JP4128864B2 - Servo type accelerometer - Google Patents

Description

になる。ここで、ｍ：振子質量（ｋｇ）、ｇ：重力加速度（ｍ／ｓ²）、θ：傾斜角度、である。
また、支持バネ３ａと振子質量ｍで決まる振子系の固有振動数ｆn（Ｈｚ）は、
【数２】

になる。ここで、ｋ：バネ定数（Ｎ／ｍ）、である。
【００２６】
従って、この振子系の固有振動数ｆnは、振子の傾斜により変わるので、計測される加速度の値も変化するが、傾斜算出部７０で算出された傾斜角度分が補正されるので、より正確な加速度を算出することができる。
【００２７】
移動機構部８は、固定電極４ｂを上下方向に移動させるものであって、例えば、一端が固定電極４ｂの上面に軸を中心に回動自在に固定されたネジ軸８１と、本体ケース２に設けられ、このネジ軸８１と螺合するネジ穴８２と、ネジ軸８１を回転駆動させるモータ８３などにより構成されている。そして、モータ８３が駆動することによりネジ軸８１が回転して、固定電極４ｂを上下に移動させることができるようになっている。
【００２８】
移動制御部９は、振子質量が中立位置時に検出される駆動コイル２ｂに流れる電流値の入力により、この入力された電流値が所定値よりも大きくなった場合に、移動機構部８のモータ８３を駆動させて固定電極４ｂを所定量（例えば、駆動コイル２ｂからの電流値が零となる位置）だけ移動させる。
即ち、支持バネ３ａがクリープ変形すると、支持バネ３ａの静たわみ位置が下方に下がるが、サーボアンプ５と駆動部２により、支持バネ３ａを元の中立位置に戻そうとするため、電流が駆動コイル２ｂに流れる。この電流値が所定値を超えた場合に、移動制御部９は、移動機構部８のモータ８３を駆動させることにより固定電極４ｂを移動させて、中立位置を変更する。
これにより、支持バネ３ａがクリープ変形しても、それに対応して固定電極４ｂの位置を移動させることができることとなって、非線形バネを使用して、より高感度且つ小型化が可能なサーボ型加速度計１０を提供することができる。
【００２９】
信号出力部１１は、移動制御部９の制御によって固定電極４ｂが移動した際の移動開始時及び移動終了時に各々信号を、図示しない記録部へ出力させる。
記録部（図示省略）は、信号出力部１１から出力された信号を加速度データと対応付けて記憶する。
【００３０】
次に、上記構成のサーボ型加速度計１０における傾斜補正動作について説明する。
まず、傾斜計測部６は、本体に取り付けられた水平振子６２が中立位置から変位すると、中央位置に戻そうとして、フォースコイル（図示省略）に電流を流す。このフォースコイル（図示省略）に流れた電流値から傾斜算出部７０により傾斜角度が算出され、算出された傾斜角度が加速度補正部７に出力される。加速度補正部７では、入力された傾斜角度分を補正して加速度を算出する。
【００３１】
次に、上記構成のサーボ型加速度計１０における可動極板４ａの中立位置補正動作について説明する。
まず、移動制御部７は、振子３が静たわみ位置に位置する時に駆動コイル２ｂに流れる電流値が所定値を超えたか否か判断し、超えたと判断した場合には、移動機構部６のモータ６３に駆動信号を出力すると同時に、信号出力部１１に移動開始信号を出力させる。すると、モータ６３は、回転駆動してネジ軸６１が回転し、固定電極４ｂが下方に移動する。そして、固定電極４ｂの移動に伴い可動極板４ａの中立位置も下方に移動し、駆動コイル２ｂに流れる電流値が減少する。そして、電流値が所定値となった場合には、移動制御部７は、移動機構部６のモータ６３に駆動停止信号を出力すると同時に、信号出力部１１に移動終了信号を出力させる。
【００３２】
以上説明した本発明に係るサーボ型加速度計１０によれば、傾斜計測部６により、本体ケース１の傾斜角度が計測され、この計測された傾斜角度に基づいて振子３に加わる加速度が補正されるので、駆動コイル２ｂに流れた電流から、傾斜成分の影響を排除することができることとなって、より精度の高い加速度を測定することができる。
【００３３】
また、支持バネ３ａとして非線形バネを用いることで、低バネ定数としても静たわみ量を少なくすることができることとなって、高感度且つ小型のサーボ型加速度計を提供することができる。
ここで、振子３を支持する支持バネ３ａを非線形バネとしたことにより、サーボ型加速度計１０の加速度データにおける傾斜成分の影響が線形バネに比べて顕著になるが、傾斜成分の補正ができるため、傾斜による測定精度の低下を防止することができるので、高感度且つ小型の加速度計を提供することができる。
【００３４】
なお、上記説明したサーボ型加速度計１０は、上記構成のものに限るものではなく、同様の作用効果を奏する範囲内で適宜変更してよい。
支持バネ３ａは、非線形バネでなく、線形バネを用いても良い。
移動機構部８は、ネジ軸８１を駆動して固定極板４ｂを移動するものに限らず、例えば、リフト機構により移動させてもよく、固定極板４ｂを精度良く移動できる機構であればどのようなものであってもよい。
【００３５】
【発明の効果】
請求項１記載の発明によれば、傾斜計測部により、本体ケースの傾斜角度が計測され、この計測された傾斜角度に基づいて振子に加わる加速度が補正されるので、駆動コイルに流れた電流から、傾斜成分の影響を排除することができることとなって、より精度の高い加速度を測定することができる。
また、非線形バネを用いることで、低バネ定数としても静たわみ量を少なくすることができることとなって、高感度且つ小型のサーボ型加速度計を提供することができる。
即ち、振子を支持する支持バネを非線形バネとしたことにより、サーボ型加速度計の加速度データにおける傾斜成分の影響が線形バネに比べて顕著になるが、傾斜成分の補正ができるため、傾斜による測定精度の低下を防止することができるので、高感度且つ小型の加速度計を提供することができる。
さらに、支持バネがクリープ変形しても、それに対応して固定電極の位置を移動させることができるので、非線形バネを使用して、より高感度且つ小型化が可能なサーボ型加速度計を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るサーボ型加速度計の断面図及び主要構成のブロック図を模式的に示した図である。
【図２】線形バネと非線形バネのバネ特性を説明するための図である。
【図３】従来のサーボ型加速度計の断面図及び配線図を模式的に示した図である。
【符号の説明】
１ 本体ケース
２ 駆動部（駆動制御部）
２ｂ 駆動コイル
３ 振子
３ａ 支持バネ
４ 変位検出部
４ａ 可動極板
４ｂ 固定極板
５ サーボアンプ（駆動制御部）
６ 傾斜計測部
７ 加速度補正部
１０ サーボ型加速度計
６１ ネジ軸
６２ ネジ穴
６３ モータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo-type accelerometer, and more particularly to a servo-type accelerometer that measures acceleration in the vertical direction with higher accuracy.
[0002]
[Prior art]
Conventionally, for example, as shown in FIG. 3, the servo accelerometer 100 includes a drive unit 102, a pendulum 103, a displacement detection unit 104, a servo amplifier 105, and the like provided in a main body case 101.
[0003]
The drive unit 102 includes a permanent magnet 102a fixed to the main body case 101, and a drive coil 102b wound around the pendulum 103 and arranged to face the permanent magnet 102a, and allows a current to flow through the drive coil 102b. As a result, an electromagnetic force is generated in the drive coil 102b, whereby the pendulum 103 attached to the drive coil 102b moves.
[0004]
A support spring 106 and a damper 107 are provided in parallel between the pendulum 103 and the permanent magnet 102a.
The displacement detection unit 104 measures the change in the capacitance of the capacitor C formed between the movable plate 104a attached to the pendulum 103 and the fixed plate 104a on the main body case 101 side. The displacement is detected and output to the servo amplifier 105.
The servo amplifier 105 inputs the output of the displacement detection unit 104 and controls the amount of current of the drive coil 102b of the drive unit 102 in order to apply an electromagnetic force for returning the pendulum 103 to the neutral position.
[0005]
In the servo-type accelerometer 100 configured as described above, when acceleration is applied to the pendulum 103 and deviates from the neutral position, the displacement detection unit 104 detects this deviation amount based on the capacitance change amount, and this capacitance change. Based on the quantity, the servo amplifier 105 controls the return of the pendulum 103 to the neutral position by passing a current through the drive coil 102b of the drive unit 102.
And the acceleration added to the pendulum 103 is detectable by measuring the electric current which flowed through the drive coil 102b (refer patent document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-153479
[Problems to be solved by the invention]
By the way, the servo-type accelerometer may be used by being embedded in the ground as a seismometer, for example. In the ground, the attitude of the servo accelerometer may change due to crustal movements. When the attitude of the servo-type accelerometer changes, the natural frequency increases, which affects the accuracy of measured acceleration.
[0008]
An object of the present invention is to provide a servo-type accelerometer that can measure vertical acceleration more accurately without being affected by the installation posture.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is, for example, as shown in FIG. 1, a pendulum 3 supported in a main body case 1 so as to be movable up and down by a support spring 3 a, and a neutral position of the pendulum. The displacement detector 4 detects the displacement by the amount of change in capacitance between the fixed electrode 4b provided on the main body case and the movable electrode 4a provided on the pendulum, and the displacement detector detects the displacement. A drive control unit (e.g., drive unit 2, servo amplifier 5) that causes the pendulum to return to the neutral position by passing a current through the drive coil 2b that moves the pendulum based on the amount of change in capacitance; In the servo-type accelerometer 10 that measures the acceleration applied to the pendulum according to the current value passed through the drive coil,
A moving mechanism 8 for moving the fixed electrode up and down by driving a motor;
When the drive control unit applies a current to the drive coil to return the pendulum to the neutral position, the current value supplied to the drive coil detected at the neutral position is greater than a predetermined value. And a movement control section 9 for controlling the movement of the fixed electrode to a position where the current value from the drive coil becomes zero by driving the motor of the movement mechanism section;
An inclination measuring unit 6 provided in the main body case for measuring an inclination angle of the main body case;
An acceleration correction unit 7 for correcting the acceleration of the pendulum based on the inclination angle measured by the inclination measurement unit;
And the support spring is a non-linear spring .
[0010]
According to the first aspect of the present invention, since the inclination angle of the main body case is measured by the inclination measuring unit and the acceleration applied to the pendulum is corrected based on the measured inclination angle, the current flowing through the drive coil is corrected. Thus, the influence of the tilt component can be eliminated, and the acceleration can be measured with higher accuracy.
Further, by using a non-linear spring, the amount of static deflection can be reduced even with a low spring constant, and a highly sensitive and small servo accelerometer can be provided.
In other words, by using a non-linear spring as the support spring that supports the pendulum, the influence of the tilt component in the acceleration data of the servo accelerometer becomes more significant than that of the linear spring, but the tilt component can be corrected, so measurement by tilt is possible. Since a reduction in accuracy can be prevented, a highly sensitive and small accelerometer can be provided.
Furthermore, even if the support spring undergoes creep deformation, the position of the fixed electrode can be moved correspondingly. Therefore, a servo-type accelerometer that can be made more sensitive and miniaturized using a non-linear spring is provided. be able to.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a servo accelerometer to which the present invention is applied will be described in detail with reference to FIGS.
[0014]
FIG. 1 is a diagram schematically showing a main configuration of a servo accelerometer.
A servo accelerometer 10 shown in FIG. 1 includes a drive unit 2, a pendulum 3, a displacement detection unit 4, a servo amplifier 5, a tilt measurement unit 6, an acceleration correction unit 7, a movement inside a main body case 1. A mechanism unit 8, a movement control unit 9, a signal output unit 11, and the like are provided.
[0015]
The drive unit 2 includes a magnet (permanent magnet) 2a fixed to the main body case 1 and a drive coil 2b wound around a foot 31 of a pendulum 3 inserted into a recess of the magnet 2a. By passing a current through the coil 2b, an electromagnetic force that moves the pendulum 3 is generated.
[0016]
One end of the pendulum 3 is supported so as to be vertically movable by a support spring 3a fixed to the main body case 1 or the wall 1a.
The support spring 3a is composed of, for example, a non-linear diaphragm spring. Here, for example, as shown in FIG. 2, the non-linear diaphragm spring {circle around (1)} is compared with the linear spring {circle around (2)} having an equivalent spring constant in the region of static deflection caused by the load (W) of the pendulum 3. The amount of static deflection (x1) due to the load (W) of the pendulum 3 can be reduced.
[0017]
The displacement detection unit 4 includes a movable plate 4a attached to the upper end of the pendulum 3 functioning as a capacitor and a fixed plate 4b provided on the case body 1 side, and an electric capacity between the plates 4a and 4b. By measuring the amount of change, the displacement of the pendulum 3 is detected, and the detected displacement is output to the servo amplifier 5.
[0018]
The servo amplifier 5 receives the output from the displacement detection unit 4 and controls the amount of current output to the drive coil 2b so that the drive unit 2 and the displacement detection unit 4 are matched.
In the above configuration, when acceleration is applied to the pendulum 3 and the pendulum 3 deviates from the neutral position, which is the zero position of the measurement point, the displacement detector 4 detects this deviation amount, and the servo amplifier 5 receives the signal and the servo amplifier 5 receives the signal. It operates so that a current flows through the drive coil 2 b of the drive unit 2.
[0019]
This current generates a force (electromagnetic force) in the opposite direction to the displacement of the pendulum 3 and acts to return the pendulum 3 to the neutral position. Since this electromagnetic force balances with the acceleration that caused the displacement of the pendulum 3, the acceleration applied to the pendulum 3 can be detected by measuring this current.
[0020]
The inclination measuring unit 6 includes a main body 61 attached to the inside of the main body case 1 and a pendulum rotation that rotates a horizontal pendulum 62 in directions perpendicular to each other (for example, the north-south direction and the east-west direction) at the inner upper end of the body 61. A moving part 63 is provided.
The pendulum rotation unit 63 is supported on the first shaft 63a fixed to the inside of the main body 61 and the first shaft 63a so that the upper portion thereof is rotatable about the axis of the first shaft 63a as a fulcrum. A rotating member 64, and a second shaft (not shown) provided below the rotating member 64 and spaced from the first shaft 63a and orthogonal to the first shaft 63a in plan view; The rotating member 64 is supported on the first shaft 63a by a cross spring (not shown).
[0021]
On the second shaft (not shown), the upper end of the horizontal pendulum 62 is supported with the axis of the second shaft (not shown) as a fulcrum, and is supported by a cross spring 65.
When the main body 61 is inclined in the direction centered on the first shaft 63a by the pendulum rotating portion 63, the horizontal pendulum 62 is inclined about the first shaft 63a, and the main body 61 is When tilted in the direction centered on the second axis (not shown), the horizontal pendulum 62 tilts about the second axis (not shown) as the rotating member 64 tilts.
[0022]
Further, opposite magnetic poles 66 and 66 each including a pole piece 66a are mounted on both sides of the horizontal pendulum 62 so as to surround the pole pieces 66a and 66a of the opposite magnetic poles 66 and 66 so as to cross the magnetic flux between the magnetic poles. Electromagnetic coils 67 and 67 projecting from the inner wall of the main body 61 are provided.
The electromagnetic coils 67 and 67 and the opposing magnetic poles 66 and 66 constitute a force motor (not shown) corresponding to the swinging of the horizontal pendulum 62 in the direction of the first shaft 63a. A force motor (not shown) corresponding to the swing in the direction of the shaft 63b is also provided.
[0023]
Further, a displacement detecting capacitor C is constituted by a protrusion 62a of the horizontal pendulum 62, a pair of east-west electrodes 68 and 68, and a pair of north-south electrodes (not shown) disposed so as to sandwich the protrusion 62a. In accordance with the change in the electric capacity of the capacitor C, the displacement of the protrusion 62a due to the horizontal pendulum 62 swinging back and forth and back and forth is detected.
Then, when the horizontal pendulum 62 is tilted, a control unit 69 for causing a current to flow through the electromagnetic coils 67 and 67 of the force motor so as to cancel the displacement of the horizontal pendulum 62 detected by the capacitor C. There is provided an inclination calculation unit 70 for obtaining an inclination angle based on the intensity of the current passed through the electromagnetic coils 67 and 67.
[0024]
The tilt calculation unit 70 calculates the tilt angle based on the voltage obtained via an electric resistor (not shown) provided in the inside based on the strength of the current, and outputs the calculated tilt angle to the acceleration correction unit 7.
The acceleration correction unit 7 corrects the acceleration calculated from the value of the current flowing through the drive coil 2b based on the inclination angle data calculated by the inclination calculation unit 70.
[0025]
Specifically, when the main body case 1 is inclined from the vertical direction by an angle θ, the load W (N) of the pendulum 3 is
[Expression 1]

become. Here, m: pendulum mass (kg), g: gravitational acceleration (m / s ² ), and θ: inclination angle.
The natural frequency fn (Hz) of the pendulum system determined by the support spring 3a and the pendulum mass m is
[Expression 2]

become. Here, k: spring constant (N / m).
[0026]
Accordingly, since the natural frequency fn of the pendulum system changes depending on the inclination of the pendulum, the measured acceleration value also changes. However, since the inclination angle calculated by the inclination calculating unit 70 is corrected, more accurate. Acceleration can be calculated.
[0027]
The moving mechanism unit 8 moves the fixed electrode 4b in the vertical direction. For example, one end of the moving mechanism unit 8 is fixed to the upper surface of the fixed electrode 4b so as to be rotatable about the shaft, The screw hole 82 is provided to be screwed with the screw shaft 81, and the motor 83 rotates the screw shaft 81. When the motor 83 is driven, the screw shaft 81 is rotated, and the fixed electrode 4b can be moved up and down.
[0028]
The movement control unit 9 receives the value of the current flowing through the drive coil 2b detected when the pendulum mass is in the neutral position, and when the input current value becomes larger than a predetermined value, the movement control unit 9 includes the motor 83 of the movement mechanism unit 8. To move the fixed electrode 4b by a predetermined amount (for example, a position where the current value from the drive coil 2b becomes zero).
That is, when the support spring 3a undergoes creep deformation, the static deflection position of the support spring 3a is lowered, but the servo amplifier 5 and the drive unit 2 attempt to return the support spring 3a to the original neutral position, so that current is driven. It flows to the coil 2b. When the current value exceeds a predetermined value, the movement control unit 9 drives the motor 83 of the movement mechanism unit 8 to move the fixed electrode 4b to change the neutral position.
As a result, even if the support spring 3a is creep-deformed, the position of the fixed electrode 4b can be moved correspondingly, and a servo type that can be made more sensitive and miniaturized using a non-linear spring. An accelerometer 10 can be provided.
[0029]
The signal output unit 11 outputs a signal to a recording unit (not shown) at the start and end of movement when the fixed electrode 4b is moved under the control of the movement control unit 9.
The recording unit (not shown) stores the signal output from the signal output unit 11 in association with the acceleration data.
[0030]
Next, the tilt correction operation in the servo-type accelerometer 10 having the above configuration will be described.
First, when the horizontal pendulum 62 attached to the main body is displaced from the neutral position, the inclination measuring unit 6 causes a current to flow through a force coil (not shown) so as to return to the center position. A tilt angle is calculated by the tilt calculation unit 70 from the current value flowing through the force coil (not shown), and the calculated tilt angle is output to the acceleration correction unit 7. The acceleration correction unit 7 calculates the acceleration by correcting the input tilt angle.
[0031]
Next, the neutral position correction operation of the movable plate 4a in the servo-type accelerometer 10 having the above configuration will be described.
First, the movement control unit 7 determines whether or not the value of the current flowing through the drive coil 2b exceeds a predetermined value when the pendulum 3 is positioned at the static deflection position. At the same time as outputting the drive signal to 63, the signal output unit 11 is caused to output a movement start signal. Then, the motor 63 is driven to rotate, the screw shaft 61 rotates, and the fixed electrode 4b moves downward. As the fixed electrode 4b moves, the neutral position of the movable electrode plate 4a also moves downward, and the value of the current flowing through the drive coil 2b decreases. When the current value becomes a predetermined value, the movement control unit 7 outputs a drive stop signal to the motor 63 of the movement mechanism unit 6 and simultaneously causes the signal output unit 11 to output a movement end signal.
[0032]
According to the servo-type accelerometer 10 according to the present invention described above, the tilt measuring unit 6 measures the tilt angle of the main body case 1, and the acceleration applied to the pendulum 3 is corrected based on the measured tilt angle. Therefore, the influence of the gradient component can be eliminated from the current flowing through the drive coil 2b, and the acceleration with higher accuracy can be measured.
[0033]
Further, by using a non-linear spring as the support spring 3a, the amount of static deflection can be reduced even with a low spring constant, and a highly sensitive and small servo accelerometer can be provided.
Here, since the support spring 3a that supports the pendulum 3 is a non-linear spring, the influence of the inclination component in the acceleration data of the servo accelerometer 10 becomes more significant than that of the linear spring, but the inclination component can be corrected. Since a decrease in measurement accuracy due to tilt can be prevented, a highly sensitive and small accelerometer can be provided.
[0034]
Note that the servo-type accelerometer 10 described above is not limited to the one having the above-described configuration, and may be appropriately changed within a range in which the same function and effect are obtained.
The support spring 3a may be a linear spring instead of a non-linear spring.
The moving mechanism unit 8 is not limited to moving the fixed electrode plate 4b by driving the screw shaft 81. For example, the moving mechanism unit 8 may be moved by a lift mechanism or any mechanism that can move the fixed electrode plate 4b with high accuracy. It may be something like this.
[0035]
【The invention's effect】
According to the first aspect of the present invention, since the inclination angle of the main body case is measured by the inclination measuring unit and the acceleration applied to the pendulum is corrected based on the measured inclination angle, the current flowing through the drive coil is corrected. Thus, the influence of the tilt component can be eliminated, and the acceleration with higher accuracy can be measured.
Further, by using a non-linear spring, the amount of static deflection can be reduced even with a low spring constant, and a highly sensitive and small servo accelerometer can be provided.
In other words, by using a non-linear spring as the support spring that supports the pendulum, the influence of the tilt component in the acceleration data of the servo accelerometer becomes more significant than that of the linear spring, but the tilt component can be corrected, so measurement by tilt is possible. Since a reduction in accuracy can be prevented, a highly sensitive and small accelerometer can be provided.
Furthermore, even if the support spring undergoes creep deformation, the position of the fixed electrode can be moved correspondingly. Therefore, a servo-type accelerometer that can be made more sensitive and miniaturized using a non-linear spring is provided. be able to.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a cross-sectional view and a block diagram of a main configuration of a servo accelerometer according to the present invention.
FIG. 2 is a diagram for explaining spring characteristics of a linear spring and a nonlinear spring.
FIG. 3 is a diagram schematically showing a cross-sectional view and a wiring diagram of a conventional servo-type accelerometer.
[Explanation of symbols]
1 Body case 2 Drive unit (drive control unit)
2b Drive coil 3 Pendulum 3a Support spring 4 Displacement detection unit 4a Movable plate 4b Fixed plate 5 Servo amplifier (drive control unit)
6 Inclination Measurement Unit 7 Acceleration Correction Unit 10 Servo Accelerometer 61 Screw Shaft 62 Screw Hole 63 Motor

Claims (1)

A pendulum supported by a support spring in the main body case so as to be movable up and down, and a displacement from a neutral position of the pendulum are statically moved between a fixed electrode provided on the main body case and a movable electrode provided on the pendulum. Based on the displacement detection unit detected by the capacitance change amount and the capacitance change amount detected by the displacement detection unit, a current is passed through the drive coil that moves the pendulum to return the pendulum to the neutral position. A servo type accelerometer, comprising: a drive control unit; and measuring an acceleration applied to the pendulum by a current value passed through the drive coil.
A moving mechanism for moving the fixed electrode up and down by driving a motor;
When the drive control unit applies a current to the drive coil to return the pendulum to the neutral position, the current value supplied to the drive coil detected at the neutral position is greater than a predetermined value. In addition, a movement control unit that controls to move the fixed electrode to a position where the current value from the driving coil becomes zero by driving the motor of the moving mechanism unit;
An inclination measuring unit provided in the main body case for measuring an inclination angle of the main body case;
An acceleration correction unit that corrects the acceleration of the pendulum based on the inclination angle measured by the inclination measurement unit;
And a servo-type accelerometer , wherein the support spring is a non-linear spring .

Images