Distributed Control of Networked Nonlinear Euler-Lagrange Systems

Motivated by recent developments in formation and cooperative control of networked multi-agent systems, the main goal of this thesis is development of efficient synchronization and formation control algorithms for distributed control of networked nonlinear systems whose dynamics can be described by Euler-Lagrange (EL) equations. One of the main challenges in the design of the formation control algorithm is its optimality and robustness to parametric uncertainties, external disturbances and ability to reconfigure in presence of component, actuator, or sensor faults. Furthermore, the controller should be capable of handling switchings in the communication network topology. In this work, nonlinear optimal control techniques are studied for developing distributed controllers for networked EL systems. An individual cost function is introduced to design a controller that relies on only local information exchanges among the agents. In the development of the controller, it is assumed that the communication graph is not fixed (in other words the topology is switching). Additionally, parametric uncertainties and faults in the EL systems are considered and two approaches, namely adaptive and robust techniques are introduced to compensate for the effects of uncertainties and actuator faults. Next, a distributed H_infinity performance measure is considered to develop distributed robust controllers for uncertain networked EL systems. The developed distributed controller is obtained through rigorous analysis and by considering an individual cost function to enhance the robustness of the controllers in presence of parametric uncertainties and external bounded disturbances. Moreover, a rigorous analysis is conducted on the performance of the developed controllers in presence of actuator faults as well as fault diagnostic and identification (FDI) imperfections. Next, synchronization and set-point tracking control of networked EL systems are investigated in presence of three constraints, namely, (i) input saturation constraints, (ii) unavailability of velocity feedback, and (iii) lack of knowledge on the system parameters. It is shown that the developed distributed controllers can accomplish the desired requirements and specification under the above constraints. Finally, a quaternion-based approach is considered for the attitude synchronization and set-point tracking control problem of formation flying spacecraft. Employing the quaternion in the control law design enables handling large rotations in the spacecraft attitude and, therefore, any singularities in the control laws are avoided. Furthermore, using the quaternion also enables one to guarantee boundedness of the control signals both with and without velocity feedback

Course Transformation From Synchronous To Asynchronous Using Technology

A robust project-based engineering course at the undergraduate senior level, traditionally taught face-to-face synchronously, has been transformed to a distance course taught asynchronously using distance modes. In this case, pedagogical transitions, alterations, and adjustments are required for meeting the course objectives effectively and without sacrificing the instructional quality. Project collaboration in groups or teams requires effective communication, which is made possible in this case with extensive utilization of new information technology (IT) and communication tools such as virtual meetings. Some technologies used in transition from live to distance learning modes are summarized and their effectiveness is addressed experientially in this paper. This discussion includes some benefits of implementing project-based courses in the domain of distance learning modes. © American Society for Engineering Education, 2009

A Simulation Package With Applications In Underdeveloped Nations For Systems Design

A menu-driven graphics-based simulation package called DESIGN has been developed. It enables the users to add/delete poles or zeros and vary design requirements such as the value of the gain, damping factor, overshoot, delay time, rise time, bandwidth, resonance frequency, etc., to investigate the effects of these parameters on system performance. The package is free and is designed around the root locus plot of a unity feedback control system in a MS-Window environment. It is a useful tool for both the instructors and the students in a basic control system theory course with a special emphasis on design. © American Society for Engineering Education, 2006

Crafting Online Exams In Engineering And Technology: Latest Challenges, Methodologies, And Trends

In recent years distance education and learning have emerged as a popular method of instructional delivery in engineering and technology-related fields. Many faculties of engineering and technology may found themselves teaching online classes or thinking about teaching one. In this process, crafting and preparation of online exams without sacrificing the educational quality and exam security is a crucial issue to the faculty. Psychological setbacks and barriers among engineering students also add another concern for the faculty teaching in a distance education environment, i.e., students may have fears of losing partial credit in an online multiple-choice exam. The asynchronous and economical advantages of distance education and learning that make offering and taking them very popular force the profession to re-examine and re-engineer some of these exam-related issues. In this paper we discuss issues as they relate to crafting online exams for the distance learning students in engineering and technology. More specifically, we discuss one major theme: how should faculty craft and design online exams for students studying in engineering and technology-related fields? We use some accurate but crude empirical data and evaluation methodologies to draw our conclusions. The data used are collected from more recent sample courses that have been taught by the authors over the last five years. This facilitates the evaluation of the latest challenges, development of new methodologies, and monitoring the current trends. © American Society for Engineering Education, 2008

Faculty Educational Experiences With Crafting Online Exams In Engineering And Technology

In recent years distance education and learning have emerged as a popular method of instructional delivery in engineering and technology-related fields. Many faculties of engineering and technology may found themselves teaching online classes or thinking about teaching one. In this process, crafting and preparation of online exams without sacrificing the educational quality and exam security is a crucial issue to the faculty. Psychological setbacks and barriers among engineering students also add another concern for the faculty teaching in a distance education environment, i.e., students may have fears of losing partial credit in an online multiple-choice exam. The asynchronous and economical advantages of distance education and learning that make offering and taking them very popular force the profession to re-examine and re-engineer some of these exam-related issues. In this paper we discuss some background and lessons learned from our experience with crafting online exams for the distance learning students in engineering and technology. We use some accurate but crude empirical data and evaluation methodologies to draw our conclusions. The article\u27s discussion encompasses six faculty concerns of security, interactivity, equity, hands-on demonstration of concept, team-workability assessment, and ethics, all related to crafting online examinations in engineering and technology. Some of the results presented here are also confirmed intuitively through our informal discussions with the colleagues having similar experiences. We conclude, from our experiences, that in open and honest learning environments such as those in most institutions of higher education in the United States, the most important focus should be on the ethics education of the students before they can take online examinations in a non-proctored examination environment. © American Society for Engineering Education, 2009

Atmospheric Pollutants in an Iranian Industrial Metropolis: Spatiotemporal Analyses Associated with Health Risks and Photochemical Pollutions

Background: The present research addressed the spatiotemporal variations in such pollutants as benzene, toluene, ethylbenzene, and xylene (BTEX) in the atmosphere of Arak, a city in central Iran. Also, the health risk evaluation and ozone formation potential (OFP) were assessed. Methods: The air samples were collected and evaluated through gas chromatography-mass spectrometry (GC-MS) over a one-year period. Results: The overall BTEX levels ranged between 2.7-256 µgr/m3. The seasonal levels showed considerable variations among benzene, toluene, ethylbenzene, and xylene, and the levels of total BTEX. Comparison of the air samples between morning and evening for the concentrations of BTEX components revealed that the values were higher in the evening; however, there were no significant differences observed among them. The spatial map indicated that the maximal concentration of BTEX components occurred in high-traffic zones of the city. The maximal and minimal OFP levels were recorded in the summer (254.8 µgr/m3) and autumn (64.9 µgr/m3), respectively. The average toluene/benzene (T/B) ratio found to be 4.3, indicating the fuel combustion was the major source of atmospheric BTEX from vehicles. Conclusion: The measured cancer risk value for benzene (6.68×10-5) was higher than those recommended by the WHO and U.S. Environmental Protection Agency. Therefore, exposure to atmospheric benzene had a carcinogenic risk for Arak inhabitants. This needs further investigation in future studies. The acceptable hazard quotients (<1) for all BTEX species posed minimal risks of non-cancer diseases for the population

Faculty Practices In Effective Online Student Assessment In Engineering And Technology

Distance learning is recognized in the engineering and technology-related education profession as an attractive method of instructional delivery. The asynchronous and economical advantages of distance education and learning make offering and taking them very popular. The fast pace availability of the technology and its rapidly changing environment compel the profession to constantly evaluate, address, re-evaluate and re-engineer some of the assessment-related issues. In this article, we discuss some aspects of online performance assessment in distance learning environments in engineering and technology. The article is built on the foundation laid by many previous studies and articles by the authors and others. It encompasses discussions on effective techniques on the use of technology for online student performance assessment. We rely on our own many years of online teaching as an experiential instrument in the former parts of this study while we use statistical analysis in the later part of the paper. The data used are collected from recent sample courses in engineering and technology taught by the authors and their colleagues. We conclude that the currently available automated robust and effective online assessment tools are significant in pedagogical assessment in engineering and technology. The results are confirmed through our discussions with the colleagues having similar experience at some other institutions of higher education. We plan to expand our database and revalidate our study through collaborative data-sharing efforts with our colleagues across the States in the near future. © American Society for Engineering Education, 2010

The Relationship between Lung and Heart Two-Dimensional Parameters and Three-Dimensional Dose-Volume Data in Adjuvant Radiotherapy for Breast Cancer

Background: Two-dimensional (2D) radiographic parameters have been used to estimate the amount of heart and lung irradiated for minimizing heart and lung complications in breast cancer patients. The aim of this study was to investigate the correlation between traditionally used 2D radiographic and dose-volume parameters during adjuvant radiotherapy of breast cancer. Methods: In this cross-sectional study, we analyzed 121 female patients treated with breast-conserving surgery (BCS) or modified radical mastectomy (MRM) and 3D conformal radiotherapy (3DCRT) using two-field radiotherapy (2FRT) or three-field radiotherapy (3FRT) technique. All patients underwent computed tomography (CT)-planning. Two-D parameters, including central lung distance (CLD), maximum lung depth (MLD), maximum heart length (MHL), maximum heart distance (MHD), and chest wall separation (CWS), were measured using digitally reconstructed radiographs (DRR) and CT images. DVHs for lung, heart, and target were created. The Pearson correlation test was used to evaluate the correlation between 2D radiographic and dose-volume parameters. Results: There was a correlation between CLD and ipsilateral lung V5-20Gy and Dmean and between MLD and ipsilateral lung V5-20Gy. In 2FRT, only moderate correlation between CLD and ipsilateral lung V20Gy (r = 0.453, P = 0.003) and between MLD and ipsilateral lung V20Gy (r = 0.593, P <0.001) were observed. Poor correlation of MHL and heart V25Gy (r = 0.409, P = 0.007) was seen only in 3FRT. There was a correlation between MHD and heart dose-volume data, with a strong correlation between MHD and heart V5-25Gy and Dmean (r = 0.875-0.934, P<0.001) in the 2FRT group. No correlation between CWS and breast Dmax was found. Conclusion: There was a correlation between 2D parameters (i.e., CLD, MLD, and MHD) and the heart and lung dose-volume parameters during adjuvant breast radiotherapy. Although CLD was correlated to ipsilateral lung V5-20Gy and Dmean, the correlation between CLD and ipsilateral lung V20Gy was greater than other dose-volume parameters. MHD provided a close estimation of heart dose-volume parameters