Research On Integrated Scheduling Of Production And Preventive Maintenance Based On Machine Condition

In the traditional production scheduling research,the machine is considered to be always available,but in practice,the machine would wear out due to use too long,which makes the machine production efficiency lower,and in serious cases,the failure occurs,so the machine needs to be preventive maintained.Although the machine preventive maintenance takes a certain amount of production time,it can improve the performance of the machine and prolong its service life.It can be seen that the relationship between machine preventive maintenance and production scheduling is very close,so it is very necessary to conduct comprehensive decision-making research on production scheduling and preventive maintenance.The current research can be divided into two major categories according to the determination of preventive maintenance time.One is the integrating scheduling of production and periodic preventive maintenance,and the other is the integrating scheduling of production and preventive maintenance based on machine condition.In this paper,the following problems is done on the integrating scheduling of production and preventive maintenance based on machine condition:The first problem is not to consider about machine failure and assumes the duration of preventive maintenance is fixed.Three preventive maintenance strategies are proposed based on the effects of duration to machine condition:due to longer duration the machine condition returns to the original value after preventive maintenance,due to shorter duration and the effect of preventive maintenance frequency that the machine condition successively decremented after preventive maintenance,and due to shorter duration and the effect of machine condition when preventive maintenance begins to carry that the machine condition changes within the interval after preventive maintenance,which is studied in the case of the preventive maintenance is carried out when machine condition declines to one condition or a fixed condition interval.The optimization goal is to minimize the total completion time and minimize the maximum completion time.A solution model is established for the problem and solved by genetic algorithm.The experimental results show that the preventive maintenance time is better at the threshold point,and the preventive maintenance duration is fixed and the status is successively decremented strategy is optimal when the number of jobs is small.When the number of jobs is large,the preventive maintenance duration is fixed and state recovery is as new as optimal.The second problem is not to consider about machine failure and assumes the duration of preventive maintenance is related to machine condition.On the basis of the first problem,consider when the preventive maintenance duration is related to the condition of the machine when preventive maintenance is started and the condition of the machine when preventive maintenance is completed,two preventive maintenance strategies are proposed based on preventive maintenance duration and machine condition:machine condition returns to initial value after preventive maintenance and machine condition changes within the interval after preventive maintenance,which is studied in the case of the preventive maintenance is carried out when machine condition declines to one condition or a fixed condition interval.The optimization goal is to minimize the total completion time and minimize the maximum completion time.A solution model is established for the problem,and the genetic algorithm is used to solve the problem.A heuristic algorithm is added to the genetic algorithm for the case that the machine condition is not well determined after preventive maintenance for the strategy that machine condition changes within the interval after preventive maintenance.The experimental results show that the preventive maintenance time is better when machine condition declines to one condition,and the strategy that machine condition changes within the interval after preventive maintenance is better.The third problem is to consider about machine failure and assumes the duration of preventive maintenance is related to machine condition.On the basis of the second problem,the optimal preventive maintenance strategy is selected,and consider about the various fault maintenance strategies:minor repair,minor repair/medium repair,minor repair/overhaul.The optimization goal is to minimize the total completion time and minimize the maximum completion time.A solution model is established for the problem,and a genetic algorithm with heuristic algorithm is applied to solve the problem.The experimental results show that the fault repair strategy of minor repair/medium is the best for minimizing the total completion time and minimizing the maximum completion time.