Method of detecting system function by measuring frequency response
First Claim
1. A method for detecting function of an energy storage device under test by measuring frequency response, the method comprising the acts of:
- generating a vector of frequencies by defining a lowest frequency for the vector of frequencies, defining an integer step factor, multiplying the lowest frequency by the integer step factor to obtain a second frequency for the vector of frequencies, determining subsequent frequencies for the vector of frequencies by multiplying a previous frequency in the vector of frequencies by the integer step factor;
defining a vector of amplitudes and phases corresponding to the frequencies in the vector of frequencies;
assembling an excitation signal using the vector of frequencies and the vector of amplitudes and phases;
conditioning the excitation signal to be compatible with the energy storage device under test;
exciting the energy storage device under test with the conditioned excitation signal for one period of the lowest frequency;
capturing a response time record with a data acquisition system, the response time record comprising a response of the energy storage device to the act of exciting; and
processing the response time record to the frequency domain to obtain the frequency response.
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Abstract
Methods of rapidly measuring an impedance spectrum of an energy storage device in-situ over a limited number of logarithmically distributed frequencies are described. An energy storage device is excited with a known input signal, and a response is measured to ascertain the impedance spectrum. An excitation signal is a limited time duration sum-of-sines consisting of a select number of frequencies. In one embodiment, magnitude and phase of each frequency of interest within the sum-of-sines is identified when the selected frequencies and sample rate are logarithmic integer steps greater than two. This technique requires a measurement with a duration of one period of the lowest frequency. In another embodiment, where selected frequencies are distributed in octave steps, the impedance spectrum can be determined using a captured time record that is reduced to a half-period of the lowest frequency.
43 Citations
22 Claims
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1. A method for detecting function of an energy storage device under test by measuring frequency response, the method comprising the acts of:
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generating a vector of frequencies by defining a lowest frequency for the vector of frequencies, defining an integer step factor, multiplying the lowest frequency by the integer step factor to obtain a second frequency for the vector of frequencies, determining subsequent frequencies for the vector of frequencies by multiplying a previous frequency in the vector of frequencies by the integer step factor; defining a vector of amplitudes and phases corresponding to the frequencies in the vector of frequencies; assembling an excitation signal using the vector of frequencies and the vector of amplitudes and phases; conditioning the excitation signal to be compatible with the energy storage device under test; exciting the energy storage device under test with the conditioned excitation signal for one period of the lowest frequency; capturing a response time record with a data acquisition system, the response time record comprising a response of the energy storage device to the act of exciting; and processing the response time record to the frequency domain to obtain the frequency response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for detecting function of an energy storage device under test by measuring frequency response, the method comprising the acts of:
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generating a vector of frequencies by defining a lowest frequency for the vector of frequencies, defining an integer step factor, multiplying the lowest frequency by the integer step factor to obtain a second frequency for the vector of frequencies, determining subsequent frequencies for the vector of frequencies by multiplying a previous frequency in the vector of frequencies by the integer step factor, and removing the second frequency from the vector of frequencies; defining a vector of amplitudes and phases corresponding to the frequencies in the vector of frequencies; assembling an excitation signal using the vector of frequencies and the vector of amplitudes and phases; conditioning the excitation signal to be compatible with the energy storage device under test; exciting the energy storage device under test with the conditioned excitation signal for one-half period of the lowest frequency; capturing a response time record with a data acquisition system, the response time record comprising a response of the energy storage device to the act of exciting; and processing the response time record to the frequency domain to obtain the frequency response. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification