Coordination Approaches and Systems – Part II: An Operational Perspective

This is the second of two papers surveying research in coordination approaches and systems. This paper is concerned with operational coordination, which is aimed at coordinating activities such that the design process can be performed in a near optimal manner with respect to time, and the allocation and utilisation of resources. Aspects of coordination categorised as operational include resource management, scheduling and planning. The first of these two papers presents a review of coordination from a strategic perspective, which is concerned with the decision management aspects of coordination. Greater emphasis is now being placed on the significance of organising the design process as this affects time to market, product quality, cost, and consequently product success. The aim of this paper is to present a fundamental review of operational coordination approaches and systems. The 1990s has seen much progress being made towards a greater understanding and appreciation of coordination in various disciplines through the development of a wide range of approaches and systems. However, there remains a requirement to formally identify the key issues involved in coordination such that a widely accepted representation can be agreed upon. Consequently, research should continue to be supported in the exploration for a unified approach to coordination which will permit a broader and greater understanding of those aspects involved.     

Schedulability issues for EDZL scheduling on real-time multiprocessor systems

EDZL (Earliest Deadline first until Zero Laxity) is an efficient and practical scheduling algorithm on multiprocessor systems. It has a comparable number of context switch to EDF (Earliest Deadline First) and its schedulable utilization seems to be higher than that of EDF. Previously, there was a conjecture that the utilization bound of EDZL is 3m/4=0.75m for m processors. In this paper, we disprove this conjecture and show that the utilization bound of EDZL is no greater than m(1−1/e)≈0.6321m, where e≈2.718 is the Euler's number.     

Multi-machine earliness and tardiness scheduling problem: an interconnected neural network approach

This paper addresses the problem of scheduling a set of independent jobs with sequence-dependent setups and distinct due dates on non-uniform multi-machines to minimize the total weighted earliness and tardiness, and explores the use of artificial neural networks as a valid alternative to the traditional scheduling approaches. The objective is to propose a dynamical gradient neural network, which employs a penalty function approach with time varying coefficients for the solution of the problem which is known to be NP-hard. After the appropriate energy function was constructed, the dynamics are defined by steepest gradient descent on the energy function. The proposed neural network system is composed of two maximum neural networks, three piecewise linear and one log-sigmoid network all of which interact with each other. The motivation for using maximum networks is to reduce the network complexity and to obtain a simplified energy function. To overcome the tradeoff problem encountered in using the penalty function approach, a time varying penalty coefficient methodology is proposed to be used during simulation experiments. Simulation results of the proposed approach on a scheduling problem indicate that the proposed coupled network yields an optimal solution which makes it attractive for applications of larger sized problems.     

SS/TDMA time-slot assignment with knowledge-base and prolog implementation

A software production system for the generation of time slot assignment plans for SS/TDMA systems is proposed and implemented. The approach used in this system conveniently combines algorithms derived for ideal configurations with heuristic procedures that are needed to account for conditions present in real systems. Algorithms that produce plans with a minimum number of switchings and minimum traffic transmission duration can now be easily implemented. The assignment plans obtained are as efficient as those previously reported when the assumptions are the same. The proposed production system, however is capable of handling a much larger variety of constraints and heuristic procedures for which no efficient solutions have been reported.     

Multiprocessor scheduling with communication delays

This paper adresses certain types of scheduling problems that arise when a parallel computation is to be executed on a multiprocessor. We define a model that allows for communication delays between precedence-related tasks, and propose a classification of various submodels. We also review complexity results and optimization and approximation algorithms that have been presented in the literature.     

Integrating scheduling and control functions in computer integrated manufacturing using artificial intelligence

Proper integration of scheduling and control in Flexible Manufacturing Systems will make available the required level of decision-making capacity to provide a flexibly-automated, efficient, and quality manufacturing process. To achieve this level of integration, the developments in computer technology and sophisticated techniques of artificial intelligence (AI) should be applied to such FMS functions as scheduling. In this paper, we present an Intelligent Scheduling System for FMS under development that makes use of the integration of two AI technologies. These two AI technologies — Neural Networks and Expert Systems — provide the intelligence that the scheduling function requires in order to generate goodschedules within the restrictions imposed by real-time problems. Because the system has the ability to plan ahead and learn, it has a higher probability of success than conventional approaches. The adaptive behavior that will be achieved contribute to the integration of scheduling and control in FMS.     

Scheduling and sequencing of rubber compounds on banbury mixers in a tyre company

Scheduling and sequencing compounds on banbury mixers is a daily production planning function in a tyre company. The current scheduling procedures are based on experience. A number of factors, such as, capacity, cost, time, speed, set-up of mixers, compound changeovers, density and demand of compound, have to be considered during planning. In this paper, we propose a two-stage approach to this problem. This approach can be easily computerised to aid the personnel in the planning function. An example, considering actual data obtained from the company, is used to illustrate the approach. The current scheduling practice by company personnel, as inferred from past record, is also reported.     

基于自适应遗传算法的航材动态调度规划研究

针对民机不同维修任务的航材调度规划问题进行了深入研究,提出了基于改进自适应遗传算法动态库存的航材实时共享调度规划模型。结合任务时间窗的需求和停机惩罚函数为约束,以最小总成本为优化目标,建立了航材库动态环境下的航材调度模型。在此基础上,采用改进遗传算法对模型进行求解,编码方式采用染色体组的形式,在求解过程中,将交叉和变异概率根据适应值作出动态调整。通过算例仿真验证了该模型的可行性和有效性,为航材实时调度规划提供了理论方法依据。     

Grid emulation for managing random sensor networks

A common assumption in sensor networks is that sensors are located according to a uniform random distribution. In this paper, we show that uniform random points on the two dimensional unit square are almost a “grid”. In particular, for a synchronous geographic sensor network we show how to emulate any grid protocol on random sensor networks, with high probability.This suggests the following framework. In order to solve a problem on a random sensor network, we solve the same problem on a grid. Then we use our emulation to make the obtained solution suitable for random sensor network. We analyze the cost of the emulation in terms of consumed energy and time. Finally, we provide some examples that illustrate our method.     

Construction Productivity Improvement

Construction productivity has been on the decline in the last decade. The results are presented on a survey of the Engineering News‐Record 400 largest contractors to obtain their views on where productivity improvements would most help and to compare the trends with a similar survey carried out in 1979. Data were collected on the general company characteristics of the responding contractors, and on the contractors' opinions on potential areas for productivity improvement in the office and in the field. Findings indicate that immediate research should concentrate on improving marketing practices, planning and scheduling, labor‐management relations, site supervision, industrialized building systems, equipment policy and engineering design; and that governmental regulations have lost the immediate urgency attached to them in 1979.It is also recommended that similar surveys be conducted every 3 to 4 years to identify new trends and to steer research in the appropriate direction.