| US 7,395,163 B1 | ||
| Method of detecting system function by measuring frequency response | ||
| John L. Morrison, Butte, Mont. (US); and William H. Morrison, Manchester, Conn. (US) | ||
| Assigned to Montana Tech of the University of Montana, Butte, Mont. (US) | ||
| Filed on Jul. 05, 2007, as Appl. No. 11/825,629. | ||
| Application 11/825629 is a continuation of application No. 11/313546, filed on Dec. 20, 2005, abandoned. | ||
| Claims priority of provisional application 60/724631, filed on Oct. 07, 2005. | ||
| Claims priority of provisional application 60/637969, filed on Dec. 20, 2004. | ||
| Int. Cl. G01R 23/00 (2006.01); G06F 11/00 (2006.01) | ||
| U.S. Cl. 702—75 [702/79; 702/117; 324/603] | 4 Claims |
| 1. A method for detecting system function of a unit under test by measuring frequency response, the method comprising the
steps of:
(a) selecting a number of frequencies over which the function of the unit under test will be tested;
(b) assembling an excitation time record that is the sum of the sinusoids of the frequencies and a duration of greater than
or equal to a period of the lowest selected frequency;
(c) conditioning the excitation time record to be compatible with the unit under test;
(d) exciting the unit under test with the excitation time record and simultaneously capturing a response time record with
a data acquisition system;
(e) processing the response time record using the following synchronous detection equations to obtain estimated frequency
components of magnitude and phase for one of the selected frequencies:
 Ai amplitude of the ith input sinusoid
Bi amplitude response of the ith output sinusoid
ωi radian frequency of the ith sinusoid
Δt time step of data system
φini phase of the ith input sinusoid
φouti phase response of the ith output sinusoid
N number of points of the response time record
M number different sinusoids of the excitation time record
R the number of points in the response time record that may be discarded
K is the frequency index for the system function being detected;
(f) repeating step (e) to obtain estimated frequency components for each selected frequency;
(g) assembling the estimated frequency components to get an estimated response time record;
(h) subtracting the estimated response time record from the captured response time record to get an error; and
(i) minimizing the error to achieve the frequency response.
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