阅读说明：本技术 一种大平面激光三维成像质量检校场及其设计方法 (Large-plane laser three-dimensional imaging quality calibration field and design method thereof ) 是由 童小华 谢欢 刘世杰 许雄 魏超 金雁敏 柳思聪 王超 陈鹏 冯永玖 叶真 于 2021-08-31 设计创作，主要内容包括：本发明涉及一种大平面激光三维成像质量检校场及其设计方法,该检校场包括多个用于获取激光波束成像的大平面高平整度检校靶板,按给定布置方案进行布设；所述每个检校靶板包括多个用于调整局部平整度的靶板面调节器；所述方法包括：靶板基准平面参数获取、激光器三维成像点云获取、误差校验和质量精度评定。与现有技术相比,本发明可提高激光器三维成像质量精度,满足着陆区快速建模与障碍物识别的需求,为行星探测着陆器安全着陆提供支撑。(The invention relates to a large-plane laser three-dimensional imaging quality calibration field and a design method thereof, wherein the calibration field comprises a plurality of large-plane high-flatness calibration target plates for obtaining laser beam imaging, and the large-plane high-flatness calibration target plates are distributed according to a given arrangement scheme; each calibration target plate comprises a plurality of target plate surface adjusters for adjusting local flatness; the method comprises the following steps: acquiring parameters of a reference plane of a target plate, acquiring a laser three-dimensional imaging point cloud, checking errors and evaluating quality precision. Compared with the prior art, the method can improve the three-dimensional imaging quality precision of the laser, meet the requirements of rapid modeling and obstacle identification of the landing zone, and provide support for safe landing of the planet detection lander.)

1. A large-plane laser three-dimensional imaging quality calibration field is characterized in that the quality calibration field comprises a plurality of large-plane high-flatness calibration target plates for obtaining laser beam imaging, and the large-plane high-flatness calibration target plates are distributed according to a given arrangement scheme; each of the calibration target plates includes a plurality of target plate surface conditioners for adjusting local flatness.

2. The large-plane laser three-dimensional imaging quality calibration field according to claim 1, wherein the calibration target plate is supported by a steel frame, and the steel frame is a keel frame welded by a square steel pipe.

3. The large-plane laser three-dimensional imaging quality calibration field according to claim 2, wherein the keel frame comprises a plurality of small frame units, and the calibration target plate is fixedly connected with the keel frame by utilizing a plurality of steel plate surfaces and small frame unit supporting points.

4. The large-plane laser three-dimensional imaging quality calibration field according to claim 3, wherein the target plate surface regulator is placed at a small frame unit dividing point of the keel frame.

5. The large-plane laser three-dimensional imaging quality calibration field according to claim 3, wherein the keel frame adopts a square steel tube as an inclined support.

6. The large-plane laser three-dimensional imaging quality calibration field according to claim 1, wherein the reference surface of the calibration target plate is coated with a calibration target plate layer for simulating lunar soil reflectivity.

7. The large-plane laser three-dimensional imaging quality calibration field according to claim 1, wherein the arrangement scheme of the calibration target plate comprises: in the vertical laser imaging direction, different imaging distances are designed, and the depth of a laser imaging view field is improved; meanwhile, a plurality of stepped platforms are designed, the platform elevation change of the arrangement of the calibration target plate is increased, and the vertical imaging view field range is expanded.

8. The large-plane laser three-dimensional imaging quality calibration field according to claim 3, wherein the arrangement scheme of the calibration target plate comprises: the keel frame base is provided with a steering shaft and is provided with a fixing pile, part of the checking target plate is designed with a vertical inclination angle and an observation direction included angle, and a multi-normal plane checking reference is constructed by adopting a mounting method of different vertical inclination angles and different observation direction included angles.

9. The large-plane laser three-dimensional imaging quality calibration field according to claim 1, wherein the arrangement scheme of the calibration target plate comprises: the target correcting plates are fixedly connected in pairs and form a set included angle, and the constraint of the geometric vector characteristics of the line and the surface is increased.

10. A design method of a large-plane laser three-dimensional imaging quality inspection calibration field based on claim 1 is characterized by comprising the following steps:

step S1: acquiring calibration target plate reference plane parameters, constructing an area plane control network by using a high-precision total station, acquiring three-dimensional space coordinates of a target plate reference plane and constructing a multi-normal large plane reference vector matrix;

step S2: the method comprises the steps of obtaining a laser three-dimensional imaging point cloud, namely arranging a laser on an observation holder, designing different observation angles to scan and image a target plate area, and respectively obtaining point cloud data of the target plate area and carrying out segmentation and extraction;

step S3: error checking, namely checking and correcting the laser three-dimensional imaging error by using the area plane control parameter;

step S4: and (4) precision evaluation, namely comparing and analyzing the correction value with a reference value, and evaluating the imaging quality precision.

Technical Field

The invention relates to the field of laser three-dimensional imaging, in particular to a large-plane laser three-dimensional imaging quality calibration field and a design method thereof.

Background

With the development of deep space exploration technology, surface inspection of extraterrestrial celestial bodies, material exploration and construction of moon space stations have been developed in various countries, and safe landing of land vehicles becomes a key task in project success or failure. Aiming at the limitation that the landing process cannot be repeated, the laser three-dimensional imaging technology is selected for landing zone obstacle detection and safe landing point selection of the deep space exploration lander in China, and high credible imaging measurement accuracy is urgently needed. The laser radar (Light Detection and Ranging) has the advantages of high measurement precision, high angular resolution, high measurement speed, strong anti-interference capability and the like, is not influenced by illumination, can quickly detect three-dimensional terrain information of a target area, and is an important means for screening landing areas.

The laser three-dimensional imaging system adopting the multi-beam linear array detection technology combines optical and electronic imaging high-speed echo processing energy, improves the target detection resolution and imaging rate, and can better meet the requirements of rapid modeling and obstacle identification of a preset landing area of a hovering section of a planet lander. Because the three-dimensional imaging system adopts a complex imaging mode of multi-beam two-dimensional galvanometer scanning and sparse point cloud, errors such as distance measurement, angle measurement and the like exist in the measurement process, the detection precision of the obstacle of the landing zone and the reliability of safe landing zone selection are influenced, and effective ground experiments are required to be carried out to carry out imaging quality error analysis and imaging quality improvement.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a high-precision large-plane laser three-dimensional imaging quality calibration field and a design method thereof, so that the three-dimensional imaging precision of a laser is improved, and the requirements of rapid modeling of a landing area and obstacle identification are met.

The purpose of the invention can be realized by the following technical scheme:

according to a first aspect of the present invention, there is provided a large-plane laser three-dimensional imaging quality calibration field, comprising a plurality of large-plane high-flatness calibration target plates for obtaining laser beam imaging, and arranged according to a given arrangement scheme; each of the calibration target plates includes a plurality of target plate surface conditioners for adjusting local flatness.

Preferably, the calibration target plate is supported by a steel frame, and the steel frame is a keel frame welded by a square steel pipe.

Preferably, the keel frame comprises a plurality of small frame units, and the calibration target plate is fixedly connected with the keel frame by utilizing a plurality of steel plate surfaces and small frame unit supporting points.

Preferably, the target deck conditioner is placed at a small frame unit division point of the keel frame.

Preferably, the keel frame adopts a square steel pipe as an inclined support.

Preferably, the reference surface of the calibration target plate is coated with a calibration target plate pattern layer for simulating lunar soil reflectivity.

Preferably, the arrangement scheme of the calibration target plate comprises: in the vertical laser imaging direction, different imaging distances are designed, and the depth of a laser imaging view field is improved; meanwhile, a plurality of stepped platforms are designed, the platform elevation change of the arrangement of the calibration target plate is increased, and the vertical imaging view field range is expanded.

Preferably, the arrangement scheme of the calibration target plate comprises: the keel frame base is provided with a steering shaft and is provided with a fixing pile, part of the checking target plate is designed with a vertical inclination angle and an observation direction included angle, and a multi-normal plane checking reference is constructed by adopting a mounting method of different vertical inclination angles and different observation direction included angles.

Preferably, the arrangement scheme of the calibration target plate comprises: the target correcting plates are fixedly connected in pairs and form a set included angle, and the constraint of the geometric vector characteristics of the line and the surface is increased.

According to a second aspect of the present invention, there is provided a design method based on the above-mentioned large planar laser three-dimensional imaging quality calibration field, the method including the following steps:

step S1: acquiring calibration target plate reference plane parameters, constructing an area plane control network by using a high-precision total station, acquiring three-dimensional space coordinates of a target plate reference plane and constructing a multi-normal large plane reference vector matrix; step S2: the method comprises the steps of obtaining a laser three-dimensional imaging point cloud, namely arranging a laser on an observation holder, designing different observation angles to scan and image a target plate area, and respectively obtaining point cloud data of the target plate area and carrying out segmentation and extraction;

step S3: error checking, namely checking and correcting the laser three-dimensional imaging error by using the area plane control parameter;

step S4: precision evaluation, namely comparing and analyzing the correction value with the reference value, and evaluating the imaging quality precision

Compared with the prior art, the invention has the following advantages:

1) according to the wide-field-of-view multi-normal large-plane laser three-dimensional imaging quality calibration field, the large-plane calibration target plate with high coplanarity precision is built through the high-strength steel plate and the flatness regulator, the three-dimensional imaging quality precision of the laser is improved, the requirements of rapid modeling and obstacle identification of a landing area are met, and support is provided for safe landing of a planet detection lander;

2) the calibration target plate coating which has the wavelength of 1064nm and is similar to the lunar surface environment is designed, and the laser imaging echo signal under the lunar surface weak reflectivity environment is simulated really;

3) the invention designs a method for arranging a multi-step target plate with increasing elevation, expands the range of a vertical view field in laser large view field imaging, and solves the problem of insufficient view field coverage in the vertical direction of laser imaging;

4) the invention designs a target plate arrangement method with different vertical inclination angles and different observation direction included angles to construct a multi-normal plane calibration standard, simulates the influence of a complex lunar surface environment on laser three-dimensional imaging quality, and solves the problem of system error inconsistency in a multi-beam laser imaging view field;

5) the invention is based on a multi-normal large-plane high-precision control network of a multi-forced centering device, sets different observation angles of different laser systems by using a two-dimensional holder, and performs laser three-dimensional imaging quality calibration about 100 meters away from a target plate area.

Drawings

FIG. 1 is a schematic diagram of a wide-field-of-view multi-normal large-plane laser three-dimensional imaging quality inspection field in an embodiment;

FIG. 2 is a laser three-dimensional imaging quality calibration method based on wide field of view and multiple normal large planes.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

In the embodiment, the multi-beam laser three-dimensional imaging sensor with a plurality of laser detection units is adopted, the wide-view-field multi-normal large-plane laser three-dimensional imaging quality calibration field is in a four-layer ladder shape, and 19 target plate reference surfaces with different normal directions are arranged for the calibration of laser three-dimensional imaging quality errors, as shown in fig. 1.

According to a designed calibration scheme, a high-precision total station is used for obtaining plane control parameters of 19 target plates, and three-dimensional imaging of a laser to be calibrated is carried out to obtain point cloud data; the laser three-dimensional imaging quality error is calibrated, the imaging quality precision is evaluated, and the precise measurement of the three-dimensional shape of the large-plane calibration target plate in a wide view field and multiple normal directions can be realized.

The following describes embodiments of the present invention in detail.

1. Design of large-plane high-flatness calibration target plate reference surface

The invention relates to a large-plane target checking plate, in particular to a large-plane target checking plate, which is a key technology for checking the laser three-dimensional imaging quality and aims at solving the problem of sparse point cloud of laser rapid imaging in a lunar soft landing fine obstacle detection scene. The height of the target checking plate is 4 meters, the width of the target checking plate is 2 meters, and all laser beams are ensured to be imaged on the plane of the target plate; for a single target plate, a plurality of target plate surface adjusters are designed, so that the flatness fitting precision of the target plate plane is ensured to be superior to 2mm for a long time. The specific design scheme is as follows:

1.1, designing a steel frame with a grid structure, welding a keel frame by using a large-size and high-thickness square steel pipe, and manufacturing a frame inclined support by using the square steel pipe so as to ensure the overall stability of a target plate supporting structure; the keel frame is divided into a plurality of small units, and a plurality of steel plate surfaces and frame unit supporting points are designed to ensure that the target plate surface is stably connected with the keel frame;

1.2 designing a plurality of steel plate surface connection point regulators based on keel frame unit division points for adjusting the local flatness of the plane of the target plate; according to the building structure load specification (GB5009-2001), by combining the arrangement environment of a calibration yard (roughness B type, wind pressure height change coefficient of 1.0, size coefficient of 2.0, wind gust coefficient of 2.25, 0.55KN/m2 of basic wind pressure in 50 years in a region), the maximum deformation of the plane of the target plate and the keel frame is 1.8mm under the action of the phoenix load, and the requirement of flatness is met. Ensuring that the fitting precision of the large plane flatness of the large plane is superior to 2mm for a long time;

1.3 the spectral analysis of the paint with different gray scales on the target plate plane is carried out by referring to the lunar soil reflectivity, and the calibration target plate coating which is similar to the lunar surface environment and meets the simulation of 1064nm wavelength is designed.

2. Wide-view-field multi-normal calibration target plate arrangement scheme design

The multi-beam laser three-dimensional imaging has systematic errors and different influence degrees to the periphery along the imaging center [4 ]. Aiming at the imaging characteristics, the invention designs a wide-view-field multi-normal arrangement scheme of the calibration target plate, and ensures high credibility of the plane reference of the calibration target plate. The method is characterized in that the method strictly covers the imaging view field range of a laser three-dimensional imaging system of a multi-beam linear array detection technology, the length of a calibration target plate installation area is 60 meters, the width of the calibration target plate installation area is 50 meters, and the specific installation scheme is designed as follows:

2.1 in the direction vertical to the laser imaging, different imaging distances are designed, and the depth of a laser imaging view field is improved; designing a plurality of stepped platforms, increasing the platform elevation change of target plate placement, and expanding the range of vertical imaging view field;

2.2 designing a steering shaft and a mounting fixing pile of a keel frame base, designing vertical inclination angles and observation direction included angles on part of target plates, and constructing a multi-normal plane calibration standard by adopting a mounting method of different vertical inclination angles and different observation direction included angles;

2.3 design the part of target plates are fixedly connected pairwise and form a certain included angle, and the constraint of geometric vector characteristics such as line and surface is increased.

3. Wide-field-of-view-based multi-normal large-plane laser three-dimensional imaging quality calibration scheme

Considering the correlation of calibration parameters among system parameters of the laser radar and between the system parameters and external orientation elements, integrating the influences of the distance between a laser and a target plate, the observation angle and the like, and designing a laser three-dimensional imaging quality calibration scheme based on a wide view field multiple normal direction large plane as shown in fig. 2:

s1, acquiring reference plane parameters: constructing an area plane control network by using a high-precision total station, acquiring high-precision three-dimensional space coordinates of a target plate datum plane, and constructing a multi-normal large plane datum vector matrix;

s2, acquiring the laser three-dimensional imaging point cloud: arranging a laser on an observation holder, designing different observation angles to scan and image a target plate area, and respectively acquiring point cloud data of the target plate area and performing segmentation and extraction;

s3, error checking: checking and correcting the laser three-dimensional imaging error by using the area plane control parameter;

s4, precision assessment: comparing and analyzing the correction value with the reference value, and evaluating the imaging quality precision

According to the novel design method of the wide-field multi-normal large-plane laser three-dimensional imaging quality calibration field, a large-plane calibration target plate with high coplanarity precision is built through a high-strength steel plate and a flatness regulator, the calibration target plate coating layer similar to lunar soil reflectivity is designed to simulate the lunar surface weak reflectivity laser imaging environment, a multi-step target plate arranging method with gradually increased elevations is designed to expand the imaging vertical field of view, the target plate arranging methods with different vertical dip angles and different observation direction included angles are designed to construct the multi-normal plane calibration standard, and the influence of the complex lunar surface environment on the laser three-dimensional imaging quality is simulated. The invention can improve the three-dimensional imaging quality precision of the laser, meet the requirements of rapid modeling and obstacle identification of the landing zone and provide support for safe landing of the planet detection lander.

While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.