JPH0752105B2 - Angular velocity sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an angular velocity sensor used in a gyroscope.

Configuration of Conventional Example and Problems Thereof In recent years, computer technology has been developed, products having many functions have been commercialized, and demands for various sensors for that have been increased. The angular velocity sensor is also applied to navigation systems in electrical equipment, robot direction detection, drive device stabilizers, etc. All of which require small size and high performance.

Conventionally, as an inertial navigation device using a gyroscope,
The method of finding the direction of a moving object such as an airplane or a ship is mainly used. This gives a stable orientation,
Since it is a mechanical type, the device is large-scaled, the cost is high, and it is difficult to apply it to consumer equipment, which requires miniaturization.

On the other hand, a vibration gyro (Japanese Patent Laid-Open No. 58-174854) has been proposed in which an object is vibrated without using a rotational force, and the angular velocity is detected from the Coriolis force generated when the angular velocity is generated.
This vibrating gyro can be considered as a vibrating sensor having a tuning fork structure. The prototype for this structure is US Pat.
It can be seen in No. 6. According to this, a rectangular plate of a drive elastic body (for excitation) and a detection elastic body is joined linearly and orthogonally, and the Coriolis force acting on the detection elastic body having a velocity (v) is detected. To do.

The contents of the invention of JP-A-58-174854 are described in US Pat.
It is considered that two vibrating elements shown in No. 6 were joined in parallel at the free end of the driving vibrating element along the detection axis. With this method, the actual vibration information of the vibrating body cannot be obtained, so the phase information and amplitude information during large-amplitude drive cannot be obtained accurately. Therefore, it can be obtained from the detection piezoelectric bimorph excited by the drive piezoelectric bimorph. Since the Coriolis force information becomes inaccurate and zero point drift occurs, there is a limit to practical use in the DC region.

OBJECT OF THE INVENTION It is an object of the present invention to provide an angular velocity sensor with high detection accuracy, less influence on external noise, little zero-point drift, and high productivity.

According to the angular velocity sensor of the present invention, a pair of sensor elements in which the driving piezoelectric element and the detecting piezoelectric element are arranged parallel to the angular velocity detection axis and orthogonal to each other have a coupling portion on the driving piezoelectric element side. An angular velocity sensor having a tuning fork type vibrating element formed through the above and an elastic member supporting the coupling portion, wherein mechanical vibration is caused by applying a driving electric signal to one driving piezoelectric element, and the other The driving piezoelectric element is mechanically resonated through the coupling member supported by the elastic member so as to have a phase opposite to that of the one driving piezoelectric element, and a reference electric signal is taken out from the other driving piezoelectric element. The control electric signal is controlled by the reference electric signal. As a result, the left and right sensor elements vibrate in a precisely matched state, and the phase and amplitude signals of the vibration, which are important for the detection circuit, are obtained from the driving piezoelectric element, so there is little zero-point lift and detection accuracy. Can be made high, and it becomes a sensor that is strong against external noise.

Description of Embodiments One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a plan view of an angular velocity sensor in one embodiment of the present invention, and FIG. 2 shows a side view. FIG. 3 shows a circuit block diagram.

In FIGS. 1 and 2, 1 is a detecting piezoelectric element, 2 is a driving piezoelectric element, 3 is a driving detecting piezoelectric element, 4 is a conductive member, 5 is a metal elastic member, 6 is a base, and 7 is a joining member. .

The operation of the angular velocity sensor of the present embodiment configured as described above will be described below.

First, a drive signal (resonance frequency) is applied to vibrate only the drive piezoelectric element 2. At this time, the lead wire is made as thin as possible and soldered near the conductive member 4 which hardly affects vibration. Alternatively, instead of using the lead wire, an alternative means may be used. The sensor element composed of the driving piezoelectric element 2 and the detecting piezoelectric element 1 that have started to vibrate is joined to the other through the conductive member 4 within a start time of less than 1 second and the driving detecting piezoelectric element 3 and the detecting element. Piezoelectric element 1
Mechanically resonates with the sensor element consisting of and starts symmetrical tuning fork vibration.

In order to accurately vibrate the tuning fork, it is important that the metallic elastic member 5 eliminates the misalignment due to the left and right assembly accuracy, so that the left and right symmetrical vibration modes can be obtained. Since no electric signal is applied to the drive detection piezoelectric element 3, the conversion characteristics of the piezoelectric material, that is, mechanical energy can be taken out as electric energy from the piezoelectric element 3, so that the actual vibration state is an electric signal. Can be taken out as. The signals at this time are a phase signal and an amplitude signal. This signal plays a very important role for the vibrating angular velocity sensor. The role will be described in detail in the circuit relation.

In order to match the mechanical impedances of the drive piezoelectric element 2 and the drive detection piezoelectric element 3, it is preferable that they have the same size and shape and the same piezoelectric material.

It has been found that since the detection piezoelectric element 1 has matched tuning fork vibration, it has a high canceling effect against acceleration and a canceling effect against disturbance noise, and the linearity of detection sensitivity is improved.

In the present embodiment, the resonance frequency of the tuning fork is designed around 300 Hz, and the drive circuit is designed accordingly. Next, the circuit operation will be described in detail with reference to the block diagram of FIG.

The drive circuit 8 is for supplying electric power for exciting the resonance system to the driving piezoelectric element, and the supplied electric power is controlled by a signal from a drive information extraction circuit described later, and serves as an angular velocity sensor. The vibration state of the resonance system is maintained so that a constant sensitivity is always obtained.

Here, in order to maximize the drive efficiency, it is necessary to drive at the resonance frequency of the resonance system. For that purpose, the drive circuit is composed of an oscillation loop including a driving piezoelectric element as a frequency selection element, and Insert a variable gain amplifier into
The gain can be maintained at a predetermined amplitude by adjusting the Gain distribution in the loop by the control mechanism described later.

The drive information extraction circuit 10 generates a drive amplitude signal and a drive phase signal in response to an output signal of a drive detection piezoelectric element (hereinafter referred to as a monitor signal), and specifically, rectifies and smoothes the monitor signal. , Amplify and generate a DC voltage (drive amplitude signal) according to the physical vibration amplitude, and apply a suitable phase shift to the monitor signal to generate a drive phase signal that will be the reference phase in phase detection described later. Have the function to

The automatic gain adjustment circuit 9 compares the drive amplitude signal with a reference voltage and adjusts the gain of the variable gain amplifier so that the difference becomes zero.

The detection circuit 11 removes unnecessary components from the output of the detection piezoelectric element (hereinafter referred to as sense output) to extract a component corresponding to the angular velocity, and is a synchronous detection circuit using the drive phase signal as a reference phase. is there.

The filter circuit 12 is for smoothing the detection output and generating an output according to the angular velocity.

In the above configuration, by using the same material for the driving piezoelectric element, the drive detection piezoelectric element, and the detection piezoelectric element,
Not only is it possible to obtain an ideal resonance system that is bilaterally symmetrical, but it is also possible to obtain a stable output by absorbing changes in the characteristics of the element due to temperature and the like.

For example, the drive amplitude signal, which reflects the physical vibration amplitude, includes the mechanical-electrical conversion efficiency of the piezoelectric element as its coefficient, and by controlling this constant, the Coriolis force is sensed. When converting to output, by absorbing the change in conversion efficiency in the mechanical-electric conversion of the piezoelectric element for detection, as a result, the coefficient relationship connecting the angular velocity and the sense output,
Can be kept constant at all times.

This cannot be realized by a method of simply driving the driving piezoelectric element with a constant current or a constant voltage.

Further, even in phase detection for extracting an angular velocity component from the sense output, the relative phase change between the acting force and the sense output, which occurs during the mechanical-electrical conversion of the sensing piezoelectric element, is absorbed, and An ideal reference synchronized with the angular velocity component can be obtained, and it is possible to completely extract the angular velocity component and completely remove the driving inertia force component.

EFFECTS OF THE INVENTION As is clear from the above description, according to the present invention, a pair of sensor elements in which the driving piezoelectric element and the detecting piezoelectric element are arranged parallel to the angular velocity detection axis and orthogonal to each other are provided on the driving piezoelectric element side An angular velocity sensor having a tuning fork type vibration element formed via a coupling portion and an elastic member supporting the coupling portion, wherein a driving electric signal is applied to one of the driving piezoelectric elements. The other driving piezoelectric element is vibrated to mechanically resonate through the coupling body supported by the elastic member so that the other driving piezoelectric element has a phase opposite to that of the one driving piezoelectric element. The reference electric signal is taken out and the driving electric signal is controlled by the reference electric signal, and a completely symmetrical vibration mode can be obtained in a wide range from a small amplitude to a large amplitude. It is possible to realize an angular velocity sensor that has less DC drift and is not affected by disturbance noise. Further, the vibration state of the tuning fork vibration can be monitored from the other driving piezoelectric element as an electric signal, and since it is a piezoelectric component, a sensor that is small and lightweight and consumes less power can be obtained.

Further, by using the same piezoelectric material, the effect of canceling the temperature characteristic can be obtained.

[Brief description of drawings]

FIG. 1 is a front view of an angular velocity sensor according to an embodiment of the present invention, FIG. 2 is a side view of an angular velocity sensor according to an embodiment of the present invention, and FIG. 3 is a circuit block of the angular velocity sensor according to an embodiment of the present invention. It is a figure. 1 ... Detection piezoelectric element, 2 ... Driving piezoelectric element, 3 ...
Piezoelectric element for drive detection, 4 ... Conductive member, 5 ... Metal elastic member, 6 ... Base, 7 ... Joining member, 8 ... Drive circuit, 9 ... Automatic gain adjustment circuit, 10 ... Drive information extraction Circuit, 11 …… Detection circuit, 12 …… Filter.

Claims (1)

[Claims] 1. A pair of sensor elements in which a driving piezoelectric element and a detecting piezoelectric element are arranged parallel to an angular velocity detecting axis and orthogonal to each other are formed on the driving piezoelectric element side via a coupling portion. An angular velocity sensor having a tuning fork type vibration element and an elastic member supporting the coupling portion, wherein mechanical vibration is caused by applying a driving electric signal to one driving piezoelectric element, and the other driving piezoelectric element is driven. Mechanical resonance is generated through the coupling member supported by the elastic member so as to have a phase opposite to that of the one driving piezoelectric element, and the magnitude of the amplitude obtained from the other driving piezoelectric element is used as a reference electrical signal. And controlling the magnitude of the driving electric signal according to the reference electric signal.