Method and Apparatus for Monitoring Solenoid Health

• US 20100217545A1
• Filed: 02/20/2009
• Published: 08/26/2010
• Est. Priority Date: 02/20/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Salman, Mutasim A., Rajagopalan, Satish
• Granted Patent: US 8,055,460 B2
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/72 Testing of electric windings testing of transformers G01R31/62

Abstract

A method for monitoring the state of health (SOH) of a solenoid powered by a battery includes measuring a voltage and a current supplied to the solenoid by the battery, using a processor to determine each of an equivalent resistance and inductance of the solenoid using the voltage and the current, comparing the equivalent resistance and the equivalent inductance to a corresponding calibrated threshold, and recording deviations from the corresponding calibrated thresholds as a pair of SOH values. A trend of the SOH values is continuously monitored, and an appropriate control action is taken when either SOH value drops below a calibrated lower limit. A solenoid monitoring system includes a solenoid, voltage and current sensors, and a controller having an algorithm for continuously monitoring a state of health (SOH) of the solenoid as set forth above.

Claims

1. A method for monitoring the state of health (SOH) of a solenoid powered by a battery, the method comprising:

measuring a voltage and a current supplied to the solenoid by the battery;

using a processor to determine each of an equivalent resistance and an equivalent inductance of the solenoid using the voltage and the current;

comparing each of the equivalent resistance and the equivalent inductance to a corresponding calibrated threshold;

recording deviations from the corresponding calibrated thresholds on a computer-readable medium as a pair of SOH values;

continuously monitoring a trend of each of the pair of SOH values; and

automatically executing a control action when either of the pair of SOH values drops below a calibrated lower limit.

2. The method of claim 1, wherein automatically executing a control action includes one of:

recording a diagnostic code on the computer-readable medium, activating an audio/visual signal, and displaying a message on a display device.

3. The method of claim 1, including an accessory powered by the battery, wherein measuring a current supplied to the solenoid by the battery includes:

measuring a total outlet current of the battery;

determining a current supplied to the accessory; and

subtracting the current supplied to the accessory from the total outlet current of the battery prior to energizing the solenoid.

4. The method of claim 1, wherein using a processor to determine the equivalent resistance and the equivalent inductance of the solenoid includes:

determining whether the solenoid is of a first or a second predetermined type;

calculating the equivalent resistance and the equivalent inductance as a function of a peak current and exponential time constant when the solenoid is of the first type; and

estimating the equivalent resistance and the equivalent inductance using predetermined parameter estimation technique when the solenoid is of the second type.

5. The method of claim 1, further comprising estimating a back-electro-motive force (EMF) of the solenoid using a predetermined parameter estimation technique, and automatically executing a second control action when the back-EMF exceeds a calibrated threshold.

6. A method for monitoring the state of health (SOH) of a solenoid powered by a battery, the method comprising:

measuring each of a voltage and a peak current supplied to the solenoid by the battery, wherein the peak current defines a maximum value of an exponential rise in current delivered to the solenoid from the battery;

using a processor to calculate each of an equivalent resistance and an equivalent inductance of the solenoid as a function of the peak current and an exponential time constant;

subtracting each of the equivalent resistance and the equivalent inductance from a corresponding calibrated threshold to thereby determine a deviation from the corresponding calibrated threshold;

subtracting the deviation from a value of 1 to thereby determine a state of health (SOH) factor for each of the equivalent resistance and the equivalent inductance;

monitoring a trend of the SOH for each of the equivalent resistance and the equivalent inductance; and

automatically executing a control action when the SOH factor of at least one of the equivalent resistance and the equivalent inductance drops below a calibrated lower limit.

7. The method claim 6, further comprising:

comparing the SOH factors for the equivalent resistance and the equivalent inductance;

selecting the minimum SOH factor of the compared SOH factors;

comparing the minimum SOH factor to a calibrated minimum threshold; and

automatically executing the control action when the minimum SOH factor drops below the calibrated minimum threshold.

8. The method of claim 7, the solenoid including a moveable plunger portion, wherein automatically executing the control action includes:

recording a predetermined diagnostic code when the minimum SOH factor does not exceed the calibrated minimum threshold;

estimating a back-EMF of the solenoid when the minimum exceeds the minimum threshold;

comparing the back-EMF to a calibrated maximum back-EMF threshold; and

setting a diagnostic code indicating a malfunction of the moveable plunger portion when the back-EMF exceeds the maximum back-EMF threshold.

9. The method of claim 8, wherein estimating the back-EMF includes using a predetermined parameter estimation technique.

10. The method of claim 9, wherein the predetermined parameter estimation technique is selected from the group consisting of:

linear least squares, polynomial least squares, and recursive least squares.

11. A solenoid monitoring system comprising:

an electro-mechanical solenoid;

a current sensor adapted for measuring an electrical current supplied to the solenoid;

a voltage sensor adapted for measuring a voltage level supplied to the solenoid; and

a controller in communication with the current sensor and the voltage sensor, and having an algorithm for continuously monitoring a state of health (SOH) of the solenoid;

wherein the algorithm is adapted for determining each of an equivalent resistance and an equivalent inductance of the solenoid, for calculating a first SOH factor as a function of the equivalent resistance and a second SOH factor as a function of the equivalent resistance, and for executing a control action when the value of one of the first and the second SOH factor falls below a minimum threshold.

12. The system of claim 11, wherein the solenoid has a moveable plunger portion that generates a back-electro-motive force (EMF) when moving, and wherein the algorithm is adapted for estimating the back-EMF using a parameter estimation technique.

13. The system of claim 12, wherein the algorithm is adapted for executing a control action when the value of the back-EMF exceeds a calibrated maximum.

14. The system of claim 12, wherein the solenoid is electrically connected to a vehicular starter motor, and is configured as an electromagnetic switch for selectively activating the vehicular starter motor.

15. The system of claim 12, wherein the control action includes at least one of:

recording a diagnostic code on the computer-readable medium, activating an audio/visual signal, and displaying a message on a display device.