Kaplan, Sargent and Goodman 
Suso = vertical distance from height sensor to 
undisturbed water surface at design 
foilborne condition, 
s = Laplace transform operator, 
C. = unknown parameters. 
1 
To demonstrate the feasibility of using system identification 
to estimate the C's from full-scale tests, computer generated trajec- 
tories were first used as trial inputs. The sponsoring agency supplied 
the computer generated trajectories but withheld the values of the C's 
used in the generation until the results of system identification became 
known. Three sets of trajectories for each of the three different con- 
figurations, termed A, B, and C (i.e., for three different sets of 
C's) were supplied. A run in each case consisted of a step change in 
the commanded height after the craft had reached equilibrium. Alto- 
gether, there were 9 sets of trajectories supplied. 
Even though there was no prior information given as to the 
proper values for the C's other than the crudest order of magnitude 
estimates, no difficulty was encountered by the system identification 
program in converging toa set of C's for each configuration and run. 
Confidence in the converged results was investigated by varying the 
record length as described previously, and also by comparing the 
results from different runs of the same configuration. In all cases 
high confidence in the results were indicated. The estimates from 
system identification are given in Table 2, together with the true va- 
lues. 
Table © 2 
Configuration 
True (Estimated) 
A B C 
C, .0450(. 0439) .0450(.0439) .0950(. 0942) 
Cc, 14842 (.434) Sheds 129) 161 129) 
C, .1794(. 179) . 1794(. 179) . 1906(. 190) 
1644 
