A review of design and control of automated guided vehicle systems <s> Single-loop guide-path system <s> SUMMARY This study deals with the Automated Guided Vehicle System guide path design problem. We suggest a single closed loop guide path layout configuration as an alternative to conventional but more complex guide path designs. The benefits of using a simple guide path versus more complicated guide paths are discussed. A procedure for designing an optimal single loop guide path for a given facility layout is presented. Finally, the single loop's throughput performance is tested and compared to that of a more complex guide path. <s> BIB001 </s> A review of design and control of automated guided vehicle systems <s> Single-loop guide-path system <s> Guide path simplification can potentially reduce the complexity inherent in conventional, multi-loop automated guided vehicle systems (AGVs). A single-loop configuration is one alternative. A procedure for designing single-loop AGV systems, the OSL method was presented in a previous paper. In this paper, we suggest faster and more efficient methods for solving the two mathematical models in the OSL procedure. The first model called the valid single-loop problem (VSLP) is used to determine an initial single loop for the procedure. The method suggested is a heuristic procedure that starts from a loop around one of the departments and keeps adding departments to the loop until a valid single loop is constructed. The second model called the single-loop station location problem (SLSLP) is used to determine the location of the pick-up and delivery stations along a given loop. The method suggested converts the mixed integer formulation into a linear formulation. <s> BIB002 </s> A review of design and control of automated guided vehicle systems <s> Single-loop guide-path system <s> Asynchronized automated material handling systems, e.g. automated electrified monorail systems and automated guided vehicle systems, have been playing important roles in manufacturing. Reliability becomes a critical issue as manufacturing enterprises are moving toward automation. In the past, reliability tissue has not been analysed explicitly for these types of systems. In this research, a new measure was proposed to specify reliability. A mixed integer programming model was developed to design flow paths for a special class of material handling systems, i.e. single-loop dual-rail systems. The model can be used to design systems with higher reliability. The model and application procedure in design and analysis were demonstrated through two case studies. <s> BIB003 </s> A review of design and control of automated guided vehicle systems <s> Single-loop guide-path system <s> The purpose of this article is to formulate and solve a shortest loop problem associated with the design of material flow handling systems in factories. The problem is formulated as an Integer Linear Program (ILP) initially containing a very large number of constraints. Several simplifications are proposed in order to reduce the problem to a size amenable by standard ILP solvers. Computational results confirm the efficiency and practicality of the proposed approach. <s> BIB004
The main difference between the single-loop and the conventional guide-path system is that in the single-loop layout, vehicles travel in only one loop without any shortcut or alternative routes (e.g. the loop in the left part of Figure 2 ). The travel mode in the single-loop system is usually unidirectional. Bidirectional traveling is possible but in this case vehicle interference is likely to happen. Vehicles in single-loop systems can be controlled by simple dispatching rules such as first-encountered-first-serve (FEFS), implying that an empty vehicle should pick up the first load it encounters. BIB001 propose an optimal procedure to design a single-loop system. This procedure includes five components: (1) An IP formulation is used to find an initial valid loop (a valid single loop problem -VSLP) -a valid loop contains at least one segment for each department in the facility layout. Their iterative algorithm involving of solving two 0-1 integer-programming (IP) models is very time consuming for realistic problems. Some other models and solution procedures for the single loop guide-path system design are proposed in BIB002 , BIB003 , and BIB004 . BIB003 results. This SLDR problem was solved using CPLEX (an optimization package). An instance containing 13 P/D locations needs about 2hrs of computation time using CPLEX on a SPARC station 2. BIB004 propose an alternative formulation to BIB001 that has a smaller number of binary variables and considers a larger set of feasible integer solutions. Their formulation takes the design of a unidirectional singleloop and the location of P/D stations into account at the same time. The throughput of the single-loop system drops slightly compared with the throughput of the conventional system BIB001 . To obtain the same throughput with the conventional system, the single-loop system needs more vehicles. Obviously, the single-loop system eliminates the inference problem at intersections (this system has no intersection at all). However, with multiple vehicles operating in the same loop, vehicle interference is still possible, since vehicles may have different operating speeds, etc.