No-drag control ground semi-physical simulation equivalent verification method and system

Abstract

The invention provides a drag-free control ground semi-physical simulation equivalent verification method and a drag-free control ground semi-physical simulation equivalent verification system. Firstly, a ground semi-physical simulation platform is designed, a five-degree-of-freedom motion platform is adopted to simulate five-degree-of-freedom motion of a drag-free satellite, and a two-stage suspension wire suspension pendulum structure is adopted to hitch a test mass to simulate the zero-gravity suspension state of the test mass in the drag-free satellite. Ground semi-physical simulation platform control loops are designed to be in one-to-one equivalent correspondence with space gravitational wave detection control loops in the drag-free satellite; and finally, determining controller parameters of the ground drag-free control loop based on the parameter scaling determined by the Pi theorem theory. A system composed of a designed ground semi-physical simulation platform and a control loop of the ground semi-physical simulation platform is adopted to conduct ground simulation on the drag-free satellite, and due to the fact that the system conducts equivalence from the aspects of dynamics equivalence, control loop equivalence, controller parameter equivalence and the like, the precision of equivalent verification of the ground semi-physical simulation system on the drag-free satellite is improved.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace control technology, and specifically relates to a drag-free control ground semi-physical simulation equivalent control method and system, which is used to simulate and verify the drag-free controller of the on-orbit dual-parameter inspection quality. Background Art

[0002] In recent years, with the development of my country's space technology, the space gravitational wave detection plan and gravity field measurement plan proposed by my country have both used drag-free control technology. This control technology has important applications in many space science research and engineering tasks and is of great significance to the development of my country's space science. The residual acceleration index of the sensitive axis direction of the drag-free control satellite is extremely high, and the accuracy within the measurement frequency band needs to be better than 1×10 -15 m / s 2 / Hz 1 / 2 In 2015, the LISA Pathfinder satellite was launched, achieving a residual acceleration level better than 3×10 -14 m / s 2 / Hz 1 / 2 The residual acceleration disturbance index is verified, and the residual acceleration index achieved by the Tianqin-1 and Taiji-1 satellites launched by my country in 2019 in the measurement frequency band is better than 1×10 -8 m / s 2 / Hz 1 / 2 It can be seen that there is still a big gap between my country and foreign countries in terms of drag-free control engineering.

[0003] Ground-based experimental verification is a crucial component of space gravitational wave detection and one of the primary means of ensuring spacecraft function properly in real-world environments and meet mission requirements. Currently, ground-based semi-physical simulation platforms primarily include drop towers, parabolic aircraft, neutral buoyancy tanks, air flotation, and wire suspension. Drop towers simulate space microgravity with high accuracy, but for a short duration, lasting only a few seconds. Parabolic aircraft simulate space microgravity with high accuracy, but at a high experimental cost. Neutral buoyancy tanks can simulate microgravity for extended periods, but the dynamic interaction between the simulation platform and the surrounding buoyancy tank fluid creates significant interference factors, making them ineffective for realistic and effective dynamic simulations. Air flotation satellite simulation platforms can maintain microgravity for extended periods, are cost-effective, and are reusable, but their uneven gas release can result in increased disturbance noise. Wire suspension simulates space microgravity for extended periods, is simple in structure, and can provide high microgravity levels, making it widely used in ground-based testing of inertial sensors for space gravitational wave detection.

[0004] The present invention provides a ground-based semi-physical simulation equivalent verification scheme for drag-free control based on a wire suspension method, which performs equivalence from multiple angles, including dynamic equivalence, control loop equivalence, and controller parameter equivalence, thereby improving the accuracy of ground-based semi-physical simulation system for equivalent verification of drag-free satellites. Summary of the Invention

[0005] In view of this, the present invention provides a method and system for equivalent verification of drag-free control ground semi-physical simulation, which can ensure the accuracy of equivalent verification of drag-free satellites by the ground semi-physical simulation system.

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

[0007] A drag-free control ground semi-physical simulation equivalent verification method, comprising:

[0008] Step 1: Design a ground-based physical-in-the-loop simulation platform, including: using a five-degree-of-freedom motion platform to simulate the five degrees of freedom of the drag-free satellite, including two horizontal degrees of freedom and three rotational degrees of freedom; using a two-stage suspension wire suspension pendulum structure to attach the test mass to simulate the zero-gravity suspension state of the test mass in the drag-free satellite, and the test mass can move in four degrees of freedom, including two translations along the sensitive axis and two rotations about the suspension wire;

[0009] Step 2: Design a one-to-one correspondence between the ground-based semi-physical simulation platform control loop and the space gravitational wave detection control loop in the drag-free satellite, including: the ground motion platform attitude control loop is equivalent to the space satellite attitude control loop, the ground drag-free control loop is equivalent to the space drag-free control loop, and the ground electrostatic control loop is equivalent to the space electrostatic suspension control loop. The ground electrostatic control loop uses a pair of static electrode plates fixed on the five-degree-of-freedom motion platform to simulate the electrostatic control of the suspension attitude of the proof mass by the static electrode plates of the electrode cage in the drag-free satellite, and the control direction is the non-gravity direction of the two non-sensitive axes of the proof mass. The displacement sensor in the ground electrostatic control loop is used to simulate the displacement detection of the proof mass in the drag-free satellite.

[0010] Step 3: Based on the π-theorem theory, determine the minimum number of parameters that characterize the complete dynamics of the drag-free satellite, convert the parameters into dimensionless parameters, and determine the scaling ratio of the dimensionless parameters between the ground-based semi-physical simulation platform and the drag-free satellite;

[0011] Step 4: Determine controller parameters of the ground no-drag control loop: Utilize the scaling ratio to convert the controller parameters of the spatial no-drag control loop into controller parameters of the ground no-drag control loop;

[0012] Step 5: Use the ground-based semi-physical simulation platform and its control loop to complete the ground simulation of the drag-free satellite.

[0013] Preferably, the secondary suspended wire pendulum structure includes two secondary suspended wire pendulums; each secondary suspended wire pendulum includes a primary suspension wire, a balancing arm is suspended under the primary suspension wire, one end of the balancing arm is connected to the balancing mass block, and the other end is connected to the secondary suspension wire, and an inspection mass is suspended under the secondary suspension wire.

[0014] Preferably, each control loop constructed in step 2 is:

[0015] In the ground drag-free control loop, the displacement changes of the test mass sensitive axis detected by the displacement sensor in both positive and negative directions are decoupled to the X-axis and Y-axis of the motion platform. After the displacement changes are subtracted from the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform, the control variables are generated by the X-axis controller and the Y-axis controller, and then output to the five-degree-of-freedom motion platform to control the relative position change between the five-degree-of-freedom motion platform and the test mass.

[0016] The attitude control loop of the ground motion platform does not require controller design. The five-degree-of-freedom motion platform is driven by the motion platform actuator to track the movement of the mass-sensitive axis.

[0017] In the ground electrostatic control circuit, based on the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion stage and the displacement detection results of the proof mass, the relative position of the non-sensitive axis of the proof mass and the five-degree-of-freedom motion stage is controlled by the electrostatic electrode plate to remain unchanged.

[0018] Preferably, in step 3, the minimum number of parameters characterizing the complete dynamics of a drag-free satellite is determined according to the π theorem theory, and the mass and size are selected from them; by adjusting the mass and size of the ground semi-physical simulation platform, the ground semi-physical simulation platform meets the required residual acceleration index requirements and displacement index requirements.

[0019] Preferably, in step 4, the controller in the ground drag-free control loop is a PID controller; wherein,

[0020] The conversion formula of the PID parameters of the displacement controller is:

[0021]

[0022] in, are the PID parameters of the ground drag-free controller, is the PID parameter of the spatial drag-free controller; m S is the total mass of the untowed satellite, m G is the mass of the five-degree-of-freedom motion platform.

[0023] The present invention also provides a drag-free control ground semi-physical simulation equivalent verification system, which includes: a ground semi-physical simulation platform and a ground semi-physical simulation platform control loop;

[0024] The ground-based semi-physical simulation platform includes a five-degree-of-freedom motion platform, a two-stage suspended pendulum structure, and a test mass;

[0025] The five-degree-of-freedom motion platform simulates the five-degree-of-freedom motion of a drag-free satellite, including two horizontal degrees of freedom and three rotational degrees of freedom;

[0026] The two-stage suspension wire pendulum structure is connected to the test mass, which is used to simulate the zero-gravity suspension state of the test mass in the drag-free satellite, and the test mass can move with four degrees of freedom, including two translations along the sensitive axis and two rotations around the suspension wire;

[0027] The ground control loop corresponds one-to-one with the space gravitational wave detection control loop in the drag-free satellite, including: the ground motion platform attitude control loop is equivalent to the space satellite attitude control loop, the ground drag-free control loop is equivalent to the space drag-free control loop, and the ground electrostatic control loop is equivalent to the space electrostatic suspension control loop; the ground electrostatic control loop uses a pair of static electrode plates fixed on the five-degree-of-freedom motion platform to simulate the electrostatic control of the suspension attitude of the proof mass by the static electrode plates of the electrode cage in the drag-free satellite, and the control direction is the non-gravity direction of the two non-sensitive axes of the proof mass; the displacement sensor in the ground electrostatic control loop is used to simulate the displacement detection of the proof mass in the drag-free satellite;

[0028] The control parameters in the ground drag-free control loop are obtained by converting the controller parameters in the drag-free satellite according to the scaling ratio of the dimensionless parameters between the ground semi-physical simulation platform and the drag-free satellite determined by the π theorem theory.

[0029] Preferably, the secondary suspended wire pendulum structure includes two secondary suspended wire pendulums; each secondary suspended wire pendulum includes a primary suspension wire, a balancing arm is suspended under the primary suspension wire, one end of the balancing arm is connected to the balancing mass block, and the other end is connected to the secondary suspension wire, and an inspection mass is suspended under the secondary suspension wire.

[0030] Preferably, the ground drag-free control loop includes a sensitive axis direction decoupling module and a drag-free controller; the sensitive axis direction decoupling module decouples the displacement changes in the positive and negative directions of the sensitive axis of the proof mass detected by the displacement sensor to the X-axis and Y-axis of the motion platform, and subtracts the displacements from the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform to obtain the relative position change between the five-degree-of-freedom motion platform and the proof mass, and outputs the result to the drag-free controller; the drag-free controller includes an X-axis controller and a Y-axis controller, generates a control variable, and outputs the control variable to the five-degree-of-freedom motion platform;

[0031] The ground motion platform attitude control loop drives the five-degree-of-freedom motion platform to track and test the movement of the mass-sensitive axis only through the motion platform actuator;

[0032] The ground electrostatic control circuit includes an electrostatic electrode plate, a displacement sensor and an electrostatic electrode plate controller; the electrostatic electrode plates are a pair and are fixed on a five-degree-of-freedom motion platform; the displacement sensor is used to detect the displacement of the inspection mass; the electrostatic electrode plate controller controls the relative position of the non-sensitive axis of the inspection mass and the five-degree-of-freedom motion platform to remain unchanged through the electrostatic electrode plate based on the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform and the displacement detection results of the inspection mass.

[0033] Preferably, the displacement controller in the drag-free controller is a PID controller, and the PID parameters are:

[0034]

[0035] in, are the PID parameters of the ground drag-free controller, is the PID parameter of the spatial drag-free controller; m S is the mass of the untowed satellite, m G is the mass of the five-degree-of-freedom motion platform.

[0036] Beneficial effects:

[0037] (1) The drag-free control ground semi-physical simulation equivalent verification scheme designed by the present invention performs equivalence from multiple angles, including dynamic equivalence, control loop equivalence, and controller parameter equivalence, thereby improving the accuracy of the ground semi-physical simulation system for equivalent verification of drag-free satellites.

[0038] (2) Through analysis, the present invention adopts a five-degree-of-freedom motion platform to simulate the 5 degrees of freedom of the satellite body, and a secondary suspended test mass to simulate the 4-degree-of-freedom movement of the dual test mass in space, instead of selecting a six-degree-of-freedom motion platform. This is because the test mass mainly simulates the direction of the sensitive axis, which is perpendicular to the direction of gravity and does not exist in the direction of gravity. Therefore, there is no need for the five-degree-of-freedom motion platform to move along the direction of gravity to achieve better semi-physical simulation equivalence. Therefore, the present invention eliminates the less necessary equivalent design and ensures equivalence when the structural complexity allows.

[0039] (3) The present invention can make controller parameters equivalent according to the scaling ratio determined by the π theorem theory, thereby ensuring the equivalence of the controller control effect.

[0040] (4) The present invention verifies the similarity between the drag-free control ground semi-physical simulation system of the present invention and the drag-free satellite based on the dynamic similarity theory. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the design idea of ​​the present invention.

[0042] Figure 2 It is a schematic diagram of the kinetic equivalent;

[0043] Figure 3 It is a structural schematic diagram of the five-degree-of-freedom motion platform of the present invention.

[0044] Figure 4 It is a structural schematic diagram of the secondary suspended wire pendulum structure of the present invention.

[0045] Figure 5 This is an equivalent schematic diagram of the control loop of the present invention.

[0046] Figure 6 This is a schematic diagram of PID parameter equivalence. DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0048] The present invention provides a drag-free control ground semi-physical simulation equivalent verification solution, which performs equivalent design from multiple angles such as motion equivalence, controller equivalence, parameter equivalence, etc. Figure 1 As shown, specifically including:

[0049] 1. Design a ground-based semi-physical simulation platform based on the principle of dynamic similarity;

[0050] 2. Design the corresponding ground equivalent control circuits for the attitude control circuit, drag-free control circuit, and electrostatic suspension control circuit of the space gravitational wave detection satellite;

[0051] 3. Design the parameters of the ground-space equivalent controller based on the control similarity law.

[0052] The designed ground semi-physical simulation platform and its control loop are used to complete ground simulation of the functions and technical indicators of the drag-free satellite.

[0053] The following is a project description of the design process.

[0054] (1) Design of a ground-based semi-physical simulation platform based on dynamic similarity

[0055] Based on the differences between the models of the sky and the earth, using dimensional analysis tools and according to the π theorem theory, a systematic method is provided to determine the minimum number of parameters that can characterize the complete dynamics of a system, and these parameters are dimensionless to determine the dynamic scaling standard of the system, so that the π groups of the two systems are equal in one-to-one correspondence, and the ground-based semi-physical simulation model and the space gravitational wave satellite model are dynamically equivalent.

[0056] When designing a ground-based, physical-in-the-loop simulation platform, the present invention first analyzes key considerations and, based on these, designs the satellite-equivalent portion and the test mass-equivalent portion. The π theorem is then used to determine the minimum set of dynamic parameters. Based on the designed ground-based, physical-in-the-loop simulation platform and the drag-free satellite, the scaling ratio of these parameters between the two systems is determined. Based on this scaling ratio, the π groups of the two systems are determined, and the equivalence of the simulation platforms is verified. By adjusting mass and dimensions, the ground-based, physical-in-the-loop simulation platform can meet the required residual acceleration and displacement requirements.

[0057] When designing a ground-based semi-physical simulation platform, the present invention takes into account the important indicators of simulated motion freedom. Space satellites include 6 degrees of freedom for the satellite body and 12 degrees of freedom for the dual test mass. The ground-based simulation platform of the present invention uses a five-degree-of-freedom motion platform to simulate the 5 degrees of freedom of the satellite body, and a secondary suspended test mass to simulate the 4-degree-of-freedom motion of the dual test mass in space. The five-degree-of-freedom motion platform includes two horizontal movements and three rotations. The four-degree-of-freedom motion of the dual test mass includes the translation of the dual test mass along the sensitive axis and the rotation around the suspension wire. The sensitive axis is perpendicular to the direction of gravity, and there is no movement along the direction of gravity. Therefore, with the five-degree-of-freedom motion platform, a better semi-physical simulation equivalence can be achieved. Therefore, the present invention eliminates the less necessary equivalent design and ensures equivalence when the structural complexity allows. It can be confirmed through theoretical verification of the π theorem that the present invention's choice of simulated motion degrees of freedom can meet the similarity requirements required for verification.

[0058] Figure 2 In the figure, on the left is a schematic diagram of a space-based gravitational wave detection satellite. The hexagon in the figure represents the satellite, the solid squares outside the hexagon are microthrusters, and TM1 and TM2 are two test masses. The test masses are electrostatically suspended and do not contact the satellite. Each test mass has three axes: one sensitive axis and the other two non-sensitive axes. The two non-sensitive axes are controlled via WeChat to ensure a fixed positional relationship between the non-sensitive axes and the satellite, as well as to maintain a fixed relative position and angle between the two test masses.

[0059] Figure 2 The right side of the figure shows the ground-based semi-physical simulation platform designed by the present invention, namely the ground-based semi-physical simulation platform, which has a five-degree-of-freedom motion platform at the bottom and a two-stage suspended wire pendulum structure at the top. The five-degree-of-freedom motion platform simulates the five degrees of freedom of the drag-free satellite, which are two horizontal translations and three rotations, excluding the degree of freedom in the gravity direction. Figure 3 As shown. The two-stage suspension pendulum structure is connected to the test mass to simulate the zero-gravity suspension state of the test mass in the untowed satellite, and the dual test mass can move with 4 degrees of freedom. The 4 degrees of freedom here include two translations along the sensitive axis and two rotations around the suspension wire, excluding the degree of freedom in the gravity direction, as shown in Figure 2. Figure 4 shown.

[0060] See also Figure 4 The secondary suspended pendulum structure includes two secondary suspended pendulums; each secondary suspended pendulum includes a primary suspension wire, a balance arm is suspended under the primary suspension wire, one end of the balance arm is connected to the balance mass block, and the other end is connected to the secondary suspension wire, and an inspection mass is suspended under the secondary suspension wire.

[0061] The five-degree-of-freedom (5DOF) dynamics of a ground-based five-degree-of-freedom (5DOF) motion platform are similar to those of a space satellite platform. Based on the π theorem, the minimum number of parameters required to characterize the complete dynamics of a drag-free satellite is determined, including mass, size, time, force, and displacement. Three of these parameters, mass, size, and time, were scaled to determine the similarity ratio between the ground-based five-degree-of-freedom (5DOF) motion platform and the space-based gravitational wave detection satellite model. The mass scaling factor is the ratio of the satellite platform's mass to the five-degree-of-freedom (5DOF) motion platform's mass; the size scaling factor is the ratio of the satellite platform's size to the five-degree-of-freedom (5DOF) motion platform's size; and the time scaling factor is not scaled and is set to 1.

[0062] The dynamics of the dual proof mass of the ground-based, two-wire suspended pendulum structure are similar to those of the space-based, two-proof mass. Similarly, the mass, size, and time factors are scaled to determine the ratio of the ground-based, two-wire suspended pendulum to the space-based proof mass model. The mass scaling factor is the ratio of the space-based proof mass to the mass of the two-wire suspended pendulum; the size scaling factor is the ratio of the space-based proof mass to the size of the two-wire suspended pendulum; and the time scaling factor is not scaled and is taken as 1.

[0063] The equivalence between the ground-based semi-physical simulation platform and the space gravitational wave detection satellite model is determined based on the scaling factor. Verification shows that the equivalence of the ground-based semi-physical simulation platform designed by the present invention meets the requirements.

[0064] Furthermore, by adjusting the mass and size and combining the actual ground environment, including ground noise, sensor noise, actuator noise, and various external disturbances, the ground semi-physical simulation platform can meet the required residual acceleration and displacement index requirements.

[0065] (2) Controller equivalence

[0066] This step is a one-to-one correspondence between the ground semi-physical simulation platform control loop and the space gravitational wave detection control loop in the drag-free satellite, including: the ground motion platform attitude control loop is equivalent to the space satellite attitude control loop, the ground drag-free control loop is equivalent to the space drag-free control loop, and the ground electrostatic control loop is equivalent to the space electrostatic suspension control loop.

[0067] Figure 5 In the figure, the left side is the control loop of the space gravitational wave detection satellite, and the right side is the control loop of the ground semi-physical simulation platform.x1 and r x2 They are the displacements in the directions of the sensitive axes of the test mass, and the X-axis and Y-axis refer to the two translational degrees of freedom of the five-degree-of-freedom motion platform.

[0068] The space satellite control method is as follows: the direction of the insensitive axis of the test mass is controlled by an electrostatic suspension control loop. When the displacement of the sensitive axis of the test mass changes, the directions of the two sensitive axes of the test mass are decoupled to the two horizontal degrees of freedom of the satellite platform. The controller controls the relative position change between the satellite platform and the test mass, and the microthruster drives the satellite platform to track the movement of the test mass.

[0069] The design and control method of the ground control loop are as follows:

[0070] The ground-based drag-free control loop includes a sensitive-axis direction decoupling module and a drag-free controller. The sensitive-axis direction decoupling module decouples the displacement changes in both the positive and negative directions of the test mass's sensitive axis, as detected by the displacement sensor, to the X- and Y-axes of the motion stage. This module then subtracts these displacements from the actual X- and Y-axis displacements of the 5-DOF motion stage to determine the relative position change between the 5-DOF motion stage and the test mass, which it then outputs to the drag-free controller. The drag-free controller, comprised of X- and Y-axis controllers, generates control variables based on the input position changes and outputs them to the 5-DOF motion stage to control the relative position between the 5-DOF motion stage and the test mass.

[0071] The attitude control loop of the ground motion platform does not perform equivalent design of anti-interference controller, and only drives the five-degree-of-freedom motion platform to track and test the movement of the mass-sensitive axis through the motion platform actuator.

[0072] The ground-based electrostatic control circuit simulates the displacement detection of a test mass in a drag-free satellite and electrostatically controls the test mass's levitation posture using the static plates of the electrode cage. The control direction is the non-gravity direction of the test mass's two insensitive axes. This ground-based electrostatic control circuit includes a static plate, a displacement sensor, and a static plate controller. The static plates are a pair fixed to a five-degree-of-freedom motion platform; the displacement sensor detects the displacement of the test mass's sensitive and insensitive axes. A pair of static plates and displacement sensors are fixed to the five-degree-of-freedom motion platform. The static plate controller uses the static plates to maintain the relative position of the test mass's insensitive axis with respect to the five-degree-of-freedom motion platform, based on the five-degree-of-freedom motion platform's actual X- and Y-axis displacements and the test mass's displacement detection results.

[0073] It can be seen that the control method of the ground-based semi-physical simulation platform is consistent with the control method used in space gravitational wave detection, and the controllers are equivalent.

[0074] (3) Controller similarity design

[0075] According to the design of the aforementioned ground-based semi-physical simulation platform, the scaling factors between the ground-based semi-physical simulation platform and the space satellite can be determined based on the dynamic similarity, including mass, size, and time. According to the controller parameters of the drag-free control loop in the space satellite, combined with the control similarity, the parameters of the corresponding controller in the ground-based semi-physical simulation platform can be converted, such as Figure 6 shown.

[0076] Taking the PID controller as an example, the PID controller parameters are similarly designed as follows:

[0077]

[0078] in, are the PID parameters of the controller in the ground drag-free control loop, is the PID parameter of the controller in the spatial drag-free controller loop; m S is the mass of the untowed satellite, m G is the mass of the ground five-degree-of-freedom motion platform.

[0079] In summary, the present invention first designs a quasi-zero-stiffness five-degree-of-freedom motion platform based on the principle of dynamic similarity to simulate the partial degrees-of-freedom motion of a drag-free satellite. It then uses a two-stage suspended pendulum test mass to simulate the test mass in a drag-free satellite. Based on the designed semi-physical simulation platform, this patent proposes a ground-based equivalent verification method for a drag-free controller. Based on the drag-free controller used in space gravitational wave detection, a ground-based semi-physical simulation experimental platform controller is designed to verify the effectiveness of the controller designed for space gravitational wave detection. Specifically, the satellite attitude control loop controls the satellite's motion in the motion equivalent space of the five-degree-of-freedom motion platform; the electrostatic levitation control loop controls the electrostatic levitation of the electrode cage in the equivalent space of the static electrode plates of the electrode cage; and the drag-free control loop controls the satellite's tracking of the test mass's sensitive axis in the equivalent space of the motion platform's tracking sensitive axis. Simultaneously, the ground-to-space equivalence of the controller is verified based on the control similarity law. This invention improves the accuracy of ground-based equivalent simulations.

[0080] The above specific embodiments merely illustrate the design principles of the present invention. The shapes and names of the components described herein may vary and are not limiting. Therefore, those skilled in the art may modify or substitute equivalents for the technical solutions described in the above embodiments. Such modifications and substitutions, without departing from the inventive spirit and technical solutions of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A drag-free control ground semi-physical simulation equivalent verification method, characterized in that: include: Step 1: Design a ground-based physical-in-the-loop simulation platform, including: using a five-degree-of-freedom motion platform to simulate the five degrees of freedom of the drag-free satellite, including two horizontal degrees of freedom and three rotational degrees of freedom; using a two-stage suspension wire suspension pendulum structure to attach the test mass to simulate the zero-gravity suspension state of the test mass in the drag-free satellite, and the test mass can move in four degrees of freedom, including two translations along the sensitive axis and two rotations about the suspension wire; Step 2: Design a one-to-one correspondence between the ground-based semi-physical simulation platform control loop and the space gravitational wave detection control loop in the drag-free satellite, including: the ground motion platform attitude control loop is equivalent to the space satellite attitude control loop, the ground drag-free control loop is equivalent to the space drag-free control loop, and the ground electrostatic control loop is equivalent to the space electrostatic suspension control loop. The ground electrostatic control loop uses a pair of static electrode plates fixed on the five-degree-of-freedom motion platform to simulate the electrostatic control of the suspension attitude of the proof mass by the static electrode plates of the electrode cage in the drag-free satellite, and the control direction is the non-gravity direction of the two non-sensitive axes of the proof mass. The displacement sensor in the ground electrostatic control loop is used to simulate the displacement detection of the proof mass in the drag-free satellite. Step 3: Based on the π-theorem theory, determine the minimum number of parameters that characterize the complete dynamics of the drag-free satellite, convert the parameters into dimensionless parameters, and determine the scaling ratio of the dimensionless parameters between the ground-based semi-physical simulation platform and the drag-free satellite; Step 4: Determine controller parameters of the ground no-drag control loop: Utilize the scaling ratio to convert the controller parameters of the spatial no-drag control loop into controller parameters of the ground no-drag control loop; Step 5: Use the ground-based semi-physical simulation platform and its control loop to complete the ground simulation of the drag-free satellite.

2. The method according to claim 1, wherein The secondary suspended wire pendulum structure includes two secondary suspended wire pendulums; each secondary suspended wire pendulum includes a primary suspension wire, a balance arm is suspended under the primary suspension wire, one end of the balance arm is connected to the balance mass block, and the other end is connected to the secondary suspension wire, and an inspection mass is suspended under the secondary suspension wire.

3. The method according to claim 1, wherein The control loops constructed in step 2 are: In the ground drag-free control loop, the displacement changes of the test mass sensitive axis detected by the displacement sensor in both positive and negative directions are decoupled to the X-axis and Y-axis of the motion platform. After the displacement changes are subtracted from the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform, the control variables are generated by the X-axis controller and the Y-axis controller, and then output to the five-degree-of-freedom motion platform to control the relative position change between the five-degree-of-freedom motion platform and the test mass. The attitude control loop of the ground motion platform does not require controller design. The five-degree-of-freedom motion platform is driven by the motion platform actuator to track the motion of the mass-sensitive axis. In the ground electrostatic control circuit, based on the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion stage and the displacement detection results of the proof mass, the relative position of the non-sensitive axis of the proof mass and the five-degree-of-freedom motion stage is controlled by the electrostatic electrode plate to remain unchanged.

4. The method according to claim 1, wherein In step 3, the minimum number of parameters that characterize the complete dynamics of a drag-free satellite is determined based on the π theorem theory, and the mass and size are selected from them; by adjusting the mass and size of the ground-based semi-physical simulation platform, the ground-based semi-physical simulation platform can meet the required residual acceleration and displacement index requirements.

5. The method according to claim 1, wherein In step 4, the controller in the ground drag-free control loop is a PID controller; wherein, The conversion formula of the PID parameters of the displacement controller is: in, are the PID parameters of the ground drag-free controller, is the PID parameter of the spatial drag-free controller; m S is the total mass of the untowed satellite, m G is the mass of the five-degree-of-freedom motion platform.

6. A drag-free control ground semi-physical simulation equivalent verification system, characterized in that: The system includes: a ground semi-physical simulation platform and a ground semi-physical simulation platform control loop; The ground-based semi-physical simulation platform includes a five-degree-of-freedom motion platform, a two-stage suspended pendulum structure, and a test mass; The five-degree-of-freedom motion platform simulates the five-degree-of-freedom motion of a drag-free satellite, including two horizontal degrees of freedom and three rotational degrees of freedom; The two-stage suspension wire pendulum structure is connected to the test mass, which is used to simulate the zero-gravity suspension state of the test mass in the drag-free satellite, and the test mass can move with four degrees of freedom, including two translations along the sensitive axis and two rotations around the suspension wire; The ground control loop corresponds one-to-one with the space gravitational wave detection control loop in the drag-free satellite, including: the ground motion platform attitude control loop is equivalent to the space satellite attitude control loop, the ground drag-free control loop is equivalent to the space drag-free control loop, and the ground electrostatic control loop is equivalent to the space electrostatic suspension control loop; the ground electrostatic control loop uses a pair of static electrode plates fixed on the five-degree-of-freedom motion platform to simulate the electrostatic control of the suspension attitude of the proof mass by the static electrode plates of the electrode cage in the drag-free satellite, and the control direction is the non-gravity direction of the two non-sensitive axes of the proof mass; the displacement sensor in the ground electrostatic control loop is used to simulate the displacement detection of the proof mass in the drag-free satellite; The control parameters in the ground drag-free control loop are obtained by converting the controller parameters in the drag-free satellite according to the scaling ratio of the dimensionless parameters between the ground semi-physical simulation platform and the drag-free satellite determined by the π theorem theory.

7. The system according to claim 6, wherein: The secondary suspended wire pendulum structure includes two secondary suspended wire pendulums; each secondary suspended wire pendulum includes a primary suspension wire, a balance arm is suspended under the primary suspension wire, one end of the balance arm is connected to the balance mass block, and the other end is connected to the secondary suspension wire, and an inspection mass is suspended under the secondary suspension wire.

8. The system according to claim 6, wherein: The ground drag-free control loop includes a sensitive axis direction decoupling module and a drag-free controller. The sensitive axis direction decoupling module decouples the displacement changes of the test mass sensitive axis in the positive and negative directions detected by the displacement sensor to the X-axis and Y-axis of the motion platform, and subtracts the displacements from the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform to obtain the relative position change between the five-degree-of-freedom motion platform and the test mass, and outputs it to the drag-free controller. The drag-free controller includes an X-axis controller and a Y-axis controller, generates a control variable, and outputs it to the five-degree-of-freedom motion platform. The ground motion platform attitude control loop drives the five-degree-of-freedom motion platform to track and test the movement of the mass-sensitive axis only through the motion platform actuator; The ground electrostatic control circuit includes an electrostatic electrode plate, a displacement sensor and an electrostatic electrode plate controller; the electrostatic electrode plates are a pair and are fixed on a five-degree-of-freedom motion platform; the displacement sensor is used to detect the displacement of the inspection mass; the electrostatic electrode plate controller controls the relative position of the non-sensitive axis of the inspection mass and the five-degree-of-freedom motion platform to remain unchanged through the electrostatic electrode plate based on the actual X-axis and Y-axis displacements of the five-degree-of-freedom motion platform and the displacement detection results of the inspection mass.

9. The system according to claim 8, wherein The displacement controller in the drag-free controller is a PID controller, and the PID parameters are: in, are the PID parameters of the ground drag-free controller, is the PID parameter of the spatial drag-free controller; m S is the mass of the untowed satellite, m G is the mass of the five-degree-of-freedom motion platform.

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