Dynamic joint simulation method for electromagnetic docking process of satellites

Abstract

The invention discloses a dynamic joint simulation method for a satellite electromagnetic docking process, and belongs to the field of spacecraft electromagnetic docking dynamics simulation, and the simulation method comprises the following steps: firstly, carrying out the three-dimensional modeling of a spacecraft containing an electromagnet in Ansys Maxwell, and building a spacecraft dynamics simulation model in Syslab; setting simulation boundary conditions and initial conditions; joint simulation is carried out, and a closed-loop dynamic information transmission process of interaction of electromagnetism and dynamics is established; analyzing the motion process of the current step in Syslab in a stepping manner according to the simulation information of the previous step; at the moment, an external control system is allowed to detect and control the electromagnet current; and finally, repeating the joint simulation process, dynamically updating the motion state of the spacecraft until the motion state is stopped, and realizing electromagnetic field and motion process coupled electromagnetic docking dynamics simulation. According to the method, the defect that dynamic simulation of electromagnetic field and motion coupling cannot be solved through traditional electromagnetic simulation can be overcome, and the method better fits the physical actual process of on-orbit docking of spacecrafts.

Description

Technical Field

[0001] The invention relates to the field of spacecraft electromagnetic docking dynamics simulation. Background Art

[0002] With the development of micro-satellites and space stations, the interaction of spacecraft in orbit is becoming more and more frequent. Traditional jet propulsion docking technology has problems such as fuel consumption and plume impact, which have an impact on the life of spacecraft that cannot be ignored. Electromagnetic docking, with its advantages of no fuel consumption and low docking impact, well meets the current needs of high-frequency docking and small-amplitude on-orbit maneuvers. The main difficulties faced by electromagnetic docking are the strong nonlinear characteristics of electromagnetism and the coupling characteristics of electromagnetism and kinematics. At the same time, it is necessary to design the layout of on-board electromagnets to ensure that multiple degrees of freedom can be controlled to achieve stable docking.

[0003] Designing a satellite electromagnetic docking flight program inevitably requires designing a spacecraft electromagnetic docking dynamics control system. In terms of electromagnetic control, since the Biot-Savart law does not have an analytical solution in engineering, and most of the simple magnetic dipole models currently used for theoretical analysis are only applicable at the far-field scale, they cannot meet the accuracy requirements of the small-scale docking process. Therefore, it is necessary to establish a finite element analysis model for electromagnetic field simulation to solve the interaction between electromagnets, and provide a theoretical basis for the spatial layout design, structural design, material selection, dynamics modeling, and derived control system design and structural optimization of electromagnets.

[0004] At present, simulation analysis in most related fields is mainly divided into two parts. First, finite element simulation of electromagnetics is carried out to design the electromagnet and its distribution, and then dynamics and control system simulation analysis is carried out. However, the former is mostly limited to the static field of simple motion, and it is impossible to realize the dynamic closed-loop analysis of the influence between the electromagnetic field and the motion state; the latter mostly uses a simple model obtained by linear approximation as the controlled object, which makes the correlation between electromagnetics and dynamics insufficient, and it is impossible to perform electromagnetic and dynamic coupling dynamic analysis during the electromagnetic docking process. Therefore, it is necessary to combine the two to conduct electromagnetic and dynamic joint simulation. Summary of the invention

[0005] In view of the limitations of the current electromagnetic docking dynamics simulation and analysis methods, the present invention proposes a dynamic joint simulation method for the satellite electromagnetic docking process. Based on the principles of electromagnetic finite element analysis and Newton's laws of motion, Ansys Maxwell software and Syslab software are used to perform dynamic closed-loop joint simulation to improve the accuracy and reliability of the simulation model.

[0006] A dynamic joint simulation method for a satellite electromagnetic docking process comprises the following steps:

[0007] Step 1: Based on the on-board electromagnets and their distribution design, three-dimensional modeling of the spacecraft containing electromagnets is performed in Maxwell.

[0008] Step 2: Establish a dynamic simulation model of the controlled object in Syslab.

[0009] Step 3: Set the simulation boundary conditions and initial conditions in Syslab.

[0010] Step 4: Perform joint simulation, establish an information transmission process, transfer the electromagnet posture data and current data in Syslab to Maxwell, use Maxwell to solve the interaction between the electromagnets and feed back to Syslab to form a signal closed loop.

[0011] Step 5: Dynamically step and analyze the motion process in Syslab.

[0012] Step 6: Allow the external control system to detect and control the current of the electromagnet to achieve the designed control target.

[0013] Step 7: Repeat steps 4, 5, and 6 according to the simulation step size to realize the coupled simulation of the electromagnetic field and posture, and realize the dynamic update of electromagnetic and dynamic information.

[0014] In step 1, the simplified mechanism model established in the Maxwell includes the electromagnetic core, coil, and the spatial distribution of multiple electromagnets, wherein it is necessary to define the electromagnetic core material, core size, spatial position of the electromagnet, number of turns of the energized coil, current size of the coil, number of electromagnets, relative position and relative posture of each other, and spatial grid division. The electromagnetic model allows joint simulation analysis with the dynamic model of Syslab, which respectively represents different information of the simulation object in electromagnetics and dynamics.

[0015] In step 2, the controlled object is a spacecraft containing an electromagnet and capable of electromagnetic docking. According to the dynamic properties of the spacecraft, such as mass and moment of inertia, the dynamic equation of the controlled object is established according to Newton's laws of motion.

[0016] In step 3, the simulation initial conditions refer to the dynamic information such as the initial position and posture of the controlled object and the electromagnetic parameters such as the initial current of the electromagnet; the simulation boundary conditions refer to geometric constraints such as the motion area and the simulation stop conditions.

[0017] In step 4 and step 5, the joint simulation and dynamic stepping process establishes a data interaction model between the rigid body kinematics simulation model and the Ansys Maxwell electromagnetic simulation in Syslab, including two parts: Syslab transmits the simulated rigid body and electromagnet posture information to Maxwell, and Maxwell transmits the simulated electromagnet interaction to Syslab. In this process, the posture output by Syslab in the previous shot during the simulation step will be used as the electromagnet posture information of the current shot Maxwell electromagnetic simulation, and the simulation results of Maxwell will be used as the external force and external torque of the current shot dynamics model to update the spacecraft posture information of the current shot, and then the signal flow forms a dynamic closed-loop structure of stepping iteration. In the joint simulation process, the above-mentioned closed-loop information transmission is performed at each iteration until the simulation ends.

[0018] In step 5, the motion analysis part, based on the forces of each electromagnet output by Maxwell, combined with the distribution of on-board electromagnets set during initial modeling, can calculate the torque vector of the spacecraft in Syslab, and then use the dynamic model established in step 2 to solve the acceleration and angular acceleration of the spacecraft, perform double inertia integration to obtain the position and attitude changes of the spacecraft, and then realize the simulation of the motion process of the spacecraft.

[0019] In step 6, allowing the external control system to control the current refers to changing the electromagnet current value of each step of simulation according to a preset control law.

[0020] In step 7, the coupling of the electromagnetic field and the posture means that the electromagnetic force of each step is affected by the current change, and the current change is determined by a preset control law according to the posture. At the same time, the posture will affect the size of the electromagnetic force (torque) of the electromagnet.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] The present invention proposes a dynamic joint simulation method for the satellite electromagnetic docking process, which adopts Ansys Maxwell software and Syslab software to realize closed-loop dynamic simulation of electromagnetics and dynamics. Different from traditional static electromagnetic simulation and isolated dynamic analysis, the present invention strengthens the connection between electromagnetics and dynamics, is closer to the electromagnetic field and posture coupling in the actual physical process, and makes the simulation more realistic.

[0023] The invention proposes a dynamic joint simulation method for the satellite electromagnetic docking process, which solves the problem that the traditional linearized dynamic analysis and magnetic dipole model are only applicable to far-field analysis; the closed-loop iterative simulation of electromagnetism and dynamics improves the accuracy and reliability of the model, and provides a feasible simulation solution for the problem that the accurate Biot-Savart law model has no analytical solution in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a dynamic joint simulation method for a satellite electromagnetic docking process;

[0025] Figure 2 A schematic diagram of a dual-satellite electromagnetic docking working condition of a specific embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a binary star electromagnetic modeling calculation based on Maxwell software according to a specific embodiment of the present invention;

[0027] Figure 4 A schematic diagram of a double-satellite docking dynamics coordinate system according to a specific embodiment of the present invention; DETAILED DESCRIPTION

[0028] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0029] like Figure 2 As shown, as a specific embodiment of the present invention, the dynamic joint simulation process of the on-orbit electromagnetic docking of two cubesats is described below.

[0030] The pre-processing process of the joint simulation, that is, the specific modeling process corresponding to step 1 and step 2, is as follows:

[0031] (1) Electromagnetic modeling of spacecraft in Maxwell:

[0032] Add two relative coordinate systems RelativeCS1 and RelativeCS2 in Ansys Maxwell as the fixed coordinate systems of the two spacecraft.

[0033] Add design variables in Ansys Maxwell, which are the relative position, relative attitude, and current excitation value of the two spacecraft in three-dimensional space.

[0034] The RelativeCS1 coordinate system is established with reference to the initial Global coordinate system of Ansys Maxwell. To simplify the modeling process, the origin positions and axis orientations of the two coordinate systems can be set to be consistent. The RelativeCS2 coordinate system is established with reference to the RelativeCS1 coordinate system. According to the relative positions and relative attitudes of the two spacecraft, the origin positions and axis orientations of RelativeCS2 are input by posture transformation.

[0035] According to the structural design and geometric relationship of the spacecraft, the spatial distribution and material parameters of the on-board electromagnets are determined, and the three-dimensional models of the respectively connected spacecraft are drawn under RelativeCS1 and RelativeCS2 respectively.

[0036] To facilitate the modeling process, the three-dimensional model needs to be appropriately simplified, retaining only the electromagnet part and its required connection parts, which is referred to as the simplified model below. According to the working environment conditions of the spacecraft, the electromagnetic simulation boundary conditions are set. According to the calculation accuracy and speed requirements, the finite element mesh parameters are set.

[0037] Add the current excitation in the design variable to the corresponding electromagnet.

[0038] Establish a solution method and set the error tolerance range. Select the simplified electromagnets in RelativeCS2 and set the virtual work calculation parameters.

[0039] like Figure 3 As shown, in this embodiment, for a cubic satellite with four electromagnets located at the four corners of the docking surface, the docking surface baffle and the four electromagnets are retained as a three-dimensional model for simulation, hereinafter referred to as a "simplified mechanism". The docking surface baffle plays a geometric connection role and can be used to preliminarily simulate the influence of the front baffle material on the electromagnetic simulation results.

[0040] In the existing electromagnetic docking mechanism, the electromagnet usually uses an energized solenoid with an iron core. When constructing the model geometrically in Maxwell, a cylinder can be used to represent the iron core and a round tube can be used to represent the closely wound spiral. The inner diameter of the round tube should be slightly larger than the diameter of the cylinder, and the two cannot touch each other. Set the cylinder material to electrical pure iron and the round tube material to copper. The baffle used for connection is simplified to a rectangular parallelepiped, and the thickness is extremely small compared to the length and width. No additional material settings are made to prevent affecting the simulation results. Set the excitation to current excitation on the closely wound spiral, select the required simulation current value and current direction, and adjust to the winding type.

[0041] (2) Rigid body dynamics modeling of the spacecraft in Syslab:

[0042] Rigid body dynamics modeling is performed in Syslab, including given parameters such as spacecraft mass, moment of inertia, principal axis of inertia, center of mass position, and size information.

[0043] like Figure 4 As shown, the motion reference coordinate system S1 and the target spacecraft fixed coordinate system S t , Tracking spacecraft fixed coordinate system S c ; Define the relative motion and relative attitude between the two spacecraft in S1 and initialize the position information, respectively in S t , S c The spatial distribution of the electromagnets on the satellite, i.e. the installed position vector, is defined in the paper; the attitude transformation matrix between the three coordinate systems is calculated, and the dynamic equations of the three-axis position vector and the three-axis attitude with respect to external forces and external torques are derived.

[0044] After completing the pre-processing, corresponding to steps 3 to 7, start the specific process of joint simulation:

[0045] A. Set the joint simulation boundary conditions and simulation step size.

[0046] B. Initialize the three-dimensional position and attitude of the tracking spacecraft and the target spacecraft, that is, the initial conditions of the double inertial integration, and set the initial current of the electromagnetic simulation.

[0047] C. Start the Maxwell and Syslab joint simulation platform and wait for the two simulation platforms to achieve communication handshake.

[0048] D. After the two platforms shake hands successfully, the electromagnet current value and the spacecraft's position and posture information at that moment are transmitted from Syslab to Maxwell. Maxwell updates the position and posture of the simplified mechanism in the preset electromagnetic field in the three-dimensional model and the current value in the energized solenoid, resets the calculation force parameters, and calculates the electromagnetic force vector between the electromagnets at that moment.

[0049] E. Return the electromagnetic force vector simulated by Maxwell to Syslab. Syslab calculates the total external force and torque on the spacecraft based on the spacecraft attitude at that moment and the initially set spatial distribution of electromagnets, and calculates the motion process step by step based on the established dynamic equations.

[0050] F. Syslab updates the spacecraft's position and attitude information based on the inertial integral for the next simulation.

[0051] G. The external control system detects and controls the current and changes the electromagnet current value of the next simulation according to the preset control law.

[0052] H. Enter the next simulation step and re-enter step C loop to iterate until the simulation ends.

Claims

1. A dynamic joint simulation method for satellite electromagnetic docking process, characterized in that: The method comprises the following steps: Step 1: Based on the on-board electromagnets and their distribution design, three-dimensional modeling of the spacecraft containing electromagnets is performed in Ansys Maxwell; Step 2: Establish a dynamic simulation model of the controlled object in Syslab; Step 3: Set the simulation boundary conditions and initial conditions in Syslab; Step 4: Perform joint simulation, establish an information transmission process, transfer the electromagnet posture data and current data in Syslab to Maxwell, use Maxwell to solve the interaction between the electromagnets and feed back to Syslab to form a signal closed loop; Step 5: Dynamically analyze the motion process in Syslab; Step 6: Allow the external control system to detect and control the current of the electromagnet to achieve the designed control target; Step 7: Repeat steps 4, 5, and 6 according to the simulation step size to realize the coupled simulation of the electromagnetic field and posture, and realize the dynamic update of electromagnetic and dynamic information.

2. A dynamic joint simulation method for satellite electromagnetic docking process as claimed in claim 1, characterized in that: In step 4 and step 5, the dynamic joint simulation concept refers to establishing a data interaction model between the rigid body kinematics simulation model and the Ansys Maxwell electromagnetic simulation in Syslab, including two parts: Syslab transmits the simulated rigid body and electromagnet posture information to Maxwell, and Maxwell transmits the simulated electromagnet interaction to Syslab. In this process, when Syslab simulates stepping, the posture output of the previous simulation step will be used as the electromagnet posture information of the current step simulation Maxwell electromagnetic simulation, and the simulation results of Maxwell will be used as the external force and external torque of the current step simulation dynamic model to update the spacecraft posture information of the current step simulation, and then the signal flow forms a dynamic closed-loop structure of step iteration, thereby making up for the disadvantage that only Maxwell software cannot perform dynamic simulation. In the joint simulation process, the above closed-loop information transmission is performed at each iteration until the simulation ends.

3. A dynamic joint simulation method for satellite electromagnetic docking process as claimed in claim 1, characterized in that: In step 5, the motion analysis part, based on the forces of each electromagnet output by Maxwell, combined with the distribution of on-board electromagnets set during initial modeling, can calculate the torque vector of the spacecraft in Syslab, and then use the dynamic model established in step 2 to solve the acceleration and angular acceleration of the spacecraft, perform double inertia integration to obtain the position and attitude changes of the spacecraft, and then realize the simulation of the motion process of the spacecraft.

4. A dynamic joint simulation method for satellite electromagnetic docking process as claimed in claim 1, characterized in that: The present invention is designed to simulate the docking dynamics under the coupling of electromagnetic field and posture. The coupling of electromagnetic field and posture means that the electromagnetic force exerted on the spacecraft in each step of simulation is affected by the change of current, and the change of current is determined by a preset control law according to the posture. At the same time, the posture will affect the size of the electromagnetic force and electromagnetic torque of the electromagnet.

5. The method for dynamic joint simulation of satellite electromagnetic docking process according to claim 1, characterized in that: In step 1, the three-dimensional modeling of the spacecraft containing electromagnets in the Maxwell software is mainly aimed at the electromagnetic actuator of the spacecraft, that is, the electromagnetic simulation static modeling of the electromagnet, which has nothing to do with the dynamic characteristics of the spacecraft.

6. A dynamic joint simulation method for satellite electromagnetic docking process as claimed in claim 1, characterized in that: In step 6, allowing the external control system to control the current means changing the electromagnet current value of each simulated step according to a preset control law, where the control law is a control method used for simulation of specific working conditions.

Images