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1. Sorting It Out: Identifying and Addressing Conflicts and Business Ethics in Global Value Networks

Author

Davis, Matthew C., Voss, Hinrich, Sumner, Mark P., and Singhal, Divya

Abstract

Global value networks are often large, complex, and opaque. Understanding the relationships among stakeholders involved in these networks or organizations can be challenging. This card sort task provides an interactive way to engage participants in questioning the roles of stakeholders who are involved in a business ethics dilemma or an organizational product failure. This card sort task and discussion activity encourages participants to recognize that stakeholders may hold different knowledge, responsibility, or power; identify competing, conflicting, or complementary interests across stakeholders; articulate logical arguments; and engage in debate, compromise, and critical evaluation. This technique has been used successfully with undergraduate and postgraduate business, management, and social science students and is suitable for in-person and remote classes.

Published
2023
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24. Continuous yarn processing systems

Author

Sumner, Mark

Subjects
677
Abstract

The objective of the Engineering Doctorate project was the development of a continuous yam dyeing system which could meet the needs of a changing textile industry. Through an examination of the changes in the industry, it was found that the system must incorporate waste minimisation principles, be flexible and responsive to the demands of the fashion industry and provide the yam dyer with short lead times. Two yam processing systems were identified and investigated to determine whether they could be used to fulfil the aims of the project. The first system was based on the Fibre 'M' Yam Texturing and Dyeing process previously developed at UMIST. The second was a new development referred to as the Sealed Applicator Device (SAD). It had been shown in the past that the Fibre 'M' based system could simultaneously texture and dye polyester yam to a relatively high standard of fixation and bulk. However, through the process investigation presented here it was found that the system lacked flexibility, ease of use and, in addition, its environmental impact could be considerable. The investigation of the SAD process proved to be more fruitful. It was found that the SAD process could be used to impregnate single ends of yam with liquor to a high degree of accuracy and control. Laboratory trials sho~ed that the SAD system could be used to impregnate worsted yam with dye liquor levelly at yam speeds up to 500 m1min at liquor to goods ratios as low as 0.3 : 1. Also it was shown that the SAD system could be used as a high speed yam washing device as well as a yam drying device. Through a combination of the impregnation, washing and drying capabilities of the SAD process, in conjunction with an autoclave stage, it was demonstrated that the SAD process could be used to continuously dye, wash and dry yams at high speed to commercial standards of penetration, levelness and fastness. The potential savings for a yam dyer through the use of the SAD system were explored. It was also shown, through commercial trials, that the SAD system could be used as an integral part of a simultaneous yam folding, setting, conditioning and lubricating process for worsted yams. Comparable levels of setting, conditioning and lubricating to the industry standard were achieved using the SAD process, with the potential for considerable saving for the spinner.

Published
1997

27. Dynamic Analysis, Stability and Design of Grid Forming Converters With PI-Based Voltage Control in DC and 3-Phase AC Microgrids

Author

Navarro-Rodriguez, Angel, Garcia, Pablo, Cano, Jose M., and Sumner, Mark

Abstract

This article analyzes the dynamic behavior of the voltage control loop based on proportional-integral regulators, commonly used for grid-forming converters in 3-phase AC and DC Microgrids and applications that involve a DC-link voltage control. The article proposes a simple and accurate generalized analysis useful both for the system characterization and design. Two different control schemes, based on linear (Direct Voltage Control, DVC) and quadratic voltage feedback (Quadratic Voltage Control, QVC), are analytically studied, simulated and experimentally tested, demonstrating a superior performance of the QVC under the presence of constant power loads. The operation limits, the system stability and the disturbance rejection capability are analyzed considering the effect of control and plant parameters and the effect of the different types of disturbances and the operating point, taking into account the non-linearities of the system. The analysis is mainly focused on the effect of constant power loads given their negative impact on the system performance. The study provides a generic procedure for the analysis and design of proportional-integral voltage controllers, including the selection of the system capacitance for meeting specific dynamic specifications while considering system characteristics as the load level, the stability margins and the maximum voltage deviation under disturbances.

Published
2023
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28. Distributed Predictive Secondary Control With Soft Constraints for Optimal Dispatch in Hybrid AC/DC Microgrids

Author

Navas-Fonseca, Alex, Burgos-Mellado, Claudio, Gomez, Juan S., Espina, Enrique, Llanos, Jacqueline, Saez, Doris, Sumner, Mark, and Olivares, Daniel E.

Abstract

Hybrid AC/DC microgrids (H-MGs) are a prominent solution for integrating distributed generation and modern AC and DC loads. However, controlling these systems is challenging as multiple electrical variables need to be controlled and coordinated. To provide flexibility to the control system, these variables can be regulated to specific values or within secure bands. This paper proposes a set of distributed model predictive control schemes for the secondary control level to control certain variables to specific values and other variables within secure pre-defined bands into H-MGs. Specifically, optimal dispatch of active and reactive power is achieved while frequency and voltages are regulated within secure bands in H-MGs. Dynamic models of AC generators, DC generators and interlinking converters along with their novel multi-objective cost functions are developed in constrained distributed predictive optimisation problems to simultaneously achieve the aforementioned objectives via information sharing. Extensive simulation work validates the performance of this proposal.

Published
2023
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40. Sensorless Control of a PMSM Drive Post an Open Circuit Failure Based on 3D?SVPWM Technique

Author

Saleh, Kamel and Sumner, Mark

Subjects
Electrical and Electronic Engineering
Abstract

This paper presents a novel technique to maintain the PMSM Drive operation post the failure in one phase and the failure of the speed sensor occur simultaneously. The PMSM motor is driven by a fault-tolerant inverter. The use of the fault-tolerant inverter associated with the using of the 3-Dimension space vector pulse width modulation (3-D SVPWM) allow the PMSM drive to maintain its performance post the failure in one phase. Moreover, the stability of the PMSM drive system is furtherly enhanced through utilizing a novel algorithm to obtain the rotor position and speed post the failure in the speed sensor. The algorithm is based on measuring the transient response of the remaining healthy currents post the failure due to the inverter switching actions. The results that are obtained through simulation prove the reliability of the system to maintain its operation post the failure in one phase of the motor and the failure in the speed sensor occurred simultaneously. Also, the results demonstrate the effectiveness of the proposed technique to maintain the performance of the PMSM drive system under different speeds steps and load conditions post the failure. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Published
2022

41. Characterizing Interaction with Visual Mathematical Representations

Author

Sedig, Kamran and Sumner, Mark

Abstract

This paper presents a characterization of computer-based interactions by which learners can explore and investigate visual mathematical representations (VMRs). VMRs (e.g., geometric structures, graphs, and diagrams) refer to graphical representations that visually encode properties and relationships of mathematical structures and concepts. Currently, most mathematical tools provide methods by which a learner can interact with these representations. Interaction, in such cases, mediates between the VMR and the thinking, reasoning, and intentions of the learner, and is often intended to support the cognitive tasks that the learner may want to perform on or with the representation. This paper brings together a diverse set of interaction techniques and categorizes and describes them according to their common characteristics, goals, intended benefits, and features. In this way, this paper aims to provide a preliminary framework to help designers of mathematical cognitive tools in their selection and analysis of different interaction techniques as well as to foster the design of more innovative interactive mathematical tools. An effort is made to demonstrate how the different interaction techniques developed in the context of other disciplines (e.g., information visualization) can support a diverse set of mathematical tasks and activities involving VMRs.

Published
2006
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