JPH07141028A - Piezoelectric actuator controller - Google Patents

Abstract

PURPOSE:To periodically repeat successive position control and to perform high-accuracy position control for ink bottle control by setting scan time to perform the control again within the lapse of time when required position accuracy can not be kept by the natural discharge of a piezoelectric element. CONSTITUTION:Plural driving power source parts are defined as one driving power source 4, and a multiplexer circuit 5 is provided to input the output signal of this driving power source part 4 and to selectively connect it to a piezoelectric element 1 under the control of an arithmetic control part 3. For example, a displacement detector is provided to detect distortion corresponding to the piezoelectric element 1 and the output signal of this displacement detector is inputted through any multiplexer circuit 5, which is different from that multiplexer circuit 5, to the arithmetic control part 3. Then, the position detector of the piezoelectric element 1 under controlling at present is selectively connected corresponding to the output signal of this arithmetic control part 3, and the present position data of the piezoelectric element 1 are fed back.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an ink fountain key drive actuator of an offset printing machine in which the amount of ink can be individually controlled in the printing width direction by a dividing blade.
The present invention relates to a control device that simultaneously performs minute positioning of a plurality of channels.

[0002]

2. Description of the Related Art A piezoelectric element actuator is composed of a piezoelectric element and an ink fountain key (also called a blade), which are integrally formed and provided in a large number in the width direction of a plate cylinder, by controlling the voltage applied to the piezoelectric element. The expansion / contraction operation of the piezoelectric element is used as it is as the movement amount of the key to increase or decrease the ink ejection amount.

FIG. 7 is a block diagram for positioning control of a plurality of conventional piezoelectric elements. Each piezoelectric element 11 has an independent drive power source section 12, and calculation is performed with respect to a position set and input by a setter 13. A command value corresponding to the displacement amount from the control unit 14 is output to the drive power supply unit 12 to generate a voltage or current sufficient to displace the piezoelectric element 11.

[0004]

However, in the present apparatus, when the number of piezoelectric elements to be controlled increases, the driving power source section is also required to correspond to the number of piezoelectric elements, and the piezoelectric element is used for controlling the divided fountain type ink fountain keys of the printing machine. When using elements, several tens of channels are required for each color, there are many components,
This leads to an increase in the size of the device and a high cost. The present invention has been made in view of the above-mentioned points, and its object is to focus on the capacitor characteristics of the pressure point element, and sequentially arrange a plurality of piezoelectric elements and a set of driving power supply circuits into a multiplexer circuit. The scan time is set so that the electric charge of the piezoelectric element is controlled again within the time when the position accuracy required due to spontaneous discharge cannot be maintained when the piezoelectric element is turned off. By repeating the control and by performing highly accurate position control in the ink fountain control of the split blade mechanism, the number of parts related to the control can be significantly reduced, the device can be downsized, and the system price can be reduced. A piezoelectric actuator control device that achieves high reliability is provided.

[0005]

[Means for Solving the Problems] That is, the means for achieving the object is to use a piezoelectric element as a capacitive element in an apparatus using as many piezoelectric elements as the number of positioning points as an actuator for fine positioning control of a plurality of points. Taking advantage of a certain characteristic, after completing the positioning control of one piezoelectric element, the piezoelectric element and the drive power supply circuit that have been controlled until now are separated by a multiplexer, and then the drive power supply section is selectively connected to the piezoelectric element by the multiplexer circuit. After positioning is determined, the drive power supply unit is switched and connected to the next piezoelectric device, one drive power supply unit controls a plurality of piezoelectric devices in sequence, and the scan is repeated within the natural heat dissipation time of the charges of the piezoelectric device. Thus, the position control of a plurality of piezoelectric elements is realized by one set of drive power supply circuit and control circuit.

Further, in order to highly accurately control the position of the piezoelectric element, each piezoelectric element is provided with a displacement detector, which is switched by a multiplexer circuit, and at the same time the current position data is displayed by feedback. is there.

[0007]

Next, this operation will be described including the second aspect. The arithmetic and control unit compares the current position of each piezoelectric element on the basis of the position display of a plurality of positioning points and the position setting of the setting device for setting the position, and is included in the drive power supply unit according to the difference amount. The command is output to the D / A converter. The drive power supply unit is a power supply circuit that drives a piezoelectric element having a variable voltage or variable current source, and its output is selectively connected to a plurality of piezoelectric elements through a multiplexer circuit according to the control of the arithmetic control unit and is controlled to a set position. . Whether or not the control is completed is detected by the displacement detector 1 having an integrated structure with the piezoelectric element, and the detected data is detected by the multiplexer control circuit as well as the drive system by the arithmetic control section to detect the position of the piezoelectric element currently controlled. The device is selectively connected, input to the A / D converter of the signal conversion unit, read by the arithmetic control unit, and judged and at the same time displayed as current position data on the setting device.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. 1 is a block diagram showing an embodiment according to claim 1 of the present invention, FIG. 2 is a block diagram showing an embodiment according to claim 2 of the present invention, FIG. 3 is an explanatory view of a driving power supply unit, and FIG. FIG. 4 is an explanatory diagram of a displacement detector. In FIG. 1, a setting device 2 for position control of the displacement amount of the piezoelectric element 1, an arithmetic control unit 3 for arithmetically controlling the output signal 2a of the setting device according to the channel selection of the piezoelectric element 1, and the arithmetic control unit. Output signal 3b from 3
And a multi-placer circuit 5 for selectively connecting to the plurality of piezoelectric elements 1 according to the control of the arithmetic control unit 3 by inputting a drive power source unit 4 for inputting
And a piezoelectric element 1 to which the output signal 5d is input. Further, as shown in FIG. 3, the drive power source unit 4 includes a D / A conversion circuit 41 for inputting the output signal 3b and an output signal 41 for the D / A conversion circuit 41.
It is composed of a high voltage amplifier circuit 42 for inputting a and a high voltage power source 43 of the high voltage amplifier circuit 42.

Further, in FIG. 2, a displacement detector 5 for detecting strain corresponding to the piezoelectric element 1 is provided, and this displacement detector 6
Output signal 6e of the multiplexer circuit 7 and D /
The position detector 6 of the piezoelectric element 1 which is input to the arithmetic control unit 9 via the A converter 8 and is currently controlled by the output signal 9f of the arithmetic control unit 9 is selectively connected, and the current position of the piezoelectric element 1 is detected. It is configured to feed back data. Further, in the displacement detector 6, as shown in FIG. 4, a strain gauge 61, a bridge circuit 62 for inputting its output signal 61a, and an amplifier circuit 63 for inputting this output signal 62b.
It consists of

In the present invention having such a structure,
FIG. 2 shows one embodiment of FIG. 1. Below, FIG. 2 will be explained with reference to the timing chart shown in FIG. 2 to 4, since the piezoelectric element 1 as a micro displacement actuator fluctuates depending on the ambient temperature and has a large hysteresis characteristic, the displacement detector 6 is integrally enclosed with the piezoelectric element 1 in a system requiring accuracy. A strain gauge is generally used as the displacement detector 6,
The output signal 61a of the strain gauge 61 is composed of a bridge circuit 62 that detects a change in position as a minute change in resistance value and converts the change in resistance value into a voltage, and an amplifier 63 that amplifies the output voltage of the bridge circuit 62. The minute displacement amount is amplified to a voltage that is not affected by noise received by the wiring between the machine and the control device, and is connected to the multiplexer circuit 7. In the multiplexer circuit 7, the channels of the piezoelectric elements for position control are selectively connected by the arithmetic control unit 9 during the Tgn (Tg1, Tg2,) period shown in the timing chart of FIG. During this period, the current position of the channel controlled in the current position reading mode is fetched by the arithmetic control unit 9 through the A / D converter 8.

Position data corresponding to this feedback voltage is output based on the voltage-displacement conversion curve in the arithmetic control unit 9, and the output voltage of the drive power supply unit 4 is changed to the voltage of the piezoelectric element 1 for positioning. Control so that they almost match. The period for controlling the output voltage of the driving power supply unit 4 to match the voltage of the piezoelectric element 1 after capturing the position feedback signal is represented by the Tg mode (Tg1, Tg2) shown in the timing chart of FIG. When connected to the piezoelectric element 1, the piezoelectric element 1 is driven by different voltages.
The timing mode is such that the voltage of the piezoelectric element 1 is matched with the output voltage of the driving power supply unit 4 so that the position of does not change suddenly. During this period, the multiplexer circuit 5 on the driving side is kept in a non-connected state and is not selectively connected to any piezoelectric element 1. After allowing time for the output voltage of the drive power source section to settle, the multiplexer circuit 5 is selectively connected to the piezoelectric element 1 to be controlled.

Next, in order to reset to a new position set value of the piezoelectric element 1 to be controlled, which is read from the setting device 2 into the arithmetic control unit 9, the piezoelectric element 1 is driven in a direction to close the difference between the position set value and the current position. The output voltage of the power supply unit is gradually changed to a voltage value at which the feedback position and the set position match. This period is represented by Td in FIG. 6, and the piezoelectric element 1
After reaching the set target position of, the driving side maltoplexer circuit 5 is brought into the non-selected state again, and the mode shifts to the mode Tg of the next channel.

In this way, the control for all the channels is sequentially and repeatedly controlled, and the time for controlling all the channels is set to Ts, and the control is repeated again at each Ts. Driving time Td from scanning time Ts
During the time when (Td1, Td2 ...) Is subtracted, the charged electric charge, that is, the energy stored in the element is held because the element is a capacitive element of the piezoelectric element, and the capacitance of the piezoelectric element 1 is required. It is assumed that the characteristics are sufficient to maintain the positional accuracy of If the electrostatic capacitance of the piezoelectric element 1 is Cp and the voltage of the piezoelectric element 1 controlled by the driving power supply unit 4 is V, the electric charge Q stored in the piezoelectric element is expressed by the formula (1),
The time t during which this charge spontaneously discharges to q [C] by the internal loss resistance component r is represented by the mathematical expression (2).

[0014]

[Equation 1]

Cp.r is called a natural discharge time constant. In general, the spontaneous discharge time constant of the laminated piezoelectric element shows a large value, and q shows only a change of 1% or less with respect to Q in 10 seconds. Further, this numerical value has a characteristic that it hardly changes depending on the presence or absence of a load applied to the piezoelectric element. Therefore, the scan time Ts can be long enough to control the piezoelectric elements of several tens to several hundreds of channels.

Although this embodiment includes a circuit for reading position feedback, it can be easily inferred that an open loop having only a command system may be used if the required accuracy of the system is low. Further, although the drive power supply unit 4 has been described by taking the example of the variable voltage source, it may be configured by the charge control method in which the time is controlled by the constant current source.

Next, these operations will be described with reference to the flow chart of FIG. When the control is started, the arithmetic control unit 9 reads the set values of all the channels from the setter 2. (A) Next, the operation control unit 9 sets the channel of the multiplexer circuit 7 (b1), and the drive side channel is not selected and the feedback side channel is selected.
(B2) Thereafter, the current position data of the displacement detector 6 whose channel is selected is read by the arithmetic control unit 9 via the D / A conversion circuit 8. (C)

In the drive power supply unit 4, the drive voltage from the arithmetic control unit 9 is changed to a value corresponding to the current position data (d), and the timer (e1) provided in the arithmetic control unit 9 is changed.
Then, the channel on the drive side is selected by the multiplexer circuit 5 according to the scan time described above. (E2) Next, in the drive power supply unit 4, the drive voltage is gradually approached to a value corresponding to the set position data by feedback. (F)

After that, the amount of distortion of the displacement detector 6 is detected and given to the multiplexer circuit 7, and the output thereof is given to the arithmetic control unit 9 through the D / A conversion circuit 8 so that it becomes equal to the set value. It is determined whether or not, and in the case of NO, the process returns to (f) by feedback and the process is repeated.
(G) As described above, the arithmetic control unit 9 determines whether or not the control of each channel is completed. (H) When finished, reset the channel counter,
Return to the start. (I) If it is not completed, the channel counter is incremented (j) and the process returns to b1.

[0020]

As described above, according to the present invention, a large number of piezoelectric elements are used, and at the same time, it is highly effective for controlling the ink fountain of a divided blade mechanism of an offset printing machine, such as a mechanical apparatus which requires minute positioning. The position control with high accuracy can be configured by a small and low-priced device, and the number of wires between the machine and the control device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram according to claim 1 of the present invention.

FIG. 2 is a block diagram according to claim 2 of the present invention.

FIG. 3 is an explanatory diagram of a driving power supply unit.

FIG. 4 is an explanatory diagram of a displacement detector.

FIG. 5 is a flow chart diagram.

FIG. 6 is a timing chart diagram.

FIG. 7 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 Piezoelectric element 2 Setting device 3 Arithmetic control unit 4 Driving power supply unit 5 Multiplexer circuit 6 Displacement detector 7 Multiplexer circuit 8 A / D conversion circuit 9 Arithmetic control unit 11 Piezoelectric element 12 Driving power supply unit 13 Setting device 14 Arithmetic control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 41/09

Claims (2)

[Claims] 1. A setting device for position control of a displacement amount of a voltage element, an arithmetic control unit for arithmetically controlling an output signal of the setting device according to channel selection of a piezoelectric element, and a channel from the arithmetic control unit. In a piezoelectric actuator control device including a plurality of driving power supply units for inputting corresponding output signals and a plurality of piezoelectric elements receiving output signals from the plurality of driving power supply units, the plurality of driving power supply units are A piezoelectric actuator control device comprising a drive power source unit, and a multi-placer circuit for inputting an output signal of the drive power source unit and selectively connecting to the plurality of piezoelectric elements under the control of the arithmetic control unit. 2. A displacement detector that detects strain corresponding to the piezoelectric element is provided, and an output signal of the displacement detector is input to an arithmetic control unit via a multiplexer circuit different from the multiplexer circuit. 2. The piezoelectric device according to claim 1, wherein the position detector of the piezoelectric element currently controlled by the output signal of the arithmetic control unit is selectively connected and the current position data of the piezoelectric device is fed back. Actuator control device.