A regulating device capable of inhibiting low-frequency thrust noise of micro-cow-level cold-gas thruster

Abstract

The present application relates to a kind of regulating device of low-frequency thrust noise of micro-cow level cold gas thruster, it is related to the field of thruster for spaceflight, including fan-shaped first blade, fan-shaped second blade with first blade symmetrical distribution, erect in the entrance of first blade and second blade Laval micro-nozzle, control the first ultrasonic motor of the acute angle amplitude of first blade rotation along micro-nozzle outlet end and control the second ultrasonic motor of the acute angle amplitude of second blade rotation along micro-nozzle outlet end, first blade and second blade enclose fan-shaped outlet and opening included angle changes are 30°~60°To make the low-frequency thrust noise suppression rate of thruster in 0.001Hz~0.01Hz frequency band greater than or equal to 90%, the present application has the advantages that ultrasonic motor is used to drive tail jet blade rotation adjustment expansion ratio, realize the high-frequency response regulation of outlet thrust, further suppress low-frequency thrust noise.

Description

Technical Field

[0001] This invention relates to the field of aerospace thrust technology, and in particular to a control device for suppressing low-frequency thrust noise of micro-Newton level cold gas thrusters. Background Technology

[0002] Space-based gravitational wave detection, high-precision Earth gravity field measurement, and reference frame drag effect measurement are all fundamental space physics field areas that countries are vying to control, and are key to achieving significant breakthroughs in space-based fundamental physics research. Accurate detection of next-generation space-based fundamental physics data requires satellite platforms to have residual perturbation acceleration noise within the measurement frequency band of less than 10–15 m / s². 2 / Hz, there is an urgent need for ultra-low noise, ultra-high resolution micro-Newton level variable thrust control technology to provide micro-Newton level extremely small thrust for satellite platforms to counteract the extremely small interferences of non-conservative forces such as atmosphere, solar radiation pressure, and cosmic particles, to form a flight environment under the action of almost "pure gravity", to achieve "drag-free control", and to ensure the technical requirements of the payload for an ultra-quiet working environment.

[0003] Currently, both NASA and ESA are actively planning and developing next-generation ultra-precise drag-free control satellite platforms. ESA has proposed the next-generation gravity field measurement satellite NGGM based on GOCE, and has selected micro-Newton level cold gas variable thrust control technology as the preferred option. The next-generation space-based gravitational wave detection project LISA, jointly planned by NASA and ESA, is scheduled for launch around 2030, and its residual perturbation acceleration noise will be below 10⁻¹⁴ m / s². 2 / Hz (0.1mHz~1Hz), which improves the existing technical performance by five orders of magnitude. It can be seen that the thruster needs to achieve extremely low noise response in the 0.001~1Hz frequency band while outputting thrust at the μN level.

[0004] Currently, the main method used is to employ cold gas thrusters (such as nitrogen or xenon propulsion) to achieve thrust output through throttling control via a fixed nozzle structure. However, this method has a slow response speed, especially under low-frequency disturbances, making rapid adjustment difficult. More seriously, because the expansion ratio is not adjustable, the nozzle's response to exit flow field disturbances is sluggish, thus amplifying thrust noise.

[0005] Authorization notice number CN116006360B discloses an irregularly shaped Laval micro-nozzle. This structure features a threaded nozzle core within the nozzle seat, allowing for adjustment of the nozzle's throat characteristics by extending and retracting the nozzle core along the nozzle channel. By replacing nozzle cores with different tapers or moving their position, the nozzle throat diameter can be steplessly adjusted within a range of micrometers to hundreds of micrometers. However, this approach only changes the throat size, while the expansion section size remains fixed. Furthermore, the nozzle exit geometry is not adjustable after manufacturing, making it difficult to actively control jet exit disturbances.

[0006] Application publication number CN114455105A discloses a micro-Newton level gemstone-based dual-capacity variable thrust closed-loop cold gas thruster and its operation method. Its structure consists of a working gas inlet, a primary gas container, a connecting channel, a secondary gas container, and a nozzle outlet arranged sequentially within a soft magnetic shell. A Laval nozzle body made of gemstone material is installed at the outlet. The nozzle is equipped with a valve assembly with a return spring at the narrow throat inlet. The valve is opened and closed by an electromagnetic coil to achieve closed-loop regulation of the airflow. This device, using a T-valve and a dual-stage gas container, can control the flow rate at the primary gas container inlet and the nozzle outlet in real time, enabling the thruster to obtain continuous and variable flow output and provide sustained and stable thrust. Although this scheme can improve thrust accuracy and stabilize output, its nozzle structure is a Laval nozzle with a fixed expansion ratio, and the nozzle geometry is invariable. Therefore, it cannot directly suppress low-frequency thrust disturbances by changing the nozzle expansion ratio. Existing variable expansion ratio nozzles are mostly used in high-thrust engines (such as variable geometry rocket nozzles). However, they are complex in structure, large in size, and slow in response, making them unsuitable for mass-constrained microthrust systems.

[0007] To address the above shortcomings, a control device is needed to suppress low-frequency thrust noise in micro-Newton level cold gas thrusters. Summary of the Invention

[0008] (a) Technical problems to be solved The technical problem to be solved by this invention is to address the issues of traditional fixed nozzle structures being unable to actively suppress low-frequency thrust noise and having a slow response speed.

[0009] (II) Technical Solution To address the aforementioned technical problems, this invention provides a control device for suppressing low-frequency thrust noise in a micro-Newton level cold gas thruster. The device includes a fan-shaped first blade, a fan-shaped second blade symmetrically distributed with the first blade, a Laval micro-nozzle mounted at the inlet ends of the first and second blades, a first ultrasonic motor controlling the acute angle of rotation of the first blade along the outlet end of the micro-nozzle, and a second ultrasonic motor controlling the acute angle of rotation of the second blade along the outlet end of the micro-nozzle. The first and second blades form a fan-shaped outlet with an opening angle varying from 30° to 60°, ensuring that the low-frequency thrust noise suppression rate of the thruster in the 0.001 Hz to 0.01 Hz frequency band is greater than or equal to 90%.

[0010] As a further explanation of the present invention, preferably, the rated torque of the first ultrasonic motor and the second ultrasonic motor is 0.003 N·m, and the built-in photoelectric encoder has a resolution of 0.001° so that the angle adjustment accuracy of the first blade and the second blade is ±0.03°.

[0011] As a further explanation of the present invention, preferably, the first ultrasonic motor and the second ultrasonic motor are connected to the Invar base via a flange, and the Invar base has a thermal expansion coefficient of less than or equal to 1.2 × 10⁻⁶. 6 / ℃.

[0012] As a further explanation of the present invention, preferably, both the first ultrasonic motor and the second ultrasonic motor are connected to the first blade and the second blade via precision couplings, so that the transmission accuracy reaches ±0.01°.

[0013] As a further explanation of the present invention, preferably, the first ultrasonic motor and the second ultrasonic motor are electrically connected to a control module, and the control module has a built-in PID algorithm with a proportional coefficient of 0.5 to 1.2, an integral time of 0.1 to 0.3 s, and a derivative time of 0.02 to 0.05 s.

[0014] As a further explanation of the present invention, preferably, the surfaces of the first blade and the second blade are both coated with a titanium nitride coating of 50-100 μm.

[0015] As a further explanation of the present invention, preferably, the micro-nozzle is made of alumina ceramic, and the coefficient of thermal expansion of the micro-nozzle is less than or equal to 4.5 × 10⁻⁶. 6 / ℃.

[0016] As a further explanation of the present invention, preferably, the diameter of the throat of the micro-nozzle is 0.3 mm.

[0017] As a further explanation of the present invention, preferably, the plane distance between the rotation axis of the first blade and the micro-nozzle outlet is 0.07 mm.

[0018] As a further explanation of the present invention, preferably, the distance between the rotation axis of the first blade and the axis of the micro-nozzle is 0.1 to 0.4 times the diameter of the micro-nozzle throat.

[0019] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: 1. This invention, through an innovative adaptive expansion ratio control device, achieves a low-frequency thrust noise suppression rate exceeding 90% in the 0.001–0.01 Hz frequency band for micro-Newton thrusters, solving the technical challenge of traditional fixed nozzle structures being unable to actively suppress low-frequency thrust disturbances. This device uses an ultrasonic motor to drive the rotation of interdigitated blades to adjust the expansion ratio, with a response time of less than 1 ms, 20 times faster than traditional solenoid valve control, significantly improving the real-time performance of thrust control. 2. This invention achieves continuous and precise adjustment of the nozzle exit cross-sectional area (adjustment range 30°~60°) through an optimized interdigitated blade design, while maintaining structural compactness (overall weight less than 200g). The blades are coated with a titanium nitride wear-resistant coating with a friction coefficient ≤0.15, ensuring long-term operational reliability and a service life exceeding 106 adjustment cycles. 3. This invention constructs a complete closed-loop feedback system by integrating a MEMS micro-flow sensor (accuracy ±0.1%) and an adaptive PID control algorithm. This system can identify the working fluid disturbance characteristics in the 0.001–10 Hz frequency band in real time and achieve precise compensation of thrust output by adjusting the blade angle, with a control accuracy of ±0.1 μN. 4. This invention utilizes an alumina ceramic nozzle (temperature resistance ≥1600℃) and an Invar base (thermal expansion coefficient ≤1.2×10⁻⁶). -6 The material combination ( / ℃) ensures the dimensional stability of the device in the extreme temperature environment of space (-50℃~+120℃), fully meeting the stringent requirements of space basic physics exploration missions for ultra-quiet environments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the control device structure of the present invention; Figure 2 This is a cross-sectional schematic diagram of the control device of the present invention.

[0021] In the diagram: 1. First blade; 2. Second blade; 3. Micro-nozzle; 4. First ultrasonic motor; 5. Second ultrasonic motor. Detailed Implementation

[0022] 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.

[0023] A control device for suppressing low-frequency thrust noise of micro-Newton level cold gas thrusters, combined with Figure 1 , Figure 2The system includes a fan-shaped first blade 1, a fan-shaped second blade 2 symmetrically distributed with the first blade 1, the first blade 1 and the second blade 2 forming a fan-shaped outlet, a Laval micro-nozzle 3 mounted at the inlet ends of the first blade 1 and the second blade 2, a first ultrasonic motor 4 controlling the acute angle of rotation of the first blade 1 along the outlet end of the micro-nozzle 3, and a second ultrasonic motor 5 controlling the acute angle of rotation of the second blade 2 along the outlet end of the micro-nozzle 3. The first ultrasonic motor 4 and the second ultrasonic motor 5 are connected to an Invar base via a flange, and the Invar base has a thermal expansion coefficient of less than or equal to 1.2 × 10⁻⁶. 6 / ℃.

[0024] Combination Figure 1 , Figure 2 Both the first blade 1 and the second blade 2 are finger-shaped blades with different structures. Both blades are coated with a 50–100 μm titanium nitride coating, resulting in a friction coefficient ≤0.15. This wear-resistant coating significantly reduces frictional losses between the blades and the airflow, extending their service life to over 106 adjustment cycles. The opening angle between the first blade 1 and the second blade 2 varies from 30° to 60°. The symmetrical arrangement of the first blade 1 and the second blade 2 achieves thrust vector neutrality, preventing the introduction of additional torque. The distance L2 between the rotation axis of the first blade 1 and the axis of the micro-nozzle 3 is 0.1 mm, and the relationship between this distance and the throat diameter L1 of the micro-nozzle 3 satisfies 0.1L1≤L2≤0.4L1. This dimensional relationship ensures that the exit area can be continuously changed during blade rotation, achieving an adjustment range of 30°–60°, while avoiding interference with the inner wall of the micro-nozzle 3. The rotation axis of both the first blade 1 and the second blade 2 is 0.07 mm away from the outlet plane of the micro-nozzle 3, which ensures a smooth transition of airflow between the outlet of the micro-nozzle 3 and the first blade 1 and the second blade 2, avoiding flow separation.

[0025] Combination Figure 1 , Figure 2 The micro-nozzle 3 is made of alumina ceramic, with a throat diameter L1 of 0.3 mm and a thermal expansion coefficient of ≤4.5×10⁻⁶. 6 / ℃. The ceramic material is resistant to high temperatures and corrosion, and its coefficient of thermal expansion with the Invar base is ≤1.2×10. -6 / ℃ matching ensures dimensional stability within a temperature range of -50℃ to +120℃.

[0026] Combination Figure 1 , Figure 2The first ultrasonic motor 4 and the second ultrasonic motor 5 are 12mm closed-loop controlled piezoelectric motors of model SJ-PXS-012-15, with a rated torque of 0.003 N·m and a built-in photoelectric encoder with a resolution of 0.001°, ensuring a blade angle adjustment accuracy of ±0.03°, meeting the requirements of micro-Newton thrust control. Furthermore, the piezoelectric drive is free from electromagnetic interference, making it suitable for space-sensitive environments. Both the first ultrasonic motor 4 and the second ultrasonic motor 5 are connected to the first blade 1 and the second blade 2 via precision couplings to achieve a transmission accuracy of ±0.01°.

[0027] In addition, this device is equipped with a flow sensor. The flow sensor is a MEMS micro-flow sensor with a range of 0–10 mL / min and a built-in temperature compensation algorithm. The flow sensor is embedded in the working fluid pipeline via a quick-release connector, with the sensor probe flush with the inner wall of the pipeline to avoid flow field disturbance. The flow sensor is used to detect fluctuations in the working fluid flow rate in real time (accuracy ±0.1%), providing crucial feedback signals to the control module. Its response bandwidth is ≥100Hz, meeting the requirements for low-frequency noise detection.

[0028] This device is also equipped with an additional control module. The control module integrates a 32-bit ARM processor and runs an adaptive PID algorithm with a proportional gain of 0.5–1.2, an integral time of 0.1–0.3 s, and a derivative time of 0.02–0.05 s. The control module connects to each component via shielded cables and uses aviation connectors to ensure reliable connections. The control module is used to acquire flow signals. It incorporates an adaptive filtering algorithm that can separate disturbance components in the 0.001–10 Hz frequency band in real time. It can automatically adjust control parameters for disturbances of different frequencies, maintaining optimal suppression across the entire frequency band. This allows it to calculate the target thrust to be adjusted and output angle control commands to the ultrasonic motor, achieving real-time adaptive angle control of the first blade 1 and the second blade 2. This results in millisecond-level closed-loop control and a thrust noise suppression rate >90%.

[0029] In summary, this invention utilizes an ultrasonic motor to drive the tail nozzle blades to rotate and adjust the expansion ratio, thereby achieving high-frequency response control of the exit thrust and suppressing low-frequency thrust noise. This solves the problem of low-frequency thrust disturbance in current micro-Newton-class cold gas thrusters during on-orbit operation, particularly addressing the issue of uncontrollable thrust noise in the 0.001–0.01 Hz frequency band during space-based fundamental physics exploration missions (such as gravitational wave detection, Earth's gravity field measurement, and reference frame towing experiments).

[0030] 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 control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster, characterized in that: It includes a fan-shaped first blade (1), a fan-shaped second blade (2) symmetrically distributed with the first blade (1), a Laval micro-nozzle (3) mounted at the inlet end of the first blade (1) and the second blade (2), a first ultrasonic motor (4) controlling the acute angle of rotation of the first blade (1) along the outlet end of the micro-nozzle (3), and a second ultrasonic motor (5) controlling the acute angle of rotation of the second blade (2) along the outlet end of the micro-nozzle (3). The first blade (1) and the second blade (2) form a fan-shaped outlet with the included angle varying from 30° to 60° so that the low-frequency thrust noise suppression rate of the thruster in the 0.001Hz to 0.01Hz frequency band is greater than or equal to 90%.

2. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 1, characterized in that: The first ultrasonic motor (4) and the second ultrasonic motor (5) have a rated torque of 0.003 N·m and a built-in photoelectric encoder with a resolution of 0.001° to adjust the angle of the first blade (1) and the second blade (2) with an accuracy of ±0.03°.

3. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 2, characterized in that: The first ultrasonic motor (4) and the second ultrasonic motor (5) are connected to the Invar base via flanges. The Invar base has a thermal expansion coefficient of less than or equal to 1.2 × 10⁻⁶. 6 / ℃.

4. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 3, characterized in that: The first ultrasonic motor (4) and the second ultrasonic motor (5) are both connected to the first blade (1) and the second blade (2) through precision couplings so that the transmission accuracy reaches ±0.01°.

5. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 4, characterized in that: The first ultrasonic motor (4) and the second ultrasonic motor (5) are electrically connected to a control module. The control module has a built-in PID algorithm with a proportional coefficient of 0.5 to 1.2, an integral time of 0.1 to 0.3 s, and a derivative time of 0.02 to 0.05 s.

6. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 5, characterized in that: Both the first blade (1) and the second blade (2) are coated with a titanium nitride coating of 50-100 μm.

7. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 6, characterized in that: The micro-nozzle (3) is made of alumina ceramic, and its coefficient of thermal expansion is less than or equal to 4.5 × 10⁻⁶. 6 / ℃.

8. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 7, characterized in that: The throat diameter of the micro-nozzle (3) is 0.3 mm.

9. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 8, characterized in that: The plane distance between the rotation axis of the first blade (1) and the second blade (2) and the outlet of the micro-nozzle (3) is 0.07 mm.

10. The control device for suppressing low-frequency thrust noise of a micro-Newton level cold gas thruster according to claim 9, characterized in that: The rotation axis of the first blade (1) and the second blade (2) is 0.1 to 0.4 times the throat diameter of the micro-nozzle (3) at a distance of 0.1 to 0.4 times the axis of the micro-nozzle (3).

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