Method for a phase angle correction during scanning of a code track

• US 20040015307A1
• Filed: 06/06/2003
• Published: 01/22/2004
• Est. Priority Date: 08/22/2000
• Status: Abandoned Application

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Heisenberg, David
• Application Number:
  US10/362,116
• Publication Number:
  US 20040015307A1
• Time in Patent Office: Days
• US Class Current: 702/72
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01D 5/2452 incorporating two or more tracks having an (n, n+1, ...) relationship
• CPC Class Codes: G01L 3/101 involving magnetic or electromagnetic means
• CPC Class Codes: G01L 3/104 involving permanent magnets
• CPC Class Codes: G01L 3/109 involving measuring phase difference of two signals or pulse trains
• CPC Class Codes: G01L 5/221 to steering wheels, e.g. for power assisted steering

Abstract

According to the invention, a method for correcting a phase angle when scanning a code track with sensor elements is proposed that delivers a sinusoidal and a cosinusoidal signal, with which the phase difference between two signals is corrected using a specified algorithm. Since the sensor elements used, e.g., GMR, AMR, or Hall sensor elements, deliver phase-displaced sinusoidal and cosinusoidal signals due to the arrangement of the code tracks, their phases must be corrected before the arctan of the quotient can be calculated. This takes place using an algorithm derived from an arc tangent function. The method according to the invention is used preferably to measure the rotational angle or torque of a steering shaft of a motor vehicle.

Claims

1. A method for correcting a phase angle when scanning a code track (6a, 6b), whereby sensor elements (5) deliver sinusoidal and cosinusoidal signals with a relative phase-angle error (y),

wherein the correction of the phase-angle error (y) is carried out using a specified algorithm, whereby the specified algorithm contains an arctan function.

2. The method according to claim 1,

wherein the correction of the phase angle (φ

) is carried out according to the following equation;

$\mathrm{\varphi <br><br>}=1/n<br><br>\text{\hspace{1em}<br><br>}·<br><br>\arctan <br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\frac{U_1-\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}·<br><br>U_2}{U_2·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}}\right),$

whereby y is the phase error, U₁, U₂ are the sinusoidal and cosinusoidal voltages of the sensor element (5), and n is the number of periods.

3. The method according to claim 1 or 2,

wherein the algorithm comprises an expanded arctan2 function for an angular range up to 360°

, whereby the phase angle (φ

) is calculated according to the following formula;

$\mathrm{\varphi <br><br>}=1/n<br><br>\text{\hspace{1em}<br><br>}·<br><br>\arctan <br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\frac{U_1-\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}·<br><br>U_2}{U_2·<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}}\right).$

4. The method according to claims 1 through 3,

wherein the phase correction takes place when a rotational angle of a shaft (3) is determined.

5. The method according to one of the preceding claims,

wherein, in combination with a torsional element (9), a torsional angle at the shaft (3) is determined.

6. The method according to one of the preceding claims,

wherein the code track (6a, 6b) comprises alternately situated north and south poles, and

the sensor elements (5) are designed as GMR, AMR, or Hall elements and scan the magnetic north and south poles.

7. The method according to one of the preceding claims,

wherein, in the case of optical encodings (2) of the code track (6a, 6b), the sensor elements (5) contain photosensitive sensors.

8. The method according to one of the preceding claims,

wherein the angular determination is carried out at a steering shaft (3) of a motor vehicle.