A displacement sensor for micro-newton class variable thrust engines

Abstract

The application discloses a displacement sensor for micro-cow level variable thrust engine and belongs to the field of precision measurement. The displacement sensor comprises a polymer film base, one strain grid resistor and three compensation resistors. The compensation resistors are arranged on the top section of the base, and the strain grid resistor is arranged on the middle section of the base. The length of the bottom section of the base is greater than the sum of the lengths of the top section and the middle section, so that the displacement sensor presents an asymmetric U-shaped bending structure during installation and use. During use, the displacement sensor converts the relative displacement of two ends into the change of the bending strain of the polymer film, and then causes the resistance value of the strain grid resistor to change. The application has the characteristics of high precision, low cost and light weight, can be stably used in a wide temperature range environment, and is easy to install and suitable for various application scenarios.

Description

Technical Field

[0001] This invention relates to the field of precision measurement technology, and in particular to a displacement sensor for a micro-Newton level variable thrust generator. Background Technology

[0002] Micro-Newton (MN) level variable thrust generators produce continuously adjustable thrust and are primarily used for ultra-high precision attitude control and drag-free flight of spacecraft. They consist of a Laval nozzle, valve body, valve core assembly, and piezoelectric actuation assembly. Displacement signals are crucial for thrust control in variable thrust generators. Displacement sensors measure minute displacements of the piezoelectric actuation components in real time, ensuring that adjustments match the expected thrust. Furthermore, historical data from the displacement sensors, combined with intelligent algorithms, can be used to analyze component lifespan trends, optimize maintenance cycles, and reduce mission risks.

[0003] Displacement sensors used in micro-Newton level variable thrust generators need to be lightweight, miniaturized, and have good temperature adaptability due to the special nature of their application scenarios. Traditional displacement sensors are heavy and bulky, which limits their in-depth application in high-end fields such as aerospace and precision manufacturing.

[0004] Therefore, there is an urgent need for a displacement sensor for micro-Newton level variable thrusters to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a displacement sensor for a micro-Newton level variable thrust generator, characterized by high precision, lightweight, miniaturization, and high adaptability to temperature environments. The technical solution is as follows: On one hand, a displacement sensor for a micro-Newton level variable thrust generator is provided, the displacement sensor comprising a strain gauge resistor and three compensation resistors fixed on a substrate, wherein: The compensation resistors are all disposed in the top section of the substrate, and the strain gauge resistors are disposed in the middle section of the substrate; The length of the bottom section of the substrate is greater than the sum of the lengths of the top section and the middle section, so that the displacement sensor presents an asymmetrical U-shaped bending structure when in use. As a result, the maximum bending position of the displacement sensor moves significantly with the increase of displacement, and moves from a position far away from the strain gauge resistor to the position where the strain gauge resistor is located, ultimately causing a large change in the resistance value of the strain gauge resistor.

[0006] On the other hand, a method for using a displacement sensor in a micro-Newton level variable thrust generator is provided, the method comprising: The two ends of the displacement sensor are fixedly connected to the piezoelectric drive module to be measured and the thruster housing, respectively; When the piezoelectric drive module generates displacement, the resistance change of the strain gauge resistor is measured using an external circuit. The displacement change value of the piezoelectric drive module is determined based on the resistance change value.

[0007] The technical solution provided by this invention offers at least the following advantages: A substrate is fabricated using an insulating polymer composite film, and both the strain gauge resistor and the compensation resistor are fixed on the substrate. Furthermore, different lengths are designed for different parts of the substrate, thus forming a displacement sensor with an asymmetric U-shaped bending structure. This sensor has a simple fabrication process, low cost, and is easy to mass-produce. Due to its good overall structural flexibility and low stress, the sensor can be glued to the inside of the thruster, achieving non-invasive integration without the need for complex processes such as welding. This shortens installation time, facilitates installation, and avoids potential damage to the thruster's precision structure caused by welding thermal stress, making it particularly suitable for sensitive scenarios such as spacecraft propulsion systems. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of a displacement sensor structure for a micro-Newton level variable thruster provided in an embodiment of the present invention; Figure 2 This is a circuit connection diagram of the strain gauge resistor and the compensation resistor provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the displacement sensor arrangement and strain gauge resistance stress provided in an embodiment of the present invention.

[0010] Figure label: 1-Strain gauge resistance; 2, 3, 4 - Compensation resistors; 5-Polymer substrate; 6-Piezoelectric actuator; 7-Outer shell. 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 some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0012] As mentioned earlier, common limitations of existing displacement sensor technologies include heavy weight and large size, which restricts their in-depth application in high-end fields such as aerospace and precision manufacturing.

[0013] Based on this, the present invention is to provide a displacement sensor for a micro-Newton level variable thruster, which is small in size, light in weight, easy to install, and has high temperature adaptability.

[0014] The specific implementation of the above concept is described below.

[0015] Please refer to Figure 1 This invention provides a displacement sensor for a micro-Newton level variable thrust generator. The displacement sensor includes a polymer thin film substrate, a strain gauge resistor, and three compensation resistors, wherein: The compensation resistors are all disposed in the top section of the substrate, and the strain gauge resistors are disposed in the middle section of the substrate; In use, the displacement sensor converts the relative displacement at both ends into a change in the bending strain of the polymer film, which in turn causes a change in the resistance of the strain gauge resistor.

[0016] The following description Figure 1 The various parts shown.

[0017] In this embodiment of the invention, the strain gauge resistor and the compensation resistor are configured as follows: Figure 2 The Wheatstone bridge shown is used for connection to perform temperature compensation on the strain gauge resistor. The resistor material can be constantan alloy or gold or other metal materials.

[0018] Furthermore, the relationship between the strain gauge resistance and the compensation resistance satisfies the following formula: In the formula, R 1 represents the strain gauge resistance; R 2. R 3 and R 4 are all compensation resistors.

[0019] In this embodiment of the invention, the polymer film selected for the substrate is a polyimide film with a thickness not exceeding 50 micrometers to prevent the resistive material from exceeding the elastic strain limit. The length of the bottom section of the substrate is greater than the sum of the lengths of the top section and the middle section, so that the displacement sensor presents an asymmetrical U-shaped bending structure during installation and use. At the same time, the width of the middle section of the substrate is less than the width of all other positions of the substrate. As a result, the maximum bending position of the displacement sensor moves significantly with the increase of displacement, and moves from a position far away from the strain gauge resistor to the position where the strain gauge resistor is located, ultimately causing a large change in the resistance value of the strain gauge resistor.

[0020] The actual installation location of the displacement sensor is as follows: Figure 3 As shown, during the measurement process, one end A (moving element) of the displacement sensor is connected to the piezoelectric actuator, and the other end B (stationary element) is bonded to the inner wall of the thruster housing. When the piezoelectric actuator generates displacement, the coordinates of the moving element change accordingly, and the magnitude of the strain gauge resistance changes accordingly. In the initial state, the maximum bending point of the sensor is located on the right side of the strain gauge, at which point the bending strain at the strain gauge is approximately zero; after the piezoelectric actuator generates displacement, the maximum bending point is located in the strain gauge, the stress state of the strain gauge changes, and the strain gauge undergoes significant deformation from the initial state, resulting in a corresponding change in the strain gauge resistance.

[0021] Furthermore, the strain gauge resistor and compensation resistor are electrically connected to an external circuit, which is used to measure the bridge voltage change in real time, thereby calculating the value of the strain gauge resistor. Since there is a corresponding relationship between this resistance value and the displacement of the piezoelectric actuator, the displacement information of the actuator can be obtained in real time through the resistance change, thus providing key input parameters for the precise control of the thruster.

[0022] Furthermore, to ensure high resolution of the displacement sensor, the width of the strain gauge resistor must be smaller than the width at other locations. This allows for a larger strain and resistance change at the strain gauge after the same displacement change. Additionally, the lengths of the three parts satisfy L3 > L1 + L2, ensuring that the bending strain at the strain gauge is approximately zero at the initial moment. The Wheatstone bridge design ensures that the sensor can achieve temperature self-compensation over a wide temperature range, thus meeting the requirements for stable operation of the thruster over a wide temperature range.

[0023] The displacement sensor described above has the following advantages in terms of practicality: Low-cost mass production adaptability: The fabrication process is simple, low-cost, and easy to mass-produce. Based on MEMS microfabrication technology and standardized material systems (such as polyimide flexible substrates), the unit manufacturing cost is reduced by more than 60% compared with traditional metal sensors, supporting mass production.

[0024] Stress-free rapid installation technology: Due to the good flexibility and low stress of the overall structure, the sensor can be fixed inside the thruster by adhesive, achieving non-invasive integration. It does not require complex processes such as welding, shortens the installation time, is easy to install, and avoids the potential damage to the precision structure of the thruster caused by welding thermal stress. It is especially suitable for sensitive scenarios such as spacecraft propulsion systems.

[0025] Ultra-lightweight and dynamically compatible design: Adopting a thin-film structure, the overall weight is light and does not affect the motion state of the object being measured, making it suitable for a variety of application scenarios.

[0026] Wide temperature range self-compensation performance: Temperature self-compensation is achieved through the design of the Wheatstone bridge, making it suitable for wide temperature range environments.

[0027] High durability: The conductive material and substrate of this sensor are made of mature materials. During operation, the materials undergo elastic deformation without plastic deformation, resulting in high repeatability and high durability, making it suitable for long-life satellite platforms.

[0028] This invention also provides a method for using a displacement sensor in a micro-Newton level variable thruster, applicable to any of the above embodiments. The method includes: fixing the displacement sensor to the piezoelectric drive module to be measured in the thruster; when the piezoelectric drive module generates displacement, measuring the resistance change value of the strain gauge resistor using an external circuit; and determining the displacement change value of the piezoelectric drive module based on the resistance change value.

[0029] Specifically, fixing the displacement sensor to the piezoelectric drive module to be measured of the thruster includes: bending the displacement sensor, bonding the top section of the base to a preset connection point of the piezoelectric drive module of the thruster to be measured, and bonding the bottom section of the base to a preset connection point of the inner wall of the outer shell of the thruster to be measured.

[0030] It is worth noting that the specific location of the connection point can be determined based on whether the displacement sensor is in a state of free stress at the initial moment.

[0031] Furthermore, after completing the preliminary parameter design, before designing the connection point between the displacement sensor and the thruster, it is necessary to use the commercial software Abaqus to simulate the stress state of the entire sensor after the displacement of the piezoelectric drive component changes, ensuring that the sensor strain gauge is in elastic deformation within the rated variation range. If the corresponding conditions are not met, the strain gauge design needs to be optimized.

[0032] Finally, it should be noted that in this document, relational terms such as first, second, third, and fourth are used only 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 those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A displacement sensor for a micro-Newton level variable thrust generator, characterized in that, The displacement sensor comprises a polymer thin film substrate, a strain gauge resistor, and three compensation resistors, wherein: The compensation resistors are all disposed in the top section of the substrate, and the strain gauge resistors are disposed in the middle section of the substrate; In use, the displacement sensor converts the relative displacement at both ends into a change in the bending strain of the polymer film, which in turn causes a change in the resistance of the strain gauge resistor. The length of the bottom section of the base is greater than the sum of the lengths of the top section and the middle section, so that the displacement sensor presents an asymmetrical U-shaped bending structure during installation and use.

2. The displacement sensor as described in claim 1, characterized in that, The width of the middle section of the base is smaller than the width of the rest of the base to increase the curvature of the middle section.

3. The displacement sensor as described in claim 1, characterized in that, The thickness of the polymer film does not exceed 50 micrometers to prevent the resistive material from exceeding the elastic strain limit.

4. The displacement sensor as described in claim 1, characterized in that, The strain gauge resistor and the compensation resistor are connected via a Wheatstone bridge to provide temperature compensation for the strain gauge resistor.

5. The displacement sensor as described in claim 1, characterized in that, The relationship between the strain gauge resistor and the compensation resistor satisfies the following formula: In the formula, R 1 represents the strain gauge resistance; R 2. R 3 and R 4 are all compensation resistors.

6. The displacement sensor as described in claim 1, characterized in that, The polymer film is a polyimide film, and the resistor is made of constantan alloy or gold.

7. The displacement sensor as described in claim 1, characterized in that, It also includes external circuitry: The external circuit is electrically connected to the strain gauge resistor and the compensation resistor. The external circuit is used to measure the change in bridge voltage in real time, and then calculate the magnitude of the strain gauge resistor to obtain the real-time displacement of the target under test.

8. A method for using a displacement sensor in a micro-Newton level variable thrust generator, characterized in that, Applied to the displacement sensor as described in any one of claims 1-4, the method comprises: The displacement sensor is fixedly connected to the piezoelectric drive module to be measured of the thruster; When the piezoelectric drive module generates displacement, the resistance change of the strain gauge resistor is measured using an external circuit. The displacement change value of the piezoelectric drive module is determined based on the resistance change value.

9. The method as described in claim 8, characterized in that, The displacement sensor is fixedly connected to the piezoelectric drive module to be measured in the thruster, including: After bending the displacement sensor, the top section of the base is bonded to the preset connection point of the piezoelectric drive module of the thruster under test, and the bottom section of the base is bonded to the preset connection point of the inner wall of the outer shell of the thruster under test.

10. The method as described in claim 8, characterized in that, Before designing the connection point between the displacement sensor and the thruster, the following steps are also included: The displacement sensor was simulated and optimized using Abaqus software so that the strain gauge resistor remained in an elastic deformation state within the rated displacement range of the piezoelectric drive module.

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