阅读说明：本技术 一种基于机器人编队的太空垃圾智能清理系统 (Space rubbish intelligent cleaning system based on robot formation ) 是由 朱艳萍 高伟杰 应笑天 卞方军 曹黎明 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种基于机器人编队的太空垃圾智能清理系统,包括多个呈编队飞行或者编队作业状态的机器人卫星；每个机器人卫星均包括机器人本体,以及搭载在机器人本体上的通信模块、电磁吸附模块、激光烧蚀模块、能源模块、控制模块、探测模块和微处理器。本发明通过MIMO雷达探测目标区域的太空垃圾,此后经过目标识别、跟踪、航迹管理等相关处理后将信息传回处理器,同时对目标尺寸进行识别。垃圾清理通过编队机器人处理,可集合协同回收较大尺寸太空垃圾,任务完成后进行编队队形重构,返回巡航轨道。本智能太空垃圾清理系统考虑了不同尺寸范围的太空垃圾,灵活组合,降低了自身损毁率,提高了单次轨道周期碎片清理的效率。(The invention discloses a space rubbish intelligent cleaning system based on robot formation, which comprises a plurality of robot satellites in a formation flying or formation working state; each robot satellite comprises a robot body, and a communication module, an electromagnetic adsorption module, a laser ablation module, an energy module, a control module, a detection module and a microprocessor which are carried on the robot body. The space junk in the target area is detected through the MIMO radar, and then the information is transmitted back to the processor after relevant processing such as target identification, tracking, track management and the like, and the size of the target is identified. The garbage cleaning is processed by the formation robot, the garbage can be integrated to cooperatively recover large-size space garbage, the formation is reconstructed after the task is completed, and the garbage returns to the cruise track. The intelligent space debris cleaning system considers space debris in different size ranges, is flexible in combination, reduces the self-damage rate, and improves the efficiency of cleaning debris in a single orbit period.)

1. A space junk intelligent cleaning system based on robot formation is characterized by comprising a plurality of robot satellites in a formation flying or formation operation state; each robot satellite comprises a robot body, and a communication module, an electromagnetic adsorption module, a laser ablation module, an energy module, a control module, a detection module and a microprocessor which are carried on the robot body;

the energy module is used for providing power for the flying and the operation of the robot satellite; the communication module is used for duplex communication with pilots or satellites in the formation;

the detection module comprises an MIMO radar and is used for positioning and tracking debris on the space orbit; the detection modules of all the robot satellites form an integral MIMO radar detection system, and the MIMO radar detection system adopts a distributed processing mode to ensure that each robot satellite respectively undertakes partial tasks of detecting, collecting, calculating and evaluating a cleaning target;

the microprocessor receives the positioning and tracking information sent by the detection module, evaluates the cleaning target, and allocates a plurality of robot satellites matched with the cleaning target to coordinate and cooperate to complete the cleaning task; each robot satellite calls an electromagnetic adsorption module to adsorb space fragments according to an instruction sent by a microprocessor, a laser ablation module is adopted to vaporize the space fragments with the diameter less than or equal to 10cm, the formation is adjusted for the space fragments with the diameter more than 10cm, and the space fragments are pushed into an atmospheric orbit by cooperating with other robot satellites;

the microprocessor controls robot formation by adopting different control strategies according to the working state of the robot satellite:

when the robot satellite is in a mission-free cruising state, the microprocessor takes the longest endurance as a constraint condition and adopts a pulse control strategy or a threshold control strategy to enable the robot satellite to perform flying-around motion by taking the main satellite as a center;

when the robot satellite is in a cooperative working state, the microprocessor takes the highest formation accuracy as a constraint condition, adopts a continuous micro-thrust strategy, enables part or all of the robot satellites executing the cleaning task to respectively perform independent motion, and returns to the circular orbit to continue flying around after the task is finished;

the control module consists of an air storage tank and an operating system, and completes the adjustment of the robot satellite orbit and the coordination control during the task under the instruction of the microprocessor.

2. A robot formation-based space junk intelligent cleaning system as claimed in claim 1 wherein said robot satellites are in laser communication with pilots or other robot satellites in the formation in half duplex communication;

the communication module comprises an optical platform, an ATP unit, a communication unit and a laser range finder; the optical platform is used for sending and receiving signals, and the ATP unit is used for capturing, tracking and aligning the light beam; the communication unit and the laser range finder are used for generating signals and correcting errors; the communication system of the communication module adopts IM/DD, the modulation mode is OOK, and the antenna is in a transmission mode.

3. A space debris intelligent cleaning system based on robot formation as claimed in claim 2, wherein the robot satellites measure the relative distance and velocity between the robot satellites by using a laser range finder and optimize the measured values by using a particle filtering method.

4. A robot-formation-based space junk intelligent cleaning system according to claim 1 wherein the transmit antenna arrays or antenna units of the MIMO radar detection system are sparsely distributed on the robot satellite;

the MIMO radar detection system transmits mutually orthogonal signal waveforms s through M transmitting stations₁(t),s₂(t),…,s_M(t) transmittedAfter the radar signal irradiates a detection target, N receiving stations receive echo signals, each receiving station adopts M matched filter groups, M transmitting signals are separated after filtering and matching of the echo signals, and MN groups of different receiving and transmitting channels are obtained in the N receiving stations;

after the MIMO radar detection system transmits electromagnetic wave signals, the electromagnetic wave signals are reflected by a detection target and received by a receiver through a radar, analog signals received by an antenna pass through a band-pass filter, after noise and noise are removed in the receiver, the analog signals are converted into digital signals through A/D conversion, output is obtained through matched filtering, then phase-shift addition is carried out on output results, digital beam forming is carried out, and receiving beams are formed in a certain direction; and finally, after pulse accumulation, constant false alarm detection and moving target detection, obtaining motion information of the target including distance, speed, azimuth angle and pitch angle according to the processing result.

5. A robot formation-based space junk intelligent cleaning system in accordance with claim 4 wherein the MIMO radar detection system is further configured to track and filter the cleaning target, estimate the motion state of the cleaning target, and display the motion track of the cleaning target, comprising the steps of:

the radar receiving end receives a target echo, the target position and the motion state are calculated through a target detection and target tracking algorithm, and the relation between each measurement and a plurality of possible target sets is established through association processing; estimating the motion parameters of a maneuvering or non-maneuvering target by using a filtering and predicting algorithm to obtain a target motion track; and tracking and filtering the same target measurement value set to estimate a track formed by the target motion state values.

6. A robot formation-based space junk intelligent cleaning system as claimed in claim 1 wherein when the robot satellite is in an mission-free cruise condition, said microprocessor counteracts the effect of partial non-linear terms on formation accuracy by changing initial conditions, said non-linear terms including fixed error terms, long term terms and periodic terms.

7. A robot formation-based space junk intelligent cleaning system in claim 1 wherein for a robot satellite in an mission-free cruise state, when the formation accuracy requirement is lower than a preset accuracy threshold, a threshold control strategy is adopted: selecting an error threshold D, and igniting the engine by a control module to adjust the track of the robot satellite to which the engine belongs only when the formation form error exceeds the threshold D; otherwise, adopting a pulse control strategy: and periodically applying a pulse once to control an engine of the robot satellite, wherein the pulse control quantity is obtained by calculating by adopting a quadratic optimal control algorithm, and the pulse control quantity is related to the relative motion state of the surrounding satellite and the reference satellite during sampling.

8. A robot formation-based space junk intelligent cleaning system in accordance with claim 7 wherein the process of the control module controlling the formation of the robot satellites comprises the steps of:

s1, judging whether a cleaning task is received, if so, turning to the step S2, otherwise, turning to the step S4;

s2, receiving target information by adopting a continuous micro-thrust control model, estimating the orbit error, and correcting the flight orbit according to the estimation result until the cleaning task is completed;

s3, relative navigation among the satellites is carried out, if a team reconstruction instruction is received, a continuous thrust control mode is maintained according to the team reconstruction instruction until the track adjustment is completed, the self working mode is switched to a no-task state, and the step S1 is entered; otherwise, returning to the circular orbit to continue flying around, switching the working mode of the circular orbit into a task-free state, and entering step S1;

s4, adopting a pulse thrust control model, receiving the measurement parameters, judging whether the error threshold is met, and if the error threshold is met, entering the step S5;

and S5, periodically applying a pulse control to the engine of the robot satellite, receiving the measurement parameters, judging whether the track regresses, if so, returning to the step S1, and if not, returning to the step S4.

9. A space debris intelligent cleaning system based on robot formation as claimed in claim 1, wherein when the robot satellite is in a cooperative working state, the microprocessor combines the engine operation parameters of the robot satellite to construct an electric propulsion model with extremely low thrust, and the influence of micro-perturbation force including earth oblateness perturbation, solar pressure perturbation and atmospheric resistance perturbation is continuously eliminated in the whole cleaning task execution period.

10. A robot formation-based space junk intelligent cleaning system as claimed in claim 1 wherein said microprocessor reconfiguring the formation comprises the steps of:

detecting the positions of other robot satellites in the formation through the MIMO radar;

deducing a formation satellite motion equation represented by the relative orbit number between the main satellite and the satellite according to the coordinate conversion relation between the relative orbit number and the relative position and speed between the robot satellites under the orbit coordinate system;

based on a formation satellite motion equation, according to a Gaussian differential equation, deducing a small increment relative orbit root equation, establishing a relation between the in-orbit and out-orbit control force of the satellite and the relative motion between the satellites, and dividing formation reconstruction into two reconstruction conditions of in-orbit plane and out-orbit plane;

deducing to obtain the mutual relation between the inclination angle of the track and the combined external force outside the ascension point and the plane of the track;

deducing to obtain the action condition of the track combined external force on the semimajor axis, the eccentricity, the amplitude angle of the perigee and the plano-perigee angle;

obtaining the relation between the relative orbit number among satellites and the orbit pulse control force;

and selecting adaptive track pulses according to the requirement of the space task to realize the optimal or suboptimal formation reconstruction track.

Technical Field

The invention relates to the technical field of space garbage cleaning, in particular to a space garbage intelligent cleaning system based on robot formation.

Background

Space debris generally moves at a speed of 7-8 kilometers per second on a low earth orbit with the height of 300-450 kilometers, and moves at a high speed of 3 kilometers per second on an earth static orbit with the height of 36000 kilometers, and the relative speed can reach more than 10 kilometers per second when colliding according to the inclination angle of the orbit, so that the space debris has great destructive power. If the space garbage collides with an artificial satellite, a manned spacecraft or an international space station in operation, the life of equipment and even astronauts can be endangered, the space garbage with the diameter of 10cm can be completely destroyed according to calculation, and the space garbage with the size of several millimeters can possibly make the space garbage incapable of continuously working. Space refuse has become an international problem, and since the 50 s of the last 20 th century, the super kingdom entered the military universe, mankind has launched space rockets for more than four thousand times. According to incomplete statistics, the existing space garbage with the diameter larger than 10cm in the space is more than nine thousand, the existing space garbage with the diameter larger than 1.2cm is more than 10 ten thousand, and the number of the paint chips, the dust particles of solid propellant and other micro particles can be millions. These space debris are extremely fast in flight speed (6-7 km/sec), extremely powerful in lethality: a piece of space garbage with the weight of 10 grams is collided with a satellite, namely two cars with the speed of 100 km/h are collided with each other, and the satellite can be punctured or directly destroyed within 1.5 seconds. By 2016, 11 months, approximately 1 million pieces of space debris move around the earth, of which 27000 pieces, more than 10 centimeters in diameter, are tracked by the united states space agency and department of defense. The running speed of each piece of space garbage reaches 28000 km/h. Therefore, the space garbage cleaning is not slow, but most of the current space garbage cleaning schemes focus on the working performance and method of the single robot, and neglect the idea of cooperative cooperation.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the space garbage intelligent cleaning system based on the robot formation, which has a simple structure, reduces the industrial production cost, simultaneously realizes overall planning and improves the fragment cleaning efficiency of a single orbit period.

In order to achieve the purpose, the invention adopts the following technical scheme:

the embodiment of the invention provides a space rubbish intelligent cleaning system based on robot formation, which comprises a plurality of robot satellites in a formation flying or formation operation state; each robot satellite comprises a robot body, and a communication module, an electromagnetic adsorption module, a laser ablation module, an energy module, a control module, a detection module and a microprocessor which are carried on the robot body;

the energy module is used for providing power for the flying and the operation of the robot satellite; the communication module is used for duplex communication with pilots or satellites in the formation;

the detection module comprises an MIMO radar and is used for positioning and tracking debris on the space orbit; the detection modules of all the robot satellites form an integral MIMO radar detection system, and the MIMO radar detection system adopts a distributed processing mode to ensure that each robot satellite respectively undertakes partial tasks of detecting, collecting, calculating and evaluating a cleaning target;

the microprocessor receives the positioning and tracking information sent by the detection module, evaluates the cleaning target, and allocates a plurality of robot satellites matched with the cleaning target to coordinate and cooperate to complete the cleaning task; each robot satellite calls an electromagnetic adsorption module to adsorb space fragments according to an instruction sent by a microprocessor, a laser ablation module is adopted to vaporize the space fragments with the diameter less than or equal to 10cm, the formation is adjusted for the space fragments with the diameter more than 10cm, and the space fragments are pushed into an atmospheric orbit by cooperating with other robot satellites;

the microprocessor controls robot formation by adopting different control strategies according to the working state of the robot satellite:

when the robot satellite is in a mission-free cruising state, the microprocessor takes the longest endurance as a constraint condition and adopts a pulse control strategy or a threshold control strategy to enable the robot satellite to perform flying-around motion by taking the main satellite as a center;

when the robot satellite is in a cooperative working state, the microprocessor takes the highest formation accuracy as a constraint condition, adopts a long-term continuous control strategy, enables part or all of the robot satellites executing the cleaning task to respectively perform independent motion, and returns to the circular orbit to continue flying around after the task is finished;

the control module consists of an air storage tank and an operating system, and completes the adjustment of the robot satellite orbit and the coordination control during the task under the instruction of the microprocessor.

Further, the robot satellite adopts a laser communication mode and adopts half-duplex communication with pilots or other robot satellites in formation;

the communication module comprises an optical platform, an ATP unit, a communication unit and a laser range finder; the optical platform is used for sending and receiving signals, and the ATP unit is used for capturing, tracking and aligning the light beam; the communication unit and the laser range finder are used for generating signals and correcting errors; the communication system of the communication module adopts IM/DD, the modulation mode is OOK, and the antenna is in a transmission mode.

Further, the robot satellite measures the relative distance and speed between the robot satellites by adopting a laser range finder, and optimizes the measured value by adopting a particle filtering method.

Further, the transmitting antenna arrays or antenna units of the MIMO radar detection system are sparsely distributed on the robot satellite;

the MIMO radar detection system transmits mutually orthogonal signal waveforms s through M transmitting stations₁(t),s₂(t),…,s_M(t), after the transmitted radar signal irradiates a detection target, N receiving stations receive echo signals, each receiving station adopts M matched filter banks, M transmitting signals are separated after filtering and matching of the echo signals, and different transmitting and receiving channels of MN groups are obtained in the N receiving stations in total;

after the MIMO radar detection system transmits electromagnetic wave signals, the electromagnetic wave signals are reflected by a detection target and received by a receiver through a radar, analog signals received by an antenna pass through a band-pass filter, after noise and noise are removed in the receiver, the analog signals are converted into digital signals through A/D conversion, output is obtained through matched filtering, then phase-shift addition is carried out on output results, digital beam forming is carried out, and receiving beams are formed in a certain direction; and finally, after pulse accumulation, constant false alarm detection and moving target detection, obtaining motion information of the target including distance, speed, azimuth angle and pitch angle according to the processing result.

Further, the MIMO radar detection system is further configured to track and filter the cleaning target, estimate a motion state of the cleaning target, and display a motion trajectory of the cleaning target, and includes the following steps:

the radar receiving end receives a target echo, the target position and the motion state are calculated through a target detection and target tracking algorithm, and the relation between each measurement and a plurality of possible target sets is established through association processing; estimating the motion parameters of a maneuvering or non-maneuvering target by using a filtering and predicting algorithm to obtain a target motion track; and tracking and filtering the same target measurement value set to estimate a track formed by the target motion state values.

Further, when the robot satellite is in the mission-free cruising state, the microprocessor offsets the influence of partial non-linear terms including a fixed error term, a long term and a period term on the formation accuracy by changing the initial condition.

Further, for the robot satellite in the mission-free cruising state, when the precision requirement of the formation is lower than a preset precision threshold, a threshold control strategy is adopted: selecting an error threshold D, and igniting the engine by a control module to adjust the track of the robot satellite to which the engine belongs only when the formation form error exceeds the threshold D; otherwise, adopting a pulse control strategy: and periodically applying a pulse once to control an engine of the robot satellite, wherein the pulse control quantity is obtained by calculating by adopting a quadratic optimal control algorithm, and the pulse control quantity is related to the relative motion state of the surrounding satellite and the reference satellite during sampling.

Further, the process of the control module for controlling the formation of the robot satellites comprises the following steps:

s1, judging whether a cleaning task is received, if so, turning to the step S2, otherwise, turning to the step S4;

s2, receiving target information by adopting a continuous micro-thrust control model, estimating the orbit error, and correcting the flight orbit according to the estimation result until the cleaning task is completed;

s3, relative navigation among the satellites is carried out, if a team reconstruction instruction is received, a continuous thrust control mode is maintained according to the team reconstruction instruction until the track adjustment is completed, the self working mode is switched to a no-task state, and the step S1 is entered; otherwise, returning to the circular orbit to continue flying around, switching the working mode of the circular orbit into a task-free state, and entering step S1;

s4, adopting a pulse thrust control model, receiving the measurement parameters, judging whether the error threshold is met, and if the error threshold is met, entering the step S5;

and S5, periodically applying a pulse control to the engine of the robot satellite, receiving the measurement parameters, judging whether the track regresses, if so, returning to the step S1, and if not, returning to the step S4.

Further, when the robot satellite is in a cooperative working state, the microprocessor combines engine operation parameters of the robot satellite to construct an electric propulsion model with extremely small thrust, and continuously eliminates the influence of micro-perturbation force including earth oblateness perturbation, sunlight pressure perturbation and atmospheric resistance perturbation in the whole cleaning task execution period.

Further, the process of reconstructing the formation by the microprocessor comprises the following steps:

detecting the positions of other robot satellites in the formation through the MIMO radar;

deducing a formation satellite motion equation represented by the relative orbit number between the main satellite and the satellite according to the coordinate conversion relation between the relative orbit number and the relative position and speed between the robot satellites under the orbit coordinate system;

based on a formation satellite motion equation, according to a Gaussian differential equation, deducing a small increment relative orbit root equation, establishing a relation between the in-orbit and out-orbit control force of the satellite and the relative motion between the satellites, and dividing formation reconstruction into two reconstruction conditions of in-orbit plane and out-orbit plane;

deducing to obtain the mutual relation between the inclination angle of the track and the combined external force outside the ascension point and the plane of the track;

deducing to obtain the action condition of the track combined external force on the semimajor axis, the eccentricity, the amplitude angle of the perigee and the plano-perigee angle;

obtaining the relation between the relative orbit number among satellites and the orbit pulse control force;

and selecting adaptive track pulses according to the requirement of the space task to realize the optimal or suboptimal formation reconstruction track.

The invention has the beneficial effects that:

the invention comprehensively utilizes the prior art to realize intelligent classification and treatment of space garbage, detects the size, the quantity and the motion state of space debris through a radar, and totally distributes robot formation for treatment; the space garbage cleaning working area is enlarged, and the cleaning efficiency of the satellite in a single orbit running period is improved. Under the constraint condition of realizing the classification treatment of the space debris, the cleaning system has the advantages of simpler structure, mature technology, low cost, low energy consumption and strong capturing capability. The upper limit of the target quality and the volume processed by the cleaning system is positively correlated with the number of the task robots, and the upper limit is higher when the number is more.

Drawings

Fig. 1 is a structural block diagram of an intelligent space junk cleaning system based on robot formation according to an embodiment of the invention.

Fig. 2 is a flowchart of the operation of the electromagnetic adsorption module according to the embodiment of the present invention.

Fig. 3 is a system block diagram of an energy module of an embodiment of the invention.

Fig. 4 is a schematic diagram of a communication module of an embodiment of the present invention.

FIG. 5 is a flowchart of the operation of the detection module of an embodiment of the present invention.

FIG. 6 is an organizational chart of a detection module according to an embodiment of the invention.

FIG. 7 is a flowchart of the operation of an intelligent space junk cleaning system of an embodiment of the present invention.

Fig. 8 is a flowchart of MIMO radar operation according to an embodiment of the present invention.

Fig. 9 is a schematic view of a flying formation configuration of an embodiment of the present invention.

FIG. 10 is a flow chart of flight formation control according to an embodiment of the present invention.

Detailed Description

The present invention will now be described in further detail with reference to the accompanying drawings.

It should be noted that the terms "upper", "lower", "left", "right", "front", "back", etc. used in the present invention are for clarity of description only, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not limited by the technical contents of the essential changes.

Fig. 1 is a structural block diagram of an intelligent space junk cleaning system based on robot formation according to an embodiment of the invention. Referring to fig. 1, the space debris intelligent cleaning system comprises a plurality of robot satellites in a formation flying or formation working state; each robot satellite comprises a robot body, and a communication module, an electromagnetic adsorption module, a laser ablation module, an energy module, a control module, a detection module and a microprocessor which are carried on the robot body.

After the robot formation is launched into a preset orbit, the control system searches for the orbit environment through the detection module, the computer predicts the movement track of the garbage through the MIMO radar of the detection module, defines the size of the garbage at the same time, calculates the required number of small satellites according to the size and the speed of the threat object if the threat object exists, allocates, collaboratively performs different treatments, and treats the threat object garbage through the electromagnetic adsorption device. FIG. 7 is a flowchart of the operation of an intelligent space junk cleaning system of an embodiment of the present invention.

Energy source module

The energy module is used for providing power for the flying and the operation of the robot satellite. Fig. 3 is a system block diagram of an energy module of an embodiment of the invention. The energy module comprises two battery packs, a photovoltaic panel, a power supply controller and an equalizer, wherein the power supply controller can control whether the energy is output or not through output information, the equalizer can reduce the influence of intersymbol interference through the control influence on each frequency component, and the solar battery packs are input to the energy storage battery packs to be stored after being converted into the energy of the photovoltaic panel.

(II) communication module

The communication module is used for duplex communication with pilots or satellites in the formation. Fig. 4 is a schematic diagram of a communication module of an embodiment of the present invention.

The robot small satellite adopts a laser communication mode, adopts half-duplex communication with a pilot, and comprises an optical platform, an ATP part, a communication part and a distance measurement part, wherein the optical platform is used for sending and receiving signals, the ATP part is used for capturing, tracking and aligning light beams, and the communication part and the distance measurement part are used for generating signals and correcting errors. The communication system adopts IM/DD, the modulation mode is OOK, the antenna is in a transmission type, in addition, the transmitting light path is composed of a pre-collimating mirror, a dichroic mirror and the like, and the receiving light path is composed of a dichroic mirror, relay optics, a dichroic mirror, an optical filter and the like. The APD high-speed photoelectric detection module integrates an Avalanche Photodiode (APD) with high-speed response and a low-noise amplifier, single-mode/multimode optical fiber coupling input and SMA connector output, and has the characteristics of high gain, high sensitivity, alternating current coupling output, flat gain and the like.

(III) electromagnetic adsorption module and laser ablation module

The electromagnetic adsorption device is electrically connected with a step-up transformer, a rectifier filter, an instruction controller and a high-voltage output device in sequence, and can generate high-voltage static electricity to adsorb surrounding small garbage. Fig. 2 is a flowchart of the operation of the electromagnetic adsorption module according to the embodiment of the present invention. The laser ablation module directly vaporizes small-sized fragments after electrostatic adsorption, and required energy is provided by a photovoltaic panel of the energy module. The electromagnetic adsorption module performs electrostatic attraction adsorption on the space debris in real time according to a control instruction of the microprocessor, performs next processing according to a target condition after adsorption is completed, enters the cabin body to be directly subjected to laser vaporization when the size of the space debris is smaller than or equal to 10cm, and pushes the space debris into an atmosphere track in cooperation with other task units when the size of the space debris is larger than 10 cm. The laser ablation module directly vaporizes small-sized space debris.

In this embodiment, the garbage is cleaned and processed by the formation robot, and each cleaning machine can independently adsorb small space garbage and can collect and cooperatively recover large-size space garbage. The small-size garbage can be directly subjected to laser ablation treatment; and for large-size garbage, the control system allocates unit numbers of estimated quantity to perform tasks by changing the formation after receiving the command, cooperatively transports and pushes the units into the atmosphere for destruction, reconstructs the formation after the tasks are completed, and returns to the cruise track. The intelligent space debris cleaning system considers space debris in different size ranges, is flexible in combination, reduces the self-damage rate, and improves the efficiency of cleaning debris in a single orbit period.

(IV) detection module

FIG. 6 is an organizational chart of a detection module according to an embodiment of the invention. The detection module mainly comprises an MIMO radar which is mainly responsible for positioning and tracking a plurality of targets moving at high speed. The detection modules of all the robot satellites form an integral MIMO radar detection system, the MIMO radar detection system adopts a distributed processing mode, the whole radar system consists of a plurality of constellations, each constellation consists of a plurality of array element robots, each array element robot undertakes detection and collection tasks and partial evaluation, judgment, control and processing calculation tasks, and an inter-satellite link is established by transmitting orthogonal waveform signals and receiving echo signals among units to form an integral body. FIG. 5 is a flowchart of the operation of the detection module of an embodiment of the present invention.

4.1 basic principle

Fig. 8 is a flowchart of MIMO radar operation according to an embodiment of the present invention. The transmit antenna arrays or antenna elements of an aerial distributed MIMO radar system are sparsely distributed in space. The aerial distributed MIMO radar introduces multipath diversity in MIMO communication into radar design, and similar to MIMO communication, the aerial distributed MIMO radar also considers that radar target echoes are integrated by independent statistical echoes and statistical scattered echoes, and different echoes correspond to different independent attenuation paths. The system operation mode is as follows: transmitting mutually orthogonal signal waveforms s by M transmitting stations₁(t),s2(t),…,s_MAnd (t), after the transmitted radar signal irradiates a detection target, receiving echo signals by N receiving stations, wherein each receiving station adopts M matched filter banks, M transmitted signals can be separated after filtering and matching of the echo signals, and different transmitting and receiving channels of MN groups can be obtained in the N receiving stations in total. The method comprises the steps of supposing that after an M-sending N-receiving aerial distributed MIMO radar transmits electromagnetic wave signals, the electromagnetic wave signals are reflected through a detection target and received by a receiver through the radar, analog signals received by an antenna pass through a band-pass filter, after noise and noise are removed in the receiver, the analog signals are converted into digital signals through A/D conversion, then output is obtained through matched filtering, then output results are subjected to phase-shift addition, digital beam forming is carried out, and receiving beams are formed in a certain direction. And after pulse accumulation, constant false alarm detection and moving target detection, motion information of the target, such as distance, speed, azimuth angle and pitch angle, can be obtained according to the processing result.

4.2 target detection

After the distributed MIMO radar experimental system is started up to work, subsequent signals are effectively processed. And the radar receives a target echo signal, performs target detection and extracts the distance, speed and angle information of the target. For the processing flow of extracting the target information of multiple nodes, firstly, the echo of a single node is subjected to digital multi-beam forming, matched filtering separation is carried out on the echo and each transmitting signal, MTD is carried out on each upward beam, then peak phase difference and time delay difference between targets are extracted, beam synthesis between the nodes is carried out, a module is taken, CFAR detection is carried out, whether the target exists or not is judged, as the beam synthesis of multiple nodes is carried out, the side lobe of the target can be detected and the target can be detected in multiple beams, target focusing between the beams is carried out firstly in the beams, then, the angle of the target is measured by using an angle measurement algorithm, and finally, the distance, speed, azimuth angle and pitch angle information of the target are obtained.

4.3 target tracking

The distance, speed and angle measuring values of the target are obtained by the front signal processor and the detector, the target is tracked and filtered at the back, the motion state of the target is estimated, and the motion trail of the target is displayed. The tracking filtering process of the target comprises three main parts, namely data association, tracking filtering and track management.

A. Data association

And when the radar receiving end receives the target return, the target position and the motion state are calculated through a target detection and target tracking algorithm. Data correlation and state estimation are required during the tracking filtering process. The data association technology is used for establishing a relation between a current moment measurement value and a previous moment measurement value so as to judge whether each moment data belongs to the same target. The association process establishes a relationship between each metric and a number of possible target sets.

B. Tracking filtering

The target tracking is to estimate the motion parameters of a maneuvering or non-maneuvering target by using a filtering and predicting algorithm to obtain a target motion track. In the space domain, the target is generally used as a scatterer to perform mathematical modeling on the target, one is to perform modeling on the motion state of the target, and the other is to perform observation modeling on the state of the target. And after the mathematical modeling is finished, estimating the target state according to a filtering algorithm.

C. Track management

The track is formed by carrying out tracking filtering on the same target measurement value set and estimating a target motion state value. Because the existing radar detection environment is increasingly complex, the target track changes correspondingly every time the radar scans for one period, which is necessary for track management.

(V) microprocessor and control module

5.1 cleaning task

The microprocessor receives the positioning and tracking information sent by the detection module, evaluates the cleaning target, and allocates a plurality of robot satellites matched with the cleaning target to coordinate and cooperate to complete the cleaning task; and each robot satellite calls the electromagnetic adsorption module to adsorb the space debris according to an instruction sent by the microprocessor, the laser ablation module is adopted to vaporize the space debris with the diameter less than or equal to 10cm, the formation is adjusted for the space debris with the diameter more than 10cm, and the space debris is pushed into the atmospheric orbit by cooperating with other robot satellites for transportation.

5.2 formation control

The microprocessor controls the robot formation by adopting different control strategies according to the working state of the robot satellite:

when the robot satellite is in the mission-free cruising state, the microprocessor takes the longest cruising as a constraint condition and adopts a pulse control strategy or a threshold value control strategy to enable the robot satellite to carry out flying-around motion by taking the main satellite as a center.

When the robot satellite is in a cooperative working state, the microprocessor takes the highest formation accuracy as a constraint condition, adopts a continuous micro-thrust strategy, enables part or all of the robot satellites executing the cleaning task to respectively perform independent motion, and returns to the circular orbit to continue flying around after the task is finished.

The control module is composed of an air storage tank and an operating system thereof, executes a series of position adjustment tasks including initial track adjustment, space station return and the like, and issues a control command in real time by the microprocessor to push the target into the atmosphere when cooperatively processing the large-size target.

FIG. 10 is a flow chart of flight formation control according to an embodiment of the present invention. The process of the control module for forming the queue of the robot satellites comprises the following steps:

s1, judging whether the cleaning task is received, if yes, going to step S2, otherwise going to step S4.

And S2, receiving the target information by adopting a continuous micro-thrust control model, estimating the orbit error, and correcting the flight orbit according to the estimation result until the cleaning task is completed.

S3, relative navigation among the satellites is carried out, if a team reconstruction instruction is received, a continuous thrust control mode is maintained according to the team reconstruction instruction until the track adjustment is completed, the self working mode is switched to a no-task state, and the step S1 is entered; otherwise, the circular orbit is returned to continue the orbiting motion, the self working mode is switched to the no-task state, and the step S1 is entered.

And S4, adopting a pulse thrust control model, receiving the measurement parameters, judging whether the error threshold is met, and if so, entering the step S5.

And S5, periodically applying a pulse control to the engine of the robot satellite, receiving the measurement parameters, judging whether the track regresses, if so, returning to the step S1, and if not, returning to the step S4.

In this embodiment, the formation queue form control policy specifically includes the following aspects:

(1) flight coordinate system

In theory, the present embodiment may employ existing coordinate systems. For example, an earth-centered inertial coordinate system, an orbital coordinate system, and the like.

1. Center of earth inertial coordinate system

And defining a coordinate origin o as the center of the earth, wherein an X axis points to the spring equinox along the intersecting line of the equatorial plane and the ecliptic plane of the earth, a Z axis points to the north pole, and a Y axis forms a right-hand system with the X axis and the Z axis in the equatorial plane.

2. Orbital coordinate system

Defining a coordinate origin o as a principal star centroid; the oy axis points in the direction of the main star along the geocentric; the ox axis is consistent with the motion direction of the main star; the oz axis is perpendicular to the main star orbital plane and follows a right-handed system.

(2) Flying formation design

The method comprises the following steps of designing a flight-around formation of a plurality of satellites relative to a reference satellite based on phase angles:

the formation takes the main satellite as a center to carry out the fly-around motion, the formation independently moves when a multi-robot cooperative task is executed, and the formation returns to the original orbit to continue the fly-around motion after the task is finished. Fig. 9 is a schematic view of a flying formation configuration of an embodiment of the present invention. Taking a three-robot formation as an example, a regular triangle formation is generally maintained to fly around. Each encircling robot completes the encircling flying motion on a spatial circular orbit relative to the reference main satellite, and the reference satellite is positioned at the center of the regular triangle. And if one of the reference surrounding robots is taken as one vertex of the space regular triangle, the surrounding robot phase angles of the other two vertexes of the regular triangle are 120 degrees and 240 degrees, and the counterclockwise rotation is positive. On the basis, in order to keep the longer time of the formation stable, the influence of adding a nonlinear item can be considered, and the influence comprises the following steps: 1. fixed error term 2, long term 3, periodic term. The influence of the long-term does not necessarily need to modify the track control mode, and can be offset to a certain extent by changing the initial conditions.

(3) Formation maintenance and control

When the formation runs on track for a long time, the maintenance control of the formation and how to save energy consumption are important problems. Under the two conditions of task execution and non-task execution, different control strategies can be selected, and the requirements of taking precision or endurance as the first priority are met under different environments.

1. At mission-free cruise

A. And (3) pulse control strategy:

the pulse control is an optimal control based on a linear quadratic form, and is discretized. The pulse control is applied every few hundred seconds. The pulse control quantity is obtained by adopting the quadratic optimal control algorithm and is related to the relative motion state of the surrounding star and the reference star during sampling.

The impulse control can adopt an impulse thrust model. The engine of the impulse thrust model operates for much less time than the orbit period. The model is suitable for a solid fuel engine with large thrust and a fuel engine capable of being started repeatedly.

And carrying out pulse control on the surrounding stars. For the pulse control strategy, the controller with higher response speed is designed to be more beneficial to the improvement of the control precision and the reduction of the control energy consumption after the pulse control.

B. The threshold control strategy is as follows:

the threshold control means that a threshold D is selected, and when the error of the formation shape is smaller than D within the range of the allowable error of the formation, the natural formation state is kept, and the track control is not performed. The engine ignition is controlled only when the formation error exceeds a threshold D. Such control strategies may be applied to formation control where the accuracy of the formation is not as demanding.

2. In cooperation with each other

When working in tandem, in order to pursue high accuracy, it is more preferable to adopt long-term continuous control, i.e., the engine is always in an ignition state. The long-term continuous control is suitable for tasks which have high requirements on the formation accuracy. Since the control force is always applied, the formation is kept at a high accuracy throughout the flight. Under the action of no large initial deviation or large disturbance force, the control force always acts to eliminate the influence of small perturbation forces such as earth oblateness perturbation, sunlight pressure perturbation and atmospheric resistance perturbation. The long-term continuous control needs to select a low-thrust model. The low thrust model refers to the longer the electric propulsion system can function with the least thrust. The electric propulsion system has the characteristics of high specific impulse, small thrust, light weight, small volume and the like. At present, a Hall steady-state plasma thruster is widely applied to a small satellite and has reliable performance.

(4) Inter-satellite relative navigation

When the formation of the robot satellite formation is maintained and the reconstruction control is carried out, each satellite needs to obtain the information such as the position, the speed, the attitude and the like of other satellites in the formation in real time. The laser range finder can be used as measuring equipment, the relative speed and position between satellites can be indirectly estimated by measuring the relative azimuth and distance information between the satellites, the relative distance and speed between the satellites can be measured by a laser range finder signal transmitter and a laser range finder signal receiver on a formation, the time difference between a transmitted signal and a reflected signal is calculated, and the transmission rate of laser is utilized, so that the relative distance and speed between the satellites can be measured.

(5) Flight formation reconstruction

The formation reconstruction is roughly divided into the steps of detecting the positions of other robots in the formation through the MIMO radar, planning a reconstruction route through overall calculation and braking an engine.

When researching from the aspect of kinematics, firstly, a formation satellite motion equation represented by the relative orbit number between a main satellite and an accompanying satellite is deduced according to the coordinate conversion relation between the relative orbit number and the relative position and speed between the robot satellites under an orbit coordinate system, then on the basis of the motion equation, a small increment relative orbit number equation is deduced according to a Gaussian differential equation, the relation between the in-orbit and out-orbit control force of the satellite and the relative motion between the satellites is established, further the formation reconstruction is divided into two reconstruction conditions in an orbit plane and out-orbit plane, according to the particularity out-orbit plane, the small increment equation can be obtained, the pulse external force in the orbit plane only influences the orbit inclination angle and the ascent point ascent warp, the mutual relation between the orbit inclination angle and the ascent point ascent warp and the external force outside the orbit plane is deduced, and the semi-major axis, the orbit combination external force, the micro-major axis, the micro axis and the micro axis of the micro axis, And finally obtaining the relation between the relative orbit number among the satellites and the orbit pulse control force by the action conditions of the eccentricity ratio, the argument of the perigee and the mean perigee angle. According to the requirement of the space task, the optimal or suboptimal formation reconstruction track can be realized by selecting the reasonable track pulse.

The system is used for positioning and cleaning space garbage based on robot formation, can effectively enlarge the cleaning range, has the characteristics of low cost, low energy consumption, strong capturing capability and the like, and has certain popularization and application values in the field of space debris cleaning.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.