JP5245247B2 - 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 includes an I / V converter to which the monitor signal is input, and a comparator that converts an output signal from the I / V converter into a rectangular wave signal. Based on the wave signal, the output signal is converted to a 1-bit digital signal by sigma-delta conversion to form amplitude information, the amplitude information is compared with predetermined reference amplitude information, and correction information is obtained based on the comparison information. Since the rectangular wave signal is generated and converted into a multi-bit signal according to the magnification obtained from the correction information, the rectangular wave signal formed by the comparator is converted into a discrete signal, and the discrete signal is obtained from the correction information. In accordance with the magnification, the signal is converted into a multi-bit signal, which eliminates the need for a generally performed integration process and the like, thereby simplifying the processing circuit. And it has a effect that that.

The inertial force sensor of 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, A sense circuit that electrically processes a sense signal output from the sense electrode, and the drive circuit receives an I / V converter to which the monitor signal is input and an output signal from the I / V converter. A comparator for converting into a rectangular wave signal, and based on the rectangular wave signal, the output signal is converted into a 1-bit digital signal by sigma-delta conversion to form amplitude information, and the amplitude information is set to a predetermined reference amplitude. compared with information, and generates the correction information based on the comparison information, into a multi-bit signal by processing the square-wave signal in accordance with the magnification obtained from the correction information, the The multi-bit signal is converted into a signal of a predetermined output format and output to the drive electrode, and the calculation process is performed by calculating a rectangular wave signal formed from the monitor signal and comparison information. For example, the rectangular wave signal formed by the comparator is converted into a discrete signal, and the discrete signal is converted into a multi-bit signal according to the magnification obtained from the correction information. Since it becomes unnecessary, an inertial force sensor capable of simplifying the processing 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 converts the I / V converter 12 to which the monitor signal 11 is input and the output signal from the I / V converter 12 into a 1-bit digital signal. A sigma-delta modulator (hereinafter referred to as ΣΔ) 13 for conversion, a digital filter 14 for converting the 1-bit digital signal into a multi-bit signal, and reference amplitude information in which amplitude information of the multi-bit signal is set in advance. The correction information generation circuit 15 that generates correction information in comparison with the above, the comparator 16 that converts the output signal from the I / V converter 12 into a rectangular wave, and the rectangular wave signal is converted into a discrete value at a predetermined period. A signal processing circuit 17 that performs arithmetic processing with the correction information, a digital filter 18 that filters the multi-bit signal formed by the signal processing circuit 17, and the filter The digital multi-bit signal is converted to a 1-bit digital signal and output to the drive electrode 6.

  Note that ΣΔ13 is a rectangular wave signal output from the comparator 16 as an analog signal output from the I / V converter 12 as shown in FIG. 3, for example, the rectangular wave signal is High (indicated as “H” in the figure). The period is integrated each time, and this integrated signal is converted to sigma-delta conversion as an input signal to convert the amplitude information of the monitor signal 3 into a 1-bit digital signal.

Then, the signal processing circuit 17 converts the rectangular wave signal formed by the comparator 16 into a discrete signal, and , for example, according to the magnification obtained from the correction information, the magnification of the correction information is “5” and the discrete signal is “. ... 0011010..., The signal is converted into a multi-bit signal such as “. Here, since the discrete 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 signal of “1” with the magnification. Since no integration processing is required, 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 ΣΔ13 is converted into a 1-bit digital signal, the value obtained by the integrator is converted into a multi-bit digital signal by an A / D converter such as a successive approximation type without using the ΣΔ13 described above. However, since ΣΔ13 has an integrator function as its circuit configuration, the circuit scale can be reduced.

  Further, since ΣΔ19 converts a multi-bit signal into a 1-bit digital signal by arithmetic processing, it can be converted into an analog signal by a D / A converter without using ΣΔ19 and output to the drive electrode 6. This makes it possible to directly vibrate the sense element 1 with this 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 The figure which shows the flow of signal processing in the sigma delta converter which constitutes the same circuit block

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, an I / V converter to which the monitor signal is input, and a comparator that converts an output signal from the I / V converter into a rectangular wave signal. Based on the rectangular wave signal, the output signal is converted into a 1-bit digital signal by sigma-delta conversion to form amplitude information, and the amplitude information is compared with predetermined reference amplitude information. the generated correction information based on the then processing said square wave signal in accordance with the magnification obtained from the correction information into a multi-bit signal, a predetermined this multi-bit signal Into a force type of signal, and outputs to the drive electrode, the arithmetic processing, the inertial force sensor, characterized in that by operation on the comparison information with the square wave signal formed from the monitor signal.

Images