CN104567653B - A kind of method of electric vortex sensor measuring many frameworks gondola inner frame angle - Google Patents

Abstract

A kind of method that the invention discloses electric vortex sensor measuring many frameworks gondola inner frame angle, comprises the following steps that and current vortex sensor and sensing steel disc is respectively arranged on the installation frame of inner frame to be measured and this inner frame；When inner frame to be measured rotates relative to its installation frame, current vortex sensor changes relative to the distance of sensing steel disc, the voltage signal V that current vortex sensor output is relevant to distance change；The voltage signal of current vortex sensor output, by filtering and analog digital conversion, calculates current vortex sensor and sensing steel disc distance h simultaneously according to the amplification coefficient of the scale factor of current vortex sensor and analog digital conversion；Distance h according to current vortex sensor and sensing steel disc, calculates the angle between the installation frame of inner frame to be measured and this inner frame.The present invention can reduce volume and the weight of many frame hoistings cabin system, it is possible to reduces frictional force and is obtained in that high-precision angular surveying.

Description

Method for measuring angle of inner frame of multi-frame pod by using eddy current sensor

Technical Field

The invention relates to a method for measuring the angle of an inner frame of a multi-frame pod by using an eddy current sensor, belonging to the technical field of multi-frame pod control.

Background

The photoelectric pod keeps the internal platform stable in the motion process according to the speed stability principle, and information such as images, distances and the like of a target is acquired by utilizing loads (such as an optical camera, a thermal infrared imager, a laser range finder and the like) on the platform to complete the identification, tracking and positioning of the target. The method is widely applied to the fields of aerial photography, military reconnaissance, border patrol, search and rescue, safety law enforcement and the like according to the load allocation. The performance of the photoelectric pod is mainly reflected in the detection distance of infrared light and visible light and the distance measurement capability of a laser. These properties are determined by the stability accuracy of the photovoltaic bird, under the conditions satisfied by the load itself. At present, the stability precision of the foreign photoelectric pod can reach 3 micro-arcs (equivalent to that a target 1 kilometer away only shakes for 3 millimeters), and the corresponding distance measuring capacity can reach 30 kilometers. The stability precision of the domestic photoelectric pod is 25 micro-arcs, the distance measuring capability is 15 kilometers, and the difference is large.

The multi-frame photoelectric pod is a mainstream form of photoelectric pod equipment, and is stabilized by utilizing an inner layer of frame and an outer layer of frame on the same shaft: the outer frame resists wind resistance and primarily reduces vibration; the inner frame achieves higher stability accuracy. With the same outer frame, the stabilization accuracy of the inner frame determines the stabilization accuracy of the entire multi-frame photovoltaic pod. At present, the inner frames of the multi-frame photoelectric pod at home and abroad use encoders or rotary transformer devices to measure angles. First, the inner frame angle is small, typically less than ± 3 °. And the encoder or the rotary transformer are all full-circle measuring devices, so when the devices are used for measuring angles, the waste of volume, weight and measuring range is caused. Secondly, corresponding shaft end support is needed when the encoder and the rotary transformer are applied, friction can be introduced, and the friction is a main factor influencing the stability and the precision of the platform. At present, a method for measuring the angle of the inner frame of the multi-frame nacelle with high precision and capable of reducing friction force is urgently needed.

Disclosure of Invention

The invention solves the problems that: aiming at the defects of the prior art, the method for measuring the angle of the inner frame of the multi-frame pod by using the eddy current sensor is provided, and the high-precision angle measurement value of the multi-frame pod is obtained by adopting the eddy current sensor and accurate calculation in the inner frame of the multi-frame photoelectric pod.

The technical solution of the invention is as follows:

a method for measuring the angle of an inner frame of a multi-frame pod by using an eddy current sensor comprises the following steps:

respectively installing an eddy current sensor and an induction steel sheet on an inner frame to be detected and an installation frame of the inner frame;

when the inner frame to be measured rotates relative to the mounting frame, the distance between the eddy current sensor and the induction steel sheet changes, and the eddy current sensor outputs a voltage signal V related to the distance change;

the voltage signal output by the eddy current sensor is subjected to filtering and analog-to-digital conversion, and the distance h between the eddy current sensor and the induction steel sheet is calculated according to a scale factor of the eddy current sensor and an amplification factor of the analog-to-digital conversion;

and calculating the angle between the inner frame to be measured and the mounting frame of the inner frame according to the distance h between the eddy current sensor and the induction steel sheet.

The length of the installation position of the eddy current sensor from the axis of the inner frame to be measured is R₁Said R is₁Is composed ofWherein L is₁Is the measuring range of the current vortex sensor, theta is the angle range to be measured, and R₁On the premise of satisfying the inequality, R₁Should be as close as possible to

Calculating the distance between the eddy current sensor and the induction steel sheetWherein k is₁Indicating the scale factor of the eddy current sensor, n indicating the number of bits of the analog-to-digital conversion, η indicating the input voltage range of the analog-to-digital conversion.

The specific implementation mode of calculating the angle beta between the inner frame to be measured and the mounting frame of the inner frame according to the distance h between the eddy current sensor and the induction steel sheet is as follows:

(4a) calculating an included angle alpha between a straight line where the induction steel sheet is located and the axis of the inner frame to be detected and the steel sheet connecting line:

$\mathrm{\α}=\arcsin \left(\frac{0.5L_1+L_3}{R_1}\right)$

wherein L is₃Representing the minimum distance between the eddy current sensor and the induction steel sheet;

(4b) calculating an angle beta between the inner frame to be measured and the mounting frame of the inner frame by using the included angle alpha and the distance h obtained in the step (4 a):

$\mathrm{\β}=\mathrm{arc}\cos \left(\frac{\sqrt{1-c^2+2c\tan \mathrm{\α}}-c\tan \mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\β}}\right)$

wherein, $c=\frac{h\sqrt{1+{\tan }^2\mathrm{\α}}}{R_1}.$

the angle β between the mounting frame of the inner frame that awaits measuring and this inner frame, when measurement accuracy requires lowerly, can utilize simplified formula to calculate, simplified formula is:

the installation positions of the induction steel sheet and the eddy current sensor can be interchanged and are respectively installed on the installation frame of the inner frame to be tested and the installation frame of the inner frame to be tested ${\mathrm{\β}}_1=\arccos \left(\frac{\sqrt{1-{c_1}^2+2c_1\tan {\mathrm{\α}}_1}-c_1\tan {\mathrm{\α}}_1+{\tan }^2{\mathrm{\α}}_1}{1+{\tan }^2{\mathrm{\α}}_1}\right),$ α therein₁The included angle between the straight line where the eddy current sensor is located and the axis of the inner frame to be detected and the connecting line of the eddy current sensor is included;

compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts the eddy current sensor to measure the angle in the inner frame of the multi-frame photoelectric pod, and can obviously improve the measuring precision of the angle of the inner frame of the multi-frame pod compared with the means such as an encoder with the same size adopted in the prior art.

(2) Compared with the prior art, the adopted eddy current sensor does not need to be provided with a rotating shaft independently, so that the inter-shaft friction is reduced, the stability and the precision of the multi-frame photoelectric pod are improved, and the volume and the weight of the inner frame are reduced.

(3) According to the invention, the coordinate system of the eddy current sensor and the induction steel sheet is established, the position relation between the eddy current sensor and the induction steel sheet is solved by establishing the position mathematical model of the eddy current sensor and the induction steel sheet and strict data calculation, and then the angle of the inner frame is solved, so that the measurement precision of the angle of the inner frame is improved, and the performance of the multi-frame nacelle control system is improved.

Drawings

FIG. 1 is a schematic view of the eddy current sensor and induction steel sheet composition of the present invention;

FIG. 2 is a schematic structural layout of the inner frame of the multi-frame pod of the present invention;

FIG. 3 is a schematic diagram of the position relationship between the eddy current sensor and the sensing steel plate and the pitching frame according to the present invention;

FIG. 4 is a schematic diagram showing the relative position of the eddy current sensor and the inductive steel plate along the pitch axis according to the present invention;

FIG. 5 is a schematic view of the calculation of the angle between the inner frame to be measured and the mounting frame of the inner frame according to the present invention;

FIG. 6 is a graph of the numerical correspondence of the precise angle and the coarse angle with the analog-to-digital conversion values of the present invention;

FIG. 7 is a graph of the numerical correspondence of the precise and coarse angular difference values to the analog-to-digital conversion values of the present invention.

Detailed Description

The working principle and working process of the present invention will be further explained and explained with reference to the accompanying drawings.

As shown in FIG. 1, the invention applies an eddy current sensor and an induction steel sheet to the design of an inner frame angle measurement system of a multi-frame photoelectric pod so as to improve the angle measurement accuracy. Wherein the electric eddy currentThe sensor is supplied with direct current, the voltage can be +24V or +/-15V, and the output voltage can be-2-18V or 0-5V. The material of the induction steel sheet is required to be No. 45 steel. In the range of the eddy current sensor L₁The output voltage is proportional to the distance between the eddy current sensor and the induction steel sheet, and the proportionality coefficient is k₁. The eddy current sensor can measure the micro distance with high precision (can reach micron level), so according to the characteristic that the rotation range of the inner frame is small, the eddy current sensor is used for measuring the distance change caused by rotation, and then the rotation angle is worked out according to the relation between the distance and the rotation radius.

As shown in fig. 2, the azimuth and pitch axes of the multi-frame pod are both of an inner and outer two-layer frame design, so the inner frame comprises both azimuth and pitch frames.

As shown in fig. 3, the eddy current sensor and the induction steel sheet are mounted on the inner frame to be measured and the mounting frame of the inner frame, respectively.

Mounting position of the eddy current sensor:

referring to fig. 4, the eddy current sensor and the sensing steel plate of the present invention are shown in detail. The extreme left end position of the eddy current sensor is A₁And the position of the induction steel sheet is B. The linear measurement range of the current vortex sensor is A₁And A₃Chord A₁A₃Length L₁。OA₂Perpendicular to A₁A₃The intersection point is O'. When the eddy current sensor is positioned at A₂When in use, the surface of the steel sheet is opposite to the induction steel sheet. Point A of minimum distance of electric eddy sensor from induction steel sheet₃Is L away from the induction steel sheet₃(since eddy current sensors vary in unison, so does the position of the distance steel, generally L)₃≈1mm。

The measurement angle range θ is determined by the inner frame design requirements, and is typically less than ± 3 ° (or 6 °); linear measuring range L of eddy current sensor₁Is a product attribute, typically at 6 mm. The measurement of the eddy current sensor starts from a non-zero value, i.e. the measurement is 1 to 7 mm.

The length of the installation position of the eddy current sensor from the axle center of the inner frame to be measured is R₁Said R is₁Is composed ofWherein L is₁Is the range of the eddy current sensor, theta is the angular range of the required measurement, R₁On the premise of satisfying the inequality, R₁Should be as close as possible to

During the installation process of the eddy current sensor and the induction steel sheet, specific structural conditions are considered, such as the size of a pitch axis, whether the pitch axis interferes with other devices and the like. R₁The value is as large as possible, because the larger the radius is, the higher the angle measurement accuracy is under the condition that the distance measurement accuracy of the eddy current sensor is determined.

When the inner frame to be measured rotates relative to the mounting frame, the distance between the eddy current sensor and the induction steel sheet changes, and the eddy current sensor outputs a voltage signal V related to the distance change;

the voltage signal output by the eddy current sensor is subjected to filtering and analog-to-digital conversion, and the distance h between the eddy current sensor and the induction steel sheet is calculated according to a scale factor of the eddy current sensor and an amplification factor of the analog-to-digital conversion; the distance h from the eddy current sensor to the induction steel sheet is the distance from the central point P of the probe plane of the eddy current sensor to the steel sheet, and the distance h is calculated according to the measured valueWherein k is₁Indicating the scale factor of the eddy current sensor, n indicating the number of bits of the analog-to-digital conversion, η indicating the input voltage range of the analog-to-digital conversion.

And calculating the angle between the inner frame to be measured and the mounting frame of the inner frame according to the distance h between the eddy current sensor and the induction steel sheet.

According to the distance h between the eddy current sensor and the induction steel sheet, the specific implementation mode of calculating the angle beta between the inner frame to be detected and the mounting frame of the inner frame is as follows:

as shown in fig. 5, a rectangular coordinate system xOy is established with OB as the X-axis and O as the origin. OB ═ R₁The straight line l represents a straight line passing through the surface of the steel sheet, and α is an included angle between the straight line where the induction steel sheet is located and the axis of the inner frame to be detected and the connecting line of the steel sheet.

$\mathrm{\α}=\arcsin \left(\frac{0.5L_1+L_3}{R_1}\right).$

The equation of the line l on which the induction steel sheet is located is

y＝tanα(x-R₁)。

Point P is centered on the circular point and has radius R₁Polar angle fromToOn the arc of (a). The coordinates of the point P are such that,

$\left\{\begin{array}{c}x=R_1\cos \mathrm{\β}\\ y=R_1\sin \mathrm{\β}\end{array}\right.,$

wherein,it can be seen that the actual measured frame angle β is slightly greater than the desired frame angle range θ.

Therefore, according to the mathematical relationship, the distance from the point P to the straight line l is

$h=\frac{R_1\sin \mathrm{\β}-R_1\cos \mathrm{\β}\tan \mathrm{\α}+R_1\tan \mathrm{\α}}{\sqrt{1+{\tan }^2\mathrm{\α}}}.$

Wherein R is₁And α are known in the art, $h=\frac{\mathrm{V\η}}{k_1{2}^n},$ solving equations $h=\frac{R_1\sin \mathrm{\β}-R_1\cos \mathrm{\β}\tan \mathrm{\α}+R_1\tan \mathrm{\α}}{\sqrt{1+{\tan }^2\mathrm{\α}}},$ β may be calculated.

The concrete solving process is as follows

According to the formula $h=\frac{R_1\sin \mathrm{\β}-R_1\cos \mathrm{\β}\tan \mathrm{\α}+R_1\tan \mathrm{\α}}{\sqrt{1+{\tan }^2\mathrm{\α}}}$ To obtain the following formula:

$\sin \mathrm{\β}=\frac{h\sqrt{1+{\tan }^2\mathrm{\α}}}{R_1}+\cos \mathrm{\β}\tan \mathrm{\α}-\tan \mathrm{\α}$

and combined sin²β+cos²β being equal to 1, are available,

(1+tan²α)cos²β+2atanαcosβ+a²-1＝0

wherein, $\left\{\begin{array}{c}c=\frac{h\sqrt{1+{\tan }^2\mathrm{\α}}}{R_1}\\ a=c-\tan \mathrm{\α}\end{array}\right.;$

since 0. ltoreq. cos β. ltoreq.1, so

$\cos \mathrm{\β}=\frac{\sqrt{1-c^2+2c\tan \mathrm{\α}}-c\tan \mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\α}},$

Then the process of the first step is carried out,

$\mathrm{\β}=\mathrm{arc}\cos \left(\frac{\sqrt{1-c^2+2c\tan \mathrm{\α}}-c\tan \mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\β}}\right).$

when the accuracy requirement is not high, because α is very small, tan α ≈ 0 can be considered according to the formula $\cos \mathrm{\β}=\frac{\sqrt{1-c^2+2c\tan \mathrm{\α}}-c\tan \mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\α}}$ It is possible to obtain,

${\cos }^2\mathrm{\β}+{\left(\frac{h}{R_1}\right)}^2=1$

therefore, the first and second electrodes are formed on the substrate,since β is also small, it can be considered that

$\mathrm{\β}\≈\frac{h}{R_1}.$

The installation positions of the induction steel sheet and the eddy current sensor can be interchanged and are respectively installed on the installation frame of the inner frame to be tested and the installation frame of the inner frame to be testedAngle of mounting frame of frame ${\mathrm{\β}}_1=\arccos \left(\frac{\sqrt{1-{c_1}^2+2c_1\tan {\mathrm{\α}}_1}-c_1\tan {\mathrm{\α}}_1+{\tan }^2{\mathrm{\α}}_1}{1+{\tan }^2{\mathrm{\α}}_1}\right),$ α therein₁The included angle between the straight line where the eddy current sensor is located and the axis of the inner frame to be detected and the connecting line of the eddy current sensor is included;

the working process of the invention is further explained below with a specific embodiment:

as shown in FIGS. 3 and 4, O is the rotation axis of the pitch frame, and the working radius of the eddy current sensor is R₁. Where θ is 6 °, L is selected₁6 mm. Therefore, the first and second electrodes are formed on the substrate,selection of R₁Is 55 mm.

The closest distance L between the eddy current sensor and the steel sheet₃＝1mm。

According to the formula $\mathrm{\α}=\arcsin \left(\frac{0.5L_1+L_3}{R_1}\right),$ The calculation α is 4.17 °.

The eddy current sensor is electrified, and the output signal of the eddy current sensor is converted into a digital signal by an analog-to-digital converter after passing through an analog low-pass filter. If the input voltage range of the analog-to-digital converter is 0-5V and the number of conversion bits is 16, the amplification factor of the analog-to-digital converter is k_d13107. Scaling factor k for eddy current sensors₁0.83V/mm. The distance measurement accuracy of the eddy current sensor is 5 micrometers, so the angle measurement accuracy is about 0.0052 degrees.

The microprocessor reads the conversion value of the A/D converter as mu ∈ [0,65535 ]]Distance between eddy current sensor and steel sheetSo the pitch frame angle with high precision requirement is according to the formula

$\mathrm{\β}=\mathrm{arc}\cos \left(\frac{\sqrt{1-c^2+2c\tan \mathrm{\α}}-c\tan \mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\β}}\right)$ The pitch frame angle with low calculation and precision requirement is calculated according to a formulaAnd (4) calculating.

Fig. 6 shows the relationship of the fine and coarse values with respect to the analog-to-digital converted value, and fig. 7 shows the difference therebetween. It can be seen that the difference between the two is up to 0.46mrad or 0.026 deg.. Therefore, the user can select the two formulas according to the requirement of accuracy.

The non-disclosed part of the invention is the common general knowledge in the field.

Claims (5)

1. A method for measuring the angle of an inner frame of a multi-frame pod by using an eddy current sensor is characterized by comprising the following steps:

respectively installing an eddy current sensor and an induction steel sheet on an inner frame to be detected and an installation frame of the inner frame;

when the inner frame to be measured rotates relative to the mounting frame, the distance between the eddy current sensor and the induction steel sheet changes, and the eddy current sensor outputs a voltage signal V related to the distance change;

the voltage signal output by the eddy current sensor is subjected to filtering and analog-to-digital conversion, and the distance h between the eddy current sensor and the induction steel sheet is calculated according to a scale factor of the eddy current sensor and an amplification factor of the analog-to-digital conversion;

calculating the angle between the inner frame to be measured and the mounting frame of the inner frame according to the distance h between the eddy current sensor and the induction steel sheet

The length of the installation position of the eddy current sensor from the axis of the inner frame to be measured is R₁Said R is₁Is composed ofWherein L is₁Is the range of the eddy current sensor, theta is the angular range of the required measurement, R₁On the premise of satisfying the inequality, R₁Should be as close as possible to

2. The method for measuring the angle of the inner frame of the multi-frame nacelle by using the eddy current sensor as claimed in claim 1, wherein: calculating the distance between the eddy current sensor and the induction steel sheetWherein k is₁Indicating the scale factor of the eddy current sensor, n indicating the number of bits of the analog-to-digital conversion, η indicating the input voltage range of the analog-to-digital conversion.

3. The method for measuring the angle of the inner frame of the multi-frame nacelle by using the eddy current sensor as claimed in claim 2, wherein: the specific implementation mode of calculating the angle beta between the inner frame to be measured and the mounting frame of the inner frame according to the distance h between the eddy current sensor and the induction steel sheet is as follows:

(4a) calculating an included angle alpha between a straight line where the induction steel sheet is located and the axis of the inner frame to be detected and the steel sheet connecting line:

$\mathrm{\α}=\arcsin \left(\frac{0.5L_1+L_3}{R_1}\right)$

wherein L is₃Representing the minimum distance between the eddy current sensor and the induction steel sheet;

(4b) calculating an angle beta between the inner frame to be measured and the mounting frame of the inner frame by using the included angle alpha and the distance h obtained in the step (4 a):

$\mathrm{\β}=\mathrm{arc}cos\left(\frac{\sqrt{1-c^2+2ctan\mathrm{\α}}-ctan\mathrm{\α}+{\tan }^2\mathrm{\α}}{1+{\tan }^2\mathrm{\α}}\right)$

wherein,

4. the method for measuring the angle of the inner frame of the multi-frame nacelle by using the eddy current sensor as claimed in claim 3, wherein the angle β between the inner frame to be measured and the mounting frame of the inner frame can be calculated by using a simplified formula when the measurement accuracy requirement is low, wherein the simplified formula is as follows:

5. the method for measuring the angle of the inner frame of the multi-frame nacelle by using the eddy current sensor as claimed in claim 4, wherein: the installation positions of the induction steel sheet and the eddy current sensor can be interchanged and are respectively installed on the installation frame of the inner frame to be tested and the installation frame of the inner frame to be testedα therein₁The included angle between the straight line where the eddy current sensor is located and the axis of the inner frame to be detected and the connecting line of the eddy current sensor is included;