A nano-type APS sun sensor

Abstract

A nano APS sun sensor, comprising: a light introducer, an SOC processing board, a main body structure and a reference mirror; wherein, the light introducer, the SOC processing board and the reference mirror are installed on the main body structure; the reference mirror is used to represent the body coordinate system of the nano APS sun sensor; the light introducer uses a cross slit to realize the attenuation of the sunlight intensity and the introduction of the sun rays, and the SOC processing board realizes image acquisition and image processing and outputs the sun azimuth information through an interface.

Description

Technical Field

[0001] The invention relates to the field of optical attitude sensors for spacecraft attitude measurement. Background Art

[0002] The solar sensor is an optical attitude sensor that uses the sun as the reference position to measure the angle between the spacecraft attitude and the solar light vector. Because the solar sensor has a large field of view, good dynamic performance, and the sun is a relatively obvious target in space, solar sensors are widely used on various spacecraft to assist spacecraft in solar capture, solar cruise, and attitude determination.

[0003] Traditional solar sensors are mainly based on silicon photovoltaic cells, which have the characteristics of simple design, good environmental adaptability, and moderate output accuracy, but they mostly use photocurrent as output, require subsequent sampling and processing, and have complex interfaces. With the development of CCD and CMOS image sensors, solar sensors based on CCD and CMOS image sensors have appeared one after another, mostly using an integrated design, which has the characteristics of high accuracy and simple interface, but the product size and power consumption are large due to the need for processors such as FPGA, DSP or single-chip microcomputer. Summary of the invention

[0004] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and provide a nano-type APS solar sensor.

[0005] The technical solution of the present invention is: a nano-type APS solar sensor, including: a light introducer, a SOC processing board, a main structure and a reference mirror;

[0006] Among them, the light introducer, SOC processing board and reference mirror are installed on the main structure; the reference mirror is used to characterize the coordinate system of the nano-APS solar sensor body; the light introducer adopts a cross light slit to achieve the attenuation of sunlight intensity and the introduction of sunlight, the SOC processing board realizes photoelectric conversion, image acquisition and image processing, and outputs the solar position information through the interface.

[0007] Preferably, the light introducer utilizes MEMS technology to achieve coating and photolithography.

[0008] Preferably, the light introducer is designed with three layers of film on the upper surface of the substrate glass, which are anti-reflection film, neutral attenuation film and anti-reflection film from the inside to the outside of the glass substrate; a narrow-band attenuation film and an anti-reflection film are designed on the lower surface of the substrate glass, and a cross slit is engraved on the anti-reflection film.

[0009] Preferably, the anti-reflection film ensures that the reflectivity of the film layer is less than 2%, the transmittance of the neutral attenuation film is 1 / 15000, and the transmission band of the narrow-band attenuation film is 800nm±5nm.

[0010] Preferably, the slit width of the cross-shaped light slit ranges from 10um to 12um.

[0011] Preferably, the SOC processing board includes an image sensor, an SOC device, an RS422 interface device, and an internal power conversion DC-DC;

[0012] The internal power conversion DC-DC realizes the conversion of the external 5V power supply into 3.3V, 1.5V, and 2.8V to supply power to the SOC device and the image sensor; the SOC device has built-in logic resources to control the image sensor, collect images, and extract solar bright spots, and the SOC device has built-in ARM Cortex-M3 core resources to calculate the two-axis solar angle;

[0013] The power-on reset is realized by using an RC circuit and a 74LVC2G14 NOT gate for the external power-on reset of the SOC device.

[0014] Preferably, the ARM Cortex-M3 core resources use the center point of the cross-shaped light slit to calculate the two-axis solar angle, and use the four edge points to assist in calculating the single-axis solar angle. When the light slit is contaminated, the two-axis solar angle is output through the four edge points respectively.

[0015] Preferably, under normal circumstances, the two-axis solar angle (α 中心 , β 中心 ) calculated using the center point of the cross-shaped light slit is used as the output of the sun sensor; to improve reliability, α 中心 is compared with the single-axis solar angle α 边缘1 and α 边缘3 calculated using the edge points, and the output is taken in a 2-out-of-3 manner. Similarly, for β 中心 , β 边缘1 and β 边缘3 of the three angles, the output is taken in a 2-out-of-3 manner.

[0016] Preferably, the two-axis solar angle calculated using the center point of the cross-shaped light slit is compared with the coaxial solar angle calculated using the edge points respectively. If the deviation of the three angles is less than 0.03°, the average value of the three angles is used as the final output. If one of the deviations of the three angles exceeds 0.03°, the average of the remaining two is used as the final output. If the mutual deviations of the three angles all exceed 0.03°, the central angle is directly used as the output.

[0017] Preferably, the deviation between the x normal of the reference mirror and the u direction of the image sensor is less than 1 arcminute, and the deviation between the y normal of the reference mirror and the v direction of the image sensor is less than 1 arcminute.

[0018] The beneficial effects of the present invention compared with the prior art are:

[0019] The "cross" light slit is adopted, and the product has strong anti-pollution ability. When the local area of the light slit is blocked by dust, the angle can still be calculated through the light transmitted through other areas of the slit, and the product function can still be ensured without loss.

[0020] The SOC processor is adopted. The programmable logic resources and ARM processor resources are simultaneously available inside the same chip. There are rich FLASH and RAM resources inside the chip, and no peripheral configuration is required, greatly simplifying the circuit design and realizing the minimized circuit board design.

[0021] The interface is simple. The external interfaces of the product include a +5V power supply and an RS422 interface.

[0022] The typical indicators are as follows: volume 35mm × 35mm × 15mm, weight 25g, power consumption 0.5W, field of view 120° × 120°, accuracy better than 0.05° (3σ), data update rate greater than 10Hz. It has the advantages of high accuracy, small size, light weight, integration, and convenient interface. Description of the Drawings

[0023] Figure 1 Overall composition of the nano-type APS sun sensor;

[0024] Figure 2 Schematic diagram of the light introducer;

[0025] Figure 3 Schematic diagram of the "cross" light slit imaging;

[0026] Figure 4 Circuit principle block diagram;

[0027] Figure 5 Three-view drawing of the overall structure design of the nano-type APS sun sensor;

[0028] Figure 6 Corresponding relationship diagram between the reference mirror coordinate system and the image sensor coordinate system. Detailed Implementation Modes

[0029] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0030] It should also be noted that, for the convenience of description, only the parts related to the present invention rather than all the content are shown in the drawings. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0031] Micro-nano satellites have miniaturization requirements for the weight, volume, and power consumption of solar sensors, etc., and require simple interfaces. Based on this background, technologies such as SOC (System On a Chip) and MEMS are used to develop a nano-type APS solar sensor, realizing a nano-type APS solar sensor with a simple interface, excellent performance, and plug-and-play function.

[0032] The working principle of the nano-type APS solar sensor is to regard the sun as an infinitely distant approximate point light source, and the sunlight reaching the surface of the sensor is approximately parallel light. The light introduction device is used to project the sunlight onto the image sensor to form a bright spot. By calculating the centroid of the bright spot and then comparing it with the centroid position when the light is incident at a zero-degree angle, the attitude angle of the reference plane of the sensor relative to the sun can be obtained, where the imaging position when the light is incident at a zero-degree angle is obtained through the calibration of the sensor.

[0033] As Figure 1 shown, the nano-type APS solar sensor of the present invention consists of a light introduction device, an SOC processing board, a main structure, and a reference mirror. The light introduction device realizes the attenuation of sunlight intensity and the introduction of sunlight. The SOC processing board realizes image acquisition and image processing, and outputs the solar azimuth information through the RS422 interface. The reference mirror represents the body coordinate system of the nano-type APS solar sensor, and the main structure is responsible for installing the light introduction device, the SOC processing board, the reference mirror, etc.

[0034] The present invention realizes the coating and lithography of the light introduction device based on MEMS technology. As Figure 2 shown, a "cross" light slit is adopted. The solar angles of two axes are calculated using the center point, and the solar angle of a single axis is calculated with the assistance of four edge points. Even when the center point is completely invisible due to contamination of the light slit, the solar angles of two axes can still be output respectively through the four edge points. The calculation principle is as follows:

[0035] As Figure 3 shown, (x 中心 , y 中心 ) is the extractable coordinate of the center point, x 边缘1 and x边缘3 The x-axis coordinates extracted for Edge 1 and Edge 3, y 边缘2 and y 边缘4 The y-axis coordinates extracted for Edge 2 and Edge 4, x 0中心 The x-axis coordinate when the center point is at zero position, y 0中心 The y-axis coordinate when the center point is at zero position, h 中心 The distance from the photosensitive surface of the center point detector to the lower surface of the light introducer; x 0边缘1 The x-axis coordinate when Edge 1 point is at zero position, x 0边缘3 The x-axis coordinate when Edge 3 point is at zero position, h 边缘1 The distance from the photosensitive surface of Edge 1 point detector to the lower surface of the light introducer, h 边缘3 The distance from the photosensitive surface of Edge 3 point detector to the lower surface of the light introducer; y 0边缘2 The y-axis coordinate when Edge 2 point is at zero position, y 0边缘4 The y-axis coordinate when Edge 4 point is at zero position, h 边缘2 The distance from the photosensitive surface of Edge 2 point detector to the lower surface of the light introducer, h 边缘4 The distance from the photosensitive surface of Edge 4 point detector to the lower surface of the light introducer, the output angle of the sun sensor is calculated as follows:

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] Under normal circumstances, (α 中心 , β 中心 ) is the output of the sun sensor. To improve reliability, α 中心 , α 边缘1 and α 边缘3 The three angles will be compared and the 2-out-of-3 method is used as the output. Similarly, β 中心 , β 边缘2 and β 边缘4 The three angles will also be compared and the 2-out-of-3 method is used as the output.

[0043] The present invention simplifies the processing circuit by using highly integrated SOC technology, controls the image sensor, acquires images, and preprocesses images by using the logic resources in the SOC, and calculates the two-axis solar angle by using the ARM Cortex-M3 kernel resources in the SOC. Without external RAM devices, ROM, or FLASH devices, the entire SOC processing board is reduced to a size of 30 mm × 30 mm.

[0044] The specific implementation steps of the nano APS sun sensor of the present invention are as follows:

[0045] The first step: Design and process the light introducer. The size of the light introducer substrate glass is Φ10 mm, and the thickness is 0.5 mm. Three layers of films are designed on the upper surface of the light introducer substrate glass. From the glass substrate to the outside, they are the antireflection film, the neutral attenuation film, and the high reflection film. The antireflection film mainly controls the stray light reflected inside the film layer and on the surface of the image sensor. The neutral attenuation film realizes the neutral attenuation of the sunlight intensity, and the attenuation coefficient is 1 / 15000. The high reflection film mainly completes the reflection of the sunlight, reduces the incident light intensity, and lowers the surface temperature of the light introducer. A narrowband attenuation film and an antireflection film are designed on the lower surface of the light introducer substrate glass. The passband of the narrowband attenuation film is 800 nm ± 5 nm. The "cross" light slit is engraved on the antireflection film, and the width of the light slit is 11 um.

[0046] The second step: Design and process the SOC processing board. As Figure 4 shown in the SOC processing board schematic diagram, the board includes an image sensor, an SOC device, an RS422 interface device, and four internal power conversion DC-DCs. The image sensor selects the MT9P031 of Onsemi, the SOC device selects the M2S025 of Microsemi, the RS422 interface device selects the SN65HVD379 of TI, and the DC-DC selects the TPS82130 of TI. The RC circuit and the 74LVC2G14 inverter are used to power on and reset the SOC device.

[0047] The third step: Design the main structure. As Figure 5 shown in the design of the main structure of the nano APS sun sensor, the body size is 35 mm × 35 mm × 15 mm, and the entire main structure adopts an integrated structure design except for the rear cover.

[0048] The fourth step: Assemble the whole machine. Bond the reference mirror and the light introducer to the main structure, install the SOC processing board on the main structure, and adjust the position of the circuit board. As Figure 6 shown, control the deviation between the x normal of the reference mirror and the u direction of the image sensor to be less than 1 arc minute, and control the deviation between the y normal of the reference mirror and the v direction of the image sensor to be less than 1 arc minute. Here, the u and v directions of the image sensor are the row and column directions, and the x and y normals of the reference mirror are the normal directions of the two surfaces of the reference mirror.

[0049] Step 5: Calibrate the whole machine. Install the assembled nano APS sun sensor under the turntable and solar simulator. The SOC processing board uses the calibration fields of the turntable and solar simulator to determine the x of the nano APS sun sensor 0中心 , y 0中心 , h 中心 , x 0边缘1 , x 0边缘3 , h 边缘1 , h 边缘3 , y 0边缘2 , y 0边缘4 , h 边缘2 , and h 边缘4 , and use the previous formula to obtain α 中心 , α 边缘1 , α 边缘3 , β 中心 , β 边缘2 , and β 边缘4 , α 中心 , α 边缘1 , and α 边缘3 . The three angles will be compared. If the deviation of the three angles is less than 0.03°, the average value of the three angles will be used as the final output of the product. If the deviation of one of the three angles exceeds 0.03°, the average of the remaining two will be used as the final output. If the mutual deviations of the three angles all exceed 0.03°, the central angle will be directly used as the output. For β 中心 , β 边缘2 , and β 边缘4 , the same method of taking two out of three will be used as the final output for the three angles.

[0050] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention all fall within the protection scope of the technical solution of the present invention.

[0051] The parts not detailed in the present invention belong to the common general knowledge of those skilled in the art.

Claims

1. A nano-type APS sun sensor, characterized in that Including: A light introducer, an SOC processing board, a main body structure, and a reference mirror; Among them, the light introducer, the SOC processing board, and the reference mirror are installed on the main body structure; the reference mirror is used to represent the body coordinate system of the nano-type APS sun sensor; the light introducer uses a cross-shaped light slit to achieve the attenuation of sunlight intensity and the introduction of sunlight, and the SOC processing board realizes photoelectric conversion, image acquisition, and image processing, and outputs the sun azimuth information through an interface; The SOC processing board includes an image sensor, an SOC device, an RS422 interface device, and an internal power conversion DC-DC; The internal power conversion DC-DC realizes the conversion of an external 5V power supply into 3.3V, 1.5V, and 2.8V to supply power to the SOC device and the image sensor; the SOC device has built-in logic resources to realize the control of the image sensor, image acquisition, and extraction of the sun bright spot, and the SOC device has built-in ARM Cortex-M3 core resources to realize the calculation of the two-axis sun angle; The power-on reset is realized by using an RC circuit and a 74LVC2G14 inverter and is used for the external power-on reset of the SOC device; The ARM Cortex-M3 core resources use the center point of the cross-shaped light slit to calculate the sun angles of two axes, and use the four edge points to assist in the calculation of the single-axis sun angle. When the light slit is contaminated, the two-axis sun angles are output respectively through the four edge points; (x 中心 , y 中心 ) can be used as the center point to extract coordinates. x 边缘1 and x 边缘3 are the x-axis coordinates extracted for Edge 1 and Edge 3. y 边缘2 and y 边缘4 are the y-axis coordinates extracted for Edge 2 and Edge 4. x 0中心 is the x-axis coordinate when the center point is at zero position, and y 0中心 is the y-axis coordinate when the center point is at zero position. h 中心 is the distance from the photosensitive surface of the center point detector to the lower surface of the light introducer; x 0边缘1 is the x-axis coordinate when Edge 1 point is at zero position, and x 0边缘3 is the x-axis coordinate when Edge 3 point is at zero position. h 边缘1 is the distance from the photosensitive surface of Edge 1 point detector to the lower surface of the light introducer, and h 边缘3 is the distance from the photosensitive surface of Edge 3 point detector to the lower surface of the light introducer; y 0边缘2 is the y-axis coordinate when Edge 2 point is at zero position, and y 0边缘4 is the y-axis coordinate when Edge 4 point is at zero position. h 边缘2 is the distance from the photosensitive surface of Edge 2 point detector to the lower surface of the light introducer, and h 边缘4 is the distance from the photosensitive surface of Edge 4 point detector to the lower surface of the light introducer. The output angle of the sun sensor is calculated as follows: The two-axis sun angles calculated using the center point of the cross-shaped light slit are compared with the coaxial sun angles calculated using the edge points respectively. If the deviation of the three angles is less than 0.03°, the average value of the three angles is used as the final output. If one of the deviations of the three angles exceeds 0.03°, the remaining two are averaged as the final output. If the mutual deviations of the three angles all exceed 0.03°, the central angle is directly used as the output.

2. The nano APS sun sensor according to claim 1, characterized in that, The light introducer realizes coating and lithography by using MEMS technology.

3. The nano APS sun sensor according to claim 1 or 2, characterized in that: The light introducer designs three layers of films on the upper surface of the substrate glass, which are an antireflection film, a neutral attenuation film, and an antireflection film from the inside to the outside of the glass substrate; A narrowband attenuation film and an antireflection film are designed on the lower surface of the substrate glass, and the cross-shaped light slit is engraved on the antireflection film.

4. The nano APS sun sensor according to claim 3, characterized in that: The antireflection film ensures that the film layer reflectivity is less than 2%, the transmittance of the neutral attenuation film is 1 / 15000, and the passing band of the narrowband attenuation film is 800nm ± 5nm.

5. The nano APS sun sensor according to claim 1, characterized in that: The light slit width range of the cross-shaped light slit is 10um to 12um.

6. The nano APS sun sensor according to claim 1, characterized in that: The deviation between the x normal of the reference mirror and the u direction of the image sensor is less than 1 angular minute, and the deviation between the y normal of the reference mirror and the v direction of the image sensor is less than 1 angular minute.

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