A method of thrust control for a microwave ion propulsion system

Abstract

This invention provides a thrust control method for a microwave ion propulsion system. It presets the thrust range, working propellant flow range, pressure regulation range, and duty cycle regulation range. Applying a PID control method, the PID parameters are determined through ground experiments, and target values ​​for the duty cycle and pressure are set. In actual operation, given the target thrust value, the PID is used to finely adjust the pressure and solenoid valve duty cycle to achieve the corresponding target value, thereby improving thrust accuracy and meeting the high-precision, high-stability thrust requirements of microsatellites. This method has broad application prospects in the field of space propulsion technology.

Description

Technical Field

[0001] This invention relates to a thrust control method for a microwave ion propulsion system, belonging to the field of space propulsion technology. Background Technology

[0002] Microwave ion propulsion systems are mostly used for orbit maintenance and deorbiting of microsatellites. Their thrust output is characterized by small thrust, wide range, and high precision. In order to meet the overall thrust requirements of the satellite, the satellite orbit needs to be precisely planned, and the thrust output of the propulsion system needs to be accurate and stable. Furthermore, the performance of the propulsion system will degrade after long-term operation in orbit, and the operating parameters at the beginning of operation cannot be matched in real time to the propulsion system after the performance degrades.

[0003] Proportional-integral-derivative (PID) control is widely used in engineering. It has a simple structure, is stable and reliable, and is easy to adjust parameters. Therefore, it is applied to microwave ion propulsion systems to control thrust error and ensure the stability of the system in orbit and the accuracy of thrust output. Summary of the Invention

[0004] The purpose of this invention is to provide a reasoning control method for a microwave ion propulsion system that matches the operating characteristics of the microwave ion propulsion system and enables rapid adjustment of thrust output in orbit.

[0005] To achieve the above objectives, the present invention provides a thrust control method for a microwave ion propulsion system, wherein the microwave ion propulsion system includes a thruster, a storage and supply subsystem, a PID controller, a microwave source, and a high-voltage power supply; the thrust control method includes the following steps:

[0006] S1: Based on the design performance indicators of the thruster, determine the final output thrust range of the microwave ion propulsion system and set the working fluid flow rate adjustment range of the thruster under rated operation.

[0007] S2: Based on the mechanical characteristics of the working fluid flow control components of the storage and supply subsystem, set the duty cycle adjustment range of the thruster solenoid valve;

[0008] S3: Set the pressure regulation range controlled by the thruster throttle valve according to the pressure characteristics of the storage and supply subsystem pipeline;

[0009] S4: Construct a PID controller and determine the PID parameters; input the thrust target value and the actual thrust, and use PID control through ground experiments. Adjust the working fluid flow rate within the working fluid flow rate adjustment range set in S1, and perform PID pressure adjustment and PID duty cycle adjustment until the final output thrust of the thruster reaches the thrust target value, and obtain the pressure target value and duty cycle target value; wherein, the thrust target value is within the final output thrust range determined in S1, the pressure target value is within the pressure adjustment range set in S3, and the duty cycle target value is within the duty cycle adjustment range set in S2;

[0010] S5: The PID parameters are embedded into the microcontroller program of the controller. Given the target thrust value within the final output thrust range determined by S1, the microwave ion propulsion system works together to make the final output thrust automatically reach the target thrust value without having to set the pressure target value and duty cycle target value again.

[0011] Preferably, in S1, the required thrust output range of the propulsion system is set to 0.2 to 0.5 mN, and the working fluid flow rate adjustment range of the thruster under rated operation is set to 0.2 to 0.7 sccm.

[0012] Furthermore, the actual thrust in S4 is influenced by the combined effects of the thruster beam voltage and beam current; the beam voltage is generated by the high-voltage power supply of the microwave ion propulsion system, and the beam current is determined by the working fluid flow rate, ionization efficiency, and accelerating electric field between the grids. The actual thrust F satisfies the following thrust formula:

[0013]

[0014] Where α is the beam divergence compensation coefficient; β is the dual-charged ion compensation coefficient; m is the xenon atomic mass; e is the charge constant; V b For beam voltage; I b For beam current.

[0015] Furthermore, under the same actual thrust, the thruster can be matched with different gate voltages and thruster working fluid flow rates according to on-orbit operating requirements.

[0016] Furthermore, in step S4, the PID controller compares the input value c(t) and the target value r(t) to obtain the error value e(t), which satisfies the following equation:

[0017] e(t) = r(t) - c(t);

[0018] Using the error value e(t) as the control input, the adjusted output value u(t) reaches or remains within the target error range, and u(t) satisfies the following equation:

[0019]

[0020] Among them, K P K is the proportional parameter of the PID controller. i K is the integral parameter of the PID controller. d These are the differential parameters of the PID controller.

[0021] Furthermore, the PID pressure regulation in S4 specifically involves: using the difference between the actual thrust and the target thrust value as the control variable, controlling the working fluid flow rate through the throttle to regulate the actual pressure within the pressure regulation range set in S3, and using PID regulation to monitor the actual thrust; when the actual thrust reaches the target thrust value, the current actual pressure becomes the target pressure value, the current duty cycle becomes the target duty cycle value, and S4 is stopped; otherwise, PID duty cycle regulation is performed.

[0022] Furthermore, the PID duty cycle adjustment in S4 specifically involves: using the difference between the actual thrust and the target thrust value as the control variable, adjusting the duty cycle of the solenoid valve within the duty cycle adjustment range set in S2, and adjusting the working fluid flow by switching on and off at a certain frequency, while using PID regulation to monitor the actual thrust; when the actual thrust reaches the target thrust value, the current duty cycle becomes the target duty cycle value, the current actual pressure becomes the target pressure value, and S4 is stopped; otherwise, PID pressure regulation is performed.

[0023] Furthermore, in S4, the larger the duty cycle controlled by the solenoid valve, the larger the target pressure value, and the larger the working fluid flow rate.

[0024] Furthermore, the beam current is deduced from the thrust formula, and the beam current is monitored in real time. The actual thrust corresponds to the actual beam current, and the target thrust value corresponds to the target beam current value. The difference between the actual beam current and the target beam current value is used as a control variable. The working fluid flow is adjusted using a throttle or solenoid valve, while PID regulation is used to monitor the beam current. When the actual beam current reaches the target beam current value, the actual thrust reaches the target thrust value, the current duty cycle is the target duty cycle value, the current actual pressure is the target pressure value, and S4 is stopped. Otherwise, PID pressure regulation or PID duty cycle regulation is performed.

[0025] Furthermore, in S5, the PID controller adjusts the operating parameters of each component by issuing control signals; the storage and supply system provides working fluid to the thruster; the microwave source inputs microwaves into the thruster discharge chamber, which together with the magnetic field in the thruster discharge chamber forms an electron cyclotron resonance region. After the free electrons are accelerated, they ionize the working fluid to generate plasma, in which ions are accelerated and ejected under the action of the accelerating electric field formed by the screen grid and the accelerating grid to form thrust.

[0026] In summary, compared with the prior art, the inference control method for the microwave ion propulsion system provided by the present invention applies the PID control method. After setting the thrust value, it performs fine adjustment of the pressure and solenoid valve duty cycle under given PID parameters, thereby improving thrust accuracy and meeting the high-precision and high-stability thrust requirements of microsatellites. Attached Figure Description

[0027] Figure 1 This is a flowchart of the PID controller in the reasoning control method of the microwave ion propulsion system of the present invention;

[0028] Figure 2 The above is a flowchart of the S4 flow chart of the reasoning control method of the microwave ion propulsion system of the present invention.

[0029] Figure 3 This is flowchart S5 of the reasoning control method for the microwave ion propulsion system of the present invention;

[0030] Figure 4 This is a calculation flowchart of the reasoning control method for the microwave ion propulsion system of the present invention. Detailed Implementation

[0031] The following will be combined with the appendix in the embodiments of the present invention. Figure 1 ~Attached Figure 4 The technical solution, objectives and effects of the reasoning control method of the microwave ion propulsion system of the present invention are described in detail.

[0032] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0033] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0034] This invention provides a reasoning control method for a microwave ion propulsion system, such as... Figures 1-4As shown, the microwave ion propulsion system includes a thruster, a storage and supply subsystem, a PID controller, a microwave source, and a high-voltage power supply. The PID controller adjusts the operating parameters of each component by issuing control signals. The storage and supply subsystem provides working fluid to the thruster. The microwave source inputs microwaves into the thruster's discharge chamber, where they, together with the magnetic field in the discharge chamber, form an electron cyclotron resonance region. After being accelerated, the free electrons ionize the working fluid to generate plasma. Ions in the plasma are accelerated and ejected under the action of the accelerating electric field formed by the screen and the accelerating grid, thus generating thrust.

[0035] The thruster includes: a throttle valve, which regulates the real-time pressure of the storage and supply subsystem pipeline by controlling the working fluid flow rate; and a solenoid valve, which regulates the working fluid flow rate by adjusting its own switching frequency through the duty cycle, thereby changing the system thrust. A larger solenoid valve duty cycle and higher pressure result in a larger working fluid flow rate. When the high-voltage power supply, ionization efficiency, and accelerating electric field between the grids are in a stable state, the change in working fluid flow rate is positively correlated with the beam current.

[0036] The inference control method of the microwave ion propulsion system includes the following steps:

[0037] S1: Based on the design performance indicators of the thruster, determine the final output thrust range of the microwave ion propulsion system and set the working fluid flow rate adjustment range of the thruster under rated operation.

[0038] S2: Based on the mechanical characteristics of the working fluid flow control components of the storage and supply subsystem, set the duty cycle adjustment range of the thruster solenoid valve;

[0039] S3: Set the pressure regulation range controlled by the thruster throttle valve according to the pressure characteristics of the storage and supply subsystem pipeline;

[0040] S4: Construct a PID controller and determine the PID parameters; input the thrust target value and the actual thrust, and use PID control through ground experiments. Adjust the working fluid flow rate within the working fluid flow rate adjustment range set in S1, and perform PID pressure adjustment and PID duty cycle adjustment until the final output thrust of the thruster reaches the thrust target value, and obtain the pressure target value and duty cycle target value; wherein, the thrust target value is within the final output thrust range determined in S1, the pressure target value is within the pressure adjustment range set in S3, and the duty cycle target value is within the duty cycle adjustment range set in S2;

[0041] S5: The PID parameters are embedded into the microcontroller program of the controller. Given the target thrust value within the final output thrust range determined by S1, the microwave ion propulsion system works together to make the final output thrust automatically reach the target thrust value without having to set the pressure target value and duty cycle target value again.

[0042] Specifically, in this preferred embodiment, S1 sets the required thrust output range of the propulsion system to be 0.2 to 0.5 mN, and sets the working fluid flow rate adjustment range of the thruster to be 0.2 to 0.7 sccm.

[0043] Furthermore, the actual thrust in S4 is influenced by the combined effects of the thruster beam voltage and beam current; the beam voltage is generated by the high-voltage power supply of the microwave ion propulsion system, and the beam current is determined by the working fluid flow rate, ionization efficiency, and accelerating electric field between the grids. The actual thrust F satisfies the following thrust formula:

[0044]

[0045] Where α is the beam divergence compensation coefficient; β is the dual-charged ion compensation coefficient; m is the atomic mass of xenon in kg; and e is the charge constant, which is 1.6 × 10⁻⁶. -19 C;V b I is the beam voltage, measured in V. b The beam current is expressed in amperes (A). Under steady-state conditions, the ionization efficiency and the accelerating electric field between the grids remain constant. By adjusting the working fluid flow rate, the beam current can be changed, thereby altering the actual thrust.

[0046] Furthermore, under the same actual thrust, the thruster can be matched with different gate voltages and thruster propellant flow rates according to on-orbit operating requirements; representative operating conditions are as follows:

[0047] Rated operating conditions: 1250V for the shield grid, -200V for the acceleration grid, and 0.5 sccm for the working fluid flow rate;

[0048] High thrust operating conditions: 1250V for the grid, -200V for the acceleration grid, and 0.6 sccm for the working fluid flow rate;

[0049] High specific impulse operating conditions: 1500V for the grid, -200V for the acceleration grid, and 0.45 sccm for the working fluid.

[0050] Specifically, the PID controller in S4, such as Figure 1 As shown, a PID controller consists of a proportional (P) unit, an integral (I) unit, and a derivative (D) unit, corresponding to the current error, past cumulative error, and future error, respectively. The parameters K of these three units are adjusted... P (Proportional parameter), K i (Integral parameter) and K d(Differential parameters) are used to adjust the PID controller to meet design requirements. The controller's response can be represented by how quickly it reacts to errors, the degree of overshoot, and the extent of system oscillation. The PID controller compares the input value c(t) with the target value r(t) to obtain the error value e(t), which satisfies the following equation:

[0051] e(t) = r(t) - c(t);

[0052] Then, this error value e(t) is used as the control input to make the adjusted output value u(t) reach or remain within the target error range, and u(t) satisfies the following equation:

[0053]

[0054] PID controllers can adjust the input value based on historical data and the occurrence rate of differences, making the system more accurate and stable.

[0055] Furthermore, S4 is as follows Figure 2 As shown, specifically:

[0056] It is known that under stable conditions such as high voltage power supply, ionization efficiency, and accelerating electric field between the grids, the working fluid flow rate is positively correlated with the beam current, and the beam current is positively correlated with the actual thrust. Therefore, the working fluid flow rate is positively correlated with the actual thrust. In addition, the solenoid valve duty cycle is positively correlated with the working fluid flow rate, and the pressure is positively correlated with the working fluid flow rate.

[0057] PID pressure regulation: The difference between the actual thrust and the target thrust value is used as the control variable. The throttle controls the working fluid flow rate and regulates the actual pressure within the pressure regulation range set in S3. PID regulation is used to monitor the actual thrust. When the actual thrust reaches the target thrust value, the current actual pressure becomes the target pressure value, the current duty cycle becomes the target duty cycle value, and S4 is stopped; otherwise, PID duty cycle regulation is performed.

[0058] PID duty cycle regulation: The difference between the actual thrust and the target thrust value is used as the control variable. The solenoid valve adjusts the duty cycle within the duty cycle regulation range set in S2, and switches on and off at a certain frequency to regulate the working fluid flow. PID regulation is used to monitor the actual thrust. When the actual thrust reaches the target thrust value, the current duty cycle is the target duty cycle value, the current actual pressure is the target pressure value, and S4 is stopped; otherwise, PID pressure regulation is performed.

[0059] Furthermore, during the PID pressure regulation and PID duty cycle regulation, given the difficulty in monitoring force and working fluid flow rate, the beam current is deduced from the thrust formula, and the beam current is monitored in real time; the actual thrust corresponds to the actual beam current, and the thrust target value corresponds to the beam current target value; the difference between the actual beam current and the beam current target value is used as the control variable, and the working fluid flow rate is adjusted using a throttle or solenoid valve, while PID regulation is used to monitor the beam current; when the actual beam current reaches the beam current target value, the actual thrust reaches the thrust target value, the current duty cycle is the duty cycle target value, the current actual pressure is the pressure target value, and S4 is stopped; otherwise, PID pressure regulation or PID duty cycle regulation is performed.

[0060] Specifically, S5 is as follows Figure 3 and Figure 4 As shown, t represents time, and (t) represents a time-varying process. Represents a computation node, where computational operations are performed;

[0061] R(t) is the PID target value, representing the thrust target value F. r C(t) is the PID input value, representing the actual thrust F; E(t) is the error value, satisfying the following formula:

[0062] E(t) = R(t) - C(t);

[0063] U(t) is the real-time thrust F1 after the actual thrust F is adjusted by the PID controller, and U(t) satisfies the following equation:

[0064]

[0065] The throttle adjusts the pressure to bring the actual pressure closer to the target pressure value r(t), and the working fluid flow rate changes accordingly.

[0066] r(t) is the PID target value, representing the pressure target value; c(t) is the PID input value, representing the actual pressure obtained by remote measurement from the pressure sensor of the storage and supply system; e(t) is the error value, satisfying the following formula:

[0067] e(t) = r(t) - c(t);

[0068] u(t) is the real-time pressure after e(t) is adjusted by the PID controller, and u(t) satisfies the following equation:

[0069]

[0070] As the real-time pressure changes, the real-time thrust F1 changes accordingly to F2;

[0071] The solenoid valve adjusts the duty cycle to change the working fluid flow rate, thereby changing the real-time thrust F2. The real-time thrust F3 is obtained through thrust calculation.

[0072] Continuously monitor whether the actual thrust reaches the thrust target value or the actual pressure reaches the pressure target value during the above process; if it does, the process is complete; otherwise, update the actual thrust to the real-time thrust F3 and repeat S5.

[0073] In summary, the thrust control method for microwave ion propulsion systems provided by this invention receives the target thrust value from the satellite's integrated computer, adjusts the upstream pressure of the throttle via a PID algorithm, and finely adjusts the duty cycle of the solenoid valve to improve thrust accuracy and meet the high-precision and high-stability thrust requirements of microsatellites. Furthermore, even after the thruster performance degrades in the later stages of the propulsion system's lifespan, it can still maintain stable thrust output through autonomous working propellant flow regulation, avoiding the thrust degradation caused by the performance decline of propulsion system components. This enables high-quality completion of tasks such as orbit maintenance and deorbiting, ensuring stable on-orbit operation of the satellite.

[0074] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A thrust control method for a microwave ion propulsion system, characterized in that, The microwave ion propulsion system includes a thruster, a storage and supply subsystem, a PID controller, a microwave source, and a high-voltage power supply; the thrust control method includes the following steps: S1: Based on the design performance indicators of the thruster, determine the final output thrust range of the microwave ion propulsion system and set the working fluid flow rate adjustment range of the thruster under rated operation. S2: Based on the mechanical characteristics of the working fluid flow control components of the storage and supply subsystem, set the duty cycle adjustment range of the thruster solenoid valve; S3: Set the pressure regulation range controlled by the thruster throttle valve according to the pressure characteristics of the storage and supply subsystem pipeline; S4: Construct a PID controller and determine the PID parameters; input the thrust target value and the actual thrust, and use PID control through ground experiments. Adjust the working fluid flow rate within the working fluid flow rate adjustment range set in S1, and perform PID pressure adjustment and PID duty cycle adjustment until the final output thrust of the thruster reaches the thrust target value, and obtain the pressure target value and duty cycle target value; wherein, the thrust target value is within the final output thrust range determined in S1, the pressure target value is within the pressure adjustment range set in S3, and the duty cycle target value is within the duty cycle adjustment range set in S2; S5: The PID parameters are embedded into the microcontroller program of the controller. Given the target thrust value within the final output thrust range determined by S1, the microwave ion propulsion system works together to make the final output thrust automatically reach the target thrust value without having to set the pressure target value and duty cycle target value again. The actual thrust in S4 is influenced by the combined effects of the thruster beam voltage and beam current. The beam voltage is generated by the high-voltage power supply of the microwave ion propulsion system, and the beam current is determined by the working fluid flow rate, ionization efficiency, and accelerating electric field between the grids. The actual thrust F satisfies the following thrust formula: ； in, This is the beam divergence compensation coefficient; This is the compensation coefficient for dual-charged ions; Xenon atomic mass; It is the charge constant; Beam voltage; For beam current.

2. The thrust control method for a microwave ion propulsion system as described in claim 1, characterized in that, In S1, the required thrust output range of the propulsion system is set to 0.2~0.5mN, and the working fluid flow rate adjustment range of the thruster under rated operation is set to 0.2~0.7sccm.

3. The thrust control method for a microwave ion propulsion system as described in claim 1, characterized in that, Under the same actual thrust, the thruster can be matched with different gate voltages and thruster working fluid flow rates according to the on-orbit operating requirements.

4. The thrust control method for a microwave ion propulsion system as described in claim 1, characterized in that, In step S4, the PID controller will input the value and target value By comparing the two, the error values ​​are obtained. , Satisfy the following formula: ； Error value As a control input, the adjusted output value To reach or remain within the target value error range, Satisfy the following formula: ， in, For the proportional parameter of the PID, These are the integral parameters of the PID controller. These are the differential parameters of the PID controller.

5. The thrust control method for a microwave ion propulsion system as described in claim 4, characterized in that, The PID pressure regulation in S4 specifically involves using the difference between the actual thrust and the target thrust value as the control variable, controlling the working fluid flow rate of the throttle to regulate the actual pressure within the pressure regulation range set in S3, and using PID regulation to monitor the actual thrust. When the actual thrust reaches the thrust target value, the current actual pressure becomes the pressure target value, the current duty cycle becomes the duty cycle target value, and S4 stops; otherwise, PID duty cycle adjustment is performed.

6. The thrust control method for a microwave ion propulsion system as described in claim 5, characterized in that, The PID duty cycle adjustment in S4 is specifically as follows: the difference between the actual thrust and the target thrust value is used as the control quantity, the solenoid valve adjusts the duty cycle within the duty cycle adjustment range set in S2, adjusts the working fluid flow rate, and uses PID adjustment to monitor the actual thrust. When the actual thrust reaches the thrust target value, the current duty cycle is the duty cycle target value, the current actual pressure is the pressure target value, and S4 stops; otherwise, PID pressure regulation is performed.

7. The thrust control method for a microwave ion propulsion system as described in claim 6, characterized in that, In S4, the larger the duty cycle controlled by the solenoid valve, the larger the target pressure value, and the larger the working fluid flow rate.

8. The thrust control method for a microwave ion propulsion system as described in any one of claims 1 to 7, characterized in that, The beam current is deduced from the thrust formula, and the beam current is monitored in real time; the actual thrust corresponds to the actual beam current, and the target thrust value corresponds to the target beam current value. The difference between the actual beam current and the target beam current value is used as the control variable. The working fluid flow is adjusted using a throttle or solenoid valve, while the beam current is monitored using PID control. When the actual beam current reaches the target beam current value, the actual thrust reaches the target thrust value, the current duty cycle is the target duty cycle value, and the current actual pressure is the target pressure value. Stop S4. Otherwise, perform PID pressure adjustment or PID duty cycle adjustment.

9. The thrust control method for a microwave ion propulsion system as described in claim 1, characterized in that, In S5, the PID controller adjusts the working parameters of each component by sending control signals; the storage and supply system provides working fluid to the thruster; the microwave source inputs microwaves into the thruster discharge chamber, which together with the magnetic field in the thruster discharge chamber form an electron cyclotron resonance region. After the free electrons are accelerated, they ionize the working fluid to generate plasma. In this plasma, ions are accelerated and ejected under the action of the accelerating electric field formed by the screen grid and the acceleration grid to form thrust.

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