JP2004309357A - Drag calibration method in magnetic suspension and balance system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drag calibration method in a simple magnetic suspension and balance system by acquiring a force in the direction of an air current flow equivalent to a drag due to air current using the load and the pitch angle of a wind tunnel model which can be measured. <P>SOLUTION: The weight mg of the wind tunnel model 1 and the minute pitch angle θ around the reference pitch angle θ0 (may be zero) of the wind tunnel model 1 to the direction of the air current when the wind tunnel model 1 is magnetically suspended by the magnetic suspension and balance system can be measured. The same situation is generated as the drag as air force acted on the wind tunnel model 1 by changing the pitch angle posture of the wind tunnel model 1. The correspondence relationship between the drag and drag coil current can be calibrated by measuring drag coil current in the state of balance. The drag calibration can be simply and efficiently executed in the viewpoint of time or cost without needing complicated works such as the assembly, the adjustment, the preparation and the weight exchange of an apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１３】
この磁力支持天秤装置における抗力較正方法によれば、風洞模型の重さｍｇは、磁力支持天秤装置外において十分高い精度で測定可能であり、また、重力のみが作用している風洞模型を磁力支持天秤装置で釣合い状態に磁力支持したときの気流の流れ方向に対する風洞模型の基準ピッチ角θ_０ 、及び基準ピッチ角θ_０ の周りの微小ピッチ角θも、風洞模型が磁力支持天秤装置内に置かれているとしても、光学的に十分な精度で測定可能である。従って、風洞模型の姿勢を変更するだけで、大きさが分かった異なる抗力が風洞模型に作用したのと同じ状況が生じ、釣合い状態において、上記式で定められる力Ｆｄを試験時に風洞模型に作用する空気力の一つである抗力に相当する力であると見なすことができ、そのときの抗力コイル電流を計測することにより、抗力と前記電流との対応関係を較正することが可能になる。
【００１４】
この磁力支持天秤装置における抗力較正方法において、前記基準ピッチ角θ_０ が零であるとき、下式で定められる力Ｆｄ’を前記風洞模型に作用する前記抗力に相当する力であると見なすことを特徴としている。
【数４】

この抗力較正方法によれば、風洞模型が飛行機等の飛翔体であるときに最も普通に採り得る姿勢の近傍である基準ピッチ角θ_０ が零である状態に対して、試験時に風洞模型に空気力の一つとして作用する抗力に相当する力を、より簡単な式で得ることが可能である。
【００１５】
【発明の実施の形態】
以下、図面を参照して、この発明による磁力支持天秤装置における抗力較正方法の実施の態様を説明する。図１はこの発明による磁力支持天秤装置における抗力較正方法における座標と関連する物理量の概要を示す説明図である。
【００１６】
図１に示すように、風洞模型１の重心を原点とする直交座標が縦面内に定められ、ｚ軸を鉛直上方、ｘ軸を風洞における気流の流れ方向に、またｙ軸はこれら両軸と右手系を成す方向に設定される。ｘ軸は、基準ピッチ角θ_０ が零であるとき、模型長軸方向と一致する方向に取るのが好ましい。ここで用いる物理量等の記号の定義は、以下のとおりであり、括弧内はその単位である。
Ｆ ： 風洞模型１に働く力（Ｎ）
Ｍ ： 風洞模型１に内蔵される磁石２の磁気モーメント（Ｗｂｍ）
Ｍ_０ ： 風洞模型１に内蔵される磁石２の磁気モーメント（Ｗｂｍ）
Ｈ ： 磁力支持天秤装置が生じる磁場の強さ（ＡＴ／ｍ）
ｍ ： 風洞模型１の質量
θ ： 風洞模型１のピッチ角（ｒａｄ）
なお、Ｍ，Ｆ，Ｈはベクトル量、Ｍ_０ ，ｍ，θはスカラー量であり、磁力支持天秤装置２０は図３に示すのと同じ構造のものでよく再度の説明を省略する。
【００１７】
上記の物理量の間には、以下の関係式がある。
【数５】

即ち、Ｍｙが零であるので、気流の流れに沿った縦面を横切る磁気モーメント成分はない。式（１）に上記のＭを当てはめると次のようになる。
【数６】

【数７】

【００１８】
ここで、電流は測定部内部を流れていないので、次の式（４）の関係がある。
【数８】

磁気支持天秤装置２０では、浮揚させる風洞模型１は略水平の姿勢を有しており、基準ピッチ角θ_０ は零の近傍にある。
また、磁場については、多くの場合、風洞模型１を浮揚させるために、コイル系２１，２２，３１，３２を｜∂Ｈｚ／∂ｘ｜が大きな値となるように駆動している。即ち、
【数９】

更に、抗力は、多くの風洞実験では、他の空力荷重の３つの方向成分中、最も小さい値であり、それゆえ、較正の範囲は狭い。抗力は、本磁力支持天秤装置でも最大で風洞模型１の重さｍｇの５分の１であるので、ここでは、実用上の抗力較正範囲として模型模型１の重さｍｇの１０分の１とする。
【００１９】
風洞模型１について、鉛直方向の力の釣り合い、及びピッチ角θが小さい値であること、更に式（３）は、式（５）から、第２項が第１項に比べて十分小さく無視可能であるので、次のようになる。
【数１０】

【００２０】
一方、風洞模型１は静止流れの中に置かれており、流れがあるとしたときの流れ方向（ｘ軸方向、図５でＵ∞で示す）については風洞模型１に働く力は釣り合っているから、式（２）自体は次のように表され、また式（４）及び式（６）を用いて更に変形すれば、式（７）が得られる。
【数１１】

【００２１】
式（７）の左辺第２項は、風洞模型１の重さｍｇとピッチ角θの正接の積である。しかも、重さｍｇについては磁力支持天秤装置２０外で測定可能であり、またピッチ角θについても、風洞模型１が磁力支持天秤装置２０で浮揚支持されていても光学的に測定可能である。即ち、風洞模型１が磁気力で浮揚支持されて釣合い状態にあるときには、磁気の作用に基づく流れ方向（ｘ軸方向）の力の成分であるＭ_０ ・ｃｏｓθ・（∂Ｈｘ／∂ｘ）を、風洞模型１の測定可能な重さｍｇとピッチ角θから求めることができる。即ち、ピッチ角θの変化が上記の狭い範囲内で抑まるように抗力コイル電流Ｉｘを変更していくとき、釣合い状態では、抗力コイル（図５の抗力コイル３１，３２を参照）の磁気作用によって生じる力であるＭ_０ ・ｃｏｓθ・（∂Ｈｘ／∂ｘ）の値はｍｇ・ｔａｎθに等しく、ｍｇ・ｔａｎθは釣合い状態にあるときの流れ方向（ｘ軸方向）力、即ち試験時に風洞模型１に作用する抗力に相当する力と見なすことができる。そのようにして得られた釣合い状態において、抗力コイル電流Ｉｘの値と抗力（ｍｇ・ｔａｎθ）の値との組データは、磁石劣化等の場合には、抗力較正となり、即ち古い対応関係に取って代わる新しい対応関係を定めることができる。
【００２２】
ピッチ角θが零の近傍でない場合には、ピッチ角は零でない有意の値の基準ピッチ角θ_０ の周りに微小ピッチ角θで変動しているとして、次のように、ｘ軸方向の荷重を近似することができる。即ち、式（６）に対応する式として、
【数１２】

式（２）に対応する式として、
【数１３】

式（８）と式（９）から式（７）に対応する式として、式（１０）が得られる。
【数１４】

ここで、θは微小であるとすると、
ｃｏｓ（θ_０ ＋θ）≒ｃｏｓθ_０ ・ｃｏｓθであるので、式（１０）は次の式（１１）となる。
【数１５】

【００２３】
式（１１）において、その狭い範囲内でピッチ角の変動分θ内で、抗力コイル電流Ｉｘを変更して風洞模型１を釣合い状態にもたらすと、抗力コイル３１，３２の磁気作用によって生じさせた力であるＭ_０ ・ｃｏｓθ_０ ・（∂Ｈｘ／∂ｘ）の値は−ｍｇ・ｔａｎ（θ_０ ＋θ）／ｃｏｓθに等しい。即ち、ピッチ角の変動分θが小さい場合に、流れ方向（ｘ軸方向）に風洞模型１に働く力を釣り合わせたときには、計測可能な値から求まるｍｇ・ｔａｎ（θ_０ ＋θ）／ｃｏｓθは、釣合い状態にあるときの流れ方向（ｘ軸方向）力、即ち試験時に風洞模型１に空気力の一つとして作用する抗力に相当する力であると見なすことができる。そうした釣合い状態から得られた抗力コイル電流Ｉｘの値と、抗力（ｍｇ・ｔａｎ（θ_０ ＋θ）／ｃｏｓθ）の値との組データは、磁石劣化等の場合には、新しい対応関係を定める抗力較正を提供することができる。
【００２４】
図２（Ａ）は重りを用いて行う抗力較正の結果を示す図であり、図２（Ｂ）は模型の傾斜を利用して行う抗力較正の結果を示す図である。両図とも、横軸は抗力コイル電流Ｉｘ（アンペアＡ）、縦軸は抗力Ｆｄ（ニュートンＮ）であり、大きい抗力が生じているときには、当然ながら抗力コイル電流Ｉｘが大きくなっている。図中、Ｒ^２ は測定値の分散に対応する値であり、値１が分散ゼロに対応する。重りを用いた較正において図２（Ａ）に示すような抗力コイル電流Ｉｘと抗力Ｆｄとの対応関係に現れる直線性が、模型の傾きに基づいた図２（Ｂ）に示す抗力Ｆｄの較正においても良く得られている。両者の抗力コイル電流Ｉｘと抗力Ｆｄとの線型的な対応関係において、傾き及び切片の各値において良く近似しており、模型の傾きを利用した対応関係によって抗力較正を行うことの有用性を確認することができる。
【００２５】
【発明の効果】
以上説明したように、この発明による磁力支持天秤装置における抗力較正方法によれば、風洞模型の重さについては、磁力支持天秤装置外において十分高い精度で測定可能であり、また、重力のみが作用している風洞模型を磁力支持天秤装置で釣合い状態に磁力支持したときの気流の流れ方向に対する風洞模型の基準ピッチ角θ_０ 、及び基準ピッチ角θ_０ の周りの微小ピッチ角θも、光学的に十分な精度で測定可能である。風洞模型を重りで引っ張るということをしなくても、風洞模型のピッチ角姿勢を変更するだけで、抗力に相当する力と見なすことができる大きさが既知の力が風洞模型に作用したのと同じ状況が生じる。その釣合い状態を維持するために抗力コイルに流される抗力コイル電流を計測することにより、両者間に新しい対応関係が定められ、例えば磁石劣化に起因した抗力と抗力コイル電流との間でずれを生じた対応関係を較正することができる。従って、重りを用いた抗力較正では避けることができなかった、機器の組立、調整、準備、重りを交換等の煩雑な作業も必要なくなり、時間やコストの観点で簡便で効率的な抗力較正を行うことができる。
【図面の簡単な説明】
【図１】この発明による磁力支持天秤装置における抗力較正方法における座標と関連する物理量の概要を示す説明図である。
【図２】この発明による磁力支持天秤装置における抗力較正方法の有用性を示す図である。
【図３】この発明による磁力支持用風洞模型が用いられる磁力支持天秤装置の概略図である。
【図４】磁力支持天秤装置の概念図である。
【図５】磁力支持天秤装置における従来の抗力較正方法を示す概略図である。
【符号の説明】
１ 風洞模型
２ 磁石
２０ 磁力支持天秤装置
３１，３２抗力コイル
Ｉｘ 抗力コイル電流
ｍｇ 風洞模型の重さ
θ_０ 風洞模型の基準ピッチ角
θ 微小ピッチ角
Ｄ 風洞模型に作用する抗力
Ｆｄ，Ｆｄ’ 風洞模型に作用する抗力相当力[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drag calibration method for a magnetic force supporting balance device that magnetically supports a wind tunnel model having a magnet therein in the wind tunnel.
[0002]
[Prior art]
Conventionally, in order to obtain the aerodynamic characteristics of an object with a model, it has been common practice to support the model with a support at the measurement part of the wind tunnel equipment, but the support itself affects the air flow on the model surface Therefore, the test results cannot be directly used as the aerodynamic characteristics of the model. Therefore, it has been proposed to support the model by magnetic force in a wind tunnel test. Since the support is unnecessary by magnetically supporting the model, the aerodynamic influence around the model due to the presence of the support can be eliminated.
[0003]
A magnetic force supporting balance device that magnetically supports a model is a method for generating a magnetic force that interacts with a magnet provided inside the model in a wind tunnel test by causing airflow flowing around the model to generate aerodynamic force such as a drag acting on the model. This is a device that measures the magnitude of the current flowing through the provided coil. By examining the relationship between the aerodynamic force and the magnitude of the coil current and preparing a correspondence such as a map, a function, and a table in advance, and applying the correspondence to the measured value of the coil current, a drag acting on the model can be obtained. You can know the aerodynamic force.
[0004]
With reference to FIG. 3 and FIG. 4, an outline of the magnetic force supporting wind tunnel and the magnetic force supporting balance device therein will be described. The magnetic force support balance device 20 is a device that supports the wind tunnel model 1 in the airflow by magnetic force in order to avoid interference between the support device accompanying the model support and the airflow, and can realize a wind tunnel test without support interference. . The wind tunnel model 1 is mounted with a magnetized material, a coil such as a superconducting coil that keeps flowing current, or a magnet body made of a permanent magnet or the like. A magnetic force is generated in the magnet body of the wind tunnel model 1 by a magnetic action with an external magnetic field generated by passing an electric current through a coil arranged around a measurement portion of the wind tunnel, and the wind tunnel model 1 is magnetically levitated and supported. Can be. The external magnetic field is generated by the two magnetic circuits 21 and 22 including the coils 23 to 26 and the coils 27 to 30 and the air core coils 31 and 32 outside the magnetic circuits 21 and 22, and the current flowing through each coil of the magnetic circuits 21 and 22 is generated. , The strength and direction of the magnetic field in the yz plane in the magnetic circuits 21 and 22 and the rate of change thereof in the x-axis direction can be continuously changed. Further, the rate of change of the intensity of the magnetic field in the x-axis direction as viewed in the x-axis direction can be controlled by adjusting the current flowing through the air-core coils 31 and 32, so that control of five axes is possible. That is, the magnetic circuits 21 and 22 function as lift coils that provide a magnetic force that opposes the lift and the pitching moment acting on the wind tunnel model 1, and the air-core coils 31 and 32 function as a magnet that opposes the drag acting on the wind tunnel model 1. It functions as a drag coil that gives force.
[0005]
In the wind tunnel, in addition to the wind tunnel model 1 and the coils 23 to 32, a power supply system for driving each coil, a measurement system for measuring the position and orientation of the wind tunnel model 1 (a measuring device 36 shown in FIG. 1), a wind tunnel model 1 A control system for controlling the position and posture of the camera is incorporated. As shown in FIG. 4, measurement data on the position and orientation of the wind tunnel model 1 detected by the camera 33 serving as a measurement system is transmitted to a computer 34 such as a personal computer, and the calculation result of the computer 34 is amplified by an amplifier 35. , A controlled drive current is passed through each of the coils 23 to 32.
[0006]
Incidentally, as one of the important test items of the wind tunnel test, there is a drag measurement for measuring a resistance force acting on a wind tunnel model in a flow direction of an airflow. If the drag acting on an object can be reduced even slightly when moving in a fluid, the energy required for the movement can be improved to a considerable extent and contribute to energy saving.Therefore, it is necessary to measure the drag as accurately as possible. Have been. However, since the strength of the magnet provided in the model deteriorates to a considerable extent due to aging, the correspondence obtained at the beginning may not always coincide with the actual correspondence over time. In the drag measurement as well, the correspondence between the strength of the magnet and the current flowing through the coil differs due to aging, so it is necessary to calibrate the drag of the magnetic force supporting balance device.
[0007]
Drag calibration of a magnetically supported balance device usually involves placing a wind tunnel model in a wind tunnel where the flow is stopped, and adding the drag that would occur in the direction of the air flow as an external force in some way if the air flow was to flow. This can be achieved by measuring the value of the drag coil current flowing through the drag coil that generates a magnetic force corresponding to this force, and obtaining the correspondence between the applied force and the drag coil current value. Based on this correspondence, the evaluation of the drag applied to the model supporting the magnetic force in the wind tunnel test actually performed by flowing the air current by measuring the value of the drag coil current flowing through the drag coil in a balanced state Can be.
[0008]
A schematic of the longitudinal three-component calibration method, including drag calibration, is shown in FIG. While the wind tunnel model 1 is magnetically supported by the magnetic force support balance device 20 in the wind tunnel measuring unit, a force or moment corresponding to the drag D, the lift L, and the pitching moment m is added by a weight, and the corresponding coil current is measured. You. The gravitational force Md · g (corresponding to the drag force D, g is the same hereinafter) acting on the weight of the mass Md is proportional to the drag coil current Ix flowing through the drag coil 31. The lift L is in proportion to the gravity Ml · g acting on the weight of the mass Ml, and is proportional to the sum of the lift coil current Iz1 flowing through the lift coil 21 and the lift coil current Iz2 flowing through the lift coil 22. Is the product of gravity Mm · g acting on the weight of mass Mm and arm length s / 2, and is proportional to the difference between lift coil current Iz1 flowing through lift coil 21 and lift coil current Iz2 flowing through lift coil 22. are doing.
[0009]
In the drag calibration, to apply a known force, as shown in FIG. 5, complicated operations such as assembly, adjustment, and preparation of equipment for applying such force to the wind tunnel model 1 are required. Further, in order to change the force corresponding to the drag, the weights Md, Ml, and Mm are exchanged, and after the exchange, it is necessary to rebalance and adjust again, and it is necessary to wait until the movement of the wind tunnel model 1 stops. . For this reason, frequent drag calibration is actually difficult, and there is a possibility that the interval between the calibration periods is widened and the drag measurement accuracy itself is adversely affected.
[0010]
[Problems to be solved by the invention]
Therefore, in the drag calibration of the magnetic force supporting balance device, paying attention to the fact that the drag is relatively smaller than other aerodynamic forces acting on the model by the airflow, we obtain a force in the airflow direction equivalent to the drag, regardless of the weight There are issues to be solved in making it possible.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to eliminate the complicated work of assembling, adjusting, preparing, and replacing a weight, which could not be avoided when using a weight, and to simply and efficiently perform a drag calibration in terms of time and cost. Is to provide a drag calibration method in a magnetically supported balance device which enables to carry out the following.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a drag calibration method in a magnetic force supporting balance device according to the present invention is directed to a magnetic force supporting balance having a drag coil that generates a magnetic force by energizing to balance a drag acting on a wind tunnel model by an air flow. With respect to the device, the magnitude of the force acting on the wind tunnel model as a force corresponding to the drag is obtained by calculating a current flowing through the drag coil in order to balance the force with a known force, so that the correspondence between the drag and the current is determined. In the drag calibration method to calibrate, the weight of the wind tunnel model is mg, and the reference pitch angle of the wind tunnel model when the wind tunnel model on which only gravity acts is magnetically supported in a balanced state by the magnetic force supporting balance device and each theta ₀ minute pitch angle around the reference pitch _angle, when a theta, a force Fd defined by the following formula in the wind tunnel It is characterized in that considered as the a force corresponding to the drag that.
[Equation 3]

[0013]
According to the drag calibration method in the magnetic force supporting balance device, the weight mg of the wind tunnel model can be measured with sufficiently high accuracy outside the magnetic force supporting balance device, and the wind tunnel model in which only gravity acts is magnetically supported. The reference pitch angle θ ₀ of the wind tunnel model with respect to the flow direction of the air flow when the balance device is magnetically supported in a balanced state, and the minute pitch angle θ around the reference pitch angle θ ₀ are also set in the magnetic force support balance device by the wind tunnel model. Even if it is, it can be measured optically with sufficient accuracy. Therefore, just by changing the attitude of the wind tunnel model, the same situation occurs in which a different drag of a known magnitude acts on the wind tunnel model. In a balanced state, the force Fd determined by the above equation acts on the wind tunnel model during the test. It can be regarded as a force corresponding to the drag which is one of the aerodynamic forces generated, and by measuring the drag coil current at that time, the correspondence between the drag and the current can be calibrated.
[0014]
In the drag calibration method in the magnetic force supporting balance device, when the reference pitch angle θ ₀ is zero, it is assumed that a force Fd ′ defined by the following equation is regarded as a force corresponding to the drag acting on the wind tunnel model. Features.
(Equation 4)

According to this drag calibration method, when the reference pitch angle θ _0, which is in the vicinity of the attitude that can be taken most commonly when the wind tunnel model is a flying object such as an airplane, is zero, the wind tunnel model applies air to the wind tunnel model during the test. A force corresponding to the drag acting as one of the forces can be obtained with a simpler formula.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a drag calibration method in a magnetically supported balance device according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of coordinates and related physical quantities in a drag calibration method in a magnetic force supporting balance device according to the present invention.
[0016]
As shown in FIG. 1, orthogonal coordinates having the origin at the center of gravity of the wind tunnel model 1 are defined in the vertical plane, the z axis is vertically upward, the x axis is in the flow direction of the air flow in the wind tunnel, and the y axis is both axes. And the right hand direction. When the reference pitch angle θ ₀ is zero, it is preferable to take the x-axis in a direction coinciding with the longitudinal direction of the model. The definitions of symbols such as physical quantities used here are as follows, and the unit in parentheses is the unit.
F: Force acting on wind tunnel model 1 (N)
M: magnetic moment (Wbm) of magnet 2 built in wind tunnel model 1
M ₀ : Magnetic moment (Wbm) of magnet 2 built in wind tunnel model 1
H: magnetic field strength (AT / m) generated by the magnetic force supporting balance device
m: mass of wind tunnel model 1 θ: pitch angle of wind tunnel model 1 (rad)
Note that M, F, and H are vector quantities, and M ₀ , m, and θ are scalar quantities, and the magnetic force supporting balance device 20 has the same structure as that shown in FIG. 3 and will not be described again.
[0017]
There is the following relational expression between the above physical quantities.
(Equation 5)

That is, since My is zero, there is no magnetic moment component crossing the vertical surface along the flow of the airflow. When the above M is applied to the equation (1), the following is obtained.
(Equation 6)

(Equation 7)

[0018]
Here, since the current does not flow through the inside of the measurement unit, the following equation (4) is established.
(Equation 8)

In the magnetic suspension and balance system 20, wind tunnel 1 levitate has a substantially horizontal orientation, the reference pitch angle theta ₀ is in the vicinity of zero.
Regarding the magnetic field, in many cases, in order to levitate the wind tunnel model 1, the coil systems 21, 22, 31, and 32 are driven so that | ∂Hz / ∂x | has a large value. That is,
(Equation 9)

In addition, drag is the smallest of the three directional components of other aerodynamic loads in many wind tunnel experiments, and therefore has a narrow range of calibration. Since the drag force is at most 1/5 of the weight mg of the wind tunnel model 1 in this magnetic force supporting balance device, here, the drag calibration range for practical use is 1/10 of the weight mg of the model model 1. I do.
[0019]
Regarding the wind tunnel model 1, the balance of the vertical force and the pitch angle θ are small values. Further, in the equation (3), from the equation (5), the second term is sufficiently smaller than the first term and can be ignored. Therefore, it becomes as follows.
(Equation 10)

[0020]
On the other hand, the wind tunnel model 1 is placed in a stationary flow, and the forces acting on the wind tunnel model 1 are balanced in the flow direction (x-axis direction, indicated by U in FIG. 5) when there is a flow. Therefore, equation (2) itself is expressed as follows, and equation (7) can be obtained by further modifying equation (4) and equation (6).
(Equation 11)

[0021]
The second term on the left side of Expression (7) is the product of the tangent of the weight mg of the wind tunnel model 1 and the pitch angle θ. In addition, the weight mg can be measured outside the magnetically supported balance device 20, and the pitch angle θ can be optically measured even if the wind tunnel model 1 is levitated and supported by the magnetically supported balance device 20. That is, when the wind tunnel model 1 is levitated and supported by the magnetic force and is in a balanced state, M ₀ · cos θ · (∂Hx / ∂x) which is a component of the force in the flow direction (x-axis direction) based on the action of magnetism is calculated. From the measurable weight mg of the wind tunnel model 1 and the pitch angle θ. That is, when the drag coil current Ix is changed so that the change in the pitch angle θ is suppressed within the above narrow range, in a balanced state, the magnetic action of the drag coil (see the drag coils 31 and 32 in FIG. 5) is performed. equal to the value in mg · tan .theta force _M 0 · _cosθ · a resulting (∂Hx / ∂x) by the flow direction (x-axis direction) when mg · tan .theta are in a balanced state forces, ie wind tunnel during the test 1 can be regarded as a force corresponding to the drag acting on the first element. In the thus obtained balanced state, the set data of the value of the drag coil current Ix and the value of the drag (mg · tan θ) becomes drag calibration in the case of magnet deterioration or the like, that is, the old correspondence is taken. New correspondence relationships can be defined.
[0022]
If the pitch angle θ is not close to zero, it is assumed that the pitch angle fluctuates at a small pitch angle θ around the reference pitch angle θ ₀ of a significant value that is not zero, and the load in the x-axis direction is as follows. Can be approximated. That is, as an equation corresponding to equation (6),
(Equation 12)

As an equation corresponding to equation (2),
(Equation 13)

From Expressions (8) and (9), Expression (10) is obtained as an expression corresponding to Expression (7).
[Equation 14]

Here, if θ is very small,
Since cos (θ ₀ + θ) ≒ cos θ ₀ · cos θ, Expression (10) becomes Expression (11) below.
(Equation 15)

[0023]
In the equation (11), when the drag coil current Ix is changed to bring the wind tunnel model 1 into a balanced state within the pitch angle variation θ within the narrow range, the wind coil model 1 is generated by the magnetic action of the drag coils 31 and 32. The value of the force M ₀ · cos θ ₀ · (∂Hx / ∂x) is equal to -mg · tan (θ ₀ + θ) / cos θ. That is, when the variation θ of the pitch angle is small and the force acting on the wind tunnel model 1 in the flow direction (x-axis direction) is balanced, mg · tan (θ ₀ + θ) / cos θ obtained from a measurable value is It can be regarded as a force in the flow direction (x-axis direction) when in a balanced state, that is, a force corresponding to a drag acting as one of the pneumatic forces on the wind tunnel model 1 during the test. The set data of the value of the drag coil current Ix and the value of the drag (mg · tan (θ ₀ + θ) / cos θ) obtained from such a balanced state is a drag that determines a new correspondence in the case of magnet deterioration or the like. Calibration can be provided.
[0024]
FIG. 2A is a diagram illustrating a result of a drag calibration performed using a weight, and FIG. 2B is a diagram illustrating a result of a drag calibration performed using a tilt of a model. In both figures, the horizontal axis is the drag coil current Ix (ampere A), and the vertical axis is the drag Fd (Newton N). When a large drag is generated, the drag coil current Ix is naturally large. In the figure, R ² is a value corresponding to the measurement value dispersion, the value 1 corresponds to the dispersion zero. In the calibration using the weight, the linearity appearing in the correspondence between the drag coil current Ix and the drag Fd as shown in FIG. 2A is the result of the calibration of the drag Fd shown in FIG. 2B based on the inclination of the model. Has also been obtained well. In the linear correspondence between the drag coil current Ix and the drag Fd, both values of the slope and intercept are well approximated, confirming the usefulness of performing the drag calibration by the correspondence using the slope of the model. can do.
[0025]
【The invention's effect】
As described above, according to the drag calibration method in the magnetic force support balance device according to the present invention, the weight of the wind tunnel model can be measured with sufficiently high accuracy outside the magnetic force support balance device, and only gravity acts. The reference pitch angle θ ₀ of the wind tunnel model with respect to the flow direction of the air current when the wind tunnel model is magnetically supported in a balanced state by the magnetic force supporting balance device, and the minute pitch angle θ around the reference pitch angle θ ₀ are also optical. Can be measured with sufficient accuracy. Even if the wind tunnel model is not pulled by the weight, just by changing the pitch angle attitude of the wind tunnel model, the force whose magnitude can be regarded as the force equivalent to the drag applied to the wind tunnel model The same situation occurs. By measuring the drag coil current flowing through the drag coil to maintain the balanced state, a new correspondence is defined between the two, for example, a shift occurs between the drag due to magnet deterioration and the drag coil current. Can be calibrated. Therefore, complicated operations such as assembly, adjustment, preparation and replacement of weights, which cannot be avoided by drag calibration using weights, become unnecessary, and simple and efficient drag calibration can be performed in terms of time and cost. It can be carried out.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of coordinates and physical quantities in a drag calibration method in a magnetic force supporting balance device according to the present invention.
FIG. 2 is a diagram showing the usefulness of a drag calibration method in a magnetically supported balance device according to the present invention.
FIG. 3 is a schematic diagram of a magnetic force supporting balance device using the magnetic force supporting wind tunnel model according to the present invention.
FIG. 4 is a conceptual diagram of a magnetic force supporting balance device.
FIG. 5 is a schematic view showing a conventional drag calibration method in a magnetically supported balance device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wind tunnel model 2 Magnet 20 Magnetic support balance device 31, 32 Drag coil Ix Drag coil current mg Weight of wind tunnel model θ ₀ Reference pitch angle of wind tunnel model θ Small pitch angle D Drag Fd, Fd 'acting on wind tunnel model Wind tunnel model Drag equivalent force acting on

Claims (2)

Regarding a magnetic force supporting balance device provided with a drag coil that generates a magnetic force by energizing in order to balance the drag acting on the wind tunnel model by the airflow, the magnitude acting on the wind tunnel model as a force corresponding to the drag is known. In the drag calibration method of calibrating the correspondence between the drag and the current by obtaining the current flowing through the drag coil to balance the force of the wind, the weight of the wind tunnel model is set to mg, and only gravity acts. When the wind tunnel model is magnetically supported in a balanced state by the magnetic force supporting balance device, and the reference pitch angle of the wind tunnel model and the minute pitch angles around the reference pitch angle are θ ₀ and θ, respectively, Wherein the force Fd determined by the equation is regarded as a force corresponding to the drag acting on the wind tunnel model. Calibration method.

2. The magnetic force support according to claim 1, wherein when the reference pitch angle θ ₀ is zero, a force Fd ′ defined by the following equation is regarded as a force corresponding to the drag acting on the wind tunnel model. 3. Drag calibration method for a balance device.

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