Cyclic Steady State Refinement: Multimodal Processes Perspective

Cyclic scheduling problems arise in a variety of transportation applications and service domains. Within the class of those problems we can identify situations where there is need to make use of different modes of transportation. What is of particular interest in this paper is the design of a class of multimodal cyclic processes (MCP) for production engineering and supply chains. The paper presents a new modeling framework enabling to prototype and evaluate multimodal processes while comparing their cyclic steady states. A way in which the multimodal processes encompass the behavior of supporting them concurrently flowing cyclic processes (SCCP) is discussed in terms of constraints satisfaction problem. Possible implementations are illustrated on example of the flexible manufacturing system operation.KeywordsCyclic processesCyclic schedulingConcurrent processesMultimodal processesState spaceDeclarative modelingDispatching rules

In this chapter, we deal with the cyclic scheduling problem usually observed in the FMS producing multi-type parts where the AGVS plays a role of a material handling system. Finding the conditions guaranteeing the AGVs deadlock-free and collision-free movement policy is the aim of this work. The AGVs co-sharing the common parts of the transportation route while executing repetitive processes, can be modeled in terms of Cyclic Concurrent Process Systems (CCPSs). The chapter suggests a novel approach for schedulability analysis employing the declarative modeling. In turn, the schedulability analysis for a given CCPS answers the question whether a cyclic schedule exists or not. A reference model of constraint satisfaction cyclic scheduling problem shows that unschedulability can be caused by a relation among an initial state and dispatching rules selected. The sufficient conditions guaranteeing CCPS schedulability are discussed and the recursive approach to their designing is proposed. Possible implementations are illustrated on example of the flexible manufacturing system operation.

The paper concerns cyclic scheduling problems arising in a Multimodal Transportation Network (MTN) in which several unimodal networks (AGVs, hoists, lifts, etc.) interact with each other via common shared workstations as to provide a variety of demand-responsive material handling operations. The material handling transport modes provide movement of work-pieces between workstations along their manufacturing routes in the MTN. The goal is to provide a declarative framework enabling to state a constraint satisfaction problem aimed at AGVs fleet match-up scheduling taking into consideration assumed itineraries of concurrently manufactured product types. In that context, treating the different product types as a set of cyclic multimodal processes is the main objective to discuss the conditions sufficient for FMS rescheduling imposed by production orders changes. To conclude, the conditions sufficient for an FMS rescheduling imposed by changes of production orders treated as cyclic multimodal processes are stated as the paper’s main contribution.

Improved ODE integrator and mass transfer approach for simulating a cyclic adsorption process

A declarative model aimed at reachability-driven refinement of the multimodal networks (MNs) cyclic steady state space is proposed. The concept of multimodal processes executed in goods/passengers transportation or data transmission networks where several closed loop structure subnetworks interact each other via distinguished subsets of common shared hubs as to provide a variety of demand-responsive goods or data transportation/handling services is employed. Multimodal processes throughput depends on their cycle time that is on cycle time reachable in considered MN. Therefore, searching for the MN’s cyclic steady state behavior the following question is considered: Is the cyclic steady state space reachable in the given network structure? The declarative approach employed makes it possible to evaluate the reachability of cyclic behaviors on a scale that reflects real practice.

Some complexity results in cyclic scheduling

Approximation of a PSA process based on an equivalent continuous countercurrent flow process: Blow-up and blow-down representation

Chapter 1 - Introduction

Improved method to converge pressure equalization steps when simulating a cyclic adsorption process

The paper treats about a grid-like topology of different means of transport acting in mesh-like streets network in which several modes interact each other via common shared hubs (i.e. stops, interchange stations, cross-platforms, etc.) as to provide mass customized passenger services, tailored to each travel destination. In that context, a grid-like layout of various transport modes such as tram, bus, train, subway where passenger flows are treated as multimodal processes can be seen as a real-life example of the considered case. The goal is to provide a declarative model representation enabling to state a constraint satisfaction problem aimed at multimodal transportation processes scheduling aimed at dedicated flows of passengers service. The main objective is to provide conditions guaranteeing the right match-up of local cyclic acting tram/bus/metro line schedules to a given passenger flow itineraries.

A multi-job cyclic scheduling problem for an automated job-shop-type manufacturing system was analyzed. In the cyclic scheduling problem, an optimum schedule is a non-idle schedule, where a bottleneck machine produces jobs without idle time in the steady state. A dividing method of the jobs was introduced and the job output interval in the steady state was clarified. A lower bound on the buffer capacity was obtained to construct a non-idle schedule.

Converging to periodic schedules for cyclic scheduling problems with resources and deadlines

In this paper, we address some issues on the interface of buffer design and cyclic scheduling decisions in a multi-product deterministic flow line. We demonstrate the importance of the above interface for the throughput performance of the flow line. In particular, we point out that the use of sequence-independent information, such as workload distribution and variability in processing times among stations, is not adequate to decide the optimal buffer configuration of the flow line. We formulate the buffer design problem for a fixed sequence of jobs as a general resource allocation problem, and suggest two effective heuristics for its solution. For the simultaneous buffer design and cyclic scheduling problem, we suggest an iterative scheme that builds on the effectiveness of the above heuristics. One of the side results of our extensive computational studies on this problem is that the general guidelines of buffer design in single-product flow lines with stochastic processing times are not directly transferable to the multiproduct deterministic flow line environment.

Cyclic Scheduling Problems with Linear Precedences and Resource Constraints

This paper proposes a common and individual (CnI) feature extraction-based process monitoring (PM) method for tracking the operating performance and product quality of processes with multiple operating modes. Different from traditional methods that separately develop PM models concerning only the individual feature of each mode data, the new method seeks to build the PM model simultaneously from all mode data, including to acquire the common subspace that captures the common feature behind different modes, and the individual subspace that reflects the unique feature of each mode. The newly proposed framework is achieved using the conventional principal component analysis (PCA) and partial least squares (PLS) based methods. The resulting CnI-PCA-based operating performance monitoring method and CnI-PLS-based product quality monitoring method are applied to the typical multimode finishing mill process (FMP) where common configuration for all steel products and individual setting for each steel are existing. Finally, the practical application result shows that the proposed method can be preferable to detect and identify different faults in the multimode FMP.