Applying Iterative Flattening Search to the Job Shop Scheduling Problem with Alternative Resources and Sequence Dependent Setup Times

This paper tackles a complex version of the Job Shop Scheduling Problem (JSSP) that involves both the possibility to select alternative resources to activities and the presence of sequence dependent setup times. The proposed solving strategy is a variant of the known Iterative Flattening Search (IFS) metaheuristic. This work presents the following contributions: (1) a new constraint-based solving procedure produced by means of enhancing a previous JSSP-solving version of the same metaheuristic; (2) a new version of both the variable and value ordering heuristics, based on temporal flexibility, that capture the relevant features of the extended scheduling problem (i.e., the flexibility in the assignment of resources to activities, and the sequence dependent setup times); (3) a new relaxation strategy based on the random selection of the activities that are closer to the critical path of the solution, as opposed to the original approach based on a fully random relaxation. The performance of the proposed algorithm are tested on a new benchmark set produced as an extension of an existing well-known testset for the Flexible Job Shop Scheduling Problem by adding sequence dependent setup times to each original testset\u27s instance, and the behavior of the old and new relaxation strategies are compared

Supporting Increment Planning Processes within the ULISSE Framework

ULISSE is an EU project whose aim is data valorization around the ISS experiments. The ULISSE software platform is endowed with a number of additional services to improve both data production and data analysis. This paper describes the Planning and Scheduling Service, a module developed to support functions of data production around the ISS activities and integrated in the ULISSE platform. Its current use to support work for the Fluid Science Laboratory facility is also shown and fully analyzed from design to application service delivery

Continuous Planning and Execution with Timelines

Planning systems need to be endowed with some additional features to cope effectively with execution: e.g., the ability to keep the plan database updated with respect to the actual feedbacks provided by the controlled system, to mention but one. In this paper, we identify a set of noteworthy planning and execution open issues relatively to the timeline-based planning approach. We address those issues presenting a domain independent deliberative system, implemented on top of the APSI-TRF, the A PSI Timeline-based Representation Framework, extended with timeline dispatching and execution-supervision capabilities so as to allow continuous planning and closed-loop re-planning activities. Some ongoing research directions are also briefly introduced

Job Shop Scheduling with Routing Flexibility and Sequence-Dependent Setup Times

This paper presents a meta-heuristic algorithm for solving a job shop scheduling problem involving both sequence dependent setup-times and the possibility of selecting alternative routes among the available machines. The proposed strategy is a variant of the Iterative Flattening Search (IFS ) schema. This work provides three separate results: (1) a constraint-based solving procedure that extends an existing approach for classical Job Shop Scheduling; (2) a new variable and value ordering heuristic based on temporal flexibility that take into account both sequence dependent setup-times and flexibility in machine selection; (3) an original relaxation strategy based on the idea of randomly breaking the execution orders of the activities on the machines with a activity selection criteria based on their proximity to the solution\u27s critical path. The efficacy of the overall heuristic optimization algorithm is demonstrated on a new benchmark set which is an extension of a well-known and difficult benchmark for the Flexible Job Shop Scheduling Problem

Exploiting Iterative Flattening Search to Solve Job Shop Scheduling Problems with Setup Times

No abstract availableThis paper presents a heuristic algorithm for solving a jobshop scheduling problem with sequence dependent setup times (SDST-JSSP). This strategy, known as Iterative Flattening Search (IFS), iteratively applies two steps: (1) a relaxation-step, in which a subset of scheduling decisions are randomly retracted from the current solution; and (2) a solving-step, in which a new solution is incrementally recomputed from this partial schedule. The algorithm relies on a core constraint-based search procedure, which generates consistent orderings of activities that require the same resource by incrementally imposing precedence constraints on a temporally feasible solution. Key to the effectiveness of the search procedure is a conflict sampling method biased toward selection of the most critical conflicts. The efficacy of the overall heuristic optimization algorithm is demonstrated empirically on a set of well known SDST-JSSP benchmarks

APSI-based Deliberation in Goal Oriented Autonomous Controllers

This paper describes a timeline-based, domain independent deliberative layer, based on E SA APSI technology, deployed in the context of the Goal Oriented Autonomous Controller (G OAC) project. In particular the paper describes a new controller composed by (1) a planning module that exploits the timeline-based approach provided by the APSI - TRF and is able to model and solve planning problems, (2) a module that dispatches planned timelines, supervises their execution status and entails continuous planning and re-planning. An example will illustrate both modules at work

Constraint-based Scheduling for Closed-loop Production Control in RMSs

Reconfigurable manufacturing systems (RMS) are conceived to operate in dynamic production contexts often characterized by fluctuations in demand, discovery or invention of new technologies, changes in part geometry, variances in raw material requirements. With specific focus on the RMS production aspects, the scheduling problem implies the capability of developing plans that can be easily and efficiently adjusted and regenerated once a production or system change occurs. The authors present a constraint-based online scheduling controller for RMS whose main advantage is its capability of dynamically interpreting and adapting to production anomalies or system misbehavior by regenerating on-line a new schedule. The performance of the controller has been tested by running a set of closed-loop experiments based on a real-world industrial case study. Results demonstrate that automatically synthesizing plans and recovery actions positively contribute to ensure a higher production rate

An integrated Constraint-based, power Aware control system for Autonomous rover Mission operations

This paper aims at describing an integrated power-aware, model-based autonomous control architecture for planetary rover-based mission operations synthesized in the context of a Ph.D. program on the topic "Autonomy for Interplanetary missions" funded and supported by ESA. The proposed controller implements a single Sense-Act-Plan (SPA) closed-execution loop to safely command the robot activities considered in the context of a specific key mission scenario. Both highly decision making capabilities and a flexible execution process are the two key features on which the control system is grounded. Furthermore, target execution capabilities, specially those that allow to flexibly keeping pace with temporal and power-related contingencies that might threaten the whole schedule execution attainment, are demonstrated through the integration with the ESA\u27s 3DROV planetary rover system simulator

Polyunsaturated fatty acids in fishes increase with total lipids irrespective of feeding sources and trophic position

Trophic transfer and retention of dietary compounds are vital for somatic development, reproduction, and survival of aquatic consumers. In this field study, stable carbon and nitrogen isotopes, and fatty acids (FA) contents in invertebrates and fishes of pre-alpine Lake Lunz, Austria, were used to (1) identify the resource use and trophic level of Arctic charr (Salvelinus alpinus), pike (Esox lucius), perch (Perca fluviatilis), brown trout (Salmo trutta), roach (Rutilus rutilus), and minnow (Phoxinus phoxinus) and (2) examine how polyunsaturated fatty acids (PUFA; i.e., omega-3 and -6 PUFA) are related to total lipid status, littoral-pelagic reliance, and trophic position. Stable isotope data suggest that pike, perch, and minnow derived most of their energy from littoral resources, but minnows differed from pike and perch in their trophic position and PUFA composition. The co-occurrence of cyprinids, percids, and pike segregated these fishes into more lipid-rich (roach, minnow) and lipid-poor (pike, percids) species. Although the relatively lipid-poor pike and percids occupied a higher trophic position than cyprinids, there was a concurrent, total lipid-dependent decline in omega-3 and -6 PUFA in these predatory fishes. Results of this lake food-web study demonstrated that total lipids in fish community, littoral-pelagic reliance, and trophic position explained omega-3 and -6 PUFA in dorsal muscle tissues. Omega-3 and -6 PUFA in these fishes decreased with increasing trophic position, demonstrating that these essential FAs did not biomagnify with increasing trophic level. Finally, this lake food-web study provides evidence of fish community-level relationship between total lipid status and PUFA or stable isotope ratios, whereas the strength of such relationships was less strong at the species level.Peer reviewe