Method of operating or constructing a geartooth sensor

• US 6,191,576 B1
• Filed: 06/30/1998
• Issued: 02/20/2001
• Est. Priority Date: 06/30/1998
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Ricks, Lamar F., Lamb, Wayne A., Hancock, Peter G.
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US09/107,798
• Time in Patent Office: 966 Days
• Field of Search: 324/166, 324/173, 324/174, 324/207.12, 324/207.2, 324/207.21, 324/207.25, 324/251, 327/58, 327/60, 327/62, 327/72, 327/510-511, 327/516-517, 123/612, 123/617
• US Class Current: 324/207.2
• CPC Class Codes: G01D 3/02 with provision for altering or correcting the law of variation
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence
• CPC Class Codes: G01D 5/2448 Correction of gain, threshold, offset or phase control

Abstract

A geartooth sensor utilizes an algorithm for establishing an adaptive threshold for the switch point of the sensor to minimize drift in the point at which the sensor output changes in relation to the target features it is tracking. The algorithm utilizes measured waveform peak and average outputs and applies a separate empirically derived constant to each value to quickly obtain the major portion of the adaptive threshold value from the product of the first constant and the peak output, and to refine the threshold value further with the product of the second constant and the average output.

Claims

1. A method of operating a geartooth sensor comprising the steps of:

(a) obtaining at least one amplified sensor transducer waveform;

(b) periodically measuring the peak output (B_peak) from the sensor transducer waveform and multiplying the peak output by a first constant (M₁) resulting in a first product;

(c) obtaining an average output of the sensor transducer waveform (B_avg) and multiplying the average output by a second constant (M₂) resulting in a second product;

(d) adding the first and second products to obtain an adaptive threshold;

(e) comparing the adaptive threshold to the sensor transducer waveform to result in an output; and

(f) utilizing the output as a switch point to set the operational characteristics of the geartooth sensor.

2. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

obtaining the average output by a running calculation of output values.

3. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

obtaining the average output by deriving it with a time based integrator.

4. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

utilizing the first constant to achieve the least drift from the true point over a range of airgap tolerances.

5. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

determining the second constant for multiplication with the average output value which achieves least drift from a true point over a range of airgap tolerances when added to M₁ times B_peak.

6. A method of operating a geartooth sensor according to claim 1 wherein both constants are less than 1.0.

7. A method of operating a geartooth sensor according to claim 1 wherein M₁ is greater than M₂.

8. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

determining B_peak and B_avg by a digital processor.

9. A method of operating a geartooth sensor according to claim 1 further comprising the step of:

determining B_peak and B_avg by means of analog circuitry.

10. A method for constructing a sensing system for a rotating target comprising the steps of:

(a) graphically plotting a plurality of output waveforms from a magnetic sensor transducer over a range of airgaps within an expected operating range of airgaps between the target and the sensing system;

(b) deriving a constant M₁;

(c) deriving a constant, M₂; and

;

(d) acquiring B_peak and B_avg during operation of the sensor, B_peak corresponding to the peak Gaussian output waveform and B_avg corresponding to the average gaussian output waveform and multiplying B_peak and B_avg times M₁ and M₂, respectively, resulting in a first product and a second product, and adding the first and second products thereof resulting in an adaptive threshold switch point which represents an amount of least drift of the sensor switch point from at least one reference point on the target to set the operational characteristics of the sensor.

11. A method of operating a geartooth sensor comprising the steps of:

(a) periodically obtaining a peak output (B_peak) of a sensor transducer and applying a first constant (M₁) to the peak output to derive a first value (B_max);

(b) obtaining an average output of the sensor transducer (B_avg) and applying a second constant (M₂) to the average to obtain a second value (B_min);

(c) combining the first and second values, B_max and B_min, to obtain an adaptive threshold; and

(d) applying the adaptive threshold as a switch point to set the operational characteristics of the sensor transducer.

12. A geartooth sensor comprising:

(a) means for periodically obtaining the peak output (B_peak) of the sensor transducer and applying a first constant (M₁) to B_peak to obtain a first value (B_max);

(b) means for obtaining the average output of the sensor transducer (B_avg) and applying a second constant (M₂) to B_avg to obtain a second value (B_min);

(c) means for combining B_max and B_min to obtain an adaptive threshold; and

(d) means for applying the adaptive threshold as a switch point to set the operational characteristics of the sensor transducer.

13. The geartooth sensor according to claim 12 wherein both constants are less than 1.0.

14. The geartooth sensor according to claim 12 wherein M₁ is greater than M₂.

15. A method of operating a geartooth sensor according to claim 12 further comprising the step of:

digital processing means for obtaining the values M₁×

B_peak and M₂×

B_avg.

16. A method of operating a geartooth sensor according to claim 12 further comprising:

analog processing means for obtaining the values M₁×

B_peak and M₂×

B_avg.