Reference governors: Theoretical Extensions and Practical Applications.

As systems become downsized and operate at the limits of performance, control systems must be designed to ensure that system state and control constraints are satisfied; however, conventional control schemes are often designed without taking constraints into account. Reference governors and the related, more flexible, extended command governors are add-on, constraint enforcement schemes that modify reference signals to conventionally designed, closed-loop systems for the purpose of enforcing output constraints. The focus of this dissertation is on theoretical and methodological extensions of reference and extended command governors, and on their practical applications. Various theoretical results are presented. The first is the development of reduced-order reference and extended command governors, which enables constraint enforcement schemes using simplified models. The second, related development is that of reference governors for decentralized systems that may or may not communicate over a network. The third considers command governors with penalty functions that are used to enforce prioritized sets of constraints, as well as reference governors that are applied to a sequence of prioritized references. The fourth considers the often overlooked case of applying reference governors to linear systems subject to nonlinear constraints; various formulations of constraints are considered, including quadratic constraints and mixed logical-dynamic constraints. The final theoretical development considers using contractive sets to design reference governors for systems with time-varying reference inputs or subject to time-dependent constraints. Numerical simulations are used throughout to illustrate the theoretical advances. The design of reference governor schemes for three systems arising in practical applications is also presented. The first scheme enforces compressor surge constraints for turbocharged gasoline engines, ensuring that the compressor does not surge. The second scheme is designed for an airborne wind energy system that is subject to various flight constraints including constraints on altitude and angle of attack. The third and final scheme is designed for the constrained control of spacecraft attitude, whose discrete-time dynamics evolve on the configuration space SO(3). In the case of the first application, experimental vehicle results are reported that show successful avoidance of surge. For the other two applications, nonlinear model simulation results are reported that show enforcement of system constraints.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113518/1/kalabic_1.pd

Reduced Order and Prioritized Reference Governors for Limit Protection in Aircraft Gas Turbine Engines

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140424/1/6.2014-1149.pd

Identifying, Tracking, and Prioritizing Parts Unavailability

The Air Force is pursuing several efficiency initiatives designed to reduce support function costs. One such initiative is an effort to reduce the flow days of items being repaired in the Air Force\u27s organic depots. Many end items are affected by awaiting parts (AWP) delays, which increase total flow days. The first step in reducing AWP delays is to identify which piece parts are causing the delays. A gap analysis was conducted to identify a process for creating a list of piece parts that are causing AWP delays. In addition, a clinimetric method was used to develop an aggregate measure of AWP impact by which the list of piece parts could be prioritized. The gap analysis showed that such a list can be created with Cognos, a reporting tool currently used by the depots, which can pull data from multiple information systems. In addition, only minor changes to information recorded throughout the repair process are needed. An aggregate measure of AWP impact was also created and tested. It produced significantly different prioritizations from the individual constituent variables, and provides a possible method for helping depot managers to understand decision tradeoffs between different parts shortage priorities

Trafficking in Persons: International Dimensions and Foreign Policy Issues for Congress

[Excerpt] Trafficking in persons, or human trafficking, refers to the subjection of men, women, and children to exploitative conditions that can be tantamount to slavery. Reports suggest that human trafficking is a global phenomenon, victimizing millions of people each year and contributing to a multi-billion dollar criminal industry. It is a centuries-old problem that, despite international and U.S. efforts to eliminate it, continues to occur in virtually every country in the world. Human trafficking is also an international and cross-cutting policy problem that bears on a range of major national security, human rights, criminal justice, social, economic, migration, gender, public health, and labor issues. Although there is widespread support among policy makers for the continuation of U.S. anti-trafficking goals, ongoing reports of such trafficking worldwide raise questions regarding whether sufficient progress has been made to deter and ultimately eliminate the problem, the end goal of current U.S. anti-trafficking policies. This report explores current foreign policy issues confronting U.S. efforts to combat human trafficking, the interrelationship among existing polices, and the historical and current role of Congress in such efforts

Innovation in the Public Sector

Innovation is something that is new, capable of being implemented, and has a beneficial impact. It is not an event or activity; it is a concept, process, practice, and capability that defines successful organizations. Innovation in the public sector can help create value for society

An Epistemological Inquiry into the Incorporation of Emergency Management Concept in the Homeland Security with a Post-Disaster Security Centric Focus

The historical roots of the Emergency Management concept in the U.S. date back to 19th century. As disasters occurred, policies relating to disaster response have been developed, and many statuary provisions, including several Federal Disaster Relief Acts, conceptually established the framework of Emergency Management. In 1979, with the foundation of the Federal Emergency Management Agency (FEMA), disaster relief efforts were finally institutionalized, and the federal government acknowledged that Emergency Management included mitigation, preparedness, response and recovery activities as abbreviated \u27MPRR.\u27 However, after 2000, the U.S. experienced two milestone events - the September 11 terrorist attacks in 2001 and Hurricane Katrina in 2005. Following the foundation of the Department of Homeland Security (DHS) in 2002, the definitional context of Emergency Management and its phases/components, simply its essence, evolved and was incorporated into many official documents differently, creating contextual inconsistencies. Recent key official documents embody epistemological problems that have the potential to traumatize the coherence of the Homeland Security contextual framework as well as to impose challenges theoretically to the education and training of Homeland Security/Emergency Management stakeholders. Furthermore, the conceptual design of the Emergency Support Functions (ESF) which have been defined within the context of the National Response Framework (NRF) displays similar problematic symptoms, and existing urban area Public Safety and Security planning processes have also not been supported by methodologies that are aligned with the post-disaster security requirements. To that end, the conceptual framework of Emergency Management and its incorporation in the Homeland Security global architecture should be revised and redefined to enhance coherence and reliability. Coherence in the contextual structure directly links to the system\u27s organizational structure and its viability functions. Also, holistic multi-dimensional system representations/abstractions, which would support appreciation of the system\u27s complex context, should be incorporated in policy documents to be utilized to educate the relevant stakeholders (individuals, teams, etc.) during the training/orientation programs. In addition, the NRF and its ESFs should be reviewed through a post-disaster security centric focus, since the post-disaster environment has unique characteristics that should be addressed by different approaches. In that sense, this dissertation develops a Post-Disaster Security Index (PDSI) Model that provides valuable insights for security agents and other Emergency Management and Homeland Security stakeholders

Reference Governors for MIMO Systems and Preview Control: Theory, Algorithms, and Practical Applications

The Reference Governor (RG) is a methodology based on predictive control for constraint management of pre-stablized closed-loop systems. This problem is motivated by the fact that control systems are usually subject to physical restrictions, hardware protection, and safety and efficiency considerations. The goal of RG is to optimize the tracking performance while ensuring that the constraints are satisfied. Due to structural limitations of RG, however, these requirements are difficult to meet for Multi-Input Multi-Output (MIMO) systems or systems with preview information. Hence, in this dissertation, three extensions of RG for constraint management of these classes of systems are developed. The first approach aims to solve constraint management problem for linear MIMO systems based on decoupling the input-output dynamics, followed by the deployment of a bank of RGs for each decoupled channel, namely Decoupled Reference Governor (DRG). This idea was originally developed in my previous work based on transfer function decoupling, namely DRG-tf. This dissertation improves the design of DRG-tf, analyzes the transient performance of DRG-tf, and extends the DRG formula to state space representations. The second scheme, which is called Preview Reference Governor, extends the applicability of RG to systems incorporated with the preview information of the reference and disturbance signals. The third subject focuses on enforcing constraints on nonlinear MIMO systems. To achieve this goal, three different methods are established. In the first approach, which is referred to as the Nonlinear Decoupled Reference Governor (NL-DRG), instead of employing the Maximal Admissible set and using the decoupling methods as the DRG does, numerical simulations are used to compute the constraint-admissible setpoints. Given the extensive numerical simulations required to implement NL-DRG, the second approach, namely Modified RG (M-RG), is proposed to reduce the computational burden of NL-DRG. This solution consists of the sequential application of different RGs based on linear prediction models, each robustified to account for the worst-case linearization error as well as coupling behavior. Due to this robustification, however, M-RG may lead to a conservative response. To lower the computation time of NL-DRG while improving the performance of M-RG, the third approach, which is referred to as Neural Network DRG (NN-DRG), is proposed. The main idea behinds NN-DRG is to approximate the input-output mapping of NL-DRG with a well-trained NN model. Afterwards, a Quadratic Program is solved to augment the results of NN such that the constraints are satisfied at the next timestep. Additionally, motivated by the broad utilization of quadcopter drones and the necessity to impose constraints on the angles and angle rates of drones, the simulation and experimental results of the proposed nonlinear RG-based methods on a real quadcopter are demonstrated