JPS6113246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a servo motor drive circuit, and particularly to a servo motor drive circuit that converts various input control voltages that change in different directions with respect to a target value into voltages that change in a predetermined direction. .

When adjusting circuit components that require adjustment after wiring, such as oscillation coils, variable resistors, semi-fixed variable resistors, etc. placed on a printed circuit board, conventionally the operator manually adjusts them using a screwdriver while watching meters. Adjustments were made by turning the core, shaft, screws, etc. This has led to problems such as poor work efficiency, requiring skill, and variations in adjustment values. Therefore, automatic adjustment of the printed circuit board was made in which a driver rotated by a servo motor was used to turn the adjustment screws, etc., and the rotation of the driver was automatically stopped when the circuit components reached a predetermined adjustment value. Devices have been developed and are beginning to be put into practical use.

In such an automatic adjustment device, for example, the first
A servo loop as shown in the figure is constructed.

In FIG. 1, an adjustment screw 3 of a circuit component 2 that requires adjustment and is mounted on a printed circuit board 1 is rotated by a driver 5 driven by a servo motor 4. As shown in FIG.
Due to this rotation, when the circuit component 2 is a variable resistor or a semi-fixed variable resistor, its resistance value changes, and when the circuit component 2 is an oscillation coil, its inductance or oscillation frequency changes. This change is caused by the predetermined wiring pattern 6 of the printed circuit board 1,
7 and added to processor 8.
The processor 8 outputs a control voltage whose level changes according to the above change, and this control voltage is amplified by an amplifier 9 and applied to the motor 4, whereby the motor 4 is rotated in the forward or reverse direction. . When the control voltage reaches a preset target value, the rotation of the motor 4 is stopped and the circuit component 2 is adjusted to a predetermined value.

In the servo circuit as described above, the control voltage applied from the processor 8 to the motor 4 via the amplifier 9 is as shown in FIG.
It undergoes various different changes as shown in B and C. That is, there are cases such as A in which the control voltage increases as the motor 4 rotates in the forward direction, B in which the control voltage decreases in the opposite way to A, and C in which the control voltage has a peak value. Note that these control voltages A, B, and C are all changed toward the target value by rotating the motor 4 in the forward or reverse direction.

However, if different servo loops are constructed for various changes in the control voltage, the circuit becomes extremely complicated.

The present invention is intended to solve the above problems,
A control voltage and a target value voltage are applied to the differential amplifier, the magnitude of these voltages is detected, and the two voltages applied to the differential amplifier are switched at the input terminal based on this detection signal. This is what I did.

Hereinafter, an embodiment in which the present invention is applied to the above-mentioned automatic adjustment device for a printed circuit board will be described with reference to the drawings.

In FIG. 3, various control voltages as shown in FIGS. 2A, B, and C are applied to the input terminal 11 depending on the type of circuit component to be adjusted by the processor 8 in FIG. Further, a voltage E _A serving as the target value shown in FIG. 2 is applied to the input terminal 12. This voltage E _A is connected to analog switches 13 and 14 and voltage comparator 17.
is applied to one side input terminal. Further, the above control voltage is controlled by analog switches 15, 16 and voltage comparator 1.
It is added to the + side input terminal of 7. Voltage comparator 17
outputs a high level signal when the control voltage is greater than the target value voltage E _A , and outputs a low level signal when it is smaller. This output signal is directly applied to the gates of analog switches 13 and 15, and
The level of the signal is inverted by an inverter 18 and applied to the gates of analog switches 14 and 16. Analog switches 13, 14, 15, and 16 are configured to close when a high level signal is applied to their gates. Therefore, when the control voltage is greater than E _A , a high level signal is obtained from the voltage comparator 17 and the analog switches 13 and 15
When only the analog switches 14 and 16 are closed and the control voltage is lower than E _A , a low level signal is obtained from the voltage comparator 17, which is inverted by the inverter 18 to become a high level signal, so only the analog switches 14 and 16 are closed. It can be done.

When the analog switches 13 and 15 are closed, the analog switch 13 passes the voltage E _A and applies it to the + side input terminal of the differential amplifier 19, and the analog switch 15 passes the control voltage and applies it to the differential amplifier 19. It is added to the negative input terminal of the amplifier 19. Therefore, in this case, since the control voltage is greater than E _A , an output voltage that always changes on the negative side is obtained at the output side of the differential amplifier 19.

When the analog switches 14 and 16 are closed, the analog switch 14 passes the voltage E _A and applies it to the negative input terminal of the differential amplifier 19, and the analog switch 16 passes the control voltage and applies it to the differential amplifier 19. Add it to the + side input terminal of the width filter 19. Therefore, in this case, since the control voltage is smaller than E _A , an output voltage that always changes on the negative side is obtained at the point. 4A, B, and C show changes in the output voltage of the differential amplifier 19 obtained by the above-described operation, corresponding to FIGS. 2A, B, and C. As is clear from Fig. 4, for the various control voltages in Fig. 2 A, B, and C, the voltages in Fig. 4 A, B, and C all take OV as the maximum value, and this maximum value is set as the target value. It is converted into a changing negative voltage.

The output voltages shown in FIGS. 4A, B, and C are then applied to the negative input terminal of the differential amplifier 20. A reference voltage E _B is applied to the + side input terminal of the differential amplifier 20 to provide a differential with the output voltage. Therefore, the output terminal 21 of the differential amplifier 20 has the output voltages A, B, and C in FIG. 5 for each of the output voltages A, B, and C in FIG.
The voltage E _B as shown in B and C is taken as a minimum value, and a positive output voltage that changes with this minimum value as a target value is obtained. In this case, the voltage range from OV to voltage E _B becomes the dead zone of the servo motor.

In FIGS. 5A, B, and C, when the output voltage is decreasing, that is, when the change in voltage is negative, the target value is automatically reached by rotating the motor in the positive direction. Further, when the output voltage is increasing, that is, when the change in voltage is positive, the target value is automatically reached by switching the polarity of the motor and rotating it in the opposite direction.

Next, an embodiment of the above polarity switching circuit will be described with reference to FIG.

In FIG. 6, the input terminal 21 is common to the output terminal 21 in FIG. 3, and the output voltage of FIG. 5 A, B, C (hereinafter referred to as input voltage for FIG. is added. This input voltage is applied to analog switches 24 and 25 as well as to the + side input terminal of delay circuit 26 and voltage comparator 27. The output side of the analog switch 24 is connected to the negative input terminal of the differential amplifier 28 and also to the input side of the analog switch 23. The output side of the analog switch 25 is connected to the + side input terminal of the differential amplifier 28 and also to the input side of the analog switch 22. Further, the output sides of the analog switches 22 and 23 are grounded. The delay circuit 26 and the voltage comparator 27 constitute a rate of change determination circuit 29 for determining whether the changes in the input voltages shown in FIGS. 5A, B, and C are positive or negative, and the output of the delay circuit 26 is the voltage It is applied to the negative input terminal of the comparator 24. The voltage comparator 27 compares the input voltage with the delayed input voltage.
As a result, a low level signal is output when the input voltage changes negatively, and a high level signal is output when the input voltage changes positively. This low level or high level signal is applied to the trigger terminal of flip-flop 31 through a three-input OR gate 30. This flip-flop 31 is inverted by the high level signal and the output Q becomes high level. Therefore, when the input voltage changes negatively and a low level signal is output from the voltage comparator 27, the flip-flop 31 is not inverted and the output Q remains at a low level. This low level output Q is inverted by the inverter 23 to become a high level signal, and this signal causes the analog switches 23, 2
5 is closed. As a result, the input voltage is applied to the + side input terminal of the differential amplifier 28 through the analog switch 25, and this differential amplifier 28
The negative input terminal of the analog switch 23 is grounded through the analog switch 23. As a result, an amplified positive input voltage appears at the output side of the differential amplifier 28, and this voltage is further amplified by the amplifier 9 and applied to the motor 4 as a control voltage. Therefore, this motor 4 rotates in the forward direction. When the control voltage reaches the target value, the motor 4 is stopped and the adjustment is completed.

Also, if the input voltage is a positive change, the voltage comparator 2
When a high level signal is output from the flip-flop 7, the flip-flop 31 is inverted and the output Q becomes a high level inversion instruction signal. This high level output Q causes analog switches 22 and 24 to close. This causes the input voltage to change to analog switch 2.
4 to the negative input terminal of the differential amplifier 28, and the positive input terminal of the differential amplifier 28 is grounded through the analog switch 22. As a result, a negative input voltage obtained by inverting and amplifying the positive input voltage appears at the output side of the differential amplifier 28, and this voltage is further amplified by the amplifier 9 and is used as a control voltage for the motor 4. , which causes this motor 4 to rotate in the opposite direction. When the control voltage reaches the target value, the motor 4 is stopped and the adjustment is completed.

Note that a reversal instruction signal, which will be described later, is applied to the other terminal 39 of the OR gate 30 after the adjustment is completed, and a high-level reversal instruction signal is applied to the other terminal 33 when necessary, such as when an overload occurs during adjustment. A signal is added.

FIG. 7 shows changes in the output voltage at points during forward rotation and reverse rotation obtained by the above-described operation.

Next, after the adjustment is completed, the following problems occur. In FIG. 8A, it is assumed that the tip 5a of the driver fitted into the driver groove 3a of the adjustment screw 3 of the circuit component that now needs adjustment is rotated in the clockwise direction indicated by the arrow and then stopped. In this state, the tip portion 5a of the driver is brought into pressure contact with the driver groove 3a at a point due to the force generated during rotation, so that they are in contact with each other. Therefore, if the driver tip 5a is pulled up from this state, it will be difficult to remove it from the driver groove 3a, and the adjustment screw 3 will rotate slightly due to the pulling force, causing the adjustment to be out of order. To prevent this, as shown in FIG. 8B, after completing the adjustment, rotate the motor 4 slightly in the reverse direction, rotate the driver tip 5a slightly counterclockwise as shown by the arrow, and move it away from the point in FIG. All you have to do is make sure it's well separated from the ground before you pull it up.

Next, an embodiment for slightly reversing the motor 4 after the above adjustment is completed will be described with reference to FIG. 9.

FIG. 9 shows the circuit of FIG. 6 with a voltage comparator 34, an inverter 35, monomultis 36 and 37, and an analog switch 38 added.

Completion of the adjustment can be detected by the fact that the output voltage at the point of the differential amplifier 19 in FIG. 3, that is, the output voltages in FIGS. 4A, B, and C, have become zero. Therefore, in FIG. 9, the voltage at the above point is added to the negative input terminal of the voltage comparator 34 and is compared with the ground potential of the positive input terminal. Therefore, when the adjustment is completed and the voltage at the point becomes zero, the voltage comparator 34
A lower level signal is output and inverted by an inverter 35. This inverted high level signal inverts the flip-flop 31 through the OR gate 30, and the high level output Q is applied to the analog switches 22 and 24 as an inversion instruction signal. As a result, the output voltage of the differential amplifier 28 is inverted in the same manner as described with reference to FIG. At this time, the output voltage is, for example, approximately 1V, which is approximately equal to the magnitude of E _B. On the other hand, the high level signals from the inverter 35 have a time constant τ connected in series with each other.
The signal is delayed by a monomulti 36 with a time constant of ₁ and a monomulti 37 with a time constant τ ₂ , and is applied to the gate of an analog switch 38. As a result, the analog switch 38 is set to τ after the reversal instruction signal is output.
₁ and then opened for a time τ _2. As a result, the motor 4 is reversed for a time τ ₂ and then stops. Incidentally, when the adjustment is completed, the rotation of the motor 4 is very slow, so that the above-mentioned reverse rotation is only slightly performed, resulting in the state shown in FIG. 8B. Therefore, by pulling up the driver tip 5a, it can be easily separated from the driver groove 3a, and the adjustment will not be disturbed.

The invention provides a first differential amplifier 19 to which a control voltage and a target value voltage are applied to its two input terminals.
and first switching means 13 to 16 for mutually switching the control voltage and the target value voltage applied to the two input terminals of the first differential amplifier, and the control voltage and the target value voltage. a comparing means 17 for comparing the voltages and controlling the first switching means according to the comparison result; and a comparing means 17 for controlling the first switching means according to the comparison result; a second differential amplifier 28 and a second differential amplifier 28 that mutually exchanges the output voltage of the first differential amplifier and the reference voltage applied to the two input terminals of the second differential amplifier; detecting an increase or decrease in the output voltage of the switching means 22 to 25 and the first differential amplifier;
A servo motor comprising detecting means 22 to 25 for controlling the second switching means according to the detection thereof, and controlling the motor by the output voltage of the second differential amplifier. This relates to the drive circuit.

Therefore, according to the present invention, various control voltages having different directions of change as shown in FIG. 2, for example, are changed in the same direction as shown in FIG. It can be converted into a motor drive voltage that instructs forward or reverse rotation.

[Brief explanation of drawings]

Figure 1 is a schematic system diagram of a printed circuit board automatic adjustment device to which the present invention can be applied, Figure 2 is a diagram showing changes in various control voltages, and Figure 3 is a diagram showing changes in the various control voltages mentioned above in the same direction. FIG. 4 is a diagram showing changes in the output voltage at the points in FIG. 3, and FIG. 5 is a diagram showing changes in the output voltage at the output terminal in FIG. 3. , Fig. 6 is a block diagram of the motor polarity switching circuit, Fig. 7 is a diagram showing changes in the output voltage at the points in Fig. 6, and Fig. 8 A, B.
9 is a plan view showing the relationship between the driver and the adjusting screw after adjustment is completed, and FIG. 9 is a block diagram showing an embodiment for reversing the motor after adjustment is completed. In addition, in the symbols used in the drawings, 3 is an adjustment screw, 4 is a servo motor, 5 is a driver, and 8
is a processor, 9 is an amplifier, 13, 14, 15,
16 is an analog switch, 17 is a voltage comparator, 1
9 is a differential amplifier.

Claims (1)

[Claims] 1. A first differential amplifier to which a control voltage and a target value voltage are applied to its two input terminals; a first switching means for switching the control voltage and the target value voltage; a comparison means for comparing the control voltage and the target value voltage and controlling the first switching means according to the comparison result; a second differential amplifier in which the output voltage of the first differential amplifier and a reference voltage are applied to its two input terminals; a second switching means for switching the output voltage of the first differential amplifier and the reference voltage; detecting an increase or decrease in the output voltage of the first differential amplifier; A servo motor drive circuit comprising: detecting means for controlling the second switching means, the motor being controlled by the output voltage of the second differential amplifier.