Small celestial body sampling process dynamics and control simulation method based on particle dynamics

Abstract

The invention discloses a small celestial body sampling process dynamics and control simulation method based on particle dynamics. The method comprises the following steps: establishing a small celestial body particle dynamics model and a detector system flexible multi-body dynamics model; and establishing a particle dynamics-multi-body dynamics-control coupling simulation model, and realizing dynamics and control joint simulation solution calculation in the small celestial body sampling process by using a numerical integration algorithm. In order to solve the multidisciplinary, system-level dynamics and control joint simulation problem in the small celestial body sampling process, mathematical simulation models of small celestial body star soil particle flow dynamics, detector flexible multi-body dynamics, detector attitude and orbit control and mechanical arm control are provided, and the interface relation among the models is defined; multi-disciplinary and system-level joint simulation of particle dynamics-multi-body dynamics-control in the small celestial body sampling process is realized, and an important technical means is provided for small celestial body star soil weathered layer particle characteristic simulation and process dynamics and control coupling characteristic analysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of space relative navigation, and in particular relates to a small celestial body sampling process dynamics and control simulation method based on particle dynamics. Background Art

[0002] Small celestial bodies refer to smaller celestial bodies orbiting the sun. They are the most numerous celestial bodies in the solar system discovered so far. Scientists generally believe that small celestial bodies are the remnants of matter condensed from the original solar nebula after the formation of the solar system, and they are likely to retain information about the original solar system. Research on small celestial bodies can promote breakthroughs in basic scientific issues such as the origin of the solar system, planetary evolution, and the origin of life, and is a frontier and hot topic in current space exploration.

[0003] The sampling process is a key link in the small celestial body exploration mission with high technical difficulty, many uncertainties and high risk factors. It involves complex dynamics and control behaviors such as contact collision, structural vibration, multi-body motion, attitude control, and robotic arm control. Since it is difficult to accurately simulate the special weak gravitational field environment of small celestial bodies on the ground, it is urgent to simulate the mechanical properties of the small celestial body's soil and the dynamics and control coupling characteristics of the sampling process through simulation methods to ensure the rationality of the scheme design and the safety of in-orbit flight.

[0004] The main problems with current methods are:

[0005] (1) In terms of modeling of celestial soil properties, the mechanical properties of the soil on the surface of small celestial bodies are crucial for safe attachment and successful sampling. Unlike large celestial bodies such as the Moon and Mars, small celestial bodies are small in size and have very weak gravitational fields. Their surfaces are usually composed of relatively loose weathering particles and smaller gravel. Even under low-speed collision conditions, the celestial soil of small celestial bodies will still deform, flow, or cause particle splashing, which brings challenges and risks to contact detection. The existing celestial soil modeling mainly adopts the equivalent mechanical contact collision dynamics modeling method based on the continuum theory, which is unable to simulate the discontinuous particle dynamics behavior of the celestial soil weathering layer of small celestial bodies, such as flow and splashing.

[0006] (2) In terms of joint simulation of dynamics and control, although there are currently relevant professional software available for particle dynamics, multi-body dynamics and control modeling, such as discrete element simulation software EDEM, multi-body dynamics simulation software ADAMS, scientific computing software Matlab, etc. However, there is still a lack of comprehensive simulation software or research methods for the system-level, multi-disciplinary dynamics and control simulation requirements required by the small celestial body sampling process. The main reason is that various commercial software can meet the modeling work within the professional scope of the software itself, but cannot truly simulate the complex coupling characteristics between the subsystems of the sampling process. For example, the discrete element simulation software EDEM itself can realize the simulation of small celestial body star soil particle dynamics and the coupling simulation of single mass body restricted motion and particle flow. Although it has a joint simulation interface with ADAMS, it does not have the modeling capability of the control system. Summary of the invention

[0007] The technology of the present invention solves the problem: overcomes the shortcomings of the prior art, provides a small celestial body sampling process dynamics and control simulation method based on particle dynamics, and aims at the multidisciplinary, system-level dynamics and control joint simulation problem of the small celestial body sampling process. A mathematical simulation model of the small celestial body soil particle flow dynamics, the detector flexible multi-body dynamics, the detector attitude and orbit control and the robotic arm control is given, and the interface relationship between them is defined, thereby realizing the multidisciplinary, system-level joint simulation of particle dynamics-multi-body dynamics-control in the small celestial body sampling process, and providing an important technical means for simulating the particle characteristics of the small celestial body soil weathering layer and analyzing the coupling characteristics of the process dynamics and control.

[0008] In order to solve the above technical problems, the present invention discloses a small celestial body sampling process dynamics and control simulation method based on particle dynamics, comprising:

[0009] Establish a small celestial particle dynamics model and a flexible multi-body dynamics model for the detector system;

[0010] Based on the small celestial particle dynamics model and the flexible multi-body dynamics model of the detector system, a particle dynamics-multi-body dynamics-control coupling simulation model is established;

[0011] Based on the particle dynamics-multibody dynamics-control coupling simulation model, the numerical integration algorithm is used to realize the joint simulation solution and calculation of the dynamics and control of the small celestial body sampling process, and the body posture, solar wing vibration, particle contact force, body control force and robotic arm control force are obtained as the basis for the design and optimization of the small celestial body sampling scheme.

[0012] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics, the small celestial body particle dynamics model is expressed as follows:

[0013]

[0014] F h =f contact (F n ,F t )

[0015] Among them, F n represents the particle normal collision force, E * represents Young's modulus, R * represents the equivalent radius, δ n Indicates the normal overlap, m * represents the equivalent mass, represents the normal component of the relative velocity, β represents the coefficient, S n represents normal stiffness; F t represents the particle tangential collision force, S t represents the tangential stiffness, δ t represents the tangential overlap, Represents the tangential component of the relative velocity; F h represents the collision force and torque between the sampler at the end of the robotic arm and the small celestial body, f contact () represents the calculation function of the resultant force and torque acting on the sampler contact geometry at the end of the robotic arm.

[0016] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics,

[0017]

[0018] Here, e represents the coefficient of restitution.

[0019] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics,

[0020]

[0021] Among them, G * represents the equivalent shear modulus.

[0022] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics, the flexible multi-body dynamics model of the detector system is expressed as follows:

[0023]

[0024] Where κ represents the parameter vector set, κ=[v0,ω0,q,η] T , v0 represents the velocity of the body, ω0 represents the angular velocity of the body, q represents the joint angle of the robot arm, η represents the elastic vibration mode of the solar wing; M(q) represents the generalized mass matrix, t represents time, The skew-symmetric matrix representing the angular velocity of the body, represents the first 6 rows of the block matrix of M(q), q1 represents the joint angle of the first joint of the robot arm, q2 represents the joint angle of the second joint of the robot arm, It represents the skew-symmetric matrix of the velocity of the main body, I represents the unit matrix, K represents the stiffness matrix of the solar wing, F represents the external force and torque acting on the system, τ represents the joint torque of the robot arm, and J represents the Jacobian matrix at the end of the robot arm.

[0025] In the above-mentioned small body sampling process dynamics and control simulation method based on particle dynamics, the particle dynamics-multibody dynamics-control coupling simulation model includes: small body particle dynamics model, detector system flexible multibody dynamics model, body attitude and orbit control model and robotic arm control model.

[0026] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics, the body attitude and orbit control model is expressed as follows: F = f GNC (v0,ω0); where F represents the control force and torque acting on the body, f GNC () represents the body attitude and trajectory control function.

[0027] In the above-mentioned small celestial body sampling process dynamics and control simulation method based on particle dynamics, the robotic arm control model is expressed as follows: Among them, f JXB () represents the robot arm control function.

[0028] The present invention has the following advantages:

[0029] (1) The present invention discloses a method for simulating the dynamics and control of the small body sampling process based on particle dynamics, and realizes the discontinuous contact collision modeling of the small body soil under weak gravity conditions based on the discrete element theory method, which breaks through the limitation that the current multi-body dynamics modeling method can only consider the contact collision of continuum bodies (such as the contact collision between the sampler and hard ground such as large rocks), but cannot be applied to the modeling of the characteristics of small body soil.

[0030] (2) The present invention discloses a method for simulating the dynamics and control of a small body sampling process based on particle dynamics, which can realize the modeling of the small body soil characteristics, the multi-body motion characteristics of the detector, the vibration characteristics of the solar wing, the control and the mutual coupling characteristics. It breaks through the limitation that the current research method can only perform local modeling and analysis, but cannot meet the complex multidisciplinary and system-level modeling and simulation requirements of the small body sampling process.

[0031] (3) The present invention discloses a method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics. According to the multi-time scale characteristics of particle dynamics, multi-body dynamics and control models and the different requirements for simulation precision, a variable-step-size and high-efficiency simulation method is provided, which breaks through the limitation of low simulation efficiency caused by fixed communication step-size in current joint simulation between commercial software. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of a method for simulating dynamics and control of a small celestial body sampling process based on particle dynamics in an embodiment of the present invention;

[0033] Figure 2 is a relationship diagram of a particle dynamics and contact geometry collision interface in an embodiment of the present invention;

[0034] Figure 3 It is a particle dynamics-multibody dynamics-control coupling simulation interface relationship diagram in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of a small celestial body sampling process in an embodiment of the present invention;

[0036] Figure 5 This is a simulation flow chart of a small celestial body sampling process in an embodiment of the present invention;

[0037] Figure 6 It is a schematic diagram of a numerical integration step size in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0039] One of the core ideas of the present invention is: a dynamics and control simulation method for the small celestial body sampling process based on particle dynamics is disclosed, which can simulate discontinuous particle dynamics behaviors such as flow and splashing of the regolith weathering layer of small celestial bodies, and is suitable for the unique regolith mechanical properties of small celestial bodies; it can simulate the dynamics and control coupling behaviors involved in the small celestial body sampling process in terms of contact collision, structural vibration, multi-body motion, attitude control, robotic arm control, etc., and meet the multi-disciplinary and system-level simulation requirements for the design and evaluation of small celestial body sampling schemes; it can select a variable step size to increase the simulation efficiency according to the multi-time scale characteristics of models such as particle dynamics, multi-body dynamics and control and different requirements for the degree of simulation precision.

[0040] Reference Figure 1 In this embodiment, the small celestial body sampling process dynamics and control simulation method based on particle dynamics includes:

[0041] Step 1: Establish a small celestial particle dynamics model and a flexible multi-body dynamics model of the detector system.

[0042] In this embodiment, the small celestial particle dynamics model and the flexible multi-body dynamics model of the detector system interact with each other by generating geometric bodies of the contact and collision parts, such as Figure 2 That is, the motion of the geometric body is determined by the flexible multi-body dynamics model of the detector system, and the position, velocity, attitude and angular velocity of the geometric body are output to the small celestial particle dynamics model. The concentrated force and torque of the particle flow acting on the geometric body are calculated by the small celestial particle dynamics model, and fed back to the flexible multi-body dynamics model of the detector system for dynamic and kinematic solutions.

[0043] The dynamic model of small celestial particles is expressed as follows:

[0044]

[0045] F h =f contact (F n ,F t )

[0046] Among them, F n represents the particle normal collision force, E * represents Young's modulus, R * represents the equivalent radius, δ n Indicates the normal overlap, m * represents the equivalent mass, Represents the normal component of relative velocity; F t represents the particle tangential collision force, δ t represents the tangential overlap, Represents the tangential component of the relative velocity; F h represents the collision force and torque between the sampler at the end of the robotic arm and the small celestial body, f contact () represents the calculation function of the resultant force and torque of the particle on the contact geometry of the sampler at the end of the robot arm; β represents the coefficient, e represents the coefficient of restitution; S n represents the normal stiffness, S t represents the tangential stiffness, G * represents the equivalent shear modulus.

[0047] The mechanical model of the detector is as follows Figure 3 As shown, where Σ L is the ground coordinate system of the small celestial body, Σ Bis the detector body coordinate system. Aiming at the time-varying multi-body motion of the detector sampling process, based on the mixed coordinate method and using the second-kind Lagrangian equation, a flexible multi-body dynamics model of the detector system is established, which is expressed as follows:

[0048]

[0049] Where κ represents the parameter vector set, κ=[v0,ω0,q,η] T , v0 represents the velocity of the body, ω0 represents the angular velocity of the body, q represents the joint angle of the robot arm, η represents the elastic vibration mode of the solar wing; M(q) represents the generalized mass matrix, t represents time, The skew-symmetric matrix representing the angular velocity of the body, represents the first 6 rows of the block matrix of M(q), q1 represents the joint angle of the first joint of the robot arm, q2 represents the joint angle of the second joint of the robot arm, It represents the skew-symmetric matrix of the velocity of the main body, I represents the unit matrix, K represents the stiffness matrix of the solar wing, F represents the external force and torque acting on the system, τ represents the joint torque of the robot arm, and J represents the Jacobian matrix at the end of the robot arm.

[0050] Step 2: Based on the small celestial body particle dynamics model and the flexible multi-body dynamics model of the detector system, a particle dynamics-multi-body dynamics-control coupling simulation model is established.

[0051] In this embodiment, the particle dynamics-multibody dynamics-control coupling simulation model interface relationship is as follows: Figure 4 As shown in FIG. 1 , the particle dynamics-multibody dynamics-control coupling simulation model mainly includes: a small celestial particle dynamics model, a detector system flexible multibody dynamics model, a body attitude and orbit control model, and a robotic arm control model. The small celestial particle dynamics model and the detector system flexible multibody dynamics model refer to the description in step 1 above.

[0052] The body attitude and trajectory control model is expressed as follows:

[0053] F=f GNC (v0,ω0)

[0054] Where F represents the control force and torque acting on the body, f GNC () represents the body attitude and trajectory control function.

[0055] The robot arm control model is expressed as follows:

[0056]

[0057] Among them, f JXB () represents the robot arm control function.

[0058] Step 3, based on the particle dynamics-multibody dynamics-control coupling simulation model, use the numerical integration algorithm to realize the dynamics and control joint simulation solution calculation of the small celestial body sampling process, and obtain the body posture, solar wing vibration, particle contact force, body control force and robotic arm control force as the basis for the design and optimization of the small celestial body sampling scheme.

[0059] In this embodiment, based on the particle dynamics-multibody dynamics-control coupling simulation model established in step 2, a numerical integration algorithm flow of discrete element-multibody dynamics-control coupling simulation of small celestial body sampling process is given. Figure 5 As shown, the numerical integration algorithm process is as follows:

[0060] The simulation starting point is the distance between the detector and the ground coordinate system of the small celestial body Σ L At a hovering point at a certain height, the probe approaches the surface of the small celestial body under the control of the body's attitude and orbit, and multi-body dynamics-control joint simulation is used; when the front end of the robotic arm sampling comes into contact with the star surface, particle dynamics-multi-body dynamics-control joint simulation is used; when the sampling time and normal contact force meet the mission requirements, the probe begins to fly around and leave the surface of the small celestial body. When the front end of the robotic arm sampling separates from the star surface, multi-body dynamics-control joint simulation is used until the end of the simulation.

[0061] According to the multi-time scale characteristics of particle dynamics, multi-body dynamics and control models (small celestial particle dynamics model, detector system flexible multi-body dynamics model, body attitude and orbit control model and robotic arm control model) and different requirements for simulation precision, the variable step size integration method is selected to increase the simulation efficiency, such as Figure 6 As shown in the figure. The small celestial particle dynamics model has the highest requirement for simulation precision. It is a variable step simulation. The simulation step ΔT_DEM is determined by the Rayleigh criterion according to the diameter of the particle (generally less than 0.0001s); the second is the flexible multi-body dynamics model of the detector system. The simulation step ΔT_ADAMS needs to balance the coupling stability and data smoothness with the small celestial particle dynamics model and the simulation efficiency. It can be set to a small step (generally less than 0.001s) during the contact process between the detector and the particle, and can be set to a large step (0.01s order of magnitude) during the non-contact process between the detector and the particle; the third is the robotic arm control model (0.01s order of magnitude), and finally the body attitude and orbit control model (0.1s order of magnitude).

[0062] In this embodiment, the overall implementation process of the small celestial body sampling process dynamics and control simulation method based on particle dynamics is as follows: First, according to the surface mechanical characteristic parameters (Young's modulus E * , equivalent radius R * , equivalent mass m *, restitution coefficient e, tangential stiffness S t , equivalent shear modulus G * ), and the normal overlap δ of the sampler contact geometry at the end of the manipulator invading the soil particles calculated by the flexible multi-body dynamics model of the detector system n and the tangential overlap δ t , bring it into the small celestial particle dynamics model, and calculate the particle normal collision force F n and particle tangential collision force F t , and further calculate the collision force and torque F between the end sampler of the robotic arm and the small celestial body h Among them, according to the body velocity v0 and angular velocity ω0 calculated by the flexible multi-body dynamics model of the probe system, the body attitude and trajectory control model F = f GNC (v0, ω0), calculate the control force and torque F acting on the body; according to the flexible multi-body dynamics model of the detector system, the joint angle q and joint angular velocity of the manipulator are calculated Bring in the robotic arm control model The joint torque τ of the robot arm is calculated. h , F and τ are substituted into the flexible multi-body dynamics model of the detector system to obtain the particle dynamics-multi-body dynamics-control coupling simulation model. Finally, based on the established particle dynamics-multi-body dynamics-control coupling simulation model, the numerical integration algorithm is used to realize the dynamics and control joint simulation solution calculation of the small celestial body sampling process, and the parameters such as the body attitude, solar wing vibration, particle contact force, body control force, and robotic arm control force are obtained as the basis for the design and optimization of the small celestial body sampling plan.

[0063] In summary, in order to solve the problem of multidisciplinary and system-level joint dynamics and control simulation of the small body sampling process, the present invention provides a dynamics and control simulation method for the small body sampling process based on particle dynamics, and provides mathematical simulation models of the small body soil particle flow dynamics, the detector flexible multi-body dynamics, the detector attitude and orbit control and the robotic arm control, namely, the small body particle dynamics model, the detector system flexible multi-body dynamics model, the main body attitude and orbit control model and the robotic arm control model; and defines the interface relationship between the models, thereby realizing the multidisciplinary and system-level joint simulation of particle dynamics-multi-body dynamics-control in the small body sampling process, which provides an important technical means for simulating the particle characteristics of the small body soil weathering layer and analyzing the coupling characteristics of the process dynamics and control.

[0064] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0065] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A small celestial body sampling process dynamics and control simulation method based on particle dynamics, characterized in that: include: Establish a small celestial particle dynamics model and a flexible multi-body dynamics model for the detector system; Based on the small celestial particle dynamics model and the flexible multi-body dynamics model of the detector system, a particle dynamics-multi-body dynamics-control coupling simulation model is established; Based on the particle dynamics-multibody dynamics-control coupling simulation model, the numerical integration algorithm is used to realize the joint simulation solution and calculation of the dynamics and control of the small celestial body sampling process, and the body posture, solar wing vibration, particle contact force, body control force and robotic arm control force are obtained as the basis for the design and optimization of the small celestial body sampling scheme.

2. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 1, characterized in that: The dynamic model of small celestial particles is expressed as follows: F h =f contact (F n ,F t ) Among them, F n represents the particle normal collision force, E * represents Young's modulus, R * represents the equivalent radius, δ n Indicates the normal overlap, m * represents the equivalent mass, represents the normal component of the relative velocity, β represents the coefficient, S n represents normal stiffness; F t represents the particle tangential collision force, S t represents the tangential stiffness, δ t represents the tangential overlap, Represents the tangential component of the relative velocity; F h represents the collision force and torque between the sampler at the end of the robotic arm and the small celestial body, f contact () represents the calculation function of the resultant force and torque acting on the sampler contact geometry at the end of the robotic arm.

3. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 2 is characterized in that: Here, e represents the coefficient of restitution.

4. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 2, characterized in that: Among them, G * represents the equivalent shear modulus.

5. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 2, characterized in that: The flexible multi-body dynamics model of the detector system is expressed as follows: Where κ represents the parameter vector set, κ=[v0,ω0,q,η] T , v0 represents the velocity of the body, ω0 represents the angular velocity of the body, q represents the joint angle of the robot arm, η represents the elastic vibration mode of the solar wing; M(q) represents the generalized mass matrix, t represents time, The skew-symmetric matrix representing the angular velocity of the body, represents the first 6 rows of the block matrix of M(q), q1 represents the joint angle of the first joint of the robot arm, q2 represents the joint angle of the second joint of the robot arm, It represents the skew-symmetric matrix of the velocity of the main body, I represents the unit matrix, K represents the stiffness matrix of the solar wing, F represents the external force and torque acting on the system, τ represents the joint torque of the robot arm, and J represents the Jacobian matrix at the end of the robot arm.

6. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 5, characterized in that: Particle dynamics-multibody dynamics-control coupling simulation model, including: small celestial body particle dynamics model, detector system flexible multibody dynamics model, body attitude and orbit control model and robotic arm control model.

7. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 6, characterized in that: The body attitude and trajectory control model is expressed as follows: F = f GNC (v0,ω0); where F represents the control force and torque acting on the body, f GNC () represents the body attitude and trajectory control function.

8. The method for simulating the dynamics and control of a small celestial body sampling process based on particle dynamics according to claim 6, characterized in that: The robot arm control model is expressed as follows: Among them, f JXB () represents the robot arm control function.

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