planning and function block-based control. Different from traditional methods, the proposed approach uses two-level decision-making—supervisory planning and operation planning. The former focuses on product data analysis, machine selection, and machining sequence planning, while the latter considers the detailed working steps of the machining operations inside of each process plan and is accomplished by intelligent NC controllers. By the nature of decentralization, the DPP shows promise of improving system performance within the continually changing shop floor environment.