Research On Mobile Grading And Precooling Scheduling Of Fruits And Vegetables Based On The-First-One-Kilometer Problem

At present,there are some problems in the " first one kilometer " of fruits and vegetables in China,such as low manual grading efficiency and untimely precooling service.The characteristics of scattered fruit and vegetable producing areas and small and medium-sized scale make it difficult to implement post harvest process treatment.Although the emerging mobile grading and precooling equipments applied in the field can solve the above problems,there is a broken chain in the classification and precooling links.It is necessary to coordinate the mobile grading and precooling resources to reduce the service interval,so as to ensure the quality of fruits and vegetables and reduce the decay rate.Based on this,this paper comprehensively considers the service sequence constraints of grading and precooling,the time interval constraints of grading precooling service,and combined with whether the fruits and vegetables have strong timeliness,constructs the collaborative scheduling model under two scenarios.One is for the corrosion-resistant fruits and vegetables with long shelf life.In this scenario,the quality change of fruits and vegetables in a single day is not obvious,so the model focuses on realizing high service level and low service cost;The other is for perishable fruits and vegetables with short shelf life.In this scenario,timely and effective precooling of fruits and vegetables can delay decay and deterioration.Therefore,when building the model,it should ensure that the precooling link is carried out within the optimal precooling delay time to improve the precooling effect.The specific research contents are as follows:(1)A single objective hierarchical precooling vehicle collaborative scheduling model is designed for corrosion-resistant fruits and vegetables.In order to shorten the service interval and optimize the cost,a model considering the dual soft time window constraints of hierarchical precooling sequence constraint and hierarchical precooling maximum service interval is constructed.Then a hybrid variable neighborhood genetic algorithm with customer clustering is designed according to the characteristics of the model.The effectiveness of the algorithm is proved by comparing with adaptive genetic algorithm and variable neighborhood search algorithm.In addition,using the example data of apple in Luochuan County,Shaanxi Province,the results show that the sorting cost under this model is 20% lower than that of manual sorting,and the precooling cost is 36% lower than that of precooling warehouse.Finally,the sensitivity analysis is carried out from the two aspects of service level and the proportion of pre cooled vehicles,and the management suggestions under this mode are given.(2)A multi-objective vehicle cooperative scheduling model is designed for perishable fruits and vegetables.In order to ensure the timeliness of precooling of perishable fruits and vegetables,the precooling delay cost is added to the total cost to reflect the quality changes of fruits and vegetables.At the same time,the precooling delay time is introduced as the goal for multi-objective optimization.On this basis,a multi-objective genetic algorithm considering space-time distance is designed and compared with NSGA-Ⅱ algorithm to prove its effectiveness.Using the example of strawberry collection in Dandong Ci ty,it is found that the average utilization rate of grading vehicle and precooling vehicle under this mode is low,which is related to the dispersion of customer points.In addition,it performs well in precooling delay time and synergy,which means that the application of the model can effectively improve the quality of fruits and vegetables and bring high customer satisfaction.Finally,the sensitivity analysis is carried out based on the vehicle working speed and the proportion of precooling demand to find a more suitable parameter setting in this scenario.To sum up,this study expands the vehicle collaborative scheduling model and the " first one kilometer " optimal scheduling research to a certain extent,and provides a reference for the promotion and use of mobile grading and precooling facilities in small farmers in the future.