Tone Lerher

Travel time models for automated warehouses with aisle transferring storage and retrieval machine

This paper presents analytical travel time models for the computation of travel time for automated warehouses with the aisle transferring S/R machine (in continuation multi-aisle AS/RS). These models consider the operating characteristics of the storage and retrieval machine such as acceleration and deceleration and the maximum velocity. Assuming uniform distributed storage rack locations and pick aisles and using the probability theory, the expressions of the cumulative distribution functions with which the mean travel time is calculated, have been determined. The computational models enable the calculation of the mean travel time for the single and dual command cycles, from which the performance of multi-aisle AS/RS can be evaluated. A simulation model of multi-aisle AS/RS has been developed to compare the performances of the proposed analytical travel time models. The analyses show that regarding all examined types of multi-aisle AS/RS, the results of proposed analytical travel time models correlate with the results of simulation models of multi-aisle AS/RS.

Travel time model for double-deep shuttle-based storage and retrieval systems

Technological developments in the global supply chain have changed processes in warehousing. This reflects in short response time in handling the orders, which has a consequence on high automation degree in warehousing. An important part of automated warehouses is presented by shuttle-based storage and retrieval systems (SBS/RS), which are used in practice when demand for the throughput capacity is high. In this paper, analytical travel time model for the computation of cycle times for double-deep SBS/RS is presented. The advantage of the double-deep SBS/RS is that fewer aisles are needed, which results in a more efficient use of floor space. The proposed model considers the real operating characteristics of the elevators lifting table and the shuttle carrier with the condition of rearranging blocking totes to the nearest free storage location during the retrieval process of the shuttle carrier. Assuming uniform distributed storage locations and the probability theory, the expressions for the single and dual-command cycle of the elevators lifting table and the shuttle carrier have been determined. The proposed model enables the calculation of the expected cycle time for single- and dual-command cycles, from which the performance of the double-deep SBS/RS can be evaluated. The analysis show that regarding examined type of the double-deep SBS/RS, the results of the proposed analytical travel time model demonstrate good performances for evaluating double-deep SBS/RS.

Travel time models for double-deep automated storage and retrieval systems

In this paper new analytical travel time models for the computation of cycle times for unit-load double-deep automated storage and retrieval systems (in continuation double-deep AS/RS) are presented. The proposed models consider the real operating characteristics of the storage and retrieval machine and the condition of rearranging blocking loads to the nearest free storage location during the retrieval process. With the assumption of the uniform distributed storage rack positions and the probability theory, the expressions of the single and modified dual command cycle have been determined. The proposed models enable the calculation of the mean cycle time for single and dual command cycles, from which the performance of the double-deep AS/RS can be evaluated. A simulation model of the selected double-deep AS/RS has been developed to compare the performances of the proposed analytical travel time models. The numerical analyses show that with regard to the examined type of double-deep AS/RS with a different fill-grade factor, the results of the proposed analytical travel time models correlate with the results of simulation models of double-deep AS/RS.

Simulation-based performance analysis of automated single-tray vertical lift module

In this paper a simulation analysis of an automated single-tray Vertical Lift Module (VLM) system is presented. Compared to other well-known warehouse systems, a VLM system can provide moderate throughput capacity and lower investment cost. The objective of the study is to investigate benefits of a single-tray VLM system design in terms of reducing transactions’ mean cycle time, which results in increased throughput of the system. Performance of the single-tray VLM is evaluated regarding alternative design configurations and the velocity profiles. The results show that single-tray VLM systems are effective and may serve as guideline for warehouse designers in designing a new or improving an existing automated warehouse system.

Method for evaluating the throughput performance of shuttle based storage and retrieval systems

In this paper a method for throughput performance calculation of shuttle based storage and retrieval systems (SBS/RS) is presented. SBS/RS represent a new technology in automated storage and retrieval systems. Since it is important to design SBS/RS right the first time due to the relative inflexibility of the physical layout, we provide a proposed method for the throughput performance calculation of these systems. The performance of the system is considered as a throughput capacity of the SBS/RS as a whole.

Multi-objective optimisation model of shuttle-based storage and retrieval system

AbstractThis paper presents a multi-objective optimisation solution procedure for the design of the Shuttle-Based Storage and Retrieval System (SBS/RS). An efficient SBS/RS design should take into account multi-objectives for optimization. In this study, we considered three objective functions in the design concept which are the minimization of average cycle time of transactions (average throughput time), amount of energy (electricity) consumption and total investment cost. By also considering the amount of energy consumption as an objective function for minimization, we aimed to contribute to an environmentally friendly design concept. During the optimization procedure, we considered seven design variables as number of aisles, number of tiers, number of columns, velocities of shuttle carriers, acceleration/deceleration of shuttle carriers, velocity of the elevators lifting tables and acceleration/deceleration of the elevators lifting tables. Due to the non-linear property of the objective function, we ut...

Parametric Study of Throughput Performance in SBS/RS Based on Simulation

This paper presents an analysis of cycle times and throughput performances of Shuttle-Based Storage and Retrieval Systems (SBS/RSs), a relatively new technology that is becoming an important part of automated warehouses. A parametric simulation model was developed for the purposes of this research. The model enables calculation of Single Command (SC) and Dual Command (DC) cycle times and throughput performances of SBS/RS. The model was tested on a case study, which is based on a real type of SBS/RS. Experiments were designed to evaluate the following factors, such as number of bays nx and minimum warehouse volume Q. Our research uses Design of Experiment (DOE) analysis and helps to achieve the proper dimension of the SBS/RS, which gives us the best possible performance of the SBS/RS. The simulation based on the presented model delivers the best SBS/RS designs. (Received in May 2016, accepted in October 2016. This paper was with the authors 2 months for 1 revision.)

Designing Unit Load Automated Storage and Retrieval Systems

The successful performance of the unit load automated storage and retrieval systems is dependent upon the appropriate design and optimization process. In this chapter a model of designing unit load automated storage and retrieval system for the single- and multi-aisle systems is presented. Because of the required conditions that the unit load automated storage and retrieval systems should be technically highly efficient and that it should be designed on reasonable expenses, the objective function represents minimum total cost. The objective function combines elements of layout, time-dependant part, the initial investment and the operational costs. Due to the nonlinear, multi-variable and discrete shape of the objective function, the method of genetic algorithms has been used for the optimization process of decision variables. The presented model proves to be a useful and flexible tool for choosing a particular type of the single- or multi-aisle system in designing unit load automated storage and retrieval systems. Computational analysis of the design model indicates the model suitability for addressing industry-size problems.

Aisle changing shuttle carriers in autonomous vehicle storage and retrieval systems

The objective of this study is to propose analytical travel time models for aisle changing shuttle carriers, which are capable of travelling in the horizontal and in the cross-aisle directions. The expressions for the single and dual command travel times have been determined assuming uniform distributed storage locations and the probability theory. A simulation model has been applied for the performance analysis of the proposed analytical models. The proposed models enable the calculation of the expected travel times for single and dual command cycles of the aisle changing shuttle carriers, from which the performance can be evaluated.

Evaluating costs of vehicle use in military logistics

The article presents an analytical model of evaluating costs of vehicle use in military logistics adapted to specific construction demands and characteristics of military vehicles, profile (conditions and manner) of use and technological procedures of preventive and remedial maintenance of military vehicles. The proposed model of evaluation enables an equivalent comparison of total costs in advance of use of similar vehicles made by different manufacturers throughout the entire operating period (their service life). Initial (entry) and boundary conditions are clearly defined within the proposed model. The implementation of the analytical model ensures the evaluation and planning of maintenance costs and costs of direct vehicle use in military logistics already at the point of purchasing new vehicles, as well as evaluation of optimal operating period (service life) of vehicles, which leads to increased reliability and availability, and, consequently, to more effective use of military vehicles.