A Benchmarking Service for the evaluation and comparison of scheduling techniques

Abstract

Scheduling decisions constitute the last decision-making phase of the production planning and control process. From the industrial side, the adoption of highly reactive and efficient scheduling and control systems strongly affects the level of productivity and utilization of a manufacturing system, particularly under the pressure of shortened product cycles, reduced batch sizes and a broader variety of items to be produced. In the meanwhile, from the research side, there has been a considerable amount of works done in the area of manufacturing systems control, even if they still remain “unheard voices” in industry. Hence, in the scheduling world there is a risk of miscommunication between academics and industrial users.

Aim of the paper is to provide a comprehensive view of the rationale, the conceptual model, the development efforts and first applicative experiences of the Benchmarking Service, a research initiative which has been carried out within the activities of the Special Interest Group on Benchmarking and Performance Measurement of the IMS Network of Excellence. In particular, the paper details the PMS-ESS conceptual framework developed for assessing the level of quality of a scheduling solution in terms of efficiency, robustness and flexibility.

Introduction

Competitive firms are operating today in global and worldwide markets. Manufacturers are experiencing a lumpy market demand for their products, with ever shorter requested lead times and order quantities as well as frequent changes in product specifications. In this context, within the production planning and control process, scheduling plays undoubtedly a critical role. It is the final temporal decision-making phase where industrial managers have to act for fixing any short noticed variations preserving at the same time expected medium-term efficiency performance.

According to Kempf et al. [6], the most general definition of a scheduling problem is that of “assigning scarce resources to competing activities over a given time horizon to obtain the best possible system performance”. Referring specifically to factory scheduling, the resources are machines and workforce, and the competing activities are jobs that require processing on the resources.

Several scheduling approaches exist, from the traditional off-line scheduling systems, which elaborate a production plan (e.g. according to static rules and algorithms) for a specific plan period, to on-line production scheduling systems, which are intrinsically able to modify an existing schedule or regenerate a completely new one for managing upcoming events which could alter the original plan.

Despite the flourish of heterogeneous proposals, a dichotomy is actually affecting the world of scheduling. Researchers are often detached from industrial reality, proposing answers to simple examples and toy cases. On the contrary, practitioners have clear difficulties in explaining their requirements and exploiting the opportunities which could come out from the industrial exploitation of the new advanced scheduling approaches.

The main purpose of the present paper is to provide a comprehensive view of a research initiative, carried out in the last years within the activities of the IMS-NoE Special Interest Group (SIG) on Benchmarking and Performance Measurement of Production Scheduling Systems. The research community involved in the SIG has been mainly interested in promoting the adoption of a Benchmarking methodology for testing and evaluating scheduling solutions in order to identify the best solution for one industrial problem.

This idea has turned into reality with the instantiation of the Benchmarking Service within the IMS-NoE web site [7], freely accessible to all the registered members. The available prototype of the Benchmarking Service is a web-based arena, where production systems would be described and different production scheduling policies would be evaluated and compared under a common simulation environment.

The paper is organized as follows: Section 2 summarizes the rationale behind the developed Benchmarking Service; Section 3 introduces the framework developed for supporting the description of a test case; Section 4 explores the main requirements of the evaluation of a scheduling system; Sections 5 The proposed framework (PMS-ESS), 6 Application of the PMS-ESS illustrate the proposed PMS-ESS with an applicative example; Section 7 provides the main conclusions of the paper.