Automation in warehouses: study of the new technologies through the development of design and assessment models

This research project is based on the awareness that innovation in logistics processes becomes an important element to support and improve the management of goods flows throughout the entire supply chain, especially in a changing environment as one in which the companies are now operating (e.g. Sauvage, 2003; Grawe, 2009). To export products into new markets, to be customer-oriented and to increase sustainability are the key features of today’s competitive market that stress the modern logistics process. Today’s warehouses must be able to respond both efficiently and responsively to customer demand with continuously changing assortments and small order sizes (especially due to the growth of the e-commerce B2C market), and in their evaluation also sustainability concerns should considered (e.g. De Koster et al., 2007; Baker and Canessa, 2009; McKinnon et al., 2012). In this context, warehouses, above all distribution centres, have an increasingly strategic role and are subjected to pressures in terms of both cost and service. In terms of cost, they represent approximately 20 per cent of total logistics cost (Dhooma and Baker, 2012), whilst in terms of service they are critical to the achievement of customer service levels (Frazelle, 2001), particularly as distribution centres are often the final point in the supply chain and operate as cross-docking points, value added service centres (e.g. kitting, pricing and labelling), production postponement points (e.g. order assembly based on the specific customers’ requirements), returned good centres (for reverse logistics of packaging, faulty goods or end-of-life goods) and many other activities, such as service and repair centres. All of these factors led companies to view the automation as a means to achieve greater operational efficiency and to cope with the aforementioned challenges so that they can maintain competitiveness. Automated solutions in distribution are increasingly adopted in distribution centres. The annual growth of the total revenues of the top twenty material handling suppliers increased up to 26% and 4% in 2011 and 2012, respectively. As traditional automated unit load storage and retrieval systems often do not perform well in such a context, as they are expensive and inflexible in handling fluctuating product volumes (e.g. Roodbergen and Vis, 2009), material handling providers develop new solutions that bring both the promise of low operational cost and inherent volume flexibility and can change the way in which the distribution centres operate. Although it is imperative to the success of businesses that warehouses are designed so that they function both effectively and efficiently, a company can not have the right competences to face with the complexity of new technologies when evaluating them. It has to take into account operational, economic and sustainability performances simultaneously. Therefore, companies are interested in performance analysis and design tools for the new solutions, and in the comparison among them. The present research, on one hand, would contribute to the extant literature on warehouse design and modelling of innovative automated material handling systems. On the other hand, it aims at supporting companies in the choice of the right technology that best suits their needs and goals by assessing new material-handling solutions in terms of system performance analysis, advantages and disadvantages, and application areas. Carried out in close cooperation with material handling providers, this dissertation is based on the development of analytical models and design frameworks, the investigation of design issues, and the evaluation of environmental sustainability concerns for such automated solutions.

Oggi i centri distributivi devono essere progettati in modo da rispondere in modo efficiente e reattivo alle variazioni della domanda dei clienti. Tuttavia, i sistemi di stoccaggio e prelievo tradizionali sono spesso costosi e non abbastanza flessibili per seguire questa erraticità nelle richieste dei clienti. Per rispondere a questa esigenza, negli ultimi anni, i fornitori di soluzioni di material handling hanno sviluppato nuove tecnologie che potenzialmente portano a livelli più elevati di efficienza e flessibilità. Focalizzandosi su due di queste tecnologie innovative (sistemi di stoccaggio automatizzato che utilizzano veicoli autonomi e sistemi di stoccaggio compatti che impiegano shuttle), questo lavoro di tesi ha l’obiettivo di i) analizzarne le performance, ii) capire quale sia la loro configurazione ottima noti i parametri di progettazione, iii) valutarne l’impatto ambientale, ed iv) effettuare un confronto con le tecnologie più consolidate per individuare le aree di convenienza. In particolare, lo studio delle performance avviene attraverso lo sviluppo di modelli di teoria delle code validati con simulazione. Supportata dal confronto con i fornitori di material handling, la tesi si propone, da un lato, di arricchire l’attuale letteratura scientifica sulla modellizzazione delle tecnologie più recentemente introdotte per la movimentazione all’interno dei centri distributivi. Dall’altro lato, i risultati consentono di supportare il processo decisionale delle aziende per selezionare la tecnologia più adatta date le caratteristiche dei prodotti da gestire e i suoi obiettivi di medio-lungo periodo.