JP2006165011A - Piezoelectric element driving apparatus and piezoelectric element driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element driving apparatus and a driving method for performing displacement control that causes a large displacement in a piezoelectric element in a short time and further increases its resolution.
A drive device 10 for displacing a piezoelectric element 50 includes a computer 20 and a drive power supply 30. The drive power supply 30 includes a current source Ip ₁ for supplying a current to the piezoelectric element 50, a current sink Im ₁ for discharging a charge charged in the piezoelectric element 50, and a power supply provided in the current source Ip ₁ . a changeover switch Sp ₁ of, and a changeover switch Sm ₁ for discharge provided in the current sink Im _1. The piezoelectric element 50 is extended by repeatedly turning on / off the switch Sp _{1 at} a constant switching time t ₁ . When the piezoelectric element 50 is not charged / discharged, the piezoelectric element 50 is disconnected from the drive power supply 30, so that the displacement is kept constant.
[Selection] Figure 2

Description

The present invention relates to a piezoelectric element driving apparatus and a driving method used in a positioning apparatus using a piezoelectric element, and more particularly to a positioning piezoelectric element driving apparatus and a driving method provided in an ultraprecision positioning apparatus such as a semiconductor manufacturing apparatus.
About.

  For example, with the recent miniaturization and high integration of circuits in semiconductor devices, for example, in a semiconductor manufacturing apparatus such as an exposure apparatus (stepper), it is necessary to position a silicon wafer with high accuracy. Therefore, a piezoelectric element (mainly a laminated piezoelectric element) has been used for positioning the stage holding such a silicon wafer.

  The driving method of the piezoelectric element is roughly divided into voltage driving and current driving. In voltage drive, in order to obtain a desired amount of displacement, normally, a command value (digital signal) generated by a computer is converted into an analog signal by a D / A converter, and the power is amplified by an amplifier to form a piezoelectric element. Apply and displace the piezoelectric element. Then, the displacement amount of the piezoelectric element is measured by a displacement meter, the data is fed back to the computer, and a new command value is generated by the computer (see, for example, Non-Patent Document 1 and Patent Document 1).

  On the other hand, in current driving, the magnitude of the current value output from the constant current power source is controlled by a computer, thereby controlling the amount of charge charged in the piezoelectric element and displacing the piezoelectric element. Also in this case, the displacement amount of the piezoelectric element is measured by a displacement meter, the data is fed back to the computer, and the current value output from the constant current power source is controlled (for example, see Non-Patent Document 2 and Patent Document 2). Such current drive is characterized in that hysteresis does not occur in the displacement of the piezoelectric element. In this case as well, a D / A converter is provided between the computer and the low current power source.

  However, in such a conventional method for driving a piezoelectric element, it is possible to cause displacement in the piezoelectric element in a short time, and to perform displacement amount control with an increased resolution so as to obtain a high resolution on the order of sub-nanometers, for example. This is difficult due to the characteristics of the drive power supply (amplifier).

  The reason is that when the piezoelectric element is driven by voltage, a high resolution is required for the D / A converter, but it is difficult to realize a D / A converter having a resolution of 16 bits or more at high speed. Since the piezoelectric element is displaced, it is difficult to obtain a high resolution, and since the value of the flowing current changes depending on the terminal voltage of the piezoelectric element, the displacement amount per pulse even if a pulse-like constant voltage is applied. Specifically, when the terminal voltage is low, a large amount of current flows and greatly increases. Conversely, when the terminal voltage is high, the current decreases and hardly extends.

  In addition, when the piezoelectric element is driven by current, the output impedance of the constant current power source is generally high and the current value that can be supplied to the piezoelectric element is limited, so that it is difficult to displace the piezoelectric element at high speed. In addition, similarly to voltage driving, there is a problem that it is difficult to increase the resolution of the D / A converter.

Furthermore, in the conventional method of driving the piezoelectric element with current, the piezoelectric element and the driving power source are always in a conductive state even when it is desired to keep the displacement of the piezoelectric element constant. For this reason, there is a problem that current flows between the piezoelectric element and the drive power source, and the piezoelectric element repeats minute expansion and contraction (vibration), thereby reducing the precision of precision positioning.
JP-A-1-181580 Yuichi Okazaki, “Microdisplacement tool table using piezoelectric elements”, Journal of Japan Society for Precision Engineering, 54, 7, pp1375-1380 (1988) Japanese Patent Laid-Open No. 2-129975 CV Newcomb and I. flinn: Improving The Linearity of Piezoelectric Ceramic Actuators, Electronics Letter, 18, pp442-444 (1982)

  The present invention has been made in view of such circumstances, and provides a piezoelectric element driving device and a driving method capable of performing displacement control with a large amount of displacement generated in a piezoelectric element in a short time and with improved resolution. The purpose is to do. Another object of the present invention is to provide a piezoelectric element driving apparatus and a driving method that can make the piezoelectric element stand still in a displaced state.

According to the present invention, there is provided a driving device for current driving a piezoelectric element,
A current source for supplying current to the piezoelectric element;
A power supply changeover switch for supplying power to the piezoelectric element from the current source in a predetermined switching time;
A current sink for discharging the electric charge charged in the piezoelectric element;
A discharge changeover switch for discharging from the piezoelectric element to the current sink in a predetermined switching time;
Comprising
The current source and the current sink are totem-pole connected via the power supply changeover switch and the discharge changeover switch,
The piezoelectric element is charged and displaced by a current pulse generated by repeatedly turning on and off the power supply changeover switch, and the piezoelectric element is charged by a current pulse produced by repeatedly turning on and off the discharge changeover switch. When the electric charge is discharged and displaced, and the piezoelectric element is not charged / discharged, the power supply changeover switch and the discharge changeover switch are held in the OFF state, and the displacement amount of the piezoelectric element is controlled to be constant. There is provided a piezoelectric element driving device.

  In this piezoelectric element driving device, a plurality of power supply changeover switches may be connected to one current source, and the plurality of power supply changeover switches may be connected in parallel to each other and have different switching times. preferable. Similarly, it is preferable that a plurality of discharge changeover switches are connected to one current sink, and the plurality of discharge changeover switches are connected in parallel to each other and have different switching times. Thereby, a large displacement can be generated in the piezoelectric element in a short time, and displacement amount control with improved resolution can be performed.

  The piezoelectric element driving apparatus according to the present invention includes a plurality of current sources, and one power supply changeover switch is connected to each current source, and the peak values of currents extracted from the plurality of current sources are respectively It is also preferable to adopt a different configuration. Further, it is preferable that the switching time of the power supply changeover switch connected to each of the plurality of current sources becomes shorter as the peak value of the current extracted from the current source becomes smaller. Thereby, a large displacement can be generated in the piezoelectric element in a short time, and displacement amount control with improved resolution can be performed.

  Similarly, a plurality of current sinks are provided, and one discharge changeover switch is connected to each current sink, and the peak values of the current values sucked into the plurality of current sinks are different from each other. Furthermore, it is preferable that the switching time of the discharge changeover switch connected to each of the plurality of current sinks becomes shorter as the peak value of the current drawn into the current sink becomes smaller.

  The piezoelectric element driving apparatus according to the present invention can be switched on and off freely in synchronization with the power supply switching switch and the discharge switching switch for each piezoelectric element so that a plurality of piezoelectric elements can be displaced. It is also preferable that a plurality of switches be provided, and the remaining charge / discharge changeover switch be turned off when one charge / discharge changeover switch is turned on.

  The piezoelectric element driving device according to the present invention determines a power supply changeover switch and a switching time, and holds a power supply changeover switch in an ON state only during the switching time by a predetermined ON signal; A second time adjusting circuit that determines a discharge changeover switch and a switching time, and holds the discharge changeover switch in an ON state only during the switching time by a predetermined ON signal, and creates such an ON signal to generate a first time. The signal generator for outputting to the time adjustment circuit and the second time adjustment circuit can be provided.

  Alternatively, a signal generator for generating a pulse signal having a predetermined time width is further provided, and the switching time of the power supply changeover switch and the discharge changeover switch is set according to the time width of the pulse signal output from the signal generator. You may make it do.

  When feedback control of the displacement of the piezoelectric element (closed loop control) is performed, a displacement sensor for measuring the displacement amount of the piezoelectric element, and a power supply changeover switch and a discharge changeover switch based on the measurement data of the displacement sensor are used. What is necessary is just to set it as the structure further provided with the control apparatus for controlling an on-off operation | movement. As described above, when a signal generator for operating the power supply changeover switch and the discharge changeover switch is provided, for example, if the signal generator is a computer, the computer is used as a control device. be able to.

According to the present invention, there is provided a method for driving a piezoelectric element that can be implemented using the above-described piezoelectric element driving apparatus. That is, according to the present invention, there is provided a driving method for current driving a piezoelectric element,
The piezoelectric element is charged by a current pulse having a predetermined charge,
Discharging from the piezoelectric element charged by a current pulse having a predetermined charge,
When the piezoelectric element is not charged / discharged, the amount of displacement of the piezoelectric element is kept constant by opening the electrodes provided on the piezoelectric element to charge / discharge the piezoelectric element, thereby suppressing the movement of charges. There is provided a method for driving a piezoelectric element.

  As the current pulse for charging the piezoelectric element, it is preferable to use a plurality of current pulses having different charge amounts. As the current pulse for discharging from the piezoelectric element, a plurality of current pulses having different charge amounts are used. It is preferable.

  According to the present invention, since a fixed-value current power source is used, a displacement can be controlled with a large displacement generated in the piezoelectric element in a short time and with improved resolution. Even when the current value includes noise, the displacement amount of the piezoelectric element is controlled by the electric charge integrated with the current, so that the error of the displacement amount of the piezoelectric element due to the noise can be extremely reduced. . Further, since the displacement amount of the piezoelectric element with respect to one current pulse for driving the piezoelectric element is known, the displacement amount of the piezoelectric element can be estimated from the number of current pulses without using a displacement meter.

  In addition, since the acceleration when displacing the piezoelectric element can be changed by adjusting the height, pulse width, and generation interval of the current pulse, the positioning mechanism using expansion and contraction of the piezoelectric element has an appropriate acceleration / deceleration characteristic. Therefore, it is possible to realize precise positioning and to suppress residual vibration.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a piezoelectric element driving device 10 (hereinafter referred to as “driving device 10”). The drive device 10 includes a computer 20, a drive power supply (drive amplifier) 30, and a displacement meter 40.

  The computer 20 inputs a command for driving the piezoelectric element 50 by an operator, and drives the piezoelectric element 50 and an input / output unit 21 for displaying the displacement amount of the piezoelectric element 50 so that the operator can visually recognize the displacement amount. A recording unit 23 in which a program or the like for generating a signal for generating a signal is recorded, an input interface (input IF) 24b for taking in data relating to the displacement amount of the piezoelectric element 50 measured by the displacement meter 40, and the displacement amount. A process controller (CPU) 22 that generates a command signal for driving the piezoelectric element 50 according to a program, and a digital output port (for outputting a digital signal generated by the process controller (CPU) 22 to the drive power source 30 ( Output IF) 24a. The input interface (input IF) 24b may be one that captures data using an analog / digital conversion function or one that captures digital signals, depending on the type of displacement sensor.

FIG. 2 shows a schematic configuration of the drive power supply 30 and a schematic connection form of the drive power supply 30 and the piezoelectric element 50. The drive power supply 30 includes one current source (current supply source) Ip ₁ for supplying current to the piezoelectric element 50 and one current sink (current sink) for discharging the charge charged in the piezoelectric element 50. Source) Im ₁ , a power supply changeover switch Sp ₁ provided in the current source Ip ₁ , and a discharge changeover switch Sm ₁ provided in the current sink Im ₁ .

The peak value (referred to as “I ₁ ”) of the current output from the current source Ip ₁ is always constant. As the current source Ip ₁ , a commercially available constant current power supply can be used. At this time, if a large-capacity capacitor is provided in parallel with the power receiving unit of the constant current power supply, electric energy is supplied to the constant current power supply. The capacity of the main power source that supplies the current can be reduced, and the current source Ip ₁ can be made small and inexpensive.

The current sink (current suction source) Im _1, a constant current diode, bipolar transistor, field effect transistor (FET), an operational amplifier (op amp Operational Amplifier) constant current circuit, which is constituted by an IC or the like is preferably used. Here, the current sink Im ₁ can suck the electric charge charged in the piezoelectric element 50 with the current having the peak value I ₁ ′. That is, the peak value of the discharge current of the piezoelectric element 50 is I _1. It shall be '.

As each of changeover switches _{Sp 1} · Sm 1, a power MOS-FET is fast switching element (Power Metal Oxide Semiconductor Field Effect Transistor ) or IGBT (Insulated Gate Bipolar Transistor), use an electrostatic induction transistor (Static Induction Transistor), etc. be able to. These change-over switches Sp ₁ and Sm ₁ are normally in an off state. The circuit configuration is such that the switching time when each change-over switch Sp ₁ · Sm ₁ is in the on state (closed state) is t _1, and the on / off operation of each change-over switch Sp ₁ · Sm ₁ is performed by a computer. 20 is configured to be performed by a signal such as a rectangular pulse having a certain time width output from the signal 20.

  As the displacement meter 40, an appropriate one can be selected according to the maximum displacement amount and resolution of the piezoelectric element 50. For example, a linear encoder, a laser interference displacement meter, an eddy current displacement meter, or the like is used.

Next, a method for driving the piezoelectric element 50 by the driving device 10 will be described. FIG. 3 is a graph schematically showing the relationship between the current (charge) supplied to the piezoelectric element 50 and the amount of displacement of the piezoelectric element 50. First, the current source Ip ₁ is put on standby. Next, the computer 20 generates a control signal (hereinafter referred to as “on signal”) for closing the changeover switch Sp ₁ and outputs the on signal to the drive power supply 30. Thus closes changeover switch Sp ₁ (ON state), flows into the piezoelectric element 50 current of a current value _{I 1} from the current source Ip ₁ only time _{t 1.} In this way, the charge of “I ₁ × t ₁ ” is charged in the piezoelectric element 50, and the piezoelectric element 50 expands according to the amount of the charge (this extension is indicated as “δ” in FIG. 3). When the time _{t 1} to close the changeover switch Sp ₁ has passed over switch Sp ₁ is opened (OFF state).

  As described above, the driving device 10 drives the piezoelectric element 50 with the current pulse. Conventionally, a method of driving a piezoelectric element with a current pulse is known. However, since the driving power source is always connected to the piezoelectric element in the past, charge movement occurs between the piezoelectric element and the driving power source. As a result, the piezoelectric element repeatedly expanded and contracted minutely. However, according to the drive device 10, when the piezoelectric element 50 is not charged / discharged, the drive power supply 30 and the piezoelectric element 50 are separated from each other. Therefore, the piezoelectric element 50 can be brought into a substantially completely stationary state.

By repeating such ON / OFF changeover switch Sp _1, it is possible to extend the piezoelectric element 50 stepwise. The displacement meter 40 measures the amount of displacement of the piezoelectric element 50 and feeds back the data to the computer 20. Computer 20 based on the data, to the amount of displacement of the piezoelectric element 50 reaches the desired value, performs the on / off changeover switch Sp _1.

In order to shrink the piezoelectric element 50 thus stretched, the computer 20 generates an ON signal of the changeover switch Sm ₁ and outputs it to the drive power supply 30. As a result, when the changeover switch Sm ₁ is closed, discharge starts from the piezoelectric element 50, the charge of “I ₁ ′ × t ₁ ” flows into the current sink Im ₁ , and the piezoelectric element 50 contracts according to the amount of the charge. . When the time _{t 1} to close the change-over switch Sm ₁ has elapsed open the change-over switch Sm _1. Thereby, since the discharge from the piezoelectric element 50 is stopped, the displacement of the piezoelectric element 50 is maintained. By repeating such on / off, the piezoelectric element 50 can be contracted stepwise. In FIG. 3, I ₁ = I ₁ ′, but I ₁ ≠ I ₁ ′ may be used.

Note that the displacement amount of the piezoelectric element 50 can be controlled even in a configuration in which the displacement sensor 40 is removed from the driving device 10 (so-called open loop control). For example, when the piezoelectric element 50 is driven without using the displacement sensor 40, the displacement amount of the piezoelectric element 50 when the piezoelectric element 50 is charged with the charge amount “I ₁ × t ₁ ” and the piezoelectric element 50 are charged. The upper limit of the charge amount that can be measured is measured in advance, and the information is input to the computer 20. Then, the computer 20 calculates the amount of charge necessary to obtain the desired displacement, and further calculates the ON / OFF count changeover switch Sp _1, it may be charged to the piezoelectric element 50. Even in a configuration in which the displacement sensor 40 is not used as described above, the generation of hysteresis can be suppressed in the charge control in which the piezoelectric element 50 is driven with a current pulse.

In the driving method shown in this FIG. 3, by increasing the current value I ₁ which is output from the current source Ip _1, and, the longer the switching time t ₁ of the switch Sp _1, displacement of one of the piezoelectric elements 50 Although the amount can be increased, it is difficult to obtain high resolution. On the other hand, to reduce the current value I ₁ which is output from the current source Ip _1, and, when shortening the switching time t ₁ of the switch Sp _1, although a single displacement of the piezoelectric element 50 is small, to obtain a high resolution be able to. The same applies to the relationship between the current I ₁ ′ that can be passed through the current sink Im ₁ and the switching time of the changeover switch Sm ₁ .

  In driving the piezoelectric element 50 using the drive power source 30, the acceleration when the piezoelectric element 50 is deformed can be changed by changing the height, pulse width, and generation interval of the current pulse. Therefore, in the positioning mechanism using the expansion and contraction of the piezoelectric element 50, an appropriate acceleration / deceleration characteristic can be set, so that accurate positioning can be realized and residual vibration can be suppressed.

In the driving device 10, the switching times of the changeover switch _Sp 1 · Sm ₁ is fixed to _{t 1,} the configuration of the computer 20 outputs an ON signal for the on / off operation the selector switch _Sp 1 · Sm ₁ The switching times of the changeover switches Sp ₁ and Sm ₁ can be changed to a configuration in which the switching time is adjusted by the time width of the rectangular wave output from the computer 20. This configuration change can be performed by changing a program for signal generation recorded in the recording unit 23 of the computer 20.

FIG. 4 shows a graph schematically showing the relationship between the current (charge) supplied to the piezoelectric element 50 and the displacement amount of the piezoelectric element 50 when using such a driving device. The driving method of the piezoelectric element 50 shown in FIG. 4 is as follows. That is, first, the current source Ip ₁ is put on standby. Next, the computer 20 generates an ON signal in which the switching time of the changeover switch Sp ₁ is T ₁ and outputs it to the drive power supply 30. As a result, a current having a current value I ₁ flows from the current source Ip ₁ into the piezoelectric element 50 for a time T ₁ , and the charge of “I ₁ × T ₁ ” is charged in the piezoelectric element 50. It grows accordingly. The changeover switch Sp ₁ is opened when the time _{T 1} to close the changeover switch Sp ₁ has elapsed.

Subsequently, the computer 20 generates an ON signal of the changeover switch Sp ₁ whose switching time is T ₂ (T ₂ <T ₁ ), and outputs it to the drive power supply 30. As a result, the charge of “I ₁ × T ₂ ” is charged in the piezoelectric element 50, and the piezoelectric element 50 expands according to the amount of charge. Such an on / off changeover switch Sp _1, carried out sequentially by the on signal of a time width _{T 3, T 4 (T 4} <T 3 <T 2 <T 1). Thereby, a large displacement and a high resolution can be obtained with a small number of on / off times.

When the piezoelectric element 50 thus extended is contracted, if the high resolution is not required, for example, the changeover switch Sm ₁ may be turned on / off by an on signal of the switching time T ₁ . On the other hand, in the case that requires a high resolution in order to control the amount of shrinkage, the changeover switch Sm ₁ is turned on / off appropriately combined on signal time width T ₁ through T ₄ or on the time width T _4, the changeover switch Sm ₁ may be turned on / off by the signal.

In addition, when the displacement amount of the piezoelectric element 50 is determined in advance and when the displacement amount of the piezoelectric element 50 is measured by the displacement meter 40 and feedback control is performed, the computer 20 is based on the data from the displacement meter 40. Until the amount of displacement of the piezoelectric element 50 reaches a desired value, one having an appropriate time width is selected from the ON signals of the time widths T _{1 to} T ₄ , and the changeover switch Sp ₁ is repeatedly turned on / off.

The above-described driving method of the piezoelectric element 50 shown in FIG. 4 can also be performed using the driving power source 30a shown in FIG. FIG. 5 is a diagram showing a schematic configuration of the drive power supply 30a and a schematic connection form of the drive power supply 30a and the piezoelectric element 50. As shown in FIG. Driving power source 30a includes a current source Ip _1, current sink Im ₁ and a changeover switch _{Sp 1 · Sp 2 · Sp 3} · Sp 4 for feeding in parallel connected, changeover switch Sm ₁ for parallel connected discharge · _Sm and a 2 · _Sm 3 · _{Sm 4.} Switching time of the switch _{Sp 1 · Sp 2 · Sp 3} · Sp 4 is fixed to each of _{T 1, T 2, T 3} , T 4 (T 4 <T 3 <T 2 <T 1), switching switching time of the switch _{Sm 1 · Sm 2 · Sm 3} · Sm 4 is also fixed to the _{T 1, T 2, T 3} , T 4 , respectively.

Computer 20 for each change-over switch a signal such as a rectangular pulse of a constant duration _{Sp 1 ~Sp 4 · Sm 1 ~Sm} 4 for the on / off operation the selector switch _{Sp 1 ~Sp 4 · Sm 1 ~Sm} 4 Output.

To make the drive of the piezoelectric element 50 shown above with reference to such a computer 20 and a driving power source 30a in FIG. 4, first, turns on the changeover switch Sp ₁ (this time, the other changeover switch Sp 2 _· Sp ₃ · Sp ₄ · Sm ₁ is turned off), and the piezoelectric element 50 is charged with the charge of “I ₁ × T ₁ ”. After changeover switch Sp ₁ is turned off subsequently, by turning on the changeover switch Sp ₂ to charge the charge of _{"I 1} × T _2" to the piezoelectric element 50, after the changeover switch Sp ₂ is turned off switches the switch Sp ₃ are turned on to charge the charge of _{"I 1} × _{T 3"} to the piezoelectric element 50, further the changeover switch Sp ₃ by turning on the switch Sp ₄ switched after turned off _{"I 1} × T _The piezoelectric element 50 is charged with the charge of ₄ ″.

The discharging may be performed in the same manner as this charging method by sequentially turning on / off the changeover switches Sm _{1 to} Sm ₄ . When feedback control is performed by measuring the displacement amount of the piezoelectric element 50 with the displacement meter 40, a suitable changeover switch among the changeover switches Sp _{1 to} Sp ₄ is appropriately selected according to the target displacement amount of the piezoelectric element 50. It may be selected and turned on / off once or a plurality of times.

Since the drive power sources 30 and 30a described above have only _one current source Ip _{1, the} amount of charge that can charge the piezoelectric element 50 by turning on / off the changeover switch Ip ₁ once is sufficient. The resolution of the piezoelectric element 50 is determined by the minimum value. That is, the resolution of the piezoelectric element 50 is determined by the minimum switching time t _min of the changeover switch Ip ₁ , and charges less than “I ₁ × t _min ” are charged in the piezoelectric element 50 to control the displacement amount of the piezoelectric element 50. It is not possible. Similarly, with respect to the current sink Im ₁ , it is not possible to discharge a charge less than “I ₁ × t _min ” from the piezoelectric element 50.

  Accordingly, a drive power supply that can displace the piezoelectric element 50 greatly in a short time by providing a plurality of current sources and current sinks having different peak current values, and can further increase the resolution of the piezoelectric element 50 is shown in FIG. This will be described with reference to FIG. FIG. 6 shows a schematic configuration of the drive power supply 60.

The driving power source 60 is a current source _Ip n of n (n is an integer of 2 or more) for supplying current to the piezoelectric element _{50 (Ip 1, Ip 2,} ···, Ip n) and, k pieces ( current sink _Im k _{(Im 1,} Im 2 of k is an integer of 2 or more), ..., and Im _k), the changeover switch _Sp n provided for each current source _{Ip n (Sp 1, Sp 2} , ·· ., Sp _n ) and changeover switches Sm _k (Sm ₁ , Sm ₂ ,..., Sm _k ) provided for each current sink Im _k .

Each current source Ip _n and the current sink Im _k is a totem-pole connected through the respective changeover switch Sp _n and each switching switch Sm _k. Although FIG. 6 shows a case where k = n, k ≠ n may be used.

In the drive power supply 60, the magnitudes of the peak currents that can be supplied from the _n current sources Ipn are different. For example, the current source _{(Ip 1, Ip 2, ···} , Ip n) is the peak current value in each _{(I 1, I 2, ···} , I n) is configured capable of supplying a current Yes. For example, as in a general D / A converter, the peak current values (I ₁ , I ₂ ,..., I _n ) have a geometric sequence with a common ratio of 2 (that is, I ₁ , I ₂ = _{I 1/2,} to be a ^{_{I n = I 1/2 n}} ), it can also be a non-uniform rate.

Similarly, the magnitudes of the peak currents that can be absorbed by the _k current sinks Im _k are different. For example, the current sinks (Im ₁ , Im ₂ ,..., Im _k ) have peak current values (I ₁ , I ₂ ,..., I _k ) having a geometric sequence relationship with a common ratio of 2, respectively. ) Current can be sucked. Here, since k = n, the peak current value _{I k} of the peak current value _{I n} and the current sink Im _k of the current source Ip _n are the same size, respectively.

The switching times of the _n changeover switches Spn provided for each of the _n current sources Ipn may be different from each other. However, for the sake of easy explanation and understanding, all of them are “t ₁ ”. And the same. Further, the switching times of the _k change-over switches Sm _k provided for each of the _k current sinks Im _k may be different from each other, but here, it is assumed that all are the same at “t ₁ ”. Computer 20 outputs the respective changeover switch _Sp n · Sm _k signals of k + n pieces of rectangular pulses or the like of a predetermined time width for on / off operation of k + n pieces each switching switch _Sp n · Sm _k of.

If the switching time t ₁ is the minimum switching time t _min , for example, if the changeover switch Sp ₂ · Sm ₂ is turned on / off, the charge transfer amount at that time is “I ₂ × t _min = (I ₁ / 2) × t _min ″. Therefore, by turning the changeover switches Sp ₂ and Sm ₂ on and off once, the piezoelectric element 50 is charged with less charge than “I ₁ × t _min ” which is the minimum charge transfer amount in the drive power supply 30 and 30a described above. Since the piezoelectric element 50 can be supplied and discharged from the piezoelectric element 50, the resolution of the piezoelectric element 50 can be increased.

Needless to say, k + n pieces of may be set to different switching times for each changeover switch Sp n _· Sm _k, but if so, the amount of charge equal to the respective current source Ip _n is supplied to the piezoelectric element 50 From the viewpoint of displacing the piezoelectric element 50 in a short time with high resolution, the switching time is set so that the amount of charge sucked into each current sink Im _k from the piezoelectric element 50 is not the same. ,preferable.

The driving method of the piezoelectric element 50 by the driving power source 60 is the same as the method of driving the piezoelectric element 50 by the driving power source 30a shown in FIG. For example, the changeover switch Sp ₁ is turned on, the charge of “I ₁ × t ₁ ” is charged in the piezoelectric element 50, and the piezoelectric element 50 is extended. Following after the changeover switch Sp ₁ is turned OFF state and turns on the changeover switch Sp ₂ to charge the charge of _{"I 2} × t _1" to the piezoelectric element 50, further expanding the piezoelectric element 50. Such charging operation performed for switching the switch Sp _n which are appropriately selected. In the same manner as this charging method, discharging may be performed by sequentially turning on / off one appropriately selected from the change-over switches Sm _{1 to} Sm _k .

When the displacement amount of the piezoelectric element 50 is measured by the displacement meter 40 and feedback control is performed, the computer 20 determines that the displacement amount of the piezoelectric element 50 reaches a desired value based on the data from the displacement meter 40. select suitable from the current source Ip _n, turning on / off changeover switch Sp _n corresponding thereto.

A method of driving the piezoelectric element 50 using the driving power source 60 will be described more specifically with numerical values. It is assumed that the piezoelectric element 50 is a multilayer piezoelectric element. When the current I ₁ for charging / discharging the piezoelectric element 50 is 10 A and the switching time t ₁ is 50 μs (microseconds), the piezoelectric element 50 is turned on when the changeover switch Sp ₁ is turned on / off once. The charge supplied to is 500 μC. If the current I ₂ is 1 mA, the switching time t ₁ is 50 μs, so that the charge supplied to the piezoelectric element 50 when the changeover switch Sp ₂ is turned on / off once is 50 nC. Here, since the displacement amount of the piezoelectric element 50 is substantially proportional to the charge amount, the difference in displacement amount of the piezoelectric element 50 when the changeover switches Sp ₁ and Sp ₂ are turned on and off once is easily about 10,000 times. Obtainable.

If the electrostatic capacity of the piezoelectric element 50 is 6 μF and it is extended by 10 μm when 100 V is applied, the charged charge at the maximum extension is 600 μC. Therefore, if the changeover switch Sp ₁ is used, 8.3 μm (= 10 μm × A displacement amount of 500 μC / 600 μC) can be obtained. Further, since the resolution in the case of using the changeover switch Sp ₂ becomes 0.83nm (= 10μm × 50nC / 600μC ), it is possible to displacement control in the sub-nanometer order. Here, if the switching time t ₁ of the changeover switches Sp ₁ and Sm ₂ is further changed to 10 μs, the resolution is about 0.17 nm.

Therefore, when the changeover switches Sp ₁ and Sp ₂ are combined, the piezoelectric element 50 can be driven at high speed and with high resolution. It can be said that such a driving method of the piezoelectric element 50 is a driving method in which a change in current pulse supplied to the piezoelectric element 50 and pulse density modulation are combined. For this reason, a high resolution can be easily obtained even though the number of stages is smaller than that in the case of using a normal D / A converter.

Next, a method and circuit configuration for driving a plurality of piezoelectric elements 50j (j is a natural number of 2 or more) using the drive power supply 60 will be described. FIG. 7 shows a connection form between the drive power supply 60 and the plurality of piezoelectric elements 50j. Since the configuration of the drive power source 60 has been described with reference to FIG. 5, the description thereof is omitted here. The plurality of piezoelectric elements 50j are connected in parallel, performs feeding / discharging of the piezoelectric element 50j each piezoelectric element 50j, also by switching the switch Sc ₁ to SC _j is provided for holding the piezoelectric element 50j to open Yes.

When the piezoelectric element 50 ₁ will be driven one by one in sequence maintains the changeover switch Sc ₁ to the ON state, the other switches Sc ₂ to SC _j and maintained in the OFF state, as described previously as other switch is turned off when one switch in the selector switch Sp ₁ to SP _n is oN, turns on the switch selected from among changeover switch Sp ₁ to SP _n / turns off, it may be charged to the piezoelectric element 50 _1. Then, when the desired displacement of the piezoelectric element 50 ₁ is obtained, in order to drive the piezoelectric element 50 _2, holds the changeover switch Sc ₂ to the ON state, the other changeover switch _Sc 1 _{· Sc} 3 _{~Sc j} and maintained in the oFF state, in the same manner as in the method for charging a piezoelectric element 50 ₁ may be charged to the piezoelectric element 50 _2. Further, such a process is performed for the remaining piezoelectric elements 50 ₃ to 50 _j .

Further, in the case of sequentially driving the piezoelectric element ₅₀ 3 to 50 _j may be to synchronize the selected selector switch Sp _n and changeover switch Sc _j turned on / off. Operation when reducing the piezoelectric element 50 ₃ to 50 _j, change the operation of the switch Sm _n switching operation of the switch Sp _n during charging, it others that may be carried out in the same manner, from the above description Since it is clear, the detailed explanation here is omitted.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this. For example, as a method for adjusting the switching time of various change-over switches such as the change-over switch Sp _n , a circuit is configured so that there is only a fixed pulse width for each current value I _n (or I _k ), and sent from the computer 20. It is also possible to detect the rising edge of the ON signal and take the timing of generating the current pulse.

  The present invention can also be used to drive a Stewart platform type parallel mechanism. FIG. 8 shows a schematic configuration of the parallel mechanism 60. The parallel mechanism 60 has a structure in which the base plate 63 and the stage 64 are connected using six links 61a to 61f that are expanded and contracted by the piezoelectric elements 62a to 62f. The expansion and contraction of these links 61a to 61f is controlled by a computer 65 equipped with a controller (CPU), a signal input / output interface, and the like, so that the translation of the stage 64 in the xyz direction and the inclination around those axes are six degrees of freedom. The degree can be controlled.

  Each of the links 61a to 61f is provided with a displacement sensor (not shown) for measuring the amount of expansion / contraction of each piezoelectric element 62a to 62f. The output of each displacement sensor is taken into the computer 65, and the expansion and contraction of each piezoelectric element 62a to 62f is determined based on the program stored in the computer 65. Accordingly, the computer 65 gives a drive signal to the drive power supply 66. The drive power supply 66 has the configuration shown in FIG. 7, and the drive power supply 66 applies a predetermined current pulse to the piezoelectric elements 62a to 62f based on the drive signal.

As described above, a pulsed current is supplied to the piezoelectric elements 62a to 62f, and similarly, discharge from the piezoelectric elements 62a to 62f is performed. Therefore, in the parallel mechanism 60, for example, 6 in one cycle of control. It is possible to drive the piezoelectric elements 62a to 62f while switching the so-called time-division method. Specifically, switching the changeover switch _{Sp 1, Sp 2, ···,} Sp 6 or _{Sm 1, Sm 2, ···,} Sm 6 and _{Sc 1,} Sc 2, · · ·, the Sc _6. With this operation, the operating rate of the drive power supply 66 can be increased. In FIG. 8, the selection of the links 61a to 61f (that is, the selection of the piezoelectric elements 62a to 62f) is referred to as “channel selection”, and the charge / discharge selection of the piezoelectric elements 62a to 62f is referred to as “source / sink selection”. ing.

  Furthermore, the present invention can also be applied to an ink jet printer that discharges ink particles by driving a piezoelectric element. In that case, the ink capacity of one drop can be changed by changing the displacement acceleration of the piezoelectric element.

(Example 1)
In the drive power supply 30 having the configuration shown in FIG. 2, a circuit having a transistor and a resistor is used as a current source Ip ₁ and a current sink Im ₁ by connecting a 9.4 μF capacitor as a load instead of a piezoelectric element. The charging / discharging current is 60 mA, the switching time (current pulse width) of the changeover switch Sp ₁ is 500 μs, the switching time of the changeover switch Sm ₁ is 100 μs, and the voltage of the capacitor is changed by repeatedly turning on / off the changeover switch Sp _1. raised, lowered the voltage of the capacitor by causing repeated on / off switching switch Sm _1. The increase or decrease of the capacitor voltage corresponds to the increase or decrease of the charge. On the other hand, the displacement of the piezoelectric element is proportional to the charge to be charged. Therefore, this experiment can be considered equivalent to displacement control of the piezoelectric element. A more detailed circuit configuration of the drive power supply 30 is shown in FIG. 9, and a graph showing changes in capacitor electrode voltage is shown in FIG.

As shown in FIG. 10, due to a single on / off of the switch Sp _1, Sm _1, the electrode terminal voltage of the capacitor is changed stepwise. When the power supply to the capacitor (charging) is stopped, the capacitor terminal voltage decreases slightly because the current is flowing from the capacitor to the oscilloscope because the waveform is observed with the oscilloscope. This is not caused by the current flowing between the capacitor and the drive power supply 30. From FIG. 10, it is possible to control the terminal voltage of the capacitor with high resolution by reducing one step of the voltage change of the capacitor, that is, by reducing the amount of charge that can be flowed by _one switching of the changeover switch Sp1. You can see that you can. This indicates that when the capacitor is replaced with a piezoelectric element, the piezoelectric element can be driven with high resolution.

  Actually, the electric charge is reduced by the internal resistance of the piezoelectric element and the discharge into the air. However, it is possible to minimize the displacement error of the piezoelectric element by measuring in advance the decrease in displacement caused by this and giving a current pulse to compensate for it in a certain time interval.

(Example 2)
In the driving power source 60 shown in FIG. 6, a circuit with n = k = 2 was formed, and the piezoelectric element was displaced.
(Experimental device)
A pulse signal was generated by a DSP (sbox manufactured by MTT), and the constant current circuit was driven thereby. As a piezoelectric actuator, FPA-100-DEMO manufactured by Dynamic Structures & Materials was used. This has a mechanism for enlarging the displacement of the stacked piezoelectric element AE0505D16 made by NEC / TOKIN. The amount of displacement was 70 μm when 100 V was applied, and hysteresis associated with step-up / step-down was observed in the case of voltage driving. The natural frequency is 1.3 kHz alone, and 1 kHz when a sensor target described later is attached.

  The displacement of the piezoelectric actuator was measured with an eddy current sensor (EX-201 manufactured by Keyence) using a steel plate of 20 mm × 20 mm × 2 mm as a target. The sensor output was amplified 20 times with a differential amplifier 5307 manufactured by NF circuit design block. Therefore, the sensitivity of 1 mm / 5.65V was 1 mm / 113V. However, since the noise is also amplified, the resolution remains unchanged at 0.4 μm. The cut-off frequency of the sensor was set to 1 kHz.

  The sbox_DaGet () function was used for time adjustment of the current pulse width. Since it was 324 μs when it was looped 1000 times, it was calculated as 324 ns (nanosecond) per one time. Due to the slew rate of the D / A converter, the rising / falling waveform becomes dull as shown in FIG. 11, and it was confirmed that it takes about 10 μs to change by 5V.

(Current pulse width setting)
By driving the piezoelectric element by open loop control, the pulse width was set so that the displacement amount per current pulse was equal between the current source and the current sink. The amount of charge per current pulse was adjusted by setting the pulse width of the larger current value between the current source and current sink to the shortest time (5 μs) and increasing the smaller pulse width. Also, by adjusting the pause time, the period of one cycle of the current source / current sink is coarsely adjusted (current source Ip ₁ , current sink Im ₁ ) is 640 μs (waiting 2000 times), and finely adjusted (current source Ip ₂ , current The sink Im ₂ ) was set to 160 μs (waiting for 500 times). As previously described in Example 1, when an oscilloscope was connected to measure the terminal voltage of the piezoelectric element constituting the piezoelectric actuator, the leakage current increased and the linearity deteriorated, so the oscilloscope was not connected. .

  Table 1 shows the current value and pulse width after such adjustment. It should be noted that a slightly shorter pulse width can be set due to circuit performance.

FIG. 12 is a graph showing the amount of displacement when the piezoelectric actuator is displaced using the coarse power source circuit portion of the drive power source, that is, the current source Ip ₁ , the current sink Im ₁ , and the changeover switches Sp ₁ and Sm ₁ . Both expansion and contraction are driven by 70 pulses. The reason for the poor linearity during contraction is that the linearity of the current sink circuit is poor. The displacement per one current pulse of the piezoelectric actuator was 0.51 μm (4.07 V / 70 pulses).

FIG. 13 is a graph showing the amount of displacement when the piezoelectric actuator is displaced using the circuit portion for fine movement of the drive power source, that is, the current source Ip ₂ , the current sink Im ₂ , and the changeover switches Sp ₂ and Sm ₂ . Both expansion and contraction are driven with 5000 pulses each. As shown in FIG. 13, the influence of the leakage current was not observed even when the driving was performed in an open loop with only fine movement. In the calculation, the displacement amount of the piezoelectric actuator was 7.1 nm / 1 current pulse (4.00 V / 5000 pulse). The amount of charge charged in the piezoelectric element is the product of the terminal voltage and the capacitance. Therefore, by connecting a capacitor in parallel to the piezoelectric element, the voltage change is reduced even when a pulse having the same charge amount is applied, and the displacement resolution of the piezoelectric element can be further improved.

(Example 3)
Using the apparatus of Example 2, feedback control for causing the displacement of the piezoelectric element to follow the target value was performed. The target value was given as a step-like voltage changing from 0.5 V to 5.2 V as shown in FIG. The displacement of the piezoelectric element was measured with an eddy current displacement meter manufactured by Keyence Corporation. The displacement of the piezoelectric actuator in this feedback control is shown in FIG. The rise time of the displacement was 50 ms (milliseconds) due to the relationship between the amount of charge determined by the product of the current value per pulse and the pulse width and the capacitance of the piezoelectric element.

  The present invention is suitable for precise positioning in a semiconductor manufacturing apparatus or the like.

The figure which shows schematic structure of a piezoelectric element drive device. The figure which shows schematic structure of a drive power supply, and the general connection form of a drive power supply and a piezoelectric element. The graph which shows typically the relationship between the electric current (electric charge) supplied to a piezoelectric element, and the displacement amount of a piezoelectric element. 4 is another graph schematically showing the relationship between the current (charge) supplied to the piezoelectric element and the amount of displacement of the piezoelectric element. The figure which shows the schematic structure of another drive power supply, and the general connection form of the drive power supply and a piezoelectric element. The figure which shows schematic structure of another drive power supply. The figure which shows the form which connected the several piezoelectric element to the drive power supply shown in FIG. The figure which shows schematic structure which applied the drive power supply to the Stewart platform type parallel mechanism. The figure which shows the more detailed circuit structure of the drive power supply shown in FIG. The graph which shows the change of the electrode voltage of a piezoelectric element. The graph which shows the rising / falling waveform of a current pulse. The graph which shows the displacement of the piezoelectric actuator by a coarse motion circuit. The graph which shows the displacement of the piezoelectric actuator by a fine movement circuit. (A) is a graph which shows the position command voltage in displacement feedback control, (b) is a graph which shows the displacement of a piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10; Piezoelectric element drive device 20; Computer 21; Input / output part 22; Process controller (CPU)
23; Recording unit 24a; Digital output port (output IF)
24b; input interface (input IF)
30 · 30a · 60; driving power source 40; displacement sensor 50 · 50 _j; piezoelectric element 60; the parallel mechanism 61a to 61f; link 62a to 62f; piezoelectric element 63; the base plate 64; stage 65; computer 66; driving power Ip _n; Current source Im _k ; Current sink Sp _n ; (For power supply) selector switch Sm _k ; (Discharge) selector switch Sc _j ; (Charge / discharge) selector switch

Claims (15)

A driving device for current driving a piezoelectric element,
A current source for supplying current to the piezoelectric element;
A power supply changeover switch for supplying power to the piezoelectric element from the current source in a predetermined switching time;
A current sink for discharging the electric charge charged in the piezoelectric element;
A discharge changeover switch for discharging from the piezoelectric element to the current sink in a predetermined switching time;
Comprising
The current source and the current sink are totem pole connected via the power supply changeover switch and the discharge changeover switch,
The piezoelectric element is charged and displaced by a current pulse generated by repeatedly turning on and off the power supply changeover switch, and the piezoelectric element is charged by a current pulse produced by repeatedly turning on and off the discharge changeover switch. When the electric charge is discharged and displaced, and the piezoelectric element is not charged / discharged, the power supply changeover switch and the discharge changeover switch are held in the OFF state, and the displacement amount of the piezoelectric element is controlled to be constant. A piezoelectric element driving apparatus characterized by comprising:   The plurality of power supply changeover switches are connected to one current source, and the plurality of power supply changeover switches are connected in parallel to each other and have different switching times. Piezoelectric element driving device.   2. The discharge changeover switch is connected in plural to one current sink, and the plurality of discharge changeover switches are connected in parallel to each other and have different switching times. Item 3. The piezoelectric element driving device according to Item 2. A plurality of the current sources are provided, and the feeding switch is connected to each current source one by one,
2. The piezoelectric element driving apparatus according to claim 1, wherein peak values of currents taken from the plurality of current sources are different from each other.   5. The piezoelectric element according to claim 4, wherein a switching time of the power supply changeover switch connected to each of the plurality of current sources becomes shorter as a peak value of a current taken out from the current source becomes smaller. Drive device. A plurality of the current sinks, and one discharging changeover switch is connected to each current sink;
6. The piezoelectric element driving device according to claim 1, wherein peak values of current values sucked into the plurality of current sinks are different from each other.   7. The piezoelectric element according to claim 6, wherein a switching time of the discharge changeover switch connected to each of the plurality of current sinks is shortened as a peak value of a current sucked into the current sink decreases. Drive device. In order to be able to displace a plurality of piezoelectric elements, each piezoelectric element includes a plurality of charging / discharging changeover switches that can be turned on / off in synchronization with the power supply changeover switch and the discharge changeover switch,
The piezoelectric element driving device according to any one of claims 1 to 7, wherein when one charge / discharge changeover switch is in an on state, the remaining charge / discharge changeover switches are in an off state. A first time adjustment circuit that determines a switching time with the power supply changeover switch and holds the power supply changeover switch in an ON state only during the switching time by a predetermined ON signal;
A second time adjustment circuit for determining the discharge changeover switch and the switching time, and holding the discharge changeover switch in an ON state only during the switching time by a predetermined ON signal;
A signal generator for producing the ON signal and outputting it to the first time adjustment circuit and the second time adjustment circuit;
The piezoelectric element driving device according to claim 1, comprising: A signal generator for generating a pulse signal having a predetermined time width;
9. The switching time of the power supply changeover switch and the discharge changeover switch is set according to a time width of a pulse signal output from the signal generator. A piezoelectric element driving device according to claim 1. A displacement sensor for measuring a displacement amount of the piezoelectric element;
Based on measurement data of the displacement sensor, a control device for controlling the on / off operation of the power supply changeover switch and the discharge changeover switch;
The piezoelectric element driving apparatus according to claim 1, further comprising: A displacement sensor for measuring a displacement amount of the piezoelectric element;
10. The signal generator according to claim 9, wherein the signal generator generates a control signal for controlling on / off operation of the power supply changeover switch and the discharge changeover switch based on measurement data of the displacement sensor. Item 15. The piezoelectric element driving apparatus according to Item 10. A driving method for current driving a piezoelectric element,
The piezoelectric element is charged by a current pulse having a predetermined charge,
Discharging from the piezoelectric element charged by a current pulse having a predetermined charge,
When the piezoelectric element is not charged / discharged, the amount of displacement of the piezoelectric element is kept constant by opening the electrodes provided on the piezoelectric element to charge / discharge the piezoelectric element, thereby suppressing the movement of charges. A method for driving a piezoelectric element, characterized in that:   14. The method of driving a piezoelectric element according to claim 13, wherein a plurality of current pulses having different charge amounts are used as current pulses for charging the piezoelectric element.   15. The method of driving a piezoelectric element according to claim 13, wherein a plurality of current pulses having different charge amounts are used as current pulses for discharging from the piezoelectric element.

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