Method for autonomously identifying additional rigidity of cable between two stages of platforms based on flexible connection

Abstract

The invention relates to a flexible connection-based method for autonomously identifying additional rigidity of a cable between two stages of platforms, which relates to the field of spacecraft attitude control, and comprises the following steps of: in a cable-free connection state, sequentially outputting sine excitation by voice coil motors in all actuators, and measuring by an eddy current sensor to obtain motion displacement; calculating the stiffness of the actuators based on the two groups of data, and then calculating the equivalent stiffness of each actuator in the state of cable connection according to the previous step; the method has the advantages that the additional rigidity of the cable in the on-orbit state can be obtained, the influence of the cable is reduced by adopting control measures, the control capacity of a three-super platform is guaranteed, the stability of the three-super platform is improved, and the reliability of the three-super platform is improved. And a technical basis is provided for high-precision pointing, high-stability control and rapid and stable control of the load of a new-generation spacecraft.

Description

Technical Field

[0001] This invention relates to the field of spacecraft attitude technology, and in particular to an autonomous identification method for the additional stiffness of cables between two-stage platforms based on flexible connections. Background Technology

[0002] Currently, large high-resolution optical remote sensing satellites have extremely high control performance requirements. These satellites are large inertial satellites with multiple large flexible attachments, low and dense modal frequencies, and severe coupling between rigid, flexible and fluid components. The contradiction between the agile maneuvering "fast start and fast stop" and the ultra-high resolution imaging "fast and stable, ultra-precise and ultra-stable" control is prominent. Traditional control methods that rely solely on the satellite platform level are insufficient to meet the extremely high performance requirements. Therefore, a three-super platform with rapid pointing adjustment, disturbance compensation and vibration isolation was designed between the satellite platform and the payload. Various on-board interferences are eliminated centrally at the payload mounting point to improve the "fast, stable and accurate" performance indicators.

[0003] Because the satellite platform and the payload are connected via a flexible triple-platform, and the connection stiffness of the triple-platform is generally low with a frequency of about 1 to 2 Hz, the cables connecting the satellite platform and the payload across the triple-platform will increase the stiffness of the triple-platform actuator itself as additional stiffness, thus affecting the triple-platform control performance indicators.

[0004] Therefore, to address the above shortcomings, a method for autonomously identifying the additional stiffness of cables between two-level platforms based on flexible connections is needed. Summary of the Invention

[0005] (a) Technical problems to be solved The technical problem to be solved by this invention is to address the issue of the inability to estimate external interference such as the additional stiffness of cables.

[0006] (II) Technical Solution To address the aforementioned technical problems, this invention provides a method for autonomously identifying the additional stiffness of cables between two-stage platforms based on flexible connections. This method is based on a structure where a load and a satellite platform are connected by several triple-platform actuators. Each triple-platform actuator includes a flexible spring-damped passive element, a voice coil motor active element, and an eddy current sensor. The method includes the following steps: Ⅰ. In the absence of cable connection, the voice coil motors in each actuator sequentially output sinusoidal excitation. And the motion displacement is obtained by measuring the eddy current sensor. ; II. Based on the sinusoidal excitation value output by the voice coil motor Motion displacement values ​​obtained by eddy current sensor measurement Calculate the actuator stiffness measurement at the current time. Specifically: in: To be based on sampling period Increasing time variable; ~ ; Then calculate the deviation between the measured value and the estimated value. : Corrected estimate : in, These are the filter coefficients; The result As the actuator stiffness identified at the current time; III. By continuously iterating based on the above formula, the actuator stiffness identification value can be obtained. .

[0007] As a further explanation of the present invention, preferably, the sinusoidal excitation value output by the voice coil motor... Represented as: in, The amplitude of the sinusoidal excitation; The frequency of the sinusoidal excitation.

[0008] As a further explanation of the present invention, preferably, the filtering coefficients or .

[0009] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention, without adding any additional devices, can obtain the stiffness identification results of each actuator by measuring the output of the voice coil motor of the three-actuator and the eddy current, and then use it for controller design. This solves the problem that external disturbances such as additional stiffness cannot be estimated, improves the overall performance of the three-actuator control system, and thus achieves ultra-high precision, ultra-high stability and ultra-high agility control performance of the load. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the flexible connection two-level platform system with cables of the present invention; Figure 2 This is a flowchart of the present invention; Figure 3 This is the result of the output force of the voice coil motor of each actuator in the wireless state of the present invention; Figure 4 This is the result of stiffness identification of each actuator in the wireless state of the present invention; Figure 5 This invention relates to the output force of the voice coil motors of each actuator in the wired state. Figure 6 This is the equivalent stiffness identification result of each actuator in the wired state of the present invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] An autonomous identification method for the additional stiffness of cables between two-level platforms based on flexible connections, such as... Figure 1 As shown, the structure is based on a triple-platform actuator, a payload, and a satellite platform. The payload is an optical system used for high-quality imaging of the target. The satellite platform mainly supports the triple-platform and the payload. The triple-platform is installed between the payload and the satellite platform, with its upper plane connected to the payload and its lower plane connected to the satellite platform. The triple-platform consists of six or eight actuators, each containing three parts installed in parallel: a flexible spring-damped passive element, a voice coil motor active element, and an eddy current sensor. The voice coil motor drives the axial movement of the actuator, and the eddy current sensor measures the axial displacement of the actuator. Cables connecting the satellite platform and the payload are connected in parallel with the triple-platform actuators. Each triple-platform actuator includes a flexible spring-damped passive element, a voice coil motor active element, and an eddy current sensor.

[0013] The method specifically includes the following steps: I. In a wireless state, apply sinusoidal excitation with specific parameters to each actuator sequentially. Simultaneously, the motion displacement is measured using an eddy current sensor. Taking a three-dimensional platform consisting of eight actuators as an example, sinusoidal excitation... Represented as: in, This refers to the number of actuators, which is 8 in this case. The amplitude of the sinusoidal excitation is preferably 20N; The frequency of the sinusoidal excitation is preferably 0.04 Hz; To be based on sampling period Increasing time variable, optimal sampling period The duration is 10ms and the time is 50s. II. Based on the sinusoidal excitation value output by the voice coil motor Motion displacement values ​​obtained by eddy current sensor measurement Calculate the actuator stiffness measurement at the current time. Specifically: in ~ ; Then calculate the deviation between the measured value and the estimated value. : Corrected estimate : in, For the filter coefficients, the preferred values ​​are... or ; The result The actuator stiffness is determined at the current time.

[0014] III. By continuously iterating based on the above formula, the actuator stiffness identification value can be obtained. .

[0015] IV. Simulation verification of the method: Substitute the preferred specific parameters from step I into the sinusoidal excitation. The calculation formula calculates the output force obtained by the voice coil motors of the eight actuators, i.e., the sinusoidal excitation. , to obtain Figure 3 The output force results in the wireless state are shown, and as follows Figure 5 The output force result is shown in the wired state. The subsequent output is as follows: Figure 4 The identification results of the stiffness of the eight actuators in the wireless state are shown, with a value of approximately 40,000 N / m; and as shown... Figure 6 The identification results of the equivalent stiffness of the eight actuators in the wired state are shown, with a value of approximately 47500 N / m. Figure 4 and Figure 6 The obtained actuator stiffness results are summarized in Table 1. The additional stiffness of a single actuator caused by the cable can be calculated as follows: Table 1. Statistical Table of Cable Additional Stiffness Identification Results Table 1 shows that the values ​​of the actuator's intrinsic stiffness and equivalent stiffness are relatively concentrated with minimal fluctuations, indicating that the actuators themselves are of good quality and the data obtained for verification is reliable. Although the calculated additional stiffness varies considerably between actuators, field verification indicates that this is due to differences in cable length and deformation. Table 2 is obtained after adjusting the cables for "uniformity". Table 2 Statistical Table of Additional Stiffness Identification Results After Cable Adjustment Comparing the results of the additional stiffness changes in Tables 1 and 2, it is shown that the additional stiffness calculated by this method can indeed represent the influence of the cable on the actuator, thus demonstrating the accuracy of this method.

[0016] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for autonomously identifying the additional stiffness of cables between two-stage platforms based on flexible connections, based on a structure connecting the load and the satellite platform by several triple-platform actuators, each triple-platform actuator including a flexible spring-damped passive element, a voice coil motor active element, and an eddy current sensor, characterized in that: Includes the following steps: Ⅰ. In the absence of cable connection, the voice coil motors in each actuator sequentially output sinusoidal excitation. And the motion displacement is obtained by measuring the eddy current sensor. ; II. Based on the sinusoidal excitation value output by the voice coil motor Motion displacement values ​​obtained by eddy current sensor measurement Calculate the actuator stiffness measurement at the current time. Specifically: in: To be based on sampling period Increasing time variable; ～ ； Then calculate the deviation between the measured value and the estimated value. : Corrected estimate : in, These are the filter coefficients; The result As the actuator stiffness identified at the current time; III. By continuously iterating based on the above formula, the actuator stiffness identification value can be obtained. .

2. The method for autonomously identifying the additional stiffness of cables between two-level platforms based on flexible connections according to claim 1, characterized in that: The sinusoidal excitation value output by the voice coil motor Represented as: in, The amplitude of the sinusoidal excitation; The frequency of the sinusoidal excitation.

3. The method for autonomously identifying the additional stiffness of cables between two-level platforms based on flexible connections according to claim 1, characterized in that: Filter coefficients or .

Images