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Results for “pointing control”

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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Impacts of Control Set-Points on Battery Energy Storage Performance for Peak Shaving Application

This article presents the impact of battery energy storage system’s (BESS) control triggers on its performance during peak shaving application. With the increasing deployment of BESS for load leveling and grid capacity relief, the sensitivity of BESS performance to its set-points is yet to be investigated. Most utilities have defined thresholds for activating BESS control during peak demand leveling and baseload BESS charging. However, this study shows that without using optimal setpoints for control applications, the BESS can be under-utilized. Simulations results of the peak shaving algorithm implementation in 30-minute time step over a period of 10 years show the impact of different set-points on distribution transformer loading, line and system losses.

battery energy storage system↗
NASA NTRS1984

Rectification of single and multiple frames of satellite scanner imagery using points and edges as control

Rectification of single and overlapping multiple scanner frames produced by such satellite-borne scanners as the LANDSAT MSS was carried out using a newly developed comprehensive parametric model. Tests with both simulated and real image data demonstrate conclusively that this model in general is superior to the widely used polynomial model, and that the simultaneous rectification of overlapping frames using least squares techniques yields a high accuracy than sngle frame rectification due to the inclusion of tie points between the image frames. Used to control, edges or lines, whic are much more likely to be found in images, can replace conventional control points and can easily be implemented into the least squares approach. An efficient algorithm for findng corresponding points in image paris was developed which can be used for determining tie points between image frames and thus increase the ecnomy of the whole rectification procedure.

Paderes, F. C., Jr.↗
DOE OSTI2020

Virtual synchronous generator system and method with virtual inertia control

A virtual synchronous generator device disclosed. The device includes an inverter and inverter controller having a power control portion, a power reserve portion, a power point tracking control portion, and a virtual inertia control portion. The power reserve portion determines an amount of power to be reserved and sends a signal, indicative of the determined amount of power to the power point tracking controller. The power point tracking controller determines a power point that is less than a MPP, and provides a signal to the power control portion indicative of the determined power point. The inertia control portion determines a virtual inertia and provides a signal indicative of the virtual inertia to the power control portion. The power control portion provides a power control signal to the inverter based on the power point tracking signal and the inertia command signal.

42 ENGINEERING↗
NASA NTRS1975

ATS-6 - Spacecraft Attitude Precision Pointing and Slewing Adaptive Control Experiment

The primary objective of the Spacecraft Attitude Precision Pointing and Slewing Adaptive Control (SAPPSAC) experiment is to establish feasibility and evaluate capabilities of a ground-based spacecraft attitude control system, wherein RF command and telemetry links, together with a ground station on-line minicomputer, perform closed loop attitude control of the Applications Technology Satellite-6 (ATS-6). The ground processor is described, including operational characteristics and the controller software. Attitude maneuvers include precision pointing to fixed targets, slewing between targets, and generation of prescribed ground tracks. Test results show high performance and reliability for over 30 hours of on-line control with no serious anomalies. Attitude stabilization relative to a prescribed target has been achieved to better than 0.007 deg in pitch and roll and 0.02 deg in yaw for a period of 43 min. Ground tracks were generated which had maximum latitude/longitude deviations less than 0.15 deg from reference.

Isley, W. C.↗
DOE OSTI2023

Operational control with set-points tuning - application to mobile robots

This paper proposes a novel method for the optimal tuning of set points for multiple-layered control system structure widely seen in robotics and other complex industrial processes composed of a number of subsystems. The terminal sliding mode control (SMC) is used as the low-level control strategy to ensure the stability of subsystems. When uncertainties exist, it can be shown that the deteriorated system performance will be improved by the outer loop with set points tuning. For this purpose, the learning of the new set point is designed to compensate for the effects caused by uncertainties during the system operation. At the same time, the system is proven to stay with the original set point when the compensation is introduced. A practical application to a holonomic mobile robot system is given to illustrate the presented method. Desired results have been obtained.

42 ENGINEERING↗
NASA NTRS1979

Application of Model Reference Adaptive Control System to Instrument Pointing System /IPS/

A Model Reference Adaptive Controller (MRAC) is derived for a Shuttle payload called the Instrument Pointing System (IPS). The unique features of this MRAC design are that total state feedback is not required, that the internal structure of the model is independent of the internal structure of the IPS, and that the model input is of bounded variation and not required a priori. An application of Liapunov's stability theorems is used to synthesize a control signal which assures MRAC asymptotic stability. Exponential observers are used to obtain the necessary state information to implement the control synthesis. Results are presented which show how effectively the MRAC can maneuver the IPS.

Waites, H. B.↗
NASA NTRS1974

Stabilization, pointing and command control of a balloon-borne 1-meter telescope

A 1-meter balloon-borne telescope has been constructed and flown to observe far-infrared radiation from celestial sources. The attitude control systems must perform to the diffraction limit of the telescope for stabilization and have positioning capability for source acquisition. These and associated systems are discussed in detail, as is the command control of the payload as a whole.

Hazen, N. L.↗
NASA NTRS1993

Control of libration point orbits using lunar gravity-assisted transfer

The Interplanetary Physics Laboratory, WIND, will be placed in a small-amplitude halo orbit in late 1995. A lunar swingby is used to achieve the halo orbit. Using the lunar swingby reduces the fuel required to achieve the desired orbit. The spacecraft's position and velocity with respect to the Moon near the time of swingby are shown to determine the characteristics of the halo orbit. The shape of the halo orbit, its x-, y-, and z-amplitudes, must be designed to meet mission constraints. A convenient set of parameters for displaying the dependence of the halo orbit's shape upon the lunar swingby is formulated. The use of the lunar swingby adds additional constraints to the trajectory in terms of attainable swingby parameters. Strategies for obtaining the desired swingby parameters in view of these mission constraints are discussed. The limits on attainable halo orbit shapes using the lunar swingby technique are discussed in terms of minimum and maximum x-, y-, and z-amplitudes. The relevance of previous work on this topic is discussed.

Sharer, P.↗
NASA NTRS1992

Comparison of computer- and human-derived coronary angiographic end-point measures for controlled therapy trials

The Cholesterol Lowering Atherosclerosis Study, a randomized angiographic clinical trial, demonstrated the beneficial effect of niacin/colestipol plus diet therapy on coronary atherosclerosis. Outcome was determined by panel-based estimates (viewed in both still and cine modes) of percent stenosis severity and change in native artery and bypass graft lesions. Computer-based quantitative coronary angiography (QCA) was also used to measure lesion and bypass graft stenosis severity and change in individual frames closely matched in orientation, opacification, and cardiac phase. Both methods jointly evaluated 350 nonoccluded lesions. The correlation between QCA and panel estimates of lesion size was 0.70 (p less than 0.0001) and for change in lesion size was 0.28 (p = 0.002). Agreement between the two methods in classifying lesion changes (i.e., regression, unchanged, or progression) occurred for 60% (210 of 350) of the lesions kappa +/- SEM = 0.20 +/- 0.05, p less than 0.001). The panel identified 442 nonoccluded lesions for which QCA stenosis measurements could not be obtained. Lesions not measurable by QCA included those with stenosis greater than 85% that could not be reliably edge tracked, segments with diffuse or ecstatic disease that had no reliable reference diameter, and segments for which matched frames could not be located. Seventy-nine lesions, the majority between 21% and 40% stenosis, were identified and measured by QCA but were not identified by the panel. This comparison study demonstrates the need to consider available angiographic measurement methods in relation to the goals of their use.

NASA Center JPL↗
NASA NTRS2003

Control of node crossing points in Saturnian gravity-assist tours

In the Saturnian system, the control of the node crossing point is important to avoid debris in Saturn's ring plane and to target flybys of moons other than Titan. This paper describes how to use Titan gravity assists to control the spacecraft's node crossing point.

Saturn node crossing point flyby Titan gravity ass↗
NASA NTRS1978

Digital controller design: Analysis of the annular suspension pointing system

The analog controllers of the annular suspension pointing system are designed for control of the chi, phi sub 1, and phi sub 2 bandwidth dynamics through decoupling and pole placement. Since it is virtually impossible to find an equivalent bandwidth of the overall system and establish a general eigenvalue requirement for the system, the subsystem dynamics are decoupled through state feedback and the poles are placed simultaneously to realize the desired bandwidths for the three system components. Decoupling and pole placement are also used to design the closed-loop digital system through approximation.

Kuo, B. C.↗
NASA NTRS1989

Control-structure interaction in precision pointing servo loops

The control-structure interaction problem is addressed via stability analysis of a generic linear servo loop model. With the plant described by the rigid body mode and a single elastic mode, structural flexibility is categorized into one of three types: (1) appendage, (2) in-the-loop minimum phase, and (3) in-the-loop nonminimum phase. Closing the loop with proportional-derivative (PD) control action and introducing sensor roll-off dynamics in the feedback path, stability conditions are obtained. Trade studies are conducted with modal frequency, modal participation, modal damping, loop bandwidth, and sensor bandwidth treated as free parameters. Results indicate that appendage modes are most likely to produce instability if they are near the sensor rolloff, whereas in-the-loop modes are most dangerous near the loop bandwidth. The main goal of this paper is to provide a fundamental understanding of the control-structure interaction problem so that it may benefit the design of complex spacecraft and pointing system servo loops. In this framework, the JPL Pathfinder gimbal pointer is considered as an example.

Spanos, John T.↗
NASA NTRS1989

The Circumstellar Imaging Telescope image motion compensation system - Ultra-precise control on the Space Station platform

The Circumstellar Imaging Telescope (CIT) is a 1.9 m visible wavelength Cassegrain instrument whose primary mission is to locate extra-solar planets by direct imaging. The current reference concept calls for it to be deployed as a Space Station attached payload some time in the late 1990s. Mission and signal processing demands impose the following attitude control requirements: pointing accuracy - 250 nrad RMS, pointing stability - 50 nrad RMS over 30 minutes, roll accuracy - 1 mrad RMS, roll stability 1 mrad RMS over 30 minutes. This paper reports on the results of a recent design study in which it was determined that these requirements can be met on the Space Station by a three tiered control system consisting of a two degree of freedom mechanical gimbal for course pointing, a magnetically suspended roll bearing for roll accommodation, translational isolation and intermediate pointing control, and articulation of the secondary mirror for fine pointing.

Sevaston, G. E.↗
NASA NTRS1982

Improved pointing at trackable targets by integrating control valve signals

A compact, low-cost add-on electronic module has been developed for the STRAP III control system to improve pointing at trackable targets. The module provides peak-to-peak limit cycle excursions of + or - 5 arcseconds while tracking a +3 magnitude or brighter star. This is achieved without using rate-integrating gyroscopes, thus reducing payload length, weight, cost, and preparation time. This module has flown successfully five times. In May 1981, it improved the performance of a two-startracker attitude control system with TV camera and joystick control which pointed at a nontrackable target. This paper describes the operation of the module, how it alters the ordinary STRAP III operation, and how it was developed using an analog-computer-based rocket flight simulator.

Stone, R. W.↗
NASA NTRS1996

Using Fast-Steering Mirror Control to Reduce Instrument Pointing Errors Caused by Spacecraft Jitter

The scope of this study was to investigate the benefit of using feedback control of a Fast Steering Mirror (FSM) to reduce instrument pointing errors. Initially, the study identified FSM control technologies and categorized them according to their use, range of applicability, and physical requirements. Candidate payloads were then evaluated according to their relevance in use of fast steering minor control technologies. This leads to the mission and instrument selection which served as the candidate mission for numerical modeling. A standard SmallSat was designed in order to accommodate the payload requirements (weight, size, power, etc.). This included sizing the SmallSat bus, sizing the solar array, choosing appropriate antennas, and identifying an attitude control system (ACS). A feedback control system for the FSM compensation was then designed, and the instrument pointing error and SmallSat jitter environment for open-loop and closed-loop FSM control were evaluated for typical SmallSat disturbances. The results were then compared to determine the effectiveness of the FSM feedback control system.

Antol, Jeffery↗