Engineering topics

Whitmore, S. A.

Publications and source records attributed to Whitmore, S. A..

6 records

NASA NTRS1985

Formulation and implementation of nonstationary adaptive estimation algorithm with applications to air-data reconstruction

The dynamics model and data sources used to perform air-data reconstruction are discussed, as well as the Kalman filter. The need for adaptive determination of the noise statistics of the process is indicated. The filter innovations are presented as a means of developing the adaptive criterion, which is based on the true mean and covariance of the filter innovations. A method for the numerical approximation of the mean and covariance of the filter innovations is presented. The algorithm as developed is applied to air-data reconstruction for the space shuttle, and data obtained from the third landing are presented. To verify the performance of the adaptive algorithm, the reconstruction is also performed using a constant covariance Kalman filter. The results of the reconstructions are compared, and the adaptive algorithm exhibits better performance.

Whitmore, S. A.↗

NASA NTRS1985

Formulation and implementation of nonstationary adaptive estimation algorithm with applications to air-data reconstruction

The dynamics model and data sources used to perform air-data reconstruction are discussed, as well as the Kalman filter. The need for adaptive determination of the noise statistics of the process is indicated. The filter innovations are presented as a means of developing the adaptive criterion, which is based on the true mean and covariance of the filter innovations. A method for the numerical approximation of the mean and covariance of the filter innovations is presented. The algorithm as developed is applied to air-data reconstruction for the Space Shuttle, and data obtained from the third landing are presented. To verify the performance of the adaptive algorithm, the reconstruction is also performed using a constant covariance Kalman filter. The results of the reconstructions are compared, and the adaptive algorithm exhibits better performance.

Whitmore, S. A.↗

NASA NTRS1984

Flight and wind-tunnel comparisons of the inlet-airframe interaction of the F-15 airplane

The design of inlets and nozzles and their interactions with the airplane which may account for a large percentage of the total drag of modern high performance aircraft is discussed. The inlet/airframe interactions program and the flight tests conducted is described. Inlet drag and lift data from a 7.5% wind-tunnel model are compared with data from an F-15 airplane with instrumentation to match the model. Pressure coefficient variations with variable cowl angles, capture ratios, examples of flow interactions and angles of attack are for Mach numbers of 0.6, 0.9, 1.2, and 1.5 are presented.

Webb, L. D.↗

NASA NTRS1984

Air data position-error calibration using state reconstruction techniques

During the highly maneuverable aircraft technology (HiMAT) flight test program recently completed at NASA Ames Research Center's Dryden Flight Research Facility, numerous problems were experienced in airspeed calibration. This necessitated the use of state reconstruction techniques to arrive at a position-error calibration. For the HiMAT aircraft, most of the calibration effort was expended on flights in which the air data pressure transducers were not performing accurately. Following discovery of this problem, the air data transducers of both aircraft were wrapped in heater blankets to correct the problem. Additional calibration flights were performed, and from the resulting data a satisfactory position-error calibration was obtained. This calibration and data obtained before installation of the heater blankets were used to develop an alternate calibration method. The alternate approach took advantage of high-quality inertial data that was readily available. A linearized Kalman filter (LKF) was used to reconstruct the aircraft's wind-relative trajectory; the trajectory was then used to separate transducer measurement errors from the aircraft position error. This calibration method is accurate and inexpensive. The LKF technique has an inherent advantage of requiring that no flight maneuvers be specially designed for airspeed calibrations. It is of particular use when the measurements of the wind-relative quantities are suspected to have transducer-related errors.

Whitmore, S. A.↗

NASA NTRS1983

Reconstruction of the shuttle reentry air data parameters using a linearized Kalman filter

This paper presents the reconstruction of the space shuttle's wind-relative reentry trajectory for the orbital flights. The technique uses a linearized Kalman filter (LKF) to merge highand low-frequency inertial and wind-relative data to obtain enhanced high-frequency results that closely follow expected mean levels. Two verifications are presented. First, wind trajectories resulting from the reconstruction are compared with analytically predicted values. There is close comparison. Second, the frequency characteristics are investigated using system identification techniques. The stability and control model generated using the LKF trajectory shows good agreement between measured and predicted spacecraft response for both high and low frequencies.

Whitmore, S. A.↗

NASA NTRS1979

Preliminary flight and wind tunnel comparisons of the inlet/airframe interaction of the F-15 airplane

Preliminary flight and wind tunnel comparison data are presented for the F-15 inlet/airframe interactions program. Test conditions and instrumentation for both the model and the aircraft are described. Flight and wind tunnel inlet drag data (for a 0-deg angle of attack and Mach numbers of 0.6, 0.9, and 1.2), derived by using nearly identical pressure integration equations, are compared. The effects of a movable cowl, movable ramps, and other system components on pressure flow fields along the airframe are discussed. Excellent agreement between wind tunnel and flight pressure-integrated drags is found at all three Mach numbers. The wind tunnel data show good agreement for pressure-integrated and force-balance-measured inlet drag, except at Mach 0.6. Flight-measured pressure-integrated inlet lift is lower than that measured in the wind tunnel.

Webb, L. D.↗