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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Total energy control system autopilot design with constrained parameter optimization

A description is given of the application of a multivariable control design method (SANDY) based on constrained parameter optimization to the design of a multiloop aircraft flight control system. Specifically, the design method is applied to the direct synthesis of a multiloop AFCS inner-loop feedback control system based on total energy control system (TECS) principles. The design procedure offers a structured approach for the determination of a set of stabilizing controller design gains that meet design specifications in closed-loop stability, command tracking performance, disturbance rejection, and limits on control activities. The approach can be extended to a broader class of multiloop flight control systems. Direct tradeoffs between many real design goals are rendered systematic by proper formulation of the design objectives and constraints. Satisfactory designs are usually obtained in few iterations. Performance characteristics of the optimized TECS design have been improved, particularly in the areas of closed-loop damping and control activity in the presence of turbulence.

Ly, Uy-Loi↗
NASA NTRS1984

A frequency domain stability analysis of a phase plane control system

A describing function is used to model a phase plane controller which is part of the Space Shuttle on-orbit Reaction Control System autopilot. A frequency domain stability analysis of the closed-loop control system is applied to a study of potential flight control system interaction with the Orbiter and a class of payloads deployed from a tilt table. Phase-gain plot techniques are used to show that expansion of phase plane angular rate limits and stiffening of the tilt table pivot do not always enhance system stability. Instability region approximations are mapped as a function of rate limit, payload geometry, jet used, and natural frequency of the pivot. Comparison of the describing function analysis with simulation results shows excellent correlation.

Hattis, P. D.↗
NASA NTRS1978

Floating-point system quantization errors in digital control systems

This paper considers digital controllers (filters) operating in floating-point arithmetic in either open-loop or closed-loop systems. A quantization error analysis technique is developed, and is implemented by a digital computer program that is based on a digital simulation of the system. The program can be integrated into existing digital simulations of a system.

Phillips, C. L.↗
NASA NTRS2017

Spaceport Command and Control System Software Development

The Spaceport Command and Control System (SCCS) is the National Aeronautics and Space Administration's (NASA) launch control system for the Orion capsule and Space Launch System, the next generation manned rocket currently in development. This large system requires a large amount of intensive testing that will properly measure the capabilities of the system. Automating the test procedures would save the project money from human labor costs, as well as making the testing process more efficient. Therefore, the Exploration Systems Division (formerly the Electrical Engineering Division) at Kennedy Space Center (KSC) has recruited interns for the past two years to work alongside full-time engineers to develop these automated tests, as well as innovate upon the current automation process.

Glasser, Abraham↗
NASA NTRS1986

Design of adaptive control systems by means of self-adjusting transversal filters

The design of closed-loop adaptive control systems based on nonparametric identification was addressed. Implementation is by self-adjusting Least Mean Square (LMS) transversal filters. The design concept is Model Reference Adaptive Control (MRAC). Major issues are to preserve the linearity of the error equations of each LMS filter, and to prevent estimation bias that is due to process or measurement noise, thus providing necessary conditions for the convergence and stability of the control system. The controlled element is assumed to be asymptotically stable and minimum phase. Because of the nonparametric Finite Impulse Response (FIR) estimates provided by the LMS filters, a-priori information on the plant model is needed only in broad terms. Following a survey of control system configurations and filter design considerations, system implementation is shown here in Single Input Single Output (SISO) format which is readily extendable to multivariable forms. In extensive computer simulation studies the controlled element is represented by a second-order system with widely varying damping, natural frequency, and relative degree.

Merhav, S. J.↗
NASA NTRS1980

Phase control system concepts and simulations

A phase control system concept for a solar power satellite is proposed which partitions the system into three major levels. The first level of phase control consists of a reference phase distribution system implemented in the form of phase distribution tree structure. The major purpose of the tree structure is to electronically compensate for the phase shift due to the transition path lengths from the center of the spacetenna to each phase control center located in each subarray. In the reference system, this is accomplished using the master slave returnable timing system technique. The second level of phase control consists of the beam steering and microwave power generating system which houses the power transponders. This transponder consists of a set of phase conjugation multipliers driven by the reference phase distribution system output and the output of a pilot spread spectrum receiver which accepts the received pilot via a diplexer connected to a separate receive horn or the subarray itself. The output of the phase conjugation circuits serve as inputs to the third level of the phase control system. The third level of phase control is associated with maintaining an equal and constant phase shift through the microwave power amplifier devices while minimizing the associated phase noise effects on the generated power beam. This is accomplished by providing a phase locked loop around each high power amplifier.

Lindsay, V. C.↗
NASA NTRS1976

The F-12 series aircraft approach to design for control system reliability

The F-12 series aircraft control system design philosophy is reviewed as it pertains to functional reliability. The basic control system, i.e., cables, mixer, feel system, trim devices, and hydraulic systems are described and discussed. In addition, the implementation of the redundant stability augmentation system in the F-12 aircraft is described. Finally, the functional reliability record that has been achieved is presented.

Schenk, F. L.↗
NASA NTRS1990

Thermal control system corrosion study

During the development of an expert system for autonomous control of the Space Station Thermal Control System (TCS), the thermal performance of the Brassboard TCS began to gradually degrade. This degradation was due to filter clogging by metallic residue. A study was initiated to determine the source of the residue and the basic cause of the corrosion. The investigation focused on the TCS design, materials compatibility, Ames operating and maintenance procedures, and chemical analysis of the residue and of the anhydrous ammonia used as the principal refrigerant. It was concluded that the corrosion mechanisms involved two processes: the reaction of water alone with large, untreated aluminum parts in a high pH environment and the presence of chlorides and chloride salts. These salts will attack the aluminum oxide layer and may enable galvanic corrosion between the aluminum and the more noble stainless steel and other metallic elements present. Recommendations are made for modifications to the system design, the materials used, and the operating and maintenance procedures, which should largely prevent the recurrence of these corrosion mechanisms.

Yee, Robert↗
NASA NTRS2014

Launch Control System Message Reduction

System Monitoring and Control (SMC) message browsers receive many messages daily that operators do not need to see. My job is to reduce the number of messages so that warning and emergency messages can be seen easily and therefore, responded to promptly. There are two methods to reduce messages: duplicate and state-based message correlations. With duplicate message correlation, SMC display the message the first time it shows up. The next times it occurs, a duplicate number will count the number of times the message appears. State-based message correlation is a process in which more informative messages acknowledge less useful ones and send them to history. I also work on correcting the severity level and text formats of messages. I follow two SMC message filtering tenets as I'm working on this project. Firstly, before filtering an offending message, a non-conformance (NC) must be created in order to attempt fixing that message through hardware or software. Only after the NC assessment states that it cannot fix an offending message, it can be filtered by SMC. Secondly, per Launch Control System (LCS) Coding Standards, SMC does not send information messages to the active message browser unless it's a response to an operator action.

correlation↗
NASA NTRS2006

Development and Flight Testing of a Neural Network Based Flight Control System on the NF-15B Aircraft

The Intelligent Flight Control System (IFCS) project at the NASA Dryden Flight Research Center, Edwards AFB, CA, has been investigating the use of neural network based adaptive control on a unique NF-15B test aircraft. The IFCS neural network is a software processor that stores measured aircraft response information to dynamically alter flight control gains. In 2006, the neural network was engaged and allowed to learn in real time to dynamically alter the aircraft handling qualities characteristics in the presence of actual aerodynamic failure conditions injected into the aircraft through the flight control system. The use of neural network and similar adaptive technologies in the design of highly fault and damage tolerant flight control systems shows promise in making future aircraft far more survivable than current technology allows. This paper will present the results of the IFCS flight test program conducted at the NASA Dryden Flight Research Center in 2006, with emphasis on challenges encountered and lessons learned.

Bomben, Craig R.↗
NASA NTRS2019

Command and Control System Software Development

With the first launch of the National Aeronautics and Space Administration's Space Launch System heavy-lift expendable launch vehicle and Lockheed Martin's Orion Multi-Purpose Crew Vehicle scheduled for the year 2020, there exists a need to complete development of a new command and control system that will provide systems monitoring and launch control for NASA's Exploration Missions. One remaining task necessary for completion of this command and control system is to create and maintain comprehensive unit tests of the control system software packages. These tests should verify that the implementation of all required and desired functionality works as intended. This testing infrastructure is mostly in place, but the control system's open source automation server still reports software "bugs" (possible flaws or failures which may lead to unintended behavior) and intermittently failing unit tests. Since code correctness is of critical importance for human rated software systems, I was assigned to diagnose the root cause of failing unit tests, eliminate non-determinism in these tests, and fix bugs as reported by the automation server.

GUI↗
NASA NTRS1985

Advanced thermal-control systems as applied to future NASA spacecraft

It is pointed out that active thermal control systems can theoretically provide a more isothermal spacecraft at less power and weight than required by conventional passive systems. The present paper is concerned with a study of the advantages, with respect to weight and power savings, which can be achieved by using active thermal control systems in future NASA spacecraft. In the study, a prototype NASA spacecraft, based on the Upper Atmosphere Research Satellite (UARS), is considered. In order to represent thermal requirements of future spacecraft, the UARS requirements were modified for the prototype, which was called AEOS (advanced earth-orbiting spacecraft). Five types of active thermal-control systems were considered. The results which can be obtained with the different thermal-control systems are compared.

Bravo, C. L.↗
NASA NTRS1986

Initial design and evaluation of automatic restructurable flight control system concepts

Results of efforts to develop automatic control design procedures for restructurable aircraft control systems is presented. The restructurable aircraft control problem involves designing a fault tolerance control system which can accommodate a wide variety of unanticipated aircraft failure. Under NASA sponsorship, many of the technologies which make such a system possible were developed and tested. Future work will focus on developing a methodology for integrating these technologies and demonstration of a complete system.

Weiss, J. L.↗
NASA NTRS2011

Propulsive Reaction Control System Model

This software models a propulsive reaction control system (RCS) for guidance, navigation, and control simulation purposes. The model includes the drive electronics, the electromechanical valve dynamics, the combustion dynamics, and thrust. This innovation follows the Mars Science Laboratory entry reaction control system design, and has been created to meet the Mars Science Laboratory (MSL) entry, descent, and landing simulation needs. It has been built to be plug-and-play on multiple MSL testbeds [analysis, Monte Carlo, flight software development, hardware-in-the-loop, and ATLO (assembly, test and launch operations) testbeds]. This RCS model is a C language program. It contains two main functions: the RCS electronics model function that models the RCS FPGA (field-programmable-gate-array) processing and commanding of the RCS valve, and the RCS dynamic model function that models the valve and combustion dynamics. In addition, this software provides support functions to initialize the model states, set parameters, access model telemetry, and access calculated thruster forces.

Brugarolas, Paul↗
NASA NTRS1995

Micro-Precision Interferometer: Pointing Control System

This paper describes the development of the wavefront tilt (pointing) control system for the JPL Micro-Precision Interferometer (MPI). This control system employs piezo-electric actuators and a digital imaging sensor with feedback compensation to reject errors in instrument pointing. Stringent performance goals require large feedback, however, several characteristics of the plant tend to restrict the available bandwidth. A robust 7th-order wavefront tilt control system was successfully implemented on the MPI instrument, providing sufficient disturbance rejection performance to satisfy the established interference fringe visibility.

Micro-Precision Pointing↗
NASA NTRS2004

A Study on the Requirements for Fast Active Turbine Tip Clearance Control Systems

This paper addresses the requirements of a control system for active turbine tip clearance control in a generic commercial turbofan engine through design and analysis. The control objective is to articulate the shroud in the high pressure turbine section in order to maintain a certain clearance set point given several possible engine transient events. The system must also exhibit reasonable robustness to modeling uncertainties and reasonable noise rejection properties. Two actuators were chosen to fulfill such a requirement, both of which possess different levels of technological readiness: electrohydraulic servovalves and piezoelectric stacks. Identification of design constraints, desired actuator parameters, and actuator limitations are addressed in depth; all of which are intimately tied with the hardware and controller design process. Analytical demonstrations of the performance and robustness characteristics of the two axisymmetric LQG clearance control systems are presented. Takeoff simulation results show that both actuators are capable of maintaining the clearance within acceptable bounds and demonstrate robustness to parameter uncertainty. The present model-based control strategy was employed to demonstrate the tradeoff between performance, control effort, and robustness and to implement optimal state estimation in a noisy engine environment with intent to eliminate ad hoc methods for designing reliable control systems.

DeCastro, Jonathan A.↗