Bending feedback control Final report
Application of quadratic optimal control, least squares state, and parameter estimation to stability and control of flexible launch vehicle
OPTIMAL CONTROL↗
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Solution of the algebraic matrix Riccati equation via Newton-Raphson iteration.
Algebraic matrix Ricatti equation solution via Newton-Raphson iteration algorithm, noting application to quadratic optimal controller and least square state estimator
Blackburn, T. R.↗
New Jacobi-type necessary and sufficient conditions for singular optimization problems
Jacobi conditions for singular optimization problems by transforming singular accessory minimum problem into nonclassical nonsingular form, considering optimal control theory applicability
Mcdanell, J. P.↗
Command and data handling for Atmosphere Explorer satellite
The command and data-handling subsystem of the Atmosphere Explorer satellite provides the necessary controls for the instrumentation and telemetry, and also controls the satellite attitude and trajectory. The subsystem executes all command information within the spacecraft, either in real time (as received over the S-band command transmission link) or remote from the command site (as required by the orbit operations schedule). Power consumption in the spacecraft is optimized by suitable application and removal of power to various instruments; additional functions include control of magnetic torquers and of the orbit-adjust propulsion subsystem. Telemetry data from instruments and the spacecraft equipment are formatted into a single serial bit stream. Attention is given to command types, command formats, decoder operation, and command processing functions.
Fuldner, W. V.↗
State-space formulations for flutter analysis
Various methods are presented and assessed for approximating the aerodynamic forces so that the State Space formulation and off-the-imaginary axis analysis are retained. The advantages of retaining these features are considerable, not only in simplifying the flutter analysis, but especially for more advanced applications such as optimal design of active control in which the flutter is merely a constraint to the optimization problem.
Weiss, S. J.↗
Reduced state feedback gain computation
Because application of conventional optimal linear regulator theory to flight controller design requires the capability of measuring and/or estimating the entire state vector, it is of interest to consider procedures for computing controls which are restricted to be linear feedback functions of a lower dimensional output vector and which take into account the presence of measurement noise and process uncertainty. Therefore, a stochastic linear model that was developed is presented which accounts for aircraft parameter and initial uncertainty, measurement noise, turbulence, pilot command and a restricted number of measurable outputs. Optimization with respect to the corresponding output feedback gains was performed for both finite and infinite time performance indices without gradient computation by using Zangwill's modification of a procedure originally proposed by Powell. Results using a seventh order process show the proposed procedures to be very effective.
Kaufman, H.↗
Research and development for improved lead-salt diode lasers
A substantial increase in output power levels for lead-salt diode lasers, through the development of improved fabrication methods, as demonstrated. The goal of 1 mW of CW, single-mode, single-ended power output, was achieved, with exceptional devices exhibiting values greater than 8 mW. It was found that the current tuning rate could be controlled by adjusting the p-n junction depth, allowing the tuning rate to be optimized for particular applications. An unexpected phenomenon was encountered when crystal composition was observed to be significantly altered by annealing at temperatures as low as 600 C; the composition was changed by transport of material through the vapor phase. This effect caused problems in obtaining diode lasers with the desired operating characteristics. It was discovered that the present packaging method introduces gross damaging effects in the laser crystal through pressure applied by the C-bend.
Butler, J. F.↗
Analytical display design for flight tasks conducted under instrument meteorological conditions
A relatively straightforward, nearly algorithmic procedure for deriving model-based pilot-centered display requirements is presented. A pilot model based on modern control theory serves as the backbone of the design methodology, which is specifically directed toward the synthesis of head-down, electronic cockpit display formats. Some novel applications of the optimal pilot model are discussed, including the generation of vehicle-handling-qualities levels via numerical pilot-opinion ratings. An analytical design example is offered which aids in the definition of a format for the electronic display to be used in a UH-1H helicopter in a landing-approach task involving longitudinal and lateral degrees of freedom. It is proposed that the design procedure offers a systematic means for generating candidate display formats and flight-director laws for simulator evaluation.
Hess, R. A.↗
Determination of navigation FDI thresholds using a Markov model
A method for determining time-varying Failure Detection and Identification (FDI) thresholds for single sample decision functions is described in the context of a triplex system of inertial platforms. A cost function consisting of the probability of vehicle loss due to FDI decision errors is minimized. A discrete Markov model is constructed from which this cost can be determined as a function of the decision thresholds employed to detect and identify the first and second failures. Optimal thresholds are determined through the use of parameter optimization techniques. The application of this approach to threshold determination is illustrated for the Space Shuttle's inertial measurement instruments.
Walker, B. K.↗
Analysis of integral controls in linear quadratic regulator design
The application of linear optimal control to the design of systems with integral control action on specified outputs is considered. Using integral terms in a quadratic performance index, an asymptotic analysis is used to determine the effect of variable quadratic weights on the eigenvalues and eigenvectors of the closed loop system. It is shown that for small integral terms the placement of integrator poles and gain calculation can be effectively decoupled from placement of the primary system eigenvalues. This technique is applied to the design of integral controls for a STOL aircraft outer loop guidance system.
Slater, G. L.↗
Effect of display size on utilization of traffic situation display for self-spacing task
The weather radar cathode ray tube (CRT) is the prime candidate for presenting cockpit display of traffic information (CDTI) in current, conventionally equipped transport aircraft. Problems may result from this, since the CRT size is not optimized for CDTI applications and the CRT is not in the pilot's primary visual scan area. The impact of display size on the ability of pilots to utilize the traffic information to maintain a specified spacing interval behind a lead aircraft during an approach task was studied. The five display sizes considered are representative of the display hardware configurations of airborne weather radar systems. From a pilot's subjective workload viewpoint, even the smallest display size was usable for performing the self spacing task. From a performane viewpoint, the mean spacing values, which are indicative of how well the pilots were able to perform the task, exhibit the same trends, irrespective of display size; however, the standard deviation of the spacing intervals decreased (performance improves) as the display size increased. Display size, therefore, does have a significant effect on pilot performance.
Abbott, T. S.↗
Pilot guidance and display considerations for energy efficient flight profiles
Two computer programs are applied to energy efficient flight operation in order to minimize aircraft operating costs. One algorithm (OPTIM) computes vertical flight profiles which optimize direct operating costs, including fuel and time costs, for an aircraft flying over a fixed range and with a fixed time-of-arrival. The second program (TRAGEN) simulates an aircraft steered to fly along a specified vertical flight trajectory, in order to examine fuel and cost penalties involved in flying nonoptimal trajectories. Constraints such as air traffic control procedures, and atmospheric and weight conditions are considered and supported by graphs and diagrams. The use of the algorithms as preflight planning tools is discussed, emphasizing OPTIM's future application for on-board energy management. Finally, research questions concerning pilot guidance and display considerations for advanced energy/flight management systems are addressed.
Samms, K. H.↗
Minimum cost criteria for SPS transportation to GEO
The application of cost optimization to vehicle design is discussed relative to establishing ground rules for a minimum cost heavy cargo launch vehicle to transport the Satellite Power System to geosynchronous orbit. Criteria defined include: fully reusable; unmanned; technical simplicity; and operations simplicity. Graphs are presented depicting (1) the launch vehicle concept schematic, (2) the cost comparison, (3) the launch vehicle sizing, and (4) the specific transportation cost.
Koelle, D. E.↗
Control of large flexible spacecraft by the independent modal-space control method
The problem of control of a large-order flexible structure in the form of a plate-like lattice by the Independent Modal-Space Control (IMSC) method is presented. The equations of motion are first transformed to the modal space, thus obtaining internal (plant) decoupling of the system. Then, the control laws are designed in the modal space for each mode separately, so that the modal equations of motion are rendered externally (controller) decoupled. This complete decoupling applies both to rigid-body modes and elastic modes. The application of linear optimal control, in conjunction with a quadratic performance index, is first reviewed. A solution for high-order systems is proposed here by the IMSC method, whereby the problem is reduced to a number of modal minimum-fuel problems for the controlled modes.
Meirovitch, L.↗
Electrical power systems for Space Station
Major challenges in power system development are described. Evolutionary growth, operational lifetime, and other design requirements are discussed. A pictorial view of weight-optimized power system applications shows which systems are best for missions of various lengths and required power level. Following definition of the major elements of the electrical power system, an overview of element options and a brief technology assessment are presented. Selected trade-study results show end-to-end system efficiencies, required photovoltaic power capability as a function of energy storage system efficiency, and comparisons with other systems such as a solar dynamic power system.
Simon, W. E.↗
Equivalent plate analysis of aircraft wing box structures with general planform geometry
A new equilvalent plate analysis formulation is described which is capable of modeling aircraft wing structures with a general planform such as cranked wing boxes. Multiple trapezoidal segments are used to represent such planforms. A Ritz solution technique is used in conjunction with global displacement functions which encompass all the segments. This Ritz solution procedure is implemented efficiently into a computer program so that it can be used by rigorous optimization algorithms for application in early preliminary design. A direct method to interface this structural analysis procedure with aerodynamic programs for use in aeroelastic calculations is described. This equivalent plate analysis procedure is used to calculate the static deflections and stresses and vibration frequencies and modes of an example wing configuration. The numerical results are compared with results from a finite element model of the same configuration to illustrate typical levels of accuracy and computation times resulting from use of this procedure.
Giles, G. L.↗
A research program in active control/aeroelasticity
In this research period a synthesis methodology for multifunctional robust aeroservoelastic systems was developed. The development consisted of the following stages: (1) development of an universal diagram to determine phase and gain margins of a multi-input multi-output (MIMO) system using singular value based stability margin criteria; (2) determination of singular value gradients with respect to design parameters and their application to improve stability margins of multiloop system; and (3) application of constrained optimization techniques to synthesize a low order robust controller for a high order MIMO aeroservoelastic system while satisfying several design constraints on the dynamic loads and responses and stability margins at the plant input and output. Overall research activities are summarized.
Source record↗
Solid-propellant rocket motor internal ballistics performance variation analysis, phase 5
The results of research aimed at improving the predictability of internal ballistics performance of solid-propellant rocket motors (SRM's) including thrust imbalance between two SRM's firing in parallel are presented. Static test data from the first six Space Shuttle SRM's is analyzed using a computer program previously developed for this purpose. The program permits intentional minor design biases affecting the imbalance between any two SMR's to be removed. Results for the last four of the six SRM's, with only the propellant bulk temperature as a non-random variable, are generally within limits predicted by theory. Extended studies of internal ballistic performance of single SRM's are presented based on an earlier developed mathematical model which includes an assessment of grain deformation. The erosive burning rate law used in the model is upgraded and made more general. Excellent results are obtained in predictions of the performances of five different SRM's of quite different sizes and configurations. These SRM's all employ PBAN type propellants with ammonium perchlorate oxidizer and 16 to 20% aluminum except one which uses carboxyl terminated butadiene binder. The only non-calculated parameters in the burning rate equations that are changed for the different SRM's are the zero crossflow velocity burning rate coefficients and exponents. The results, in general, confirm the importance of grain deformation. The improved internal ballistic model makes practical development of an effective computer program for application of an optimization technique to SRM design which is also demonstrated. The program uses a pattern search technique to minimize the difference between a desired thrust-time trace and one calculated based on the internal ballistic model.
Sforzini, R. H.↗