Beth Plott

Using simulation to analyze supply chains

Supply chain management, the management of the flow of goods or services from materials stage to the end user, is a complex process because of the level of uncertainty at each stage of the supply chain. Computer simulation, because it can be applied to operational problems that are too difficult to model and solve analytically, is an especially effective tool to help analyze supply chain logistical issues. While most engineers have had some exposure to the tools and technology of computer modeling and simulation, the use of simulation for supply chain analysis has not been prevalent until recently. The software tool, Supply Solver, was developed in an effort to provide supply chain solutions using simulation as the foundation. The goal is to show how discrete-event simulation is used to analyze supply chain processes. The paper also demonstrate what some of the considerations are in using Supply Solver to help solve supply chain design problems.

Predicting nuclear power-plant operator performance using discrete event simulation

A study was conducted to evaluate the use of discrete event simulation (DES) to predict human performance in a nuclear power plant control room environment. Computer simulation models of two disturbance scenarios were built using a simulation software program, Micro Saint. In parallel, data were also collected at a full-scope training simulator at the Halden man-machine laboratory (HAMMLAB) in Halden, Norway, using crews of commercial nuclear power plant operators from the Loviisa nuclear power plant in Loviisa, Finland. Comparisons were made between predicted operator performance data generated by the simulation models and crew performance in the HAMMLAB experiment to determine the degree of agreement between the simulated data and the data from operators. The models were then used to extrapolate advanced control room conditions and alarm systems that were not tested in the HAMMLAB experiment. This report summarizes these findings and provides recommendations for improvements to the DES approach for use by a regulatory agency.

Discrete event simulation as a tool to determine necessary nuclear power plant operating crew size

There are not always sufficient resources or time available to identify human factors issues early enough for development of detailed technical bases using empirical experimentation with human subjects. Consequently, analytical approaches are needed to augment the experimental approach for human factors regulatory decision making at the US Nuclear Regulatory Commission. One analytical approach, computer modeling of human performance, is being investigated by the NRC Office of Nuclear Regulatory Research. As an example of the types of supporting research required, we discuss two specific studies pertaining to the use of Micro Saint, a discrete event simulation package, as a means of evaluating the effects of crew size on safety in a nuclear power plant setting. Both studies provided data that permit an evaluation of the practicality and validity of using models built in Micro Saint for the specific purpose of studying staffing issues, as well as the value of modeling of human performance in general.

CoHOST- Computer Simulation Models to Investigate Human Performance Task and Workload Conditions in a U.S. Army Heavy Maneuver Battalion Tactical Operations Center

A multi-year effort was conducted to investigate the impact on human cognitive and physical performance capabilities, which the introduction of a new Army command and control vehicle with modernized digital communications systems would have. This was a joint effort by the Human Research and Engineering Directorate of the U.S. Army Research Laboratory in partnership with the Directorate of Force Developments at the U.S. Armor Center and School at Fort Knox, Kentucky, and the U.S. Army Operational Test and Evaluation Command at Alexandria, Virginia. Literature searches and background investigations were conducted, and a model architecture based on a taxonomy of human performance was developed. A computer simulation design and methodology was implemented with these taxonomic-based descriptors of human performance in the military command and control domain, using a commercially available simulation programming language. A series of computer models called Computer modeling of Human Operator System Tasks (CoHOST) was written and results were developed that suggest that automation alone does not necessarily improve human performance.

Computer Modeling of a Nuclear Power Plant Operating Crew to Aid in Analysis of Crew Size Issues

An analytical approach to addressing the implications of nuclear power plant shift sizing is needed as an augmentation to the classical empirical approach. The research reported in this paper was to evaluate the feasibility and validity of one potential analytical approach as a means of evaluating the consequences of crew reduction on crew performance in a nuclear power plant setting. The approach selected for analysis was task network modeling and simulation using a tool named Micro Saint. Task network modeling allows the human factors engineer to extend the information from a task analysis and generate a computer simulation of crew performance that can predict critical task times and error rates. Through modeling, the current and proposed processes can be evaluated and analyzed in order to understand, identify, and test opportunities for process improvement or reengineering. For this effort, models of a conventional nuclear power plant during four extremely demanding scenarios were developed. Task analysis and timing data were collected at the Imatran Voima Nuclear Power Plant at Loviisa, Finland. The task analyses were collected over a two week period by interviewing reactor operators, reviewing procedures, and conducting walk-throughs. We then refined the models and incorporated workload modeling constructs. At the completion of the modeling effort, the models were executed and the data collected were used to predict crew performance in varying staffing conditions.

Use of Discrete Event Simulation to Model Human Performance

For the past twenty years, Micro Saint simulation software has been helping the military and other commercial companies answer human performance related questions. Micro Saint Sharp, the next generation Micro Saint simulation tool, includes the ability to allow the user to add built-in parameters and reports that are specifically related to human performance modeling. With a well-designed model, users can easily represent who the operators are, what functions and tasks they perform, what visual, auditory, cognitive, and psychomotor demands are placed on them, and what their utilization is. There are a number of user-defined reports that can be generated based on the simulation execution. This demonstration will provide an overview of Micro Saint Sharp and present some of its new human performance modeling capabilities.

Staffing Levels: Methods for Assessing Requirements

Technological innovations and the increasing role of automation in advanced systems raise questions about the role of the human operator and the number of humans required to run these systems. This chapter discusses a variety of approaches to evaluating staffing requirements and describes in detail two HAMMLAB studies performed to evaluate staffing requirements in advanced versus conventional nuclear power plant control rooms.

Using Discrete Event Simulation to Assess Human Lifting and Assembly of Vehicle Armor

The Future Combat Systems (FCS) program goal is to develop the next generation of vehicles and networks for the Army. Eight configurations of Manned Ground Vehicles (MGV) are being designed as part of this effort. Requirements state that each MGV must weight less than 20 Tons to be C-130 transportable. To achieve this weight limitation the armor will be removed before flight. The armor will be flown in on a separate aircraft and installed at the destination. A specific challenge for the manufacturer of the MGVs is determining how best to utilize human resources in the installation process. This poster will describe the use of discrete event simulation to develop a human performance model that helps determine an optimal combination of manpower, armor panels, and installation equipment. Four different “up-armor” scenarios were simulated each with different manpower, number of armor pieces, size of armor pieces, and material handling equipment requirements.

A Cognitive Systems Engineering Evaluation of a Tool to Aid Imagery Analysts

A cognitive systems engineering evaluation of an imagery analysis system was conducted to capture baseline performance and workload and compare it to performance with advanced filtering capabilities. Experienced Imagery Analysts searched for and annotated targets of interest in full-motion video in Army- relevant scenarios. Measures of performance included percent of primary targets found, time to find primary target, total targets found, and interactions with the system (via mouse clicks). Performance metrics were augmented with continuous physiological and behavioral measurements in order to capture more accurate cognitive state fluctuations during human-system interaction. The findings suggest that in time-pressured situations, analysts were able to identify more targets with the advanced filter capabilities than in the baseline condition. The findings were used to suggest specific design changes to address workflow deficiencies. The study also developed and implemented a multi-aspect approach to estimate operator functional state during system evaluation.

Using an Information-Driven Decision_Making Human Performance Tool to Assess U.S. Army Command, Control, and Communication Issues

The military command and control process is certain to change given the introduction of new information technology and new organizational structures. To predict how these changes will impact system performance, the U.S. Army Research Laboratory Human Research and Engineering Directorate (ARL-HRED) sponsored the development of a modeling environment in which one can develop multiple concept models for any sized organization, staffed by any number of people, performing any number of functions and tasks, and under various communication and information loads. This environment is called Command, Control, and Communication: Techniques for Reliable Assessment of Concept Execution (C3TRACE). Among the performance measures tracked are operator utilization, the number of tasks performed, and the quality of decisions made by the operators. Recently, C3TRACE was used to develop models of two Future Combat Systems (FCS) conceptual configurations. This paper discusses the theory and application of the tool.