Physical quantity measuring apparatus and physical quantity measuring method

Patent metadata

Field	Value
Publication number	US-9740661-B2
Application number	US-201313756907-A
Country	US
Kind code	B2
Filing date	Feb 1, 2013
Priority date	Feb 2, 2012
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A physical quantity measuring apparatus of the present invention measures a physical quantity from a signal based on a physical quantity output by a physical quantity signal output apparatus. A correction signal output unit outputs a new correction signal based on a signal on the basis of a physical quantity obtained at a given measurement time, a correction signal obtained before that measurement time, and a filter coefficient. A large/small relationship determining unit determines a large/small relationship between the signal on the basis of the physical quantity and the correction signal obtained before that measurement time. A first filter coefficient output unit outputs a first filter coefficient based on the plural large/small relationships.

First claim

The invention claimed is:

1. A geomagnetic sensor comprising:
a detecting unit that detects a magnetism and outputs a geomagnetic sensor signal, on which noises are superimposed; and
a computing apparatus that computes the magnetism from the geomagnetic sensor signal,
wherein the computing apparatus comprises:
a memory unit that stores the geomagnetic sensor signal detected by the detecting unit;
a fluctuation estimating unit that estimates a fluctuation in the geomagnetic sensor signal detected by the detecting unit; and
a filter coefficient output unit which sets a filter coefficient based on the fluctuation estimated by the fluctuation estimating unit, and which outputs the filter coefficient,

wherein the fluctuation estimating unit comprises:
a first fluctuation estimating unit that estimates a first fluctuation in the geomagnetic sensor signal based on a distribution of geomagnetic sensor signals obtained at multiple measurements at different timings by the detecting unit; and
a second fluctuation estimating unit that estimates a second fluctuation in the geomagnetic sensor signal based on relation between the geomagnetic sensor signal obtained at a given measurement time by the detecting unit and a first corrected geomagnetic sensor signal obtained at a measurement time close to the given measurement time, both of the geomagnetic sensor signal and the first corrected geomagnetic sensor signal being stored in the memory unit,

wherein the filter coefficient output unit comprises:
a first filter coefficient output unit that outputs a first filter coefficient based on the first fluctuation;
a second filter coefficient output unit that outputs a second filter coefficient based on the second fluctuation; and
a filter coefficient selecting unit that selects either one of the first and second filter coefficients as the filter coefficient,

wherein the computing apparatus further comprises a correction signal output unit that outputs a second corrected geomagnetic sensor signal, in which the noises and delay to the geomagnetic sensor signal have been reduced, based on the filter coefficient, the geomagnetic sensor signal, and the first corrected geomagnetic sensor signal.

2. The geomagnetic sensor according to claim 1 , wherein
the second fluctuation estimating unit comprises a fluctuation determining unit that determines whether or not the second fluctuation in the geomagnetic sensor signal is smaller than a predetermined threshold, and
the first fluctuation estimating unit estimates the first fluctuation based on a determination result by the fluctuation determining unit.

3. The geomagnetic sensor according to claim 1 , wherein the computing apparatus comprises a magnetism measuring element that outputs the geomagnetic sensor signal necessary for measuring a target magnetism.

4. The geomagnetic sensor of claim 1 , wherein the detecting unit that detects a magnetism includes a hall element or a magnetoresistance effect element.

5. A geomagnetic sensor comprising:
a detecting unit that detects a magnetism and outputs a geomagnetic sensor signal, on which noises are superimposed; and
a computing apparatus that computes the magnetism from the geomagnetic sensor signal,
wherein the computing apparatus comprises:
a memory unit that stores the sensor signal;
a fluctuation estimating unit that estimates a fluctuation in the geomagnetic sensor signal detected by the detecting unit; and
a filter coefficient output unit which sets a filter coefficient based on the fluctuation estimated by the fluctuation estimating unit, and which outputs the filter coefficient,

wherein the fluctuation estimating unit comprises a large/small relationship determining unit that determines a large/small relationship between the geomagnetic sensor signal obtained at a given measurement time and a first corrected geomagnetic sensor signals obtained before the given measurement time, and
the filter coefficient output unit comprises a first filter coefficient output unit that outputs a first filter coefficient based on the plural large/small relationships,

wherein the filter coefficient output unit further comprises:
a second filter coefficient output unit that outputs a second filter coefficient based on the difference value calculated by the difference value calculating unit; and
a filter coefficient selecting unit that selects either one of the first and second filter coefficients as the filter coefficient,

wherein the computing apparatus further comprises a correction signal output unit that outputs a second corrected geomagnetic sensor signal, in which the noises and delay to the magnetic sensor signal have been reduced, based on the geomagnetic sensor signal, the first corrected geomagnetic sensor signal, and the filter coefficient.

6. The geomagnetic sensor according to claim 5 , further comprising:
a difference value calculating unit that calculates a difference value between the geomagnetic sensor signal obtained at a given measurement time and the first corrected geomagnetic sensor signal obtained before the given measurement time or a difference value between different corrected geomagnetic sensor signals obtained at different timings from each other and obtained before the given measurement time.

7. The geomagnetic sensor according to claim 5 , wherein
when in a desired cycle, the large/small relationship between the geomagnetic sensor signal and the first corrected geomagnetic sensor signal is relatively deviated to either large or small, the first filter coefficient output unit outputs, as the first filter coefficient, a coefficient that increases a contribution of the sensor signal to the second corrected geomagnetic sensor signal, and
when there is no relative deviation in the large/small relationship between the geomagnetic sensor signal and the first corrected geomagnetic sensor signal, the first filter coefficient output unit outputs, as the first filter coefficient, a coefficient that increases a contribution of the first corrected geomagnetic sensor signal to the second corrected geomagnetic sensor signal.

8. The geomagnetic sensor according to claim 6 , wherein the second filter coefficient output unit outputs the second filter coefficient based on a difference value between the geomagnetic sensor signal obtained at a given measurement time and the first corrected geomagnetic sensor signal obtained right before the given measurement time, and a difference value between the geomagnetic sensor signal obtained at the given measurement time and a corrected geomagnetic sensor signal obtained two time points before the given measurement time.

9. The geomagnetic sensor according to claim 6 , wherein
when the difference value between the geomagnetic sensor signal and the first corrected geomagnetic sensor signal or the difference value between the different corrected geomagnetic sensor signals from each other is relatively large, the second filter coefficient output unit outputs, as the second filter coefficient, a coefficient that increases a contribution of the geomagnetic sensor signal to the second corrected geomagnetic sensor signal, and
when the difference value between the geomagnetic sensor signal and the first corrected geomagnetic sensor signal or the difference value between the different corrected geomagnetic sensor signals from each other is relatively small, the second filter coefficient output unit outputs, as the second filter coefficient, a coefficient that increases a contribution of the first corrected geomagnetic sensor signal to the second corrected geomagnetic sensor signal.

10. The geomagnetic sensor according to claim 5 , wherein the filter coefficient selecting unit selec

Assignees

• Asahi Kasei Microdevices Corp

Inventors

• Kitaura Munehiro
• Mikoshiba Norihiko

Classifications

• G10L21/0208

  Noise filtering · CPC title

• G06F17/00 Primary

  Digital computing or data processing equipment or methods, specially adapted for specific functions (information retrieval, database structures or file system structures therefor G06F16/00) · CPC title

• G01D3/032 Primary

  affecting incoming signal, e.g. by averaging; gating undesired signals · CPC title