CN110645954B - Method for calculating visual axis angle of four-frame two-axis stable platform - Google Patents

Abstract

The invention discloses a method for calculating the visual axis angle of a four-frame two-axis stable platform, which comprises the steps of respectively obtaining an outer azimuth angle A, an outer pitch angle B, an inner azimuth angle a and an inner pitch angle B by angle sensors on an outer azimuth frame, an outer pitch frame, an inner azimuth frame and an inner pitch frame of an airborne photoelectric turret four-frame two-axis stable platform, obtaining two equal direction cosine matrixes C' and C by using two coordinate transformation methods, obtaining an equation about A, B, a and B, an azimuth angle alpha of a visual axis relative to a turret base and an azimuth angle beta of the visual axis relative to the turret base, and further calculating alpha and beta. The azimuth angle alpha and the pitch angle beta obtained by the method are accurate values obtained by calculating the parameters which can be accurately obtained, and the method is directly calculated by space coordinate transformation without errors caused by a system method, so that the method can meet the requirements of high-precision visual axis use scenes, and does not install new measuring equipment on the basis of the prior art, thereby saving the cost of updating the equipment in a phase-changing manner.

Description

Method for calculating visual axis angle of four-frame two-axis stable platform

Technical Field

The invention belongs to the technical field of photoelectric turret control, and particularly relates to a method for calculating the visual axis angle of a four-frame two-axis stable platform.

Background

The high-precision airborne photoelectric turret usually adopts a four-frame two-axis stable platform form and sequentially comprises an outer orientation frame, an outer pitching frame, an inner orientation frame and an inner pitching frame from outside to inside according to a frame structure nesting relation. An angle sensor is arranged on each frame rotating shaft, and the measuring angles are A, B, a and B respectively. And the photoelectric turret base coordinates are rotated to the sensor visual axis coordinates once through the outer azimuth angle A, the outer pitch angle B, the inner azimuth angle a and the inner pitch angle B. When the photoelectric turret is operated to perform tasks, the azimuth angle alpha and the pitch angle beta of the current visual axis relative to the turret base need to be acquired and displayed in real time.

There are two methods to represent the azimuth angle α and the pitch angle β of the current boresight relative to the turret base:

(1) because the four-frame two-axis stable platform requires the outer frame to follow the inner frame in the control design, and the inner azimuth angle a and the inner pitch angle B are smaller, the outer azimuth angle A is usually used for representing the azimuth angle alpha of the visual axis, and the outer pitch angle B is used for representing the pitch angle beta of the visual axis.

(2) Expressed by the way that the inner and outer frame corners are fused: α ═ a + a/cos (B), β ═ B + B.

The second method is more accurate than the first method, but still has a large error in the situation that the visual axis angle is extremely accurate, such as target positioning and target geographic guiding.

Therefore, it is desirable to find a method for accurately determining the azimuth angle α and the pitch angle β of the current boresight relative to the turret base.

Disclosure of Invention

In order to accurately determine the azimuth angle alpha and the pitch angle beta of the current visual axis relative to the turret base, the invention provides a method for calculating the visual axis angle of a four-frame two-axis stable platform.

A method for calculating the visual axis angle of a four-frame two-axis stable platform is characterized by comprising the following steps: angle sensors arranged on an outer azimuth frame, an outer pitching frame, an inner azimuth frame and an inner pitching frame of the four-frame two-axis stable platform respectively acquire an outer azimuth angle A, an outer pitching angle B, an inner azimuth angle a and an inner pitching angle B;

using A, B, a, B the directional cosine matrix C is used in the order Z-X-Y₁The coordinates of the turret base are transferred to the coordinates of the turret outer orientation frame, and then a direction cosine matrix C is used₂Turning to the pitching frame coordinate outside the rotating tower, and then using the direction cosine matrix C₃Turning to the coordinate of the azimuth frame in the turret, and then using the direction cosine matrix C₄Transferring to the pitching frame coordinate in the turret, namely the visual axis coordinate, thereby obtaining a total direction cosine matrix C' in the whole conversion process;

an azimuth angle alpha of a visual axis relative to the turret base, a pitch angle beta of the visual axis relative to the turret base and a roll angle gamma of the visual axis relative to the turret base are respectively rotating angles around Z, X, Y coordinate axes of the turret base, and a direction cosine matrix C with space coordinate conversion is directly used for converting the coordinates of the turret base to the coordinates of the visual axis;

let C' be C, the azimuth angle α and the pitch angle β can be calculated from a, B, a, and B by making the matrix corresponding elements equal.

Further, the

Further, the

Further, the

Further, the

Further, the direction cosine matrix

Further, a direction cosine matrix

Further, the

Beta is arcsin (-c)₁₃) At the same time, c₁₂＝cosbcosacosBsinA+cosbsinacosA-sinbsinBsinA、c₁₁＝cosbcosacosBcosA-cosbsinasinA-sinbsinBcosA、c₁₃α and β were calculated from-cosbcosasinB-sinbcosB.

In addition, in the space rotation coordinate transformation, when the rotation sequence and the rotation angle are determined, the direction cosine matrix of the coordinate transformation is uniquely determined. The rotation sequence and angle have a mapping relation with the direction cosine matrix. Under the condition of the uniform direction cosine matrix, the rotation angles of the required sequence can be calculated according to the elements in the matrix, therefore, the transformation results of C and C are the same, and the turret base coordinate is converted to the visual axis coordinate, so that C' can be made equal to C, and then alpha and beta can be calculated.

It can be seen that the method disclosed in the present invention list C, C ' does not aim to calculate C, C ', but rather uses C, C ' to construct equations for a, B, α, β, and further calculates α, β from a, B, a, B. In practical application, the outer azimuth angle a, the outer pitch angle B, the inner azimuth angle a and the inner pitch angle B can be respectively obtained directly through angle sensors arranged on an outer orientation frame, an outer pitch frame, an inner orientation frame and an inner pitch frame of the four-frame two-axis stable platform, and alpha and beta can be directly calculated. In addition, if necessary, the rolling angle of the visual axis can be calculated

Compared with the prior art, the invention has the following beneficial effects: the azimuth angle alpha and the pitch angle beta of the visual axis obtained by the invention are accurate values obtained by calculating the parameters which can be accurately obtained, and the method is directly calculated by space coordinate transformation without errors caused by a system method, so that the requirement of a high-precision visual axis use scene can be met, and no additional measuring equipment is arranged on the basis of the prior art, thereby phase change and equipment updating cost are saved.

Detailed Description

The present invention will be further explained with reference to specific examples. The following examples are only for explaining the present invention, and the purpose of substituting data is to more specifically explain the present invention, but not to limit the present invention, and the technical solutions obtained by simple substitution and superposition based on the present invention should fall into the protection scope of the present invention.

Example 1

The outer azimuth angle A of the four-frame two-axis stable platform is 45 degrees, the outer pitch angle B is-45 degrees, the inner azimuth angle a is 0.5 degrees, and the inner pitch angle B is-0.5 degrees, so that the four-frame two-axis stable platform has the advantages of simple structure, low cost, high stability and the like

While

β＝arcsin(-c₁₃)，

At the same time, C₁₂＝0.5017690、C₁₁＝0.4894284、C₁₃＝0.7132234，C₂₃＝-0.0061706、C₃₃0.7049096, the azimuth angle alpha of the current visual axis relative to the turret base is 45.713 degrees, the pitch angle beta of the current visual axis relative to the turret base is-45.498 degrees, and the roll angle gamma of the current visual axis relative to the turret base is-0.5 degrees.

In contrast, the conventional inner and outer frame angle blending method is adopted, where α ═ a + a/cos (B) ═ 45.707 °, and β ═ B + B ═ 45.500 °. It can be seen that, compared with the technical scheme of the present invention, the traditional inner and outer frame angle fusion manner is more accurate in both the obtained azimuth angle α of the current visual axis relative to the turret base and the obtained azimuth angle β of the current visual axis relative to the turret base.

Claims (2)

1. A method for calculating the visual axis angle of a four-frame two-axis stable platform is characterized by comprising the following steps: angle sensors arranged on an outer azimuth frame, an outer pitching frame, an inner azimuth frame and an inner pitching frame of the four-frame two-axis stable platform respectively acquire an outer azimuth angle A, an outer pitching angle B, an inner azimuth angle a and an inner pitching angle B;

using A, B, a, B the directional cosine matrix C is used in the order of the coordinate axes Z-X-Y of the turret base₁The coordinates of the turret base are transferred to the coordinates of the turret outer orientation frame, and then a direction cosine matrix C is used₂Turning to the pitching frame coordinate outside the rotating tower, and then using the direction cosine matrix C₃Turning to the coordinate of the azimuth frame in the turret, and then using the direction cosine matrix C₄Transferring to the pitching frame coordinate in the turret, namely the visual axis coordinate, thereby obtaining a total direction cosine matrix C' in the whole conversion process;

an azimuth angle alpha of a visual axis relative to the turret base, a pitch angle beta of the visual axis relative to the turret base and a roll angle gamma of the visual axis relative to the turret base are respectively angles of the visual axis rotating around Z, X, Y coordinate axes of the turret base, and a direction cosine matrix C with space coordinate conversion is used for converting the coordinates of the turret base to the coordinates of the visual axis;

c' is equal to C, and the azimuth angle α and the pitch angle β can be calculated by using a, B, a and B;

said

Said

Said

Said

The direction cosine matrix

Directional cosine matrix

Said

Beta is arcsin (-c)₁₃) At the same time, c₁₂＝cosbcosacosBsinA+cosbsinacosA-sinbsinBsinA、c₁₁＝cosbcosacosBcosA-cosbsinasinA-sinbsinBcosA、c₁₃α and β were calculated from-cosbcosasinB-sinbcosB.

2. The method for calculating the visual axis angle of the four-frame two-axis stabilized platform as claimed in claim 1, wherein: roll angle

Wherein, c₂₃＝sinasinB，c₃₃＝-sinbcosasinB+cosbcosB。