JP6401598B2 - Active vibration isolator - Google Patents

Description

  The present invention relates to an active vibration isolation device that elastically supports a precision device that dislikes vibration, such as an electron microscope, with respect to a foundation and adds a control force to attenuate the vibration by an actuator.

  Patent Document 1 (pages 9-10, FIG. 6) describes a surface plate on which a vibration isolation object is placed, an elastic member that elastically supports the surface plate with respect to the foundation, and the vibration isolation object. An active vibration isolation device including an actuator group that applies control force to the surface plate is disclosed. In this active vibration isolator, the actuator group is composed of three pairs of actuators composed of two actuators whose action lines of control force extend in parallel to each other, and each actuator pair has an action vector of control force of an adjacent actuator. The horizontal components are arranged so as to have a difference of 120 degrees from each other.

JP 2012-47308 A

  However, in Patent Document 1, since the action lines of the control force of the three pairs of actuators are not orthogonal to each other, interference occurs between the control forces in the three directions of the three pairs of actuators, resulting in good vibration isolation performance. I can't get it.

  The present invention has been made in view of such a point, and an object of the present invention is when the actuator group is composed of three pairs of actuators including two actuators in which action lines of the control force extend parallel to each other. In addition, it is to obtain good control performance.

  In order to achieve the above object, the present invention is characterized in that three actuator pairs are arranged so that the action lines of control forces in three directions are orthogonal to each other.

  Specifically, the present invention provides a surface plate on which an object to be isolated is placed, an elastic member that elastically supports the surface plate with respect to the foundation, and the surface plate and the foundation. The following solution was taken for an active vibration isolation device including a vibration isolation object and an actuator group that applies control force to the surface plate.

  That is, in the first invention, the actuator group includes three pairs of actuators composed of two actuators in which the action lines of the control force extend in parallel with each other. The three translational axes corresponding to the actuator pairs are orthogonal to each other when an axis extending in parallel at an equal distance from both action lines on the same plane is defined as a translational axis.

  Thereby, since the action lines of the control forces of the three pairs of actuators are orthogonal to each other, no interference occurs between the control forces in the three directions of the three pairs of actuators, and good vibration isolation performance is obtained.

  Further, according to a second aspect of the present invention, in the active vibration isolation device of the first aspect, the three translational axes are orthogonal to each other at the gravity center position of the vibration isolation object and the surface plate, or vertically above the gravity center position. It is characterized by.

  As a result, when the three translation axes are orthogonal to each other at the center of gravity of the object to be vibration-isolated and the surface plate, the rotational direction is controlled by the control force in the translation axis direction generated by the two actuators constituting each actuator pair. Since the control force in the translation direction can be applied to the vibration isolation object and the surface plate without causing coupling to the vibration isolation performance, the vibration isolation performance is improved.

  Further, when the three translation axes are orthogonal to each other vertically above the gravity center position of the object to be vibration-isolated and the surface plate, vibrations vertically above the gravity center position can be effectively removed.

  According to a third aspect of the present invention, in the active vibration isolation device of the first or second aspect, the angles formed by the action lines of the control force of the actuators with respect to the mounting surface of the surface plate are equal to each other. Features.

  Generally, the vertical direction and the horizontal direction have different spring characteristics and the like, and the control characteristics are also different. However, since the contributions in the vertical direction and the horizontal direction are equal to each other by the six actuators, a circuit for controlling each actuator. It becomes easy to make the configuration of

  According to a fourth aspect of the present invention, in the active vibration isolation device according to any one of the first to third aspects, an acceleration sensor for detecting the acceleration of the surface plate on the action line of the control force of the actuator is further provided for each actuator. The control force applied to the vibration isolation object and the surface plate by each actuator is feedback-controlled based on the acceleration detected by the acceleration sensor, and corresponds to the action line of one actuator of each actuator pair. And the distance between the action line of the other actuator and the corresponding translation axis are equal to each other.

  As a result, the two actuators constituting each actuator pair are composed of the same kind of actuators, and the corresponding two acceleration sensors are also composed of the same kind of acceleration sensors so that both actuators can be controlled in common. It becomes easy.

  According to the active vibration isolator according to the present invention, it is possible to reduce costs and obtain good control performance.

It is a front view which shows schematic structure of the precision vibration isolator which concerns on embodiment of this invention. It is a side view which shows schematic structure of the precision vibration isolator which concerns on embodiment of this invention. It is the figure which looked at the foundation member, coil spring, and actuator from the upper part. It is the figure which looked at the surface plate, the actuator, and the controller from the lower part. It is an enlarged view which shows the actuator periphery. It is a block diagram which shows the feedback loop of control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show a precision vibration isolation table A which is an embodiment of an active vibration isolation device according to the present invention. The vibration isolation table A is a device on which a device 1 as a vibration isolation object that dislikes vibration is placed, such as a precision measurement device such as an electron microscope, an atomic force microscope, a semiconductor-related test device, or an inspection device. Therefore, it is assumed that the device 1 is mainly used for testing and research, and that the device 1 is replaced for the convenience of the user.

  As shown in FIGS. 3 and 4, the vibration isolation table A includes a rectangular plate-shaped base member 2 installed on the upper surface of a dedicated table or table (not shown) and four corners on the upper surface of the base member 2. Are respectively elastically supported on the base member 2 by the coil springs 3, 3,. And a surface plate 4 on which is mounted.

  The four coil springs 3, 3,... Are arranged on the base member 2 via height adjusting mechanisms 5, 5,. Even if the shared load applied to the springs 3, 3,... Changes, the distance between the upper surface of the base member 2 and the lower surface of the surface plate 4 can be kept approximately constant. 1 and 2, the coil springs 3, 3,... And the height adjusting mechanisms 5, 5,.

  Further, the coil springs 3, 3,... Are of unequal pitch, and have a characteristic that the spring constant increases in proportion to the increase in load due to the weight of the device 1. For this reason, even if the device 1 is changed and its weight is changed, the natural frequency of the spring system is kept substantially constant, and a high vibration isolation effect is obtained by active control described later regardless of the change of the device 1. Is obtained.

  Further, between the surface plate 4 and the base member 2, as shown in FIGS. 3 and 4, the six actuators 6 and 6 shown in FIG. Are arranged at intervals in the circumferential direction with respect to the center of the vibration isolation table A. These six actuators 6, 6,... Are provided with three pairs of actuators 6 and 6, each consisting of two actuators 6 and 6, in which action lines of the control force extend in parallel with each other. When the axes extending in parallel with the same distances D1, D2, D3 from the two action lines on the same plane as the action lines of the control force of the actuator pairs 6, 6 are defined as the translation axes X1, X2, X3, These three translation axes X1, X2, and X3 are orthogonal to each other at the gravity center position G of the device 1 and the surface plate 4. The angle formed by the action line of the control force of each actuator 6 with respect to the mounting surface of the surface plate 4 is set to an angle θ equal to or less than the same.

  That is, the six actuators 6, 6,... Are distances between the action lines of one actuator 6 of the actuator pairs 6, 6 and the corresponding translation axes X1, X2, and X3, and the action lines of the other actuator 6. And the corresponding translation axes X1, X2, X3 are arranged such that the distances D1, D2, D3 are equal to each other.

  A support member 7 that supports each actuator 6 is attached to the base member 2 so that the control force of each actuator 6 is obliquely upward. Each support member 7 is formed with a support surface 7a facing in the direction of the control force of the actuator 6 to be supported.

  A controller 8 for controlling the actuators 6, 6,... Is attached to the center of the lower surface of the surface plate 4.

  The six actuators 6, 6,... Are the same. As shown in FIG. 5, each actuator 6 has a cylindrical wall portion 6a fixed to the surface plate 4 via a bracket 9, and the cylindrical wall portion. A contact member 6b that protrudes from 6a and contacts the support surface 7a of the support member 7; A coil (not shown) for passing a current corresponding to a control signal input from the controller 8 and a magnet are disposed inside the cylindrical wall portion 6a, and the contact member is caused by the force generated by the coil and the magnet. 6b reciprocates. As the contact member 6b reciprocates in this way, a control force in a direction orthogonal to the support surface 7a is applied to the surface plate 4 and the device 1.

  Each actuator 6 is integrally provided with an acceleration sensor 10 via a bracket 9. From the acceleration sensor 10, a signal indicating the acceleration of the surface plate 4 in the direction in which the control force of the corresponding actuator 6 acts is output, and this signal is input to the controller 8. The acceleration indicated by the signal output here is the acceleration of the surface plate 4 on the line of action of the control force of the corresponding actuator 6.

  The controller 8 outputs a control signal to each actuator 6 based on signals input from the six acceleration sensors 10, 10,..., And a control force is applied to the surface plate 4 and the device 1 so as to reduce the vibration. Is done. That is, the vibration isolation table A of this embodiment is an active type in which feedback vibration control for reducing the vibration of the device 1 is performed.

  FIG. 6 is a block diagram showing a feedback loop for controlling each actuator 6 by the controller 8. In this embodiment, the detected value of the acceleration x ″ of the surface plate 4 is multiplied by the control gain Gm, and the acceleration x ″ is calculated. The speed x ′ integrated once is multiplied by the control gain Gc, and the displacement x obtained by integrating the acceleration x ″ twice is multiplied by the control gain Gk to obtain feedback correction values Gm · x ″ and Gc · x, respectively. ', Gk · x is calculated.

  The feedback correction values Gm · x ″, Gc · x ′, and Gk · x are added and then inverted to obtain a feedback control amount U (control signal) to the actuator 6. This control amount U is supported. The actuator 6 that is driven in response to the control signal to be applied applies a control force F to the device 1 and the surface plate 4 that are vibration control targets, thereby reducing vibration.

  The controller 8 also receives a signal from a sensor (not shown) that detects the height of the surface plate 4, and the controller 8 that receives this signal controls the height adjusting mechanisms 5, 5,. The lower end position is adjusted according to the elastic deformation of the coil springs 3, 3,... So that the height of the surface plate 4 is kept substantially constant.

  Therefore, according to the present embodiment, since the action lines of the control forces of the three pairs of actuators 6 and 6 are orthogonal to each other, no interference occurs between the control forces of the three pairs of actuators 6 and 6 in the three directions. Good vibration isolation performance can be obtained.

  Further, since only three actuator pairs 6 and 6 need be provided, the number of parts can be reduced and the cost can be reduced as compared with the case where eight actuators 6 are provided.

  In addition, when the control force in the translational axis direction is generated by the two actuators 6 and 6 constituting each actuator pair 6 and 6, the translational axes X1, X2, and X3 pass through positions shifted from the gravity center position G. Moment force is generated, and vibration is excited by this. In other words, vibration is coupled in the rotational direction by excitation in the translation direction. The coupled vibration in the rotational direction is reduced by the feedback control described above, but there is a risk of deteriorating the vibration isolation performance.

  On the other hand, according to the present embodiment, since the translation axes X1, X2, and X3 of any actuator pair 6 and 6 pass through the center of gravity position G, the two actuators 6 and 6 constituting each actuator pair 6 and 6 are used. With the generated control force in the translation axis direction, the control force in the translation direction can be applied to the device 1 and the surface plate 4 without causing coupling in the rotation direction. Therefore, the vibration isolation performance is improved.

  In general, the spring characteristics and the like of the elastic member are different between the vertical direction and the horizontal direction, so the control characteristics are also different. However, the angle formed by the control force action line of each actuator 6 with respect to the mounting surface of the surface plate 4 is different. Since the vertical and horizontal contributions are equal to each other in the six actuators 6, 6,..., The control characteristics of the six actuators 6, 6,. Therefore, the configuration of a circuit that controls each actuator 6 such as a low-pass filter can be shared.

  Further, the distance between the action line of one actuator 6 of each actuator pair 6, 6 and the corresponding translation axis X 1, X 2, X 3, and the translation axis X 1, X 2, X 3 corresponding to the action line of the other actuator 6 Are equal distances D1, D2 and D3, so that the two actuators 6 and 6 constituting each actuator pair 6 and 6 are composed of the same kind of actuators, and two acceleration sensors corresponding thereto 10 is also composed of the same kind of acceleration sensor, and the control gains Gm, Gc, Gk of both actuators 6 can be shared. That is, common control can be performed for both actuators 6 and 6.

  In the above embodiment, the three translation axes X1, X2, and X3 are orthogonal to each other at the center of gravity position G, but may be orthogonal to each other vertically above the center of gravity position G. As a result, vibrations vertically above the gravity center position G can be effectively removed. Therefore, this configuration is preferable when a high vibration isolation effect is required above the gravity center position G, such as when the device 1 is an electron microscope.

  Moreover, although the example which detects the acceleration of the surface plate 4 and feedback-controls the actuator 6 was shown in the said embodiment, not only this but vibration control is based on the vibration state of the base member 2. The vibration transmitted to 4 is estimated, the vibration isolation feedforward control for driving the actuator 6 so as to generate a control force that cancels this vibration, and the vibration associated with the operation of the device 1 are estimated by the warning signal, and this vibration A vibration suppression feedforward control that drives the actuator 6 so as to generate a control force that cancels the vibration is also possible.

  INDUSTRIAL APPLICABILITY The present invention is useful as an active vibration isolator in which, for example, a precision instrument that dislikes vibration, such as an electron microscope, is elastically supported with respect to the foundation and a control force that attenuates the vibration is applied by an actuator.

1 Equipment (objects for vibration isolation)
2 Foundation members (foundations)
4 Surface plate
6 Actuator
10 Acceleration sensor A Precision vibration isolation table (active vibration isolation device)
X1, X2, X3 Translation axis G Center of gravity position D1, D2, D3 Distance

Claims (4)

A surface plate on which an object to be isolated is placed;
An elastic member that elastically supports the surface plate with respect to the foundation;
An active vibration isolation device provided between the surface plate and a foundation and provided with the vibration isolation object and an actuator group for adding control force to the surface plate,
The actuator group includes three pairs of actuators composed of two actuators in which action lines of the control force extend in parallel with each other.
When the axes extending parallel to the action lines of the control force of each actuator pair on the same plane at an equal distance from the action lines are translation axes, the three translation axes corresponding to the actuator pairs are An active vibration isolator characterized by being orthogonal to each other. The active vibration isolator according to claim 1.
3. The active vibration isolation device, wherein the three translation axes are orthogonal to each other at a gravity center position of the vibration isolation object and the surface plate, or vertically above the gravity center position. In the active vibration isolator according to claim 1 or 2,
An active vibration isolator characterized in that the angle formed by the line of control force of each actuator with respect to the mounting surface of the surface plate is equal to each other. In the active vibration isolator according to any one of claims 1 to 3,
An acceleration sensor for detecting the acceleration of the surface plate on the line of action of the control force of the actuator is further provided for each actuator.
The control force applied to the vibration isolation object and the surface plate by each actuator is feedback controlled based on the acceleration detected by the acceleration sensor,
An active vibration isolation device, wherein a distance between an action line of one actuator of each actuator pair and a corresponding translation axis, and a distance between an action line of the other actuator and a corresponding translation axis are equal to each other.

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