Storage and retrieval automation has progressed rapidly. One such popular storage and retrieval system deploys two passing aisle-bound cranes. Each crane can access every location in the rack. To pass the other crane and prevent collision, each crane has to timely move the platform to an appropriate level and simultaneously rotate it. We develop a queuing model with preemptive-resume interrupted service to estimate the system response time (and hence throughput capacity) while considering two I/O point positions, random storage, and a crane assignment policy where all requests are shared between the cranes. The analytical models are validated with simulation based on the data from real cases. We find that a design with I/O points located in the middle of the rack will increase the interference, but it has a high relative throughput because of the reduced expected travel time. Compared with a system with one crane, a two-crane system has interference, but it can improve the system efficiency, especially in large systems with high job arrival rates. The model can be extended to other systems where multiple cranes are used in a single travel aisle with crane interference, e.g. passing cranes operating in a container stack lane.

存储和检索自动化发展迅速。一种流行的存储和检索系统部署了两台通过过道的起重机。每台起重机都可以访问机架中的每个位置。为了通过另一台起重机并防止碰撞，每台起重机必须及时将平台移动到适当的水平并同时旋转。我们开发了一个具有抢先恢复中断服务的排队模型来估计系统响应时间（以及由此产生的吞吐量），同时考虑两个 I/O 点位置、随机存储和起重机分配策略，其中所有请求在起重机之间共享。分析模型通过基于真实案例数据的模拟进行验证。我们发现 I/O 点位于机架中间的设计会增加干扰，但由于减少了预期的旅行时间，它具有较高的相对吞吐量。与单吊系统相比，双吊系统存在干扰，但可以提高系统效率，尤其是在作业到达率高的大型系统中。该模型可以扩展到其他系统，其中多个起重机在单个行进过道中使用起重机干扰，例如在集装箱堆垛车道上运行的经过起重机。