The Derivation and Definition of a Linear Model program, LINEAR, provides the user with a powerful and flexible tool for the linearization of aircraft aerodynamic models. LINEAR was developed to provide a standard, documented, and verified tool to derive linear models for aircraft stability analysis and control law design. Linear system models define the aircraft system in the neighborhood of an analysis point and are determined by the linearization of the nonlinear equations defining vehicle dynamics and sensors. LINEAR numerically determines a linear system model using nonlinear equations of motion and a user supplied linear or nonlinear aerodynamic model. The nonlinear equations of motion used are six-degree-of-freedom equations with stationary atmosphere and flat, nonrotating earth assumptions. LINEAR is capable of extracting both linearized engine effects, such as net thrust, torque, and gyroscopic effects and including these effects in the linear system model. The point at which this linear model is defined is determined either by completely specifying the state and control variables, or by specifying an analysis point on a trajectory and directing the program to determine the control variables and the remaining state variables. The system model determined by LINEAR consists of matrices for both the state and observation equations. The program has been designed to provide easy selection of state, control, and observation variables to be used in a particular model. Thus, the order of the system model is completely under user control. Further, the program provides the flexibility of allowing alternate formulations of both the state and observation equations. Data describing the aircraft and the test case is input to the program through a terminal or formatted data files. All data can be modified interactively from case to case. The aerodynamic model can be defined in two ways: a set of nondimensional stability and control derivatives for the flight point of interest, or a full non-linear aerodynamic model as used in simulations. LINEAR is written in FORTRAN and has been implemented on a DEC VAX computer operating under VMS with a virtual memory requirement of approximately 296K of 8 bit bytes. Both an interactive and batch version are included. LINEAR was developed in 1988.
[1]
J. E. Dieudonne.
Description of a computer program and numerical techniques for developing linear perturbation models from nonlinear systems simulations
,
1978
.
[2]
Duane T. McRuer,et al.
Aircraft Dynamics and Automatic Control
,
1973
.
[3]
T. G. Gainer,et al.
Summary of transformation equations and equations of motion used in free flight and wind tunnel data reduction and analysis
,
1972
.
[4]
J. A. Thelander.
AIRCRAFT MOTION ANALYSIS
,
1965
.
[5]
R. E. Maine,et al.
Programmer's manual for MMLE3, a general FORTRAN program for maximum likelihood parameter estimation
,
1980
.
[6]
W. Gracey.
Measurement of aircraft speed and altitude
,
1981
.
[7]
J. W. Edwards,et al.
A FORTRAN program for the analysis of linear continuous and sample-data systems
,
1976
.
[8]
R. E. Maine,et al.
Application of parameter estimation to aircraft stability and control: The output-error approach
,
1986
.
[9]
Eugene L. Duke,et al.
User's manual for LINEAR, a FORTRAN program to derive linear aircraft models
,
1987
.