Method and device for determining a recognition threshold

• US 9,500,465 B2
• Filed: 10/31/2011
• Issued: 11/22/2016
• Est. Priority Date: 12/27/2010
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Rolew, Eduard, Schmidt, Verena, Opitz, Bernhard
• Primary Examiner(s): Bhat, Aditya
• Application Number:
  US13/976,566
• Publication Number:
  US 20140019084A1
• Time in Patent Office: 1,849 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A method for determining a recognition threshold for recognizing the presence of a tooth or a tooth gap of a position sensor in front of a sensor is presented. The method includes a step of reading in a sensor signal which represents a variation over time of a measured magnetic field when the teeth and the tooth gaps of the position sensor are passed by the sensor. In addition, the method includes a step of ascertaining from the sensor signal a first value based on a minimum value of the sensor signal and a first value based on a maximum value of the sensor signal within a predefined time interval. The method also includes a step of computing a differential absolute value which represents a predetermined percentage of a difference between the value based on the at least one maximum value and a value based on the at least one minimum value of the sensor signal. Lastly, the method includes a step of determining the recognition threshold, so that the recognition threshold represents a value that corresponds to a result of adding the differential absolute value to the first value based on the minimum value of the sensor signal.

Claims

1. A method for determining a first and a second recognition threshold for recognizing a presence of teeth or tooth gaps of a position sensor in front of a sensor, the method comprising:

reading in a sensor signal which represents a variation over time of a measured magnetic field when the teeth and the tooth gaps of the position sensor are passed by the sensor;

ascertaining from the sensor signal a first value based on a minimum value of the sensor signal and a first value based on a maximum value of the sensor signal within a predefined time interval;

computing a first differential absolute value which represents a predetermined percentage of a difference between the first value based on the maximum value of the sensor signal and the first value based on the minimum value of the sensor signal;

determining a first recognition threshold, so that the first recognition threshold represents a value that corresponds to a result of adding the first differential absolute value to the first value based on the minimum value of the sensor signal;

ascertaining from the sensor signal a second value based on a minimum value of the sensor signal and a second value based on a maximum value of the sensor signal within a second predefined time interval subsequent to the predefined time interval;

computing a second differential absolute value which represents a second predetermined percentage of a difference between the second value based on the maximum value and the second value based on the minimum value of the sensor signal; and

determining a second recognition threshold, which is different from the first recognition threshold, so that the second recognition threshold represents a value that corresponds to a result of adding the second differential absolute value to the second value based on the minimum value of the sensor signal,

wherein the method provides for precise determination of a position of the teeth or the gaps of the position sensor.

2. The method as recited in claim 1, wherein in the computing of the second differential absolute value, a value is used which corresponds to the predetermined percentage that is used in the step of computing the first differential absolute value.

3. The method as recited in claim 1, wherein in ascertaining of the first value step, at least one of the first value based on the minimum value of the sensor signal, and the first value based on the maximum value of the sensor signal, is discarded if a difference between the first value based on the minimum value and the first value based on the maximum value is less than a predetermined differential threshold value.

4. The method as recited in claim 1, wherein in ascertaining of the second value step, at least one of the second value based on the minimum value of the sensor signal, and the second value based on the maximum value of the sensor signal, is discarded if a difference between the second value based on the minimum value and the second value based on the maximum value is less than a predetermined differential threshold value.

5. The method as recited in claim 1, wherein a position sensor having a number of n teeth in combination with the sensor is used, and wherein in the reading-in, a sensor signal having a plurality of groups of small values and a plurality of groups of large values is read in, and in the ascertaining the first value, the first value based on a minimum value of the sensor signal is obtained by averaging minimum values of each nth group of small values, and the first value based on a maximum value of the sensor signal is obtained by averaging the maximum values of each nth group of large values.

6. The method as recited in claim 1, wherein after the determining, detecting a tooth of the position sensor when the sensor signal has a value that is greater than the one of the first recognition threshold or the second recognition threshold.

7. A device for determining a recognition threshold for recognizing a presence of a tooth or a tooth gap of a position sensor in front of a sensor, the device comprising:

an interface to read in a sensor signal which represents a variation over time of a measured magnetic field when the teeth and the tooth gaps of the position sensor are passed by the sensor;

a unit to ascertain from the sensor signal a first value based on a minimum value of the sensor signal and a first value based on a maximum value of the sensor signal within a predefined time interval, and to ascertain from the sensor signal a second value based on a minimum value of the sensor signal and a second value based on a maximum value of the sensor signal within a second predefined time interval subsequent to the predefined time interval;

a unit to compute a first differential absolute value which represents a predetermined percentage of a difference between the first value based on the maximum value and the first value based on the minimum value of the sensor signal, and to compute a second differential absolute value which represents a second predetermined percentage of a difference between the second value based on the maximum value and the second value based on the minimum value of the sensor signal; and

a unit to determine the recognition threshold, so that the recognition threshold represents a value that corresponds to a result of adding the first differential absolute value to the first value based on the minimum value of the sensor signal, and to determine a second recognition threshold, which is different from the first recognition threshold, so that the second recognition threshold represents a value that corresponds to a result of adding the second differential absolute value to the second value based on the minimum value of the sensor signal,

wherein the device is configured to provide for precise determination of a position of the teeth or the tooth gaps of the position sensor.

8. A non-transitory computer-readable storage medium storing program code to determine a first and a second recognition threshold for recognizing a present of teeth or tooth gaps of a position sensor in front of a sensor, the program code, when executed by a device, causing the device to perform:

reading in a sensor signal which represents a variation over time of a measured magnetic field when the teeth and the tooth gaps of the position sensor are passed by the sensor;

ascertaining from the sensor signal a first value based on a minimum value of the sensor signal and a first value based on a maximum value of the sensor signal within a predefined time interval;

computing a first differential absolute value which represents a predetermined percentage of a difference between the first value based on the maximum value of the sensor signal and the first value based on the at least one minimum value of the sensor signal;

determining a first recognition threshold, so that the first recognition threshold represents a value that corresponds to a result of adding the first differential absolute value to the first value based on the minimum value of the sensor signal;

ascertaining from the sensor signal a second value based on a minimum value of the sensor signal and a second value based on a maximum value of the sensor signal within a second predefined time interval subsequent to the predefined time interval;

computing a second differential absolute value which represents a second predetermined percentage of a difference between the second value based on the maximum value and the second value based on the minimum value of the sensor signal; and

determining a second recognition threshold, which is different from the first recognition threshold, so that the second recognition threshold represents a value that corresponds to a result of adding the second differential absolute value to the second value based on the minimum value of the sensor signal.

wherein the method provides for precise determination of a position of the teeth or the tooth gaps of the position sensor.