Test-Based Stabilizing Control of COVID-19 Transmission

(Georgia Institute of Technology, 2020-03) Sadegh, Nader ; Sadegh, Payman

The COVID-19 pandemic has confronted the world with a health and an economic crisis not seen since 1918. Appearing first in Wuhan, China, in late 2019, the virus has now spread to over 150 countries. At the time of this writing, hundreds of thousands have already been infected and tens of thousands have died as a result. Given the virus' high degree of contagion, a question that occupies everyone's mind is whether a strategy could be conceived to suppress or at least substantially slow the spread of the virus until a vaccine becomes widely available. Using an extended SEIR model with COVID-19's available epidemiological parameters, this paper studies a feedback control solution to stabilize the virus' transmission dynamic based on a test-and-isolate strategy. The derived theoretical results combined with simulation analyses are used to answer key questions around testing strategies that will be required for suppression of the virus.
Biodynamic Feedthrough Compensation and Experimental Results Using a Backhoe

(Georgia Institute of Technology, 2011-03) Heather C. Humphreys ; Book, Wayne J. ; Huggins, James D.

In some operator-controlled machines, motion of the controlled machine excites motion of the human operator, which is fed back into the control device, causing unwanted input and sometimes instability; this phenomenon is termed biodynamic feedthrough. In operation of backhoes and excavators, biodynamic feedthrough causes control performance degradation. This work utilizes a previously developed advanced backhoe user interface which uses coordinated position control with haptic feedback, using a SensAble Omni six degree-of-freedom haptic display device. Backhoe user interface designers and our own experiments indicate that biodynamic feedthrough produces undesirable oscillations in output with conventionally controlled backhoes and excavators, and it is even more of a problem with this advanced user interface. Results indicate that the coordinated control provides more intuitive operation, and the haptic feedback relays meaningful information back to the user. But the biodynamic feedthrough problem must be overcome in order for this improved interface to be applicable. For the purposes of reducing model complexity, the system is limited to a single degree of freedom, using fore-aft motion only. This paper investigates what types of controller-based methods of compensation for biodynamic feedthrough are most effective in backhoe operation, and how they can be implemented and tested with human operators.
Designing Platforms for Customizable Produces and Processes in Markets of Non-Uniform Demand

(Georgia Institute of Technology, 2007) Williams, Christopher Bryant ; Rosen, David W. ; Mistree, Farrokh ; Allen, Janet K.

The foremost difficulty in making the transition to mass customization is how to offer product variety affordably. The answer to this quandary lies in the successful management of modularity and commonality in the development of products and their production processes. While several platform design techniques have emerged as a means to offer modularity and commonality, they are limited by an inability to handle multiple modes of offering variety for multiple design specifications. The Product Platform Constructal Theory Method (PPCTM) is a technique that enables a designer to develop platforms for customizable products while handling issues of multiple levels of commonality, multiple product specifications, and the inherent trade-offs between platform extent and performance. The method is limited, however, by its inability to handle multiple design objectives and its reliance on the assumption that demand in the market is uniform for each product variant. The authors address these limitations in this paper by infusing the utility-based compromise Decision Support Problem and demand modeling techniques. The authors further augment the PPCTM by extending it use to a new domain: the design of process parameter platforms. The augmented approach is illustrated through a tutorial example: the design of a product and a process parameter platform for the realization of a line of customizable cantilever beams.
Validating Behavioral Models For Reuse

(Georgia Institute of Technology, 2007) Paredis, Christiaan J. J. ; Malak, Richard J., Jr.

When using a model to predict the behavior of a physical system of interest, engineers must be confident that, under the conditions of interest, the model is an adequate representation of the system. The process of building this confidence is called model validation. It requires that engineers have knowledge about the system and conditions of interest, properties of the model and their own tolerance for uncertainty in the predictions. To reduce time and costs, engineers often reuse preexisting models that other engineers have developed. However, if the user lacks critical parts of this knowledge, model validation can be as time consuming and costly as developing a similar model from scratch. In this article, we describe a general process for performing model validation for reused behavioral models that overcomes this problem by relying on the formalization and exchange of knowledge. We identify the critical elements of this knowledge, discuss how to represent it and demonstrate the overall process on a simple engineering example.
Multi-Attribute Utility Analysis in Set-Based Conceptual Design

(Georgia Institute of Technology, 2007) Paredis, Christiaan J. J. ; Malak, Richard J., Jr. ; Aughenbaugh, Jason Matthew

During conceptual design, engineers deal with incomplete product descriptions called design concepts. Engineers must compare these concepts in order to move towards the more desirable designs. However, comparisons are difficult because a single concept associates with numerous possible final design specifications, and any meaningful comparison of concepts must consider this range of possibilities. Consequently, the performance of a concept can only be characterized imprecisely. While standard multi-attribute utility theory is an accepted framework for making preference-based decisions between precisely characterized alternatives, it does not directly accommodate the analysis of imprecisely characterized alternatives. By extending uncertainty representations to model imprecision explicitly, it is possible to apply the principles of utility theory to such problems. However, this can lead to situations of indeterminacy, meaning that the decision maker is unable to identify a single concept as the most preferred. Under a set-based perspective and approach to design, a designer can work towards a single solution systematically despite indecision arising from imprecise characterizations of design concepts. Existing work in set-based design primarily focuses on feasibility conditions and single-attribute objectives, which are insufficient for most design problems. In this article, we combine the framework of multi-attribute utility theory, the perspective of set-based design, and the explicit mathematical representation of imprecision into a single approach to conceptual design. Each of the component theories are discussed, and their combined application developed. The approach is illustrated using the conceptual design of a fixed-ratio power transmission as an example. Additionally, important directions for future research are identified, with a particular focus on the process of modeling abstract design concepts.
Manufacturing Cellular Materials Via Three-Dimensional Printing of Spray-dried Metal Oxide Ceramic Powder

(Georgia Institute of Technology, 2007) Rosen, David W. ; Williams, Christopher Bryant

Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer high strength accompanied by a relatively low mass. Unfortunately, existing manufacturing techniques constrain a designer to a predetermined part mesostructure, material type, and macrostructure. In this paper, the authors document their design rationale for the selection of the Three-Dimensional Printing (3DP) additive manufacturing process as a means to fabricate metallic cellular materials. This is achieved by selectively printing a solvent into a bed of spray-dried metal oxide ceramic powder. The resulting green part undergoes reduction and sintering post-production processes in order to chemically convert it to metal.
Empowering Students to Learn How to Learn: Mass Customization of Graduate Engineering Design Course

(Georgia Institute of Technology, 2006) Mistree, Farrokh ; Williams, Christopher Bryant

ME 6101: Engineering Design is a graduate level course offered through the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. To empower students to learn how to learn, the orchestrators of ME 6101 strive to offer an individual course in a group setting. In this paper, the techniques utilized to create this type of learning environment are described in terms parallel to those of the mass customization paradigm. Excerpts from students' essays are presented as anecdotal evidence that the concerted use of these methods aids and empowers students both in the internalization of course content and the development of critical analysis, abstraction, and synthesizing skills that will help them become lifelong learners.
Interactive Multi-Modal Robot Programming

(Georgia Institute of Technology, 2005) Paredis, Christiaan J. J. ; Khosla, Pradeep K. ; Iba, Soshi

As robots enter the human environment and come in contact with inexperienced users, they need to be able to interact with users in a multi-modal fashion—keyboard and mouse are no longer acceptable as the only input modalities. This paper introduces a novel approach for programming robots interactively through a multi-modal interface. The key characteristic of this approach is that the user can provide feedback interactively at any time—during both the programming and the execution phase. The framework takes a three-step approach to the problem: multi-modal recognition, intention interpretation, and prioritized task execution. The multi-modal recognition module translates hand gestures and spontaneous speech into a structured symbolic data stream without abstracting away the user's intent. The intention interpretation module selects the appropriate primitives to generate a task based on the user's input, the system's current state, and robot sensor data. Finally, the prioritized task execution module selects and executes skill primitives based on the system's current state, sensor inputs, and prior tasks. The framework is demonstrated by interactively controlling and programming a vacuum-cleaning robot. The demonstrations are used to exemplify the interactive programming and the plan recognition aspect of the research.
Towards the Design of a Layer-Based Additive Manufacturing Process for the Realization of Metal Parts of Designed Mesostructure

(Georgia Institute of Technology, 2005) Mistree, Farrokh ; Rosen, David W. ; Williams, Christopher Bryant

Low-density cellular materials, metallic bodies with gaseous voids, are a unique class of materials that have high strength, good energy absorption characteristics, good thermal and acoustic insulation properties, accompanied by an extremely low mass. Unfortunately, current cellular material manufacturing processes severely limit a designer's ability to control the part mesostructure, the material composition, and the part macrostructure. As such, the authors look towards the use of layer-based additive manufacturing (AM) as a means of providing the design freedom that is currently absent from cellular material manufacturing processes. Since current metal-based AM techniques do not offer an adequate means of satisfying the unique requirements of cellular materials, the authors carry out the conceptual design of a new AM process that is dedicated to the manufacture of cellular materials. Specifically, the authors look to the layer-based additive fabrication of metal oxide powders followed by post-processing in a reducing atmosphere as a means of fabricating three-dimensional, low-density cellular metal parts with designed mesostructure. In this paper, the authors detail this conceptual design process and select working principles that are worthy of further investigation. Insights gained as a result of designing an AM process for a specific class of geometry (e.g. considerations for small wall thickness, high quality surface finish, internal voids, and support material) and investigating the use of AM for production-scale manufacturing are also detailed.
Integrating Social Aspects and Group Work Aspects in Engineering Design Education

(Georgia Institute of Technology, 2003) Subrahmanian, Eswaran ; Westerberg, Arthur ; Talukdar, Sarosh ; Garrett, James ; Jacobson, Annette ; Paredis, Christiaan J. J. ; Amon, Cristina ; Herder, Paulien ; Turk, Adam

Over the last several years, the Institute for Complex Engineered Systems (ICES), from its origins as the Engineering Design Research Center (EDRC), has evolved two elective courses addressing the social and group aspects of engineering design. These courses are offered to students in the engineering undergraduate curricula as part of a design minor.