JPH04178517A - Biaxial angular velocity meter - Google Patents

Abstract

PURPOSE:To increase a working temperature range and to reduce size and weight by arranging HPF in series between a differentiating circuit and a synchronous detecting circuit, making a current contact equal to the time constant of a voltage detector, and also making a temperature change factor approximately equal to that of the voltage detector to produce reverse polarity. CONSTITUTION:HPF 33 is inserted in a given manner in series between a differentiating circuit 22 and a synchronous detecting circuit 26, capacity 35 is arranged in a rate sensor 11, and arranged approximately in the same temperature environment as temperature environment in which piezoelectric detectors 13 and 14 are located. The magnitude of the temperature factor of the capacity 35 being equal to that of internal capacity of the piezoelectric detectors 13 and 14 and reverse polarity of a change are selected. The time constant of the HPF 33 is made equal to those of the piezoelectric detectors 13 and 14. Thus, a DC content in an output from the differentiating circuit 22 is shut off by the HPF 33, noise of a shaft rotation frequency is prevented from occurring to the synchronous detecting circuit 26. Thus, a bias regulating circuit is eliminated, a working temperature range is also increased, and a device reduced in size and weight is provided.

Description

Detailed Description of the Invention "Industrial Application Field" This invention is used for attitude measurement and control of various moving objects such as flying objects, and detects angular velocity.
This invention relates to a two-axis angular velocity meter in which a pair of piezoelectric detectors are mounted symmetrically and parallel to a rotational axis, the rotational axis is rotated, and angular velocities about two orthogonal axes in a plane perpendicular to the rotational axis are detected.

``Prior Art'' Figure 3 shows a conventional two-axis angular velocity meter. Rate sensor section 1
1 , a pair of parallel beam-shaped piezoelectric detectors 13 , 14 are mounted on the rotation axis 12 at right angles to and symmetrically to the rotation axis.

The rotating shaft 12 is rotated by a spin motor 15 at a constant speed. Coriolis force acts on the piezoelectric detectors 13.14 due to the angular velocity acting in a plane perpendicular to the rotation axis 12, and the piezoelectric detectors 13.14 deflect in opposite directions as shown by dotted lines in the figure, and this deflection causes the piezoelectric Each of the signals generated in the detectors 13 and 14 is led to a preamplifier 17 and 18 via a pick-up ring and a planar 16, respectively, and each output of the preamplifier 17 and 18 is sent to the outside of the rate sensor section 11. Filter phase shift circuit 21 in sensor electronics section 19 of
The filter phase shift circuit 21 adjusts the sensitivity and phase of both electrical signals. The outputs of the filter phase shift circuit 21 are subtracted from each other by the differential circuit 22, and the in-phase component of the acceleration along the rotation axis 11 is quickly removed.

A reference pattern plate 23 is attached to the rotating shaft 12,
In this example, a reference pattern formed on a reference pattern plate 23 is detected by a photodetector 24, and its detection output is supplied to a reference signal generator 25.

The reference signal generator 25 generates a square wave reference signal that rises when the rotating shaft 12 faces in the reference direction and then falls after 1800 rotations, and a reference signal that is delayed by 90 degrees. The output of the differential circuit 22 is synchronously detected by the synchronous detection circuit 26 using the two reference signals from the reference signal generator 25, and these two projection outputs are passed through the filter amplifier 27 as an X-axis angular velocity signal and a Y-axis angular velocity signal. Output.

"Problem to be Solved by the Invention" In this conventional two-axis angular velocity meter, if the output of the differential circuit 22 contains a DC component, the DC component is transmitted to the synchronous detection circuit 22.
6, which has the drawback of producing noise at the shaft rotation frequency, and also has the drawback of a large scale factor and cross-coupling temperature coefficient.

The transfer characteristic GP(S) of the piezoelectric detector 13.14 is expressed by the following formula: Proportionality constant Internal capacitance R1 of the piezoelectric detector C:
Internal Resistance of the Piezoelectric Detector The internal capacitance C of the piezoelectric detector generally changes with a relatively large positive temperature coefficient with respect to temperature changes.

Therefore, as the temperature increases, the time constant T increases, and the gain frequency characteristics change from curve 28 to curve 29 as shown in FIG. 4A.
As shown in FIG. 4B, the phase frequency characteristic changes from curve 31 to curve 32 so that the phase lags.

Therefore, the gain of the detected angular velocity signal increases from a to b, and the phase lags from C to d. As a result, the scale factor of the gyro meter changes relatively significantly with temperature changes.

Furthermore, the angular velocity around the X-axis and the angular velocity around the Y-axis, which is perpendicular to it, are essentially unrelated.In other words, if only the angular velocity around the X-axis is input, the X-axis angular velocity signal will be output accordingly, and the The shaft angular velocity signal is zero, but if the phase characteristics of the piezoelectric detector change due to temperature fluctuations, the phase relationship between the output of the piezoelectric detector and the reference signal will deviate from the correct state.
For example, although the Y-axis angular velocity signal should originally be zero, a Y-axis angular velocity signal appears, causing so-called cross-coupling. The temperature change coefficient of this cross-coupling is also relatively large.

As a countermeasure to this, it is possible to reduce the corner frequency of the response in the piezoelectric detector (in other words, increase the time constant T) to make it sufficiently smaller than the carrier frequency of the angular velocity signal (rotational frequency of the rotating shaft 12). It will be done. However, this method reduces the voltage output sensitivity of the piezoelectric detector and is not practical.

For this reason, in the past, in order to reduce the noise of the shaft rotation speed, it was necessary to provide a bias adjustment circuit using a differential circuit or the like and adjust it to eliminate the input high ass to the synchronous detection circuit.

Furthermore, in order to prevent the scale factor, cross force, and 7-pulling from changing due to temperature, the operating temperature range may be limited, or if use in a wide temperature range is required,
The rate sensor section 11 was controlled to a predetermined temperature so as not to be influenced by the external ambient temperature. Such temperature control goes against the desire to make the two-axis angular velocity meter smaller, lighter, and cheaper. Alternatively, a temperature sensor is attached to the rate sensor section 11, and a microprocessor corrects and calculates the angular velocity signal according to the output of the temperature sensor, thereby reducing the scale factor and the temperature change coefficient of cross coupling. However, such correction calculations using a microprocessor have been a hindrance to reducing the size, weight, and cost of a two-axis angular velocity meter.

"Means for Solving the Problem" According to the present invention, a high-pass filter is inserted between the differential circuit and the synchronous detection circuit, and the DC component is blocked and supplied to the synchronous detection circuit. At least a part of the time constant determining elements of the high-pass filter are placed in substantially the same temperature environment as the piezoelectric detector, and the time constant TM of the high-pass filter is equal to the time constant T of the piezoelectric detector. and these time constants TNs
The temperature change coefficients of T and T are approximately equal to each other and have opposite polarities.

Embodiment FIG. 1 shows an embodiment of the present invention, and parts corresponding to those in FIG. 3 are given the same reference numerals. In this invention, a high-pass filter 33 is provided between the differential circuit 22 and the synchronous detection circuit 26.
are inserted in series. For example, the high-pass filter 33 has one end of an input resistor 34 connected to the input end of the filter 33, the other end connected to an inverting input end of an operational amplifier 36 through a capacitor 35, and a non-inverting input end of the operational amplifier 36. The terminal is grounded, and a feedback resistor 3 is connected between the inverting input terminal and the output terminal.
7 are connected and configured. An input resistor 34 and a capacitor 35 are time constant determining elements of this high-pass filter 33.
Of these, the capacitor 35 is disposed within the rate sensor section 11 and is placed in approximately the same temperature environment as the piezoelectric detectors 13 and 14. As this capacitor 35, a negative polarity capacitor whose temperature coefficient of capacitance is equal in size to that of the internal capacitance C7 of the piezoelectric detector 13, 14 and whose polarity of change is opposite is used. Such a capacitor 35 can be selected from commercially available temperature compensation capacitors. Further, the time constant T8 of the high-pass filter 33 is made equal to the time constant T of the piezoelectric detectors 13 and 14. In other words, the resistance value RH of the input resistor 34 and the capacitance CM of the capacitor 35
Let the time constant TM, which is the product of , be equal to Tp.

With this configuration, the DC component in the output of the differential circuit 22 is blocked by the high-pass filter 33, and no noise at the shaft rotation frequency is generated in the synchronous detection circuit 26.

Furthermore, the transfer function C, (S) of the high-pass filter 33 is (2
), and the piezoelectric detector 13゜1 shown by the formula (1)
This is the same format as the transfer characteristic of No. 4.

T engineering S+1 TM=C11-R.

R8: Resistance value of input resistor 34 CH: Capacity of capacitor 35 KM: Proportional constant The temperature coefficient of capacitance C8 is negative and the size is equal to the temperature coefficient of internal capacitance C2, T, = TF, and capacitor 35 is a piezoelectric Since the temperature is always the same as that of the piezoelectric detectors 13 and 14, changes in gain and phase due to temperature changes in the piezoelectric detectors 13 and 14 are caused by high-pass filters 33 having the same magnitude and opposite polarity. The gain and phase of are generated and canceled, and the output of the high-pass filter 33 becomes unaffected by temperature changes in both gain and phase, and an angular velocity signal that is unaffected by temperature changes is obtained. In other words, it is possible to correct temperature changes in scale factors and cross-coupling.

The time constant T of the high-pass filter 33 is the piezoelectric detector 13.
14, the temperature change coefficients are the same, and the polarity of change is opposite.

Therefore, as shown in FIG. 2, a capacitor 35 is provided in the sensor electronics section 19, and a capacitor whose capacitance changes little with temperature changes is used as the capacitor 35, and a negative temperature-sensitive resistor is used as the input resistor 34 and the feedback resistor 37. Elements, for example thermistors, may be used and placed in the same temperature environment as the piezoelectric detectors 13,14. The reason why the feedback resistor 37 is also a temperature-sensitive resistance element and is placed in the same temperature environment as the input resistor 34 is to prevent the gain of the filter 33 from changing due to temperature changes. If necessary, temperature coefficient adjusting resistance elements 34' and 37' can be connected in series or in parallel with the input resistor 34 and the feedback resistor 37, respectively. In this way, T, I and T can be made equal, their temperature change coefficients can be made equal, and the change polarity can be made opposite. The capacitor 35 and resistors 34 and 37 are all those that change with temperature changes, are placed in the same temperature environment as the piezoelectric detector 13 and 14, TH and T are equal, and their temperature change coefficients are equal. The polarity of change may be reversed. When the rate sensor section and the sensor electronics section are placed in the same temperature environment, the capacitor 35 and the resistors 34, 37 may not be installed inside the rate sensor, but may be installed inside the sensor electronics section. Other types of high pass filters 33 can also be used.

[Effects of the Invention j] As described above, according to the present invention, since the DC component is blocked from the output of the differential circuit 22 by the high-pass filter 33, noise at the shaft rotation frequency is not generated in the synchronous detection circuit 26. As a result, the conventional bias adjustment circuit and bias adjustment can be omitted. Moreover, this high-pass filter 33
The time constant T8 of the piezoelectric detector 13.14 is changed in accordance with the temperature change of the piezoelectric detector 13.14, and the time constant T□ of the piezoelectric detector 13.1 is changed.
Since the time constant T is set equal to 4, the temperature change coefficients are equal, and the polarities are reversed, it is possible to correct the scale factor and the temperature change of cross coupling. With this correction, it is possible to control the rate sensor section 11 to a constant temperature, measure the temperature of the rate sensor section 11, and use the measured value, and it is not necessary to perform correction calculations with a microprocessor, thereby widening the operating temperature range. I can do it. As a result of the above, a two-axis angular velocity meter that is small, lightweight, inexpensive, and can be used over a wide temperature range can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing another example, Fig. 3 is a block diagram showing a conventional two-axis angular velocity meter, and Fig. 4 is a block diagram showing a piezoelectric detector. FIG. 6 is a diagram showing how the gain characteristics and phase characteristics change due to changes in constants.

Claims (1)

[Claims] (1) Install a pair of piezoelectric detectors perpendicularly symmetrically and parallel to each other, rotate the rotating shaft, extract the difference between the respective outputs of the two piezoelectric detectors using a differential circuit, and The output of the differential circuit is detected by a synchronous detection circuit using two reference signals indicating the rotational position that are out of phase by 90 degrees, and two orthogonal axes intersecting the rotation axis in a plane perpendicular to the rotation axis are detected. In a two-axis angular velocity meter that detects the angular velocity around At least a part of the time constant determining element of the high-pass filter is placed in substantially the same temperature environment as the piezoelectric detector, and the time constant of the high-pass filter is determined by the internal capacitance and internal resistance of the piezoelectric detector. A two-axis angular velocity meter characterized in that it is approximately equal to a constant, and its temperature change coefficient is approximately equal and has opposite polarity.