Integrated Optimization Of Remanufacturing Production Planning And Scheduling Under Uncertain Environment

Nowadays, remanufacturing has become the inevitable choice to promote energy saving, emissions reduction and to develop circular economy under the circumstances of increasingly tense of energies and increasing material cost. The contradiction between the expansion of remanufacturing industry and the production decision-making and management method is growing. Therefore, this paper study the remanufacturing production planning and scheduling problem in order to provide theory support for the industrialization and scale production of remanufacturing. The main work and innovations are as follows:First of all, uncertain factors that cause disturbance to the operation management during remanufacturing process were summarized in detail, FGERT method based process route model was established for uncertain remanufacturing of recycled aircrafts. Aiming at the remanufacturing process with processing time as fuzzy triangular random variables, mason topology equation and equivalent fuzzy transfer function was built to obtain the probability and expected operation time of each process route branch. The proposed approach was applied to the remanufacturing process route analysis of engine crankshaft.Secondly, the credibility theory and two-stage fuzzy programming theory was introduced to set up a two-stage fuzzy remanufacturing production planning model. The model considered the uncertain parameters, such as remanufacturing machining quantity, new purchase cost and the machining cost etc., as a fuzzy vector with known probability distribution. Then in the decision making process, the deviation of production plan was adjusted and compensated after obtaining the values of the fuzzy parameters. Compensation function approximation method was discussed and a PSO algorithm based that was used to solve the model. The model and its solving algorithm were validated through multi-products and single-product case respectively.Thirdly, the process route and processing time is variable for different failure degree of recycled parts. So after selecting the quality evaluation index, the rough set discretization algorithm based on information entropy was used for attribute reduction. A rank evaluation matrix was developed by use of TOPSIS method and the quality classification of recycled parts can be done to reduce the influence of uncertain factors on the production scheduling. Bifuzzy variables were selected to describe the double uncertainty of remanufacturing processing workshops. A production scheduling model based on dual fuzzy chance constrained programming was proposed. A hybrid intelligent algorithm including double fuzzy simulation, neural network and genetic algorithm was also designed. The simulation examples show that on the basis of quality classification, the model proposed can effectively solve the remanufacturing production scheduling problem under uncertainty.Fourthly, the proposed model took scheduling approach as constraint and the total production cost as objective function, including the cost for remachining, production adjustment, overtime charge and inventory. The reprocessing time was presented by fuzzy random variable to deal with multiple uncertain phenomenons. Based on the uncertainty theory, the integrated optimization model was transformed into a fuzzy random chance constrained programming model under given confidence level. Then a hybrid optimization algorithm based on fuzzy random simulation was built. The uncertain integrated optimization model was approximated by BP neural networks and then be embedded into a three-level coded genetic algorithm to solve the model. Finally the effectiveness and feasibility of the proposed model and its solving algorithm was validated by a simulation example.Finally, on the basis of theoretical research above, this paper analyzed the basic business process of remanufacturing enterprise. A prototype for integrating remanufacturing production planning and scheduling suitable for uncertain environment was developed. The results of system test and actual application show that the research achievements of this paper can provide support for remanufacturing enterprise to coordinate the activities of the production workshop, also validate the correctness and feasibility of the production planning and scheduling theory and method.