SYSTEM AND METHOD FOR ELECTRICAL PARAMETER ESTIMATION

• US 20100145640A1
• Filed: 12/10/2008
• Published: 06/10/2010
• Est. Priority Date: 12/10/2008
• Status: Abandoned Application

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Hernandez, Norberto, Carmona, Jesus, Aguinaga, Esau
• Application Number:
  US12/331,748
• Publication Number:
  US 20100145640A1
• Time in Patent Office: Days
• US Class Current: 702/57
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 27/2611 Measuring inductance

Abstract

A method is provided for estimating an electrical parameter of a circuit-under-test (e.g., resistance, capacitance and/or inductance). The method acquires samples during a plurality of charging cycles rather than during just one, which allows an extended overall time period to acquire such samples. The first step involves defining a major sampling period having a plurality of minor sampling periods. A number of steps are performed for each minor sampling period: applying an excitation signal to the circuit-under-test to produce a respective induced, response signal and acquiring a respective sample of the induced signal at a respective predetermined deferral time. In an embodiment where the circuit-under-test includes an unknown capacitance, the excitation signal may be a unit step while an increase in the induced signal is governed by a charging time constant, which itself is indicative of the unknown capacitive. The electrical parameter may be determined based on the acquired samples, which collectively constitute a composite response. The composite response is processed, for example, by fitting it to a normalized capacitive charging curve, to ascertain an estimate of the unknown capacitive.

Claims

1. A method of estimating an electrical parameter of a circuit-under-test, comprising the steps of:

defining a major sampling period having a plurality of minor sampling periods;

for each minor sampling period

(i) resetting the circuit-under test to a known state;

(ii) applying an excitation signal to the circuit-under-test to thereby produce a respective induced, response signal;

(iii) acquiring a respective sample of the induced signal at a respective predetermined deferral time; and

determining the electrical parameter based on the samples.

2. The method of claim 1 further including the step of:

providing a first interface through which the excitation signal is applied to the circuit-under-test.

3. The method of claim 2 wherein the electrical parameter is a capacitance value (Cx), said step of providing the first interface includes the sub-step of:

selecting a charging resistance value (R) for the first interface.

4. The method of claim 3 wherein said step of providing the first interface includes the sub-step of:

arranging the first interface in series with the circuit-under-test.

5. The method of claim 1 further including the step of:

providing a second interface through which the induced signal is sampled.

6. The method of claim 5 wherein said induced signal is a voltage on a first node, said step of providing the second interface includes the sub-step of:

providing a unity gain buffer amplifier having an input thereof connected to the first electrical node and wherein said samples are obtained from an output of said amplifier, said amplifier having a desired output impedance.

7. The method of claim 6 wherein said induced signal is an analog signal, said step of acquiring said samples includes the sub-step of converting the induced signal at the respective deferral times into corresponding digital words.

8. The method of claim 1 wherein said resetting step includes the sub-step of discharging the circuit-under-test.

9. The method of claim 1 wherein each predetermined deferral time is measured from the beginning of a respective minor sampling period.

10. The method of claim 1 wherein said samples are concatenated to form a composite response to the excitation signal.

11. The method of claim 10 wherein said step of determining the electrical parameter further includes the sub-step of using the composite response.

12. The method of claim 11 wherein said step of determining the electrical parameter includes the sub-step of:

determining a least squares fit of the composite response to predetermined data.