A new momentum management controller for the space station

A new approach to CMG (control moment gyro) momentum management and attitude control of the Space Station is developed. The control algorithm utilizes both the gravity-gradient and gyroscopic torques to seek torque equilibrium attitude in the presence of secular and cyclic disturbances. Depending upon mission requirements, either pitch attitude or pitch-axis CMG momentum can be held constant: yaw attitude and roll-axis CMG momentum can be held constant, while roll attitude and yaw-axis CMG momentum cannot be held constant. As a result, the overall attitude and CMG momentum oscillations caused by cyclic aero-dynamic disturbances are minimized. A state feedback controller with minimal computer storage requirement for gain scheduling is also developed. The overall closed-loop system is stable for + or - 30 percent inertia matrix variations and has more than + or - 10 dB and 45 deg stability margins in each loop

Interim security insights and implications from the first two months of the Russia-Ukraine war

Russia's ongoing struggles during its invasion of Ukraine have led some to suggest that the Russian military lacks the capability to credibly threaten the North Atlantic Treaty Organization (NATO) and its member states. However, narrowly focusing on Russia's tactical and operational struggles, while omitting the flawed Russian strategic decisionmaking which underpinned the invasion, is a dangerous approach. While Russia's significant losses in this war will clearly degrade its ability to conduct large scale offensive operations against NATO in the short term, it is too soon to write off the medium to long-term threat posed by Russia. Therefore, as the Russian invasion enters a new phase, it is useful to determine what lessons should and should not be derived from this conflict. In our subsequent analysis, we analyze these initial insights and provide policy recommendations for NATO to enhance its conventional capability and strengthen its ability to credibly deter future Russian aggression

Feasible US steps to strengthen NATO deterrence in the Baltics and Poland

With Russia's invasion of Ukraine, a renewed assessment of efforts by the United States and the North Atlantic Treaty Organization (NATO) to deter Russia from taking military action on NATO's eastern flank has become particularly salient. In the coming weeks, NATO leadership will meet to discuss what longer term force posture adjustments are required to create such a deterrent. This paper proposes several modest policy recommendations which will help inform the discussion and ultimately strengthen NATO's conventional deterrence postur

Cavitation phenomena in a stagnation point flow

Cavitation phenomena inherently occur in regions with low pressure. Consequently, it seems unlikely that cavitation would develop near the stagnation point of a blunt body flow. However, in recent experiments involving a high-speed bubbly jet impinging on a blunt body, we have observed substantial rapid growth and stretching of bubbles near the stagnation point over a wide range of flow parameters. Using a highspeed camera we observe that bubbles with initial diameters of tens of microns located very close to the blunt body are being stretched into long strings that are generally aligned parallel to the body surface. In-line Digital Holographic Microscopy (DHM) measurements show that the bubble strings are located far from the walls. High resolution 3-D holographic Particle Image Velocimetry (DHM-PIV) is performed to quantify the 3-D flow field near the leading edge of the blunt body. Instantaneous data show vortices being stretched by the local strain field close to the blunt body in an orientation consistent with the appearance of cavitation. These vortices are originated from the turbulent jet upstream. An estimate based on the measured vortex strength and strain field shows that stretching rapidly decreases the pressure in the vortex core below the vapor pressure, explaining the occurrence of cavitation.http://deepblue.lib.umich.edu/bitstream/2027.42/84222/1/CAV2009-final179.pd

Benchmark problems for robust control design

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76996/1/AIAA-20949-475.pd

A Model of Function-Based Representations

The need to model and to reason about design alternatives throughout the design process demands robust representation schemes of function, behavior, and structure. Function describes the physical effect imposed on an energy or material flow by a design entity without regard for the working principles or physical solutions used to accomplish this effect. Behaviors are the physical events associated with a physical artifact (or hypothesized concept) over time (or simulated time) as perceived by an observer. Structure, the most tangible concept, partitions an artifact into meaningful constituents such as features, Wirk elements, and interfaces in addition to the widely used assemblies and components. The focus of this work is on defining a model for function-based representations that can be used across various design methodologies and for a variety of design tasks throughout all stages of the design process. In particular, the mapping between function and structure is explored and, to a lesser extent, its impact on behavior is noted. Clearly, the issues of a function-based representation\u27s composition and mappings directly impact certain computational synthesis methods that rely on (digitally) archived product design knowledge. Moreover, functions have already been related to not only form, but also information of user actions, performance parameters in the form of equations, and failure mode data. It is essential to understand the composition and mappings of functions and their relation to design activities because this information is part of the foundation for function-based methods, and consequently dictates the performance of those methods. Toward this end, the important findings of this work include a formalism for two aspects of function-based representations (composition and mappings), the supported design activities of the model for function-based representations, and examples of how computational design methods benefit from this formalism

Building a Practical Natural Laminar Flow Design Capability

A preliminary natural laminar flow (NLF) design method that has been developed and applied to supersonic and transonic wings with moderate-to-high leading-edge sweeps at flight Reynolds numbers is further extended and evaluated in this paper. The modular design approach uses a knowledge-based design module linked with different flow solvers and boundary layer stability analysis methods to provide a multifidelity capability for NLF analysis and design. An assessment of the effects of different options for stability analysis is included using pressures and geometry from an NLF wing designed for the Common Research Model (CRM). Several extensions to the design module are described, including multiple new approaches to design for controlling attachment line contamination and transition. Finally, a modification to the NLF design algorithm that allows independent control of Tollmien-Schlichting (TS) and cross flow (CF) modes is proposed. A preliminary evaluation of the TS-only option applied to the design of an NLF nacelle for the CRM is performed that includes the use of a low-fidelity stability analysis directly in the design module

Multi-Disciplinary Project-Based Paradigm That Uses Hands-On Desktop Learning Modules and modern Learning Pedagogies

It has been established that traditional lectures ARE NOT best for student learning – yet that is what the community almost universally does! Furthermore, engineers work in broad multidisciplinary teams while classroom learning is individual and narrow. Yet, educators rarely invest the time and resources necessary to employ such innovations. In this CCLI type II award we are further refining Desktop Learning Modules (DLMs) within a Cooperative, Hands-on, Active, Problem based, Learning (CHAPL) setting for Chemical, Civil, Mechanical, Bio- and Electrical Engineering courses at a diverse set of institutions, including a community college engaged through a distance learning mode. A workbook is being developed and tested for easier adoption of the hands-on units and accompanying pedagogy. Existing concept inventories are not always showing significant gains in apparent student learning either for control or experimental groups and we are concluding these assessments are not well aligned with the macroscale design calculations being emphasized in the course. Therefore, new concept question assessments are being developed consisting of some macroscale questions from past inventories along with conceptual essay and calculation based questions aligned more specifically with the DLM processes at hand. Past implementations like this show students learn key concepts at least as well from each other in a guided inquiry as they do from lecture. Also, a mixed qualitative / quantitative assessment using a critical reasoning rubric reveals student abilities become better aligned with what is expected of graduating engineers ready for industry and that the CHAPL/DLM environment serves to reinforce understanding of physical phenomena, and to develop analytical and evaluative problem-solving skills. Interviews, surveys and team reports reveal students are better able to visualize concepts and that classroom exercises are promoting team skills and academic rigor. Faculty interviews reveal enhanced awareness of student misconceptions and improved monitoring of student growth in conceptual understanding and interpersonal skills. The poster and paper will highlight our findings and illustrate the CHAPL environment. Hands-on DLMs with cartridges used in teaching principles in the various disciplines will be demonstrated. A survey will be offered to those viewing the poster to assess potential interest in adoption of the DLMs and in participating in a follow-on NSF Type III proposal for Transforming Undergraduate Engineering Education through use of the DLMs and associated CHAPL pedagogies

A Qualitative Modeling Method for Platform Design

The development of a collection of related products sharing a common platform represents an important approach in modern product design. an ongoing problem is the application of design methods toward a limited set of evolving product data and archived design knowledge to search and explore alternative platform options. with the goal of maximizing the reuse of end item artifacts and supply chain elements, we propose a design modeling method using basic qualitative relationships among relevant performance, design, and noise parameters in the system of interest. by using qualitative models related to multiple levels of design data, the method provides a single high level graphical representation among design data including archived knowledge in a design repository. © 2005 IEEE

Multi-Disciplinary Hands-On Desktop Learning Modules and Modern Pedagogies

Our team’s research focuses on fundamental problems in undergraduate education in terms of how to expand use of well researched, yet still “new”, teaching pedagogies of ‘sensing’ or ‘hands-on’, ‘active’ and ‘problem-based learning’ within engineering courses. It is now widely accepted that traditional lectures ARE NOT best for students – yet that is what the community almost universally does. To address this issue we are developing new Desktop Learning Modules (DLMs) that contain miniaturized processes with a uniquely expandable electronic system to contend with known sensor systems/removable cartridges, as well as, unknown expansions to the project. We have shown that miniaturized mimics of industrial-scale equipment produce process data that agree with correlations developed for large-scale equipment. We are now adapting concepts shown efficacious in a single chemical engineering course to a variety of engineering classes within civil, mechanical, bio- and electrical engineering. Some examples of new hands-on learning applications in chemical engineering include a boiler / condenser and evaporative and shell & tube heat exchangers. In bioengineering, we are developing prognostic devices for separating Prostate Cancer Tumor Cells (PCTCs) from blood, sensing for the presence of PCTCs, a thermoregulation simulated limb cartridge for studying kinematics of heat flow and heat distribution in human extremities, and immunoaffinity neuron-like ion selective electrodes. In civil engineering, the DLMs illustrate open channel flow units and a solar powered Rankine cycle is underway in mechanical engineering. We are implementing DLMs along with team learning pedagogy. In this paper we will present technical aspects surrounding development of a large number of new learning cartridges. While the assessment strategies being developed are broadly applicable we will just present one instance, with the civil engineering cartridge, of the identification of misconceptions and experimental design for assessing the impact of the DLM on learning. The assessment includes a pre- and post-test assessment to determine improvement in understanding basic concepts and persistence and/or repair of misconceptions