JP2000234925A - Attitude detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and weight while ensuring operational reliability by providing an astronomical light detector having a plurality of pixels arranged at a specified interval in the scanning direction of a basic body for focusing an image and the direction orthogonal thereto. SOLUTION: The attitude detector mounted on a satellite, or the like, and utilizing the solar image comprises an optical package 15 combining a lens 14 and a CCD detecting element 16 arranged with a plurality of detecting elements two-dimensionally. Solar light 17 is taken in and a read circuit 20 is actuated by means of a reference clock 18 and an address generator 19 to search the azimuth angle, elevation angle and each CCD pixel. Subsequently, the number of detecting elements capturing the solar image is made to correspond with the attitude angle thus detecting the attitude angle. Resolution is enhanced by a specified processing employing the value of output signals from elements at the opposite ends of an element array providing a maximum width. Since another specified pixel array is employed upon deterioration of a pixel, the angle can be detected without substantially no deterioration of accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an attitude detecting apparatus mounted on a spacecraft such as an artificial satellite and capable of detecting an attitude stably and with high accuracy, and in particular, an attitude detecting method using a solar image. The present invention relates to a detection device.

[0002]

2. Description of the Related Art Conventionally, there are a silicon photodiode system and a one-dimensional CCD system as a system for detecting an angle formed by sunlight on a predetermined axis of a space vehicle such as an artificial satellite.
The photodiode method has been mainly used. FIG.
6 and 7 show the principle of a conventional sun sensor. FIG.
Shows an example of a conventional sun sensor, in which a light receiving element 2 composed of a silicon photodiode molded in a gray code is arranged on a substrate 3.

[0003] A box 1 is provided on the substrate 3 to prevent extra light from entering from outside. A slit plate 4 having a slit S is disposed on the upper surface of the box 1, and sunlight enters only from the slit S.

In the sun sensor configured as described above,
The band-shaped sunlight passing through the slit S is applied to each light receiving element 2 and determines ON / OFF of each bit. The signal output from the light receiving element 2 is amplified by a preamplifier 5 and converted into a digital signal by a comparator 6 at a certain threshold. After that, the shift register 7
The data is converted into serial data and output to the attitude control device of the artificial satellite via the I / F 8.

FIG. 6 shows a CCD (Charge Coupled Device).
This is a conventional example in which a sun sensor is configured by the following. here,
As in the case of FIG. 5, the CCD light receiving element 9 is surrounded by a box 1 and a slit S is provided in a direction orthogonal to the arrangement direction of the CCD light receiving elements 9. The slit S is
It is located approximately at the center of the one-dimensional CCD.

In the sun sensor having such a configuration, the center of the sun incident light due to the light from the slit S is one-dimensional CC.
Positioning is performed by determining on which light receiving element of D the light is to be received. First, after the signal from the light receiving element 9 is amplified by the preamplifier 5, it is converted to a digital signal by the A / D 10. The angle calculation unit 12 calculates the angle data of the center pixel which receives the digital signal of each pixel in the buffer memory 11 and receives the light. The output angle is output to the control device of the artificial satellite via the I / F 13.

As a sun sensor, azimuth (A
z) and elevation (El) are required, and finally, two axes arranged in orthogonal directions as shown in FIG.
A set of sensor devices is required. In FIG. 7, the slit S1 and the slit S2 are arranged in the orthogonal direction. In the slit S1, the elevation angle ± θE is measured around the elevation angle optical axis BE. In the slit S2, the azimuth angle ± θA is measured around the azimuth angle optical axis BA.

[0008]

The first problem with the conventional sun sensor is that the two sets of sensor devices that are orthogonal to each other are required, so that the weight, volume, power consumption, etc., are all twice as large. There was a drawback that would be.
The reason is that since the light receiving element has sensitivity only in one-dimensional direction, a space for two axes is required.

The second problem is that there is a trouble in that the optical axes of azimuth (Az) and elevation (El) are aligned.
Further, when a part of the pixel is deteriorated and cannot be measured, there is a disadvantage that reading at a specific angle becomes impossible. The reason is that as a one-dimensional light receiving element array in advance,
This is because the element is designed, and there is no flexibility to make a determination using another light receiving element.

Further, the sunlight tracking sensor device disclosed in Japanese Patent Application Laid-Open No. 63-29210 determines the sun position by detecting the light receiving element that detects the maximum amount of received light among the light receiving elements. . Therefore, in the invention disclosed herein, there is a possibility that an accurate sun position cannot be detected when a part of the light receiving element is deteriorated.

In the apparatus for determining the attitude of an artificial satellite or the like disclosed in Japanese Patent Application Laid-Open No. 4-343010, an image of a celestial object is focused on a two-dimensional pixel array, the center of the image is obtained by a processing apparatus, and the roll or It indicates a pitch attitude error. Therefore, there is no technical idea that the elevation angle and the azimuth angle can be detected even when a part of the light receiving element is deteriorated as in the present invention.

An object of the present invention is to improve the above-mentioned disadvantages of the prior art, reduce power consumption by reducing the size and weight, and ensure high reliability by operational flexibility.

[0013]

In order to achieve the above-mentioned object, the present invention employs the following basic technical structure. That is, as a first aspect according to the present invention, an optical system mounted on a spacecraft such as an artificial satellite and converging light from a celestial body, a base on which an image is formed by the optical system, and a base An astronomical photodetector that is arranged on the top and detects the image, and a signal processing unit that processes an output signal of the astronomical photodetector, and the astronomical photodetector has a direction that matches a scanning direction of the base and An attitude detecting apparatus having a plurality of pixels arranged at predetermined intervals in a direction orthogonal to the scanning direction.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned problems in the prior art, an attitude detecting apparatus according to the present invention is equipped with an optical system mounted on a spacecraft such as an artificial satellite to converge light from a celestial body. A base on which an image is formed by the optical system, an astronomical light detector arranged on the base to detect the image, and a signal processing unit for processing an output signal of the astronomical light detector, The astronomical photodetector has a plurality of pixels arranged at predetermined intervals in a direction coinciding with a scanning direction of the substrate and a direction orthogonal to the scanning direction. .

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a posture detecting apparatus according to the present invention. FIG. 1 is a block diagram showing a configuration of a posture detecting device according to one embodiment of the present invention, FIG. 2 is an explanatory diagram showing an enlarged light receiving element surface of the posture detecting device of the present invention, and FIG. FIG. 4 is an explanatory diagram showing a relationship between a light receiving element surface of a posture detecting device and an image forming position of the sun.

Here, the attitude detecting device is mounted on a spacecraft such as an artificial satellite, and an optical system for converging light from a celestial body, a base on which an image is formed by the optical system, and a base on the base. An astronomical photodetector is provided for detecting the image, and a signal processing unit for processing an output signal of the astronomical photodetector is provided.

Next, the posture detecting apparatus of the present invention will be specifically described with reference to an embodiment using the sun. As shown in FIG. 1, a CC in which a plurality of detection elements are arranged two-dimensionally.
A signal from sunlight 17 is taken in from an optical system package 15 in which a D detection element 16 and a lens 14 are combined. The read circuit 20 is operated by the reference clock 18 and the address generator 19 to search for the CCD pixel having the maximum width of the solar image at each of the azimuth angle (Az) and the elevation angle (El). In this embodiment, it is preferable that the signal from the CCD detecting element is temporarily stored in a memory which can be accessed arbitrarily. Such a memory is prepared in the read circuit 20, for example. In the attitude detecting device according to the present invention, the viewing angle is determined in advance by the optical system package 15, and therefore, the number of the CCD detecting elements that capture the sun image can be made to correspond to the attitude angle. For example, if the viewing angle is 60 degrees and the number of detection elements in the azimuth and elevation directions is 6000, the attitude angle can be detected with an accuracy of 0.01 degree per element. In the present invention, the angle is detected with higher accuracy by using the output signal amount of the detection element as described below.

First, the detection in the azimuth (Az) direction will be described.
The element array is searched to find the maximum width of the solar image, and when the element row giving the maximum width is detected, the positions of the elements at both ends are output as pixel numbers A1 and A2. This is shown in FIG. Next, also in the elevation (El) direction, similarly, the element row in the El direction is searched to find the maximum width of the solar image, and when the element row giving the maximum width is detected, the positions of the elements at both ends are determined by the pixels. Output as numbers E1 and E2. In the buffer 21, these A1, A2, E
1, the pixel number of E2 is stored. On the other hand, assuming that the output signal amounts output from the detection elements at both ends that give the pixel numbers A1 and A2 in the azimuth direction are a1 and a2, these amounts correspond to + Δ and −Δ in FIG. Mean shift angle. The output signal of this detection element is normalized by an output signal obtained from the detection element located at the center of the solar image by the calculation circuit 28, and is +0.5
It is standardized as an auxiliary signal of .about.-0.5.
Is stored in the buffer. At this time, the amplitude normalizer 22 supplies an output signal obtained from the detection element located at the center of the solar image to the calculation circuit. Further, the amplitude normalizer 22 calculates the pixel numbers A1, A2, E1, E
In the search for obtaining 2, the signal output amount of each detection element is also supplied to the readout circuit 20 as a reference signal when determining the signal output amount. The amplitude normalizer 22 is for correcting a change in a signal due to an aging of the sensor, a change in the amount of sunlight, a posture angle, adhesion of dust, and the like. In the present invention, by utilizing this auxiliary signal, an additional 10
To achieve a resolution of 0.001 degrees. Similarly, the pixel number E in the elevation direction
Assuming that the output signal amounts output from the detection elements at both ends that give 1, E2 are e1 and e2, these are also normalized and stored in the buffer as auxiliary signals. In the following description, the signals a1, a2, e1, and e2 are assumed to be standardized auxiliary signals.

Next, a specific determination of the element output will be described. In FIG. 2, assuming that the normalized output voltages of the elements at both ends of the solar image are ± 0.5 as shown in FIG. 4, elements having small absolute values including 0 (that is, closer to the center of the pixel) An element on which the optical axis (sun image) is located is selected, and its pixel numbers are A1 and A2, respectively. Now, assuming that the edge of the solar image comes to the element of θA2, the output signals of θA1, θA2, and θA3 are compared, and the element having the smallest normalized signal is determined as the element at the end capturing the solar image. Is A2. Further, the normalized signal of this element, that is, the auxiliary signal is stored in the buffer as a2. In this way, after all, a
1, a2, e1, and e2 signals are read, and a calculation circuit 2
8 buffers.

Thereafter, A1 and A2 are added by an adder 23a, and a1 and a2 are subtracted by a subtractor 24a. The results A12 and a12 are further added by an adder 25a and multiplied by θO / 2 by an angle generator 26a to obtain θ
A fine angle A is generated. The same processing is performed for the E1, E2, e1, and e2 in the elevation direction by using the adder 23e, the subtractor 24e, the adder 25e, and the angle generator 2
6e to generate the fine angle θE. ΘA and θE obtained in this way are output to, for example, a satellite attitude control device via the interface circuit 27.

In summary, in the azimuth direction, the pixel numbers of the elements at both ends of the solar image are denoted by A1 and A, respectively.
2, and the normalized auxiliary signal from these elements is a
1, a2, the course angle θA of the azimuth angle (Az)
C is represented by Equation 1. Here, θo is a unit angle of one pitch. Further, the fine angle θA at that time is expressed by Expression 2.

ΘAC = θo [(A1 + A2) / 2] (1)

ΘA = θo [(A1-a1 + A2 + a2)] / 2 = θo [(A1 + A2 + a2-a1)] / 2 Equation 2

Similarly, the fine angle θ in the elevation direction
E is represented by Equation 3. θE = θo [(E1 + E2 + e2-e1)] / 2 Equation 3

In this way, the azimuth and elevation angle of an artificial satellite or the like can be detected using sunlight. In the present invention, since a two-dimensional CCD is used,
One azimuth detection device can detect both azimuth (Az) and elevation (El).

Further, as shown in FIG. 3, when normal detection cannot be performed due to the deterioration of the pixel 29, high-accuracy posture detection can be performed by using an element row including the immediately adjacent pixel 30.

In the above description, an example in outer space such as an artificial satellite has been described, but the present invention can also be used for angle detection such as civil engineering work and surveying on the ground. It should be noted that the present invention is not limited to the above embodiments, and various design changes can be made based on the technical idea of the present invention.

[0028]

The first effect of the present invention is that azimuth (Az) and elevation (E) are realized by one optical system package.
l) It is possible to detect the angle of two axes,
Weight reduction has become possible. The reason for this is that instead of using a combination of a one-dimensional optical detection element and a slit as in the past,
That is, a two-dimensional detection element and a lens optical system are used.

The second effect is that even if one pixel of the detecting element deteriorates and becomes inoperable, the angle cannot be detected and the reliability can be increased. That is, there is an effect equivalent to that obtained by forming a redundant configuration. The reason is that the angle detection can be performed with almost no deterioration in accuracy by using a pixel row that escapes in the direction orthogonal to one pixel from the widest (string indicating the diameter) pixel row of the solar image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a posture detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an enlarged light receiving element surface of the attitude detecting device of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a light receiving element surface of the attitude detecting device of the present invention and an image forming position of the sun.

FIG. 4 is an explanatory diagram showing a relationship between a light receiving element image and an output signal in the posture detecting device of the present invention.

FIG. 5 is an explanatory view showing an example of a conventional attitude detecting device using a photodiode detecting element surface.

FIG. 6 is an explanatory diagram illustrating an example of a conventional posture detecting device using a one-dimensional CCD detecting element.

FIG. 7 is a perspective view showing a configuration of a conventional attitude detecting device optical system package.

[Explanation of symbols]

 S slit θ sunlight incident angle OUT output signal BA azimuth angle optical axis BE elevation angle optical axis θA azimuth angle θE elevation angle A1, A2 azimuth pixel number a1, a2 azimuth auxiliary signal E1, E2 elevation pixel number e1, e2 Elevation auxiliary signal ADD Adder SUB Subtractor θA1, θA2, θA3, θA4 Azimuth direction pixel ± Δ Fine angle 1 Box 2 Light receiving element 3 Substrate 4 Slit plate 5 Preamplifier 6 Comparator 7 Shift register 8 I / F 9 CCD light receiving element 10 A / D 11 Buffer memory 12 Angle calculator 13 I / F 14 Lens 15 Optical system package 16 CCD detector 17 Sunlight 18 Reference clock 19 Address generator 20 Readout circuit 21 Buffer 22 Amplitude normalizer Reference Signs List 23 adder 24 subtracter 25 adder 26 angle generator 27 interface circuit 28 calculation circuit 29, 30 pixels

Claims (7)

[Claims] An optical system mounted on a spacecraft such as an artificial satellite for converging light from a celestial body, a base on which an image is formed by the optical system, and a base arranged on the base to detect the image An astronomical photodetector, and a signal processing unit that processes an output signal of the astronomical photodetector, wherein the astronomical photodetector is arranged in a direction coinciding with the scanning direction of the substrate and in a direction orthogonal to the scanning direction. A plurality of detection elements are arranged in the same. 2. When the celestial body is detected by the celestial body photodetector, the attitude angle is determined from the number of detection elements that have caught the celestial body and the signal amounts obtained from the detection elements at both ends of the detection element group that has caught the celestial body. 2. The attitude detecting apparatus according to claim 1, wherein the accuracy is obtained in units of pixels or more. 3. The method according to claim 1, wherein when the attitude angle is obtained from the signal amounts obtained from the detection elements at both ends of the detection element group capturing the celestial body, a difference between the signal amounts obtained from the detection elements at both ends is used. The attitude detection device according to claim 2. 4. The angle detection by the celestial light detector, wherein angle detection using a diameter width orthogonal to the celestial light image and angle detection using a chord shorter than the orthogonal width are performed. Item 7. The attitude detection device according to Item 1. 5. The attitude detecting apparatus according to claim 1, wherein the celestial body light detector detects a light image from the sun. 6. The signal processing unit includes an amplitude normalizer, and performs a normalization process on a signal from the celestial body photodetector with an output of a detection element at a central portion of a detection element group that has captured the celestial body. The attitude detection device according to claim 1. 7. The attitude detecting device according to claim 1, wherein the astronomical light detector uses a two-dimensional CCD.