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Robotics and Automation, IEEE Transactions on

Issue 6 • Date Dec 1990

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Displaying Results 1 - 14 of 14
  • The robot task-sequencing planning problem

    Publication Year: 1990 , Page(s): 760 - 765
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The problem of how to utilize some robot task flexibility characteristics efficiently is addressed. For a given set of robots and a set of tasks which can be accomplished through several alternative sequences of motions and operations, the robot task-sequencing planning problem is to determine the optimal sequence of paths for each robot such that all the tasks are executed with a total minimum cost (e.g. time). A framework and a classification for such types of problems are provided, and one class of problems is studied. The problems are solved according to the proposed decomposition scheme. Special considerations, such as the capacity of the robot end effector and coordination planning among several robots, are included in the algorithms. An example illustrates the problem and the solution View full abstract»

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  • Optimal machine settings of imperfect component production processes for assembly operations

    Publication Year: 1990 , Page(s): 652 - 658
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The present work is motivated by a problem occurring in a fabrication and assembly operation of fuel injectors for automobile engines. The production processes of the individual components to be assembled are imperfect. For a specific machine setting, which can be preset by an operator, the dimensions of the outputs of a component production process are variable. Components can be assembled only if their dimensions are within some given specification limits of each other. The problem of determining the optimal machine settings of two component production processes to maximize the expected outputs of the assembly operations is considered. The properties of the optimal solution are studied, and some numerical examples are presented View full abstract»

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  • Schedule generation and reconfiguration for parallel machines

    Publication Year: 1990 , Page(s): 687 - 696
    Cited by:  Papers (59)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    A methodology for scheduling independent jobs with due dates on identical, parallel machines is presented. The jobs have different levels of importance and various processing times on the machines, and the objective is to minimize the total weighted job tardiness of the schedule. Since the problem is NP hard, the goal is not to obtain the optimal schedule. Rather, an efficient near-optimal algorithm based on Lagrangian relaxation is presented. This approach provides a lower bound on the cost, which can be used as a measure of suboptimality. According to an implementation for a work center at Pratt and Whitney, most schedules generated are within 1% of the optima with reasonable CPU times. Furthermore, the method provides valuable job interaction information, which shop floor management uses to answer `what if' questions, to reconfigure the schedule to accommodate dynamic changes, and to schedule new jobs View full abstract»

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  • Efficient computation of coordinating controls in hierarchical structures for failure-prone multicell flexible assembly systems

    Publication Year: 1990 , Page(s): 659 - 672
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    Production allocation in multicell manufacturing systems is considered. A model is developed for a hierarchical control scheme, where each cell consists of several failure-prone machines for which the time scale of the machine state transitions is comparable to the processing times. The production objective is to track a nonstationary demand as closely as possible when the demand is near or exceeds the capacity of the system. A series of approximations is proposed to obtain a model that is realistic while admitting a tractable solution. To solve the resulting stochastic control problem, a general result is derived on the second-order finite-time (transient) statistics of a continuous-time Markov chain. Simulation results are presented to illustrate the proposed model and control methodology. These results are compared with a myopic linear programming approach View full abstract»

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  • Trajectory planning for coordinated motion of a robot and a positioning table. I. Path specification

    Publication Year: 1990 , Page(s): 735 - 745
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    Coordinating the tool (robot) and workpiece (positioning table) motion in continuous manufacturing processes such as sealing, welding, and laser cutting offers several advantages over the motion of only the tool or workpiece. Better utilization of the speed and workspace characteristics of the two devices and improvement in tracking accuracy at sharp corners in the path are some of the merits of this approach. In coordinated motion, the two devices are simultaneously moved to track a given path, and two strategies are developed for coordinating their motion, where each is dependent on the given path information. The first strategy is applicable to any type of path and resolves the motion by splitting the displacement between any two points on the path into segments moved by the robot and the table. The robot and the table move in opposite directions in this strategy. The second strategy is applicable to sharp cornered paths and resolves the given path into two smooth paths. The first path is a double clothoid curve, whereas the second path is a tangential straight line path. The table executes a local motion around the corner in this strategy, whereas the robot is moved at all times. The uniqueness of this strategy in constructing the original corner path is proved. The proposed strategies are shown to be applicable to other coordinated motion systems View full abstract»

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  • Deadlock avoidance in flexible manufacturing systems with concurrently competing process flows

    Publication Year: 1990 , Page(s): 724 - 734
    Cited by:  Papers (186)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    The concurrent flow of multiple jobs through a FMS can lead to deadlock conditions due to competition for limited resources in the system. The authors develop a Petri net (PN) model of concurrent job flow and dynamic resource allocation in an FMS and define deadlock in terms of transition enabling in the PN model. The problem of deadlock avoidance is addressed by introducing the notion of a restriction policy, which is a feedback policy for excluding some enabled transitions from the current resource allocation alternatives. The authors then present their deadlock avoidance algorithm (DAA) and prove that restricted deadlock can never occur for any resource allocation policy implemented under the DAA restriction policy. The DAA can be implemented easily in real time and is much less restrictive for FMS applications than existing algorithms for deadlock avoidance in computer systems. Application of the DAA is illustrated for three FMS examples: allocation of finite buffer space in a multicell machining facility, collision avoidance in a multirobot assembly cell, and coordination of multiple AGVs on a shop floor View full abstract»

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  • The product cycling problem in systems with uncertain production yields

    Publication Year: 1990 , Page(s): 640 - 651
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    The author addresses a production planning problem for a single machine producing multiple parts, where the yield rate (fraction acceptable) for each part may be uncertain, and the production policy is to cycle through the set of parts. She analyzes a simplified version of the problem that, although still quite complex, becomes solvable as a result of several properties that are demonstrated. The major simplifying assumption is that inventory for each product is zero when its production run begins. A procedure with a fixed-point flavor is developed to determine the cycle duration and the associated production policies (yield loss adjustment factors). An iterative scheme is suggested to incorporate heuristically the impact of the yield adjustment experiments; however, it is found that in most situations, only a single iteration is needed. The resulting plan is viewed as a basis for specifying targets that provide guidelines for controlling the system while considering long-term aggregate tradeoffs. In particular, the model of the planning problem captures both the effect of setup times and, at an aggregate level, the impact of yield uncertainty (not just average yields) on capacity utilization View full abstract»

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  • Performance evaluation of automated manufacturing systems using generalized stochastic Petri nets

    Publication Year: 1990 , Page(s): 621 - 639
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1528 KB)  

    Generalized stochastic Petri net (GSPN) modules are used as basic building blocks to model and analyze complex manufacturing systems. This modular approach facilitates model construction and helps manage the complexity of modeling large manufacturing systems. The structural analysis ensures that the model is live and bounded, which guarantees that the equivalent Markov chain (MC) is ergodic. The temporal analysis is used to derive performance measures such as average production rates and average in process inventories. The main advantage of Petri nets (PNs) over MCs is that the number of places and transitions increases only slightly as the manufacturing system complexity increases, whereas the number of states in the MC increases exponentially. In addition, there is no need to enumerate all the possible states manually since they are automatically generated from the GSPN model. As a result, PN models can still be easily obtained for complicated interconnected systems. The straightforward application of this approach is demonstrated and reviewed for several manufacturing case studies. For serial transfer lines it is proven that this modular approach results in live and bounded GSPN models. Comparisons are made with deterministic and reduced state-space models. Examples containing as many as 9614 states are presented View full abstract»

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  • Hybrid hierarchical scheduling and control systems in manufacturing

    Publication Year: 1990 , Page(s): 673 - 686
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1244 KB)  

    Some experiments on the integration of algorithmic techniques with knowledge-based ones are discussed. Two case studies are presented: an FMS cell and a press shop. It was found that the algorithmic procedures developed for production scheduling resulted in limiting the ability to cope with the complexity of the real manufacturing world. The scheduling problem, seen as a constraint satisfaction problem, can be approached with rule-based techniques. Nevertheless, algorithmic techniques are found to be valuable for their efficiency and ability to deal with aggregated data. This ability is fundamental for an efficient implementation of hierarchical control systems in general and in the manufacturing context in particular. This suggests that the integration of rule-based techniques with algorithmic ones can increase the efficiency of searching in the space of possible solutions. The ability to deal with aggregated data can have little value when detailed real-time operation scheduling is needed. In this case, simple dispatching rules are often used, and sophisticated operations research methods are not used. In such a dynamic situation, a purely-rule based approach may be more suitable View full abstract»

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  • Part routing in flexible assembly systems

    Publication Year: 1990 , Page(s): 697 - 705
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (828 KB)  

    The problem of part routing and scheduling in flexible manufacturing systems is considered with the goal of increasing the throughput. The flexible system considered is strongly characterized by the inclusion of assembly among the manufacturing operations to be performed on a mix of part batches. In particular, the logic structure of some basic decision problems is indicated through a set of combinatorial models. Two basic assembly problems characterized by batches of large and small size, respectively, are analyzed View full abstract»

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  • Deadlock prevention and deadlock avoidance in flexible manufacturing systems using Petri net models

    Publication Year: 1990 , Page(s): 713 - 723
    Cited by:  Papers (139)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    Deadlocks constitute an important issue to be addressed in the design and operation of FMSs. It is shown that prevention and avoidance of FMS deadlocks can be implemented using Petri net models. For deadlock prevention, the reachability graph of a Petri net model of the given FMS is used, whereas for deadlock avoidance, a Petri-net-based online controller is proposed. The modeling of the General Electric FMS at Erie, PA, is discussed. For such real-world systems, deadlock prevention using the reachability graph is not feasible. A generic, Petri-net-based online controller for implementing deadlock avoidance in such real-world FMSs is developed View full abstract»

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  • Effects of flexibility through set-up time reduction and expediting on integrated production-distribution systems

    Publication Year: 1990 , Page(s): 609 - 620
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    A model of an integrated production-distribution system is applied to the question of the impact of flexibility (setup time reduction and expediting) in manufacturing on stock levels throughout the supply chain. The analysis is based on a three-echelon supply chain model consisting of three locations: a factory work center, a finished-goods (FG) stockpile, and a retailer stocking point. One product is manufactured and distributed. Two model variations are introduced to represent systems in which the FG stockpile may or may not expedite in the event of a stockout. The ability of the factory to expedite represents the second aspect of flexibility considered. Since expedited orders interrupt the processing of replenishment orders, production scheduling is directly linked to the inventory-stocking policies at the FG stockpile. FG policies are, in turn, affected by stock control at the retailer. The results indicate that the cost of holding inventory will be less when manufacturing has low setup times and that the gains from implementing an expediting system are realized only in high-setup-time facilities View full abstract»

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  • Optimal scheduling control of a flexible machine

    Publication Year: 1990 , Page(s): 706 - 712
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    A flexible machine that processes a set of different part types is considered. Each part type has its own Poisson arrival process, general processing requirement, and a given delay (flow time) constraint. The problem is to find an optimal control that schedules the machine among the part types on a real-time basis in order to minimize a cost function of the flow times and meet all the constraints. The cost function is quite general, and it requires only that the marginal costs can be ordered among the part types. Based on polymatroid theory, an optimal control is identified that partitions the part types into several groups and applies a priority rule among the groups. Within each group, the optimal control is an appropriate randomization among priority rules. An efficient algorithm is developed to characterize the optimal control completely View full abstract»

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  • Trajectory planning for coordinated motion of a robot and a positioning table. II. Optimal trajectory specification

    Publication Year: 1990 , Page(s): 746 - 759
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (996 KB)  

    For pt.I see ibid., p.735-45 (1990). A robot and positioning table system is a kinematically redundant system with respect to planar motion. Two strategies were developed in pt.I to resolve this redundancy and to specify path shapes that make the best utilization of the workspace and speed characteristics of the two devices. In this part, a one-variable dynamic programming approach is developed to obtain a near-minimum time and/or energy trajectory of the two devices. The developed strategies were studied using this path-planning algorithm on a model of a 3 d.o.f. robot and a two-axis linear positioning table for a variety of path shapes and constraints. In addition, experiments were performed in a typical workcell to show the feasibility of the developed strategies. In moving the two devices in opposite directions, the least travel time is obtained when the original path is resolved more in favor of the faster device, whereas the quality of resultant motion is dependent on the controller performance of each device View full abstract»

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Aims & Scope

This Transactions ceased production in 2004. The current retitled publications areIEEE Transactions on Automation Science and Engineering and IEEE Transactions on Robotics.

Full Aims & Scope