A life prediction method for multi-mode electric thrusters based on time-varying stress

Abstract

A method for predicting the life of a multi-mode electric thruster based on time-varying stress comprises the following steps: obtaining working modes in different detection phases and working times corresponding to each working mode; obtaining the initial degradation rate, drift coefficient and diffusion coefficient of sputtering etching under stress of different working modes through a pre-trained parameter prediction model; calculating the sputtering etching degree of a grid system of an electric thruster under time-varying stress according to the initial degradation rate, drift coefficient and diffusion coefficient of sputtering etching; calculating the change of grid wear under stress according to the sputtering etching degree of the grid system of the electric thruster under time-varying stress; setting a sputtering etching threshold, calculating the time required to reach the etching threshold of an acceleration grid under each working mode according to the change of grid wear, and accumulating the time to obtain the life of the electric thruster; the present invention takes into account the influence of sputtering etching of an electric thruster under different modes on the life, and obtains the life of the electric thruster by accumulating the sputtering etching conditions under each mode.

Description

Technical Field

[0001] The present invention relates to the technical field of electric thrusters, and more particularly to a life prediction method for a multi-mode electric thruster based on time-varying stress. Background Art

[0002] In deep space exploration, the probe often has to fly in deep space for several years to reach its destination. The electric thrusters play the role of thrust adjustment and attitude maintenance during flight. The working time of the electric thrusters reaches tens of thousands or even hundreds of thousands of hours. Therefore, the life of the thrusters is very important to the success of the mission. The power supply of the electric thrusters is mainly converted from solar radiation. As the detection distance becomes farther and farther, the intensity of the obtained solar light changes continuously, and the power supply also changes accordingly. It is necessary to continuously adjust the working mode of the electric thrusters. The degree of damage to the thrusters in different modes is different. In the past, the life prediction did not consider the influence of the working mode. In the test process, only the life under average stress was considered.

[0003] In the past, the life prediction value of a product under constant stress was a constant value. Under time-varying stress conditions, the life of the same product is no longer a constant value, but is related to the sequence and duration of the working modes. Accurate prediction of the life of the electric thruster can save onboard fuel, reduce launch costs, and is crucial to ensuring the success of the exploration mission.

[0004] Therefore, how to provide a multi-mode electric thruster life prediction method based on time-varying stress is an urgent problem that technicians in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a multi-mode electric thruster life modeling method based on time-varying stress to determine whether the electric thruster life can meet the detection mission. At the same time, it can accurately predict the life, reduce the launch cost, and ensure the success of the detection mission.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A multi-mode electric thruster life prediction method based on time-varying stress comprises the following steps:

[0008] Obtain working modes and working hours corresponding to each working mode;

[0009] According to the working mode, the initial degradation rate μ of sputtering etching under stress k of different working modes is obtained through the pre-trained parameter prediction model. k , drift coefficient b k and the diffusion coefficient σ k ;

[0010] According to the initial degradation rate μ of the sputtering etching k , drift coefficient bk and the diffusion coefficient σ k Calculate the sputtering etching degree of the electric thruster grid system under time-varying stress;

[0011] According to the sputtering etching degree of the electric thruster grid system under the time-varying stress, the grid wear variation under the stress k is calculated;

[0012] The sputtering etching threshold is set, and according to the change of the gate wear, the time required to reach the etching threshold of the acceleration gate in each working mode is calculated and accumulated to obtain the life of the electric thruster.

[0013] Furthermore, the training step of the parameter prediction model includes:

[0014] S1: Locate 9 grid holes from the acceleration grid;

[0015] S2: setting a test etching threshold, and etching the acceleration gate respectively under different stress levels until the etching data reaches the etching threshold;

[0016] S3: During the etching process, the etching data of the j-th gate hole at the i-th time is measured, wherein i=0, 1, 2..., n; j=1, 2, 3...9;

[0017] S4: Calculate the initial degradation rate μ of sputtering etching under stress level k in different working modes k , drift coefficient b k and the diffusion coefficient σ k ,

[0018]

[0019]

[0020]

[0021] Among them, x i,j is the etching data of gate hole j at the i-th moment, x i,1 is the etching data of gate hole No. 1 at the i-th moment, x i,9 is the etching data of gate hole No. 9 at the i-th moment; t i represents the measurement time at the i-th moment, t n is the final measurement time of the experiment, and t1 is the starting measurement time of the experiment;

[0022] Furthermore, the method for positioning the grid holes includes positioning one grid hole at the center of the acceleration grid, positioning four grid holes in the middle of the acceleration grid, and positioning four grid holes at the edge of the acceleration grid.

[0023] Furthermore, the stress k is set corresponding to different working modes to simulate the stress conditions of each working mode.

[0024] Furthermore, the sputtering etching degree of the electric thruster grid system is calculated by the following formula:

[0025]

[0026] Among them, Th k Indicates the etching process, represents the degree of gate wear change per unit time, and B(t) represents the Brownian motion parameter.

[0027] Furthermore, the gate wear variation under the stress k is calculated by the following formula:

[0028] Furthermore, the sputtering etching threshold is set, and according to the change of the gate wear, the time required to reach the etching threshold of the acceleration gate in each working mode is calculated, and the accumulated time is added to obtain the life of the electric thruster, which includes:

[0029] Set the threshold Th, and calculate the time required to reach the etching threshold of the acceleration gate in each working mode by the following formula:

[0030] Among them, t k represents the working time under stress k corresponding to the working mode, and n represents the number of working modes;

[0031] The time required to reach the etching threshold of the acceleration gate in each working mode is accumulated to obtain the life of the electric thruster L. in, It represents the working life under the stress k corresponding to the working mode.

[0032] Beneficial effects of the present invention:

[0033] Through the above technical solutions, it can be known that compared with the prior art, the present invention discloses a multi-mode electric thruster life prediction method based on time-varying stress, considering the influence of electric thruster sputtering etching on life under different working modes, establishing an electric thruster life model based on time-varying stress, constructing life models in each mode and estimating parameters, accumulating the sputtering etching conditions in each mode, and being able to more realistically characterize the on-orbit working conditions of the electric thruster, and being more in line with the actual situation in calculating the life. Accurately predicting the life of the electric thruster can carry reasonable fuel, reduce the carrying weight, and reduce the cost of the entire mission. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 The accompanying drawing is a schematic diagram of a multi-mode electric thruster life prediction method based on time-varying stress provided by the present invention;

[0036] Figure 2 The accompanying drawing is a schematic diagram of different stress levels and corresponding sputtering etching conditions in the present invention;

[0037] Figure 3 The accompanying drawing is a schematic diagram of the distribution of the holes of the acceleration grid in the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] like Figure 1 The embodiment of the present invention discloses a method for predicting the life of a multi-mode electric thruster based on time-varying stress, comprising the following steps:

[0040] Obtain the working mode and the working time corresponding to each working mode; analyze the space exploration phase according to the space exploration mission, obtain the corresponding working time of the electric thruster in different phases, and determine the working time of the electric thruster in different working modes;

[0041] Calculate the model parameters under different working modes, and based on the working mode, obtain the initial degradation rate μ of sputtering etching under stress k of different working modes through the pre-trained parameter prediction model. k , drift coefficient b k and the diffusion coefficient σ k ;

[0042] The change of sputtering etching degree of the electric thruster grid system under time-varying stress is analyzed. According to the initial degradation rate μ k , drift coefficient b k and the diffusion coefficient σ kCalculating the sputtering etching degree of the electric thruster grid system under time-varying stress; calculating the change of grid wear under stress k according to the sputtering etching degree of the electric thruster grid system under the time-varying stress;

[0043] like Figure 2 The grid system generates rated thrust by accelerating the xenon in the discharge chamber. In this process, electron backflow and other conditions will occur, resulting in the etching of the slots, which will increase the aperture of the accelerating grid. The sputtering etching rate of the accelerating grid aperture under different working modes is analyzed. The sputtering etching rate can be obtained through experiments. In ground tests, stress conditions similar to those in space are loaded. Generally speaking, the larger the working mode and the greater the power, the greater the sputtering etching rate of the electric thruster, which is expressed as S1<S2<…<S i <…<S n , that is, stress k includes S1, S2, S i , S n , representing the stresses of the 1st, 2nd, i, and nth working modes respectively.

[0044] The life of the electric thruster is calculated, a sputtering etching threshold is set, and the time required to reach the etching threshold of the acceleration gate in each working mode is calculated according to the change in the gate wear, and the time is accumulated to obtain the life of the electric thruster.

[0045] In another embodiment, the step of training the parameter prediction model includes:

[0046] S1: Locate 9 holes in the acceleration grid; the holes are used to accelerate ions. Due to the sputtering of ions, the holes will gradually become larger and eventually cause the acceleration grid to fall off, which can represent the life of the ion thruster.

[0047] S2: setting a test etching threshold, etching the acceleration gates respectively under different stresses k until the etching data reaches the etching threshold; multiple groups of acceleration gates may be set, and different stresses k are assigned to each group of acceleration gates;

[0048] S3: During the etching process, the etching data of the j-th gate hole at the i-th time is measured, wherein i=0, 1, 2..., n; j=1, 2, 3...9; the sputtering etching condition is measured once every certain period of time, and the test is terminated when the test time reaches a specified value or the sputtering etching reaches a specified threshold value;

[0049] S4: Calculate the initial degradation rate μ of sputtering etching under stress level k in different working modes k , drift coefficient b k and the diffusion coefficient σ k ,

[0050]

[0051]

[0052]

[0053] Among them, x i,j is the etching data of gate hole j at the i-th moment, x i,1 is the etching data of gate hole No. 1 at the i-th moment, x i,9 is the etching data of gate hole No. 9 at the i-th moment; t i represents the measurement time at the i-th moment, t n is the final measurement time of the experiment, and t1 is the starting measurement time of the experiment.

[0054] like Figure 3 In another embodiment, the method for positioning the gate holes includes positioning one gate hole at the center of the acceleration gate, positioning four gate holes in the middle of the acceleration gate, and positioning four gate holes at the edge of the acceleration gate.

[0055] In another embodiment, the stress k is set correspondingly according to different working modes.

[0056] In another embodiment, the sputtering etching degree of the electric thruster grid system is calculated by the following formula:

[0057]

[0058] Among them, Th k represents the etching degree under stress k, It represents the degree of gate wear change per unit time, and B(t) represents the Brownian motion parameter.

[0059] In another embodiment, the gate wear variation under the stress k is calculated by the following formula:

[0060] In another embodiment, the setting of the sputtering etching threshold, according to the change of the gate wear, calculates the time required to reach the etching threshold of the acceleration gate in each working mode, and accumulates the time to obtain the life of the electric thruster, which includes:

[0061] Set the threshold Th, and calculate the time required to reach the etching threshold of the acceleration gate in each working mode by the following formula:

[0062] Among them, t k represents the working time under the stress k corresponding to the working mode, that is, the working time of the electric thruster under different working modes initially determined according to the space exploration mission, and n represents the number of working modes;

[0063] The time required to reach the etching threshold of the acceleration gate in each working mode is accumulated to obtain the life of the electric thruster L. in, It represents the working life under the stress k corresponding to the working mode.

[0064] The present invention considers the influence of sputtering etching on the life of electric thrusters in different modes, establishes an electric thruster life model based on time-varying stress, constructs life models in various modes and estimates parameters, and accumulates sputtering etching conditions in various modes to more realistically characterize the on-orbit working conditions of electric thrusters, and is more in line with actual conditions in calculating life. Accurately predicting the life of electric thrusters can carry reasonable fuel, reduce the carrying weight, and reduce the cost of the entire mission.

[0065] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0066] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-mode electric thruster life prediction method based on time-varying stress, characterized in that: The following steps are included: Determine the working modes and the working hours corresponding to each working mode; According to the working mode, the initial degradation rate μ of sputtering etching under stress k of different working modes is obtained through the pre-built parameter prediction model. k , drift coefficient b k and the diffusion coefficient σ k ; According to the initial degradation rate μ of the sputtering etching k , drift coefficient b k and the diffusion coefficient σ k Calculate the sputtering etching degree of the electric thruster grid system under time-varying stress; According to the sputtering etching degree of the electric thruster grid system under the time-varying stress, the grid wear variation under the stress k is calculated; The sputtering etching threshold is set, and according to the change of the gate wear, the time required to reach the etching threshold of the acceleration gate in each working mode is calculated and accumulated to obtain the life of the electric thruster.

2. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 1 is characterized in that: The steps of constructing the parameter prediction model include: Locate 9 grid holes from the acceleration grid; Setting a test etching threshold, and etching the acceleration gate respectively under different stresses k until the etching data reaches the test etching threshold; During the etching process, the etching data of the j-th gate hole at the i-th time is measured, wherein i=0, 1, 2..., n; j=1, 2, 3...9; Calculate the initial degradation rate μ of sputtering etching under stress k in different working modes k , drift coefficient b k and the diffusion coefficient σ k , the expression is: Among them, x i,j is the etching data of gate hole j at the i-th moment, x i,1 is the etching data of gate hole No. 1 at the i-th moment, x i,9 is the etching data of gate hole No. 9 at the i-th moment; t i represents the measurement time at the i-th moment, t n is the final measurement time of the experiment, and t1 is the starting measurement time of the experiment.

3. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 2 is characterized in that: The method for positioning the grid holes includes positioning one grid hole at the center of the acceleration grid, positioning four grid holes in the middle of the acceleration grid, and positioning four grid holes at the edge of the acceleration grid.

4. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 2 is characterized in that: The stress k is set correspondingly according to different working modes.

5. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 2 is characterized in that: The sputtering etching degree of the electric thruster grid system is calculated by the following formula: Among them, Th k Indicates the degree of etching, represents the degree of gate wear change per unit time, B(t) represents the Brownian motion parameter; t represents the test time under stress k.

6. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 5 is characterized in that: The gate wear variation under the stress k is calculated by the following formula:

7. The method for predicting the life of a multi-mode electric thruster based on time-varying stress according to claim 1 is characterized in that: The setting of the sputtering etching threshold, according to the change of the gate wear, calculating the time required to reach the etching threshold of the acceleration gate in each working mode, and accumulating the time to obtain the life of the electric thruster includes: Set the threshold Th, and calculate the time required to reach the etching threshold of the acceleration gate in each working mode by the following formula: Among them, t k represents the working time under stress k corresponding to the working mode, and n represents the number of working modes; The time required to reach the etching threshold of the acceleration gate in each working mode is accumulated to obtain the life of the electric thruster L. in, It represents the working life under the stress k corresponding to the working mode.

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