JPH0578770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to autopilots for aircraft, ships, etc., autonavigation for automobiles, or
The present invention relates to an angular velocity sensor that can be used in auto stabilizers of various machines and devices.

Configuration of conventional examples and their problems A so-called angular velocity sensor, a device that detects angular velocity relative to an inertial frame (referred to as absolute angular velocity in the text), uses a rotor that rotates at an extremely high speed, and detects angular velocity around an axis perpendicular to the axis of rotation. A method of detecting the torque acting on the support of the shaft in proportion to the absolute angular velocity of the shaft (referred to as the rotary drive method in this text) has been employed for a long time.

In such a rotary drive system, the structure is complicated and high precision is required because the rotor is rotated and the torque acting on the support of the rotating shaft is detected, and it is large, heavy, and expensive. The problem is that maintenance is difficult.

In order to eliminate this problem, a relatively recent method has been developed in which a mass element is given a rotational motion and the Coriolis force acting on the mass element is detected according to the absolute angular velocity around an axis perpendicular to the rotation axis. (This is referred to as the swing drive method in the text) was proposed.

The mechanism of absolute angular velocity detection in this swing drive method will be explained below using a schematic diagram.

As shown in FIG. 1, a mass point of mass m is assumed to be represented by a position vector r in an orthogonal coordinate system in which i→, j→, k→ are unit vectors.

This mass point is defined as k→(t)=r(i
→
cosωt+j→sinωt), and when the rotation is driven at a constant angular frequency ω and a constant radius r for time t, the velocity vector v→(t) at this time becomes v→(t)=dr→/dt = rω(−i→sinωt+j→cos
ωt).

Here, it is assumed that the orthogonal coordinate system rotates at an angular velocity Ω→ with respect to the inertial system. Here, Ω→ is a three-dimensional vector whose magnitude represents the angular velocity and whose direction indicates the direction of the rotation axis, and Ω→=Ω ₁ i→+Ω ₂ j→+
Suppose that it is expressed as Ω ₃ k→.

At this time, the Coriolis force F→ _c acting on the mass point is F→ _c =2mv→×Ω→ =2mrωi→ −sinωt Ω ₁ j cosωt Ω ₂ k O Ω ₃ =2mrω｛Ω ₃ (i→cosωt+j→sinωt) − (Ω ₂ sinωt+Ω ₁ cosωt)k→} =2mrω{Ω ₃ i→/r−(Ω ₂ sinωt+Ω ₁ cosωt)k
k→}. (Here, the symbol "x" is an operational symbol that represents a vector product, and "||" is an operational symbol that represents a determinant.) Here, the mass point is defined as a pressure-sensitive element that is sensitive only to the force in the k→ direction. If the force in the k → direction is detected and converted into a linear signal by replacing it with , the signal processing S(t)
can be expressed as S(t)=C(Ω ₂ sinωt+Ω ₁ cosωt), including the sign, m, r, ω, and detection sensitivity, and let C be the proportionality constant.

In the swing drive system, this S(t) is synchronously detected using sinωt or cosωt to obtain an output proportional to the j→direction component or the i→direction component of the absolute angular velocity Ω→.

In such a system, the drive system is responsible only for imparting a velocity v→ to the mass element, and maintaining it does not require the same complexity required to pick up torque in systems using a rotating rotor. No mechanism or high precision is required, allowing for a significant reduction in hardware.

However, as is clear from looking at S(t),
When a deviation occurs in the reference phase of synchronous detection, a component in a different direction orthogonal to the desired direction component is mixed in, that is, so-called crosstalk occurs.

This crosstalk can be a fatal drawback, especially in applications where high precision is required.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems in swing drive type angular velocity sensors and to provide a high-performance angular velocity sensor free from crosstalk.

Configuration of the Invention The angular velocity sensor of the present invention includes two mass elements,
A driving means that provides a constant angular velocity with opposite signs and the same magnitude and a rotating motion of a constant radius, and a force acting on each of the two mass elements is independently detected and an output corresponding to the component in the direction of the rotating axis. By calculating the sum and difference of the signals from the two detection means, the degree of separation between the necessary direction component and the opposite direction component of the absolute angular velocity can be dramatically increased. This makes it possible to eliminate crosstalk that appears in the final output.

DESCRIPTION OF EMBODIMENTS First, the angular velocity detection operation of the angular velocity sensor of the present invention will be described using schematic diagrams.

As shown in Fig. 2, in a rectangular coordinate system with unit vectors i→, j→, k→, the position vectors r→ ₁ (t)=r(i→codωt+j→sinωt), r
→ ₂ (t)
A mass point of equal mass m that rotates in the opposite direction in the form = r {i → cos (-ωt) + i → sin (-ωt)}
Assume P ₁ and P ₂ .

The orthogonal coordinate system has an angular velocity Ω→= with respect to the inertial frame.
When rotating at Ω ₁ i→+Ω ₂ j→+Ω ₃ j→, the mass point P ₁
，
The Coriolis forces F→ _c1 and F→ _c2 acting on P ₂ are F→ _c1 = 2mrω{Ω ₃ r→ ₁ /r−(Ω ₂ sinωt+Ω ₁ cosω
t)
k→｝ F→ _c2 =2mrω{Ω ₃ r→ ₂ /r−(−Ω ₂ sinωt＋Ω ₁ cos
ωt)
k → }.

Here, if we replace the mass points P ₁ and P ₂ with pressure-sensitive elements that are sensitive only to the force in the k direction, and convert each of the forces acting in the k → direction into a linear signal with equal sensitivity, the output signal S ₁ (t), S ₂ (t) are signs,
Including m, r, ω, and detection sensitivity, and assuming that the proportionality constant is C, S ₁ (t) = C{Ω ₂ sinωt + Ω ₁ cosωt) S ₂ (t) = C{−Ω ₂ sinωt + Ω ₁ cosωt) becomes.

Here, if we add and subtract S ₁ (t) and S ₂ (t) and let the results be S ₃ (t) and S ₄ (t), respectively, then S ₃ (t) = 2CΩ ₁ cosωt S ₄ (t)=2CΩ ₂ sinωt, and the components corresponding to the i→ and j→ components of the absolute angular velocity are canceled out, leaving only one direction component.

In an actual device, due to various mismatches, S ₁ (t)
C in S ₂ (t) and C in S 2 (t) do not completely match, and S ₃ (t) and S ₄ (t) also have a slight component in the opposite direction.
It is only compressed to ΔC/2 times the required component ratio, and even if there is some phase error during subsequent synchronous detection, it hardly appears as crosstalk.

This completes the explanation of the operation of removing components in different directions of the angular velocity sensor of the present invention, and describes the configuration for realizing a practical angular velocity sensor and the functions of each component using an example of a device using a piezoelectric bimorph as a pressure sensitive element. This will be explained using drawings.

FIG. 3 is a sectional view showing the configuration of a driving section and a detecting section in an embodiment of the angular velocity sensor of the present invention.

In FIG. 3, 1 is a motor which is a driving source, and this rotation is transmitted through gears 2a, 2b, 3 and 4 to drive rotating shafts 5a and 5b.
A pair of rotating units 6a and 6b are rotated in opposite directions.

The two pairs of piezoelectric bimorph elements 7a and 7b rotate in opposite directions by this rotating shaft.

Each piezoelectric element has one end attached to a support block 8.
It has a cantilever shape supported by points a and 8b, and when a force in the direction k is applied, it bends and generates an electrical output. That is, the piezoelectric elements 7a and 7b are mass elements that are rotated, and also act as detection elements that detect the force acting on themselves.

In this state, the device is rotated in the direction of the rotation axis (k → direction).
When the angular velocity in the direction (i→ and j→ direction) perpendicular to the piezoelectric element 7 acts, the piezoelectric element 7
A Coriolis force in the k direction acts on a and 7b, generating an electrical output.

The electrical output is taken out to the outside via printed circuit boards 9a, 9b, rotors 10a, 10b, and brushes 11a, 11b, and an angular velocity signal is obtained by signal processing described later.

FIG. 4 shows a state in which a cantilever-shaped piezoelectric element is installed on a printed circuit board. Note that since the pair of rotating units 6a and 6b are constructed identically, only one is shown and the suffixes a and b are omitted.

One side of a pair of metal support blocks 8 is fixed by soldering on a ground electrode 12 provided on a printed circuit board 9 symmetrically with respect to the rotation axis, and one end of a pair of piezoelectric elements 7 is soldered to the opposite side. . The surface of the piezoelectric element 7 at one end, which faces the surface to be joined with the support block, is connected to the signal electrode 13 by a lead wire.

The pair of piezoelectric elements 7 are polarized in opposite directions, and their output signals cancel each other out against forces that act equally in the k→direction, and enhance each other against forces that act in opposite directions.

With this configuration, the pair of piezoelectric elements 7 have velocities in opposite directions due to the rotating motion, and the Coriolis force acts in opposite directions, so that the piezoelectric elements 7 are
It is possible to obtain twice the electrical output compared to the case where only one is provided, and it is possible to effectively detect angular velocity by canceling components corresponding to disturbances acting in the same direction.

In the figure, the reason why the ground electrode is provided to surround the signal electrode is to prevent noise from being mixed into the low-level, high-output impedance signal.
Furthermore, the entire rotating unit is made of metal and is grounded and shielded.

FIG. 5 is a block diagram showing signal processing in an embodiment of the angular velocity sensor of the present invention.

As mentioned above, the electrical outputs of the piezoelectric elements 7a and 7b are sinusoidal with a phase difference of π/2 or -π/2 for the i→direction component and the j→direction component of the angular velocity acting on the device. It is weighted and synthesized.

Charge amplifiers 14a and 14b are piezoelectric elements 7
The high output impedance electrical outputs of a and 7b are taken out as a short circuit charge signal and converted into a low impedance high voltage signal.

15a and 15b are band-pass amplifiers whose center frequency is the rotational angular frequency of the motor 2, which effectively amplifies the component corresponding to the Coriolis force included in the voltage signal and removes noise components with far different frequencies. do.

This amplified signal is sent to adder 16a+b, subtracter 16
For the two-direction components that are added and subtracted by a-b and converted into electrical signals among the three-direction components of the action angular velocity,
Add one and cancel the other to obtain only the necessary directional component.

However, due to mismatches such as piezoelectric element sensitivity,
A slight component in the opposite direction is mixed in the outputs of 6a+b and 16a-b. Synchronous detector 17a+b, 17a-
b completely removes this slightly remaining different direction component.

The phase reference signal for phase detection is obtained by converting the signal from the pulse generator installed in the motor into phase reference generator 1.
8 to form a waveform and supply it.

After that, low pass filters 19a+b, 19
The ripple component is removed by a-b, and the DC amplifier 20a is
+b, 20a-b to set the desired sensor sensitivity.

As described above, according to this embodiment, the turning motion→
Through a series of processes of Coriolis force detection, the spatial orthogonality of the absolute angular velocities is replaced by the temporal orthogonality of the output signals, and by providing two detection means that rotate in opposite directions, this can be achieved. By shifting the relative relationship of temporal orthogonality by 180°, it is possible to remove components in different directions at the AC stage by addition and subtraction, which dramatically reduces the occurrence of crosstalk due to subsequent synchronous detection errors. It makes it possible.

In this embodiment, cantilever-shaped piezoelectric elements each driven in opposite directions are provided in pairs, but this is for the purpose of removing disturbance components, and angular velocity detection is possible even with just one of each. .

In addition, the driven mass element is a cantilever-shaped piezoelectric element that detects the force acting on itself, but the mass element is provided at the tip of a leaf spring-shaped electrode to oppose a fixed electrode, and this is driven to rotate. The force acting on the mass element can also be detected by a method such as detecting a change in capacitance between a leaf spring-like electrode and a fixed electrode.

Effects of the Invention As is clear from the above description, the angular velocity sensor of the present invention has a drive means that gives two mass elements constant angular velocities with opposite signs and equal magnitudes and a uniform turning motion with a constant radius. , two force detection means that independently detect the force acting on each of the two mass elements and generate an output according to the component in the direction of the rotation axis, and the two force detection means By calculating the sum and difference of the outputs, it is possible to almost completely separate the required direction component of absolute angular velocity from the component in a different direction at the AC stage, realizing highly accurate absolute angular velocity detection with almost no crosstalk. .

This makes it possible to apply a swing-driven angular velocity sensor that dramatically reduces the hardware burden to control systems that require highly accurate angular velocity detection, which has traditionally been limited to methods using high-speed rotors. It is expected that it will provide more possibilities for its use and also expand its range of applications.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the operation of a conventional angular velocity sensor, FIG. 2 is a schematic diagram for explaining the operation of the angular velocity sensor of the present invention, and FIG. 3 is a schematic diagram for explaining the operation of the angular velocity sensor of the present invention. FIG. 4 is a sectional view showing the driving section and the detecting section, FIG. 4 is a perspective view showing the detecting section, and FIG. 5 is a block diagram showing a signal processing circuit in one embodiment of the angular velocity sensor of the present invention. 1... Motor, 2a, 2b, 3, 4... Gear, 5a, 5b... Rotating shaft, 6a, 6b... Rotating unit, 7a, 7b... Piezoelectric element, 8a, 8b
...Support block, 9a, 9b...Printed circuit board, 10a, 10b...Rotor, 11a, 11b
... Brush, 12 ... Earth electrode, 13 ... Signal electrode, 14a, 14b ... Charge amplifier, 15a,
15b... Bandwidth amplifier, 16a+b... Adder,
16a-b...subtractor, 17a+b, 17a-b
... Synchronous detector, 18 ... Phase reference signal generator,
19a+b, 19a-b...Low pass filter, 20a+b, 20a-b...DC amplifier.

Claims (1)

[Claims] 1. A driving means that provides two mass elements with constant angular velocities of opposite signs and equal magnitudes and a turning motion of an equal constant radius, and a drive means that independently detects the force acting on each of the two mass elements; two force detection means that generate electrical output according to the component in the direction of the rotation axis; and an addition means that adds the two electrical outputs;
A subtraction means for subtracting the two electric outputs, and two signal processing means for processing the output signals of the addition means and the subtraction means to generate signals corresponding to two specific direction components of the operating angular velocity. An angular velocity sensor characterized by: