Engineering topics

Hodel, A. Scottedward

Publications and source records attributed to Hodel, A. Scottedward.

4 records

NASA NTRS2000

Robust Inversion and Data Compression in Control Allocation

We present an off-line computational method for control allocation design. The control allocation function delta = F(z)tau = delta (sub 0) (z) mapping commanded body-frame torques to actuator commands is implicitly specified by trim condition delta (sub 0) (z) and by a robust pseudo-inverse problem double vertical line I - G(z) F(z) double vertical line less than epsilon (z) where G(z) is a system Jacobian evaluated at operating point z, z circumflex is an estimate of z, and epsilon (z) less than 1 is a specified error tolerance. The allocation function F(z) = sigma (sub i) psi (z) F (sub i) is computed using a heuristic technique for selecting wavelet basis functions psi and a constrained least-squares criterion for selecting the allocation matrices F (sub i). The method is applied to entry trajectory control allocation for a reusable launch vehicle (X-33).

Hodel, A. Scottedward↗

NASA NTRS1993

Octave: A MARSYAS post-processor for computer-aideed control system design

MARSYAS is a computer-aided control system analysis package for the simulation and analysis of dynamic systems. In the summer of 1991 MARSYAS was updated to allow for the analysis of sampled-data systems in terms of frequency response, stability, etc. This update was continued during the summer of 1992 in order to extend further MARSYAS commands to the study of sampled data systems. Further work was done to examine the computation of openat transfer functions, root-locii and omega-plane frequency response plots. At the conclusion of the summer of 1992 work, it was proposed that control-system design capability be incorporated into the MARSYAS package. It was decided at that time to develop a separate 'stand-alone' computer-aided control system design (CACSD) package. This report is a brief description of such a package.

Hodel, A. Scottedward↗

NASA NTRS1992

Numerical methods for the analysis of sampled-data systems and for the computation of system zeros

MARSYAS is a computer-aided control system design package for the simulation and analysis of dynamic systems. In the summer of 1991 MARSYAS was updated to allow for the analysis of sampled-data systems in terms of frequency response, stability, etc. This update was continued during the summer of 1992 in order to extend further MARSYAS commands to the study of sampled-data systems. Further work was done to examine the computation of OPENAT transfer functions, root-locii and w-plane frequency response plots.

Hodel, A. Scottedward↗

NASA NTRS1991

Numerical methods for the analysis of sampled-data systems and for the computation of system zeros

MARSYAS is a computer aided control system design package for the simulation and analysis of open loop and closed loop dynamic systems. Outlined here is the numerical and theoretical basis of the MARSYAS functions developed during the summer of 1991. In particular, the numerical computation of the matrix exponential e(exp A) = I + A + A(exp 2)/2! + A(exp 3)/3! + ... and the numerical computation of the finite system zeros of a dynamic system (continuous time or discrete time) are presented.

Hodel, A. Scottedward↗