CN112455724B - Space passive object transfer method based on throwing, striking and receiving - Google Patents

Abstract

The invention discloses a space passive object transfer method based on throwing and hitting, comprising the following steps: Step 1: determine a throwing scheme according to the occlusion between the current position of the passive object and the target position; The current position of the serving satellite, the task energy and time constraints, select the serving satellite participating in the mission and the range of the hitting point; Step 3: Based on the selected serving satellite, optimize the hitting point position and the reference trajectory of each serving satellite; Step 4: Based on the optimization The obtained reference trajectory generates an extended reference trajectory; Step 5: Execute the throwing scheme determined in Step 1, track the extended reference trajectory, and realize the transfer of the passive object. By mobilizing different service satellites to move passive objects, the invention no longer needs the service satellites to move for a long time and can reduce the overall energy consumption of the system.

Description

A space passive object transfer method based on throwing and hitting

technical field

The invention belongs to the technical field of space target transfer, in particular to a space passive object transfer method based on throwing and hitting.

Background technique

As the functions of the space station continue to expand, the volume of the space station continues to increase. In some off-station maintenance and assembly work, the distance between the parts warehouse and the work surface has exceeded the working space of the space station robotic arm.

There are two types of existing solutions, one is to set orbits on the outer surface of the space station for the manipulator to move, and the other is to use the accompanying service satellites to drag objects to the work surface. Since the space station is composed of spliced modules of different periods and different specifications, the first type of method is difficult to apply. The second type of method requires repeated motion of the serving satellite, which increases energy consumption.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the prior art, the present invention provides a space passive object transfer method based on throwing and hitting, which solves the problem that the transfer of spare parts warehouses in the current space station maintenance and assembly work requires repeated movement of the service satellite. , the problem of large energy consumption.

In order to achieve the above object, the present invention provides the following technical solutions: a space passive object transfer method based on throwing and hitting, comprising the following steps:

Step 1: Determine the throwing scheme according to the occlusion between the current position of the passive object and the target position;

Step 2: According to the current position of all service satellites, mission energy and time constraints, select the service satellites participating in the mission and the scope of the strike point;

Step 3: Based on the selected service satellites, optimize the location of the hitting point and the reference trajectory of each service satellite;

Step 4: Based on the reference trajectory obtained by optimization, generate an extended reference trajectory;

Step 5: Execute the throwing scheme determined in Step 1, track the extended reference trajectory, and realize the transfer of the passive object.

Further, the specific steps of the step 1 are as follows:

When there is no blocking object between the current position of the passive object and the target position or the blocking object between the current position of the passive object and the target position can be avoided by adjusting the positions of the throwing satellite and the receiving satellite, it is not necessary to mobilize the hitting satellite to strike. Strike; otherwise, the strike satellite needs to be mobilized to carry out relay strike.

Further, the number of the hit satellites is several.

Further, the number of the hit satellites is determined according to the mission energy, time constraints, the situation of the occluded objects on the throwing path, and the distribution of the serving satellites.

Further, the specific steps of the step 2 are as follows:

According to the current position of all the service satellites, the task energy and time constraints, select the service satellites participating in the mission, and select the first service satellite and the second service satellite nearby according to the current position and target position of the passive object from the service satellites participating in the mission respectively;

When the residual momentum direction of the first serving satellite after grabbing the target can avoid occluding objects or the path from the second serving satellite to the target position can avoid occluding objects, the first serving satellite is selected as the throwing satellite and the second serving satellite is selected as the Access satellites, otherwise you need to select several nearby hit satellites.

Further, in the step 3, the direct trajectory optimization method based on the collision system calculates the reference trajectory and hitting point position of each serving satellite.

Further, the reference trajectory in the step 4 is a segmented continuous system composed of several segments divided by the calculated collision moment, and the segments are discontinuous, and each segment is forwardly expanded and backwardly expanded to obtain a collision system. The virtual motion trajectory before and after the collision moment is used as an extended reference trajectory.

Further, in step 5, the current segment of the extended reference trajectory is tracked according to the state quantity of the serving satellite and the state quantity of the passive object, and when a real collision is detected, it jumps and tracks to the next segment of the extended reference trajectory.

Compared with the prior art, the present invention at least has the following beneficial effects:

The present invention provides a space passive object transfer method based on throwing and hitting. For the transfer of passive objects in space, the repeated movement of the serving spacecraft is no longer required, and the energy required by a single serving spacecraft is reduced. When the current position of the passive object There is no blocking object between the target position or the blocking object between the current position of the passive object and the target position. When the position of the throwing satellite and the receiving satellite can be adjusted to avoid, there is no need to mobilize the hitting satellite to hit, directly through a service The satellite throws the passive object, and another serving satellite can directly access it at the access point. The serving satellite only needs energy for short-distance movement and throwing the passive object, and it is difficult to block the object between the current position of the passive object and the target position. The path of the passive object can be changed simply by throwing the satellite and receiving the satellite directly by hitting the satellite to change the path of the passive object. The present invention moves the passive object by mobilizing different service satellites, and does not need the service satellite to move for a long time and a long distance. , which can reduce the overall energy consumption of the system.

Further, in step 2, the service satellites participating in the mission are selected so that the entire optimization result is not the global optimal solution, and the calculation amount of the global optimal solution is relatively large. Pre-selecting the mission satellite can greatly reduce the calculation amount and quickly obtain the local optimal solution. , to speed up optimization.

Description of drawings

1 is a schematic diagram of the space passive object transfer task of the present invention based on throwing and hitting;

2 is a schematic diagram of an extended reference trajectory of the present invention;

In the drawings: 1-space station, 2-serving satellite, 3-passive object, 4-first target position, 5-hitting position, 6-movement trajectory of passive object, 7-second target position, 8-avoidance The occluded throwing position, 9- the third target position, 10- the reference track, 11- the actual track, 12- the reverse extension of the reference track, 13- the forward extension of the reference track, 14- the jump moment of the reference track, 15 - The jump moment of the actual trajectory.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , the present invention provides a method for transferring passive objects in space based on throwing and hitting. According to the constraints of the transfer task, the distribution of the service satellites accompanying the space station 1 around the space station 1, the task design is carried out, and the design for each service satellite is carried out. Reference track 10; perform offline expansion on the reference track 10, and use the expanded track as the final reference track to perform tracking control. Specific steps are as follows:

Step 1: Determine the throwing scheme according to the occlusion between the current position of the passive object 3 to be transferred and the target position; if there is no blocking object or the blocking object can be eliminated by adjusting the position of the throwing satellite, and the service satellite 2 is not mobilized to strike ; If the blocking object is unavoidable, mobilize a service satellite 2 to strike, and the strike satellite may not be limited to one time, and the strike point is determined according to the throwing plan in step 1 and the distribution of the service satellite, and the strike satellite is The number of s depends on the mission energy, time constraints, the occluded objects on the throwing path, and the distribution of serving satellites; the motion trajectory 6 of the passive object is shown in Figure 1.

Specifically: as shown in Figure 1: if there is no occlusion between the current position and the target position, such as the situation between the current position and the first target position 4, call a flying service satellite 2 to throw the passive object 3, Call another service satellite to pick up the object near the first target position 4; if the occlusion angle is small, that is, between the current position and the second target position 7, the movement of the satellite to be thrown or the satellite is acceptable, that is, the service The energy required by the movement of satellite 2 can satisfy the service satellite 2 to complete the movement, then the passive object 1 moves to the throwing position that avoids the occlusion, and the throwing point of the throwing satellite also moves to the throwing position 8 that avoids the occlusion or the passive object does not move. , the access point of the satellite is moved to 4, then only two service satellites need to be mobilized to complete the throwing, and there is no need to mobilize additional service satellites for relay strike. If the occluding object cannot avoid, for example, the third target position 9 , an additional serving satellite needs to be mobilized to strike at the striking position 5 , so that the passive object bypasses the occluding object and reaches the third target position 9 .

Under normal circumstances, the target position can be reached without out-of-plane transfer, and only two serving satellites are needed as throwing satellites and receiving satellites; if out-of-plane transfer is required, an additional serving satellite needs to be called for hitting, as a hit satellite.

Step 2: According to the current positions of all service satellites 2, task energy or time constraints, select the service satellites 2 participating in the mission and the range of the strike point from all the service satellites 2, and the strike satellite preferably considers the service satellite 2 closest to the strike point; Among them, the task energy mainly refers to the energy consumed by the movement of the center of mass of the service satellite 2, the attitude adjustment, and the movement of the robotic arm. In a mission, the possible energy constraints include: the total energy consumption of all serving satellites or the remaining energy of all serving satellites after completing the mission as much as possible. The time constraint is the time it takes for the passive object to finally reach the target position from the start of the task.

Concrete: It is assumed that the space station has a large number of accompanying service satellites available for calling. Since the trajectory optimization problem considering collision is a strong nonlinear problem, the global optimal solution cannot be obtained, and the amount of calculation is large. Pre-selecting the serving satellites participating in the mission can greatly reduce the amount of calculation and quickly obtain the local optimal solution; throwing satellites and access satellites are generally selected based on the position of the passive object; if the residual momentum direction of a serving satellite after grabbing the target can avoid occlusion or the path from a serving satellite to the target position can avoid occlusion, these two services are selected. Satellites are for throwing satellites and receiving satellites. The selection of the hitting point is determined according to the throwing scheme and the distribution of serving satellites in step 1.

Step 3, for the selected serving satellite, the reference trajectory is calculated by the direct method trajectory optimization method based on the collision system.

The specific calculation steps are as follows: The dynamic equation of the mission satellite or passive object is as follows:

为状态量中的速度，角速度量(q的一阶导数)，

为状态量中的加速度，角加速度量(q的二阶导数)，C为非线性项，τ为驱动力，J为雅可比矩阵，f为外部力，这里是指碰撞力。In the formula: M is the mass matrix of the satellite or passive object; q is the position and angle in the state quantity;

is the velocity in the state quantity, the angular velocity quantity (the first derivative of q),

is the acceleration in the state quantity, the angular acceleration (the second derivative of q), C is the nonlinear term, τ is the driving force, J is the Jacobian matrix, f is the external force, here refers to the collision force.

Collision is modeled based on complementary constraints. Typical complementary constraints are as follows:

Complementary constraints describe two mutually exclusive constraints z≥0 and g(z)≥0. At least one constraint must be 0 to satisfy z·g(z)=0. Complementary constraints can be compactly described as 0≤z⊥g(z)≥0.

Similarly, the collision is described as

_0≤φn (q) _⊥fn ≥0

where φn is the normal distance of the potential contact point and _{fn is} the normal force of the collision. f _t represents the tangential direction of the collision, which is decomposed into d directions here for easy calculation. γ is an auxiliary parameter and ψ(q, q.) is the tangential velocity.

The direct method discretizes the trajectory into N nodes, and optimizes the state and control quantities of the entire trajectory at the same time. The dynamics of the system are described by constraints. The method does not require dynamic forward simulations during optimization, avoiding the numerical difficulties that occur in forward methods. Its general form is

where G _f is the end objective function; q _N is the end state quantity; h is the time step; G is the process objective function; q _k is the state at time _k ; uk is the control input at time k; λ _k is the collision force; U is the value range of the control quantity; Q is the value range of the state quantity.

In this form, the constraints of the direct method considering collisions are constructed as follows, for the k+1th node

0≤φ _n (q _k+1 )⊥f _n,k+1 ≥0

The constraints of all state quantities and control quantities at all nodes together constitute the constraints of the optimization problem. Solving the optimization problem can obtain the state quantity, control quantity, collision force, etc. of the serving satellite and the passive object at each time node. The reference trajectory and reference control input can be obtained by interpolating the state quantity and the control quantity. The optimization problem is high-dimensional, but sparse, and can be solved using existing solvers.

Step 4, for the generated reference trajectory, perform forward and reverse expansion on each segment to generate an expanded reference trajectory; wherein, the expanded reference trajectory is segmented, and the segments are calculated collision points calculated by optimization, forward and reverse. The extension is to assume that the collision constraint does not exist, for the motion trajectory of the system.

As shown in Figure 2, there is a deviation between the actual trajectory 11 and the reference trajectory 10. Since the collision system is a typical discontinuous system, in the trajectory tracking problem, we describe it as a hybrid system. The hybrid system consists of a reference track 10 and a jump instant 14 of reference tracks connecting the reference tracks, as shown in FIG. 2 . For a collision system, the collision moment is the jump moment. Usually, due to errors, the jump time 14 of the reference track is inconsistent with the jump time 15 of the actual track, and the control system tends to diverge before and after the jump time. To address this issue, we introduce extended reference trajectories. For each segment, it is expanded in the forward direction and the reverse direction to be the backward expansion segment 13 of the reference track and the forward expansion segment 12 of the reference track, respectively. As shown in Figure 2, during tracking, only the actual track After the jump time 15 occurs, the extended reference track is switched.

Step 5: Execute the task, track the extended reference trajectory, and realize the transfer of the passive object; the state quantity of the serving satellite and the state quantity of the passive object track the current segment of the extended reference trajectory until a real collision is detected and switch to the next point segment, where the state quantities of the serving satellites and the passive objects respectively include the centroid position, velocity, acceleration, attitude angle, angular velocity, angular acceleration of the serving satellites and passive objects, and the angles of the joints of the serving satellite manipulator, angular velocity, angle acceleration.

Specifically: after the extended trajectory is calculated offline, the tracking control can be completed according to the general tracking control method:

。

.

Claims (7)

1. a space passive object transfer method based on throwing, hitting and accessing is characterized by comprising the following steps:

step 1: determining a throwing scheme according to the shielding condition between the current position and the target position of the passive object (3);

and 2, step: selecting the service satellites (2) participating in the task and the range of the hitting point according to the current positions of all the service satellites (2), the task energy and the time constraint;

the specific steps of the step 2 are as follows:

selecting service satellites (2) participating in the task according to the current positions of all the service satellites (2), task energy and time constraints, and respectively selecting a first service satellite and a second service satellite nearby from the service satellites (2) participating in the task according to the current positions and the target positions of the passive objects (3);

when the remaining momentum direction of the first service satellite after grabbing the target can avoid an obstructing object or the path from the second service satellite to the target position can avoid the obstructing object, the first service satellite is selected as a throwing satellite and the second service satellite is selected as a receiving satellite, otherwise, a plurality of hitting satellites are required to be selected nearby;

and step 3: optimizing and obtaining the positions of the hit points and the reference tracks of the service satellites (2) based on the selected service satellites (2);

and 4, step 4: generating an expanded reference track based on the reference track obtained by optimization;

and 5: and (3) executing the throwing scheme determined in the step (1), tracking the extended reference track, and realizing the transfer of the passive object (3).

2. The method for transferring the space passive object based on the throwing striking and accessing as claimed in claim 1, wherein the specific steps of the step 1 are as follows:

when no shielding object exists between the current position of the driven object (3) and the target position or the shielding object between the current position of the driven object (3) and the target position can be adjusted and avoided through the positions of the throwing satellite and the receiving satellite, the beating satellite does not need to be moved to beat; otherwise, the beating satellite needs to be mobilized for relay beating.

3. The method for transferring the space passive object based on the throwing striking and accessing as claimed in claim 2, wherein the number of the striking satellites is several.

4. The method for transferring the space passive objects based on throwing and hitting access is characterized in that the number of hitting satellites depends on task energy, time constraints, the condition of the blocked objects on the throwing and hitting path and the distribution condition of service satellites.

5. The method for transferring the space passive object based on throwing, hitting and accessing as claimed in claim 1, wherein the reference trajectory and the hit point position of each service satellite are calculated by the direct method trajectory optimization method based on the collision system in the step 3.

6. The method for transferring the space passive object based on the throwing striking pick-up as claimed in claim 1, wherein the reference trajectory in step 4 is a segmented continuous system consisting of a plurality of segments divided by the calculated collision time, the segments are discontinuous, and forward expansion and reverse expansion are performed on each segment to obtain the virtual motion trajectory of the collision system before and after the collision time as the expanded reference trajectory.

7. The method for transferring the passive object in the space based on the throwing striking pick-up as claimed in claim 1, wherein in the step 5, the current segment of the extended reference track is tracked according to the state quantity of the service satellite and the state quantity of the passive object, and the next segment of the extended reference track is tracked after the jump when the real collision is detected.

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