JP2003288122A - Guide device using ultrasonic motor as drive source for moving body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a guide device, capable of guiding a moving body with high position accuracy and positioning accuracy, while suppressing variations in a command value, when switching from a speed control to a position control even if an ultrasonic motor is used as a drive source for the moving body, where the guide device moves the moving body quickly by the speed control, until the vicinity of a final target position and positions precisely by the position control from the vicinity of the final target position until the final target position. <P>SOLUTION: A stage is driven by the speed control until the vicinity of the final target position while switching to the position control at the vicinity of the target position, and the command value, given at the switching time, is calculated by a proportional equation with a position deviation value in the execution of speed control and a position command value. The stage is driven by the position control until the target position after switching to the position control. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide device for positioning a movable body to a target position by using an ultrasonic motor as a drive source, and particularly to moving the movable body at high speed up to near the final target position. The present invention is suitable for a guide device that accurately positions from the vicinity of the final target position to the final target position.

[0002]

2. Description of the Related Art X conventionally used in semiconductor manufacturing equipment
On the Y stage, a method is used in which a table as a movable body is moved to a target position at high speed by speed control, and then the position control is performed to position the table at the target position.

Therefore, when both speed control and position control are used to move to a target position for positioning, it is necessary to switch from speed control to position control.

As a control method using both speed control and position control in this way, means for discovering control conditions by repeating trials by an operator, method for forming a double loop of speed control loop and position control loop, deviation A means for setting an initial value that minimizes a quadratic evaluation function for a signal and its differential signal has been proposed (see Japanese Patent Laid-Open No. 6-43940).

Further, as a target position determining method at each time after switching to the position control, there has been proposed a method of calculating a target position with a cubic function using an inverted value of the position deviation value as an initial value (Japanese Patent Application Laid-Open No. 2000-242242). See 2001-126424).

On the other hand, a DC motor or the like has been used as a means for driving a table such as an XY stage, but an ultrasonic motor is used as a drive source for the table from the viewpoint of enhancing the positional accuracy and the positioning accuracy during movement. Proposed to be used.

[0007]

However, when the ultrasonic motor is used as the drive source of the table, the contact state between the ultrasonic motor and the table is likely to change, so that stable movement and positioning of the table cannot be performed. However, in the method of finding the control condition by repeating the trial as described above, there is a problem that a worker constantly monitors and maintains a uniform driving state, which requires a lot of labor.

Further, in the method of forming the double loop of the speed control loop and the position control loop, the effect of speed control cannot be made zero when performing positioning, which causes an unstable condition and deteriorates the positioning accuracy. There were challenges.

Further, in the method of minimizing the quadratic evaluation function concerning the position deviation signal and its difference signal (differential signal),
Since the position command value is not managed, it is not possible to reduce the fluctuation of the command value that leads to deterioration of the life of the ultrasonic motor, and if the contact state between the movable body and the ultrasonic motor changes,
However, there is a problem that the target control state cannot be maintained.

Further, as a target position determining method at each time after switching to position control, a method of calculating a target position by a cubic function using an inverted value of a position deviation value as an initial value is
This is a method of responding with a cubic function so that the position deviation value when switching from speed control to position control becomes zero within a predetermined time. There is a problem that the target control state cannot be maintained when the contact state between the table and the ultrasonic motor changes, because the size cannot be reduced.

Therefore, even if each of the above-mentioned means is used as the control means of the guide device which uses the ultrasonic motor as the drive source of the table, the movement accuracy and the positioning accuracy of the table cannot be improved, and the precision machining machine, Precision measuring equipment,
There is a problem that it is difficult to use it for a guide device such as an exposure device used for a semiconductor manufacturing apparatus, which requires a movable body with high movement accuracy and positioning accuracy.

[0012]

In view of the above problems, the present invention has been made in view of the above problems, a movable body that is an object to be controlled, an ultrasonic motor that drives the movable body, and a position detector that measures the position of the movable body. And a deviation determination unit that calculates a position deviation that is the difference between the position information from the position detection unit and the target position at each time, a position deviation sent from the deviation determination unit, and the movement based on the speed control parameter. A speed control unit that outputs a command signal for moving the body to the vicinity of the final target position, a target position determination unit that determines the target position at each time based on the position deviation sent from the deviation determination unit, and the target position determination unit Based on the target position sent from the position control parameter, the position control unit that outputs a command signal to move the movable body that has moved to the vicinity of the final target position to the final target position based on the position control parameters, and switch the speed control to position control. Change switch, a movement data storage unit for storing a position deviation value and a command signal sent from the deviation determination unit at each time, and stored in the movement data storage unit at the time of switching from the speed control to the position control. A guide device that uses an ultrasonic motor as a drive source for a movable body, and an initial value setting unit that calculates an initial command signal for switching from a proportional expression of a position deviation value and a position command value to a position control during execution of speed control Is.

It is preferable that the speed control is switched to the position control within a range of 1% to 10% of the maximum moving speed of the movable body. Further, in the target position determining means, the speed control is changed to the position. It is preferable to calculate the target position at each time from the target position at the time of switching to the control to the final target position using a polynomial of third or higher order.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a top view showing an example of a guide device using an ultrasonic motor as a drive source of a movable body using a control device according to the present invention, and FIG. 2 is a block diagram of FIG. This guide device is provided with a pair of guide members 2 such as a cross roller guide 2 on a base board 1, and the stage 3 is linearly moved by these guide members 2.

A driving force transmitting member 4 is provided on one side surface of the stage 3, a linear scale 5 is provided on the other side surface of the stage 3, and a measuring head 6 is provided at a position facing the linear scale 5. And the friction member 8a of the ultrasonic motor 8 is brought into contact with the driving force transmission member 4 perpendicularly to the longitudinal direction of the driving force transmission member 4. The controller 10 calculates based on the position information of No. 3, and the ultrasonic motor 8
The friction member 8a of the ultrasonic motor 8 is moved according to the command signal by performing feedback control to output a command voltage value to the friction member 8a of the ultrasonic motor 8 and the driving force transmission member 4 of the stage 3. The stage 3 is moved along the guide member 2 by the frictional driving of.

The control device 10 positions the movable body based on a speed control parameter and a deviation determining unit 11 which determines a position deviation value which is a difference between the detection result of the position detector 7 and the target position at each time. The command value is output until the speed reaches 10% or less of the maximum moving speed that is a speed that can ensure the moving distance that satisfies the accuracy, and the speed control unit 12 that drives the ultrasonic motor 8 and the stage 3 are moved to the final target position. Target position determination unit 13 that calculates the target position at each time when
Based on the position control parameters, the stage 3 outputs a command value to the final target position to drive the ultrasonic motor 8, a position controller 14 for switching between speed control and position control, and a switch 17 for executing speed control. From the movement data storage unit 15 that stores the position deviation value and the command value at time, and from the proportional expression of the position deviation value and the command value that are stored in the movement data storage unit 15 when switching from speed control to position control, When the PI control is used as the control means in the speed control unit 12, the position control switching initial value is calculated from the position deviation value to determine the initial command value.
When the P term and I term are used as the control parameters and the PID control is used as the control means in the position control unit 14, the P term, the I term and the D term may be used as the control parameters. Here, the P term means proportional, the I term means integral, and the D term means differential action.

As the information calculated by the target position determining unit 13, the target position at the time of switching from the speed control to the position control to the final target position is calculated by a polynomial of third or higher order and the target position at each time of the stage 3 is calculated. Calculate

The information calculated by the initial value setting unit 16 is
The position deviation value and the command value stored in the movement data storage unit 15 are calculated by the initial value setting unit 16 from the position deviation value and the command value to the minimum value X _min , the maximum value X _max and the minimum value of the position deviation. And a command value Y2 at the maximum value of the position deviation, the following calculation formula Y = AX + B formula X, Y
To obtain the value B when the slopes A and X are zero, derive the proportional expression of the position deviation value and the command value, and substitute the position deviation value when switching from speed control to position control into the proportional expression It is designed to calculate the value.

Next, the control procedure when the guide device shown in FIGS. 1 and 2 is driven will be described with reference to the flow chart of FIG.

First, the deviation determining unit 11 calculates an ideal curve to determine the ideal of the stage 3 at each time, and then the switch 17 of the switch 17 is set to 1.

The position detector 7 for detecting the position of the stage 3 detects the position of the stage 3 to detect the deviation.
1, the position deviation is calculated from the ideal position at each time and the input operation position of the stage 3.

First, in # 1, since Switch is set to 1, the process routine proceeds to # 2, in which the speed control unit 12 calculates the ideal position and the position deviation calculated by the deviation determining unit 11. The ideal speed and the speed deviation are calculated, and the speed deviation is calculated based on the following calculation formula Vn = KnPv + ΣKnIv to determine the command value.

Vn is a command value at each time, Kn is a speed deviation value at each time, Pv is P in speed control.
The term, Iv, is the I term in speed control.

Next, in # 3, when the moving speed enters the deceleration region and the ideal speed becomes 1% to 10% of the maximum speed,
Switch is set to 2 and the movement command value is output to the ultrasonic motor 8.

Here, the switching from the speed control to the position control is performed within the range of 1% to 10% of the maximum speed of the stage 3 so that the speed control is performed when the speed becomes less than 1% of the maximum speed of the stage 3. This is because if the switching to the position control is performed, there is an inconvenience that the positioning is not completed within the time when the final target position is reached, and the maximum speed of the stage 3 is 10%.
If you switch from speed control to position control earlier,
This is because there is an inconvenience that the fluctuation of the command value is large.

Then, the position deviation recorded in the deviation determination unit 11 and the command value recorded in the speed control unit 12 are output to and stored in the movement data storage unit 15.

After setting Switch to 2 in the speed control unit 12, the control loop moves to # 4 and proceeds to # 5, and the initial value setting unit 16 stores the data in the movement data storage unit 15. Inputting the position deviation and the command value, the minimum value X _min and the maximum value X _{max of} the position deviation, and the command value Y1 at the minimum value X _min of the position deviation and the command value Y at the maximum value X _max of the position deviation.
Substituting X and Y of the following calculation formula “Y = AX + B formula” based on 2 to obtain the slope A and the contact piece B, determine the command value, and Sw.
Set it to 3.

Proceeding to step # 6, the target position determining unit 13 calculates the ideal position at each time in position control from the target position at the time of switching to the final target position by the following formula "Xr = A1 (t
-Tr) ³ + Xend "to calculate the target position in each sampling cycle.

[0030] To where the slope A1 is to match the slope a _tc the slope immediately before switching in contact switched from speed control to position control, the following formula _{"a tc = 3A1 (t-Tr} ) 2 "
Performs calculation based on, the final target position arrival time Tr performs calculation based on the following formula "Tr = Tc + 3 (Xend- Xc) / a tc ".

Xr is the target position at each time in position control, A1 is the inclination, t is the sampling time, Tr is the time to reach the final target position, Xend is the final target position, and Tc is the speed control to the position control. And Xc represents the target position at the time when the speed control is switched to the position control.

Since Switch is set to 3, the process proceeds to # 7 and proceeds to # 8, and the ideal position at each time point calculated by the target position determination unit 13 by the position control unit 14 is set to the ideal position of the stage 3. The position deviation is calculated from the operation position input from the position detector 7 that has detected the operation position, and then the calculation is performed based on the calculation formula "Vn = EnPx + ΣEnIx + (En-En-1) Dx" to determine the command value. And ultrasonic motor 8
Output to.

Vn is a command value at each time, Kn is a speed deviation value at each time, Pv is P in speed control.
The term, Iv is the I term in the speed control, En is the position deviation value at each time, En-1 is the position deviation at the sampling immediately before En, Px is the P term in the position control, and Ix is the I term in the position control. Is.

Then, if Switch is set to 3 in # 9 and the stage 3 reaches the final target position, the control loop is exited and the control is terminated.

As described above, when the speed control is switched to the position control, the load on the ultrasonic motor 8 is increased because the proportional expression of the position deviation and the command value and the ideal position are calculated by a polynomial of third order or more. It can be controlled to a minimum.

Therefore, when the guide device of the present invention is used, the moving accuracy and the positioning accuracy of the stage 3 can be improved, the stage 3 can be smoothly moved at high speed to the vicinity of the final target position, and the switching in the vicinity of the final target position can be performed. Can be performed smoothly, and can be accurately positioned at the final target position, so that high precision and positioning accuracy can be achieved on movable objects such as precision processing machines, precision measuring equipment, and exposure equipment used in semiconductor manufacturing equipment. It can also be suitably used for a guide device that is required.

[0037]

EXAMPLES Specific examples of the present invention will be described below.

A guide device using the ultrasonic motor shown in FIG. 1 as a drive source for a movable body was prototyped, and the control device 10 of the present invention and a conventional control device were incorporated into this guide device, and two stages 3 were provided.
An experiment was performed to confirm the state characteristics of positioning from the running test in which the total movement distance is moved 10 km in steps of 5 mm, and the drive characteristics of the stage 3 from the wear state of the friction member 8a of the ultrasonic motor 8.

In this experiment, a cross roller guide having a stroke of 100 mm was used as the guide member 2 constituting the guide device, and the guide member 2 was used to move the stage 3 as a movable body having a weight of 5 kg. did. A drive transmission member 4 made of alumina ceramic is arranged on one side surface of the stage 3. Further, the friction member 8a of the ultrasonic motor 8 frictionally driven with the driving force transmission member 4
For this, alumina ceramics was used.

Further, in the guide device using the control device 10 of the present invention, the ultrasonic motor 8 is controlled to match the target speed at each time when the speed control of the stage 3 is executed and the target position at each time when the position control is executed. So that the speed controller 1
2 is for comparing the target speed with the operating speed calculated by the deviation determining unit 11 from the actual operating position detected by the position detecting hand 7 based on the preset acceleration and maximum speed of the ultrasonic motor 8. The velocity deviation was calculated for each sampling cycle set to.

Further, the position control unit 14 is the target position determination unit 1
The position deviation of the target position calculated in 3 and the actual operating position detected by the position detector 7 was calculated for each sampling cycle.

Here, when the command value at each time is obtained, the following calculation formula Vn = KnP is executed when the speed control is executed.
Calculation is performed based on v + ΣKnIv, and at the time of executing position control, the following calculation formula Vn = EnPx + ΣEnIx +
Calculation was performed based on (En-En-1) Dx, and the result was output as a command value to drive the ultrasonic motor 8.

Note that Vn is a command value at each time, Kn is a speed deviation value at each time, and Pv is P in speed control.
The term, Iv is the I term in the speed control, En is the position deviation value at each time, En-1 is the position deviation at the sampling immediately before En, Px is the P term in the position control, and Ix is the I term in the position control. Is.

Specifically, at the time of execution of speed control, first, after outputting a command value from the speed control unit 12 shown in FIG. 2 to the ultrasonic motor 8, the command value and the position deviation value at that time are stored. Recorded in part 15.

Next, FIG. 4 shows a characteristic diagram of the command value and the position deviation value stored in the movement data storage unit 15 as the initial setting value after switching from the speed control to the position control, and the following calculation formula "Y = AX + B" is used. Substituting the minimum value Y1 and the maximum value Y2 of the command value into Y, and the minimum value X _min and the maximum value X _max of the position deviation value into X, and calculating the inclination A and the contact B in the initial value setting unit 16. Then, a command value is calculated from the position deviation value at the time of switching the position control and output to the ultrasonic motor 8.

Next, as shown in FIG. 5, the target position determining unit 13 determines the final target position from the target position at the time of switching based on the following calculation formula "Xr = A1 (t-Tr) ³ + Xend". The target position in the cycle was calculated.

[0047] Here, since the slope A1 is to match the slope a _tc the slope immediately before switching in contact switched from speed control to position control, the following formula "a _tc = 3A1 (t-T
r) ² ”to calculate the final target position arrival time T
r The following formula "Tr = Tc + 3 (Xend- Xc) / a tc "
Calculate based on.

Xr is the target position at each time in position control, A1 is the inclination, t is the sampling time, Tr is the time to reach the final target position, Xend is the final target position, and Tc is the speed control to the position control. At the time, Xc is the target position at the time when the speed control is switched to the position control.

A position deviation value is calculated based on the target position at each time calculated by the target position determining unit 13 and the actual operating position from the position detector 7, and a command value is calculated by the position control unit 14 to calculate the command value. The sound wave motor 8 is used for output.

As a conventional control device, a method of switching between speed control and position control based on a control parameter set by an operator, and an initial value that minimizes a quadratic evaluation function regarding a deviation signal and its difference signal are set. The control device using the method described above is used.

As a result, FIG. 6 shows command values when the ultrasonic motor 8 mounted on the guide device using the control device 10 of the present invention is driven, and the ultrasonic wave mounted on the guide device using the conventional control device is shown in FIG. FIG. 7 shows command values when the motor 8 is driven.

Further, Table 1 shows the positioning time at the time of 25 mm step movement in the guide device using the control device 10 of the present invention and 25 in the guide device using the conventional control device.
The positioning time at the time of the mm step movement is extracted and confirmed during the total movement distance of 10 km.

As shown in FIG. 7, in the conventional guide device, the command value fluctuates at the time Tc at which the speed control is switched to the position control. As a result, FIG. 9 shows the surface condition of the contact surface before driving the ultrasonic motor 8, and FIG. 11 shows the surface condition of the contact surface after driving the ultrasonic motor 8 mounted on the conventional guide device. As described above, the contact surface was considerably rough and was abnormally worn.

On the other hand, in the guide device of the present invention, as shown in FIG. 6, the switching time T from the speed control to the position control is changed.
It can be seen that there is no change in the command value even at c, and smooth switching is possible. As a result, FIG. 9 shows the surface condition of the contact surface before driving the ultrasonic motor 8, and FIG. 10 shows the surface condition of the contact surface after driving the ultrasonic motor 8 mounted on the guide device of the present invention. As shown in the figure, although the contact surface was worn, it was worn uniformly over the entire surface and no abnormal wear was found.

As another conventional guide device, a guide device using a method of setting an initial value that minimizes a quadratic evaluation function concerning the deviation signal and its difference signal is also prepared in the control device.
When the variation of the command value at the time Tc at which the speed control is switched to the position control is examined, the variation of the command value is found at the time Tc as shown in FIG. It was not possible to switch.

Thus, it can be seen that a stable driving state can be maintained during the driving of the stage 3 by using the guide device provided with the control device 10 of the present invention.

[0057]

[Table 1]

[0058]

As described above, according to the present invention, a movable body which is an object to be controlled, an ultrasonic motor for driving the movable body, a position detecting section for measuring the position of the movable body, and A deviation determination unit that calculates a position deviation that is the difference between the position information from the position detection unit and the target position at a time, a position deviation sent from the deviation determination unit, and the movable body based on the speed control parameter. A speed control unit that outputs a command signal to move to the vicinity of the target position, a target position determination unit that determines a target position at each time based on the position deviation sent from the deviation determination unit, and a target position determination unit Based on the target position, the position control unit that outputs a command signal to move the movable body that has moved near the final target position to the final target position based on the position control parameters, and a switching switch that switches the speed control to the position control. Switch, a movement data storage unit that stores a position deviation value and a command signal at each time sent from the deviation determination unit, and a speed that is stored in the movement data storage unit when switching from the speed control to the position control. A guide device using an ultrasonic motor as a drive source of a movable body is configured from an initial value setting unit that calculates an initial command signal for switching from a proportional expression of a position deviation value and a position command value to a position control during control execution. Therefore, since the command signal does not fluctuate when switching from speed control to position control, the ultrasonic motor, which is difficult to control, is the drive source of the movable body, but the movable body does not deteriorate in position accuracy. Can be smoothly moved at high speed, and the movable body can be accurately positioned with respect to the final target position.

Particularly, by switching from the speed control to the position control within 1% to 10% of the maximum moving speed of the movable body, the fluctuation of the command value can be minimized, and Positioning can be completed when the target position is reached, which is more preferable.

Further, the target position determining means calculates the target position at each time from the target position at the time of switching from the speed control to the position control to the final target position by using a polynomial of third order or higher. It is more preferable that the ideal curve can be freely changed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a guide device of the present invention using an ultrasonic motor as a drive source.

FIG. 2 is a block diagram showing a control unit provided in the guide device of the present invention.

FIG. 3 is a flowchart showing the operation of the guide device of the present invention.

FIG. 4 is a diagram showing a relationship between a position deviation and a command value.

FIG. 5 is a diagram showing a relationship between time and a target position in position control.

FIG. 6 is a diagram showing a relationship between time and a command value of the guide device of the present invention in an experiment.

FIG. 7 is a diagram showing a relationship between time and a command value of a conventional guide device in an experiment.

FIG. 8 is a diagram showing a relationship between time and a command value of a conventional guide device using a method of setting an initial value that minimizes a quadratic evaluation function regarding a deviation signal and its difference signal in an experiment.

FIG. 9 is a diagram showing a surface roughness on a contact surface of a friction member included in the ultrasonic motor before the experiment.

FIG. 10 is a diagram showing the surface roughness on the contact surface of the friction member provided in the ultrasonic motor after the experiment using the guide device of the present invention.

FIG. 11 is a diagram showing the surface roughness on the contact surface of the friction member provided in the ultrasonic motor after the experiment using the conventional guide device.

[Explanation of symbols]

1: Base board 2: Guide member 3: Stage 4: Driving force transmission member 5: Linear scale 6: Length measuring head 7: Position detecting hand 8: Ultrasonic motor 8a: Friction member 10: Control device 11: Deviation determination unit
12: Speed control unit 13: Target position determination unit 14: Position control unit 15: Movement data storage unit 16: Initial value setting unit 17: Switch 21: Minimum value of position deviation and command value stored in movement data storage unit 22: Maximum value of position deviation and command value stored in movement data storage 23: Time when switching from speed control to position control 24: Target position at time when switching from speed control to position control 25: To final target position Time to arrive 26: Final target position

Claims (3)

[Claims] 1. A movable body which is an object to be controlled, an ultrasonic motor which drives the movable body, a position detector which measures the position of the movable body, and position information from the position detector at each time. A deviation determining unit that calculates a position deviation that is a difference from the target position, a position deviation sent from the deviation determining unit, and a command signal that moves the movable body to the vicinity of the final target position based on the speed control parameter are output. A speed control unit, a target position determination unit that determines a target position at each time based on the position deviation sent from the deviation determination unit, a target position sent from the target position determination unit, and a final position control parameter based on position control parameters. A position control unit that outputs a command signal to move the movable body that has moved to the vicinity of the target position to the final target position, a changeover switch that switches the speed control to the position control, and a deviation switch from the deviation determination unit. A movement data storage unit that stores a position deviation value and a command signal at each time, and a position deviation value and a position command value when the speed control is executed, which is stored in the movement data storage unit when the speed control is switched to the position control. A guide device using an ultrasonic motor as a drive source for a movable body, the guide device having an initial value setting unit for calculating an initial command signal for switching from a proportional value formula to position control. 2. The ultrasonic motor according to claim 1, wherein the speed control is switched to the position control within a range of 1% to 10% of a maximum moving speed of the movable body. Guide device used as the driving source of the. 3. The target position determining means calculates a target position at each time from a target position at the time of switching from speed control to position control to a final target position by using a polynomial of third or higher order. A guide device using the ultrasonic motor according to claim 1 or 2 as a drive source of a movable body.