JPH0334828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to means for detecting acceleration of a moving body, and more particularly to a vibratory accelerometer capable of measuring in three axial directions.

(Prior Art) The following devices are conventionally known as devices for detecting the acceleration of a moving body.

(1) Servo type As shown in Figure 3, a force coil a having a mass M supported by an elastic body d is placed in the middle of a magnetic circuit consisting of a magnet b and a core c,
The force Mα generated by acceleration α is balanced with the force generated by the force coil, and the acceleration α is determined from the current flowing through the force coil.

(2) Beam shape As shown in Figure 4, a weight g having a predetermined mass is fixed to the tip of a column f having a thin wall portion i fixed to a base e, and a strain gauge h,
By attaching h', the acceleration is determined by the change in resistance caused by the deflection of the support column f due to acceleration.

(3) Vibration type As shown in Figure 5, vibrating strings w ₁ and w ₂ are stretched across a vibration isolator m so as to face each other, and the vibration changes depending on the direction of the force received by the vibration isolator m. This method calculates acceleration from changes in the vibration frequencies f ₁ and f ₂ of a vibrating string.

(Problems to be Solved by the Invention) In the above conventional example, the servo type shown in Fig. 3 is widely used as a precision type, but it has a complicated structure and is difficult to obtain a high resolution output signal from a current signal. This has the disadvantage that signal processing is difficult.

In addition, the beam shape shown in Fig. 4 has a weight g on the support f.
The structure is simple because it is simply fixed and a strain gauge is attached, but the disadvantage is that signal processing is difficult because the gauge factor is low and the output signal is small.

The vibrating type shown in FIG. 5 outputs a signal at a frequency, has a large gauge factor, and is easy to process, but has the disadvantage that it is difficult to adjust the tension of the vibrating string and to attach the vibration separator m.

Since acceleration is measured in only one direction in these conventional examples, three accelerometers are required to measure acceleration in the XYZ directions.

(Means for solving the problems) The present invention has been made in view of the above problems, and
The purpose of this is to provide a highly accurate 3-axis accelerometer with a simple configuration and a high gauge factor. a weight having a predetermined mass fixed to a free end side; and at least three vibrating beams having both ends fixed to the base and the weight, parallel to the column, and equally spaced around the column. and excitation means for vibrating these vibrating beams, vibration detection means for detecting the natural frequency of the vibrating beam, and calculation means for calculating the natural frequency of each vibrating beam detected by the vibration detecting means. This is what I did.

(Function) When the vibrating beam is excited and acceleration is applied to the weight in the Z direction, distortion occurs in the support and the vibrating beam at the same time.
The natural frequency of the vibrating beam changes. Furthermore, when acceleration is applied to the weight in the X and Y directions, tensile strain is generated in the vibrating beam in front of the weight in the direction of movement, and compressive strain is generated in the vibrating beam in the rear, resulting in a differential change in the natural frequency of the vibrating beam. do. This change in vibration frequency is detected by the vibration detection means, and the calculation means performs calculation to separate and detect the applied acceleration in the three axial directions.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and is a perspective view showing the overall configuration. In the figure, 1 is a base with a convex cross section having large and small diameters, and in the center of the small diameter part, a cylindrical column and a column 2 are fixed perpendicularly to the base 1, and on the free end side of this column 2 there is a cylindrical column. weight 3
is fixed. Base small diameter part and weight 3
There are rectangular incisions 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 4a, 5, 5a, 4, 5a, 5a, 5a, 5a, 5b, 4a, 4a, 4a, 5a, 5a, 4b, 4a, 5b, 5a, 4a, 5a, 4a, 5a, 4a, 5a, 5a, 5a, 4a, 4a, 5a, 5a, 4a, 4a, 5a, 5a, 4a
6, 6a (6, 6a are not shown) are provided, and plate-shaped vibration beams 7a, 7b, 7c are provided in these notches.
are fixed at both ends parallel to the pillar 2 and at equal intervals. The vibrating beams 7a, 7b, 7c have elongated holes 8a, 8b, 8c (8c is not shown) near their centers.
is provided to constitute a composite tuning fork vibrator. Piezoelectric elements (not shown) for excitation and detection of the vibrating beam are pasted near the long holes 8a, 8b, and 8c, and after amplifying the voltage signal detected by the detection piezoelectric element, positive feedback is returned to the excitation element. By doing so, automatic vibration of the vibrating beam is performed. 9 is a cover, weight 3, vibration beam 7
a, 7b, and 7c, and is airtightly fixed to the large diameter part of the base 1, and is filled with vacuum or helium gas, etc., to maintain a high Q of the vibrating beam and protect it from the influence of external pressure and dirt. It is. 10a,
10b and 10c (10c not shown) are vibration beams 7
These are terminals for exciting the piezoelectric elements attached to a, 7b, and 7c and detecting the natural frequency of the vibrating beam, and one end of each terminal passes through the base 1 and is exposed to the outside of the cover 9.

In the above configuration, the piezoelectric elements attached to the vibrating beams 7a, 7b, 7c are connected to the terminals 10a, 10b, 10c.
is connected to the excitation amplifier via the oscillator, the vibrating beam is excited at a specific frequency, and when an acceleration α ₁ is applied in the Z direction, the strut 2 expands and contracts under the force Mα ₁ from the weight 3, and the strut A vibrating beam fixed parallel to 2 is subjected to compressive or tensile forces. As a result, the vibrating beam 7a,
The natural frequencies of 7b and 7c change according to their acceleration. Next, when accelerations α ₂ and α ₃ in the X or Y direction are applied, the column 2 is deflected by the forces Mα ₂ and Mα ₃ due to the weight 3, and the three pillars fixed parallel to this column and at equal intervals are bent. The vibrating beams 7a, 7b, and 7c receive compressive or tensile force depending on the direction in which the acceleration is applied, and the natural frequency of the vibrating beam differentially changes depending on the direction and magnitude of the acceleration. .

FIG. 2 is a block diagram showing an example of an electric circuit that calculates a frequency signal of a vibrating beam that changes due to acceleration. In the figure, 7a, 7b, 7c indicate the vibration beams in FIG. 1, and 11a, 11b, 11c
is an oscillation circuit for exciting the corresponding vibrating beams 7a, 7b, 7c. 12 is a calculation means, which calculates the frequency of each vibrating beam that changes according to acceleration.
f ₁ , f ₂ , and f ₃ are input to calculation means 12 .

If the relationship between the distortion and natural frequency of these three vibrating beams is determined in advance, the accelerations in the three axial directions of f ₁ , f ₂ , and f ₃ can be determined by calculation.

Since these outputs are frequency outputs, they can be easily converted to high-bit digital signals, and signal processing for calculations with a microprocessor, for example, is easy. High accuracy due to high gauge factor. Further, since the weight 3 is fixed to the support 2 and the vibrating beams 7a, 7b, and 7c are provided opposite to the support 2, the structure is simple.

In this embodiment, the shape of the vibrating beam is plate-like, and the vibrating beam is provided with elongated holes, but the vibrating beam is not limited to this example, and the vibrating beam may be a wire. Further, the number of vibrating beams is not limited to three, and a larger number may be provided.

In addition, the strut 2 and the vibrating beams 7a, 7b, and 7c are made of the same material and have a small thermoelastic coefficient, making them less susceptible to temperature changes.
-Span-C etc. are desirable.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize an accelerometer that has a simple structure, a high gauge factor, and can measure three axes simultaneously.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the overall configuration of the present invention;
The figure is a block diagram showing an example of an electric circuit.
FIG. 5 is an explanatory diagram showing a conventional example. 1... Base, 2... Support, 3... Weight, 7
a, 7b, 7c... Vibration beam, 11a, 11b, 1
1c...Excitation means, 12...Arithmetic unit.

Claims (1)

[Claims] 1 A column whose one end is fixed to a base, a weight having a predetermined mass fixed to the free end side of the column, and a column whose both ends are fixed to the base and the weight, parallel to the column, and of the column. at least three vibrating beams provided at equal intervals around the vibrating beams, an excitation means for vibrating these vibrating beams, a vibration detecting means for detecting the natural frequency of the vibrating beams, and each vibrating beam detected by the vibration detecting means. A vibrating accelerometer characterized by comprising a calculating means for calculating the natural frequency of a vibrating beam.