JP4290049B2 - Parallel link device - Google Patents

Description

  The present invention relates to a parallel link device that realizes precise positioning.

Conventionally, a 6-degree-of-freedom parallel link mechanism that connects a fixed portion and a movable table by a link is disclosed. In these parallel link mechanisms, a capacitance displacement meter is fixed parallel to the expansion / contraction direction of the piezoelectric element, a target member is provided at the end of the piezoelectric element, and changes in the link stroke accompanying the expansion / contraction operation of the piezoelectric element are detected. A parallel link mechanism is disclosed (for example, Patent Document 1). In such a parallel link mechanism, there is also a type in which a displacement meter is provided in parallel with the X axis, the Y axis, and the Z axis so as to face the target surface of the movable table at the same time to monitor the attitude of the movable table.
JP-A-8-115128

  However, if a change in the link stroke is detected using the target member provided at the end of the piezoelectric element, the displacement of the piezoelectric element is detected instead of the link stroke that contributes to the displacement of the movable table. The loss that occurs until the displacement of the element is transmitted to the movable table is an error. If the posture of the movable table is controlled while correcting this error, the control becomes complicated.

  On the other hand, in recent years, a highly accurate attitude control is required for a positioning table (movable table) used in a semiconductor or liquid crystal manufacturing apparatus.

  The present invention has been made in earnest to solve such problems, and an object of the present invention is to provide a parallel link device that enables highly accurate positioning control.

  (1) In order to achieve the above object, the parallel link device of the present invention supports the movable table by a plurality of links displaceable in the axial direction, and displaces each link by driving an actuator to move the movable table. A parallel link device for controlling the attitude of the target device, wherein the displacement is transmitted to the target surface provided on the movable table and each link or each link so as to be substantially perpendicular to the axial direction of the link. A displacement sensor for detecting a distance to the target surface is provided on a sensor mounting portion of a fixed portion to which one end of the actuator is fixed so as to face the target surface.

  Thereby, the displacement of the link contributing to the movable table can be directly detected. As a result, the attitude of the movable table can be controlled accurately and easily without considering the displacement loss that occurs until the displacement of the actuator is transmitted to the movable table. In addition, since an error caused by the loss of displacement can be eliminated, a sensor for separately monitoring the attitude of the movable table can be eliminated.

  (2) Further, the parallel link device further includes a swing member coupled to the fixed portion via a hinge and swingable in a vertical plane, and the actuator is located at a position vertically below the hinge. The rocking member is pressed in a direction from the fixed portion toward the rocking member, and the link is separated from the rocking shaft of the rocking member by a distance from the rocking shaft of the rocking member. It is connected to the swing member so that the axis of the link intersects at a position on the swing member that is larger than the distance from the actuator to the pressed position, and the link is displaced by driving the actuator to move the link. It is preferable to control the attitude of the movable table.

  Thereby, the displacement of the actuator can be transmitted to the movable table while being enlarged, and the movable table can be greatly displaced. As a result, even when the external dimensions of the parallel link device cannot be changed, the stroke of the movable table can be enlarged. Further, the displacement speed of the movable table can be increased, and the attitude of the movable table can be controlled at high speed. In addition, by adjusting the shape of the swinging member, the angle between the pressing direction of the actuator to the swinging member and the direction of displacement of the link to the movable table can be arbitrarily set, and the device can be flexibly configured. Design can be done.

  (3) Moreover, it is preferable that a parallel link apparatus is further equipped with the elastic body which connects the said rocking | swiveling member and the said fixing | fixed part. Thereby, the swing member is pressed against the tip of the actuator, and the contact between the tip of the actuator and the swing member can be improved. As a result, the followability of the swing member with respect to the displacement of the actuator can be improved.

  (4) Further, in the parallel link device, it is preferable that the link includes at least a small-diameter portion whose side surface is recessed in a radial direction. Thereby, an inexpensive parallel link device that can perform smooth positioning can be realized. Further, the play portion on the mechanism can be omitted, and the rigidity in the displacement direction can be maintained.

  According to the parallel link device of the present invention, it is possible to directly detect the displacement of the link that contributes to the movable table. As a result, the attitude of the movable table can be controlled accurately and easily without considering the displacement loss that occurs until the displacement of the actuator is transmitted to the movable table. In addition, since an error caused by the loss of displacement can be eliminated, a sensor for separately monitoring the attitude of the movable table can be eliminated.

  Further, according to the parallel link device of the present invention, the displacement of the actuator can be transmitted to the movable table while being enlarged, and the movable table can be greatly displaced. As a result, even when the external dimensions of the parallel link device cannot be changed, the stroke of the movable table can be enlarged. Further, the displacement speed of the movable table can be increased, and the attitude of the movable table can be controlled at high speed. In addition, by adjusting the shape of the swinging member, the angle between the pressing direction of the actuator to the swinging member and the direction of displacement of the link to the movable table can be arbitrarily set, and the device can be flexibly configured. Design can be done.

  Further, according to the parallel link device of the present invention, the swing member is pressed against the tip of the actuator, and the contact between the tip of the actuator and the swing member can be improved. As a result, the followability of the swing member with respect to the displacement of the actuator can be improved.

  Further, according to the parallel link device of the present invention, an inexpensive parallel link device that can perform smooth positioning can be realized. Further, the play portion on the mechanism can be omitted, and the rigidity in the displacement direction can be maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, this is an exemplification of the embodiment, and the present invention is not limited to this embodiment. In addition, although a parallel link mechanism having 6 degrees of freedom will be described as an example here, 3 degrees of freedom may be used. In order to facilitate understanding of the description, the same reference numerals are assigned to the same components in the drawings, and duplicate descriptions are omitted.

  FIG. 1 is a side view of the parallel link device according to the present embodiment, and FIG. 2 is a plan view thereof. As shown in FIG. 1, the parallel link device 1 includes a fixed portion 10, a hinge 20, a swing member 30, an actuator 40, a preload spring 50, a link 60, a movable table 70, and a displacement sensor 80. Here, the fixing portion 10 includes a base portion 11, each actuator housing portion 12, and each sensor mounting portion 13, and is fixed so that the base portion 11 does not move to a fixed position. The fixed actuator storage portion 12 and the sensor mounting portion 13 fixed to the actuator storage portion 12 also do not move from a certain position.

  As shown in FIGS. 1 and 2, the parallel link device 1 has a configuration in which the displacement of the actuator 40 is expanded via the swing member 30 and transmitted to the link 60. Hereinafter, a portion constituted by the hinge 20, the swinging member 30, and the actuator 40 is collectively referred to as a displacement enlarging mechanism. Therefore, it may be considered that the parallel link device 1 is mainly configured by the fixed portion 10, the displacement enlarging mechanism, the link 60, and the movable table 70. First, the configuration of one of the six displacement magnifying mechanisms will be described.

  The hinge 20 is connected to the actuator housing portion 12 of the fixed portion 10 so that the swing member 30 can swing. The swing member 30 can swing in the vertical plane by the hinge 20. The shape of the rocking member is not particularly limited as long as it fulfills the above function.

  FIG. 3 is a view showing the periphery of the hinge 20 of the parallel link device 1. As shown in FIG. 3A, the hinge 20 connects the actuator storage portion 12 of the fixed portion 10 and the swing member 30 over the entire width direction of the actuator storage portion 12 of the fixed portion 10.

  The actuator housing portion 12 of the fixed portion 10 fixes one end of the actuator 40 so that the displacement of the actuator 40 is transmitted to the swing member 30. The other end of the actuator 40 is in contact with the surface of the swing member 30 so as to be pressed at a position vertically below the hinge 20. The actuator 40 is configured by, for example, a piezoelectric actuator, but is not particularly limited to a piezoelectric actuator as long as the displacement can be controlled. The hinge 20 is formed by cutting out an actuator housing portion 12 and a swinging member 30 that were originally an integral member, as shown in FIG. . In addition, it may replace with the hinge 20 shown in FIG.3 (b), and you may provide what functions as hinges, such as other hinge springs.

  The preload spring 50 as an elastic body is further vertically below the contact position of the actuator 40 and the swing member 30, one end connected to the actuator housing portion 12 of the fixed portion 10 and the other end connected to the swing member 30. ing. Similarly to the hinge 20, the preload spring 50 is formed by cutting out what was originally a member integral with the actuator housing portion 12 and the swing member 30 of the fixed portion 10 into the shape shown in FIG. 1. As shown in FIG. 3B, the preload spring 50 is shaped like a spell when viewed from the side. Moreover, as shown in FIG.3 (c), the preload spring 50 has a fixed width | variety. The preload spring 50 has a function of applying tension between the swing member 30 and the actuator housing portion 12 of the fixed portion 10 and pressing the swing member 30 against the actuator 40. Accordingly, the swing member 30 is always pressed against the tip of the actuator 40, and the contact between the tip of the actuator 40 and the swing member 30 can be improved. As a result, the followability of the swing member 30 with respect to the displacement of the actuator 40 can be improved. In addition, as long as it fulfill | performs the above functions, it may replace with the preload spring 50 as shown in FIG. 1, and may comprise a preload spring by connecting elastic bodies, such as a spring.

  When the preload spring 50 is present or not, the actuator 40 is vibrated at a constant frequency and the followability of the swing member 30 to the actuator 40 is tested. As a result, the resonance frequency of the preload spring 50 is improved. .

  FIG. 4 is a side view of the periphery of the swing member 30 of the parallel link device 1. As shown in FIG. 4, the swing member 30 has an inclined surface to which the link 60 is coupled. Here, A in the figure indicates a swing shaft with respect to the swing direction E of the swing member 30. D indicates the axis of the link, B indicates the point where the actuator 40 presses the swing member 30, and C indicates the intersection of the axis D of the link 60 and the inclined surface of the swing member 30. Show. The distance from the swing axis A to the intersection C is greater than the distance from the swing axis A to the pressing point B of the actuator 40. Here, the distance between the axis and the point means the shortest distance between the straight line as the axis and the point, and means the length of the line segment that is perpendicular to the axis from the point. In this way, when the actuator 40 presses the pressing point B, the lever principle works with the pivot axis A as a fulcrum, the pressing point B as a force point, and the connection point C as an action point, and the displacement of the actuator 40 is expanded. To the link 60.

  Thereby, the displacement of the actuator 40 is transmitted to the movable table 70 while being enlarged, and the movable table 70 can be greatly displaced. As a result, even when the external dimension of the parallel link device 1 cannot be changed, the stroke of the movable table 70 can be enlarged. Further, the displacement speed of the movable table 70 can be increased, and the attitude control of the movable table 70 can be performed at high speed. Further, by adjusting the shape or the like of the swing member 30, the angle formed between the pressing direction of the actuator 40 to the swing member 30 and the displacement direction of the link 60 to the movable table 70 can be arbitrarily set. The device can be designed flexibly.

  The enlargement ratio of the displacement of the link 60 relative to the displacement of the actuator 40 can be arbitrarily set by changing the distance AB or the distance AC. However, when the enlargement ratio is increased, the link 60 response and rigidity are reduced. Therefore, it is preferable to set it to about 1.5 to 2 times.

  Since the swing member 30 is provided with the inclined surface connected to the link 60 as described above, the displacement direction Q of the link 60 is an angle of about 120 degrees with respect to the pressing direction P of the actuator 40 shown in FIG. Is made. Thereby, the link 60 and the actuator 40 can be arranged so as to be folded. As a result, the parallel link device 1 having a small and simple structure can be realized. On the other hand, in a parallel link device of a certain size, it is possible to install a larger actuator 40 than in a configuration that does not use the swing member 30, increase the displacement amount and displacement speed of the movable table 70, and control the attitude of the movable table 70. Can be performed at high speed. Note that the displacement magnifying mechanism can optimize the angle formed by the displacement direction Q of the link 60 to the movable table 70 with respect to the pressing direction P of the actuator 40 to the swinging member 30 by the designed structure. In general, it is preferably 60 degrees or more and 120 degrees or less.

  One end of the link 60 is connected to the swing member 30 so that its axis is perpendicular to the inclined surface of the swing member 30. The other end is connected to the link attachment surface 71 of the movable table 70 and supports the movable table 70. By such a mechanism, the displacement of the actuator 40 is transmitted to the movable table 70, and the posture of the movable table 70 is controlled. The link 60 has a small-diameter portion 61 whose side surface is recessed in a portion close to the inclined surface of the swing member 30 and a portion close to the link attachment surface 71. As a result, it is possible to inexpensively configure a portion where stress is released by securing a degree of freedom in the other direction while maintaining the rigidity of the link 60 in the axial direction, instead of the universal joint or the pivot. Further, the play portion on the mechanism can be omitted, and the rigidity in the displacement direction can be maintained.

  FIG. 5 is a side view showing a modification of the small diameter portion of the link 60. The small-diameter portion 61 has a drum shape, but as shown in FIGS. 5A to 5C, the small-diameter portion 61 a constricted in a V shape is used as the first modified example, and the inclined is used as the second modified example. The small-diameter portion 61b having a shape having a portion and a constant diameter, or a small-diameter portion 61c having a shape having only a constant diameter as a third modification may be used. In addition, since it is necessary to maintain the rigidity of the link 60, the smallest diameter of the shape of the small diameter portion is about 5 to 25% with respect to the diameter of the link. For example, 1 to 5 mm is preferable for a link diameter of 20 mm. In addition, as a method of connecting the link 60 and the fixed portion 10, the link and the actuator are connected in a straight line without using the displacement enlargement mechanism using the swing member 30 and further connected to the fixed portion. However, the above effect can be obtained. Alternatively, one end of the actuator may be fixed to the movable table, the other end may be connected to the link, and the link may be connected to the fixed portion. The link may be connected between the link on the straight line by the actuator. The one end may be connected to the fixed portion and the other end may be connected to the movable table.

  The link attachment surface 71 of the movable table 70 is formed substantially perpendicular to the axis of the link 60, and the displacement sensor 80 is fixed to the sensor attachment portion 13 of the fixed portion 10 so as to face the link attachment surface 71. ing. The displacement sensor 80 has a function of detecting the distance to the link mounting surface 71 as a target surface and detecting the displacement of the link in real time.

  Thereby, the displacement of the link 60 contributing to the movable table 70 can be directly detected. As a result, the attitude of the movable table 70 can be controlled accurately and easily without considering the displacement loss that occurs until the displacement of the actuator 40 is transmitted to the movable table 70. Further, since an error caused by the loss of displacement can be eliminated, a sensor for separately monitoring the attitude of the movable table 70 can be eliminated.

  As the displacement sensor 80, for example, a capacitance measuring type is used, but a type using a laser or an ultrasonic wave may be used. Further, the target surface may be a surface perpendicular to the link axis, not the link mounting surface. Further, as a method of connecting the link and the fixed portion, a method of connecting the link and the actuator on a straight line and further connecting to the fixed portion without adopting the displacement enlarging mechanism using the swing member 30 may be used. The above effects can be obtained.

FIG. 6 is an example of an electrical block diagram of the parallel link device 1 using the PID control generally used as a control method. A command value with six degrees of freedom of X, Y, Z, θ _X , θ _Y , and θ _Z is input from the host 100 to the controller 101. In the controller 101, the inverse kinematics calculation unit 102 performs the inverse kinematics calculation on the input six-degree-of-freedom command values of X, Y, Z, θ _X , θ _Y , and θ _Z and requires each link 60. The displacement amount is calculated. This inverse kinematic calculation is a method for calculating the lengths of six links from the six-degree-of-freedom posture information of the movable table in a parallel link mechanism.

  Next, PID control parameters corresponding to the required displacement amount are applied in the PID calculation unit 103. Here, PID control is the most frequently used method among automatic control methods, and is finely controlled by combining three of Proportional, Integral, and Differential. Smooth control is possible.

  The output signal of the PID calculation unit 103 is amplified by the amplifier 104 and input to each piezoelectric actuator 40 in the parallel link mechanism 105. On the other hand, the displacement amount of the link 60 is detected by the displacement sensor 80, and the detection result is fed back. At this time, since the displacement of the link 60 that directly contributes to the movable table 70 is detected, it is not necessary to correct the error between the detection result and the actual displacement. The function of the control controller 101 is exhibited when the CPU executes a program using a memory.

Next, the operation of the parallel link device according to the present embodiment configured as described above will be described with reference to the flowchart shown in FIG. As described above, when command values of 6 degrees of freedom of X, Y, Z, θ _X , θ _Y , and θ _Z are input from the host 100, the controller 101 reads the command values (step S1). Next, inverse kinematics calculation is performed based on the command value, and the required displacement amount of each link 60 is calculated for each link (step S2). Next, the current position of each link is detected (step S3), the PID control parameter corresponding to the required displacement amount is read, and the actuator 40 is operated based on the required displacement amount and the PID control parameter corresponding to the required displacement amount. Each link 60 is displaced by driving (step S4). At this time, since the displacement of the link 60 that directly contributes to the movable table 70 is detected, there is no need to perform correction between the detection result and the actual displacement. Further, the displacement of the link 60 is expanded by the swing of the swing member 30 and transmitted to the link 60. Next, the difference from the current position of the link 60 to the displacement end position is calculated (step S5).

  Next, it is determined whether or not the difference calculated in step S5 is within a predetermined range for all links 60 (step S6). As a result of the determination, the difference is within the range. If not, the current position is held for the link 60 in which the difference calculated in step S5 falls within a predetermined range (step S7). In other words, the control is not necessarily performed until the difference becomes zero, but the control may be stopped when the difference falls within a certain allowable range.

  For the link 60 in which the difference calculated in step S5 is not within the predetermined range, a PID control parameter is determined corresponding to the difference from the position of the link 60 detected in step S4 to the displacement end position. The PID control parameter corresponding to the difference calculated in step S5 is read from the control parameter table (step S8). Then, the actuator 40 is driven based on the read PID control parameter and the difference calculated in step S5 to displace the link 60 (step S9).

  The above operation is repeated until the above differences in all links 60 fall within a certain range. That is, as a result of the determination in step S6, if the difference is within the range for all the links 60, the process is terminated (step S10).

It is a side view of the parallel link device concerning the present invention. It is a top view of the parallel link device concerning the present invention. (A) It is a top view which shows the periphery of the hinge and preload spring of the parallel link apparatus which concerns on this invention. (B) It is a side view which shows the periphery of the hinge and preload spring of the parallel link apparatus which concerns on this invention. (C) It is a bottom view which shows the periphery of the hinge and preload spring of the parallel link apparatus which concerns on this invention. It is a side view of the rocking | fluctuation member periphery of the parallel link apparatus which concerns on this invention. (A) It is a side view which shows the 1st modification of the small diameter part of a link. (B) It is a side view which shows the 2nd modification of the small diameter part of a link. (C) It is a side view which shows the 3rd modification of the small diameter part of a link. It is an electrical block block diagram of the parallel link apparatus using the PID control generally used as a control method. It is a flowchart which shows operation | movement of the parallel link apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Parallel link apparatus 10 Fixed part 11 Base part (fixed part)
12 Actuator storage (fixed part)
13 Sensor mounting part (fixed part)
30 Oscillating member 40 Actuator 50 Preload spring (elastic body)
60 link 61 small diameter part 70 movable table 71 link mounting surface (target surface)
80 Displacement sensor

Claims (4)

A parallel link device for controlling the attitude of the movable table,
A fixed part that does not displace;
A piezoelectric actuator having one end fixed to the fixing portion;
A link that is displaceable in an axial direction, one end of which is connected to the movable table, and that transmits displacement due to driving of the piezoelectric actuator to the movable table;
A displacement sensor that is provided in the fixed portion so as to face a link attachment surface to which the link on the movable table is connected, and detects a distance to the link attachment surface as a displacement amount of the link;
A parallel link device that enables high-accuracy positioning by controlling the attitude of the movable table by driving the piezoelectric actuator based on the detected displacement of the link. A swing member connected to the fixed portion via a hinge and capable of swinging in a vertical plane by being pressed by the piezoelectric actuator;
The link is at a position where the distance from the swing shaft is larger than the distance from the swing shaft of the swing member to the pressing position of the piezoelectric actuator, and the other end is connected to the swing member. The parallel link device according to claim 1, wherein:   The parallel link device according to claim 2, further comprising an elastic body that couples the swing member and the fixed portion. The parallel link device according to any one of claims 1 to 3, wherein the link includes at least a small-diameter portion whose side surface is recessed in a radial direction.

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