JP5245246B2 - Inertial force sensor - Google Patents

Description

  The present invention particularly relates to an inertial force sensor used in various electronic devices such as attitude control and navigation of a moving body such as an aircraft, an automobile, a robot, a ship, and a vehicle.

  Since the conventional inertial force sensor vibrates a tuning fork-like sensing element and detects the inertial force applied thereto using the Coriolis force, an AGC is installed in the drive circuit that vibrates the sensing element to keep the amplitude of the sensing element constant. A circuit is provided.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 9-281138

  However, since the AGC circuit is formed of many analog elements, the temperature characteristics of each element are accumulated and become large, and it becomes difficult to make the amplitude of the sense element constant according to the temperature change. As a result, the detection accuracy of the inertial force sensor is affected.

  Therefore, the present invention aims to solve such problems and increase the detection accuracy of the inertial force sensor.

In order to achieve this object, the present invention converts the monitor signal into a 1-bit digital value by the drive circuit, forms amplitude information based on the digital value, and sets the amplitude information to predetermined reference amplitude information. And generating correction information based on the comparison information, calculating the digital value according to the magnification obtained from the correction information, converting the digital value into a multi-bit drive signal, and converting the multi-bit drive signal to a predetermined value. Since it is converted to an output signal and output to the drive electrode, the 1-bit digital signal is a 0/1 1-bit signal. Therefore, if the magnification of the correction information is determined, the signal of “1” is replaced with that magnification. Therefore, it is possible to convert the signal into a multi-bit signal, which eliminates the need for generally performing integration processing and the like. And it has a.

The angular velocity sensor according to the present invention includes a drive electrode, a sense electrode, a sense element having a monitor electrode, a drive circuit for detecting a monitor signal output from the monitor electrode and forming a drive signal for the drive electrode, and the sense A sense circuit that electrically processes a sense signal output from the electrode, and the drive circuit converts the monitor signal into a 1-bit digital value, forms amplitude information based on the digital value, and Comparing the information with predetermined reference amplitude information , generating correction information based on this comparison information, calculating the digital value according to the magnification obtained from the correction information and converting it into a multi-bit drive signal, wherein the drive signals of the multi-bit into a predetermined output signal, which has to output to the drive electrodes, according to this configuration, the monitor driving circuit Converting a signal into a 1-bit digital value, forming amplitude information based on the digital value, comparing the amplitude information with predetermined reference amplitude information, and generating correction information based on the comparison information; Because the digital value is arithmetically processed according to the magnification obtained from the correction information and converted into a multi-bit drive signal, the multi-bit drive signal is converted into a predetermined output signal, and output to the drive electrode. Since the 1-bit digital signal is a 0/1 1-bit signal, if the magnification of the correction information is determined, it can be converted to a multi-bit signal by replacing the “1” signal with that magnification. Therefore, an inertial force sensor capable of simplifying the drive circuit can be provided.

  Hereinafter, an inertial force sensor according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows an angular velocity sensor which is an example of an inertial force sensor, and its configuration is roughly composed of a sense element 1, a drive circuit 2 that vibrates the sense element 1, and a sense signal output from the sense element 1. 3 is constituted by a sense circuit 4 for electrically processing 3.

  As shown in FIG. 2, the sense element 1 has a drive electrode 6, a sense electrode 7, and a monitor electrode 8 formed on a tuning fork-shaped silicon substrate 5. By applying the drive signal 9, the drive arm 10 of the sense element 1 is vibrated in the left-right direction in the figure, and in this state, an angular velocity is applied to the sense element 1 to generate a Coriolis force. The sense signal 3 is output from the sense electrode 7 by bending in the front-rear direction. Although not particularly illustrated, the drive electrode 6, the sense electrode 7, and the monitor electrode 8 have a structure in which a PZT thin film is sandwiched between upper and lower electrodes.

  The monitor electrode 8 detects the vibration state of the sense element 1 and outputs a signal corresponding to the vibration of the tuning fork as the monitor signal 11.

  As shown in FIG. 1, the angular velocity sensor drive circuit 2 outputs a sigma-delta modulator (hereinafter referred to as ΣΔ) 12 that AD converts the monitor signal 11 into a 1-bit digital signal, and is output from the ΣΔ12. A digital filter 13 for converting the 1-bit digital signal into a multi-bit signal, a comparison circuit 14 for detecting zero-crossing of the multi-bit signal to form phase information, and the phase information and the previous multi-bit signal for each cycle. An amplitude detection circuit 15 that detects peak-to-peak, and a correction information generation circuit 16 that generates correction information by comparing the amplitude information obtained by the detection of peak-to-peak with preset reference amplitude information. A signal processing circuit 17 that performs arithmetic processing on the 1-bit digital signal output from ΣΔ12 and correction information, and the signal processing circuit 1 A digital filter 18 for filtering the driving signal of multi bits formed by and constitute between ΣΔ19 for outputting a driving signal for the filtered multi-bit converted into driving electrode 6 to a 1-bit digital signal.

  Note that ΣΔ12 for performing AD conversion is to convert the analog signal (monitor signal 11) output from the monitor electrode 8 into a 1-bit digital signal by oversampling and sigma-delta conversion.

Then, the signal processing circuit 17 in accordance with the magnification to obtain a 1-bit digital signal to form a monitor signal in ΣΔ12 from the correction information, for example the magnification of the correction information is 1-bit digital signal by "5" is "... 0011010 ... ", The signal is converted into a multi-bit signal such as" ... 0055050 ... ". Here, since the 1-bit digital signal is a 1-bit signal of 0/1, if the magnification of the correction information is determined, it can be converted into a multi-bit signal by replacing the “1” signal with that magnification. Since the integration processing to be performed becomes unnecessary, the processing circuit can be simplified.

  By configuring the angular velocity sensor in this way, the drive circuit 2 is performed by digital signal processing, and signal fluctuations associated with temperature changes are suppressed, thereby making the amplitude of the sense element 1 constant. Thus, the detection accuracy of the angular velocity sensor can be increased.

  Since ΣΔ12 for performing AD conversion is converted into a 1-bit digital signal, the signal obtained by the I / V converter or the integrator is converted to an A / V such as a successive approximation type without using ΣΔ12 described above. Although it can be converted to a multi-bit digital signal by a D converter, ΣΔ12 has an integrator function inside as its circuit configuration, so that the circuit scale can be reduced.

  Further, since ΣΔ19 converts a multi-bit signal into a 1-bit digital signal, it can be converted into an analog signal by a D / A converter without using ΣΔ19 and output to the drive electrode 6, but is converted into a 1-bit digital signal by ΣΔ19. As a result, the sense element 1 can be directly vibrated by the 1-bit digital signal, and the circuit scale can be reduced.

  In the above-described embodiment, the angular velocity sensor is described as an example of the inertial force sensor. However, any sensor that vibrates the sense element 1 and uses the Coriolis force can be applied to an acceleration sensor or the like. is there.

  The inertial force sensor according to the present invention can increase the detection accuracy of the inertial force sensor, and is useful as an inertial force sensor used in various electronic devices.

Circuit block diagram of angular velocity sensor according to one embodiment of the present invention The figure which shows the sense element which comprises the same angular velocity sensor

1 Sense Element 2 Drive Circuit 4 Sense Circuit 6 Drive Electrode 7 Sense Electrode 8 Monitor Electrode

Claims (1)

A drive electrode, a sense electrode, a sense element having a monitor electrode, a drive circuit for detecting a monitor signal output from the monitor electrode and forming a drive signal for the drive electrode, and a sense signal output from the sense electrode A drive circuit that converts the monitor signal into a 1-bit digital value, forms amplitude information based on the digital value, and sets the amplitude information to a predetermined reference. Comparing with amplitude information , generating correction information based on the comparison information, calculating the digital value according to the magnification obtained from the correction information and converting it into a multi-bit drive signal, and converting the multi-bit drive signal to An inertial force sensor characterized by converting to a predetermined output signal and outputting to a drive electrode.

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