A center of mass regulating device and method suitable for micro-thrust calibration torsion pendulum

Abstract

This invention discloses a centroid adjustment device and method suitable for micro-thrust calibration of a torsion pendulum. The centroid precision adjustment device includes: a double-base plate torsion pendulum base installed inside a vacuum tank, on which a support frame, a pivot, and a torsion pendulum are provided, with the support frame supporting the torsion pendulum via the pivot; a torsion pendulum tilt angle control mechanism installed on the drive side of the double-base plate torsion pendulum base; a centroid position adjustment mechanism installed on the double-base plate torsion pendulum base and connected to one end of the torsion pendulum; and a controller installed outside the vacuum tank. The method includes: determining whether the current centroid position offset s is less than 10 μm; if so, performing fine adjustment; if not, continuing to control the torsion pendulum tilt angle and then calculating the centroid position offset until the offset s is less than 10 μm. This invention can achieve a torsion pendulum tilt angle control resolution of 5 μrad and simultaneously achieve a centroid positioning accuracy of 1 μm; it can achieve a centroid position adjustment resolution of 1 μm, ensuring that the centroid offset distance of the torsion pendulum axis is no greater than 10 μm.

Description

Technical Field

[0001] This invention belongs to the field of aerospace propulsion technology, specifically a center of mass control device and method suitable for micro-thrust calibration of torsional pendulum. Background Technology

[0002] The micro-thrust calibration torsion pendulum is an important device used to calibrate aerospace micro-thrusters. The position of the pendulum's center of mass affects its anti-interference capability, which in turn affects its key performance indicators such as resolution and noise power. The closer the center of mass is to the axis of rotation, the stronger the pendulum's anti-interference capability.

[0003] In the field of space gravitational wave detection, to achieve accurate calibration of micro-Newton-level thrusters, it is necessary to ensure that the offset between the center of mass of the torsion pendulum and the axis of rotation is controlled within 10 μm. This requirement places extremely high demands on the sensing accuracy, control method, and resolution of the actuator for center of mass adjustment. Currently, the center of mass adjustment of the torsion pendulum mostly relies on manually adding or removing weights to balance the masses on both sides. This method is limited by atmospheric interference and human error, resulting in low adjustment accuracy and difficulty in ensuring that the center of mass position meets the standard. Therefore, researching a high-precision and high-reliability method for torsion pendulum center of mass adjustment is of great significance. This invention aims to achieve micron-level center of mass adjustment accuracy in a micro-Newton-level thrust calibration device, providing reliable testing assurance for micro-Newton-level thrusters. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by proposing a centroid adjustment device and method suitable for calibrating a torsion pendulum with micro-thrust. The aim is to solve the problem that the precise calibration of a micro-Newton thruster relies on manually adding or removing weights to balance the mass on both sides, resulting in low adjustment accuracy and difficulty in ensuring that the centroid position of the torsion pendulum is within 10μm of the offset between the centroid and the axis of rotation.

[0005] The present invention addresses its technical problem by proposing the following technical solution:

[0006] A precision centroid control device for a micro-thrust measurement device is characterized by comprising: a double-base torsion pendulum base disposed within a vacuum chamber, the base having a support frame, a pivot, and a torsion pendulum, the support frame supporting the torsion pendulum via the pivot; a torsion pendulum tilt angle control mechanism disposed on the drive side of the double-base torsion pendulum base; and a centroid position adjustment mechanism disposed on the double-base torsion pendulum base and connected to one end of the torsion pendulum; and a controller disposed outside the vacuum chamber, the controller having its input terminals connected to displacement sensors of the torsion pendulum and the torsion pendulum tilt angle control mechanism, and its output terminals connected to the motor of the centroid position adjustment mechanism and the piezoelectric actuator of the torsion pendulum tilt angle control mechanism, the torsion pendulum tilt angle control mechanism being used to control the tilt angle of the torsion pendulum, which is the tilt angle of the torsion pendulum cross-section along the direction of gravity; the centroid position adjustment mechanism being used to adjust the centroid position of the torsion pendulum; and the controller being used to control the torsion pendulum tilt angle control mechanism and the centroid position adjustment mechanism.

[0007] Furthermore, the controller includes: a centroid position offset calculation module for calculating the centroid deviation position of the torsional yaw, a torsional yaw tilt angle calculation module for calculating the torsional yaw tilt angle, and a PID controller for controlling the torsional yaw tilt angle.

[0008] The controller's center-of-mass offset calculation module is used to calculate the deviation 's' between the center of mass of the torsional pendulum and the rotation axis. Its input terminals are connected to the torsional pendulum and the torsional pendulum tilt angle calculation module, respectively. The current rotation angle θ of the torsional pendulum is obtained from the torsional pendulum, and the actual torsional pendulum tilt angle is obtained from the torsional pendulum tilt angle calculation module. The output end is connected to the center of gravity position adjustment mechanism, which sends the motor drive command to the center of gravity position adjustment module;

[0009] The controller's yaw angle calculation module is used to calculate the yaw angle. Its input end is connected to high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 of the torsion tilt angle control mechanism. Through the measuring points h1 and h2 of high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 respectively, the actual torsion tilt angle between the upper and lower base plates of the double-base plate torsion tilt base is obtained. The output of the torsional tilt angle calculation module is connected to a PID controller, and outputs the actual torsional tilt angle to the PID controller.

[0010] The PID controller of this controller is used to output commands for the axial displacement of the piezoelectric actuator; its input is connected to the torsional tilt angle calculation module to obtain the actual torsional tilt angle. Compare it with the tilt angle set by the controller. In comparison, the output of the PID controller is connected to the piezoelectric actuator of the torsion tilt angle control module, controlling the voltage output of the piezoelectric actuator to the upper plate of the double-base torsion tilt base.

[0011] Furthermore, the torsional tilt angle control mechanism includes: a piezoelectric actuator mounted on the drive side of the double-base plate torsional base; a pivot mounted on the rotational degree of freedom side of the double-base plate torsional base and connecting the upper and lower base plates via the pivot; and high-precision capacitive displacement sensors 1 and 2 mounted on the base plates of the double-base plate torsional base and close to both ends of the upper base plate. The piezoelectric actuator acts as a displacement source; when it outputs an axial displacement voltage, it causes the upper base plate to tilt around the pivot. The high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 are symmetrically arranged at both ends of the double-base torsion base. High-precision capacitive displacement sensor 1 is located at the end closer to the drive side, and high-precision capacitive displacement sensor 2 is located at the end closer to the pivot. When the piezoelectric actuator outputs axial displacement, high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 respectively measure the distances h1 and h2 between the upper and lower base plates, and send h1 and h2 to the torsion calculation module of the controller. The torsion calculation module obtains the tilt angle between the upper and lower base plates using h1 and h2.

[0012] Furthermore, the center of mass position adjustment mechanism includes: a fine-pitch screw, a counterweight block, and a motor; the motor and the counterweight block are coaxial; one end of the fine-pitch screw is fixed to one side along the torsional axis and the torsional block, and the other end passes through the central hole of the counterweight block and is threadedly connected to the central hole of the counterweight block; symmetrical guide holes are opened on both sides of the counterweight block, and two guide shafts with smaller diameters pass through the guide holes and are fixed to the motor; the center of the counterweight block has a pre-made internal thread, forming a precision fit with the screw; when the motor rotates, the two guide shafts will drive the counterweight block to rotate on the fine-pitch screw; the fine-pitch screw converts the angular displacement of the counterweight block into axial linear displacement, causing the counterweight block to move along the torsional axis, thereby changing the center of mass distribution of the torsional block and completing a single adjustment of the center of mass position deviation.

[0013] Furthermore, the torsional tilt angle calculation module obtains the tilt angle between the upper and lower base plates through h1 and h2. Specifically: Set the distance between the two measuring points of high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 to L. Let the gaps on the high and low sides in the tilted state be h1 and h2 respectively. The tilt angle is calculated as follows:

[0014]

[0015] This allows for the accurate measurement of the tilt angle of the torsional pendulum.

[0016] Furthermore, the centroid position deviation calculation module calculates the deviation s between the torsional centroid and the axis of rotation as follows:

[0017] When the center of mass of the torsional pendulum deviates from the axis of rotation, the pendulum will rotate under the torque generated by the gravitational component while in an inclined state. Let the total mass of the torsional pendulum be M, the pivot stiffness coefficient be k, and the distance of the center of mass from the axis of rotation be s. If the tilt angle of the upper base plate around the pivot increases... Afterwards, the rotation angle of the torsional pendulum changes to θ. Then, the mechanical equilibrium equation for the torque of the gravitational component and the restoring torque of the pivot is:

[0018]

[0019] Where g is the acceleration due to gravity, under the assumption of a small angle (cosθ = 1 when θ is sufficiently small), the deviation of the pendulum's center of mass from the axis of rotation can be obtained as follows:

[0020]

[0021] In this equation, θ is precisely measured using the angular displacement measurement function built into the torsion pendulum, k is obtained by calibrating the torsion pendulum, and M can be directly measured using a balance. Therefore, the key to calculating the deviation of the center of mass is to output axial displacement through the piezoelectric actuator, causing the upper base plate to generate a controllable tilt angle around the pivot.

[0022] A method for precise control of the center of mass of a micro-thrust measuring device, characterized by the following steps:

[0023] Step 1: Determine if the current centroid offset s falls within the fine-tuning range;

[0024] Step 2: The torsional tilt angle control module controls the torsional tilt angle. To take control;

[0025] Step 3: The centroid position deviation calculation module calculates the centroid position offset.

[0026] Step 4: Determine if the current centroid position offset s is less than 10um. If yes, complete the fine adjustment and proceed to step 6. If no, continue to step 5.

[0027] Step 5: The center of mass position adjustment module adjusts the center of mass position and returns to Step 2;

[0028] Step Six: Fine-tuning complete.

[0029] The second step of controlling the torsional tilt angle includes the following process:

[0030] 1) The PID controller input receives the set tilt angle. and actual tilt angle

[0031] 2) Determine the set tilt angle and actual tilt angle Does a difference exist? If not, proceed to step 7); if yes, continue to step 3.

[0032] 3) The PID controller outputs voltage to the piezoelectric actuator. When the piezoelectric actuator outputs axial displacement, it causes the upper base plate of the double-base torsion base to tilt around the pivot at an angle.

[0033] 4) High-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 feed back the h1 and h2 of their respective measuring point positions to the tilt angle calculation module of the controller;

[0034] 5) The tilt angle calculation module will calculate the actual tilt angle. Feedback is sent to the input of the PID controller;

[0035] 6) The PID controller adjusts the tilt angle set at the input terminal. and actual tilt angle Perform the difference calculation and return to process 2).

[0036] 7) End.

[0037] The calculation of the centroid position offset s in step three includes the following steps:

[0038] A. Establish the tilt angle generated by the piezoelectric actuator The relationship between the torsional gyroscope's rotation angle θ and the change in rotation angle θ.

[0039]

[0040] B. According to the above The relationship between θ and the given equation yields the deviation S of the torsional centroid from the axis of rotation.

[0041]

[0042] C. Send the deviation amount s to the centroid position adjustment module.

[0043] The centroid position adjustment module in step five adjusts the centroid position, and the specific steps are as follows:

[0044] 1) The controller's center of gravity position offset calculation module sends a drive command to the motor of the center of gravity position adjustment module based on the offset;

[0045] 2) When the motor rotates, the guide shaft will drive the mass block to rotate, completing a single adjustment of the center of mass position deviation.

[0046] Advantages and effects of the present invention

[0047] 1. A closed-loop control architecture based on piezoelectric actuators and high-precision capacitive displacement gauges can achieve a torsional tilt angle control resolution of 5μrad and simultaneously achieve a centroid positioning accuracy of 1μm.

[0048] 2. By changing the mass distribution through the axial displacement of the mass block on the fine-tooth screw, a 1μm-level resolution for adjusting the center of mass position can be achieved, ensuring that the distance between the center of mass of the torsional pendulum and the axis of rotation is no more than 10μm. This effectively suppresses the interference of ground vibration and other disturbances on the torsional pendulum, reduces the noise floor of the torsional pendulum, improves the measurement resolution, and provides a reliable guarantee for the testing and calibration of micro-Newton thrusters.

[0049] 3. The entire process has a mature software implementation solution, which can be operated in a vacuum environment, reducing atmospheric disturbance, improving the accuracy of center of mass adjustment, and simplifying the operation complexity. Attached Figure Description

[0050] Figure 1 This is a structural diagram of the centroid precision control device for micro-thrust calibration according to the present invention;

[0051] Figure 2 The schematic diagram of the centroid precision adjustment module of the present invention is shown in Figure (a), which is a side view and Figure (b) is a top view.

[0052] Figure 3 This is a schematic diagram - perspective view of the tilt control system of the present invention;

[0053] Figure 4 This is a side view of the torsional tilt angle control mechanism of the present invention;

[0054] Figure 5 The centroid position adjustment mechanism of the present invention is shown in Figure (a) as a side view and Figure (b) as a right view.

[0055] Figure 6 This is a flowchart illustrating the overall process of the centroid position adjustment mechanism of the present invention.

[0056] Figure 7 This is the specific process of "torsional tilt angle control" in this invention;

[0057] Figure 8 This is the specific process for "centroid offset adjustment" in this invention. Detailed Implementation

[0058] Design principle of the invention

[0059] I. Innovation of this invention: Establishing the torsional tilt angle The displacement offset s is calculated by relating the displacement angle θ to the torsional rotation angle. A thruster is installed on the drive side of the double-base plate base. When the thruster generates thrust, it causes the upper base plate on the drive side of the double-base plate torsional pendulum base to displace upwards relative to the lower base plate. After the upper base plate displaces upwards, an angle is formed between the upper and lower base plates. Since the torsional pendulum is installed on the upper base plate, the cross-section of the torsional pendulum will also change with the displacement of the upper base plate, resulting in a torsional tilt angle. Twist angle After it is generated, if the center of mass of the torsional pendulum is not on the axis of rotation, the pendulums with greater gravity on both sides of the axis of rotation will rotate in the direction of the gravitational component, resulting in a torsional pendulum rotation angle θ; according to the mechanical equilibrium equation, the torsional pendulum tilt angle can be obtained. The relationship between the centroid and the rotation angle θ is obtained. This relationship allows us to determine the deviation s between the centroid of the torsional pendulum and the axis of rotation. When the deviation s = 0, the centroid of the torsional pendulum is concentric with the axis of rotation. At this time, the interference of environmental common-mode noise on the torsional pendulum is minimized, thus enabling the measured micro-thrust to reach the accuracy requirement of micro-Newtons.

[0060] II. Design Principles of the Center of Gravity Adjustment Device: First, the torsional tilt angle ≠ The angle of rotation θ of a torsional pendulum. Two conditions are required for a torsional pendulum to rotate: its center of mass must deviate from its central point, and it must be subjected to a gravitational component, such as... Figure 2 As shown in the left figure, a torsion pendulum will only rotate by an angle θ when both of these conditions are met: the presence of a gravitational component and a shift in the center of mass of the pendulum. Assuming the center of mass of the pendulum does not shift, we can arbitrarily assign a pendulum tilt angle. Even if the tilt angle is The angle is already close to 90 degrees, but even so, the pendulum will not produce a rotation angle θ. This is because the center of mass has not shifted, and the gravitational force on both sides of the pivot is the same, so the pendulums on both sides of the pivot remain horizontal, meaning the rotation angle θ is zero. Secondly, the center of mass of the pendulum is adjusted using a center-of-mass adjustment mechanism. Thirdly, the adjustment of the pendulum's center of mass is not completed in one step, but requires several adjustments, but after each adjustment, the rotation angle θ of the pendulum will become smaller and smaller. Fourthly, each adjustment of the center of mass requires two steps: the first step is to adjust the previous pendulum tilt angle... The first step is to reset the torsional rotation angle θ to zero; the second step is for the PID controller to re-set the tilt angle. The set tilt angle It can be compared with the previously set tilt angle. They can be the same or different, depending on the setting of the yaw angle. The purpose is to generate a gravitational component, the magnitude of which determines the sensitivity of the torsional pendulum to rotation. However, the pendulum's sensitivity is only one aspect; this gravitational component only affects the pendulum's rotation when its center of mass deviates from its normal position. The degree of deviation of the pendulum's center of mass determines the magnitude of the rotation angle θ; the smaller the deviation, the smaller the rotation angle θ. (Pendulum tilt angle) The magnitude of the angle determines the pendulum's sensitivity, which is related to the gravitational component; the larger the gravitational component, the stronger the pendulum's sensitivity. Therefore, the pendulum's tilt angle... It cannot be too small, nor too large. It only needs to meet the sensitivity requirements of the gyroscope. Gyroscope tilt angle If it's too small, its sensitivity to twisting and turning will be poor.

[0061] Based on the above principles, this invention designs a precision centroid control device suitable for micro-thrust measurement devices, such as... Figure 1As shown, the precision centroid control device includes: a double-base torsion pendulum base installed inside a vacuum tank, on which a support frame, a pivot, and a torsion pendulum are mounted. The support frame supports the torsion pendulum via the pivot. A torsion pendulum tilt angle control mechanism is installed on the drive side of the double-base torsion pendulum base. A centroid position adjustment mechanism is installed on the double-base torsion pendulum base and connected to one end of the torsion pendulum. A controller is installed outside the vacuum tank. The input terminals of the controller are connected to displacement sensors of the torsion pendulum and the torsion pendulum tilt angle control mechanism, respectively. The output terminals are connected to the motor of the centroid position adjustment mechanism and the piezoelectric actuator of the torsion pendulum tilt angle control mechanism, respectively. The torsion pendulum tilt angle control mechanism is used to control the tilt angle of the torsion pendulum, which is the tilt angle of the torsion pendulum cross-section along the direction of gravity. The centroid position adjustment mechanism is used to adjust the centroid position of the torsion pendulum. The controller is used to control the torsion pendulum tilt angle control mechanism and the centroid position adjustment mechanism.

[0062] like Figure 1 , 7 As shown, the controller includes: a centroid position offset calculation module for calculating the centroid deviation position of the torsional pendulum, a torsional pendulum tilt angle calculation module for calculating the torsional pendulum tilt angle, and a PID controller for controlling the torsional pendulum tilt angle.

[0063] like Figure 1 As shown, the centroid position offset calculation module of the controller is used to calculate the deviation s between the centroid of the torsional pendulum and the axis of rotation. Its input terminals are connected to the torsional pendulum and the torsional pendulum tilt angle calculation module, respectively. The current rotation angle θ of the torsional pendulum is obtained from the torsional pendulum, and the actual torsional pendulum tilt angle is obtained from the torsional pendulum tilt angle calculation module. The output end is connected to the center of gravity position adjustment mechanism, which sends the motor drive command to the center of gravity position adjustment module;

[0064] like Figure 1 As shown, the torsional tilt angle calculation module of this controller is used to calculate the torsional tilt angle. Its input end is connected to high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 of the torsion tilt angle control mechanism. Through the measuring points h1 and h2 of high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 respectively, the actual torsion tilt angle between the upper and lower base plates of the double-base plate torsion tilt base is obtained. The output of the torsional tilt angle calculation module is connected to a PID controller, and outputs the actual torsional tilt angle to the PID controller.

[0065] like Figure 1 As shown, the PID controller of this controller is used to output the axial displacement command of the piezoelectric actuator; its input terminal is connected to the torsional tilt angle calculation module to obtain the actual torsional tilt angle. Compare it with the tilt angle set by the controller. In comparison, the output of the PID controller is connected to the piezoelectric actuator of the torsion tilt angle control module, controlling the voltage output of the piezoelectric actuator to the upper plate of the double-base torsion tilt base.

[0066] like Figure 4 As shown, the torsional tilt angle control mechanism includes: a piezoelectric actuator mounted on the drive side of the double-base plate torsional base; a pivot mounted on the rotational degree of freedom side of the double-base plate torsional base and connecting the upper and lower base plates via the pivot; and high-precision capacitive displacement sensors 1 and 2 mounted on the base plate of the double-base plate torsional base and near both ends of the upper base plate. The piezoelectric actuator acts as a displacement source; when it outputs an axial displacement voltage, it causes the upper base plate to tilt around the pivot at an angle. The high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 are symmetrically arranged at both ends of the double-base torsion base. High-precision capacitive displacement sensor 1 is located at the end closer to the drive side, and high-precision capacitive displacement sensor 2 is located at the end closer to the pivot. When the piezoelectric actuator outputs axial displacement, high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 respectively measure the distances h1 and h2 between the upper and lower base plates, and send h1 and h2 to the torsion calculation module of the controller. The torsion calculation module obtains the tilt angle between the upper and lower base plates using h1 and h2.

[0067] like Figure 5 As shown, the center of mass position adjustment mechanism includes: a fine-pitch screw, a counterweight block, and a motor; the motor and the counterweight block are coaxial; one end of the fine-pitch screw is fixed to one side along the torsional axis and the torsional block, and the other end passes through the central hole of the counterweight block and is threadedly connected to the central hole of the counterweight block; symmetrical guide holes are opened on both sides of the counterweight block, and two guide shafts with smaller diameters pass through the guide holes and are fixed to the motor; the center of the counterweight block has a pre-made internal thread, which forms a precision fit with the screw; when the motor rotates, the two guide shafts will drive the counterweight block to rotate on the fine-pitch screw; the fine-pitch screw converts the angular displacement of the counterweight block into axial linear displacement, causing the counterweight block to move along the torsional axis, thereby changing the center of mass distribution of the torsional block and completing a single adjustment of the center of mass position deviation.

[0068] The tilt angle calculation module obtains the tilt angle between the upper and lower base plates using h1 and h2. Specifically: Set the distance between the two measuring points of high-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 to L. Let the gaps on the high and low sides in the tilted state be h1 and h2 respectively. The tilt angle is calculated as follows:

[0069]

[0070] This allows for the accurate measurement of the tilt angle of the torsional pendulum.

[0071] The centroid position deviation calculation module calculates the deviation s between the centroid of the torsional yaw and the axis of rotation as follows:

[0072] When the center of mass of the torsional pendulum deviates from the axis of rotation, the pendulum will rotate under the torque generated by the gravitational component while in an inclined state. Let the total mass of the torsional pendulum be M, the pivot stiffness coefficient be k, and the distance of the center of mass from the axis of rotation be s. If the tilt angle of the upper base plate around the pivot increases... Afterwards, the rotation angle of the torsional pendulum changes to θ. Then, the mechanical equilibrium equation for the torque of the gravitational component and the restoring torque of the pivot is:

[0073]

[0074] Where g is the acceleration due to gravity, under the assumption of a small angle (cosθ = 1 when θ is sufficiently small), the deviation of the pendulum's center of mass from the axis of rotation can be obtained as follows:

[0075]

[0076] In this equation, θ is precisely measured using the angular displacement measurement function built into the torsion pendulum, k is obtained by calibrating the torsion pendulum, and M can be directly measured using a balance. Therefore, the key to calculating the deviation of the center of mass is to output axial displacement through the piezoelectric actuator, causing the upper base plate to generate a controllable tilt angle around the pivot.

[0077] A method for precise control of the center of mass of a micro-thrust measuring device, such as Figure 6 As shown, its characteristics include the following steps:

[0078] Step 1: Determine if the current centroid offset s falls within the fine-tuning range;

[0079] Step 2: The torsional tilt angle control module controls the torsional tilt angle. To take control;

[0080] Includes the following processes:

[0081] 1) The PID controller input receives the set tilt angle. and actual tilt angle

[0082] 2) Determine the set tilt angle and actual tilt angle Does a difference exist? If not, proceed to step 7); if yes, continue to step 3.

[0083] 3) The PID controller outputs voltage to the piezoelectric actuator. When the piezoelectric actuator outputs axial displacement, it causes the upper base plate of the double-base torsion base to tilt around the pivot at an angle.

[0084] 4) High-precision capacitive displacement sensor 1 and high-precision capacitive displacement sensor 2 feed back the h1 and h2 of their respective measuring point positions to the tilt angle calculation module of the controller;

[0085] 5) The tilt angle calculation module will calculate the actual tilt angle. Feedback is sent to the input of the PID controller;

[0086] 6) The PID controller adjusts the tilt angle set at the input terminal. and actual tilt angle Perform the difference calculation and return to process 2).

[0087] Step 3: The centroid position deviation calculation module calculates the centroid position offset.

[0088] Includes the following steps:

[0089] A. Establish the tilt angle generated by the piezoelectric actuator The relationship between the torsional gyroscope's rotation angle θ and the change in rotation angle θ.

[0090]

[0091] B. According to the above The relationship between θ and the given equation yields the deviation S of the torsional centroid from the axis of rotation.

[0092]

[0093] C. Send the deviation amount s to the centroid position adjustment module.

[0094] Step 4: Determine if the current centroid position offset s is less than 10um. If yes, complete the fine adjustment and proceed to step 6. If no, continue to step 5.

[0095] Step 5: The center of mass position adjustment module adjusts the center of mass position and returns to Step 2;

[0096] The specific steps are as follows:

[0097] 1) The controller's center of gravity position offset calculation module sends a drive command to the motor of the center of gravity position adjustment module based on the offset;

[0098] 2) When the motor rotates, the guide shaft will drive the mass block to rotate, completing a single adjustment of the center of mass position deviation;

[0099] Step Six: Fine-tuning complete.

[0100] 7) End.

Claims

1. A centroid adjustment device suitable for micro-thrust calibration of torsional pendulums, characterized in that, The precision centroid control device includes: a double-base torsion pendulum base installed inside a vacuum tank, the double-base torsion pendulum base having a support frame, a pivot, and a torsion pendulum, the support frame supporting the torsion pendulum via the pivot; a torsion pendulum tilt angle control mechanism installed on the drive side of the double-base torsion pendulum base; a centroid position adjustment mechanism installed on the double-base torsion pendulum base and connected to one end of the torsion pendulum; and a controller installed outside the vacuum tank, the controller's input terminals being connected to displacement sensors of the torsion pendulum and the torsion pendulum tilt angle control mechanism, and its output terminals being connected to the motor of the centroid position adjustment mechanism and the piezoelectric actuator of the torsion pendulum tilt angle control mechanism, respectively; the torsion pendulum tilt angle control mechanism is used to control the torsion pendulum tilt angle, the torsion pendulum tilt angle being the tilt angle of the torsion pendulum's cross-section along the direction of gravity; the centroid position adjustment mechanism is used to adjust the centroid position of the torsion pendulum; and the controller is used to control the torsion pendulum tilt angle control mechanism and the centroid position adjustment mechanism. The torsional tilt angle control mechanism includes: a piezoelectric actuator arranged on the driving side of the double-base plate torsional base, a pivot arranged on the rotational degree of freedom side of the double-base plate torsional base and connected to the upper and lower base plates of the double-base plate torsional base through the pivot, and a first high-precision capacitive displacement sensor and a second high-precision capacitive displacement sensor arranged on the base plate of the double-base plate torsional base and close to both ends of the upper base plate. The controller includes: a centroid position deviation calculation module for calculating the centroid deviation position of the torsional pendulum, a torsional pendulum tilt angle calculation module for calculating the torsional pendulum tilt angle, and a PID controller for controlling the torsional pendulum tilt angle.

2. The centroid adjustment device for micro-thrust calibration of torsional pendulum according to claim 1, characterized in that: The controller's center of mass position deviation calculation module is used to calculate the distance s of the center of mass deviating from the rotation axis. Its input terminals are connected to the torsion pendulum and the torsion pendulum tilt angle calculation module, respectively. The current rotation angle θ of the torsion pendulum is obtained from the torsion pendulum, and the actual torsion pendulum tilt angle is obtained from the torsion pendulum tilt angle calculation module. The output terminal is connected to the center of gravity position adjustment module, and the motor drive command is sent to the center of gravity position adjustment module; The controller's torsional tilt angle calculation module is used to calculate the actual torsional tilt angle. The input terminal of the centroid position deviation calculation module is connected to the first and second high-precision capacitive displacement sensors of the torsional tilt angle control mechanism. Through the measuring points h1 and h2 of the first and second high-precision capacitive displacement sensors, the actual torsional tilt angle between the upper and lower base plates of the double-base torsional base is obtained. The output of the torsional tilt angle calculation module is connected to a PID controller, and outputs the actual torsional tilt angle to the PID controller. h1 and h2 refer to the following: a first high-precision capacitive displacement sensor is positioned near the driving side of the double-base torsion base, and a second high-precision capacitive displacement sensor is positioned near the pivot. When the piezoelectric actuator outputs axial displacement, the first and second high-precision capacitive displacement sensors respectively measure the distances h1 and h2 between the upper and lower base plates. ； The PID controller of the controller is used to output commands for the axial displacement of the piezoelectric actuator; the input terminal of the torsional tilt angle calculation module is connected to the torsional tilt angle calculation module to obtain the actual torsional tilt angle. The PID controller and the controller's built-in yaw angle In comparison, the output of the PID controller is connected to the piezoelectric actuator of the torsion tilt angle control module, controlling the voltage output of the piezoelectric actuator to the upper plate of the double-base torsion tilt base.

3. The centroid adjustment device for micro-thrust calibration of torsional pendulum according to claim 1, characterized in that: The torsional tilt angle control mechanism includes: a piezoelectric actuator mounted on the drive side of the double-base plate torsional base; a pivot mounted on the rotational degree of freedom side of the double-base plate torsional base and connecting the upper and lower base plates via the pivot; and a first high-precision capacitive displacement sensor and a second high-precision capacitive displacement sensor mounted on the base plate of the double-base plate torsional base and near both ends of the upper base plate. The piezoelectric actuator acts as a displacement source; when it outputs an axial displacement voltage, it causes the upper base plate to generate an actual torsional tilt angle around the pivot. The first and second high-precision capacitive displacement sensors are symmetrically arranged at both ends of the double-base torsion base. The first high-precision capacitive displacement sensor is located at the end closer to the drive side, and the second high-precision capacitive displacement sensor is located at the end closer to the pivot. When the piezoelectric actuator outputs axial displacement, the first and second high-precision capacitive displacement sensors measure the distances h1 and h2 between the upper and lower base plates, respectively, and send h1 and h2 to the torsion calculation module of the controller. The torsion calculation module obtains the actual torsion angle between the upper and lower base plates using h1 and h2.

4. The centroid adjustment device for micro-thrust calibration of torsional pendulum according to claim 1, characterized in that: The center of mass position adjustment mechanism includes: a fine-pitch screw, a counterweight block, and a motor; the motor and the counterweight block are coaxial; one end of the fine-pitch screw is fixed to one side along the torsional axis and the torsional oscillation, and the other end passes through the central hole of the counterweight block and is threadedly connected to the central hole of the counterweight block; symmetrical guide holes are opened on both sides of the counterweight block, and two guide shafts with smaller diameters pass through the guide holes and are fixed to the motor; the center of the counterweight block has a pre-made internal thread, which forms a precision fit with the fine-pitch screw; when the motor rotates, the two guide shafts will drive the counterweight block to rotate on the fine-pitch screw; the fine-pitch screw converts the angular displacement of the counterweight block into axial linear displacement, causing the counterweight block to move along the torsional oscillation axis, thereby changing the center of mass distribution of the torsional oscillation and completing a single adjustment of the center of mass position deviation.

5. The centroid adjustment device for micro-thrust calibration of torsional pendulum according to claim 3, characterized in that: The torsional tilt angle calculation module obtains the actual torsional tilt angle between the upper and lower base plates through h1 and h2. Specifically: Set the distance between the two measuring points of the first high-precision capacitive displacement sensor and the second high-precision capacitive displacement sensor to L. Let the gaps on the high and low sides in the tilted state be h1 and h2, respectively. The formula for calculating the torsional tilt angle is: This allows for the accurate measurement of the torsional pendulum's tilt angle; h1 and h2 refer to: the first high-precision capacitive displacement sensor is placed at one end near the driving side of the double-base plate torsion base, and the second high-precision capacitive displacement sensor is placed at one end near the pivot; when the piezoelectric actuator outputs axial displacement, the first high-precision capacitive displacement sensor and the second high-precision capacitive displacement sensor respectively measure the distance h1 and h2 between the upper base plate and the lower base plate.

6. The centroid adjustment device for micro-thrust calibration of torsional pendulum according to claim 2, characterized in that: The distance s from the centroid to the axis of rotation is calculated as follows: When the center of mass of the torsional pendulum deviates from the axis of rotation, the pendulum will rotate under the torque generated by the gravitational component while in an inclined state. Let the total mass of the torsional pendulum be M, the pivot stiffness coefficient be k, and the distance of the center of mass from the axis of rotation be s. If the tilt angle of the upper base plate around the pivot increases... Afterwards, the rotation angle of the torsional pendulum changes to θ. Then, the mechanical equilibrium equation for the torque of the gravitational component and the restoring torque of the pivot is: Where g is the acceleration due to gravity, under the assumption of a small angle, i.e., when θ is sufficiently small, cosθ = 1, the deviation of the center of mass of the torsional pendulum from the axis of rotation can be obtained as: In this equation, θ is accurately measured by the angular displacement measurement function of the torsion pendulum, k is obtained by calibrating the torsion pendulum, and M can be directly measured by a balance.

7. A method for precise control of the center of mass of a micro-thrust measuring device, based on the center of mass control device for micro-thrust calibration torsion pendulum as described in any one of claims 1-6, characterized in that: Includes the following steps: Step 1: Determine if the current distance s from the axis of rotation to the center of mass falls within the fine-tuning range; Step 2: The torsional tilt angle control module controls the actual torsional tilt angle. To control the tilt angle; Step 3: The centroid position deviation calculation module calculates the distance s of the centroid deviation from the axis of rotation; Step 4: Determine whether the distance s between the current centroid and the rotation axis is less than 10um. If yes, complete the fine adjustment and proceed to step 6. If no, continue to step 5. Step 5: The center of mass position adjustment module adjusts the center of mass position and returns to Step 2; Step Six: Fine-tuning complete.

8. The method for center-of-mass adjustment of a torsional gyroscope suitable for micro-thrust calibration according to claim 7, characterized in that: The second step of controlling the torsional tilt angle includes the following process: 1) The PID controller input receives the set torsional tilt angle. and actual yaw angle 2) Determine the set torsional tilt angle and actual yaw angle Does a difference exist? If not, proceed to step 7); if yes, continue to step 3. 3) The PID controller outputs voltage to the piezoelectric actuator. When the piezoelectric actuator outputs axial displacement, it causes the upper base plate of the double-base torsion base to generate an actual torsion tilt angle around the pivot. 4) The first high-precision capacitive displacement sensor and the second high-precision capacitive displacement sensor feed back the h1 and h2 of their respective measuring point positions to the torsional tilt angle calculation module of the controller. 5) The torsional yaw angle calculation module will calculate the actual torsional yaw angle. Feedback is sent to the input of the PID controller; 6) The PID controller operates based on the set yaw angle at the input. and actual yaw angle Perform the difference calculation and return to process 2). 7) End.

9. The method for center-of-mass adjustment of a torsional gyroscope suitable for micro-thrust calibration according to claim 8, characterized in that: The calculation of the distance s between the center of mass and the axis of rotation in step three includes the following steps: A. Establish the actual torsional tilt angle generated by the piezoelectric actuator The relationship between the rotation angle θ of the torsional pendulum; B. Based on the actual torsional tilt angle The relationship between the change in the rotation angle θ of the torsional pendulum yields the distance s from the axis of rotation of the torsional pendulum's center of mass. C. Send the distance s of the centroid deviating from the axis of rotation to the centroid position adjustment module.

10. The method for center-of-mass adjustment of a torsional gyroscope for micro-thrust calibration according to claim 7, characterized in that: The centroid position adjustment module in step five adjusts the centroid position, and the specific steps are as follows: 1) The center of gravity position deviation calculation module of the controller sends a drive command to the motor of the center of gravity position adjustment module according to the deviation; 2) When the motor rotates, the guide shaft will drive the mass block to rotate, completing a single adjustment of the center of mass position deviation.

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