JPH05111266A - Controller for piezoelectric actuator - Google Patents

Abstract

PURPOSE:To provide a controller for a piezoelectric actuator which can rapidly and accurately control the actuator. CONSTITUTION:A charging FET 19 is connected between a high voltage power source 5 for generating a positive voltage and a piezoelectric actuator l, and a discharging FET 30 is connected to the actuator 1. A position sensor 7 detects a value (position) responsive to an elongation/contraction of the actuator 1. A differential amplifier 8 obtains a deviation between a position of the actuator 1 from the sensor 7 and a target value of the actuator 1 from a control circuit 6, and so controls the FETs 19, 30 as to obtain charging;discharging current responsive to the deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator control device which uses a piezoelectric element as an actuator and controls expansion and contraction of the actuator.

[0002]

2. Description of the Related Art Piezoelectric actuators used for precision positioning or the like are displaced by applying a voltage. However, if the amount of displacement is controlled by the applied voltage, a hysteresis as shown in FIG. This is an obstacle to accurate positioning. As a measure against this,
As shown in FIG. 5, a method of controlling by the amount of charge injected into the piezoelectric actuator is performed (Japanese Patent Laid-Open No. 1-99).
270, JP-A-2-202384). This is a method of injecting a constant charge at a constant speed in order to displace it to a target position, and as shown in FIG.
Of the electric charge of the piezoelectric actuator 71 is compared with the target value of the piezoelectric actuator 71 by the comparison circuit 72, and the charging FET 73 or the discharging FET 74 as a switching element is turned on by the comparison result.
It is supposed to turn off.

[0003]

However, as shown in FIG. 7, since charge is injected and poured out at a constant speed, overshoot and chattering occur due to the response delay of the piezoelectric actuator near the target value. It is difficult to perform high-speed and highly accurate positioning. On the contrary, if the charge injection speed is reduced to prevent chattering, the positioning speed becomes slow.

Therefore, an object of the present invention is to provide a piezoelectric actuator control device capable of controlling a piezoelectric actuator at high speed and with high accuracy.

[0005]

According to the present invention, there is provided a charging current adjusting means connected between a charging power source for generating a positive voltage and a piezoelectric actuator, and a discharging current adjusting means connected to the piezoelectric actuator. A sensor for detecting a value corresponding to expansion / contraction of the piezoelectric actuator, and a deviation between a value corresponding to expansion / contraction of the piezoelectric actuator by the sensor and a target value of the piezoelectric actuator are obtained, and a charging / discharging current corresponding to the deviation is obtained. A gist of the present invention is a piezoelectric actuator control device including a control means for controlling the charging current adjusting means and the discharging current adjusting means.

[0006]

The sensor detects a value corresponding to the expansion / contraction of the piezoelectric actuator, and the control unit obtains the deviation between the value corresponding to the expansion / contraction of the piezoelectric actuator by the sensor and the target value of the piezoelectric actuator. The charging current adjusting means and the discharging current adjusting means are controlled to obtain the charging / discharging current.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a system for controlling the absolute position of a piezoelectric actuator will be described below with reference to the drawings.

FIG. 2 shows a piezoelectric actuator 1. The piezoelectric actuator 1 is configured by alternately laminating a large number of electrode plates 2 and a large number of piezoelectric elements 3 one by one. The elements 3 are electrically connected in parallel, and expand / contract in the stacking direction according to the increase / decrease in applied voltage.

FIG. 1 shows an electric circuit diagram of the control device for the piezoelectric actuator. This device includes a piezoelectric actuator 1, a current detection resistor 4, a high voltage power source 5 as a charging power source, a control circuit 6, a position sensor 7, a differential amplifier circuit 8 as a control means, a positive half-wave rectification circuit 9, and a negative signal. Inversion half-wave rectifier circuit 10
A charging current control amplifier circuit 11, a discharge current control amplifier circuit 12, a charge signal transmission circuit 13, and a discharge signal transmission circuit 14.
The charging current adjusting circuit 15, the discharging current adjusting circuit 16, the charging current detecting circuit 17, and the discharging current detecting circuit 18 are provided.

A current detecting resistor 4 as a current detecting element is connected in series to the piezoelectric actuator 1, and the current detecting resistor 4 is grounded. The current detection resistor 4 is for detecting the charging current Icha and the discharging current Idis of the piezoelectric actuator 1 accompanying the charging / discharging operation of the piezoelectric actuator 1. Then, the current actually flowing in the piezoelectric actuator 1 is generated as an electromotive voltage of the current detection resistor 4, and a positive voltage is generated when the piezoelectric actuator 1 is being charged, and a negative voltage is being discharged. Occurs.

The charging current adjusting circuit 15 is composed of a FET 19 as a charging current adjusting means, a detection resistor 20, an operational amplifier 21 and resistors 22, 23, 24 and 25. The detection resistor 20, the FET 19 and the positive terminal of the high voltage power supply 5 are connected in series to the piezoelectric actuator 1,
The negative terminal of is grounded. The connection point a between the source terminal 19 a of the FET 19 and the detection resistor 20 is connected to the inverting input terminal of the operational amplifier 21 via the resistor 24. Furthermore, the output terminal of the operational amplifier 21 is a resistor 22.
Is connected to the gate terminal 19b of the FET 19 via the resistor 23 and negative feedback is applied via the resistor 23.

On the other hand, the discharge current adjusting circuit 16 comprises a FET 30 as a discharge current adjusting means, a detection resistor 31, an operational amplifier 32, and resistors 33, 34, 35 and 36. The piezoelectric actuator 1 has a FET 30 and a detection resistor 3
1 and 1 are connected in series, and the detection resistor 31 is grounded. Further, the source terminal 30a of the FET 30 and the detection resistor 31
The connection point b between and is connected to the inverting input terminal of the operational amplifier 32 via the resistor 35. Furthermore, operational amplifier 3
The output terminal of No. 2 is connected to the gate terminal 30b of the FET 30 via the resistor 33 and negatively fed back via the resistor 34.

The charging current detecting circuit 17 is an operational amplifier 4
1 and a diode 42 and a resistor 43.
Then, the charging current detection circuit 17 inputs the signal from the current detection resistor 4, half-wave rectifies only the positive signal, and outputs only the charging current value as a positive voltage value. Further, the discharge current detection circuit 18 includes an operational amplifier 44, a diode 45, resistors 46, 4
7 and 7. Then, the discharge current detection circuit 1
8 receives the signal from the current detection resistor 4, half-wave rectifies only the negative signal, and outputs only the rectified discharge current value as a positive voltage value.

The control circuit 6 outputs a command signal (target value signal) having a level corresponding to the target position Vcom of the piezoelectric actuator 1. The position sensor 7 detects the actual position Vfe associated with the expansion / contraction operation of the piezoelectric actuator 1 and outputs it as a feedback signal.

The differential amplifier circuit 8 includes an operational amplifier 48 and a resistor 4.
9, 50 and 51, the non-inverting input terminal of the operational amplifier 48 inputs the command signal from the control circuit 6, and the inverting input terminal of the operational amplifier 48 inputs the feedback signal from the position sensor 7. Then, the differential amplifier circuit 8 compares and amplifies the analog command value Vcom from the control circuit 6 and the feedback value Vfe from the position sensor 7 to generate a command value V.
When com is larger than the feedback value Vfe, a positive differential value is output, and when the command value Vcom is smaller than the feedback value Vfe, a negative differential value is output.

The positive half-wave rectifier circuit 9 is composed of an operational amplifier 52, a diode 53 and a resistor 54.
The signal from the differential amplifier circuit 8 is input to the second non-inverting input terminal. Then, the positive half-wave rectifier circuit 9 rectifies and outputs the output signal (differential value) from the differential amplifier circuit 8. The negative signal inversion half-wave rectifier circuit 10 is composed of an operational amplifier 55, a diode 56, and resistors 57 and 58.
The signal from the differential amplifier circuit 8 is input to the inverting input terminal of. Then, the negative signal inversion half-wave rectifier circuit 10 inverts the output signal (negative signal) of the differential amplifier circuit 8 to perform half-wave rectification.

The charging current controlling amplifier circuit 11 comprises an operational amplifier 59 and resistors 61, 62 and 63.
The non-inverting input terminal of the operational amplifier 59 of the charging current control amplifier circuit 11 inputs the signal from the positive half-wave rectifier circuit 9, and the inverting input terminal of the operational amplifier 59 inputs the signal from the charging current detection circuit 17. Then, the charging current control amplifier circuit 11 compares and amplifies the output voltage of the positive half-wave rectifier circuit 9 and the output voltage (charging current value) of the charging current detection circuit 17. The discharge current control amplifier circuit 12 is composed of an operational amplifier 60 and resistors 64, 65, 66.
The non-inverting input terminal of the operational amplifier 60 of the discharge current control amplifier circuit 12 inputs the signal from the negative signal inversion half-wave rectifier circuit 10, and the inverting input terminal of the operational amplifier 60 inputs the signal from the discharge current detection circuit 18. To do. Then, the discharge current control amplifier circuit 12 compares and amplifies the output voltage of the negative signal inversion half-wave rectifier circuit 10 and the output voltage (discharge current value) of the discharge current detection circuit 18.

The charge signal transmission circuit 13 comprises a constant voltage circuit 26, a photo coupler 27, and resistors 28 and 29. The constant voltage circuit 26 is connected to the non-inverting input terminal of the operational amplifier 21 via the resistors 28 and 25. Further, the phototransistor 27a of the photocoupler 27 is connected to the constant voltage circuit 26 via the resistor 28. Further, the output terminal of the charging current controlling amplifier circuit 11 (op amp 59) is connected to the constant voltage power supply Vcc via the light emitting diode 27b of the photocoupler 27 of the charging signal transmission circuit 13 and the resistor 29. On the other hand, the discharge signal transmission circuit 14 includes a constant voltage circuit 37, a photo coupler 38, and resistors 39 and 40. The constant voltage circuit 37 is connected to the non-inverting input terminal of the operational amplifier 32 via the resistors 39 and 36.
The phototransistor 38a of the photocoupler 38 is connected to the constant voltage circuit 37 via the resistor 39. Further, the output terminal of the discharge current control amplifier circuit 12 (op amp 60) is connected to the photo coupler 38 of the discharge signal transmission circuit 14.
Is connected to the constant voltage power supply Vcc via the light emitting diode 38b and the resistor 40.

Next, the operation of the piezoelectric actuator control device thus configured will be described. The differential amplifier circuit 8 uses the analog command value Vcom from the control circuit 6 and the position sensor 7
When the command value Vcom is larger than the feedback value Vfe, a positive differential value is output. If the command value Vcom is smaller than the feedback value Vfe, a negative differential value is output.

When the command value Vcom is larger than the feedback value Vfe, the output signal (differential value) from the differential amplifier circuit 8 is rectified by the positive half-wave rectifier circuit 9, and the circuit 11 at the latter stage on the charging side is rectified. , 13, 15 are activated. on the other hand,
When the command signal Vcom is smaller than the feedback signal Vfe, the output signal (negative signal) of the differential amplifier circuit 8 is inverted and half-wave rectified by the negative signal inversion half-wave rectification circuit 10, and the circuits 12 and 14 in the subsequent stage on the discharge side. , 16 are activated.

On the other hand, the current actually flowing in the piezoelectric actuator 1 is generated as an electromotive voltage of the current detection resistor 4, and is positive when the piezoelectric actuator 1 is being charged and negative when it is discharging. Occurs as the voltage of. The signal from the current detection resistor 4 is supplied to the charging current detection circuit 17
At, only the positive signal is half-wave rectified, and only the charging current value is output as a positive voltage value. Further, of the signals from the current detection resistor 4, only a negative signal is half-wave rectified in the discharge current detection circuit 18, and only the rectified discharge current value is output as a positive voltage value.

When the command value Vcom is larger than the feedback value Vfe, the output voltage of the positive half-wave rectifier circuit 9 in the current control amplifier circuit 11 and the charging current detection circuit 17 are set.
Output (charging current value) is compared and amplified, and half-wave rectifier circuit 9
The larger the signal of is larger than the signal of the charging current detection circuit 17, the larger the output voltage is. In addition, the discharge current control amplifier circuit 12
Then, similarly to the charging current control amplifier circuit 11, the output voltage also changes according to the amount of deviation when the command signal Vcom is smaller than the feedback signal Vfe. Therefore, the output voltage of the discharge current control amplifier circuit 12 increases as the signal of the negative signal inversion half-wave rectifier circuit 10 becomes larger than the signal of the discharge current detection circuit 18.

From the charging current control amplifier circuit 11,
Signal to the charging current adjusting circuit 15 in the signal transmission circuit 13.
Transmitted. That is, the constant voltage circuit 2 of the signal transmission circuit 13
6 is based on the electric potential of the piezoelectric actuator 1,
Connected to the collector of photocoupler 27 via resistor 28.
In addition, the light emitting diode 27b of the photocoupler 27 is
The node side is connected to the constant voltage power supply Vcc via the resistor 29.
Has been. Therefore, the charging current control amplifier circuit 11
The smaller the signal, the light emitting diode 2 of the photocoupler 27.
A large current flows through 7b, and the phototransistor 27a
Is close to saturation, the voltage V between resistors 25 and 28_AIs
descend. Also, the signal from the charging current control amplifier circuit 11
Is larger, the light emitting diode 27b of the photocoupler 27 is larger.
A small amount of current flows through the phototransistor.
27a becomes almost active, and the voltage V _ARises. That
And the voltage V of the charging signal transmission circuit 13_AIs small,
The gate voltage of the FET 19 of the charging current adjusting circuit 15 is low.
Only a small current flows through the FET 19. On the contrary, the voltage
V_AIs large, the gate voltage of FET19 is high and FE
A large current flows through T19. This current is the high voltage power supply
5 to the piezoelectric actuator 1 through the FET 19
The piezoelectric actuator performs an extension operation.

Here, an electromotive voltage is generated in the detection resistor 20 by the current flowing in the FET 19, and the operational amplifier 21 and the resistor 2 are connected.
FE is provided by the differential amplifier circuit composed of 3, 24 and 25.
The current flowing through T19 becomes stable. In addition, the charging current flowing through the piezoelectric actuator 1 via the FET 19 is fed back to the charging current control amplifier circuit 11 via the current detection resistor 4 and the charging current detection circuit 17 (a closed loop is formed). In this closed loop, the collector current may fluctuate due to the temperature characteristics of the photocoupler 27, or the FE
T19 gate-source voltage-drain current (V _GS −
Since the charge current of the piezoelectric actuator 1 has a temperature characteristic due to a signal from the positive half-wave rectifier circuit 9 due to the temperature characteristic of I _D ), it is used for correcting the charge current. For example, when the charging current does not flow when the signal from the positive half-wave rectification circuit 9 is large, the charging current detection circuit 1
Since the voltage of 7 is low, the temperature characteristic of the element is corrected by the current control amplifier circuit 11, and the charging current is made to flow stably in a wide temperature range.

Similarly, when the output of the operation amplification circuit 8 is negative, a signal corresponding to the magnitude is output by passing through the negative signal inversion half-wave rectification circuit 10, and in the discharge current control amplification circuit 12. It is compared with the value from the discharge current detection circuit 18, and a signal corresponding to the difference is sent to the discharge current adjustment circuit 16 via the discharge signal transmission circuit 14. Then, the FET 30 of the discharge current adjusting circuit 16 is controlled to control the control circuit 6
A discharge current corresponding to the deviation between the command value from the position sensor 7 and the feedback value from the position sensor 7 and the deviation from the value from the discharge current detection circuit 18 is applied to the piezoelectric actuator 1.

As a result, as shown in FIG. 3, the command value Vco
When m is larger than the feedback value Vfe, the charging current is increased or decreased depending on the magnitude of the deviation, and the piezoelectric actuator 1
It is possible to prevent overshoot and chattering that occur due to the operation delay of, and to perform a fast extension motion. When the command signal Vcom is smaller than the feedback signal Vfe, the discharge current of the piezoelectric actuator 1 is increased / decreased depending on the magnitude of the deviation, and the same effect as the charging side is obtained. In this way, the charging / discharging current is varied depending on the magnitude of the command signal Vcom and the feedback signal Vfe, and stable positioning is performed.

As described above, in this embodiment, the FET 19 (charging current adjusting means) is connected between the high voltage power source 5 (charging power source) for generating a positive voltage and the piezoelectric actuator 1, and the piezoelectric actuator 1 is connected to the FET 30 (charging current adjusting means). Discharge current adjusting means) is connected, and the position sensor 7 detects a value (position) according to expansion and contraction of the piezoelectric actuator 1, and the differential amplifier circuit 8 (control means) uses the position sensor 7 to operate the piezoelectric actuator 1. The deviation between the position of and the target value of the piezoelectric actuator 1 is obtained, and the FETs 19 and 30 are controlled so that the charging / discharging current corresponds to the deviation. As a result, it is possible to prevent overshoot and chattering that occur due to the operation delay of the piezoelectric actuator 1 and control the piezoelectric actuator with high speed and high accuracy.

The present invention is not limited to the above-described embodiment. For example, when a piezoelectric actuator is applied to a hydraulic system (when the hydraulic pressure is increased or decreased by expanding or contracting the piezoelectric actuator), the position sensor 7 is not used. Alternatively, a hydraulic sensor may be used. Further, when controlling the piezoelectric actuator according to the injected charge amount, a charge detection sensor may be used instead of the position sensor 7.

[0029]

As described in detail above, according to the present invention,
It has the excellent effect of controlling the piezoelectric actuator at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration of a piezoelectric actuator control device according to an embodiment.

FIG. 2 is a diagram showing a piezoelectric actuator.

FIG. 3 is a time chart.

FIG. 4 is a diagram showing a relationship between a voltage applied to a piezoelectric actuator and a displacement amount.

FIG. 5 is a diagram showing a relationship between an injection charge amount and a displacement amount of a piezoelectric actuator.

FIG. 6 is a diagram showing an electrical configuration of a conventional piezoelectric actuator control device.

FIG. 7 is a time chart of a conventional piezoelectric actuator control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 5 High-voltage power supply as charging power supply 7 Position sensor 8 Differential amplifier circuit as control means 19 FET as charge current adjusting means 30 FET as discharge current adjusting means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinrou Oda 1-1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. A charging current adjusting means connected between a charging power source that generates a positive voltage and a piezoelectric actuator, a discharging current adjusting means connected to the piezoelectric actuator, and a method according to expansion and contraction of the piezoelectric actuator. A sensor for detecting a value, a deviation between a value corresponding to expansion and contraction of the piezoelectric actuator by the sensor and a target value of the piezoelectric actuator is obtained, and the charging / discharging current adjusting means and the discharging current are adjusted so that the charging / discharging current corresponds to the deviation. A control device for a piezoelectric actuator, comprising: a control means for controlling an adjusting means.