| The objective of preventive scheduling is to get a preventive scheduling scheme with certain anti-interference ability, by the estimation and description of uncertain factors in the project, on the basis of various constraint conditions, such as the relationship of tasks and limited resources. The paper mainly studies the uncertain duration and release-time. The uncertainty of duration is related to the incomplete project information, the failure of equipment during the execution etc. release-time refers to is the terminal time the all external preparation activities, describes the uncertainty of external environment, such as the supply of raw materials and the environment of transportation etc.For the preventive scheduling of project problem with uncertain duration, this paper represents uncertain duration by six point fuzzy number, the maximized robustness of scheme as the optimization objective, to set up a mathematical model. Based on the NP-hard property of the problem, this paper designs an ant colony optimization algorithm to solve the problem by the related operations and comparison principle of fuzzy numbers, combining priority rule of minimum relaxation time. The validity of the algorithm to solve project scheduling problem with duration is proved by some examples, and the comparison methods of fuzzy number have a little effect on the algorithm.This paper also studies the preventive scheduling of the project with dual uncertainty, including the uncertainty of duration and release-time. The paper respectively uses the exponential distribution and fuzzy number to describe the uncertain release-time, to get the preventive scheduling schemes by the two stage algorithm or re scheduling method, combining the preventive scheduling scheme So for the project with uncertain duration. Re-scheduling method uses the ant colony optimization algorithm to solve the problem by improving the preventive scheduling model, according to the constraint of release-time to the start-time. And the experimental results show that, re-scheduling method can obtain a prevention scheduling scheme with higher robustness for the projects with dual uncertainty. |
