Study On Operational Policies And Optimization In Compact Automated Parking Systems

Under the development of economic globalization and electronic commerce,the warehousing system in logistics has gained greatly development.In modern urban life,space resources become scarce and expensive.How to quickly find an empty parking spot in the destination becomes very important.Based on this,the Compact automated parking system(CAPS),which has a higher compact storage area and stronger car handling capacity,has been produced in the last decade.At present,the system has been used in many countries and enterprises,especially in VW parking storage system in Wolfsburg,Germany’s largest vehicle delivery center,and two layers parking system of Israel’s and so on.However,there are not literature on theory study.The previous scholars’ studies are concentrated small volume and more varieties,CAPS system can be used to store large volume and weight load.So,theory study for this kind of system is very necessary.Moreover,it provides very important protheoretical reference value for the warehouse managers when they design this kind of system.Based on this,this dissertation studies the operating policies and optimization of compact automated parking system.Firstly,this dissertation studies the operating policies of the lift in compact automatic parking system.In the parking system,scholars focus on transportation、economy and traditional single-layer parking system.This dissertation studies a new compact and automatic multi-layer cylindrical parking system.This system uses continuous or discrete lifts to transport the car in a vertical direction and uses horizontal rotating rings equipped with shuttle to transport the car in the horizontal direction.This dissertation presents continuous lift decicated operating policy、discrete lift decicated operating policy and discrete lift general operating policy,and constructed the corresponding open queuing network model for the three lift operating policies.The results show that the continuous and discrete lift exist a cross point of customer arrival rate.When the system of car arrival rate is low,the discrete elevator can provide higher system turnover capacity,and when the system vehicle arrival rate is high,continuous elevator can provide higher system turnover capacity.The study also found that discrete lift general lift operating policy always performs better than the discrete lift dedicated operating policy.Secondly,this dissertation studies the structure optimization problem of general compact automated parking system.Since the number of lifts is the bottleneck of the turnover capacity the general compact automated parking system,this dissertation is aim to find the optimal number of lifts that satisfy the system maximum throughput rate.Based on this,this dissertation constructs a performance index evaluation model based on open queuing network of GCAPS system.The results show that the optimal number of lifts is always 2 when the system has the optimal number of tiers.In addition,based on constraint conditions of the transaction time,we construct the cost function.The results show that the system structure under the cheapest cost is not necessarily the minimum transaction time.Warehouse manager may choose system structure under the cheaper cost,since the cost less benefits more than time increase.Thirdly,this dissertation studies the shuttle operating policies of the general compact automated parking system.This dissertation considers another important factor that affects the system turnover capacity of general compact automated parking system: shuttle.Based on the assignment rules of the shuttle to elevator: the closest rule or random rule,considering the dedicated shuttle operating policy and random shuttle operating policy,and build queuing network model,separately.Results show that the dedicated shuttle operating policy is always better than the random shuttle operating policy,and based on this,this dissertation also investigate the optimal number of the lifts under the dedicated shuttle operating policy,the research results show that when the system has the optimal number of tiers,the number of the lifts are always two.Fourthly,this dissertation studies the operation time optimization of the compact automated vehicle parking system with double storage rings.In the compact automated vehicle parking system with double storage rings,the car vertical movement needs to be discrete lift and vertical automated guided vehicle,the car horizontal movement needs the rotating ring and the horizontal automated guided vehicle,this system also called robotic compact automated parking system.This dissertation considers the retrieval transaction time of CAVPS,and build the corresponding queuing network model based on the car storage position.This dissertation firstly optimizes the system structure,and the results show that the optimal number of tiers are range from 8 to 10.This dissertation also investigates the retrieval transaction time and footprint area of CAVPS system and CAPS system under the same system storage capacity.The results showed that retrieval transaction time of CAVPS system improved at least 29.7% over the CAPS system,and the total footprint area improved by 32.0%.