A tabu search procedure for developing robust predicitive project schedules.

Proactive scheduling aims at the generation of robust baseline schedules that are as much as possible protected against disruptions that may occur during project execution. In this paper, we focus on disruptions caused by stochastic resource availabilities and aim at generating stable baseline schedules. A schedule’s robustness (stability) is measured by the weighted deviation between the planned and the actually realized activity starting times during project execution. We present a tabu search procedure that operates on a surrogate, free slack based objective function. Its effectiveness is demonstrated by extensive computational results obtained on a set of randomly generated test instances.Project scheduling; Robustness; Proactive; Stability;

A tabu search procedure for generating robust project baseline schedules under stochastic resource availabilities.

The majority of research efforts in project scheduling assume a static and deterministic environment with complete information. In practice, however, these assumptions will hardly, if ever, be satisfied. Proactive scheduling aims at the generation of robust baseline schedules that are as much as possible protected against anticipated disruptions that may occur during project execution. In this paper, we focus on disruptions that may be caused by stochastic resource availabilities and aim at generating stable baseline schedules, where the solution robustness (stability) of the baseline schedule is measured by the weighted deviation between the planned and the actually realized activity starting times during project execution. We present a tabu search procedure that operates on a surrogate free slack based objective function. The effectiveness of the procedure is demonstrated by extensive computational results obtained on a set of randomly generated test instances.

Project scheduling under undertainty – survey and research potentials.

The vast majority of the research efforts in project scheduling assume complete information about the scheduling problem to be solved and a static deterministic environment within which the pre-computed baseline schedule will be executed. However, in the real world, project activities are subject to considerable uncertainty, that is gradually resolved during project execution. In this survey we review the fundamental approaches for scheduling under uncertainty: reactive scheduling, stochastic project scheduling, stochastic GERT network scheduling, fuzzy project scheduling, robust (proactive) scheduling and sensitivity analysis. We discuss the potentials of these approaches for scheduling projects under uncertainty.Management; Project management; Robustness; Scheduling; Stability;

Timeslack-based techniques for generating robust projectschedules subject to resource uncertainty.

The classical, deterministic resource-constrained project scheduling problem has been the subject of a great deal of research during the previous decades. This is not surprising given the high practical relevance of this scheduling problem. Nevertheless, extensions are needed to be better able to cope with situations arising in practice such as multiple activity execution modes, activity duration changes and resource breakdowns. In this paper we analytically determine the impact of unexpected resource breakdowns on activity durations. Furthermore, using this information we develop an approach for inserting explicit idle time into the project schedule in order to protect it as well as possible from disruptions caused by resource unavailabilities. This strategy will be compared to a traditional simulation-based procedure and to a heuristic developed for the case of stochastic activity durations.Uncertainty; Project scheduling; Scheduling; Research; Impact; Information; Time; Order; IT; Strategy; Heuristic;

Impact of Sugarcane Delivery Schedule on Product Value at Raw Sugar Factories

Conversion to combine harvesters has resulted in Louisiana sugarcane growers delivering a more perishable product to raw sugar factories. Dextran formation increases as the time between harvest and milling is extended. Milling of freshly cut sugarcane reduces the formation of dextran and associated economic losses. One approach available to factories to reduce dextran formation is to extend the harvested sugarcane delivery schedule to the mill. A simulation model was developed to evaluate alternative delivery schedules at raw sugar factories. Economic losses in product value associated with dextran formation were estimated and compared for various extended delivery schedules.dextran, milling, product value, raw sugar factories, scheduling, sugarcane industry, Crop Production/Industries, Marketing, Production Economics,

A case study material flow simulation based analysis for maintenance network improvement

The competitiveness of enterprises operating in complex environments depends on how well their value creation factors can adapt to disruptions caused by unanticipated events. Building this resilience requires the ability to identify uncertainties and to model their impact on operations, which is difficult to achieve. Thus, increasing adaptability in maintenance and repair networks calls for an adequate approach to address uncertainties. It is necessary to consider the maintenance activities within and outside the company as well as those affecting all equipment supplier partners. Enhancement in simulation technique has opened the opportunity to analyse this complex system. This paper presents a comprehensive analysis introducing a potential approach using material flow simulation that models and simulates the impact of existing maintenance and repair activities to identify the uncertainties to increase the flexibility of the network while ensuring profitability and continuity

Proactive, dynamic and multi-criteria scheduling of maintenance activities.

International audienceIn maintenance services skills management is directly linked to the performance of the service. A good human resource management will have an effect on the performance of the plant. Each task which has to be performed is characterised by the level of competence required. For each skill, human resources have different levels. The issue of making a decision about assignment and scheduling leads to finding the best resource and the correct time to perform the task. The solve this problem, managers have to take into account the different criteria such as the number of late tasks, the workload or the disturbance when inserting a new task into an existing planning. As there is a lot of estimated data, the managers also have to anticipate these uncertainties. To solve this multi-criteria problem, we propose a dynamic approach based on the kangaroo methodology. To deal with uncertainties, estimated data is modelled with fuzzy logic. This approach then offers the maintenance expert a choice between a set of the most robust possibilities

Planned maintenance systems with respect to modern manufacturing strategies

To remain competitive in todays's increasingly automated environment, manufacturing industry must take a more proactive and strategic attitude towards maintenance. This thesis applies these concepts, as a case study? to Philips Components Durham an advanced manufacturing unit for colour television tubes. Consideration is first given to modern manufacturing strategies and the business objectives which the maintenance strategy must support. Recent organisational changes are then discussed and analysis made of the maintenance information systems infrastructure. Having related the maintenance department functional requirements to proprietary equipment management packages, the area of machine breakdown data collection is further discussed. To address the need for improved feedback on machine performance, a shop floor data collection and analysis system (Equipment Utilisation Improvement system) has been developed and commissioned. This system now provides more accurate and detailed information than was previously available. A further success of this system is that, as a pilot project, the system has highlighted many organisational and technical issues. These must be addressed before a more comprehensive equipment management package could be successfully implemented. Based on the knowledge gained from the implementation of this system, recommendations are made on the responsibilities for maintenance tasks, appropriate training for maintenance personnel and the further development of information systems to support the maintenance function