Influence of unsteady aerodynamics on rotor blade aeroelastic stability and response
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Friedmann, P. P.↗
Engineering topics
Robinson, L. H.
Publications and source records attributed to Robinson, L. H..
Analytic simulation of higher harmonic control using a new aeroelastic model
This paper describes a higher harmonic control (HHC) study of a four bladed hingeless rotor using a coupled flap-lag-torsional aeroelastic stability and response analysis which incorporates finite-state, time-domain aerodynamics. The rotor trim condition is determined using a coupled trim-aeroelastic analysis. Deterministic and cautious controllers based on local and global HHC models are implemented with different combinations of input parameters identified using a Kalman filter. The effects of unsteady versus quasisteady aerodynamic modeling on HHC simulations are investigated, including the effectiveness of the local and global HHC models and the advantages of different identification schemes.
Friedmann, P. P.↗
Influence of time domain unsteady aerodynamics on coupled flap-lag-torsional aeroelastic stability and response of rotor blades
This paper describes the incorporation of finite-state, time-domain aerodynamics in a flag-lag-torsional aeroelastic stability and response analysis in forward flight. Improvements to a previous formulation are introduced which eliminate spurious singularities. The methodology for solving the aeroelastic stability and response problems with augmented states, in the time domain, is presented using an implicit formulation. Results describing the aeroelastic behavior of soft and stiff in-plane hingeless rotor blades, in forward flight, are presented to illustrate the sensitivity of both the stability and response problems to time domain unsteady aerodynamics.
Friedmann, P. P.↗
ASTP ranging system mathematical model
A mathematical model is presented of the VHF ranging system to analyze the performance of the Apollo-Soyuz test project (ASTP). The system was adapted for use in the ASTP. The ranging system mathematical model is presented in block diagram form, and a brief description of the overall model is also included. A procedure for implementing the math model is presented along with a discussion of the validation of the math model and the overall summary and conclusions of the study effort. Detailed appendices of the five study tasks are presented: early late gate model development, unlock probability development, system error model development, probability of acquisition and model development, and math model validation testing.
Ellis, M. R.↗
Development of spectral analysis math models and software program and spectral analyzer, digital converter interface equipment design
Spectral analyses of angle-modulated communication systems is studied by: (1) performing a literature survey of candidate power spectrum computational techniques, determining the computational requirements, and formulating a mathematical model satisfying these requirements; (2) implementing the model on UNIVAC 1230 digital computer as the Spectral Analysis Program (SAP); and (3) developing the hardware specifications for a data acquisition system which will acquire an input modulating signal for SAP. The SAP computational technique uses extended fast Fourier transform and represents a generalized approach for simple and complex modulating signals.
Hayden, W. L.↗