Balancing earliness and tardiness within workload control order release: an assessment by simulation

Most Workload Control literature assumes that delivery performance is determined by tardiness related performance measures only. While this may be true for companies that directly deliver to end-customers, for make-to-stock companies or firms that are part of supply chains, producing early often means large inventories in the finished goods warehouse or penalties incurred by companies downstream in the supply chain. Some earlier Workload Control studies used a so-called time limit, which constrains the set of jobs that can be considered for order release, to reduce earliness. However, recent literature largely abandoned the time limit since it negatively impacts tardiness performance. This study revisits the time limit, assessing the use of different adaptive policies that restrict its use to periods of either low or high load. By using a simulation model of a pure job shop, the study shows that an adaptive policy allows to balance the contradictory objectives of delaying the release of orders to reduce earliness and to release orders early to respond to periods of high load as quick as possible. Meanwhile, only using a time limit in periods of high load was found to be the best policy.

Workload Control and Order Dispatching Rules

The purpose of this study is to choose an order dispatching rule and measure the work-in-process and lead-time in the production process of a conveyor chain manufacturer. The main strategic issue for the manufacturer is dependability, which requires meeting deadlines and managing internal lead-times. The study integrates two techniques, workload control (WLC) and an analytical hierarchy process (AHP), respectively systems for production planning and control, and multi-criteria decision support, both widely used in handling manufacturing strategic issues. The research method is a field experiment. Supported by the AHP and according to strategic criteria, practitioners selected the early due date rule (the order with the closest due date comes first) to release 231 orders. Then, employing a methodology designed to support WLC applications, the study measured key parameters that provide information regarding the overall performance of the manufacturer, the input rate, work-in-process, lead-time, throughput performance, and the level of safety stock. Using the model and a graphical tool derived from queuing theory, the throughput diagram, the study provides evidence that, although the manufacturing process is satisfactorily balanced and achieves acceptable performance, the level of safety stock is small and should be increased to prevent starvation on the shop floor.

Guaranteeing Timely Response to Changes of Monitored Objects by Assigning Deadlines and Periods to Tasks

Timely response to changes of monitored objects is the key to ensuring the safety and reliability of cyber-physical systems (CPSs). There are two kinds of tasks in CPSs: update tasks and control tasks. Update tasks are responsible for updating the data in the system based on the state of the objects they monitor. Control tasks are responsible for making decisions based on the data in the system. The response time of the system to the change of a monitored object consists of two parts: the time taken by update tasks to reflect the change to the system, and the time taken by control tasks to make decisions according to the data in the system. Deadlines and periods of update tasks and control tasks directly affect the response time. Reasonable deadline and period assignment is the key to ensuring timely response to the changes of monitored objects. In this paper, we study the deadline and period assignment in CPSs. To the best of our knowledge, all existing work only focuses on the deadline and period assignment for update tasks with the goal of ensuring the freshness of the data in CPSs, and this is the first study focusing on the deadline and period assignment for both update tasks and control tasks with the goal of ensuring timely response to the changes of monitored objects. A new problem about response time control and system workload control is defined in this paper. Two deadline and period assignment methods are proposed to solve the defined problem. All the proposed methods can be used in the CPSs adopting the earliest deadline first (EDF) scheduling method. Experiments with randomly generated tasks are conducted to evaluate the performance of the proposed methods in terms of acceptance ratio and execution efficiency.

Labor flexibility integration in workload control in Industry 4.0 era

The paradigm shift toward Industry 4.0 is facilitating human capability, and at the center of the research are the workers—Operator 4.0—and their knowledge. For example, new advances in augmented reality and human–machine interfaces have facilitated the transfer of knowledge, creating an increasing need for labor flexibility. Such flexibility represents a managerial tool for achieving volume and mix flexibility and a strategic means of facing the uncertainty of markets and growing global competition. To cope with these phenomena, which are even more challenging in high-variety, low-volume contexts, production planning and control help companies set reliable due dates and shorten lead times. However, integrating labor flexibility into the most consolidated production planning and control mechanism for a high-variety, low-volume context—workload control—has been quite overlooked, even though the benefits have been largely demonstrated. This paper presents a mathematical model of workload control that integrates labor flexibility into the order review and release phase and simulates the impact on performance. The main results show that worker transfers occur when they are most needed and are minimized compared to when labor flexibility is at a lower level of control—shop-floor level—thus reducing lead time.

Technical staff structure, planning methods, methodological practices and load management in soccer (Estructura de los cuerpos técnicos, métodos de planificación, prácticas metodológicas y gestión de la carga en fútbol)

Soccer performance depends on several interrelated factors regarding technical, tactical, physical and psychological areas. Over the last decades there was an increase in match congestion. The increased match frequency and the associated injury risk have highlighted the importance of physical condition, increasing the need to implement new training methodologies with a special focus on load and fatigue management, as well as non-specific complementary training. The main objective of this study was to provide information on the structure and characteristics of the technical staffs, the methodological training practices, as well as the workload and fatigue control methods used in soccer, examining possible differences based on gender, category and competitive level. 190 soccer teams from 20 different countries participated in the study, by answering a survey. The results reveal that there are differences in the structure of the technical staff, the planning models, the methodology and the workload control depending on the category and the competitive level. Gender only appears as a discriminating variable, in relation to the most used complementary training contents. The weekly microcycle is the preferred planning model (80.89%), regardless the competitive level. However, in lower categories, medium and long term periodization are also used (23.80%). The weekly volume of complementary training increases as category (p=0.000) and competitive level (p=0.000) does. Strength training is the most used non-specific content (84.89%). However, its importance is reduced in lower categories (38.5%). Load and fatigue control are only extended among teams of superior category (p=0.000) and competitive level (p=0.000). Resumen. El rendimiento en fútbol depende de varios factores interrelacionados entre los que encontramos las áreas técnica, táctica, física y psicológica. Durante las últimas décadas ha existido un aumento en la congestión de partidos. La mayor frecuencia de partidos y el riesgo de lesión asociado han puesto de manifiesto la importancia de la condición física, aumentando la necesidad de implementar nuevas metodologías de entrenamiento con especial énfasis en el manejo de la carga y la fatiga, así como entrenamientos complementarios. El objetivo principal de este estudio fue brindar información sobre la estructura y características de los cuerpos técnicos y las prácticas metodológicas de entrenamiento, así como los métodos de control de la carga de trabajo y la fatiga utilizados en el fútbol, ​​examinando posibles diferencias por género, categoría y nivel competitivo. 190 equipos de fútbol de 20 países diferentes participaron en el estudio, respondiendo a una encuesta. Los resultados revelan que existen diferencias en la estructura de los cuerpos técnicos, los modelos de planificación, la metodología y el control de la carga de entrenamientos y partidos según la categoría y el nivel competitivo. El género solo aparece como variable discriminante en relación con los contenidos complementarios de entrenamiento más utilizados. El microciclo semanal es el modelo de planificación preferido (80.89%), independientemente del nivel competitivo. Sin embargo, en categorías inferiores también se utiliza la periodización a medio y largo plazo (23.80%). El volumen semanal de entrenamiento complementario aumenta a medida que lo hace la categoría (p<.001) y el nivel competitivo (p<.001). El entrenamiento de fuerza es el contenido de entrenamiento complementario más utilizado (84.89%). Sin embargo, su importancia se reduce en categorías inferiores (38.5%). El control de la carga y la fatiga solo se extiende entre equipos de categoría y nivel competitivo superior (p<.001).

Use of workload control in production planning and control: modeling on a simulation software

This paper aims at presenting a structure of implementation of the Workload Control (WLC) approach on a commercial discrete event simulation software by comprehensively demonstrating how to construct and simulate this approach. This research was developed considering the lack of studies fully describing this implementation on this kind of software, which hinders the dissemination and use of the WLC approach by managers. Initially, the logic was developed on a dedicated and structured language and then converted to the simulation software. A detailed description of the WLC implementation contributes to the business domain by facilitating its replication and application in other manufacturing environments, reducing the project time needed to develop the base model and allowing managers and/or researchers to focus directly on the adjustments of the model to the environment being modeled. In the academic domain, this paper addresses a gap in the WLC literature concerning the lack of tutorials for simulation and the lack of information, in the existing papers, regarding the development of the computational model.