JP2005114492A - Active control pulse thrust measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse thrust measuring apparatus for suppressing the vibration of an apparatus system even if short pulse thrust operates, and precisely measuring the short pulse thrust. <P>SOLUTION: The pulse thrust measuring apparatus comprises: a thrust trestle 12 in which a thruster 2 for generating thrust is mounted; a support member 14 for supporting the thrust trestle so that it can travel in the thrust direction; a fixed member 16 fixed to the outside of the thrust trestle; a load detector 18 that is pinched between the fixed member and the thrust trestle for detecting a load operating between them; a displacement detection means 20 for detecting displacement (x) in the thrust direction of the thrust trestle; an actuator 22 for adding external force (u) in the thrust direction to the thrust trestle; and an active control unit 24 for controlling the external force (u) in the actuator according to the displacement (x), thus actively controlling the stiffness and/or attenuation characteristics of the thrust trestle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pulse thrust measurement device that measures thrust of a thruster that generates high-frequency pulse thrust, and more specifically, an active control pulse thrust having an active control system that suppresses high-frequency vibration of the device system generated by pulse thrust. It relates to a measuring device.

  For example, Patent Document 1 has been proposed to measure the thrust of a thruster used in space control, for example, for attitude control of an artificial satellite.

  As shown in FIG. 6, the “high-frequency pulse thrust measurement method and high-frequency pulse thrust measurement load cell” disclosed in Patent Document 1 has a longitudinal elastic modulus E such that the primary natural frequency f is greater than the frequency f ′ of the pulse thrust. And a block portion 52 having a length L in the thrust direction, and a strain gauge 54 inside or on the side of the block portion, and measuring a high-frequency pulse thrust by measuring strain generated in the block portion with the strain gauge. is there.

Japanese Patent Laid-Open No. 2002-202111

  A thruster used for artificial satellite attitude control or the like is required to confirm performance in a short pulse mode of 20 ms to 40 ms. Therefore, as shown schematically in FIG. 7, the conventional pulse thrust measuring device includes a gantry 61 that fixes the thruster 2 horizontally, a support body 62 that movably supports the gantry, and a gantry 61 and a support bracket. The load cell 64 is sandwiched between the load cell 64 and the thrust generated by the thruster is detected by the load cell.

  The pulse thrust measuring device having this configuration detects thrust generated by a thruster as a static force by a load cell. For this purpose, it is necessary to reduce the dynamic response by making the rigidity of the device system as large as possible and separating the pulse frequency and the natural frequency of the device system as much as possible. In a device manufactured under such conditions, the detected thrust should be in the shape of the original pulse and should give satisfactory results. Moreover, even if vibration is generated when a pulse is input, the vibration is attenuated in a very short time, so that there is no major problem in thrust measurement. In the unlikely event that a dynamic response of the device system occurs due to insufficient rigidity, it is conceivable to filter the obtained thrust waveform and remove the dynamic component, but when such processing is performed, There is a high possibility that the shape of the raw thrust waveform will be damaged, and it is considered that there is a problem in terms of reliability.

FIG. 8 is an example of a pulse thrust measurement result measured by the above-described pulse thrust measurement device. This example is a result of testing in a pulse mode of 0.02 sec (20 ms) with a period of 0.2 seconds, the horizontal axis is time, and the vertical axis is measured pulse thrust.
From this figure, it can be seen that in the measured pulse thrust, the thrust generated by the thruster (pulse thrust) is superimposed with a disturbance that seems to be due to insufficient rigidity of the device, and the pulse thrust cannot be measured.

  In order to measure the thrust with high accuracy, it is sufficient to increase the rigidity of the device system. This means that a more rigid load cell is selected. It becomes small and it becomes difficult to measure a thrust of about several tens of N. Therefore, a certain compromise must be established for rigidity. However, in recent years, highly responsive thrusters have been developed, and the natural frequency of the system tends to be close to the frequency of the thrust. Therefore, as described above, the vibration of the device system becomes obvious with respect to the short-time pulse, and there is a problem that it is difficult to obtain an accurate thrust waveform.

  The present invention has been developed to solve such problems. That is, an object of the present invention is to suppress vibration of the apparatus system even when a short-time pulse thrust of, for example, 20 ms to 40 ms is applied, and thereby to accurately measure a short-time pulse thrust. An object of the present invention is to provide a pulse thrust measuring device capable of performing the above.

  As in the conventional example described above, if the gantry is not sufficiently rigid and damped, vibration is generated in the apparatus system. As a result, the vibration is superimposed on the thrust waveform, and accurate thrust measurement cannot be performed. On the other hand, the present invention is intended to improve the measurement accuracy of the pulse thrust by incorporating a vibration suppression function in the measuring apparatus and measuring only the original thrust.

  That is, according to the present invention, a thrust base to which a thruster that generates thrust is attached, a support member that supports the thrust base to be movable in the thrust direction, a fixing member that is fixed to the outside of the thrust base, and a fixed A load detector that detects a load that is sandwiched between the member and the thrust mount and detects a load acting between them, a displacement detection means that detects displacement x in the thrust direction of the thrust mount, and an external force u in the thrust direction is added to the thrust mount An active control pulse thrust measuring device comprising an actuator and an active control device for controlling the external force u of the actuator in accordance with the displacement x, thereby actively controlling the rigidity and / or damping characteristics of the thrust mount Is provided.

  According to a preferred embodiment of the present invention, the actuator is a linear motor, a piezo actuator, or a giant magnetostrictive actuator.

  The actuator is a linear motor, and the active control device obtains a speed dx / dt from the displacement x, and a value Kv · dx / dt obtained by multiplying the speed dx / dt by a predetermined speed feedback gain Kv is used as the actuator thrust u. It is preferable to control in the direction opposite to the thrust.

  According to the configuration of the present invention, the displacement detecting means for detecting the displacement x in the thrust direction of the thrust mount, the actuator for adding the external force u in the thrust direction to the thrust mount, and controlling the external force u of the actuator according to the displacement x Active control device that can control the rigidity and / or damping characteristics of the thrust stand to improve the vibration characteristics of the device system to the desired characteristics, which were mixed in the thruster detection signal The vibration of the apparatus system can be suppressed, and thereby, a short-time pulse thrust can be accurately measured.

In addition, by adopting active control using an actuator, vibration control under vacuum conditions can be facilitated, and high-performance vibration characteristics can be realized by high-frequency fine vibration control.
Furthermore, since active control is used, the vibration characteristics can be changed only by changing the feedback gain as necessary, and a wide range of applications not limited to the installed thruster is possible.

In addition, since the displacement detecting means is provided, if this waveform is acquired, the thrust waveform can be inversely analyzed using a dynamic model, and can be used for verification of the detected thrust waveform.
Further, from the viewpoint of maintenance of the thrust measuring device, it is also possible to detect the damage or deterioration of the device at an early stage from the change in the vibration characteristics by exciting the thrust mount using the actuator as a vibration device.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram of an active control pulse thrust measuring device of the present invention. As shown in this figure, an active control pulse thrust measuring device 10 of the present invention includes a thrust base 12, a support member 14, a fixing member 16, a load detector 18, a displacement detection means 20, an actuator 22, and an active control device 24. .

  In this example, a thruster 2 that generates a thrust f is horizontally mounted on the thrust base 12. Further, in this example, the support member 14 is four thin plate springs arranged vertically, and supports the thrust mount 12 so as to be movable in the thrust direction (horizontal direction in this example). The fixing member 16 is fixed so as not to move to the outside of the thrust mount 12 (in this example, the foundation 4). The load detector 18 is, for example, a load cell, and is sandwiched between the fixed member 16 and the thrust mount 12 and detects a horizontal load acting therebetween.

In this example, the displacement detection means 20 is an eddy current sensor attached to the fixed member 16 (or the thrust base 12), and detects the displacement x in the thrust direction of the thrust base.
The actuator 22 is preferably a linear motor, and applies an external force u in the thrust direction to the thrust base 12. The actuator may be a piezo actuator or a giant magnetostrictive actuator instead of the linear motor.
The active control device 24 controls the external force u of the actuator in accordance with the detected displacement x by the displacement detecting means 20, thereby actively controlling the rigidity and / or damping characteristics of the thrust mount.

As described above, in the present invention, an actuator is incorporated in the measurement device to perform active vibration control. In the active control, a signal detected by a vibration sensor arranged on a thrust base of the apparatus is fed back, and a drive signal to an actuator is calculated by a controller. By applying this to the actuator, vibration is reduced. The drive signal by such feedback control is given by Expression (1) in (Formula 1) in the form of control force.
Here, fc is a control force, and Kd and Kv are feedback gains, respectively. The equation of motion of the device system to which such a control force is applied is expressed by equations (2) and (3) in (Equation 1).

Here, m _s , c _s , and k _s are the mass, damping coefficient, and rigidity of the device system before improvement, and f is the pulse thrust.
From the equation (3), it can be seen that the control force proportional to the speed contributes to the damping addition, and the control force proportional to the displacement contributes to the rigidity addition. In other words, the actuator can serve as both a spring element and a damper, and the vibration characteristic of the gantry can be improved to a desired characteristic by the feedback gain.

  FIG. 2 is a schematic diagram showing an arrangement example of actuators according to the present invention. In this figure, (a) is a parallel arrangement corresponding to FIG. 1, and (b) and (c) are a series arrangement.

As the most common actuator arrangement, the parallel arrangement of FIG. 1 and FIG. 2 (a) can be considered, but when the actuator is arranged in series with respect to the load cell as shown in FIG. 2 (b) (c), It is possible to add both damping and stiffness.
Of course, it goes without saying that the support bracket must be extremely rigid, but the detection force of the load cell and the force of the actuator are in an action-reaction relationship, so for example, a rigid piezoelectric element can be applied, Both high rigidity and damping addition can be realized. In addition, since such a piezoelectric element has a function as a sensor, it can be expected to substitute for a load cell, and if it is used as a self-sensing actuator, it does not use a thrust mount vibration sensor and load cell, but a smart structure using only a piezoelectric element Can be realized.

  FIG. 1 shows a configuration in which an actuator is arranged in parallel to the load cell shown in FIG. 2A. In the present invention, the actuator serves as a damper that can give only a damping force. A linear motor is used for the actuator 22 that performs vibration control, and this is installed between the lower part of the thrust base 12 and the foundation 4. In the linear motor, the upper and lower portions of the coil portion are sandwiched between magnet portions, and the coil portion is mounted on the thrust base 12 and one magnet portion is mounted on the foundation 4. When a current is passed through the coil, a thrust is generated in the vibration direction, and a required damping force can be applied to the thrust base. Since the coil part and the magnet part are not in contact with each other, there is no mechanical friction and minute vibrations can be efficiently reduced. A vibration sensor for detecting vibration is arranged on the thrust base. As the sensor, an eddy current type displacement sensor is used, but other displacement sensors and velocity sensors are also possible. Here, the feedback displacement signal is differentiated by the controller to obtain the speed. This is subjected to a control law based on equation (1) to obtain a driving force signal. This is input to a drive driver attached to the motor, and a current is supplied to the motor to control vibration.

  FIGS. 2B and 2C show an alternative structure of the parallel arrangement of FIGS. 1 and 2A. This is a case where the actuator is arranged in series with the load cell. There are two possible methods depending on whether the actuator is arranged on the thrust base side or the support bracket side. In this case, rigidity addition can be applied to the control force of Expression (1), and a piezoelectric element having a structurally high rigidity can also be applied.

FIG. 3 is a simulation result showing the influence of rigidity and damping ratio. In this figure, (A) shows the characteristics when the rigidity is changed to 0.5k, which is half of the standard 1.0k, and 2.0k, which is twice. (B) shows a case where the damping ratio is changed to 0.04, 0.1 and 0.4, and a case where the damping ratio is changed to 0.4 and the rigidity is changed to 2.0 k. In each figure, the horizontal axis represents frequency and the vertical axis represents static response magnification.
As shown in FIG. 3A, when the rigidity is reduced, the static response magnification is increased, so that the detection sensitivity can be improved. However, since the resonance point is lowered, vibration is easily superimposed. On the other hand, when the rigidity increases, the resonance point shifts to the high frequency side, so that it is less affected by the dynamic response, but the detection sensitivity decreases. Further, it can be seen that the characteristics in the high frequency range do not change regardless of the rigidity.
On the other hand, from FIG. 3B, when the damping ratio is increased, the resonance peak is reduced, but there is no significant change in a region outside the resonance peak. When the rigidity is increased and the damping is increased, the frequency range is broadened.
Therefore, it can be seen that by optimizing the rigidity and the damping ratio, the detection sensitivity is high and the superposition of vibration can be suppressed.

FIG. 4 is a characteristic diagram showing the effect of active control. In this figure, (A) shows the case without active control, and (B) shows the case with active control. From above, (a) input thrust, (b) control force, (c) displacement of the thrust base, (D) The detected thrust. In each figure, the horizontal axis is time.
From this figure, it can be seen that when active control is performed, the dynamic component due to vibration is reduced and the original waveform of the pulse thrust can be detected.

FIG. 5 shows the results of actual measurement of thruster thrust. In this figure, (A) shows the case without active control, and (B) shows the case with active control. The input thrust is on the lower side and the upper curve is the detected thrust in the figure, respectively. In each figure, the horizontal axis represents time, and the vertical axis represents thrust at different scales.
From this figure, it can be seen that even in an actual combustion test, when active control is performed, vibration is reduced and a good thrust waveform is obtained.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a block diagram of the active control pulse thrust measuring apparatus of this invention. It is a schematic diagram which shows the example of arrangement | positioning of the actuator by this invention. It is a simulation result which shows the influence of rigidity and damping ratio. It is a characteristic view which shows the effect of active control. It is the result of measuring thruster thrust. 10 is a schematic diagram of Patent Document 1. FIG. It is a schematic diagram of the conventional pulse thrust measuring device. It is an example of the pulse thrust measurement result measured with the conventional pulse thrust measuring device.

Explanation of symbols

2 thrusters, 4 basics,
10 Active control pulse thrust measuring device,
12 thrust mounts, 14 support members, 16 fixing members,
18 load detector (load cell), 20 displacement detection means (eddy current sensor),
22 Actuator (Linear Motor), 24 Active Control Device

Claims (3)

A thrust base to which a thruster that generates thrust is attached; a support member that supports the thrust base to be movable in a thrust direction; a fixing member that is fixed to the outside of the thrust base; and a fixing member and the thrust base. A load detector for detecting the load that is sandwiched and acting between them, a displacement detection means for detecting the displacement x in the thrust direction of the thrust mount, an actuator for adding an external force u in the thrust direction to the thrust mount, and the displacement x And an active control device for controlling the external force u of the actuator, thereby actively controlling the rigidity and / or damping characteristics of the thrust mount. The active control pulse thrust measuring device according to claim 1, wherein the actuator is a linear motor, a piezo actuator, or a giant magnetostrictive actuator. The actuator is a linear motor, and a speed dx / dt is obtained from the displacement x by the active control device, and a value Kv · dx / dt obtained by multiplying the speed dx / dt by a predetermined speed feedback gain Kv is used as a thrust u of the actuator. 2. The active control pulse thrust measuring device according to claim 1, wherein control is performed in the reverse direction.

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