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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Effect of manipulator and feel system characteristics on pilot performance in roll tracking

The control system features of force vs displacement stick command, feel/force displacement gradient, 'feel' system vs command prefilter dynamic lag, and flight control system effective time delay, have been investigated by a fixed-base simulation employing both joysticks and side-sticks in order to ascertain their effect on pilot opinion, pilot performance, and their hand/arm neuromuscular subsystem interaction. The results obtained indicate that the use of displacement sensing added the feel system dynamic lag to the command path and increased effective system flight delay, thereby lowering pilot opinion and performance but reducing the possibility of roll instability; the use of force sensing as stick command to exclude feel system dynamic lag had the obverse effect.

Aponso, Bimal L.↗
NASA NTRS1988

Simulator evaluation of takeoff performance monitoring system displays

The development of head-up and head-down cockpit displays to convey symbolic status and advisory information to the pilot to aid him in his decision to continue or abort takeoff is described. It also describes a pilot-in-the-loop evaluation of the displays using the NASA Langley transport systems research vehicle fixed-base simulator. It was found that the head-up display was monitored with little effort and did not obstruct or distract from the runway scene.

Middleton, David B.↗
NASA NTRS1987

A virtual manipulator model for space robotic systems

Future robotic manipulators carried by a spacecraft will be required to perform complex tasks in space, like repairing satellites. Such applications of robotic manipulators will encounter a number of kinematic, dynamic and control problems due to the dynamic coupling between the manipulators and the spacecraft. A new analytical modeling method for studying the kinematics and dynamics of manipulators in space is presented. The problem is treated by introducing the concept of a Virtual Manipulator (VM). The kinematic and dynamic motions of the manipulator, vehicle and payload, can be described relatively easily in terms of the Virtual Manipulator movements, which have a fixed base in inertial space at a point called a Virtual Ground. It is anticipated that the approach described here will aid in the design and development of future space manipulator systems.

Dubowsky, S.↗
NASA NTRS1988

Design considerations of manipulator and feel system characteristics in roll tracking

A fixed-base simulation was performed to identify and quantify interactions between the pilot's hand/arm neuromuscular subsystem and such control system features of typical modern fighter aircraft roll rate command mechanizations as: (1) force versus displacement sensing side-stick type manipulator, (2) feel force/displacement gradient, (3) feel system versus command prefilter dynamic lag, and (4) flight control system effective time delay. The experiment encompassed some 48 manipulator/filter/aircraft configurations. Displacement side-stick experiment results are given and compared with the previous force sidestick experiment results. Attention is focused on control bandwidth, excitement (peaking) of the neuromuscular mode, feel force/displacement gradient effects, time delay effects, etc. Section 5 is devoted to experiments with a center-stick in which force versus displacement sensing, feel system lag, and command prefilter lag influences on tracking performance and pilot preference are investigated.

Johnston, Donald E.↗
NASA NTRS1988

A mass additive technique for modal testing as applied to the Space Shuttle ASTRO-1 payload

Traditionally, a fixed base modal test has been performed as a means of verifying the coupled loads math model for Space Shuttle flight payloads. An alternate method, a free-free configured payload using mass loaded boundary conditions, is presented as a means of verifying the coupled loads model of the ASTRO-1 flight payload. This method allows evaluation of the influence of local load paths into the frequency range of the free-free test. The method is cost effective and does not contaminate the modal test results with fixture coupled modes or boundary condition uncertainties. This paper describes the mass additive modal test technique as applied to the Space Shuttle ASTRO-1 flight payload.

Coleman, A. D.↗
NASA NTRS1988

A piloted simulation investigation of yaw dynamics requirements for turreted gun use in low-level helicopter air combat

A piloted, fixed-base simulation study was conducted to investigate the handling qualities requirements for helicopter air-to-air combat using turreted guns in the near-terrain environment. The study used a version of the helicopter air combat system developed at NASA Ames Research Center for one-on-one air combat. The study focused on the potential trade-off between gun angular movement capability and required yaw axis response. Experimental variables included yaw axis response frequency and damping and the size of the gun-movement envelope. A helmet position and sighting system was used for pilot control of gun aim. Approximately 340 simulated air combat engagements were evaluated by pilots from the Army and industry. Results from the experiment indicate that a highly-damped, high frequency yaw response was desired for Level I handling qualities. Pilot preference for those characteristics became more pronounced as gun turret movement was restricted; however, a stable, slow-reacting platform could be used with a large turret envelope. Most pilots preferred to engage with the opponent near the own-ship centerline. Turret elevation restriction affected the engagement more than azimuth restrictions.

Decker, William A.↗
NASA NTRS1988

Progress in utilization of a mobile laboratory for making storm electricity measurements

A mobile atmospheric science laboratory has been used to intercept and track storms on the Great Plains region of the U.S., with the intention of combining the data obtained with those from Doppler and conventional radars, NASA U-2 aircraft overflights, balloon soundings, and fixed-base storm electricity measurements. The mobile lab has proven to be valuable in the gathering of ground truth verifications for the two commercially operated lightning ground-strike locating systems. Data acquisition has recently been expanded by means of mobile ballooning before and during storms.

Rust, W. David↗
NASA NTRS1990

General-Purpose Data-Formatting Input/Output System

Multiplexable input/output (I/O) system developed as interface between host computer and real-time, fixed-base simulator cockpit. Unit designed to be general-purpose interface and operated through virtually any 8- or 16-bit, transistor/transistor-logic-level, parallel-I/O port with or without handshaking. Accepts byte-coded data in form of data blocks from host computer and routes data to various system I/O modules like discrete outputs, lamp drivers, and seven-segment-display drivers. Formats and routes data from input modules back to host computer. Other modules designed to drive alphanumeric displays and communications interfaces and to serve as analog-to-digital and digital-to-analog converter modules.

Busquets, Anthony M.↗
NASA NTRS1989

Shape control of high degree-of-freedom variable geometry trusses

Common static trusses are constrained to permit no relative motion between truss elements. A Variable Geometry Truss (VGT), however, is a truss which contains some number of variable length links. The extensible links allow the truss to change shape in a precise, controllable manner. These changes can also be used to control the vibrational response of a truss structure or to perform robotic tasks. Many geometric configurations, both planar and spatial, are possible candidates for VGT manipulators. Here, only two geometries are discussed; the three degree-of-freedom (DOF) spatial octahedral/octahedral truss and the three DOF planar tetrahedral truss. These truss geometries are used as the fundamental element in a repeating chain of trusses. This results in a highly dexterous manipulator with perhaps 30 to 60 degrees of freedom that retains the favorable stiffness properties of a conventional truss. From a fixed base, this type of manipulator could perform shape or vibration control while extending and snaking through complex passageways or moving around obstacles to perform robotic tasks. The approach taken here is to first concentrate on fully understanding the forward and inverse kinematics of the fundamental elements and then utilizing the insight thus gained to solve the more complex problem of the kinematic chains.

Salerno, R. J.↗
NASA NTRS1989

Flight/propulsion control integration for V/STOL fighter/attack aircraft

A NASA-defined technology program investigating integrated flight/propulsion control system design for vertical and short takeoff and landing (V/STOL) aircraft is outlined, and initial fixed-base simulation experiments for two V/STOL aircraft are covered. It is shown that transition performance can be characterized by the minimum climb or level-flight acceleration that can be achieved. Level-1 flying qualities can be achieved for deceleration to hover in instrument conditions, and for shore-based and shipboard landing when attitude and velocity stabilization and command augmentation modes are provided. Level-1 and Level-2 flying qualities can be expected when only attitude command is provided. During vertical landing aboard a destroyer in heavy seas, substantial bleed flow rates are reported for a control arrangement employing reaction control for the pitch, roll, and yaw axes. Peak bleed flows can be reduced for a control arrangement using lateral-thrust transfer for roll control.

Franklin, James A.↗
NASA NTRS1989

Simulation evaluation of transition and hover flying qualities of a mixed-flow, remote-lift STOVL aircraft

Using a generalized simulation model developed for piloted evaluations of STOVL aircraft, an initial fixed-base simulation of a mixed-flow, remote-lift configuration has been completed. Objectives were to evaluate the integration of the aircraft's flight and propulsion controls to achieve good flying qualities throughout the low-speed flight envelope; to determine control power used during transition, hover, and vertical landing; and to evaluate the transition flight envelope considering the influence of thrust deflection of the remote-lift component. Pilots' evaluations indicated that Level 1 flying qualities could be achieved for deceleration to hover in instrument conditions, for airfield landings, and for recovery to a small ship when attitude and velocity stabilization and command augmentation control modes were provided. Level 2 flying qualities were obtained for these same tasks when only the attitude command mode was used, leaving the pilot to perform the task of thrust management required to control the flight-path and speed in transition and the horizontal and vertical translational velocities in hover. Thrust margins were defined for vertical landing as a function of ground effect and hot-gas ingestion.

Franklin, James A.↗
NASA NTRS1991

The NASA Lewis integrated propulsion and flight control simulator

A new flight simulation facility was developed at NASA-Lewis. The purpose of this flight simulator is to allow integrated propulsion control and flight control algorithm development and evaluation in real time. As a preliminary check of the simulator facility capabilities and correct integration of its components, the control design and physics models for a short take-off and vertical landing fighter aircraft model were shown, with their associated system integration and architecture, pilot vehicle interfaces, and display symbology. The initial testing and evaluation results show that this fixed based flight simulator can provide real time feedback and display of both airframe and propulsion variables for validation of integrated flight and propulsion control systems. Additionally, through the use of this flight simulator, various control design methodologies and cockpit mechanizations can be tested and evaluated in a real time environment.

Bright, Michelle M.↗
NASA NTRS1990

On the nature of control algorithms for space manipulators

A study of the characteristics of control algorithms that can be applied to the motion control of space manipulators is reported. The results obtained show that nearly any control algorithm that can be applied to conventional terrestrial fixed-base manipulators, with a few additional conditions, can be directly applied to free-floating space manipulators. Barycenters are used to formulate efficiently the kinematic and dynamic equations of free-floating space manipulators. A control algorithm for a space manipulator system is designed to demonstrate the value of the analysis.

Papadopoulos, Evangelos↗
NASA NTRS1989

On the dynamic singularities in the control of free-floating space manipulators

It is shown that free-floating space manipulator systems have configurations which are dynamically singular. At a dynamically singular position, the manipulator is unable to move its end effector in some direction. This problem appears in any free-floating space manipulator system that permits the vehicle to move in response to manipulator motion without correction from the vehicle's attitude control system. Dynamic singularities are functions of the dynamic properties of the system; their existence and locations cannot be predicted solely from the kinematic structure of the manipulator, unlike the singularities for fixed base manipulators. It is also shown that the location of these dynamic singularities in the workplace is dependent upon the path taken by the manipulator in reaching them. Dynamic singularities must be considered in the control, planning and design of free-floating space manipulator systems. A method for calculating these dynamic singularities is presented, and it is shown that the system parameters can be selected to reduce the effect of dynamic singularities on a system's performance.

Papadopoulos, E.↗
NASA NTRS1991

Optimal input design for aircraft instrumentation systematic error estimation

A new technique for designing optimal flight test inputs for accurate estimation of instrumentation systematic errors was developed and demonstrated. A simulation model of the F-18 High Angle of Attack Research Vehicle (HARV) aircraft was used to evaluate the effectiveness of the optimal input compared to input recorded during flight test. Instrumentation systematic error parameter estimates and their standard errors were compared. It was found that the optimal input design improved error parameter estimates and their accuracies for a fixed time input design. Pilot acceptability of the optimal input design was demonstrated using a six degree-of-freedom fixed base piloted simulation of the F-18 HARV. The technique described in this work provides a practical, optimal procedure for designing inputs for data compatibility experiments.

Morelli, Eugene A.↗
NASA NTRS1991

Effect of lift-to-drag ratio upon pilot rating for a preliminary version of the HL-20 lifting body

A man-in-the-loop simulation study of the handling qualities of the HL-20 lifting body vehicle has been performed in a fixed-base simulation cockpit. The study was aimed at identifying opportunities to improve the original design of the vehicle from a handling qualities and landing performance perspective. A subsonic aerodynamic model of the HL-20 was used as a baseline, and visual approaches and landings were made at various vehicle lift-to-drag (L/D) ratios. It is concluded that there is a high degree of correlation between maximum L/D ratio and pilot rating. Using the pilot ratings Level 1, flying qualities were found to be possible for configurations with a maximum L/D ratio of 3.8 or higher.

Jackson, E. B.↗
NASA NTRS1991

The NASA Lewis integrated propulsion and flight control simulator

A new flight simulation facility has been developed at NASA Lewis to allow integrated propulsion-control and flight-control algorithm development and evaluation in real time. As a preliminary check of the simulator facility and the correct integration of its components, the control design and physics models for an STOVL fighter aircraft model have been demonstrated, with their associated system integration and architecture, pilot vehicle interfaces, and display symbology. The results show that this fixed-based flight simulator can provide real-time feedback and display of both airframe and propulsion variables for validation of integrated systems and testing of control design methodologies and cockpit mechanizations.

Bright, Michelle M.↗
NASA NTRS1991

The effect of global visual flow on simulator sickness

Simulator-induced sickness is investigated in experiments performed at the NASA Ames Army Crew Station Research Facility using the fixed-base helmet-mounted-display flight simulator described by Lypaczewski et al. (1986). The focus of the tests was on the possible roles of (1) global visual flow, as defined by Warren et al. (1982), and (2) maneuvering intensity (in the conflict hypothesis of Reason and Brand, 1975). The results, based on subjective evaluations, physiological measurements, and physical tests on 19 Army helicopter pilots performing a 40-min river-valley following task, are presented in extensive tables and graphs and discussed. The data are found to be in agreement with (1) and inconsistent with (2), indicating more sickness at lower altitude instead of with increased maneuvering. Shorter simulator sessions and postponement of low-altitude work until later in the training period are recommended.

Sharkey, Thomas J.↗