CN216207186U - Naniu-level weak force calibration device - Google Patents
Naniu-level weak force calibration device Download PDFInfo
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- CN216207186U CN216207186U CN202122102687.8U CN202122102687U CN216207186U CN 216207186 U CN216207186 U CN 216207186U CN 202122102687 U CN202122102687 U CN 202122102687U CN 216207186 U CN216207186 U CN 216207186U
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Abstract
The utility model discloses a nano-Newton level weak force calibration device, which comprises a test bench frame, a rotating shaft, a swing arm, a displacement/angle sensor, a calibration arm and a calibration object, wherein the fixed part of the rotating shaft is fixedly connected with the test bench frame, the movable part of the rotating shaft is connected with the middle part of the swing arm, the swing arm can rotate around the rotating shaft in a vertical plane, the displacement/angle sensor measures the deflection angle of the swing arm, one end of the swing arm is provided with a propeller to be measured, the middle part of the calibration arm is fixedly connected with the middle part of the swing arm, the calibration arm is provided with a plurality of grooves, the calibration object is connected with a top ring through suspension wires, and the top ring is hung in the grooves.
Description
Technical Field
The utility model belongs to the technical field of space micro-thruster testing, and particularly relates to a nano-Newton level weak force calibration device.
Background
The resolution ratio has important application in high-precision space experiments in micro-Newton micro-propellers with higher precision. The precision requirement of the space task on the attitude control and the orbit control of the satellite is higher and higher, and a controlled actuator is a high-precision space micro-thruster which is a space task and an important component thereof, and the performance of the controlled actuator also determines the execution quality of the space task and even the success or failure of the space task. In the projects of high-precision deep space exploration, space small satellite formation flight, space gravitational wave exploration plan, space equivalent principle inspection, space microgravity vibration isolation and the like, a micro-thruster is also needed to compensate non-gravitational disturbance on a satellite or a local load in real time and carry out drag-free control.
Ground performance evaluation test and precision calibration are the necessary way for the development of the micro-thruster and are one of the preconditions for the space application of the micro-thruster. Common devices for ground evaluation are simple pendulum, inverted pendulum, torsional pendulum and the like, and the precision of the test tables can reach the magnitude of micro-Newton or even sub-micro-Newton. The measuring principle of the test bench is that a sensitive structure is deformed or displaced under the action of moment, and the magnitude of the moment can be calculated through measuring the displacement. However, due to assembly errors, material variations and various external factors, the rigidity of the system has errors with the theory. For accuracy of the results, calibration of the weak force measurement system using known forces/moments is required.
The french aerospace office started to develop a vertical torsional pendulum type micro-thrust test bench from 1999. The swing arm is hung on the frame by a knife edge, the gravity borne by the swing arm M acts on a mechanical sensitive structure, and the relative precision of the calibration method is 0.5%. To reduce mechanical stiffness, this solution also requires precise balancing to bring the swing arm centroid close to the axis of rotation.
The space propulsion laboratory of the Massachusetts institute of technology institute is a calibration system designed for a single pendulum type micro-thrust test bench. The weight is attached to a small diameter, lightweight string and the string is wound on a freely rotatable spool. The rope bends around the cylindrical rod, converting vertical gravity into horizontal tension. A weight hanging on the right side of the loop helps to create this tension, but a weight on the left side does not. This arrangement effectively changes the direction of gravity, but the friction between the string and the roller can cause errors.
In 2019, the university of china aerospace has designed a micro-thrust frame precision measuring device and measuring method based on gravity (CN 110307925B): a fixed frame lengthening frame is fixed on a fixed frame of a micro-thrust frame, a first measuring bracket is fixed on the fixed frame lengthening frame, a fixed pulley is fixed on the first measuring bracket, two ends of a rope wound on the circumference of the fixed pulley are respectively connected with a weight pan and a movable frame of the micro-thrust frame, and a weight with known mass is added into the weight pan to provide a known thrust for the movable frame, so that the measuring precision of the micro-thrust frame is determined. The disadvantage of this solution is that the friction of the pulley can introduce calibration errors and it is difficult to accurately evaluate the errors.
With respect to the calibration method of the test bench, ZL201920886848.7 gives a suspension ball calibration scheme, and the disadvantage of the scheme is that the real-time calibration cannot be realized. The methods are the same as the method in the scheme in terms of the source of the calibration force, and all come from gravity. The method of calibration by gravity is the scheme with the highest credibility at present.
In addition to the gravity/gravity torque calibration, the current common calibration methods include electrostatic force calibration and electromagnetic force calibration, and the corresponding representative structures include an electrostatic comb, an electromagnetic coil and the like. This type of approach has the advantage of being non-contact and producing minimal force. But the structure is more complex, the generated force is difficult to directly determine, secondary calibration is needed, and the method belongs to indirect measurement; but also introduces additional electromagnetic fields that increase coupling with the system, causing additional errors. The gravity method has simple structure, and generally only needs a heavy object with known mass to be loaded on the force arm. The gravity can be traced back to the universal gravitation, is the most accurate known force source at present, theoretically has no coupling effect with temperature, vibration and electromagnetic field, and has higher reliability; the method has the advantages of no need of introducing an electromagnetic field, simple operation and small unknown system error.
The currently common gravity calibration method uses wire suspension, which introduces additional effects; the calibration is carried out at the beginning and the end of the measurement, and the rigidity change in the measurement process of the system cannot be detected. The gravity suspension method adopts a translation table to drive a heavy object to move on a calibration arm with a notch, and the moment of gravity is changed by changing the arm of force of gravity. The calibration arm is provided with a notch groove, the micro-nano translation table is used for hanging a heavy object on the notch groove, and other parts of the system are not connected. Besides gravity calibration, the utility model can also be matched with a corresponding electromagnetic coil, and realizes real-time calibration in the measuring process by electromagnetic force. Meanwhile, the gravity moment can also calibrate the electromagnetic moment so as to ensure the accuracy of the result.
The disadvantages are as follows: in the prior art, (1) errors are caused by wires, friction and the like; (2) when the scheme such as electrostatic force, electromagnetic force and the like is used for calibration, the scale of the force needs to be weighed by using balance in advance, and the weighing process is inconsistent with the actual calibration working state, so that unknown system errors can be caused; (3) part of schemes can not realize real-time calibration; (4) the force arm of the thrust to be measured is difficult to accurately measure and is one of main error sources in the process of converting the moment into the force; (5) the calibration object changes the open-loop measurement state and introduces errors.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a nanonewton level weak force calibration device aiming at the defects in the prior art.
In order to achieve the purpose, the utility model adopts the following technical measures:
a Naniu-level weak force calibration device comprises a test table frame, a rotating shaft, a swing arm, a displacement/angle sensor, a calibration arm and a calibration object,
the fixed part of pivot links firmly with the testboard frame, the movable part of pivot links to each other with the swing arm middle part, the swing arm can revolute the rotation of axis of rotation in the vertical plane, displacement angle sensor measures the deflection angle of swing arm, swing arm one end is provided with remains to measure little propeller, the middle part of calibration arm links firmly with the middle part of swing arm, be provided with a plurality of recesses on the calibration arm, the calibration object passes through the suspension wire and is connected with the top ring, the top ring is hung in the recess, the test bench frame, the pivot, the swing arm, displacement angle sensor, the calibration arm, calibration object and little displacement adjustment mechanism all set up in the vacuum.
The utility model provides a receive ox level weak force calibration equipment, still includes the fine displacement adjustment mechanism that is used for hanging the top ring in the recess.
Compared with the prior art, the utility model has the following beneficial effects:
(1) the precision is high. No additional moment interference term exists; (2) the operation is convenient. The change of the moment can be remotely operated through the micro translation table without opening a vacuum cavity and replacing the calibration object; (3) the calibration range is wide. The calibration torque in two directions can be generated, the torque range is determined by the length of the calibration arm and the calibration object together, and the calibration interval is determined by the interval of the grooves; (4) the structure is simple, and the integration is convenient; (5) the application range is wide. The device can be suitable for equipment which needs standard force generation; (6) real-time calibration can be realized; (7) the relative thrust arm measurement method can be used for determining a thrust action point, a thrust direction and a rotating shaft position.
Drawings
Fig. 1 is a schematic diagram of a first calibration principle of the present invention.
Fig. 2 is a schematic diagram of a second calibration principle of the present invention.
In the figure: the method comprises the following steps of 1-a test table frame, 2-a rotating shaft, 3-a swing arm, 4-a displacement/angle sensor, 5-a micro propeller to be tested, 6-an electromagnetic force actuator, 7-a calibration arm, 8-a calibration object, 9-a micro displacement adjusting mechanism, 10-a groove, 11-a micro displacement table connecting piece and 12-a displacement sensor.
Detailed Description
The present invention will be described in further detail with reference to examples for the purpose of facilitating understanding and practice of the utility model by those of ordinary skill in the art, and it is to be understood that the present invention has been described in the illustrative embodiments and is not to be construed as limited thereto.
Example 1:
as shown in FIG. 1, a Naniu-level weak force calibration device is used for realizing high-precision real-time calibration of a horizontal axis pendulum type weak force test bench. The test table frame 1 is fixed on a test table top or is arranged in a vacuum container according to the working environment requirement of a tested object. The horizontal shaft swinging type weak force test bench comprises a rotating shaft 2, a swinging arm 3 and a displacement/angle sensor 4. Wherein the fixed part of pivot 2 links firmly with testboard frame 1, and the movable part of pivot 2 links to each other with swing arm 3, and swing arm 3 can be in the frictionless rotation in the plane perpendicular with pivot 2, and the balanced position of swing arm 3 is in vertical plane or horizontal plane usually. The probe part of the displacement/angle sensor 4 is fixed on the test table frame 1, and the displacement/angle sensor 4 is used for measuring the tiny displacement change of the swing arm 3 in real time. The weak force generating device to be measured, for example, the micro-thruster 5 to be measured is fixed at one end of the swing arm 3, and the thrust direction of the weak force generating device to be measured is vertical to the swing arm 3. When the micro-propeller 5 to be measured works, the swing arm 3 can change in the angle in the plane perpendicular to the rotating shaft 2, and the displacement/angle sensor 4 measures the change of the angle so as to measure the change of the thrust of the micro-propeller 5 to be measured. This is the open loop measurement mode of horizontal axis pendulum-type weak force testboard. (remark: description of configuration of the test bench and open-loop measurement mode)
In order to avoid as much as possible the disturbances related to displacement caused by the movement of the swing arm 3 during the measurement, the above-mentioned test bench also usually adopts a closed-loop measurement mode. A feedback force actuator is installed at the same end or the other end of the swing arm 3 and the micro-thruster 5 to be measured, for example, the feedback force actuator is an electromagnetic force actuator 6 as shown in fig. 1. A coil part of the electromagnetic force actuator 6 is installed on the other end of the swing arm 2 opposite to the micro-thruster 5 to be tested, and a permanent magnet part of the electromagnetic force actuator 6 is installed on the test bench frame 1. The electromagnetic force actuator 6 needs to have the capability of generating electromagnetic force of the order of micro newton or less. In the working mode, when the micro-propeller 5 to be measured works, the swing arm 3 deflects by the thrust of the micro-propeller, the deflection angle of the swing arm 3 relative to the balance position is measured by the displacement/angle sensor 4, and a feedback signal is sent to the feedback force actuator after control operation, so that the swing arm 3 is controlled at the original balance position. The feedback force of the electromagnetic force actuator 6 maintaining the position of the swing arm 3 at the equilibrium position is used to measure the thrust variation of the thruster 5.
In both the open-loop measurement mode and the closed-loop measurement mode, a constant or a proportionality coefficient related to the test environment variable and the thrust exists between the measured output signal and the micro-thrust to be measured. Under the working condition, the real-time and accurate calibration of the proportionality coefficient is a key link of the weak force test bench.
For measuring weak forceThe nano-Newton level real-time calibration system in the test process further comprises a calibration arm 7, a calibration object 8 and a micro-displacement adjusting mechanism 9, and when the balance position of the swing arm 3 is in a horizontal plane, the swing arm 3 can be used as the calibration arm 7. The calibration arm 7 is made of a low-expansion-coefficient material, the middle part of the calibration arm 7 is fixed with the middle part of the swing arm 3 and is in a horizontal state, and a V-shaped groove 10 is etched on the calibration arm. The calibration object 8 is connected with the top ring through the suspension wire, and the top ring is hung in the groove 10. The center of mass of the calibration object 8 is set at a position approximately equal to the height of the movable portion of the rotating shaft 2. The distance between the grooves 10 can be ensured by machining, and the consistency between the position where the top ring is suspended in each groove 10 and the design position of the groove 10 can be checked in advance with a high-precision three-coordinate measuring instrument. The frame assembled by the micro-displacement adjusting mechanism 9 is fixed on the testing table frame 1, and the adjusting part of the micro-displacement adjusting mechanism 9 is connected with the top ring of the calibration object 8 through the suspension wires by the micro-displacement table connecting piece 11. The calibration object 8 passes through the top ring and is lifted, translated and released in the other grooves 10 by the micro-displacement adjustment mechanism 9. The calibration object 8 and the groove 10 are in the same vertical plane under the action of gravity, so that the relative movement precision of the calibration object on the calibration arm 7 is ensured by the position of the groove 10, and the micro-displacement adjusting mechanism 9 is only used as a movement executing mechanism, and the precision, the temperature effect and the like of the micro-displacement adjusting mechanism do not influence the calibration precision. According to the test requirement, the test bench frame 1, the rotating shaft 2, the swing arm 3, the displacement/angle sensor 4, the calibration arm 7, the calibration object 8 and the micro-displacement adjusting mechanism 9 are all arranged in a vacuum container, and the pressure intensity is less than 10 under the action of a vacuum pump group-3Pa vacuum test environment.
The suspension wires and top ring may be made of fine wire or metal wire. The calibration mass m is the total mass of the suspension wire, the calibration object and the top ring, and needs to be accurately weighed before calibration. Before or after the calibration is started, the top ring is lifted by the micro-displacement adjusting mechanism 9, and the calibration object 10 is suspended in the air and is not contacted with the calibration arm 7.
As shown in fig. 2, in another embodiment of the present invention, the calibration object 8 is not suspended on the groove of the calibration arm 7 by a top ring, but the calibration object 8 is grabbed and placed in the groove of the calibration arm 7 by the micro-displacement adjusting mechanism 9, the displacement/angle sensor measures the deflection angle of the swing arm 3, and the displacement sensor 12 measures the distance of the displacement of the calibration object 8 on the calibration arm 7.
The working principle of the present invention can be represented by the following formula:
wherein, the same sign is identical sign, k is the system to be calibrated, FxRepresenting the thrust to be measured, Delta theta, of the micro-thruster 5 to be measuredxRepresenting the angular response caused by the thrust to be measured; the standard input force is generated by the gravity moment corresponding to the calibration mass; m is the calibration mass, g is the gravitational acceleration at the test position, Δ L is the movement distance of the calibration object 8 on the calibration arm 7, L is the distance of the propeller 5 from the movable part of the rotating shaft 2, and Δ θ is the difference between the deflection angles of the swing arm 3 measured twice by the displacement/angle sensor 4 compared with the initial equilibrium position.
Example 2:
a method for calibrating a Naniu-level weak force in real time based on a gravitational moment utilizes the Naniu-level weak force calibration device in embodiment 1, and comprises the following steps:
It should be noted that step 2 and step 3 are not divided in sequence, and can be performed sequentially or simultaneously, so as to realize real-time calibration of thrust.
(calibration error) consideration is given to the fact that the groove connecting line of the calibration arm 7 may have included angle error with the horizontal plane when being installed
The following can be obtained:
wherein
The error δ k of the calibrated force coefficient k to be measured can be expressed as:
wherein δ m, δ g, δ Δ L, δ Δ θ respectively represent the measurement accuracy of each physical quantity m, g, Δ L, Δ θ related to the calibration accuracy. The calibration mass m is calibrated in advance by a precision balance with the precision of microgram magnitude; the calibration arm 7 ensures that the deviation from the water level is within the required range in the working state by machining and measuring a level meter (
Within) when performing open loop calibration, due to the presence of delta theta in the operating state
May be larger and need to replace Δ l with Δ l' to correct the systematic error, when
The acceleration of gravity g may be determined using an absolute gravimeter. The thrust to be measured can be known as that the three error sources have small influence on the result, and the calibration method can easily achieve the micro Newton calibration precision. When reaching a nanonewton level, the thrust error is mainly affected by the change delta L of the gravity force arm of the calibrated mass and the precision of the thrust force arm L. The error in Δ l can be controlled on the order of microns by the method described above.
Example 3:
the method of determining the thrust arm is described below. Under the working state, the thrust action point of the micro propeller 5 to be tested is difficult to determine, the position of the rotating shaft 2 of the test bench cannot be accurately determined, and the accurate absolute measurement of the thrust force arm is a great problem.
Therefore, the present embodiment provides a method for measuring a thrust force arm, which utilizes the nanonewton-level weak force calibration apparatus described in embodiment 1: the propeller 5 to be measured is fixed at a preset position of the swing arm 2, and the rigidity coefficient K at the moment is calibrated by the calibration method and is defined as
K≡kL。 (3)
In the above formula, K is the stiffness coefficient, K is the calibration force coefficient, L is the distance between the propeller 5 and the movable part of the rotating shaft 2, and ≡ is the constant sign,
Then:
FxL＝KΔθ1x (4)
Fx(L±ΔL)＝K′Δθ2x (5)
therefore, the accurate calibration of the thrust force arm L is realized, and the thrust F to be measured is calibratedx。
The gravity moment calibration method for calibrating the mass can realize real-time calibration in the micro-thrust measurement process. When the thruster stably runs, the calibration arm is put into the calibration mass, and the swing arm deviates the angle; and moving the calibration mass again to enable the swing rod to deviate to a new position, and obtaining the calibration coefficient of the test bench and the belt thrust through the formula (1) through the change of the angle of the swing rod before and after moving and the change of the gravity moment of the calibration mass.
In the embodiment (1), traceable gravity is used as standard input; (2) the thrust arm is accurately measured by a thrust arm modulation method, and the contribution of the thrust arm error which is difficult to determine in the existing scheme is controlled in a nano Newton magnitude; and (3) the accuracy of the standard gravitational moment is ensured by using a grooving method for calibrating the change of the force arm, and the influence of a calibrated object on the state of the open-loop system is within an error control range. And finally, the real-time calibration precision of the nano Newton magnitude of the thrust is realized.
Alternative design (alternative) and other uses of example 1 of the utility model:
(1) the calibration object can be a sphere (or other geometric shapes) such as a square block or a steel ball; the groove 10 on the calibration arm is changed into an arc groove (or a groove with other shapes), and a square block or a steel ball is moved from one groove to the other groove through the micro-displacement adjusting mechanism 9 so as to realize the change of the moment;
(2) the calibration mode is not only suitable for horizontal shaft balancing pendulum, but also suitable for various systems needing to generate standard force or moment;
(3) the same purpose can be achieved by directly changing the mass of the calibration object without changing the arm of force of the calibration mass (for example, selecting different calibration objects or adding calibration objects on the existing calibration object).
(4) The displacement/angle sensor 4 may be a capacitive, laser interference, autocollimator or inductive measuring instrument, measuring distances with an accuracy of at least 10 nm.
Referring to fig. 2, the calibration object 8 is made into a regular geometric body such as a rectangular parallelepiped according to the required calibration mass, and is placed on the horizontal calibration arm 7, the calibration mass can be moved by the micro-displacement stage 9 along the calibration arm by a certain displacement under the operation of the micro-displacement stage connecting member 11, and the relative displacement is measured in real time by the displacement sensor 402 (for example, a measurement signal of a laser interferometer) without depending on the movement accuracy of the micro-displacement adjusting mechanism 9. The micro-displacement table 9 lifts the calibration object 8 before and after calibration, puts down the calibration object 8 in the calibration process, and the micro-displacement table connecting piece 11 does not contact the calibration object after moving to the set position. The above solution is another typical alternative similar to embodiment 1, and is used for determining the real-time accurate relative displacement of the calibration object 8 on the calibration arm 7 in real time, and the micrometer-scale precision is easily achieved.
It should be noted that the present invention can also be used in a weak closed-loop measurement process. At this time, the weak force measuring system is compensated by feedback control electromagnetic force, electrostatic force, etc., so that the swing arm 3 is always at the initial position. The calibration at this time will be a calibration of the feedback force coefficient, rather than the force coefficient calibration related to the swing arm 3 angle as described above. However, the technical points and the working method of the weak force real-time calibration system based on the gravitational moment are the same.
The foregoing detailed description is given for the sole purpose of illustration, and is not to be construed as limiting the scope of the utility model, as those skilled in the art will recognize that various modifications, additions and substitutions can be made to the detailed description without departing from the spirit of the utility model or exceeding the scope of the claims set forth below.
Claims (2)
1. A Naniu-level weak force calibration device comprises a test table frame (1), and is characterized by further comprising a rotating shaft (2), a swing arm (3), a displacement/angle sensor (4), a calibration arm (7) and a calibration object (8),
the fixed part of pivot (2) links firmly with test bench frame (1), the movable part of pivot (2) links to each other with swing arm (3) middle part, swing arm (3) can revolute pivot (2) internal rotation in the vertical plane, the deflection angle of swing arm (3) is measured in displacement angle sensor (4), swing arm (3) one end sets up and waits to survey micro-propeller (5), the middle part of calibration arm (7) links firmly with the middle part of swing arm (3), be provided with a plurality of recesses (10) on calibration arm (7), calibration object (8) are connected with the top ring through hanging wire, the top ring is hung in recess (10), test bench frame (1), pivot (2), swing arm (3), displacement angle sensor (4), calibration arm (7), calibration object (8) and micrometric displacement adjustment mechanism (9) all set up in the vacuum.
2. The Nanewton-grade weak force calibration device according to claim 1, further comprising a micro-displacement adjusting mechanism (9) for hanging the top ring in the groove (10).
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| CN117213714A (en) * | 2023-09-05 | 2023-12-12 | 国科大杭州高等研究院 | Torsion pendulum type micro-thrust measurement online calibration method |
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