| With the continuous development of social economy and science and technology,people are enjoying the constantly updated and functional scientific and technological products,and at the same time,the obsolete products facing the end of life are also accumulating at an alarming rate.If these waste products are discarded at will or directly disposed of by incineration and landfill,it will not only cause serious pollution and damage to the ecological environment,but also a great waste of resources.As one of the effective ways to deal with waste products,the recycling disposal of waste products not only promotes the development of circular economy,but also greatly promotes the sustainable development of human society.By recycling these waste products and extracting reusable parts or raw materials from them,the purpose of reusing,remanufacturing and recycling of waste products can be realized.Disassembly is the key link to realize the recycling disposal of the waste products,and in order to adapt to the large-scale disassembly production of enterprises,the disassembly line is gradually popularized.The load balance degree of each workstation in the disassembly line is an important factor restricting the production efficiency of the disassembly line,thus in order to realize the efficient production of the disassembly line,the work load of each workstation of the disassembly line must be balanced as much as possible.On the basis of field investigation on the actual production of disassembly enterprises,aiming at the defects of low production efficiency and waste of production resources existing in the disassembly line with linear layout,a kind of parallel disassembly line which can simultaneously disassemble hybrid products is designed,and modeling and optimization of the parallel disassembly line balancing problem(PDLBP)is addressed.Firstly,aiming at the PDLBP,a multi-objective mathematical model with the optimization objectives of minimizing the number of workstations,minimizing the balance index of workstation idle time and minimizing the number of disassembly resources is constructed,and a multi-objective improved migrating birds optimization(IMBO)algorithm is proposed to solve the problem.The effectiveness and superiority of the proposed IMBO algorithm are tested by two DLBP examples with different scales.Then the constructed multi-objective PDLBP model and the proposed multi-objective IMBO algorithm are applied to the parallel disassembly line designed for the waste refrigerators and CRT TV sets of the filed investigated disassembly enterprise.The solving results of the parallel disassembly line are compared with those of the original disassembly line of the two products when they are disassembled separately.The comparison results show that the production layout of the parallel disassembly line can effectively reduce the idle time and the waste of production resources when the products are disassembled separately.Moreover,the parallel disassembly line integrates and makes more efficient use of the production resources,thus the parallel disassembly line has more optimization space in each objective.Secondly,considering the production costs and benefits of disassembly enterprises and the impact of disassembly production on the ecological environment,a partial disassembly production mode is proposed for parallel disassembly line,in which only the parts with reuse and remanufacturing requirements and the parts containing hazardous substances are required to be removed.Based on the partial disassembly production mode,the disassembly path planning and the workstation allocation scheme of corresponding disassembly tasks are optimized in order to achieve the goal of minimizing the actual cycle time of parallel disassembly line,minimizing the number of workstations,minimizing the balance index of workstation idle time and minimizing the amount of resources required for disassembly production.Then a multi-objective mathematical model aimed at the parallel partial disassembly line balancing problem(PPDLBP)is constructed and a novel multi-objective hybrid group neighborhood search(HGNS)algorithm is presented.The solving performance of the proposed HGNS algorithm is tested through two complete DLBP examples with different scales and a partial DLBP example.Then,the proposed HGNS algorithm is applied to solve the PPDLBP instance of the filed investigated waste refrigerators and CRT TV sets.By comparing the solution results of the PPDLBP instance with those of parallel disassembly line of the two products under complete disassembly production mode and those of disassembly line of the two products when they are disassembled separately,the advantages of the parallel partial disassembly line in each optimization objective are proved.Considering the uncertainty of structure and quality of recycled waste products which may influence the balance of disassembly line,the end-of-life(EOL)state oriented parallel partial disassembly line balancing problem(EPPDLBP)is studied.In order to deal with the uncertainty of structure and quality of waste products,the random sampling survey method is used to calculate the occurrence probability of different EOL conditions for each part of the waste products,then the occurrence probability of different EOL states of the waste products can be calculated and the operation time of the disassembly tasks corresponding to each EOL state can be investigated.By adopting the solving method of mixed-model disassembly line balancing problem,the disassembly precedence relationship diagram corresponding to each EOL state of the waste products is transformed into a comprehensive disassembly precedence relationship diagram.Based on this,a multi-objective model aimed at the EPPDLBP is established and an improved discrete multi-objective firefly algorithm(IFA)is proposed to solve the problem.The solving performance of the proposed IFA is tested by two DLBP examples with different scales.Then,the IFA is applied to solve the EPPDLBP instance of the field investigated refrigerators and CRT TV sets two kinds of waste products.By comparing with the simulated annealing(SA)algorithm and genetic algorithm(GA),the advantages in solving stability and comprehensive solving quality of the proposed IFA is further proved.Finally,the theoretical research results of the parallel disassembly line are applied to the bogie repair line of a railway vehicle maintenance company.By designing the parallel repair line for the bogies and solving the parallel repair line balancing problem,the solution results of the parallel repair line are compared with those of the original linear repair line,which shows that the parallel repair line can reduce the number of workstations,reduce the idle time balance index,reduce the number of resources required for maintenance,balance the workload of each workstation and improve the maintenance efficiency.And then the Plant Simulation software is used to simulate the representative solutions of the parallel repair line and the original linear repair line.The corresponding simulation model is established to evaluate the working condition of each maintenance station and maintenance output under the maintenance condition full of uncertain factors.The simulation results further verify the superiority of the designed parallel repair line in improving maintenance efficiency compared with the original linear repair line,and provide theoretical and simulation data support for maintenance of railway vehicle bogies. |
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