Simple adaptive control for aircraft control surface failures

This work extends the so-called simple adaptive control approach to direct model reference adaptive control of multi-input multi-output systems to include loss of control effectiveness failures. It is proven that all signals are bounded for loss of control effectiveness failures during a bounded input disturbance. A state space approach is introduced for computing the feedforward compensator that is required by the stability result. The adaptive algorithm is applied to a three input model of the linearized lateral dynamics of the F/A-18 aircraft. Simulation results are obtained with single, double, and triple control effectiveness failures of 88% during the occurrence of a lateral gust. These results show that the adaptive controller exhibits improved model following as compared with a fixed gain eigenstructure assignment controller.     

The evolution of mirror type magnetic fluctuations in the magnetosheath based on multipoint observations

Two orbits were selected in January–February 2006 when the separation between the Cluster spacecraft was large and mirror type magnetic field fluctuations were observed by all spacecraft in different regions of the terrestrial magnetosheath. Minimum variance analysis was applied to find the mirror type fluctuations, and the amplitude of the fluctuations was determined individually. Mirror mode structures are moving along the streamlines frozen in the plasma. A model was developed for the calculation of plasma flowtime from the bow shock to the observation point. The growth rate of the field strength perturbations was estimated by comparing the amplitudes of fluctuations observed simultaneously at distant locations (∼10,000 km) based on the assumption that δB ∼ exp(γt). The obtained growth rate values were about an order of magnitude smaller than those provided by linear models and they decreased in the inner regions of the magnetosheath, indicating some saturation in the growth of the waves when proceeding towards the magnetopause. The results of these two case studies suggest that mirror type fluctuations originate from the compression region downstream of the quasi-perpendicular bow shock, and the growth of the fluctuations cannot be described by linear approximations.     

Space science education in Egypt and the 2006 solar eclipse

The space science research has been started in Egypt since 1910 by measuring the solar constant as indication of solar radiation at Helwan Observatory. The solar sunspot studies and its influence on the Nile flooding was erected and operated at Helwan as a first solar station in Egypt during 1957. Zeiss-Coude’ refractor was installed in 1964. Astronomy and space science educations started in Egypt at the university level since 1936 at Department of Astronomy and Meteorology of Cairo University. Undergraduate and graduate education in Egypt will be discussed in this work.     

Testing the Stability of the Fine Structure Constant in the Laboratory

In this review we discuss the progress of the past decade in testing for a possible temporal variation of the fine structure constant α. Advances in atomic sample preparation, laser spectroscopy and optical frequency measurements led to rapid reduction of measurement uncertainties. Eventually laboratory tests became the most sensitive tool to detect a possible variation of α at the present epoch. We explain the methods and technologies that helped to make this possible.     

Integrated Planning and Execution for Autonomous Spacecraft

An autonomous spacecraft must balance long-term and short-term considerations. It must perform purposeful activities that ensure long-term science and engineering goals are achieved and ensure that it maintains positive resource margins. This requires planning in advance to avoid a series of shortsighted decisions that can lead to failure. However, it must also respond in a timely fashion to a somewhat dynamic and unpredictable environment. Thus, in terms of high-level, goal-oriented activity, spacecraft plans must often be modified due to fortuitous events such as early completion of observations and setbacks such as failure to acquire a guidestar for a science observation. This describes an integrated planning and execution architecture that supports continuous modification and updating of a current working plan in light of a changing operating context.     

Improved Accuracy Metallic Resonator CVG

Metallic resonator Q-factor is very sensitive to the resonator's material, its thermal and chemical treatment, design, and environment; i.e., pressure and temperature. In order to obtain higher accuracy for CVG it is necessary to use resonator evacuation. Resonator mass plays a very important role in sensitivity to angle rate, in stability of vibration, in response to environmental condition changes, and also to external vibration and shock resistance. tnnalabs Holding Inc. uses a cylindrical resonator with increased rim thickness of up to 2 mmn and more. This concerns resonator material and design parameters selection, material thermal treatment to increase resonator Q-factor, and improved control algorithms in order to increase metallic CVG accuracy. As a result, CVG bias instability of 0.025 degth and random walk of 0.008 degvh for the resonator diameter 43 mmn, and 0.2 deg/h for the resonator diameter 25 mm were obtained. Future opportunities for Innalabs CVG is also discussed herein. Test results are presented for CVG43 and CVG25. Three-axis CVG unit under control of one DSP "Sharc" and IMU parameters are forecasted.     

Launch Envelope Optimization of Virtual Sliding Target Guidance Scheme

This paper presents an optimization of the performance of a recently proposed virtual sliding target (VST) guidance scheme in terms of maximization of its launch envelope for three-dimensional (3-D) engagements. The objective is to obtain the launch envelope of the missile using the VST guidance scheme for different lateral launch angles with respect to the line of sight (LOS) and demonstrate its superiority over kinematics-based guidance laws like proportional navigation (PN). The VST scheme uses PN as its basic guidance scheme and exploits the relation between the atmospheric properties, missile aerodynamic characteristics, and the optimal trajectory of the missile. The missile trajectory is shaped by controlling the instantaneous position and the speed of a virtual target which the missile pursues during the midcourse phase. In the proposed method it is shown that an appropriate value of initial position for the virtual target in 3-D, combined with optimized virtual target parameters, can significantly improve the launch envelope performance. The paper presents the formulation of the optimization problem, obtains the approximate models used to make the optimization problem more tractable, and finally presents the optimized performance of the missile in terms of launch envelope and shows significant improvement over kinematic-based guidance laws. The paper also proposes modification to the basic VST scheme. Some simulations using the full-fledged six degrees-of-freedom (6-DOF) models are also presented to validate the models and technique used.     

Biogenerated Rock Structures

Earth as a planet under firm control of life processes since more than 3 Ga has evolved global biogeochemical cycles, biogeomorphogenetic processes and structures also called plates or global tectonics including global climate and movement of water masses. These processes have deep impact on the shape and thickness of continental land masses as well as the chemistry and mineralogy of the crust and upper mantle. Biogenerated rock structures in this sense can be visualised through the analysis of sedimentary rock structures exhibiting e.g., biogenerated stromatolites, onkolites, oolites or cementing structures of sandstones which clearly preserve biochemical processes and biophysical structures. Further the chemical composition including the segregation of mineral layers, ore deposits, sedimentary and metamorphic rocks and granites hint to sun powered energy storage (gas, gas hydrates, hydrocarbons, coal) and tectonic processes initiated or at least modified through the enormous input of external energy through reduced carbon and iron compounds. One can state with considerable reliability that a planet under control of life must exhibit rock chemistry, mineralogy and structures typical for the impact of life on the geodynamic cycles. This includes the idea of top-down geotectonics instead of bottom-up processes.     

Kalman Filter Applications in Airborne Radar Tracking

This paper studies the application of Kalman filtering to single-target track systems in airborne radar. An angle channel Kalman filter is configured which incorporates measures of range, range rate, and on-board dynamics. Theoretical performance results are given and a discussion of methods for reducing the complexity of the Kalman gain computation is presented. A suboptimal antenna controller which operates on the outputs of the angle Kalman filter is also described. In addition, methodological improvements are shown to exist in the design of range and range-rate trackers using the Kalman filter configuration.