Real-time projection-based quick matching method for features of falling pits

Abstract

The invention discloses a real-time projection-based quick matching method for features of a falling pit. Giving an initial attitude angle, projecting the ground navigation troille to an image plane in real time, and matching the ground navigation troille with a troille extracted from the image plane; in addition, in order to improve the matching correctness and stability, similar triangle matching is adopted in the falling pit matching process, and a matching result is voted. The process can quickly determine the position and attitude of the aircraft and complete an accurate fixed-point landing task.

Description

Technical Field

[0001] The present application relates to the technical field of aircraft navigation, and in particular to a method for rapid crater feature matching based on real-time projection. Background Art

[0002] Craters are common fixed features on the surface of extraterrestrial bodies. During the navigation process of aircraft, they can be regarded as an optical image feature and used to estimate the real-time position and attitude of the aircraft. However, the morphology and relative position of craters are greatly affected by the terrain undulation and attitude. For areas with large terrain undulations or when the aircraft attitude angle is large, the imaging position of craters will also change greatly, which brings great challenges to the correct matching of craters. In addition, when there are too many craters on the surface of extraterrestrial bodies, the matching retrieval process is too inefficient, which will directly affect the timeliness of navigation. Summary of the invention

[0003] In order to solve the problem of fast crater matching in the case of large terrain undulations or large aircraft attitude angles, the present application provides a method for fast crater feature matching based on real-time projection. Given an initial attitude angle, the ground navigation craters are projected onto the image plane in real time and matched with the craters extracted on the image plane. In addition, in order to improve the accuracy and stability of the matching, the crater matching process uses similar triangle matching and votes on the matching results. This process can quickly determine the position and attitude of the aircraft and complete the precise landing mission.

[0004] In a first aspect, a method for rapid crater feature matching based on real-time projection is provided, comprising:

[0005] The sensors on the aircraft collect real-time images of the terrain below the flight path, and use star sensors to obtain attitude data at the corresponding moment;

[0006] Use the crater detection algorithm to detect craters on real-time images and obtain the coordinates of the crater center point;

[0007] The star-sensing attitude data at the corresponding time is used as the prior position attitude, and the XYZ coordinates of the ground navigation crater stored in the hardware are used to project the center point of the crater in the navigation crater library onto the image plane to obtain the position of the navigation crater on the image plane;

[0008] Establish triangle △ABC for any three craters in the navigation crater and the image plane detection crater respectively, and establish the detection crater triangle feature library;

[0009] Determine similar triangles in the navigation crater triangle feature library and the detection crater triangle feature library, determine the corresponding crater matching position based on the optimal matching results corresponding to the similar triangles, and solve to obtain the current position and orbit information of the spacecraft.

[0010] In combination with the first aspect, in certain implementations of the first aspect, the determination of similar triangles in the navigation crater triangle feature library and the detection crater triangle feature library is based on judgment based on similar triangle features.

[0011] In combination with the first aspect, in some implementations of the first aspect, similar triangle features include the cosines of the three interior angles of the triangle, cosA, cosB, and cosC, the ratio of the lengths of the three sides,

[0012] In combination with the first aspect, in certain implementations of the first aspect, determining the corresponding crater matching position according to the optimal matching result corresponding to the similar triangles includes:

[0013] After finding a pair of similar triangles, determine the matching degree between the craters around the triangle of the crater map and the craters around the captured image, and vote once if the match is correct;

[0014] The voting results are counted and the matching pair with the most votes is regarded as the correct match.

[0015] In combination with the first aspect, in certain implementations of the first aspect, determining the degree of matching between the craters around the crater map triangle and the craters around the captured image includes:

[0016] The craters around the crater map triangle are compared with the craters around the captured image by inner and cross products.

[0017] In combination with the first aspect, in some implementations of the first aspect, the inner product and the cross product satisfy:

[0018]

[0019] in, represents the longest side vector of similar triangles, Represents the vector from the centroid of the matching triangle to the mth and nth auxiliary craters, and T5 is the threshold.

[0020] In combination with the first aspect, in some implementations of the first aspect, the method further includes:

[0021] Before detecting extraterrestrial objects, a navigation crater library is established on the ground based on high-precision maps to store the XYZ coordinates and radius information of the craters in the lunar solid system. Before performing a fixed-point landing mission, the navigation crater library is stored on the hardware.

[0022] In a second aspect, a device for rapid matching of crater features based on real-time projection is provided, characterized in that the device is used to execute the method described in any one of the implementation modes in the first aspect above.

[0023] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0024] The present invention proposes a method for rapid matching of crater features based on real-time projection, which projects ground navigation craters onto an image plane in real time and matches them with craters extracted from the image plane. This method can obtain high-precision navigation results quickly and in real time, solving the crater matching problem in situations where the terrain is undulating or the aircraft attitude angle is large, and is novel in engineering implementation methods.

[0025] The present invention proposes a method for fast matching of crater features based on real-time projection, which utilizes prior posture to project the ground crater library onto the image plane in real time. The algorithm design idea is innovative. The method has not been published publicly and cannot be directly obtained from public channels.

[0026] The invention proposes a method for rapid crater feature matching based on real-time projection, which solves the problem of rapid crater matching in the case of large terrain undulation or large aircraft attitude angle. The method has good robustness to terrain undulation and aircraft attitude, and can achieve high accuracy. The measurement system described in the method has high working reliability and high practicality.

[0027] Aiming at the problem of fast crater matching in the case of large terrain undulation or large aircraft attitude angle, the present invention proposes a fast crater feature matching method based on real-time projection; this method can be extended to tasks such as deep space exploration, Mars / Moon exploration navigation, and extraterrestrial landing obstacle avoidance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a method for rapid crater feature matching based on real-time projection provided by the present invention. DETAILED DESCRIPTION

[0029] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention is a method for rapid crater feature matching based on real-time projection for extraterrestrial fixed-point landing missions. The method solves the problem of rapid crater matching in the case of large terrain undulations or large aircraft attitude angles. The ground navigation craters are projected onto the image plane in real time, matched with the craters extracted from the image plane, and the real-time positioning of the aircraft is realized. The measurement system described in the method has high reliability and a wide range of target stars. It can be applied to deep space exploration, Mars / Moon exploration navigation, extraterrestrial landing obstacle avoidance and other tasks.

[0031] The present invention provides a method for rapid crater feature matching based on real-time projection, which comprises the following steps.

[0032] Step 1: The sensor on the aircraft collects real-time images of the terrain below the flight path, and uses star sensors to obtain attitude data at the corresponding moment.

[0033] Step 2: Use the crater detection algorithm to detect craters in the real-time image and obtain the coordinates of the crater center point.

[0034] Step 3: Use the star-sensing attitude data at the corresponding time as the prior position attitude, and use the XYZ coordinates of the ground navigation crater stored in the hardware to project the crater center point in the navigation crater library onto the image plane to obtain the position of the navigation crater on the image plane.

[0035] Before detecting extraterrestrial objects, a navigation crater library can be established on the ground based on high-precision maps to store the XYZ coordinates, radius and other information of the craters in the lunar solid system. Before performing a fixed-point landing mission, the navigation crater library can be stored on the hardware.

[0036] Step 4: Establish triangle △ABC for any three craters in the navigation crater and the image detection crater, establish a detection crater triangle feature library, and calculate similar triangle features, including the cosines of the three internal angles of the triangle cosA, cosB, cosC, the ratio of the three side lengths Used for similarity judgment.

[0037] Step 5, take a pair of triangles in the navigation crater triangle feature library and the detection crater triangle feature library for similarity judgment until the similar triangle condition is met, and execute step 5, otherwise the matching fails.

[0038] Step 6, after finding a pair of similar triangles, compare the craters around the triangle in the crater map with the craters around the captured image by inner product and cross product, that is:

[0039]

[0040]

[0041] in, represents the longest side vector of similar triangles, Represents the vector from the centroid of the matching triangle to the mth and nth auxiliary craters. If the inner product and cross product are less than the threshold, the match is considered correct and a vote is performed on the pairing, otherwise return to step 3.

[0042] Step 7: Repeat steps 5-6 until all triangles are matched.

[0043] Step 8: Count the voting results. The matching pair with the most votes is regarded as the correct match. According to the crater matching position, the current position and orbit information of the spacecraft are obtained by solving.

[0044] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A fast crater feature matching method based on real-time projection, characterized in that: include: The sensors on the aircraft collect real-time images of the terrain below the flight path, and use star sensors to obtain attitude data at the corresponding moment; Use the crater detection algorithm to detect craters on real-time images and obtain the coordinates of the crater center point; The star-sensing attitude data at the corresponding time is used as the prior position attitude, and the XYZ coordinates of the ground navigation crater stored in the hardware are used to project the center point of the crater in the navigation crater library onto the image plane to obtain the position of the navigation crater on the image plane; Establish triangle △ABC for any three craters in the navigation crater and the image plane detection crater respectively, and establish the detection crater triangle feature library; Determine similar triangles in the navigation crater triangle feature library and the detection crater triangle feature library, determine the corresponding crater matching position based on the optimal matching results corresponding to the similar triangles, and solve to obtain the current position and orbit information of the spacecraft.

2. The method according to claim 1, characterized in that The determination of similar triangles in the navigation crater triangle feature library and the detection crater triangle feature library is based on the judgment of similar triangle features.

3. The method according to claim 2, characterized in that The characteristics of similar triangles include the cosines of the three internal angles of the triangle, cosA, cosB, and cosC, and the ratio of the lengths of the three sides.

4. The method according to claim 1, characterized in that: Determining the corresponding crater matching position according to the optimal matching result corresponding to the similar triangles includes: After finding a pair of similar triangles, determine the matching degree between the craters around the triangle of the crater map and the craters around the captured image, and vote once if the match is correct; The voting results are counted and the matching pair with the most votes is regarded as the correct match.

5. The method according to claim 4, characterized in that Determining the matching degree between the craters around the crater map triangle and the craters around the captured image includes: The craters around the crater map triangle are compared with the craters around the captured image by inner and cross products.

6. The method according to claim 5, characterized in that The inner product and cross product satisfy: in, represents the longest side vector of similar triangles, Represents the vector from the centroid of the matching triangle to the mth and nth auxiliary craters, and T5 is the threshold.

7. The method according to claim 1, characterized in that The method further comprises: Before detecting extraterrestrial objects, a navigation crater library is established on the ground based on high-precision maps to store the XYZ coordinates and radius information of the craters in the lunar solid system. Before performing a fixed-point landing mission, the navigation crater library is stored on the hardware.

8. A crater feature rapid matching device based on real-time projection, characterized in that: The device is used to perform the method according to any one of claims 1 to 7.

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