In this work, we focus on optimization of multiaisle automated storage/retrieval system (MA AS/RS). Analytical models of the cycle time for this type of systems are presented, and the optimal dimensions of MA AS/RS for a minimum cycle time are evaluated. The analytical expressions of the cycle time have three real variables representing the three displacement times: horizontally (t h ), vertically (t v ), and between aisles (t p ). In addition to causality constraints of horizontal and vertical transport times, there is another one related to the size of the system and to its constancy. This takes us back to optimization problems in real numbers of three variable functions with constraints. For their optimization, some variable variations are likely to give a relaxation of the constraint on the size of the system, thus reducing them to two variable functions. In the first part of the work, the analytical expressions of the cycle time are optimized, considering the three travel times t h , t v , and t p as variables. The results of these investigations allow determining a global minimum with useful regions where the minima are close to this global minimum. This allows a greater flexibility when designing the system, due to the possibility of making contingent variations on the dimensions of the system, in a wide range, without significant changes in the cycle time. In the second part, one of the travel times is supposed to be constant and then the optimal values of the other two are calculated. This will be essential in case there are dimensional constraints on premises used to house the AS/RS. If one dimension is fixed, then finding the optimal values of the other two is possible.
MSWM (Municipal Solid Waste Management) is a challenge in developing countries, especially in Algeria. In this paper, a quantitative analysis is proposed, showing that the collection of recyclable items qualified as a high-quality raw material will build a wide profit. The locations
of recycling centers in Algeria were determined for the plastic, paper/cardboard, metal, textile and glass. The annual generated amount of each type of recyclable was defined and finally a range of purchase prices was established to estimate the possible price to sell these products. The purpose
was to find the most profitable recyclable material to be collected in order to motivate both the informal sector and the recycling industry to collect recyclables. It was observed that plastic is the most profitable recyclable followed by the paper/cardboard, and then textile.
Over the past few years, automated storage and retrieval systems (AS/RSs) have been increasingly improving. It is worth mentioning that multi-shuttle storage/retrieval (S/R) machines were gradually introduced to the market some years ago. These machines, which possess a high speed of execution, are able to transport several pallets at a time during the same trip, as opposed to single-shuttle S/R machines which can carry only one pallet at a time. It should be noted that the installation of this type of system requires a significant financial investment, and therefore it is highly recommended that this system be well studied and designed prior to its installation. It is widely acknowledged that one of the most important objectives while designing an AS/RS is to achieve the shortest time for one single cycle. The present work aims at designing an AS/RS with optimal dimensions for the purpose of minimizing the time in a multi-cycle implementation. To do this, it was decided to consider a multi-aisle automated storage/ retrieval system (AS/RS) with a multi-shuttle S/R machine. In addition, a genetic algorithm (GA) was used for the optimization of the system.
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