Sensing Ignition By Voltage Monitoring

• US 20120067113A1
• Filed: 09/21/2010
• Published: 03/22/2012
• Est. Priority Date: 09/21/2010
• Status: Active Grant

• Current Assignee: GeoTab Incorporated
• Original Assignee: Webtech Wireless Incorporated (GeoTab Incorporated)
• Inventors: Jaffe, Norman, Crisologo, Jose
• Granted Patent: US 8,393,201 B2
• Time in Patent Office: Days
• US Class Current: 73/114.62
• CPC Class Codes: G01M 15/02 Details or accessories of testing apparatus
• CPC Class Codes: G01M 15/042 by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12

Abstract

A method of sensing vehicle engine ignition status is disclosed wherein samples of only the electrical system voltage levels are used. Sampling voltages that drop sufficiently (in magnitude and quantity over a period of time) will signify an “engine off” state.

Claims

1. A method of sensing the ignition state of a vehicle engine, comprising the steps of:

a) sampling the voltage level of the vehicle electrical system as powered by the vehicle battery without relying on other physical phenomena related to the engine, to obtain a current voltage sample;

b) determining if said current voltage sample has a sufficient drop from the preceding voltage sample;

c) determining if said current voltage sample is reliable; and

d) determining if said current voltage sample is below a specified threshold from which an accurate inference is that the vehicle engine ignition is off.

2. The method of claim 1, wherein step c) determines reliability by determining if the trend of the voltage samples preceding said current voltage sample is consistent with the said current voltage sample.

3. The method of claim 1, further comprising the step of calculating the Running Average Voltage, and wherein step b) determines the sufficiency of the drop from the preceding voltage sample, by measuring whether it exceeds a prescribed delta (the “

Drop Delta”

) below said Running Average Voltage.

4. The method of claim 3, wherein step b) determines the sufficiency of the drop by further measuring whether there is a prescribed number of consecutive voltage samples each exceeding said Drop Delta (“

Transition Count Off”

).

5. The method of claim 4, further comprising the step of determining whether the Running Average Voltage is below a prescribed voltage (the “

Off Threshold Voltage), and if it is, recognizing the Ignition Off state.

6. The method of claim 3, wherein if it is determined that said current voltage sample is not reliable, further comprising the step of substituting said Running Average Voltage with the value of the preceding Running Average Voltage.

7. The method of claim 3, wherein said Drop Delta is a function of local conditions being a weighted sum of {vehicle battery age, engine-on time, ambient temperature, current voltage sample, engine temperature, current Drop Delta}, where the respective synaptic weights are learned via a standard neural network learning algorithm.

8. The method of claim 3, wherein said Drop Delta is a fuzzy logic function based on local conditions of {vehicle battery age, engine-on time, ambient temperature, current voltage sample, engine temperature, current Drop Delta}.

9. The method of claim 1, further comprising the steps of assigning default values to the parameters Sample Interval, Sample Count, Transition Count On, Transition Count Off, On Threshold Voltage, Drop Delta and Off Threshold Voltage, and then tuning them using guidelines and heuristics.

10. The method of claim 1, where the parameter of Transition Count Off is assigned a value that differs from the value of Transition Count on.

11. The method of claim 4, wherein the parameter of Transition Count Off is changed in response to the recent trend of voltage samples.

12. A system that senses the ignition state of a vehicle engine, comprising:

a) a sampler that samples the voltage level of the vehicle electrical system to obtain a plurality of voltage samples including a current voltage sample,

b) a logic component that determines if said current voltage sample has a sufficient drop from the preceding voltage samples;

c) a logic component that determines if said current voltage sample is reliable; and

d) a logic component that determines if said current voltage sample is below a specified threshold from which an accurate inference is that the vehicle engine ignition is off.