Non-cooperative target full-autonomous anti-collision avoidance method

Abstract

The application discloses a kind of non-cooperative target full autonomous anti-collision avoidance methods, comprising: on-board warning radar finds unknown target, captures and tracks unknown target, obtains the relative position of unknown target relative to main star, relative speed;Variable scale direct approximation algorithm is used to calculate the closest distance between unknown target and main star, and the interval time reaching the closest distance;The minimum distance required for maneuvering to completely avoid the unknown target is calculated, referred to as safety distance herein;According to the collision time, a hierarchical avoidance strategy is developed;According to the safety distance, the speed pulse required for avoidance is calculated;According to the speed direction of unknown target attack, the speed direction of avoidance is determined;According to the current main star's maneuvering ability, the jet length is calculated;After jet execution is completed, when the closest relative distance between main star and unknown target is greater than safety distance, avoidance is successful.The application realizes satellite autonomous operation in orbit to avoid space debris or abnormal unknown target.

Description

Technical Field

[0001] This invention relates to satellite guidance, navigation and control technology, and in particular to a method for collision avoidance during autonomous operation of an on-orbit satellite. Background Technology

[0002] When satellites operate overseas for extended periods without ground-based tracking and control, they cannot effectively avoid collisions with unknown targets or space debris using ground-based strategies, potentially leading to significant losses. To ensure the autonomous and safe operation of high-value satellites in orbit, warning radars are typically installed in the overall design of satellites. These radars provide relative position information of unknown targets and operate across the entire airspace, enabling the prediction of threats from all directions.

[0003] The warning radar can only measure information about unknown targets, and the satellite control system needs to process the measurement information and formulate corresponding avoidance strategies. Based on the above issues, this poses a new challenge to the long-term autonomous operation of the satellite in orbit. Summary of the Invention

[0004] The purpose of this invention is to provide a method for collision avoidance during autonomous operation of an on-orbit satellite, enabling the satellite to avoid space debris or abnormal unknown targets during autonomous operation in orbit.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A fully autonomous collision avoidance method for non-cooperative targets includes:

[0007] Step S1: The on-board warning radar detects an unknown target, captures and tracks the unknown target, and obtains the relative position and relative velocity of the unknown target relative to the host star;

[0008] Step S2: Based on the relative position and relative velocity, calculate the closest distance between the unknown target and the host star, as well as the time interval for reaching the closest distance, using a variable-scale direct approximation algorithm, which is referred to here as the collision time.

[0009] Step S3: Based on the satellite size of the primary satellite, the accuracy of the unknown target motion estimation, and the collision interval, calculate the minimum distance required for maneuvering to completely avoid the unknown target, which is referred to here as the safe distance;

[0010] Step S4: Based on the collision time, formulate a graded avoidance strategy; based on the safe distance, calculate the velocity pulse required for avoidance; based on the direction of the incoming speed of the unknown target, determine the speed direction for avoidance; based on the current maneuverability of the host planet, calculate the jet propulsion duration; after the jet propulsion is completed, if the closest relative distance between the host planet and the unknown target is greater than the safe distance, then the avoidance is successful.

[0011] Optionally, step S1 includes: acquiring ranging and angle measurement information through the on-board alarm device, processing the data to obtain relative position information, and using a decaying Kalman filter algorithm based on the CW equation to filter and estimate the relative position information to obtain the relative position and the relative velocity.

[0012] Optionally, step S2 includes: obtaining the equations of relative motion between the two stars based on the analytical solution expression of the CW equations and the known conditions.

[0013]

[0014] Where t represents the recursion duration (the interval from the initial moment); w is the average orbital angular velocity, [x0 y0z0 v x0 v y0 v z0 [ ] represents the relative position and relative velocity of the initial unknown target relative to the host star.

[0015] Optionally, step S2 further includes: the step of solving the collision time tp includes:

[0016] Step S2.1: Based on the current relative position and velocity, obtain the time tf required for the primary star to reach the closest distance;

[0017]

[0018] Step S2.2: Using a variable step size search method, the time interval from 0 to tf is used to obtain the corresponding tmz when the distance accuracy is higher than 0.01m. tmz represents the time interval between the closest distances of the two satellites.

[0019] Step S2.2.1: Set the initial search step size step1 to 100s; t ranges from 0 to tf, and calculate...

[0020] xt0 = cwditui(rv0,n,t-step1)

[0021] In the formula, xt0 represents the relative position velocity vector at time t-step1; rv0 represents the initial relative position velocity vector; cwditui represents the analytical solution function of the CW equation, xt0 = rv0 in the first step, n represents the average orbital angular velocity, and t represents the time interval from the initial time.

[0022] xt1 = cwditui(rv0,n,t+step1)

[0023] In the formula, xt1 = represents the relative position velocity vector at time t+step1; if t+step1 > tf, then let the recursion duration be tf;

[0024] xt = cwditui(rv0,n,t)

[0025] In the formula, xt represents the relative position velocity vector at time t;

[0026] Compare the recursive time to time t, t+step1, and determine if the collision time is within this range.

[0027] (norm(xt1(1:3))-norm(xt (1:3)))*(norm(xt (1:3))-norm(xt0(1:3)))<0;

[0028] If so, proceed to step S2.2.2;

[0029] If not, return to step S2.2.1 and let t = t + step1, and re-evaluate;

[0030] Step S2.2.2: Set the second-level search step size step2 to 10s, and t1 from t to t+step1, calculate xt0=cwditui(rv0,n,t1) respectively;

[0031] xt1 = cwditui(rv0,n,t1+step2)

[0032] Where, if t1+step2>t+step1, then let the recursion time be t+step1, xt0=cwditui(rv0,n,t1-step2);

[0033] Compare the recursive time t1-step2, t1, and t1+step2 to determine if the collision time is within this range;

[0034] Abs(norm(xt1(1:3))-norm(xt0(1:3)))>0.01 and

[0035] (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))<0

[0036] If so, return to step S2.2.2 and set step2 = step2 / 2 to start the judgment again;

[0037] If not, then the collision has not yet occurred.

[0038] Abs(norm(xt1(1:3))-norm(xt0(1:3)))>0.01 and (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))>0 and let t1=t1+step2, then return to step S2.2.2;

[0039] Otherwise, if the condition Abs(norm(xt1(1:3))-norm(xt0(1:3)))≤0.01 is satisfied, that is, the current iteration time t1 is the collision time tp, and the solution is completed.

[0040] Optionally, it also includes: calculating the position velocity vector rvp reaching the nearest distance based on the collision time tp.

[0041] rvp = cwditui(rv0,n,tp)

[0042] Find the nearest distance r min :r min =norm(rvp(1:3)).

[0043] Optionally, step S3 includes: calculating the safety distance r based on the collision time tp and the position-velocity accuracy r and velocity accuracy v of the target motion estimation algorithm. safe = r + v·tp + s; where s is the satellite size.

[0044] Optionally, step S4 includes: formulating a graded avoidance strategy based on the collision time.

[0045] Step S4.1: Calculate the collision probability and time.

[0046] Step S4.2: If the collision time is less than 50 seconds, no evasive maneuver shall be taken;

[0047] Step S4.3: If the collision time is greater than 50 seconds and the closest distance is less than the safe distance for 1 minute, set a collision warning sign and take evasive maneuvers; when the satellite is outside the safe distance, cancel the collision warning.

[0048] Step S4.4: If the collision time is greater than 250 seconds, a graded early warning strategy shall be adopted.

[0049] The tiered early warning strategy includes:

[0050] At 2000 seconds into the collision, if the closest distance to the target remains less than the safe distance for one minute, the satellite will issue the first collision warning signal. The satellite will then be instructed by the ground control system to decide whether to take evasive maneuvers.

[0051] If the closest distance to the target remains less than the safe distance for one minute at 1000 seconds of the collision time, the satellite will issue a second collision warning signal. The ground will then decide whether to perform an evasive maneuver. Once the satellite is beyond the safe distance, the collision warning will be lifted.

[0052] At 500 seconds into the collision, the closest distance remained less than the safe distance for one minute, prompting the satellite to autonomously perform evasive maneuvers.

[0053] Optionally, step S4 further includes: calculating the velocity pulse Vy required for avoidance based on the safe distance.

[0054] Vy=a*tj

[0055] Among them, the avoidance time a is the satellite's maneuvering acceleration, r safe The safe distance to be avoided.

[0056] Optionally, step S4 further includes: determining the evasive velocity direction based on the incoming velocity direction of the unknown target.

[0057]

[0058] According to the current satellite mean right ascension l b Size determines the direction of the satellite's jet stream, when l b ∈(0,π), vy=atj Otherwise vy=-a·tj, rvp(5) represents the relative velocity in the Y direction when the two stars are at their closest distance; rvp(6) represents the relative velocity in the Z direction when the two stars are at their closest distance.

[0059] Optionally, step S4 further includes: calculating the corresponding jet duration based on the current maneuverability of each axis of the primary star; after the jet is completed, repeating step S2 to calculate the closest relative distance between the two stars based on the current relative position and relative speed; if the closest relative distance between the primary star and the unknown target is greater than the safe distance, then the avoidance is successful.

[0060] Compared with existing technologies, the method adopted in this invention has the following advantages and beneficial effects: it achieves fully autonomous on-board collision avoidance maneuvers, reduces dependence on ground-based orbit determination, and improves the safety and timeliness of satellite operation; through the derivation of algorithm principles and relative motion dynamics equations, it can be seen that only the relative position and velocity information of the current target is needed to obtain the closest distance and time between the two satellites and whether there is a collision risk, making the algorithm simple; this method only applies control pulses in the Y-axis direction and does not change the distance and velocity in the X-axis direction, thus not changing the stability of the escort trajectory, and the original formation mission can continue to be performed without any safety risk to the original target; since control pulses are only applied in the Y-axis direction during the avoidance process, and the control direction is the direction of the north-south position maintainer, the fuel consumption of the north-south position maintainer is effectively saved. Attached Figure Description

[0061] Figure 1 This is a flowchart illustrating a fully autonomous collision avoidance method for non-cooperative targets according to an embodiment of the present invention.

[0062] Figure 2 This is a schematic diagram illustrating the relative motion change of alarm avoidance in a fully autonomous collision avoidance method for non-cooperative targets, provided in an embodiment of the present invention.

[0063] Figure 3 This is a schematic diagram of the avoidance direction in a non-cooperative target fully autonomous collision avoidance method provided in an embodiment of the present invention. Detailed Implementation

[0064] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the non-cooperative target fully autonomous collision avoidance method proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0065] The goal of the non-cooperative target fully autonomous collision avoidance method is to enable satellites to avoid space debris or anomalous unknown targets. This invention presents expressions for constructing the closest distance and collision time based on the relative position, relative velocity, and relative motion dynamics of unknown targets obtained by filtering on-board warning radar measurement information. It establishes the theoretical basis for collision avoidance using on-board target motion estimation data, and designs a collision avoidance strategy based on this.

[0066] Based on onboard warning radar measurement information, this invention solves the technical difficulties of low accuracy in determining orbits of non-cooperative targets from the ground, inability to conduct overseas measurement and control, and slow formulation of ground orbit control strategies, and achieves the goal of a fully autonomous collision avoidance method for non-cooperative targets.

[0067] like Figure 1 As shown, this embodiment provides a non-cooperative target fully autonomous collision avoidance method, including: step S1, the on-board warning radar detects an unknown target, captures and tracks the unknown target, and obtains the relative position and relative velocity of the unknown target relative to the host star.

[0068] In this embodiment, step S1 includes: acquiring ranging and angle measurement information through the on-board alarm device, obtaining relative position information after data processing, and using a decaying Kalman filter algorithm based on the CW equation to filter and estimate the relative position information to obtain the relative position and the relative velocity.

[0069] Step S2: Based on the relative position and relative velocity, the closest distance between the unknown target and the host star is calculated using a variable-scale direct approximation algorithm, as well as the time interval for reaching the closest distance, which is referred to here as the collision time.

[0070] In this embodiment, step S2 includes: obtaining the equations of relative motion between the two stars based on the analytical solution expression of the CW equation and the known conditions.

[0071]

[0072] Where t represents the recursion duration (the interval from the initial moment); w is the average orbital angular velocity, [x0 y0z0 v x0 v y0 v z0 [ ] represents the relative position and relative velocity of the initial unknown target relative to the host star.

[0073] Step S2 further includes: the step of solving the collision time tp includes: step S2.1, obtaining the time tf required for the primary star to travel to the closest distance based on the current relative position and velocity;

[0074]

[0075] Step S2.2: The time range is from 0 to tf. The variable step size search method is used to obtain the distance accuracy (the distance accuracy between the two consecutive frames is better than 0.01m) and the corresponding tmz (tmz represents the time interval between the closest distance between the two stars) is higher than 0.01m (0.01m represents the variable step size search threshold, which can be modified): that is, the variable step size calculates the time and relative position and velocity of the two stars when they are closest in the future (similar to the bisection method).

[0076] Step S2.2.1: Set the initial search step size step1 to 100s; t ranges from 0 to tf, and calculate...

[0077] xt0 = cwditui(rv0,n,t-step1)

[0078] In the formula, xt0 represents the relative position velocity vector at time t-step1; rv0 represents the initial relative position velocity vector; cwditui represents the analytical solution function of the CW equation, xt0 = rv0 in the first step, n represents the average orbital angular velocity, and t represents the time interval from the initial time.

[0079] xt1 = cwditui(rv0,n,t+step1)

[0080] In the formula, xt1 = represents the relative position velocity vector at time t+step1; if t+step1>tf, then let the recursion duration be tf;

[0081] xt = cwditui(rv0,n,t)

[0082] In the formula, xt represents the relative position velocity vector at time t;

[0083] Compare the recursive time to time t, t+step1, and determine if the collision time is within this range.

[0084] (norm(xt1(1:3))-norm(xt(1:3)))*(norm(xt(1:3))-norm(xt0(1:3)))<0; This formula indicates that the closest distance time is within the range of t to t+step1.

[0085] If so, proceed to step S2.2.2;

[0086] If not, return to step S2.2.1 and let t = t + step1, and re-evaluate;

[0087] Step S2.2.2: Set the second-level search step size step2 to 10s, and t1 from t to t+step1, calculate respectively.

[0088] xt0 = cwditui(rv0,n,t1)

[0089] xt1 = cwditui(rv0,n,t1+step2)

[0090] If t1+step2>t+step1, then let the recursion time be t+step1.

[0091] xt0 = cwditui(rv0,n,t1-step2)

[0092] Compare the recursive time t1-step2, t1, and t1+step2 to determine if the collision time is within this range;

[0093] The formula Abs(norm(xt1(1:3))-norm(xt0(1:3)))>0.01 and (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))<0 indicates that the closest distance time is within the range of t-step2~t+step2.

[0094] If so, return to step S2.2.2 and set step2 = step2 / 2 to start the judgment again;

[0095] If not, then the collision has not yet occurred.

[0096] Abs(norm(xt1(1:3))-norm(xt0(1:3)))>0.01 and (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))>0 and let t1=t1+step2, then return to step S2.2.2;

[0097] Otherwise, if the condition Abs(norm(xt1(1:3))-norm(xt0(1:3)))≤0.01 is satisfied, that is, the current iteration time t1 is the collision time tp, and the solution is completed.

[0098] Step S3: Based on the satellite size of the primary satellite, the accuracy of the unknown target motion estimation, and the collision interval, calculate the minimum distance required to completely avoid the unknown target, which is referred to here as the safe distance.

[0099] Calculate the velocity vector rvp at the closest point based on the collision time tp:

[0100] rvp = cwditui(rv0,n,tp)

[0101] Solve for the nearest distance rmin: rmin = norm(rvp(1:3)).

[0102] Step S3 includes: calculating the safety distance r based on the collision time tp and the position-velocity accuracy r and velocity accuracy v of the target motion estimation algorithm. safe = r + v·tp + s; where s is the satellite size.

[0103] Step S4: Based on the collision time, formulate a graded avoidance strategy; based on the safe distance, calculate the velocity pulse required for avoidance; based on the direction of the incoming speed of the unknown target, determine the speed direction for avoidance; based on the current maneuverability of the host planet, calculate the jet propulsion duration; after the jet propulsion is completed, if the closest relative distance between the host planet and the unknown target is greater than the safe distance, then the avoidance is successful.

[0104] Step S4 includes: formulating a graded avoidance strategy based on the collision time.

[0105] Step S4.1: Calculate the collision probability and time.

[0106] Step S4.2: If the collision time is less than 50 seconds, no evasive maneuver shall be taken;

[0107] Step S4.3: If the collision time is greater than 50 seconds and the closest distance is less than the safe distance for 1 minute, set a collision warning sign and take evasive maneuvers; when the satellite is outside the safe distance, cancel the collision warning.

[0108] Step S4.4: If the collision time is greater than 250 seconds, a graded early warning strategy shall be adopted.

[0109] The design principle of the tiered early warning strategy is to reduce the false alarm rate and avoid misoperation;

[0110] The tiered early warning strategy includes:

[0111] At 2000 seconds into the collision, if the closest distance to the target remains less than the safe distance for one minute, the satellite will issue the first collision warning signal. The satellite will then be instructed by the ground control system to decide whether to take evasive maneuvers.

[0112] If the closest distance to the target remains less than the safe distance for one minute at 1000 seconds of the collision time, the satellite will issue a second collision warning signal. The ground will then decide whether to perform an evasive maneuver. Once the satellite is beyond the safe distance, the collision warning will be lifted.

[0113] At 500 seconds into the collision, the closest distance remained less than the safe distance for one minute, prompting the satellite to autonomously perform evasive maneuvers.

[0114] Step S4 further includes: calculating the velocity pulse Vy required for avoidance based on the safety distance.

[0115] Vy=a*tj

[0116] Among them, the avoidance time a is the satellite's maneuvering acceleration, r safe The safe distance to be avoided.

[0117] Step S4 further includes: determining the evasion velocity direction vz based on the incoming velocity direction of the unknown target.

[0118]

[0119] According to the current satellite mean right ascension l b Size determines the satellite's jet propulsion direction (i.e., whether the satellite jets propulsion along the positive or negative Y-axis), when l b ∈(0,π), vy=a·tj Otherwise vy=-a·tj, rvp(5) represents the relative velocity in the Y direction when the two stars are at their closest distance; rvp(6) represents the relative velocity in the Z direction when the two stars are at their closest distance. The X direction, Y direction and Z direction represent the directions of the corresponding three coordinate axes in the VVLH coordinate system of the primary star.

[0120] Step S4 further includes: calculating the corresponding jet duration based on the current maneuverability of each axis of the primary star; after the jet is completed, repeating step S2 to calculate the closest relative distance between the two stars based on the current relative position and relative speed; if the closest relative distance between the primary star and the unknown target is greater than the safe distance, the avoidance is successful.

[0121] To facilitate understanding of the above embodiments, a specific example is given below:

[0122] like Figure 2 As shown, this is a schematic diagram of the relative motion changes during alarm avoidance. At point A, the alarm radar detects an unknown target at a distance of 100km between two satellites. At point B, the motion estimation filtering algorithm based on the alarm information converges. An evasive maneuver begins at time t1. After the maneuver, the predicted closest distance at time t2 is greater than the safe distance, indicating successful evasion. Figure 3 The diagram shows the avoidance direction, which is perpendicular to the velocity of the target at the closest distance. Specifically, the following implementation steps achieve fully autonomous collision avoidance for non-cooperative targets based on alarm information.

[0123] The onboard warning radar detects an unknown target, acquires and tracks the target, and initiates the relative motion estimation algorithm for the unknown target relative to the host satellite:

[0124] The relative measurement equations are the outputs of spaceborne measurement equipment, such as the relative distance, relative line-of-sight azimuth, and relative line-of-sight elevation measured by microwave radar. For other types of measurement equipment, the measurement principle is similar, only the accuracy differs. Therefore, the measurement equations are derived as follows:

[0125]

[0126] Where ρ is the relative distance between the two stars, α is the elevation angle of the target star in the orbital coordinates of the accompanying satellite, β is the azimuth angle of the target star in the orbital coordinates of the accompanying satellite, x, y, and z are the three-axis relative positions of the target star in the orbital coordinates of the accompanying satellite, and V is the observation noise.

[0127] A navigation filtering algorithm is designed, and the filtering calculation is performed based on the attitude of the satellite relative to the reference orbital system and the output of the navigation sensor. The final output yields the relative position and relative velocity information of the two satellites.

[0128] To achieve fully autonomous collision avoidance of unknown targets, a variable-scale direct approximation algorithm is used to calculate the closest distance and corresponding duration between two satellites:

[0129] The CW equation is a method for describing the relative motion of circularly orbited satellites based on their relative positions. Theoretically, it has been proven that the CW equation can describe the relative motion of high-orbit satellites. Based on the analytical solution expression of the CW equation and known conditions, the equations of relative motion between two satellites can be obtained, and the calculation formula is as follows:

[0130]

[0131] Where w is the average orbital angular velocity, [x0 y0 z0 v x0 v y0 v z0 [The initial target's position and velocity relative to the primary star]

[0132] Calculate the time tp to reach the nearest distance:

[0133] 1) Based on the current relative distance and speed, obtain the time tf required for the satellite to reach its closest distance;

[0134]

[0135] 2) For time intervals from 0 to tf, the variable step size search method yields tmz with a distance accuracy higher than 0.01m (variable step size search threshold, which can be modified):

[0136] Step 1: Set the initial search step size step1 to 100s; t ranges from 0 to tf. Calculate xt0 = cwditui(rv0,n,t-step1) (for the first iteration, xt0 = rv0), xt1 = cwditui(rv0,n,t+step1) (if t+step1>tf, then set the recursion time to tf), and xt = cwditui(rv0,n,t). Compare the recursed time t with t+step1 to determine if the collision time falls within this range.

[0137] (norm(xt1(1:3))-norm(xt(1:3)))*(norm(xt(1:3))-norm(xt0(1:3)))<0

[0138] If the condition is met, proceed to the second step; otherwise, t = t + step1 and re-evaluate from the first step.

[0139] Step 2: Set the second-level search step size step2 to 10s, and t1 from t to t+step1. Calculate xt0 = cwditui(rv0,n,t1), xt1 = cwditui(rv0,n,t1+step2) (if t1+step2>t+step1, then let the recursion time be t+step1), and xt0 = cwditui(rv0,n,t1-step2).

[0140] Compare the recursive time t1-step2, t1, and t1+step2 to determine if the collision time is within this range;

[0141] (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))<0

[0142] If the condition is met, then step2 = step2 / 2 and start the second step again; otherwise, it is determined that the collision time has not yet arrived.

[0143] (norm(xt1(1:3))-norm(xt0(1:3)))*(norm(xt0(1:3))-norm(xt00(1:3)))>0

[0144] t1 = t1 + step2, restarting the second step;

[0145] Otherwise, if the condition (norm(xt1(1:3))-norm(xt0(1:3)))>0 is met, that is, the current time t1 is the collision time tp, the solution is completed;

[0146] Solve for the position velocity vector rvp that reaches the closest distance:

[0147] rvp = cwditui(rv0,n,tp)

[0148] Find the nearest distance rmin: rmin = norm(rvp(1:3));

[0149] To achieve fully autonomous collision avoidance of unknown targets, the system calculates the safe distance required to completely avoid the unknown target based on the relative position and velocity obtained from relative motion estimation.

[0150] The safety distance r is calculated based on the collision time tp and the position-velocity accuracy r and velocity accuracy v of the target motion estimation algorithm. safe = r + v·tp + s; where s is the satellite size.

[0151] To achieve fully autonomous collision avoidance of unknown targets, the system formulates avoidance strategies and calculates the velocity pulses required for avoidance.

[0152] The avoidance strategies are as follows:

[0153] 1. Calculate the collision probability and time.

[0154] 2. No evasive maneuvers should be taken if the collision time is less than 50 seconds;

[0155] 3. If the collision time exceeds 50 seconds and the closest distance remains less than the safe distance for one minute, a collision warning sign will be issued, and evasive maneuvers will be initiated. The collision warning will be deactivated once the satellite is beyond the safe distance.

[0156] 4. For collisions lasting longer than 250 seconds, a tiered warning strategy will be implemented.

[0157] The design principle of the tiered early warning strategy is to reduce the false alarm rate and avoid misoperation.

[0158] At 2000 seconds into the collision, if the closest distance to the target remains below the safe distance for one minute, the satellite will issue the first collision warning signal. The decision on whether to take evasive maneuvers will then be made by the ground control.

[0159] At 1000 seconds into the collision, if the closest distance remains below the safe distance for one minute, the satellite issues a second collision warning signal. The ground control then decides whether to perform evasive maneuvers. Once the satellite is beyond the safe distance, the collision warning is lifted.

[0160] At 500 seconds into the collision, the closest distance remained less than the safe distance for one minute, prompting the satellite to autonomously perform evasive maneuvers.

[0161] Avoidance pulse calculation:

[0162] Avoidance time Where 'a' represents the satellite's maneuvering acceleration.

[0163]

[0164] According to the current right ascension l b Size determines the jet direction of y, when l b ∈(0,π), vy=a·tj otherwise vy=-a·tj.

[0165] In summary, this embodiment discloses a fully autonomous collision avoidance method for non-cooperative targets. When a satellite is operating outside of Earth's orbit without ground control, it cannot avoid collisions with unknown targets (such as defunct satellites or space debris) in a timely manner using ground-based strategies, leading to significant losses. To ensure the autonomous and safe operation of high-value satellites in orbit, satellites are generally designed with warning radars to provide relative position information of unknown targets. These warning radars operate across the entire airspace and can predict threats from all directions. Based on the measurement information from this warning radar, this invention designs an onboard autonomous collision warning algorithm and corresponding avoidance strategies, achieving autonomous collision avoidance functionality applicable to all mission phases. This method selects out-of-plane thrusters for avoidance control, and can adjust the inclination of the primary satellite while avoiding collisions, saving fuel.

[0166] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0167] It should be noted that the apparatus and methods disclosed in the embodiments herein can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments herein. In this regard, each block in a flowchart or block diagram may represent a module, program, or part of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system to perform the specified function or action, or can be implemented using a combination of dedicated hardware and computer instructions.

[0168] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A fully autonomous collision avoidance method for non-cooperative targets, characterized in that, include: Step S1: The on-board warning radar detects an unknown target, captures and tracks the unknown target, and obtains the relative position and relative velocity of the unknown target relative to the host star; Step S2: Based on the relative position and relative velocity, calculate the closest distance between the unknown target and the host star, as well as the time interval for reaching the closest distance, using a variable-scale direct approximation algorithm, which is referred to here as the collision time. Step S3: Based on the satellite size of the primary satellite, the accuracy of the unknown target motion estimation, and the collision time, calculate the minimum distance required to completely avoid the unknown target, which is referred to here as the safe distance; Step S4: Based on the collision time, formulate a graded avoidance strategy; based on the safe distance, calculate the velocity pulse required for avoidance; based on the direction of the incoming speed of the unknown target, determine the speed direction for avoidance; based on the current maneuverability of the host planet, calculate the jet propulsion duration; after the jet propulsion is completed, if the closest distance between the host planet and the unknown target is greater than the safe distance, then the avoidance is successful.

2. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 1, characterized in that, Step S1 includes: acquiring ranging and angle measurement information through the on-board warning radar, processing the data to obtain relative position information, and using a decaying Kalman filter algorithm based on the CW equation to filter and estimate the relative position information to obtain the relative position and the relative velocity.

3. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 2, characterized in that, Step S2 includes: The equations of relative motion between the two stars can be obtained based on the analytical solution of the CW equations and the known conditions. in, t This represents the recursion duration, which indicates the time interval from the initial time. The average orbital angular velocity, The initial unknown target's relative position and relative velocity relative to the host star.

4. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 3, characterized in that, Step S2 further includes: solving the collision time. tp The steps include: Step S2.1: Based on the current relative position and relative velocity, obtain the time required for the primary star to reach the closest distance. tf ; ； Step S2.2, time from 0~ tf The variable step size search method is used to obtain the tmz corresponding to a distance accuracy higher than 0.01m, where tmz represents the time interval between the closest distances of the two satellites. Step S2.2.1, Initial search step size step 1. Set to 100 seconds; t From 0~ tf Calculate separately xt 0= Where, in the formula, xt 0 represents t-step The relative position and velocity vector at time 1; rv 0 represents the initial relative position velocity vector; Represents the analytical solution function of the CW equation, first step. xt 0= rv 0, n Represents the average orbital angular velocity. t This indicates the time interval since the initial moment; xt 1= Where, in the formula, xt 1= means t + step The relative position and velocity vector at time 1; if > tf Let the recursion time be tf ; Where, in the formula, xt express t The relative position velocity vector at any given moment; Compare and recursively calculate to time. t , t + step 1. Determine if the collision time falls within this range ( t , t + step 1) Within, the judgment condition (1) is: ； If condition (1) is true, proceed to step S2.2.2; If condition (1) is not met, then return to step S2.2.1 and let t = t + step 1. Reassess; Step S2.2.2, Second-level search step size step 2 is set to 10 seconds. t 1 From t ~ t + step 1. Calculate separately xt 0= ; xt 1= Among them, if Let the recursion time be t + step 1, xt 00= ; Compare and recursively calculate to time. , t 1, t 1+ step 2. Determine if the collision time falls within this range ( , t 1+ step 2) Within, the judgment condition (2) is: and If condition (2) is true, then return to step S2.2.2, and let step 2= step Re-evaluate 2 / 2; If condition (2) is not true, and condition (3) is satisfied: and Then let t 1= t 1+ step 2. Return to step S2.2.2; If neither condition (2) nor condition (3) is true, then the condition is satisfied. That is, the current iteration time t 1 represents the collision time. tp The solution is now complete.

5. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 4, characterized in that, Also includes: based on collision time tp Solve for the position velocity vector rvp that reaches the closest distance: rvp= Find the nearest distance r min :r min = norm (rvp(1:3)).

6. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 5, characterized in that, Step S3 includes: based on the collision time tp Position accuracy of target motion estimation algorithm r and speed accuracy v Calculate the safe distance ;in, s For satellite dimensions.

7. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 6, characterized in that, Step S4 includes: formulating a graded avoidance strategy based on the collision time. Step S4.1: Calculate the collision probability and time. Step S4.2: If the collision time is less than 50 seconds, no evasive maneuver shall be taken; Step S4.3: If the collision time is greater than 50 seconds and the closest distance is less than the safe distance for 1 minute, set a collision warning sign and take evasive maneuvers; when the satellite is outside the safe distance, cancel the collision warning. Step S4.4: If the collision time is greater than 250 seconds, a graded early warning strategy shall be adopted. The tiered early warning strategy includes: At 2000 seconds into the collision, if the closest distance to the target remains less than the safe distance for one minute, the satellite will issue the first collision warning signal. The satellite will then be instructed by the ground control system to decide whether to take evasive maneuvers. If the closest distance to the target remains less than the safe distance for one minute at 1000 seconds of the collision time, the satellite will issue a second collision warning signal. The ground will then decide whether to perform an evasive maneuver. Once the satellite is outside the safe distance, the collision warning will be lifted. At 500 seconds into the collision, the closest distance remained less than the safe distance for one minute, prompting the satellite to autonomously perform evasive maneuvers.

8. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 7, characterized in that, Step S4 further includes: Calculate the velocity pulse required for avoidance based on the stated safety distance. : Among them, the avoidance time , For the satellite's maneuvering acceleration, r safe The safe distance to be avoided.

9. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 8, characterized in that, Step S4 further includes: Based on the incoming speed and direction of the unknown target, determine the speed direction for evasion. : According to the current satellite mean ascension Size determines the direction of the satellite's jet stream, when , ,otherwise , This represents the relative velocity in the Y direction when the two stars are at their closest distance. This represents the relative velocity in the Z direction when the two stars are at their closest distance.

10. The fully autonomous collision avoidance method for non-cooperative targets as described in claim 9, characterized in that, Step S4 further includes: calculating the corresponding jet duration based on the current maneuverability of each axis of the primary star; after the jet is completed, repeating step S2 to calculate the closest distance between the two stars based on the current relative position and relative speed; if the closest distance between the primary star and the unknown target is greater than the safe distance, the avoidance is successful.

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