Method for compensating a measured value offset
In a method for determining an offset of measured values of a multiaxial directional sensor using a superposed signal, a large number of multiaxial measured values are recorded first. Measured values, which are recorded in different orientations of the directional sensor, form a geometric figure in a coordinate system resulting from the measuring axes of the sensor, the ideal form of the geometric figure being known and the ideal center point of which being located at the origin of the measuring axes. In the case of a biaxial sensor, the geometric figure is a circle; in the case of a triaxial sensor, it is a sphere around the origin. The superposition caused by the interference is reflected in that the center point of the geometric figure is shifted in relation to the origin of the measuring axes. The offset is measured by determining this shift.
1. A method for determining an offset of measured values of a multiaxial directional sensor using a superposed signal, comprising:
recording, by a processor, a large number of multiaxial measured values;
determining, by the processor, a geometric figure as an approximation of the large number of multiaxial measured values;
determining, b the processor, the offset of the measured values based on an offset of the figure in relation to an interference-free position of the figure;
assigning, by the processor, a recorded measured value to one of a plurality of predetermined clusters; and
discarding, by the processor, the measured value if a predetermined number of measured values has already been assigned to the cluster to which the measured value is assigned.
2. The method as recited in claim 1 , wherein the determination of the offset is not made until the predetermined number of measured values has been assigned to each of a predetermined number of clusters.
3. The method as recited in claim 1 , wherein the clusters are uniformly distributed along measuring axes.
4. The method as recited in claim 1 , wherein the number of clusters is a power of two and the assignment includes a division of the multiaxial measured value by a power of two.
5. The method as recited in claim 1 , further comprising:
storing the measured value assigned to a cluster in a memory.
6. The method as recited in claim 5 , wherein additional measured values are recorded after the determination of the offset and assigned to the clusters and the offset is updated.
7. The method as recited in claim 6 , further comprising:
after the determination of the offset, determining, by the processor, an expansion of the figure; and
adjusting, by the processor, at least one of a number of clusters on one of the measuring axes, a number of predetermined measured values per cluster, and a predetermined number of clusters having assigned measured values as a function of the expansion.
8. The method as recited in claim 1 , wherein the directional sensor is a magnetic field sensor, the number of measuring axes is three and the figure is a sphere.
9. The method as recited in claim 1 , wherein the figure is determined using least squares method.
10. A non-transitory computer readable medium containing computer instructions stored therein for causing a processing unit to perform the steps of:
recording a large number of multiaxial measured values;
determining a geometric figure as an approximation of the large number of multiaxial measured values;
determining the offset of the measured values based on an offset of the figure in relation to an interference-free position of the figure;
assigning a recorded measured value to one of a plurality of predetermined clusters; and
discarding the measured value if a predetermined number of measured values has already been assigned to the cluster to which the measured value is assigned.