JP2645109B2 - Sun sensor - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to a solar sensor used for attitude control of an artificial satellite, control of a solar battery paddle, and the like.

(Prior Art) Generally, this type of sun sensor is, as shown in FIG.
A pair of photoelectric elements 1a and 1b each having a quadrangular shape with one side inclined such as a solar cell element are arranged in combination with their oblique sides facing each other, and are opposed substantially orthogonally to the respective oblique sides of these photoelectric elements 1a and 1b. The mask members 2 having the slits 2a are arranged facing each other with an interval of h. When the sunlight enters from the slit 2a of the mask member 2 at the solar incident angle に 対 し て with respect to the reference axis and the solar image 3 is formed, the output voltages A and A corresponding to the solar image 3 B respectively. The output voltages A and B of the photoelectric elements 1a and 1b are guided to a signal processing system (not shown), and the calculation of C = (AB) / (A + B) is performed to generate a sun angle signal C.

Here, as shown in FIG. 5 (b), the sun angle signal C is independent of the value of the insensitive axis angle β (the sun incident angle in the slit direction) and the sensitivity axis α (the sun incident in the direction orthogonal to the slit). Angle), the shape of the photoelectric elements 1a and 1b,
Assuming that a constant determined by the efficiency and the divider characteristics is D, the constant is expressed by the equation C = D · tan ・. Therefore, the sun angle signal C is Θ ≒ ta
It is provided as sun angle information only in the angle range approximated by nΘ.

By the way, in the above-described sun sensor, the approximation error of {tan} is the sixth error in the sun angle signal C due to its method.
It occurs as shown in the figure, and has an error of about 4.3% in absolute value when, for example, the solar incident angle Θ = 20 °.

Therefore, conventionally, it has been determined that the angle is used within an angle range in which an approximation error of {tan} is allowable. Also, tan ^-1 C / D
In such a case, there is a problem that the signal processing system becomes very complicated.

(Problems to be Solved by the Invention) As described above, in the conventional sun sensor, the approximation error is used within an allowable range, and conversely, in order to correct the approximation error of {tan}, tan ^-1 C Since it is necessary to perform the calculation of / D, there is a problem that when the measurement angle is wide, a large error occurs and a very complicated signal processing system is required to correct the error.

The present invention has been made in view of the above circumstances, and provides a sun sensor having a simple configuration and capable of realizing highly accurate detection of sun angle information in which an approximation error of {tan} has been corrected. The purpose is to do.

[Constitution of the Invention] (Means for Solving the Problems) The present invention relates to a pair of photoelectric elements formed by converting light energy obtained by combining oblique sides of a quadrangle with one side thereof facing each other into electric energy. A mask member disposed to face the sun and having a slit substantially orthogonal to the oblique side of the photoelectric element, and an output of the photoelectric element in which a solar image is formed through the slit of the mask member. In a sun sensor comprising a signal processing system that generates a sun angle signal from a voltage, a current limit is applied to the sun angle signal to correct the sun angle of incidence Θ in a direction opposite to tan Θ, tan
A correction circuit having a non-linear element for correcting the approximation error of Θ is provided.

(Operation) According to the above configuration, the sun angle signal tends to increase from the sun incident angle Θ in proportion to tan 、, but correction is performed in the reverse direction approaching Θ by the correction circuit, and the error of Θ ≒ tanΘ is corrected. Is done. As a result, the error correction of {tan} is realized without performing the tan ^-1 C / D operation as in the related art, thereby simplifying the signal processing system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a solar sensor according to an embodiment of the present invention, in which a pair of quadrilateral photoelectric elements 10a and 10b having one side inclined, such as a solar cell element, is arranged in combination with the high oblique sides facing each other. Is done. On these photoelectric elements 10a and 10b, slits 11 of a mask member are disposed so as to be substantially orthogonal to respective oblique sides thereof (only slits of the mask member are shown in the drawing), and each output end thereof is connected to a signal processing system. Are connected to the adder 12 and the subtractor 13. Output terminals of the adder 12 and the subtractor 13 are connected to a divider 14. A signal output terminal E is connected to an output terminal of the divider 14 via a correction circuit 15 and an output buffer 16. This correction circuit 16 is composed of a non-linear element, for example, a resistor R1 and Zener diodes CR1 and CR2. Assuming that the resistor R1 is approximately 10 kΩ and the breakdown voltage of the Zener diodes CR1 and CR2 is 4.7 V, the voltage at the X position on the input side and the output The relationship between the voltages at the Y position on the side has characteristics as shown in FIG.

In the above configuration, when the solar light enters the slit 11 at an angle of the sun angle に 対 し て with respect to the reference axis, and the solar image 17 is formed, the photoelectric elements 10a and 10b have an output corresponding to the solar image 17. Voltages A and B are generated and output to the adder 12 and the subtractor 13, respectively. The adder 12 and the subtractor 13 add and subtract the output voltages A and B of the photoelectric elements 10a and 10b, respectively, and output the result to the divider 14. Then, the divider 14 performs an operation of C = (A−B) / (A + B) to generate the sun angle signal C. As shown in FIG. 3, this sun angle signal C is D
Has a characteristic of tan Θ (D is a constant), and is guided to a correction circuit 15 having a characteristic as shown in FIG.
Is corrected in the direction opposite to the direction in which tan is applied, and is corrected so as to be proportional to the solar incident angle Θ. in this case,
The parameters required for adjustment of the correction circuit 15 are determined by the output gain of the divider 14, the value of the resistor R1, and the breakdown voltage of the Zener diodes CR1 and CR2. Since the output does not increase above the breakdown voltage of the Zener diodes CR1 and CR2, the breakdown voltage becomes a saturated output, and the range up to the breakdown voltage becomes the sun angle detection range.

Next, the sun angle signal C corrected by the correction circuit 15 is
The signal is guided to the signal output terminal E via the output buffer 16, and as shown in FIG. 4, high-accuracy sun angle information proportional to the solar incident angle Θ ≒ corrected for the error of Θ ≒ tanΘ is obtained.

The Zener diodes CR1 and CR2 are not limited to those having a breakdown voltage of 4.7 V, and those having a breakdown voltage near 5 V at which the Zener voltage temperature coefficient γz is 0 mV / ° C. are used.

As described above, the sun sensor is provided with the correction circuit 15 that limits the current of the sun angle signal C and corrects the sun angle Θ in the direction opposite to the direction of tan Θ with respect to the sun angle Θ. By increasing the error of 増 加 tanΘ, it is possible to detect the corrected sun angle information, so that the error of Θ ≒ tanΘ can be corrected without performing the calculation of tan ^-1 C / D as in the past. Can be realized, so that the signal processing system can be simplified as much as possible.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to realize highly accurate detection of sun angle information with a simple configuration and with correction of the approximation error of {tan}. A sun sensor can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a sun sensor according to an embodiment of the present invention, FIGS. 2 to 4 are characteristic diagrams for explaining the operation of FIG. 1, and FIGS. 5 and 6. FIG. 3 is a view for explaining a problem of a conventional sun sensor. 10a, 10b: photoelectric element, 11: slit, 12: adder, 13: subtractor, 14: divider, 15: correction circuit, 16
…… Output buffer, 17 …… Solar image.

Claims (1)

(57) [Claims] 1. A pair of photoelectric elements which convert light energy obtained by combining the oblique sides of a quadrangle with one side thereof facing each other into electric energy, and which is substantially orthogonal to the oblique side of the photoelectric element. A mask member having a slit opposed to the sun, and a signal processing system for generating a sun angle signal from an output voltage of the photoelectric element in which a solar image is formed via the slit of the mask member; In a solar sensor comprising: a correction having a non-linear element for correcting the sun angle signal to a direction opposite to tan Θ with respect to the sun angle か け て by applying current limitation to the sun angle signal, and correcting an approximation error of Θ ≒ tan Θ A sun sensor comprising a circuit.