Results 1 - 10
of
28
Scheduling as a Fuzzy Multiple Criteria Optimization Problem
, 1994
"... Real-world scheduling is decision making under vague constraints of different importance, often using uncertain data, where compromises between antagonistic criteria are allowed. We explain in theory and by detailed examples a new combination of fuzzy set based constraints and repair based heuristi ..."
Abstract
-
Cited by 44 (12 self)
- Add to MetaCart
Real-world scheduling is decision making under vague constraints of different importance, often using uncertain data, where compromises between antagonistic criteria are allowed. We explain in theory and by detailed examples a new combination of fuzzy set based constraints and repair based heuristics that help to model these scheduling problems. We simplify the mathematics needed for a method of eliciting the criteria's importances from human experts. We introduce a new consistency test for configuration changes. This test also helps to evaluate the sensitivity to configuration changes. We describe the implementation of these concepts in our fuzzy constraint library ConFLIP++ and in our heuristic repair library D'ej`aVu. Finally, we present results from scheduling a continuous caster unit in a steel plant.
Recent developments in evolutionary computation for manufacturing optimization: Problems, solutions, and comparisons
- IEE Transactions on Evolutionary Computation
"... Abstract—The use of intelligent techniques in the manufacturing field has been growing the last decades due to the fact that most manufacturing optimization problems are combinatorial and NP hard. This paper examines recent developments in the field of evolutionary computation for manufacturing opti ..."
Abstract
-
Cited by 24 (1 self)
- Add to MetaCart
(Show Context)
Abstract—The use of intelligent techniques in the manufacturing field has been growing the last decades due to the fact that most manufacturing optimization problems are combinatorial and NP hard. This paper examines recent developments in the field of evolutionary computation for manufacturing optimization. Significant papers in various areas are highlighted, and comparisons of results are given wherever data are available. A wide range of problems is covered, from job shop and flow shop scheduling, to process planning and assembly line balancing. Index Terms—Assembly lines, cellular manufacturing, design, evolutionary computation, genetic algorithms, manufacturing optimization, process planning, scheduling. I.
Iterative Improvement Methods for Knowledge-based Scheduling
- AI COMMUNICATIONS
, 1995
"... For large industrial applications the constraint-based formulation of scheduling problems fits better than mathematical representations from Operational Research, because the constraint approach is more flexible and can be adapted more easily to organizational changes in the production. However, ..."
Abstract
-
Cited by 14 (7 self)
- Add to MetaCart
For large industrial applications the constraint-based formulation of scheduling problems fits better than mathematical representations from Operational Research, because the constraint approach is more flexible and can be adapted more easily to organizational changes in the production. However, the search for a good solution for realistic applications can be very expensive and furthermore, in scheduling one is not only interested in a feasible solution but also in an optimized solution. In this paper I present iterative improvement methods that can be used to optimize a schedule that is represented by constraints. These methods start with any schedule and try to optimize it by iterative modifications. The goal of the optimization method may be a minimization of the number of constraint violations or a maximization of a function that aggregates the satisfaction degrees of all involved soft constraints. Additionally, consistency techniques for constraints can be used to che...
Time Reasoning for a Collaborative Planning Agent in a Dynamic Environment
, 2001
"... We present a temporal reasoning mechanism for an individual agent who is situated in a dynamic environment such as the web and collaborates with other agents while interleaving planning and acting. Building a collaborative agent that can flexibly achieve its goals in changing environments requires a ..."
Abstract
-
Cited by 8 (6 self)
- Add to MetaCart
We present a temporal reasoning mechanism for an individual agent who is situated in a dynamic environment such as the web and collaborates with other agents while interleaving planning and acting. Building a collaborative agent that can flexibly achieve its goals in changing environments requires a blending of real-time computing and AI technologies. Therefore, our mechanism consists of an Artificial Intelligence (AI) subsystem and a Real-Time (RT) subsystem. The AI subsystem is based on a model for collaborative planning. The RT subsystem receives a dynamic task set associated
Co-Operating Scheduling Systems Communicating through Fuzzy Sets
- PREPRINTS OF THE 2 ND IFAC/IFIP/IFORS-WORKSHOP ON INTELLIGENT MANUFACTURING SYSTEMS (IMS'94
, 1994
"... A communication procedure for communicating scheduling expert systems based on fuzzy set theory is proposed. Fuzzy sets are used to express and to exchange constraints and their possible relaxations with other scheduling systems that can interpret these constraints. The procedure is intended to ..."
Abstract
-
Cited by 7 (4 self)
- Add to MetaCart
A communication procedure for communicating scheduling expert systems based on fuzzy set theory is proposed. Fuzzy sets are used to express and to exchange constraints and their possible relaxations with other scheduling systems that can interpret these constraints. The procedure is intended to optimize the global evaluation among the communicating systems. An example from steel industry is taken to illustrate the approach. Here, a scheduling system of the steel making shop and that of the rolling mill try to optimize the global costs by optimizing their own schedules under the observation of the other systems constraints.
Utility and Stability Measures for Agent-Based Dynamic Scheduling of Steel Continuous Casting
- Proceedings of the IEEE International Conference on Robotics and Automation, Taiwan ; 2003
, 2003
"... This paper describes a new model for robust predictive/reactive scheduling of steel continuous casting based on the use of multi-agents, tabu search and heuristic approaches. A continuous caster agent generates a predictive production schedule taking into account manufacturing requirements and local ..."
Abstract
-
Cited by 6 (1 self)
- Add to MetaCart
(Show Context)
This paper describes a new model for robust predictive/reactive scheduling of steel continuous casting based on the use of multi-agents, tabu search and heuristic approaches. A continuous caster agent generates a predictive production schedule taking into account manufacturing requirements and local constraints using tabu search. The predictive schedule is modified so as to minimise deviation between the performance measure values of the realised and predictive schedules in order to react to real-time events. We propose several schedule-repair and complete reschedule strategies to handle the real-time events, evaluate and compare their performance. The decision as to whether to locally repair the schedule or reschedule from scratch (complete reschedule) is based on three measures: robustness, utility and stability. Utility measures the change in schedule objective following schedule revision. Stability measures the deviation from the original schedule caused by schedule revision to quantify the undesirability of making large changes to the initial predictive schedule unless absolutely necessary. Robustness combines the utility and stability measures. In order to investigate the performance of these measures and strategies, simulation experiments were carried out and results are reported.
DÉJÀ VU -- A Reusable Framework for the Construction of Intelligent Interactive Schedulers
- OF INTELLIGENT INTERACTIVE SCHEDULERS, ADVANCES IN PRODUCTION MANAGEMENT SYSTEMS, OKINO
, 1998
"... We describe the basic techniques underlying the DÉJÀ VU Scheduling Class Library to achieve a library of reusable and extendible classes for the construction of interactive production scheduling systems. The constructed systems shall be efficient and user centered which means that the user shall hav ..."
Abstract
-
Cited by 6 (3 self)
- Add to MetaCart
We describe the basic techniques underlying the DÉJÀ VU Scheduling Class Library to achieve a library of reusable and extendible classes for the construction of interactive production scheduling systems. The constructed systems shall be efficient and user centered which means that the user shall have full control over the schedule construction process. Mixed-initiative scheduling shall be possible. We present how scheduling objects and constraints on these objects are realized. Further we describe the potential user interactions with the system and show prototypical examples from the graphical user interface. A first scheduling system was developed with this class library for the steel plant of Bhler in Kapfenberg. We demonstrate which extensions we made for this system.
Case-based Reactive Scheduling
- ARTIFICIAL INTELLIGENCE IN REACTIVE SCHEDULING
, 1995
"... Scheduling of operations in a production process is usually seen as a combinatorial search for a feasible and perhaps optimal plan. In actual industrial practice however, constraints and optimization criteria can often not be given exactly because they are unknown or vague. Therefore a combinato ..."
Abstract
-
Cited by 5 (1 self)
- Add to MetaCart
Scheduling of operations in a production process is usually seen as a combinatorial search for a feasible and perhaps optimal plan. In actual industrial practice however, constraints and optimization criteria can often not be given exactly because they are unknown or vague. Therefore a combinatorial approach often does not meet the actual requirements. Furthermore, the representation of all potential alternatives of the production process would lead to a combinatorial explosion that cannot be solved in a reasonable time frame. In this paper case-based reasoning is applied to reactive scheduling to model the experience of skilled human operators in reacting to unforeseen events in the production process. Old solutions stored in a case base are used to solve new problems. Case-based reasoning is supported by fuzzy reasoning on a constraint-based representation to find and adapt old cases and to evaluate them. An iterative improvement method is further used to optimize solutions found by case-based reasoning. The approach is illustrated by means of an application in the steel industry.
Robust Processor Allocation for Independent Tasks When Dollar Cost for Processors is a Constraint
"... In a distributed heterogeneous computing system, the resources have different capabilities and tasks have different requirements. Different classes of machines used in such systems typically vary in dollar cost based on their computing efficiencies. Makespan (defined as the completion time for an en ..."
Abstract
-
Cited by 4 (0 self)
- Add to MetaCart
(Show Context)
In a distributed heterogeneous computing system, the resources have different capabilities and tasks have different requirements. Different classes of machines used in such systems typically vary in dollar cost based on their computing efficiencies. Makespan (defined as the completion time for an entire set of tasks) is often the performance feature that is optimized. Resource allocation is often done based on estimates of the computation time of each task on each class of machines. Hence, it is important that makespan be robust against errors in computation time estimates. The dollar cost to purchase the machines for use can be a constraint such that only a subset of the machines available can be purchased. The goal of this study is to: (1) select a subset of all the machines available so that the cost constraint for the machines is satisfied, and (2) find a static mapping of tasks so that the robustness of the desired system feature, makespan, is maximized against the errors in task execution time estimates. Six heuristic techniques to this problem are presented and evaluated.
Temporal Reasoning for a Collaborative Planning Agent in a Dynamic Environment
, 2002
"... We present a temporal reasoning mechanism for an individual agent situated in a dynamic environment such as the web and collaborating with other agents while interleaving planning and acting. Building a collaborative agent that can flexibly achieve its goals in changing environments requires a bl ..."
Abstract
-
Cited by 2 (0 self)
- Add to MetaCart
(Show Context)
We present a temporal reasoning mechanism for an individual agent situated in a dynamic environment such as the web and collaborating with other agents while interleaving planning and acting. Building a collaborative agent that can flexibly achieve its goals in changing environments requires a blending of real-time computing and AI technologies. Therefore, our mechanism consists of an Artificial Intelligence (AI) planning
