Showing papers by "National Aerospace Laboratories published in 1992"

Fast and efficient variable-to-fixed length coding algorithm

Abstract: Variable-to-fixed-length coding implementations, according to the Tunstall algorithm, are shown to be significantly less complex than fixed-to-variable-length coding schemes such as the Huffman scheme. A modified version of Tunstall coding is presented, with improved compression ratio.

A robust quasi-simultaneous interaction method for a full potential flow with a boundary layer with application to wing/body configurations

Abstract: The MATRICS flow solver calculates the inviscid transonic potential flow about a wing/body semi-configuration. At present, work is in progress to extend MATRICS to take viscous effects into account through coupling with a boundary layer solver. This solver, MATRICS-V, is based on robust calculation methods for the boundary layer, the outer wing flow and their interaction. MATRICS-V is intended for (inverse) design purposes. The boundary layer and wake are based on an integral formulation of the unsteady first order boundary layer equations, the inviscid method is the existing MATRICS potential flow solver, and the interaction algorithm is of the quasi-simultaneous type. The paper gives a progress report on the coupled potential-flow boundary-layer method for transonic wing/body configurations.

Microprocessor-based controller for actuators in structural testing

Abstract: A dedicated microprocessor-based controller was developed for low-speed multichannel structural testing. The controller was designed to be mounted on the actuator and for remote calibration, tuning, and programming. It includes electronics for signal conditioning and servoloop control, programmable waveform generation, and data acquisition, as well as handshake lines for synchronous operation with other actuators. Computer-controller communication is through a serial daisy-chained interface that permits multiactuator programming through a single communication port on the host computer system.

HUD Guidance for the ASKA Experimental STOL Aircraft using Radar Position Information

Abstract: The paper describes a high performance HUD guidance system installed on the experimental powered-lift STOL aircraft Aska. Since the maiden flight in October 1985, the HUD system has been used in all the flight tests. The HUD has an accurate flight path symbol generated by inertial velocity from the IRS which is updated by up-linked precision radar position data. The flight path symbol is very useful for precise approach and flare control for Aska which has large ground effects. A synthetic runway is also presented, which is conformal with the real runway, using the position data from the ground tracking radar system. Under instrument meteorological conditions, the pilot can approach and land using the HUD synthetic runway as well as in visual meteorological conditions. The HUD system proved to be a valuable aid to the pilot for all the Aska flight tests. A NASA Ames Research Center test pilot demonstrated touch down accuracy of less than 8 meters (peak to peak) for a series of three landings.