http://ieeexplore.ieee.org TOC Alert for Publication# 8856 2008 May 12 Lean buffering is the smallest buffer capacity, which is necessary and sufficient to ensure the desired production rate of a manufacturing system. Literature offers methods for designing lean buffering in production systems with identical machines. The current paper extends these methods to serial production lines with nonidentical machines, assuming that they obey the exponential reliability model. For two-machine lines, exact formulas for lean buffering are derived, while for longer lines estimates are obtained. These results can be useful for production line designers and production managers to maintain the required production rate with the smallest possible inventories. ]]> 5 2 298 306 544 This paper addresses several questions related to the control of timed continuous Petri nets under infinite server semantics. First, some results regarding equilibrium states and control actions are given. In particular, it is shown that the considered systems are piecewise linear, and for every linear subsystem the possible steady states are characterized. Second, optimal steady-state control is studied, a problem that surprisingly can be computed in polynomial time, when all transitions are controllable and the objective function is linear. Third, an interpretation of some controllability aspects in the framework of linear dynamic systems is presented. An interesting finding is that noncontrollable poles are zero valued. Note to Practitioners¿Petri nets are a well-known formalism for the analysis and design of discrete event systems. Due to the state- explosion problem some kind of relaxation is frequently used. In particular, fluidification is a classical approximation technique that it is usually employed in the analysis of manufacturing or logistic systems, specially when heavily loaded. This work focuses on timed continuous Petri nets which are a fluidified version of discrete Petri nets with timing associated to transitions (representing stations with servers that perform activities). Furthermore, transitions have associated control actions which can slow down the corresponding activities from an initial maximum speed, that depends on the marking, and possibly halt them completely. The steady-state control problem of this kind of system and some invariant-dynamical properties are addressed. ]]> 5 2 307 320 738 This paper extends pin-tool research by investigating a new method to accurately position high-fidelity pins in an array, with each pin uniquely positioned under computer control. The resultant tool is a reusable prototyping system for the rapid generation of three-dimension (3-D) profiles using CAD extracted data, with application potential in a variety of manufacturing processes. A control assessment identifies a combination of array-addressing, latching positioning hardware, and a combined “setting platen” pin-position feedback and drive as an appropriate technique for pin control. The novel platen motion strategy is capable of moving thousands of pins with a single drive motor. The system incorporates latching “locks” that operate on the “tail” of a new two-part “header and tail” pin design. Key to the lock strategy is the application of shape memory alloy actuators in a back-to-back configuration; the response of this material to electrical input is quantified and applied to achieve the unique lock design. Multiple locks combined into a demonstrator position headers to an accuracy of ${+}0.09$ ${-}0.05$ mm. The mounting pitch of the prototype system permits the use of 1.0 mm section pins. An extension to the design ultimately allows a 15 000 pin-array to be positioned in ${sim}3$ min. ]]> 5 2 216 222 1642 Planning coordination for multiple companies has received much attention from viewpoints of global supply chain management. In practical situations, a plausible plan for multiple companies should be created by mutual negotiation and coordination without sharing such confidential information as inventory costs, setup costs, and due date penalties for each company. In this paper, we propose a framework for distributed optimization of supply chain planning using an augmented Lagrangian decomposition and coordination approach. A feature of the proposed method is that it can derive a near-optimal solution without requiring all of the information. The proposed method is applied to supply chain planning problems for a petroleum complex, and a midterm planning problem for multiple companies. Computational experiments demonstrate that the average gap between a solution derived by the proposed method and the optimal solution is within 3% of the performance index, even though only local information is used to derive a solution for each company. ]]> 5 2 259 274 1303 Dynamic programming, branch-and-bound, and constraint programming are the standard solution principles for finding optimal solutions to machine scheduling problems. We propose a new hybrid optimization framework that integrates all three methodologies. The hybrid framework leads to powerful solution procedures. We demonstrate our approach through the optimal solution of the single-machine total weighted completion time scheduling problem subject to release dates, which is known to be strongly ${cal NP}$-hard. Extensive computational experiments indicate that new hybrid algorithms use orders of magnitude less storage than dynamic programming, and yet can still reap the full benefit of the dynamic programming property inherent to the problem. We are able to solve to optimality all 1900 instances with up to 200 jobs. This more than doubles the size of problems that can be solved optimally by the previous best algorithm running on the latest computing hardware. ]]> 5 2 337 348 661 A key process in assembly of microelectromechanical systems optical switches is of inserting fibers into U-grooves in silicon substrate. Due to positioning errors and dimensional tolerances in components, heavy collision occurs between fibers and the edges of U-grooves during insertion, throwing out fibers from the fiber holder or worse, damaging the components. Typical solutions to the problem involve determining errors using machine vision or force sensors, and then positioning fibers accurately by virtue of high precision multi-axis systems (with submicron repeatability). However, these approaches are costly and difficult to implement. In this paper, we present a low-cost passive assembly method to solve the problem. It utilizes a special flexure-based fixture to regulate high contact forces and accommodate assembly errors. Specifically, we model the problems happening in the process of fiber insertion and characterize the conditions of successful insertion. We then suggest how to design flexural fixtures so that the required insertion conditions can be met. Experimental results show that using such a fixture the fiber assembly can be successfully implemented even if the assembly system's accuracy is lower than 12 $~muhbox{m}$ in $mmb x$ and $mmb y$ axes, and 0.07$^circ$ in theta axis. These requirements are within the reach of most low-cost precision systems. ]]> 5 2 207 215 1356 Most factories depend on skilled workers to test the quality of transmission devices by listening to the sound. In this paper, an intelligent inspection system is proposed to evaluate the quality of transmission devices in place of experts. Since the causes of faults of transmission devices are complex and a defective product might simultaneously have many types of faults, the discrimination process between defective and nondefective products and the classification process of defective products are treated separately in the proposed system. From the acoustic data of operating transmission devices, we extract the feature vectors based on time-frequency analysis and train a neuroclassifier by using the learning vector quantization (LVQ). Furthermore, the genetic algorithm (GA) with floating point (FP) is utilized to select some significant frequencies from the spectra of acoustic data of defective and nondefective products and to make a quality evaluation rule automatically. The defective products are picked up from the automatic production line according to the evaluation rule and the trained neuroclassifier. At last, the self-organizing feature map (SOM) algorithm is used to identify the kinds of defective products. The experimental results show that the proposed intelligent system is able to perform the quality evaluation of transmission devices successfully. ]]> 5 2 361 367 825 Nanomanipulation with atomic force microscopes (AFMs) for nanoparticles with overall sizes on the order of 10 nm has been hampered in the past by the large spatial uncertainties encountered in tip positioning. This paper addresses the compensation of nonlinear effects of creep and hysteresis on the piezo scanners which drive most AFMs. Creep and hysteresis are modeled as the superposition of fundamental operators, and their inverse model is obtained by using the inversion properties of the Prandtl–Ishlinskii operator. Identification of the parameters in the forward model is achieved by a novel method that uses the topography of the sample and does not require position sensors. The identified parameters are used to compute the inverse model, which in turn serves to drive the AFM in an open-loop, feedforward scheme. Experimental results show that this approach effectively reduces the spatial uncertainties associated with creep and hysteresis, and supports automated, computer-controlled manipulation operations that otherwise would fail. ]]> 5 2 197 206 1692 Group elevator scheduling has long been recognized as an important problem for building transportation efficiency, since unsatisfactory elevator service is one of the major complaints of building tenants. It now has a new significance driven by homeland security concerns. The problem, however, is difficult because of complicated elevator dynamics, uncertain traffic in various patterns, and the combinatorial nature of discrete optimization. With the advent of technologies, one important trend is to use advance information collected from devices such as destination entry, radio frequency identification, and sensor networks to reduce uncertainties and improve efficiency. How to effectively utilize such information remains an open and challenging issue. This paper presents the optimized scheduling of a group of elevators with destination entry and future traffic information for normal operations and coordinated emergency evacuation. Key problem characteristics are abstracted to establish a two-level separable formulation. A decomposition and coordination approach is then developed, where subproblems are solved by ordinal optimization-based local search, and top ranked nodes are selectively optimized by using dynamic programming. The approach is then extended to handle up-peak with little or no future traffic information, elevator parking for low intensity traffic, and coordinated emergency evacuation. Numerical testing results demonstrate near-optimal solution quality, computational efficiency, the value of future traffic information, and the potential of using elevators for emergency evacuation. ]]> 5 2 245 258 735 This paper addresses the general single-machine earliness–tardiness problem with distinct release dates, due dates, and unit costs. The aim of this research is to obtain an exact nonpreemptive solution in which machine idle time is allowed. In a hybrid approach, we formulate and then solve the problem using dynamic programming (DP), while incorporating techniques from branch-and-bound (BB). This approach (DP-BB) has been proven to be effective in solving certain types of scheduling problems. We further propose a new adaptation of the approach to a general problem with a nonregular objective function. To address some shortcomings of DP-BB, we also apply a BB approach in which partial dynamic programming dominance (BB-PDP) is exploited. Computational experiments were conducted with randomly generated test instances in order to evaluate the effectiveness of the two approaches. The results clearly showed that our new approaches can solve all the instances with up to 40 jobs and most of the instances with 50 jobs, which outperforms those frequently used approaches in scheduling research. ]]> 5 2 349 360 787 Many organizations are expending enormous efforts to minimize cost and time when developing new products by sharing and reusing distributed design knowledge and information. Multiagent systems provide an ideal mechanism to develop various products efficiently and cost-effectively by integrating distributed design knowledge and information. Product family design entails developing a set of differentiated products around a platform, while targeting individual products to distinct market segments. This paper presents a mathematical model reflecting the tradeoffs inherent in having a platform and introduces a dynamic multiagent system (DMAS) based on negotiation mechanisms to address the model effectively. The negotiation protocol to design a platform is developed using market-based auction mechanisms. In the proposed system, specific design tasks are assigned to agents by decomposing tasks for product family design, and an optimal platform is determined by negotiations between agents. We apply the DMAS to design a platform for a family of power tools. ]]> 5 2 234 244 1199 Problems of inventory control and customer admission control are considered for a manufacturing system that produces one product to meet random demand. Four admission policies are investigated: lost sales, complete backordering, randomized admission, and partial backordering. These policies are combined with an integral inventory control policy, which releases raw items only when an incoming order is accepted and keeps the inventory position (total inventory minus outstanding orders) constant. The objective is to determine the inventory level and the maximum number of backorders, as well as the admission probability that maximize the mean profit rate of the system. The system is modeled as a closed queueing network and its performance is computed analytically. The optimal parameters for each policy are found using exhaustive search and convex analysis. Numerical results show that managing inventory levels and sales jointly through partial backordering achieves higher profit than other control policies. ]]> 5 2 275 288 535 Rather than dealing with the traditional one-dimension bin packing problem to minimize the cost in demand assignments, the flexible demand assignment (FDA) problem studied in this paper considers the balance between revenue and cost. Compared with a number of solution methods in operations research, we solve the FDA problem by three specially designed operators of neighborhood construction for search space—namely, One Bin Repack, Two Bins Repack, and Unpack. Extensive computational results clearly show the superiority of the three proposed operators based on simple local search over the best published results. ]]> 5 2 289 297 592 Cluster tools are widely used as semiconductor manufacturing equipment. While throughput analysis and scheduling of single-cluster tools have been well-studied, research work on multicluster tools is still at an early stage. In this paper, we analyze steady-state throughput and scheduling of multicluster tools. We consider the case where all wafers follow the same visit flow within a multicluster tool. We propose a decomposition method that reduces a multicluster tool problem to multiple independent single-cluster tool problems. We then apply the existing and extended results of throughput and scheduling analysis for each single-cluster tool. Computation of lower-bound cycle time (fundamental period) is presented. Optimality conditions and robot schedules that realize such lower-bound values are then provided using “pull” and “swap” strategies for single-blade and double-blade robots, respectively. For an $M$-cluster tool, we present $O(M)$ lower-bound cycle time computation and robot scheduling algorithms. The impact of buffer/process modules on throughput and robot schedules is also studied. A chemical vapor deposition tool is used as an example of multicluster tools to illustrate the decomposition method and algorithms. The numerical and experimental results demonstrate that the proposed decomposition approach provides a powerful method to analyze the throughput and robot schedules of multicluster tools. ]]> 5 2 321 336 1823 This work intends to deal with the optimal kinematic synthesis problem of parallel manipulators under a unified framework. Observing that regular (e.g., hyper-rectangular) workspaces are desirable for most machines, we propose the concept of effective regular workspace, which reflects simultaneously requirements on the workspace shape and quality. The effectiveness of a workspace is characterized by the dexterity of the mechanism over every point in the workspace. Other performance indices, such as manipulability and stiffness, provide alternatives of dexterity characterization of workspace effectiveness. An optimal design problem, including constraints on actuated/passive joint limits and link interference, is then formulated to find the manipulator geometry that maximizes the effective regular workspace. This problem is a constrained nonlinear optimization problem without explicitly analytical expression. Traditional gradient based approaches may have difficulty in searching the global optimum. The controlled random search technique, as reported robust and reliable, is used to obtain an numerical solution. The design procedure is demonstrated through examples of a Delta robot and a Gough–Stewart platform. ]]> 5 2 223 233 881 This paper addresses the problem of how to navigate a miniature Crawler robot in a typical engineered structure inspection application—aircraft rivet inspection. First, a novel vision-assisted localization algorithm is developed to find the heading and position of the Crawler robot. Second, a new algorithm is developed to solve the path planning problem so that the Crawler robot can navigate through all the rivets. Experimental results validate the localization and path planning algorithms. This inspection system can be extended to other similar engineered structure inspection applications. ]]> 5 2 368 373 816 5 2 C1 C1 37 5 2 C2 C2 41 5 2 C3 C3 37 5 2 C4 C4 32 5 2 374 374 149 5 2 375 375 673 5 2 376 376 606