JPS61218911A - Signal processing circuit for oscillation driving type rate gyro - Google Patents

Abstract

PURPOSE:To detect an attitude accurately by detecting inertial angular velocity by adding/subtracting a signal proportionate to driving acceleration of simple harmonic oscillation driving to/from a deviation detection signal. CONSTITUTION:A differentiator 6 generates a driving acceleration signal 6' from output 4' of a driving speed signal source 4, and a variable gain amplifier 7 generates a cancellation signal of amplitude corresponding to driving inertial force component included in a deviation detection signal 1' from a driving acceleration signal 6'. An adder subtracter 9 adds/subtracts a cancellation signal to/from output of band pass filter 2 by polarity of driving inertial force component included in output of the band pass filter 2. In such a constitution, driving inertial force component included in the deviation detection signal 1' is almost removed before phase detection processing by a phase detector 3. For a low band filter 9 inserted after phase detection, necessary minimum one that can remove ripple caused by true signal component is enough for the purpose, and frequency characteristic as a device is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rate gyro that detects the inertial angular velocity of an object, and more particularly to a signal processing circuit for a vibration type rate gyro driven by simple harmonic motion.

(Prior Art) There are various devices that measure the rotation rate with respect to an inertial system, which is generally referred to as inertial angular velocity.
ar rate 5 sensor or Angular
velocity sensor), rate gyro, angular velocity detector (Angu-1ar rate sensor)
It is called by various names such as ng device). Hereinafter, the term "rate gyro" will be used in the present invention.

Conventionally, various rate gyros have been proposed, but the operating principles common to all of them are: 1) The mass element is forcibly driven within the measured coordinate system. 2) The driving causes the measured coordinate system to change. 3) Detecting the force acting on the mass element, and detecting the deviation according to the Coriolis force from the shift detection signal. After extracting the components and applying signal processing according to the generation mechanism of Coriolis force,
It can be said that an output proportional to the inertial angular velocity is obtained.

By the way, the various rate gyros that have been proposed so far are characterized by their drive method (simple harmonic drive, rotational drive, linear emission), drive method (those using electromagnetic action, those using piezoelectric effect) mass elements to which the Coriolis force is applied (e.g., cantilevers, tuning forks, vibrating parts of strings, rotor itself, emitted gas, etc.), and methods for detecting the Coriolis force (such as those using electromagnetic action). , those using piezoelectric effects, those using cantilevers, those using torque springs, etc.), and the way they are classified differs depending on the point of view.

The rate gyro device targeted in the present invention focuses on the drive method among the above-mentioned classification elements, and uses simple harmonic drive.
Vibration driven rate gyro
This vibration-driven rate gyro, which belongs to the ``river rate gyro'' category, differs in the other factors mentioned above.For example, the cantilever beam is vibrated by electromagnetic force, and the deviation caused by the Coriolis force that occurs at the tip of the beam is electromagnetically corrected. those that use piezoelectric effects for sensing, or those that utilize piezoelectric effects for excitation, detection, or both (both are disclosed in U.S. Patent No. 25446).
No. 46), a tuning fork is excited by electromagnetic force, and the Coriolis force acting on its tip is converted into torque around the tuning fork support shaft, which is detected by a torque lever (U.S. Pat. No. 26).
83596) etc.

In the above two cases as well as in other cases, all vibration-driven rate gyros can detect the true signal component contained in the obtained deviation detection signal, that is, the component corresponding to the Coriolis force ( In turn, the component proportional to the inertial angular velocity) has the following characteristics: (1) It has a frequency equal to the vibration drive frequency, and (2) It has a phase equal to the vibration drive speed. This is because the Coriolis force is proportional to the vector product of the vibration drive speed and the inertial angular velocity.

Conventionally, as a signal processing method to obtain an output proportional to the inertial angular velocity from a deviation detection signal by utilizing the characteristics of the true signal component, after appropriate frequency discrimination, a standard synchronized with the vibration driving speed has been used. It is common to perform phase detection on the signal (for example, US Pat. No. 3,258,617).

FIG. 2 is a block diagram showing the conventional signal processing circuit as described above. In FIG. 0, 1 is the force acting on the mass element;
Or it is a deviation detection signal source that generates an electrical output according to the torque generated thereby.

In addition to the signal component corresponding to the Coriolis force, which is the true necessary signal component, the output includes gravity, an inertial force as a reaction force based on the translational acceleration of the measured coordinate system with respect to the inertial coordinate system, and an inertial force due to rotational motion. Also included are signal components corresponding to centrifugal force, inertial force (driving inertial force) caused by simple harmonic motion within the measured coordinate system, and the like.

2 is a bandpass filter whose center frequency is the vibration drive frequency, and among the various components included in the shift detection signal 1', components that essentially have no causal relationship with the vibration drive operation;
That is, components other than the true signal component and the component corresponding to the vibration drive inertia force are removed.

3 is a phase detector whose reference phase is the drive speed signal 4' of the drive speed signal source 4, which in principle cancels the component corresponding to the drive inertia force whose phase is orthogonal to the drive speed signal 4' in a DC manner. , the DC component of the output is extracted by a low-pass filter 5 to obtain a final output 5' proportional to the amplitude of the component corresponding to the Coriolis force, and furthermore proportional to the inertial angular velocity.

(Problems to be Solved by the Invention) According to such conventional signal processing, it is possible to certainly obtain an output having a DC component proportional to the inertial angular velocity.

However, this alone may cause a serious problem in practice.

This is because the driving inertial force (reaction force based on acceleration accompanying vibration motion) acting on the mass element is large, and this appears in the deviation detection signal 1', which is essentially the same frequency as the vibration driving frequency. Discrimination based on frequency is impossible, and even if the phase detector 3 cancels out the direct current, the drive inertia appears as an extremely large ripple component in the detected output 3'.

The amplitude of this driving inertial force reaches a value as large as 1/2ω (ω is the driving angular frequency) when converted into the inertial angular velocity required to generate a Coriolis force of the same amplitude.

At this time, since the drive inertia force acts in the direction of the drive speed and the Coriolis force acts in the direction perpendicular to the drive speed, when converting the force acting on the mass element into an electrical signal, the direction of sensitivity is set perpendicular to the drive speed. Generally, the drive inertia force is set in the direction to prevent the drive inertia force from appearing in the shift detection signal 1'.

Due to this setting error in the sensitivity direction, a component corresponding to the driving inertia force is mixed into the deviation detection signal 1'.

When the ripple due to the drive inertia generated by the above mechanism is compared with the ripple of the inertial angular velocity signal itself, it ends up being 1/2 ω tan θ. This value is
Considering the practical vibration drive frequency for measuring inertial angular velocity, several hundred to several kHz (several hundred to several hundred thousand"/5ac at angular frequency ω), and the achievable machining accuracy θ, this type of Minimum resolution required for the device: 0
．． It can be seen how large this value is compared to 0.1°/sec and a dynamic range of 100'/sea.

Conventionally, a low-pass filter is inserted to reduce such ripples, but the filter is less than what is necessary to reduce the ripples of the inertial angular velocity signal component.
A much higher order and/or lower cut-off frequency characteristic is required, which significantly impairs the frequency characteristics of the device, especially when good frequency characteristics are required, such as in applications such as attitude control of communication satellites. This is a fatal flaw.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal processing circuit for a vibration-driven rate gyro that can reduce extremely large ripples caused by drive inertia without causing a phase delay or frequency restriction of a filter or the like.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a shift detection signal that includes:
The above objective is achieved by adding or subtracting a signal proportional to the drive acceleration in proportion to the drive inertia force component contained therein before performing the phase detection process.

(Function) According to the means described above, the component of the drive inertia force mixed into the shift detection signal is canceled out by the addition/subtraction calculation, so that the output ripple is reduced without being accompanied by phase delay or frequency limitation. Therefore, the number of low-pass filters after synchronous detection can be kept to the minimum necessary, and good frequency characteristics can be obtained as a device.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the vibration-driven rate gyro signal processing circuit of the present invention.

In FIG. 1, the explanation of the same reference numerals 1 to 4 as in FIG. 2 refers to the explanation of FIG. do.

6 is a differentiator for generating a driving acceleration signal 6' from the output 4' of the driving speed signal source 4, and 7 is a variable gain amplifier for generating a deviation detection signal 1' from the driving acceleration signal 6'. A cancellation signal having an amplitude commensurate with the included drive inertia force component is generated. Reference numeral 8 denotes an adder/subtracter for adding or subtracting a cancellation signal to or from the output of the band-pass filter 2, depending on the polarity of the driving inertial force component included in the output of the band-pass filter 2.

With the above configuration, the driving inertial force component included in the shift detection signal 1' is almost removed before the phase detection processing by the phase detector 3, and the low-pass filter 9 inserted after the phase detection.
may be the minimum necessary to remove ripples due to true signal components, and may have a much lower order and/or a higher cut-off frequency than the low-pass filter 5 in the conventional technology explained in FIG. can be used. Therefore, the frequency characteristics of the device are dramatically improved.

Here, the amplitude and polarity of the driving inertial force component included in the deviation detection signal 1' depend on the aforementioned machining error θ, and there are variations between individual doubles, but this is almost entirely due to static and geometric errors. Since changes over time and temperature can be almost ignored, by initially adjusting the coefficients of the adder/subtractor 8, the canceling function can be permanently guaranteed.

In the above embodiment, a method of differentiating the drive speed signal was used to obtain the drive acceleration signal, but this can of course also be done by providing a drive acceleration signal source independent of the drive speed signal source 4. be. However, considering that the vibration-driven rate gyro requires a drive speed signal that is accurate in both phase and amplitude as its basic operating principle, this embodiment minimizes the burden on hardware. The most appropriate method is as follows.

(Effects of the Invention) As is clear from the detailed explanation above, the signal processing circuit of the present invention can realize a vibration-driven rate gyro with extremely excellent frequency characteristics, and is particularly useful for attitude control of artificial satellites. Since the posture can be detected extremely accurately and the configuration is relatively simple, it has a great effect on this field.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a signal processing circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a signal processing circuit according to a conventional example. DESCRIPTION OF SYMBOLS 1... Deviation detection signal source, 2... Band pass filter, 3... Phase detector, 4... Driving speed signal source,
5, 9...Low pass filter, 6...Differentiator, 7...Variable gain amplifier, 8...Adder/subtractor.

Claims (1)

[Claims] In a vibration-driven rate gyro that detects inertial angular velocity, a signal proportional to the driving acceleration of the simple harmonic drive is detected from the deviation detection signal obtained by detecting the force acting on the mass element driven by the simple harmonic. After canceling the drive inertia force component included in the shift detection signal by adding or subtracting it to the shift detection signal, the inertial angular velocity is detected using a phase detector with the speed of the simple harmonic drive as a reference phase. A signal processing circuit for a vibration-driven rate gyro.