Digital receiver study and implementation

Computer software was developed which makes it possible to use any general purpose computer with A/D conversion capability as a PSK receiver for low data rate telemetry processing. Carrier tracking, bit synchronization, and matched filter detection are all performed digitally. To aid in the implementation of optimum computer processors, a study of general digital processing techniques was performed which emphasized various techniques for digitizing general analog systems. In particular, the phase-locked loop was extensively analyzed as a typical non-linear communication element. Bayesian estimation techniques for PSK demodulation were studied. A hardware implementation of the digital Costas loop was developed

Real time flight simulation methodology

An example sensitivity study is presented to demonstrate how a digital autopilot designer could make a decision on minimum sampling rate for computer specification. It consists of comparing the simulated step response of an existing analog autopilot and its associated aircraft dynamics to the digital version operating at various sampling frequencies and specifying a sampling frequency that results in an acceptable change in relative stability. In general, the zero order hold introduces phase lag which will increase overshoot and settling time. It should be noted that this solution is for substituting a digital autopilot for a continuous autopilot. A complete redesign could result in results which more closely resemble the continuous results or which conform better to original design goals

Formation Feedback Control of UAV Flight

This thesis is a study of formation control with autonomous unmanned aerial vehicles using the formation as feedback. There is also an investigation of formation methods presenting insight into different algorithms for formations. A rigid formation is achieved using a proportional-derivative virtual structure with a formation feedback controller. There is an emphasis on stick controlled aerodynamics. The rigid formation is verified by a simulation of a longitudinal model. Formation control ideas are presented for rigid formations

Control and structural optimization for maneuvering large spacecraft

Presented here are the results of an advanced control design as well as a discussion of the requirements for automating both the structures and control design efforts for maneuvering a large spacecraft. The advanced control application addresses a general three dimensional slewing problem, and is applied to a large geostationary platform. The platform consists of two flexible antennas attached to the ends of a flexible truss. The control strategy involves an open-loop rigid body control profile which is derived from a nonlinear optimal control problem and provides the main control effort. A perturbation feedback control reduces the response due to the flexibility of the structure. Results are shown which demonstrate the usefulness of the approach. Software issues are considered for developing an integrated structures and control design environment

Distributed control strategy for DC microgrids based on average consensus and fractional-order local controllers

A novel distributed secondary layer control strategy based on average consensus and fractional-order proportional-integral (FOPI) local controllers is proposed for the regulation of the bus voltages and energy level balancing of the energy storage systems (ESSs) in DC microgrids. The distributed consensus protocol works based on an undirected sparse communication network. Fractional-order local controllers increase the degree of freedom in the tuning of closed-loop controllers, which is required for DC microgrids with high order dynamics. Therefore, here, FOPI local controllers are proposed for enhanced energy balancing of ESSs and improved regulation of the bus voltages across the microgrid. The proposed control strategy operates in both islanded and grid-connected modes of a DC microgrid. In both modes, the average voltage of the microgrid converges to the microgrid desired reference voltage. The charging/discharging of ESSs is controlled independent of the microgrid operating mode to maintain a balanced energy level. The performance of the proposed distributed control strategy is validated in a 38- V DC microgrid case study, simulated by Simulink real-time desktop, consisting of 10 buses and a photovoltaic renewable energy source

Cortical Dynamics of Navigation and Steering in Natural Scenes: Motion-Based Object Segmentation, Heading, and Obstacle Avoidance

Visually guided navigation through a cluttered natural scene is a challenging problem that animals and humans accomplish with ease. The ViSTARS neural model proposes how primates use motion information to segment objects and determine heading for purposes of goal approach and obstacle avoidance in response to video inputs from real and virtual environments. The model produces trajectories similar to those of human navigators. It does so by predicting how computationally complementary processes in cortical areas MT-/MSTv and MT+/MSTd compute object motion for tracking and self-motion for navigation, respectively. The model retina responds to transients in the input stream. Model V1 generates a local speed and direction estimate. This local motion estimate is ambiguous due to the neural aperture problem. Model MT+ interacts with MSTd via an attentive feedback loop to compute accurate heading estimates in MSTd that quantitatively simulate properties of human heading estimation data. Model MT interacts with MSTv via an attentive feedback loop to compute accurate estimates of speed, direction and position of moving objects. This object information is combined with heading information to produce steering decisions wherein goals behave like attractors and obstacles behave like repellers. These steering decisions lead to navigational trajectories that closely match human performance.National Science Foundation (SBE-0354378, BCS-0235398); Office of Naval Research (N00014-01-1-0624); National Geospatial Intelligence Agency (NMA201-01-1-2016

Identification and control of structures in space

Work during the period January 1 to June 30, 1985 has concentrated on the completion of the derivation of the equations of motion for the Spacecraft Control Laboratory Experiment (SCOLE) as well on the development of a control scheme for the maneuvering of the spacecraft. The report consists of a paper presented at the Fifth Symposium on Dynamics and Control of Large Structures, June 12 to 14, 1985 at Blacksburg, VA

Wearable kinesthetic system for capturing and classifying upper limb gesture in post-stroke rehabilitation

BACKGROUND: Monitoring body kinematics has fundamental relevance in several biological and technical disciplines. In particular the possibility to exactly know the posture may furnish a main aid in rehabilitation topics. In the present work an innovative and unobtrusive garment able to detect the posture and the movement of the upper limb has been introduced, with particular care to its application in post stroke rehabilitation field by describing the integration of the prototype in a healthcare service. METHODS: This paper deals with the design, the development and implementation of a sensing garment, from the characterization of innovative comfortable and diffuse sensors we used to the methodologies employed to gather information on the posture and movement which derive from the entire garments. Several new algorithms devoted to the signal acquisition, the treatment and posture and gesture reconstruction are introduced and tested. RESULTS: Data obtained by means of the sensing garment are analyzed and compared with the ones recorded using a traditional movement tracking system. CONCLUSION: The main results treated in this work are summarized and remarked. The system was compared with a commercial movement tracking system (a set of electrogoniometers) and it performed the same accuracy in detecting upper limb postures and movements

Modeling the "microbial chassis effect" on the performance of a genetic switch

Escherichia coli is one of the most established bacterial hosts for genetic devices, partially due to the available knowledge and tools for ease of manipulation. However, there is an incentive to increase the current number of available recipients. For instance, marine bacteria are being recognized for their potential as microbial "chassis" due to their rich genetic and metabolic diversity. With this in mind, tools for simulating the behavior of genetic devices would help synthetic biology expand its reach to untraditional hosts. Hence, here in this study, the effect of recipient on the performance of a genetic switch, the "chassis" effect, was estimated across different bacteria with an aim to indicate the possibilities of marine microorganisms as hosts. The device considered in this study was assembled from two sub-parts 1) L-arabinose-inducible PBAD promoter that expresses tetR and gfp genes encoding production of the TetR repressor and GFP fluorescent protein; and 2) anhydrotetracycline (aTc)-inducible PTet promoter that controls araC and mKate expression, which codes for the AraC repressor and mKate fluorescent protein. AraC protein is a repressor of the PBAD promoter, while TeR represses PTet. The dynamic behavior and stability of this device was simulated by a mathematical model based on a system of ordinary differential equations (ODEs) that predicted possible "chassis" effect and compared its strength across selected bacterial hosts. To further our understanding of the performance of a genetic switch, a dynamic modeling framework was established, and a behavior was simulated for a set of marine bacteria and E. coli. This was done by building a mathematical model that included system of already parametrized non-linear ODEs which were solved using the R programming language. The parametrization of ODEs by a non-linear model resulted in the Hill (n) and activation (K) coefficient estimates. The non-linear regression was performed on a GFP fluorescence data collected from the induction study with E. coli. This assay estimated GFP-, GFP/OD600 signals and GFP rates from the cells induced with L-arabinose. The simulated dynamic response was quantified by a response time, a limiting factor for designing efficient gene circuits. The simulation estimated the fastest response of Vibrio natriegens and the slowest of Pseudomonas oceani. This outcome has indicated high potentials of V. natriegens for future applications in the synthetic biology. The "chassis" effect predicted by the model was estimated as a direct consequence of the specific growth rate

HYBRID GPS/SINS SYSTEM - AN OVERVIEW

This paper describes a hybrid navigation system consisting of an integrated GPS/INS system. The integration of the navigation systems has been performed to improve the accuracy of the navigation parameters and it is a current trend in the world. The need for continuous navigation, during the change of position of the GPS receiver, during the closing time of the GPS receiving antenna, and during the appearance of interference, has imposed a solution that is achieved by the integration of GPS / INS. The role of SINS, which is part of the integrated GPS / INS navigation system, is to determine the navigation parameters at intervals between two adjacent measurements of GPS receivers, i.e., at times when there is no GPS navigation information for any reason. In this way, GPS and INS, when used together, complement and correct each other, significantly increasing the reliability and accuracy of the hybrid navigation system