METHOD FOR OFFSET CALIBRATION OF A YAW RATE SENSOR SIGNAL OF A YAW RATE SENSOR, SYSTEM AND COMPUTER PROGRAM

Abstract

A method for offset calibration of a rotation rate sensor signal of a rotation rate sensor. In a first step, an ascertainment is made that the rotation rate sensor is in an idle state. In a second step, after the first step, a filter parameter is determined as a function of the measured rotation rate sensor values, measured in the idle state, of the rotation rate sensor. In a third step, after the second step, a filtered measured rotation rate sensor value is determined with the aid of the filter parameter. An offset is determined with the aid of the filtered measured rotation rate sensor value.

Claims

1-11. (canceled)

12. A method for offset calibration of a rotation rate sensor signal of a rotation rate sensor, comprising the following steps: in a first step, ascertaining that the rotation rate sensor is in an idle state; in a second step, after the first step, determining a filter parameter as a function of measured rotation rate sensor values, measured in the idle state, of the rotation rate sensor; in a third step, after the second step, determining a filtered measured rotation rate sensor value using the filter parameter; and determining an offset using the filtered measured rotation rate sensor value.

13. The method as recited in claim 12, wherein, in the first step, the ascertainment is made, using an estimated average of measured rotation rate sensor values and/or using an estimated fluctuation value of measured rotation rate sensor values, that the rotation rate sensor is in the idle state.

14. The method as recited in claim 13, wherein the estimated fluctuation value corresponds to an estimated variance.

15. The method as recited in claim 13, wherein a result of the ascertainment in the first step is that the rotation rate sensor is in the idle state when the estimated average is less than a first threshold value and/or the estimated variance is less than a second threshold value.

16. The method as recited in claim 12, wherein the measured rotation rate sensor values measured in the idle state encompass only those measured rotation rate sensor values which have been measured since the rotation rate sensor has been in the idle state, the measured rotation rate sensor values measured in the idle state being used in the third step in the determination of the filtered measured rotation rate sensor value.

17. The method as recited in claim 12, wherein the filter parameter is determined in the second step as a function of a first intermediate parameter and of a second intermediate parameter, the first intermediate parameter being proportional to a reciprocal of a number of measured rotation rate sensor values measured in the idle state, the second intermediate parameter being a function of a fluctuation of measured rotation rate sensor values measured in the idle state.

18. The method as recited in claim 17, wherein the fluctuation is an estimated variance.

19. The method as recited in claim 17, wherein the filter parameter corresponds to a maximum of the first intermediate parameter and the second intermediate parameter.

20. The method as recited in claim 12, wherein in the third step, the filtered measured rotation rate sensor value is ascertained as a function of a previous filtered measured rotation rate sensor value and of an instantaneous measured rotation rate sensor value, using an exponential smoothing.

21. The method as recited in claim 12, wherein in a fourth step, after the third step, an output rate of filtered measured rotation rate sensor values is reduced using a decimator device so that reduced-output-rate filtered measured rotation rate sensor values are generated.

22. The method as recited in claim 21, wherein in a fifth step, after the third step and after the fourth step, the offset is determined using the filtered measured rotation rate sensor value or using the reduced-output-rate filtered measured rotation rate sensor values, and further using a smoothing filter.

23. A system for offset calibration of a rotation rate sensor signal of a rotation rate sensor, the system configured to: ascertainment that the rotation rate sensor is in an idle state; determine a filter parameter as a function of measured rotation rate sensor values of the rotation rate sensor which are measured in the idle state; determine a filtered measured rotation rate sensor value using the filter parameter; and determining an offset using the filtered measured rotation rate sensor value.

24. A non-transitory computer-readable storage medium on which is stored a computer program for offset calibration of a rotation rate sensor signal of a rotation rate sensor, the computer program, when executed by a computer, causing the computer to perform the following steps: in a first step, ascertaining that the rotation rate sensor is in an idle state; in a second step, after the first step, determining a filter parameter as a function of measured rotation rate sensor values, measured in the idle state, of the rotation rate sensor; in a third step, after the second step, determining a filtered measured rotation rate sensor value using the filter parameter; and determining an offset using the filtered measured rotation rate sensor value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a schematic block diagram of a system for offset calibration of a rotation rate sensor signal of a rotation rate sensor, according to an embodiment of the present invention.

[0032] FIG. 2 is a schematic block diagram of part of a system for offset calibration, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0033] In the various Figures, identical parts are always labeled with the same reference characters and are therefore as a rule also each mentioned or named only once.

[0034] FIG. 1 is a schematic block diagram of a system 100 for offset calibration of a rotation rate sensor signal 11 of a rotation rate sensor 1, according to an embodiment of the present invention. A rotation rate sensor 1 supplies a rotation rate sensor signal 11 that encompasses a sequence of measured rotation rate sensor values 10. That signal is made available to a monitoring device 14 or testing device 14. Monitoring device 14 identifies, on the basis of measured rotation rate sensor values 10 that have been obtained, whether rotation rate sensor 1 is in an idle state 15 or in a non-idle state 16 or movable state 16. For this, monitoring device 14 estimates an estimated average of measured rotation rate sensor values 10 and an estimated fluctuation value, in particular an estimated variance, of measured rotation rate sensor values 10, preferably with the aid of a smoothing filter. If the estimated average is less than a first threshold value, thr1, and the estimated variance is less than a second threshold value, thr2, monitoring device 14 ascertains that rotation rate sensor 1 is in the idle state. The first and/or second threshold value thr1, thr2 are definable, and can be selected in accordance with requirements. If the result of the ascertainment is that rotation rate sensor 1 is in non-idle state 16, no further calibration steps are carried out. If the result of the ascertainment is, conversely, that rotation rate sensor 1 is in idle state 15, calibration is continued, a filter parameter a being determined, with the aid of a filter parameter device 17, as a function of measured rotation rate sensor values x1 of rotation rate sensor 1 which are measured in idle state 15. Measured rotation rate sensor values x1 that are measured in idle state 15 encompass only those measured rotation rate sensor values 10 which were measured since rotation rate sensor 1 was in, or had transitioned into, idle state 15. A possible exemplifying embodiment of the determination of filter parameter a, or an embodiment of filter parameter device 17, is explained in FIG. 2. With the aid of filter parameter a that has been obtained, a filtered measured rotation rate sensor value x[n] is then determined in an adaptive filter device 18. A possible exemplifying embodiment of the determination of filtered measured rotation rate sensor value x[n], or an embodiment of filter device 18, is explained in FIG. 2. Once the filtered measured rotation rate sensor value x[n] has been determined, it is made available to a decimator device 20. With the aid of decimator device 20, an output rate, in particular a sampling rate, of the filtered measured rotation rate sensor values, x[n],x[n−1], is reduced, so that reduced-output-rate filtered measured rotation rate sensor values 21 are furnished. A smoothing of the reduced-output-rate filtered measured rotation rate sensor values 21 is then accomplished with the aid of a smoothing filter 30. The result is to determine offset 40 with which rotation rate sensor signal 11 can be corrected or calibrated. Smoothing filter 30 can encompass, for example, an exponential smoothing. Alternatively, however, other filtering techniques are also possible. Alternatively, it would also be possible to obtain offset 40 directly from the filtered measured rotation rate sensor value x[n] or to use the latter as offset 40. Direct utilization of reduced-output-rate filtered measured rotation rate sensor values 21 as offset 40 would also be alternatively possible.

[0035] FIG. 2 is a schematic block diagram of part of a system 100 for offset calibration, according to an embodiment of the present invention. It depicts in particular an embodiment of filter parameter device 17. In a first portion 17′ of filter parameter device 17, first intermediate parameter al is ascertained by way of the correlation a1=1/#Z, where #Z is the number of measured rotation rate sensor values x1 measured in idle state 15 since the first sample in idle state 15, or the number of samples used for calibration. In a second portion 17″ of filter parameter device 17, second intermediate parameter a2 is ascertained in such a way that the range from 0 to the second threshold value thr2 (i.e., in particular, the range from 0 to the maximum variance of measured rotation rate sensor values 10), is subdivided into several intervals or sub-regions. For example, an interval can be furnished for each typical noise level that occurs in various wearable calibration situations. A fixed value for second intermediate parameter a2 is assigned to each interval. Second intermediate parameter a2 thus receives the value assigned to the interval into which the ascertained (maximum) fluctuation or variance of measured rotation rate sensor values x1 measured in idle state 15 (or of the several axes of the rotation rate sensor signal) falls. Second intermediate parameter a2 is thus based on the noise power level of rotation rate sensor 1.

[0036] In a third portion 17′″ of filter parameter device 17, filter parameter a is then ascertained from first and second intermediate parameters a1, a2 and is selected in particular as a=max(a1, a2). It is possible in general for first, second, and third portions 17′, 17″, 17′″ to be capable of being implemented as one shared functionality. The ascertained filter parameter a can then be made available to adaptive filter device 18. Filtered measured rotation rate sensor value x[n] is ascertained with the aid of adaptive filter device 18. An exponential smoothing can be used by adaptive filter device 18, in particular the correlation:

x[n]=(1−a)x[n−1]+ax[n],

where x[n] is the filtered measured rotation rate sensor value, a is the filter parameter, x[n−1] is the previous filtered measured rotation rate sensor value, x[n] is the instantaneous measured rotation rate sensor value, n describes the number of the measured rotation rate sensor value or the filtered measured rotation rate sensor value. The previous filtered measured rotation rate sensor value x[n−1] is preferably determined in a previous iteration analogously to the above-described determination of the filtered measured rotation rate sensor value x[n]. Filters other than the exponential smoothing described above are also possible for adaptive filter device 18.

[0037] With the aid of the example embodiment described in FIGS. 1 and 2 of a system 100, a method for offset calibration of a rotation rate sensor signal 11 of a rotation rate sensor 1 can be carried out, [0038] in a first step, an ascertainment being made that rotation rate sensor 1 is in an idle state; [0039] in a second step, after the first step, a filter parameter a being determined as a function of measured rotation rate sensor values x1, measured in idle state 15, of rotation rate sensor 1; [0040] in a third step, after the second step, a filtered measured rotation rate sensor value x[n] being determined with the aid of filter parameter a;
an offset 40 being determined with the aid of filtered measured rotation rate sensor value x[n].

[0041] It is advantageously possible for offset 40 to be used subsequently for offset correction or offset calibration of rotation rate sensor signal 11.