H.Y.K. Lau

Object-oriented specification of automated manufacturing systems

Abstract The design of automated manufacturing systems (AMSs) requires an effective system specification that helps designers to deal with the changes in system requirements. This paper presents an object-oriented rule-based methodology for the specification of AMSs, which extends the capability of the existing object-oriented specification methods to support system integration and the explicit representation of control policies. The methodology is characterised by the use of rule-based modelling techniques to specify object behaviours in terms of processes. The application of the methodology is illustrated by the specification of a flexible manufacturing system.

MIP-based heuristics for solving robust gate assignment problems

We transit the quadratic objective function to an equivalent linear one.The first one to adapt general MIP solving methods to solve GAP.Propose four methods for solving GAP.Relationship between different objectives is analyzed. This paper considers the problem of robust gate assignment. Three factors having significant impact on gate assignment are considered: schedule robustness, facility and personnel cost during tows, and passenger satisfaction level. To precisely evaluate passenger satisfaction level, especially for transfer passengers, a model with quadratic terms is formulated. The quadratic model can exactly represent the traveling distance of transfer passengers, which cannot be precisely considered by traditional approximate models. However, the quadratic model is rather difficult to solve. Therefore, we then transform the model to an equivalent MIP model which is proven to be more efficient than the linearized models proposed in previous literature. In addition, in order to handle large size instances, we developed four different algorithms including diving, local branching, and relaxation induced neighborhoods (RINS), which are popular algorithms for solving general MIP models, together with a new algorithm which hybridizes the strength of RINS and diving. Extensive experiments are performed to compare the performance of the proposed algorithms.

An object-oriented prototyping tool for automated manufacturing systems

Abstract System prototyping is essential in the development of automated manufacturing systems (AMSs), and the value of prototyping depends largely on the effectiveness of the prototyping tool to represent a system design and also the prototyping results. This paper presents a windows-based prototyping tool that adopts a frame-based representation approach to build a prototype from an object-oriented system design specification. The tool provides a platform capable of executing the prototype under different constraints and operating conditions, and of presenting the prototyping results to facilitate the study of the behaviour of the AMS. Properties, such as the total cycle time, resource utilisation, potential conflicts, errors in design, and abnormal behaviours, can be readily derived. The tools effectiveness is illustrated by prototyping a flexible manufacturing system, and examining the results obtained. Indeed, the prototyping tool proposed in this paper is shown to provide a convenient means for the design of AMSs.

A two stage heuristic algorithm for the integrated aircraft and crew schedule recovery problems

We propose a new heuristic algorithm for the integrated aircraft and crew schedule recovery problem.We propose a new model for the integrated aircraft and flight recovery problem.We propose a new model for the crew schedule recovery problem.Three sets of disruption scenarios are simulated to test algorithms performance. Airline disruptions incurred huge cost for airlines and serious inconvenience for travelers. In this paper, we study the integrated aircraft and crew schedule recovery problem. A two stage heuristic algorithm for the integrated recovery problem is proposed. In the first stage, the integrated aircraft recovery and flight-rescheduling model with partial crew consideration is built. This model is based on the traditional multi-commodity network model for the aircraft schedule recovery problem. The objective of this model also includes minimization of the original crew connection disruption. In the second stage, the integrated crew schedule recovery and flight re-scheduling model with partial aircraft consideration is built. We proposed a new multi-commodity model for the crew schedule recovery. The main advantage of such model is that it is much more efficient to integrate the flight-scheduling and aircraft consideration. New constraints are incorporated to guarantee that the aircraft connections generated in the stage 1 are still feasible. Two stages are run iteratively until no improvement can be achieved. Experimental results show that our method can provide better recovery solutions compared with the benchmark algorithms.

An integrated flight scheduling and fleet assignment method based on a discrete choice model

We propose a new integrated flight scheduling and fleet assignment method using the discrete choice model.We extend the model to consider itinerary price elasticity.A heuristic algorithm is proposed to solve models.We simulate a micro-market to evaluate the performance of our method. The airline industry is capital intensive and operates on a thin profit margin. Optimal and flexible flight schedule is essential for airlines to survive in such competitive market. In this study, we focus on the integrated flight scheduling and fleet assignment problem based on a discrete choice model. Two mixed integer programming models are proposed: the first model solves the integrated flight scheduling and fleet assignment problem and the second model further considers the itinerary price elasticity. A heuristic algorithm is also proposed to efficiently solve the second model. In numerical studies, a micro market is simulated to evaluate the performance of our proposed models and algorithms. Experimental results reveal that our models can achieve a significant profit improvement under a reasonable computation time.

An object-oriented rule-based framework for the specification of flexible manufacturing systems

The design of flexible manufacturing systems (FMSs) requires an effective system specification method, which is flexible to cope with redesigns as a result of requirement changes. In order to facilitate the design of such systems, object-oriented methods are increasingly adopted. However, they only provide limited support to system integration and the explicit specification of operational policies. In this connection, an object-oriented rule-based specification framework is proposed to incorporate a rule model into an object-oriented specification, to analyze and design the global processes and operational policies of FMSs. The application of this framework is illustrated via the specification of a typical vehicle-based FMS.

An object-oriented model for the specification of manufacturing systems

The design of advanced manufacturing systems entails a high flexibility in the system specification method, to allow for flexibility and efficiency in coping with the frequent design modifications. Object-oriented specification methods possess the necessary expressiveness and extensibility to allow for such flexibility. In order to obtain a declarative representation of the knowledge of objects, the semantic data model of the frame-based representation method is incorporated. This extended object-oriented model can be used for specifying system behaviors. Within this model, generic object types representing general concepts in manufacturing systems are identified. These generic object types can facilitate the specification of manufacturing systems by means of an object-oriented approach. The application of the model for system specification is illustrated with reference to a typical robotic FMC.

Object-oriented technologies for automated manufacturing systems development

The study presents a detailed survey on the current state-of-the-art object-oriented methodologies and representation methods in the development of complex automated manufacturing systems (AMSs). The study focuses on the suitability and usability of these methodologies, with a view to solving the complex problem of system analysis and design by modelling and prototyping. The results obtained from this study are expected to facilitate the appropriate selection of object-oriented techniques for the development of AMSs, and also to provide guidance to system engineers that adopt object-orientation as a tool for building manufacturing systems.

A unified framework for the quality management of manufacturing systems software development

Software has become a principal component in todays advanced automated manufacturing systems. The ability to deliver software which satisfies the original requirements and expectations within budgeted time and cost is one of the major factors in determining the success of the project. While existing software engineering techniques are available for the effective design of complex software systems, much of the effort relies on a designers experience and intuition. The paper presents a unified framework that aims to quantify the software development process and to assist engineers to manage the development process such that not only the quality of the software produced is assured, but also is the development process. We illustrate the application of the framework for software development of a robotic Flexible Manufacturing Cell (FMC).