Feedback control laws for highly maneuverable aircraft

The results of a study of the application of H infinity and mu synthesis techniques to the design of feedback control laws for the longitudinal dynamics of the High Angle of Attack Research Vehicle (HARV) are presented. The objective of this study is to develop methods for the design of feedback control laws which cause the closed loop longitudinal dynamics of the HARV to meet handling quality specifications over the entire flight envelope. Control law designs are based on models of the HARV linearized at various flight conditions. The control laws are evaluated by both linear and nonlinear simulations of typical maneuvers. The fixed gain control laws resulting from both the H infinity and mu synthesis techniques result in excellent performance even when the aircraft performs maneuvers in which the system states vary significantly from their equilibrium design values. Both the H infinity and mu synthesis control laws result in performance which compares favorably with an existing baseline longitudinal control law

Application of nonlinear feedback control theory to supermaneuverable aircraft

Controlled flight at extremely high angles of attack, far exceeding the stall angle, and/or at high angular rates is sometimes referred to as supermaneuvering flight. The objective was to examine methods for design of control laws for aircraft performing supermaneuvers. Since the equations which govern the motion of aircraft during supermaneuvers are nonlinear, this study concentrated on nonlinear control law design procedures. The two nonlinear techniques considered were Nonlinear Quadratic Regulator (NLQR) theory and nonlinear dynamic inversion. A conventional gain scheduled proportional plus integral (P + I) controller was also developed to serve as a baseline design typical of current control laws used in aircraft. A mathematical model of a generic supermaneuverable aircraft was developed from data obtained from the literature. A detailed computer simulation of the aircraft was also developed. This simulation allowed the flying of proposed supermaneuvers and was used to evaluate the performance of the control law designs and to generate linearized models of the aircraft at different flight conditions

Eigenspace techniques for active flutter suppression

The use of eigenspace techniques for the design of an active flutter suppression system for a hypothetical research drone is discussed. One leading edge and two trailing edge aerodynamic control surfaces and four sensors (accelerometers) are available for each wing. Full state control laws are designed by selecting feedback gains which place closed loop eigenvalues and shape closed loop eigenvectors so as to stabilize wing flutter and reduce gust loads at the wing root while yielding accepatable robustness and satisfying constrains on rms control surface activity. These controllers are realized by state estimators designed using an eigenvalue placement/eigenvector shaping technique which results in recovery of the full state loop transfer characteristics. The resulting feedback compensators are shown to perform almost as well as the full state designs. They also exhibit acceptable performance in situations in which the failure of an actuator is simulated

Engineered apoptotic nucleases for chromatin research

We have created new genomics tools for chromatin research by genetically engineering the human and mouse major apoptotic nucleases that are responsible for internucleosomal DNA cleavage, DNA fragmentation factor (DFF). Normally, in its inactive form, DFF is a heterodimer composed of a 45-kDa chaperone inhibitor subunit (DFF45 or ICAD), and a 40-kDa latent endonuclease subunit (DFF40 or CAD). Upon caspase-3 cleavage of DFF45, DFF40 forms active endonuclease homo-oligomers. Although Saccharomyces cerevisiae lacks DFF, expression of caspase-3 is lethal in this organism, but expression of the highly sequence-specific tobacco etch virus protease (TEVP) is harmless. Therefore, we inserted TEVP cleavage sites immediately downstream of the two caspase-3 cleavage sites within DFF45, generating a novel form of DFF (DFF-T) whose nuclease activity proved to be exclusively under the control of TEVP. We demonstrate that co-expression of TEVP and DFF-T under galactose control results in nucleosomal DNA laddering and cell death in S. cerevisiae. We also created synthetic DFF genes with optimized codons for high-level expression in Eschericia coli or S. cerevisiae. We further demonstrate the excellence of the synthetic gene products for in vitro mapping of the nucleosome positions and hypersensitive sites in specific genes such as the yeast PHO5

Mars transportation system

The University of Minnesota Advanced Space Design Program has developed a sample Mars exploration scenario. The purpose of the design project is to enhance NASA and university interaction, to provide fresh ideas to NASA, and to provide real world design problems to engineering students. The Mars Transportation System in this paper is designed to transport a crew of six astronauts to the Martian surface and return them to Low Earth Orbit (LEO) starting in the year 2016. The proposed vehicle features such advanced technologies as nuclear propulsion, nuclear power generation, and aerobraking. Three missions are planned. Orbital trajectories are of the conjunction class with an inbound Venus swingby providing a 60-day surface stay at Mars and an average total trip time of 520 days

Feedback control laws for highly maneuverable aircraft

During this year, we concentrated our efforts on the design of controllers for lateral/directional control using mu synthesis. This proved to be a more difficult task than we anticipated and we are still working on the designs. In the lateral-directional control problem, the inputs are pilot lateral stick and pedal commands and the outputs are roll rate about the velocity vector and side slip angle. The control effectors are ailerons, rudder deflection, and directional thrust vectoring vane deflection which produces a yawing moment about the body axis. Our math model does not contain any provision for thrust vectoring of rolling moment. This has resulted in limitations of performance at high angles of attack. During 1994-95, the following tasks for the lateral-directional controllers were accomplished: (1) Designed both inner and outer loop dynamic inversion controllers. These controllers are implemented using accelerometer outputs rather than an a priori model of the vehicle aerodynamics; (2) Used classical techniques to design controllers for the system linearized by dynamics inversion. These controllers acted to control roll rate and Dutch roll response; (3) Implemented the inner loop dynamic inversion and classical controllers on the six DOF simulation; (4) Developed a lateral-directional control allocation scheme based on minimizing required control effort among the ailerons, rudder, and directional thrust vectoring; and (5) Developed mu outer loop controllers combined with classical inner loop controllers

Development of tools for the analysis of messages in controlled social network environments

There is sometimes more demand for the attention of healthcare providers than there is supply to go around. This study evaluates a way to make expert mental health social workers more efficient at the task of moderating controlled access social network discussion boards. Sometimes, moderators need to make authoritative posts on these boards known as interventions. These are useful when needed but unnecessary interventions may degrade the benefits of organic discussion. For this study an automated decision aiding system (ADAS) tool was developed which provided the automated analysis and visualization of messages and message sentiment. This tool was designed as a means to make the expert moderators more efficient so more individuals could utilize a discussion board without proportional increase in expert moderators and the associated expense. This study determined that the custom designed automated decision-aiding system had no significant effect on participants determining if messages from such a discussion board are deserving of an intervention response for the measures of accuracy, elapsed time, or judgement confidence. The abstraction of context provided by the ADAS in this study is suspected to explain the lack of significant results, and future work would focus on identifying the level of context supply humans would require for the ADAS to have an effect

The Profumo affair in popular culture: The Keeler Affair (1963) and ‘the commercial exploitation of a public scandal’

This article demonstrates that the Profumo affair, which obsessed Britain for large parts of 1963, was not simply a political scandal, but was also an important cultural event. Focussing on the production of The Keeler Affair, a feature film that figured prominently in contemporary coverage of the scandal but which has been largely overlooked since, the article shows that this film emerged from a situation in which cultural entrepreneurs, many of them associated with the satire boom, sought to exploit the scandal for financial gain. Many Profumo-related cultural products found an audience, and thus formed an integral part of, and helped to shape public attitudes towards, the Profumo affair. However, these products did not go uncontested, and resistance to them, and especially to the idea that Keeler might benefit materially from her role in the scandal, speak to concerns about cultural mediations of sex, politics and humour in early-1960s Britain

Minnesat: GPS Attitude Determination Experiments Onboard a Nanosatellite

This paper presents an overview of the attitude determination experiments onboard the University of Minnesota nanosatellite, Minnesat. Minnesat is designed as a test bed for conducting ultra-short baseline GPS attitude determination experiments in Earth orbit. The primary scientific mission of the Minnesat project is to design, develop, and validate an ultra-short baseline GPS attitude determination (AD) system. Minnesat is equipped with a set of sensors to support two independent AD systems that are referred to as the Primary AD System and the GPS AD System. The Primary AD System blends measurements of inertial sensors with measurements of a three-axis magnetometer to estimate Minnesat’s attitude. The GPS AD System blends measurements of inertial sensors with differential carrier phase GPS measurements to estimate Minnesat’s attitude. The Primary AD System is used as a truth source to validate the GPS AD System

CT perfusion for lesion-symptom mapping in large vessel occlusion ischemic stroke

Background: Identifying eloquent regions associated with poor outcomes based on CT perfusion (CTP) may help inform personalized decisions on selection for endovascular therapy (EVT) in patients with large vessel occlusion (LVO) ischemic stroke. This study aimed to characterize the relationship between CTP-defined hypoperfusion and National Institutes of Health Stroke Scale (NIHSS) subitem deficits. Methods: Patients with anterior circulation LVO, baseline CTP, itemized NIHSS at presentation and 24 hours were included. CTP was analyzed using e-CTP (Brainomix, UK). Time to maximal contrast (Tmax) prolongation was defined as >6 s, and penumbra as the difference between Tmax and ischemic core (relative cerebral blood flow<30%). Voxel-lesion-symptom mapping was performed using sparse canonical correlation analysis. For each NIHSS subitem, and total NIHSS, the associations were plotted between Tmax voxels with baseline NIHSS, and penumbra voxels with delta NIHSS (24 hours minus baseline). Results: This study included 171 patients. Total NIHSS was predicted by hypoperfusion in left frontal cortex and subcortical white matter tracts. Voxels associated with neurological recovery were symmetrical and subcortical. Limb deficits were associated with respective motor cortex regions and descending motor tracts, with negative correlation within the contralateral hemispheres. A similar but smaller cluster of voxels within the penumbra was associated with NIHSS improvement. Language impairment correlated with left frontal cortex and superior temporal gyrus voxels. With the exception of dysarthria, significant associations were observed and more diffusely distributed in all other NIHSS subitems. Conclusions: These results demonstrate the feasibility of hypoperfusion-to-symptom mapping in LVO. Symptom-based mapping from presenting imaging could refine treatment decisions targeting specific neurological deficits