METHOD FOR DYNAMIC ERROR COMPENSATION OF A POSITION SENSOR AND POSITION SENSOR WITH DYNAMIC ERROR COMPENSATION

Abstract

A method for dynamic error compensation of a position sensor and a position sensor are disclosed. In the method, a calculated speed of a moving target for a current determined position is compared to a calculated running average of the speed of the moving target over a certain number of determined positions and if the calculated speed of the moving target for the current position is within a first window around the calculated running average of the speed of the moving target over the certain number of determined positions the dynamic angle error is not re-calculated for the current determined position, and/or if the calculated speed of the moving target for the current determined position exceeds a second window the previously calculated running average is deleted and the calculation of the running average of the speed of the moving target over a certain number of determined positions is restarted.

Claims

1. A method for dynamic error compensation of a position sensor, comprising: determining a position of a moving target by the position sensor with a certain sampling frequency, calculating the speed of the moving target for each determined position, calculating a running average of the speed of the moving target over a certain number of determined positions, and calculating a dynamic angle error on basis of the calculated running average of the speed, wherein the calculated dynamic angle error is used to correct the output of the position sensor, the calculated speed of the moving target for the current determined position is compared to the calculated running average of the speed of the moving target over the certain number of determined positions and if the calculated speed of the moving target for the current position is within a first window around the calculated running average of the speed of the moving target over the certain number of determined positions the dynamic angle error is not re-calculated for the current determined position, and/or if the calculated speed of the moving target for the current determined position exceeds a second window the previously calculated running average is deleted and the calculation of the running average of the speed of the moving target over a certain number of determined positions is restarted.

2. The method according to claim 1, wherein the determining the position of the moving target by the position sensor comprises the sensing and calculating the position of the moving target.

3. The method according to claim 1, wherein the dynamic angle error of the position sensor relates to the time for sensing and calculating the current position of the moving target.

4. The method according to claim 1, wherein the position sensor is a rotational position sensor and the method compensates the dynamic angle error of the rotational position sensor.

5. The method according to claim 1, wherein the first window is smaller than the second window.

6. The method according to claim 5, wherein the dynamic angle error is calculated on basis of the of the calculated running average if the calculated speed of the moving target for the current determined position is greater than the first window and smaller than the second window.

7. The method according to claim 1, wherein the first window is smaller than a first ratio of the calculated running average of the speed of the moving target over the certain number of determined positions.

8. The method according to claim 1, wherein the second window is greater than a second ratio of the calculated running average of the speed of the moving target over the certain number of determined positions.

9. The method according to claim 1, wherein the speed of the moving target for each determined position is calculated on basis of the current and previous determined position of the moving target by the position sensor.

10. A position sensor comprising: a sensing circuit and a control circuit, wherein the control circuit implements the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] An embodiment will be further explained with reference to the FIGURE. The FIGURE shows a schematic view of a rotational position sensor implementing the method according to one embodiment.

DETAILED DESCRIPTION

[0029] The FIGURE shows a schematic view of a position sensor (1) implementing the method for dynamic error compensation of the position sensor (1) according to an embodiment. The rotational positions sensor (1) may comprise a sensing circuit and a control circuit, wherein the control circuit implements the method. In a first step, a position (α) of a moving target is determined by the rotational position sensor (1) with a certain sampling frequency (n, k). The step of determining the position (α) of the moving target by the position rotational sensor (1) can comprise the step of sensing and calculating the position of the moving target. For each determined position (α.sub.(n)), the speed (V.sub.(n)) of the moving target is calculated. The speed (V.sub.(n)) of the moving target for each determined position (α.sub.(n)) is for example calculated on basis of the current (α.sub.(n)) and previous (α.sub.(n−1)) determined position of the moving target by the position sensor (1). Afterwards a running average (V) of the speed of the moving target over a certain number of determined positions (α.sub.(n)) is calculated. On basis of the calculated running average (V) a dynamic angle error (α.sub.err) is calculated, which is used to correct the output of the position sensor (1). The dynamic angle error (α.sub.err) of the position sensor (1) relates to the time (τ) for determining, such as sensing and calculating, the current position (α) of the moving target. Since the FIGURE refers to a rotational position sensor (1), the method compensates the dynamic angle error (α.sub.err) of the rotational position sensor (1).

[0030] The current speed (V.sub.(n)) of the moving target for the current determined position (α.sub.(n)) calculated from the last two consecutive samples is compared to the calculated running average (V) of the speed of the moving target over the certain number of determined positions (α) and if the calculated speed (V.sub.(n)) of the moving target for the current position (α.sub.(n)) is within a first window around the calculated running average (V) of the speed of the moving target over the certain number of determined positions (α) the last dynamic angle error (α.sub.err) is frozen and will be used instead of a re-calculated dynamic angle error (α.sub.err) for the current determined position (α.sub.(n)), and/or if the calculated speed (V.sub.(n)) of the moving target for the current determined position (α.sub.(n)) exceeds a second window the previously calculated running average (V) of the speed of the moving target over the certain number of determined positions (α) the last dynamic angle error (α.sub.err) is replaced by the re-calculated one on basis of the current calculated speed (V.sub.(n)) of the moving target and the previously calculated running average (V) of the speed of the moving target over a certain number of determined positions (α) is restarted.

[0031] If the calculated speed (V.sub.(n)) of the moving target exceeds the first window around the running average of the speed of the moving target and is within the second window the running average speed of the moving target is updated to include the current calculated speed (V.sub.(n)) and the dynamic angle error (α.sub.err) will be re-calculated on basis of the speed according to the running average (V) of the speed of the moving target.

[0032] In an embodiment, the first window is smaller than the second window and the dynamic angle error (α.sub.err) is calculated on basis of the of the calculated running average (V) if the calculated speed (V.sub.(n)) of the moving target for the current determined position (α.sub.(n)) is greater than the first window and smaller than the second.

[0033] For example, the first window corresponds to a substantially constant speed (V.sub.(n)) of the moving target and the second window corresponds to a substantial change of the speed (V.sub.(n)) of the moving target. For example, the first window is defined as 120% of the 3 sigma of the noise of the speed (V.sub.(n)) of the moving target and the second window is defined as 200% of the 3 sigma of the noise of the speed (V.sub.(n)) of the moving target.