JPS5828242Y2 - Servo mechanism - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a servo mechanism using a pulse motor used in a self-balancing recorder or the like.

In general, in a servo mechanism using a pulse motor, regardless of the magnitude of the deviation between the input signal voltage and the feedback voltage, if the deviation exceeds the dead band, the pulse motor will generate pulses with a constant frequency close to its maximum self-starting frequency. being driven.

Therefore, when the input changes slowly, the pulse motor repeats full-speed rotation and stopping several steps at a time, which has the disadvantage that the pointer of the recorder and the recorded results are shaky or fluffy, as shown in FIG. 2A.

Furthermore, since the pulse motor rotates at full speed when the noise voltage exceeds the dead zone, there is a drawback that the shaft of the pulse motor tends to become jittery due to the noise.

In order to eliminate such defects, conventionally, one voltage-controlled variable frequency oscillator is used to obtain a pulse output with a frequency proportional to the absolute value of the deviation voltage.This pulse output is controlled according to the polarity of the deviation. There is a device in which the pulse motor is applied to the pulse motor drive circuit through a gate.

However, voltage-controlled variable frequency oscillators have complex circuit configurations and cannot have a wide variable frequency range, making it difficult to stably output ultra-low frequencies in particular, resulting in unstable operation when the input signal changes slowly. In some cases, an absolute value detection circuit to extract the absolute value of the deflected deviation, a 2(VA) comparator and a 2s1 gate circuit controlled by its output, etc. to determine the polarity of the deviation are required, and the overall The disadvantage is that the configuration is complicated.

The purpose of the present invention is to realize a servo mechanism using a pulse motor that has stable operation even when the input changes slowly and has a simple overall configuration.

FIG. 1 is a block diagram showing one embodiment of the servo mechanism of the present invention.

In the figure, 1 is a terminal to which an input signal voltage Ei is applied, 2 is a circuit that generates a feedback voltage Ef, 3 is a comparison amplifier that compares the input signal voltage Ei and the feedback voltage Ef and amplifies the deviation;
4 (ri Comparison amplifier output Ea is divided into two currents with constant current characteristics corresponding to their polarity and size i 1 > i2
A voltage-current converter using two common-base transistors, 5 and 6 each having a frequency f1. A pulse oscillator using a unijunction transistor generates a pulse output of f2, and 7 is a pulse motor drive circuit that rotates the pulse motor 8 forward or reverse depending on the pulse output from the pulse oscillator 5 or 6.

The amount of rotation of the pulse motor 8 is applied to the feedback voltage generation circuit 2, which generates a feedback voltage Ef corresponding to the amount of rotation.

In the servo mechanism of the present invention configured as described above, when the input signal voltage Ei is smaller than the feedback voltage Ef, the deviation ε is negative, and the comparison amplifier output Ea becomes negative, the voltage-current converter 4 generates a current 11 with constant current characteristics. , the pulse oscillator 5 starts oscillating, and a pulse having a frequency f1 corresponding to the deviation ε is applied to the pulse motor drive circuit 7 to reverse the pulse motor 8.

As a result, when the feedback voltage Ef becomes smaller and becomes balanced with the input signal voltage Ei, the pulse oscillator 5 stops oscillating, and the pulse motor 8 stops rotating.

Next, the input signal voltage Ei becomes larger than the feedback voltage Ef and the comparison amplifier output Ea becomes positive, the voltage-current converter 4 generates a current 12 with constant current characteristics, the pulse oscillator 6 starts oscillating, and the frequency f2 corresponding to the deviation ε When a pulse is applied to the pulse motor drive circuit 7, the pulse motor 8 rotates normally.

Accordingly, the feedback voltage Ef increases and the input signal voltage E
When balanced with i, the pulse oscillator 6 stops oscillating and the pulse motor 8 stops rotating.

In this way, the drive frequency of the pulse motor 8 is made to correspond to the deviation, so even if the input changes slowly, it is possible to eliminate jitter and fuzz in the recorder pointer and the recorded results, as shown in Figure 2. can.

Further, even if the noise voltage exceeds the dead zone, if the magnitude is not large, the drive frequency of the pulse motor is low, so the shaft of the pulse motor 8 is less likely to wobble, and is resistant to noise.

Furthermore, since there is a proportional band, the loop gain can be increased and the minimum detection sensitivity can be increased.

In addition, the voltage-current converter uses two common-base transistors to convert the deviation voltage into two currents with constant current characteristics corresponding to the polarity and magnitude, and the circuit configuration is simple, the variable frequency range is wide, and the ultra-low Since it is combined with two oscillators using unijunction transistors that output stably regardless of the frequency, the operation is stable even when the input signal changes slowly, and the overall configuration can be simplified.

Its specific configuration is shown in FIG.

FIG. 3 is a connection diagram showing a specific embodiment of the servo mechanism of the present invention.

In the figure, R8 is a 24V DC power supply, for example, and is the only power supply for this servo mechanism.

Q 1tri) transistor, Zener diode D
21 constitutes a regulator circuit that provides a stable voltage E8 of, for example, 12V to the common line l.

A circuit 2//'i for generating the feedback voltage Ef is illustrated as consisting of a magnetically balanced displacement electric transducer.

That is, a movable permanent magnet M is disposed so as to be displaceable within the central gap of a saturable iron core T having a shape as shown in FIG. The rotating shaft of the movable permanent magnet M is connected to the rotating shaft of the pulse motor 8.

If there is a difference Aφ between the magnetic flux φm caused by the movable permanent magnet M and the magnetic flux φf caused by the current flowing through the feedback coil Wf,
An alternating current voltage is induced in the detection coil Wd.

This voltage is applied to transistor Q2. Since the half-wave AC output current ie is amplified by Q3 and is positively fed back to the exciting coil wb, it self-oscillates at a frequency (approximately 2 KHz) determined by the constant of the tuning circuit of the detection coil Wd and capacitor C1. , constitutes an oscillation amplifier circuit.

The output of this oscillation amplifier circuit is rectified and smoothed, and then amplified and energized by transistors Q4 and Q5 to become a DC output current Io.

Output current (i) o/l'i is supplied to the feedback coil Wf so that the magnetic flux difference Aφ becomes small.

Since the gain of this oscillation amplifier circuit is sufficiently large, the difference lφ in magnetic flux becomes substantially zero, and the magnetic fluxes φm and φf are balanced.

Therefore, the output current Io corresponds accurately to the amount of displacement of the movable permanent magnet M.

This output current IO flows to the load resistance RL and the common line l
A feedback voltage Ef is generated based on .

When the feedback voltage generation circuit 2 is configured using a magnetically balanced displacement electric converter in this way, a permanent magnet can be used in the movable part, and the entire converter can be made contactless and extremely stable. Therefore, a highly reliable feedback voltage generation circuit can be obtained.

Furthermore, when constructing a displacement electric converter using a self-oscillating amplifier circuit as described above, there is an advantage that the entire configuration can be extremely simple without requiring a separate AC power supply or oscillator, and the servo mechanism can be integrated into a single unit. This is suitable for operation with a DC power source.

The comparison amplifier 3 includes a differential input operational amplifier OP and a resistor R.
3 to R6, and resistors R1 and R2 that constitute the input filter F.
, a capacitor C2, and voltage dividing resistors R7 and R8.

Operational amplifier OP receives input signal voltage Ei via input filter F and resistors R3 and R4 in a differential circuit.

A resistor R is connected to one input terminal (G) of the operational amplifier OP.
A feedback voltage Ef based on the common line l is applied to the other input terminal (c) through the input terminal 6, and a voltage obtained by dividing the output voltage Ea based on the common line l by voltage dividing resistors R7 and R8 is applied to the other input terminal (c). Negative feedback is provided via resistor R5 to operational amplifier 0.
It operates using the potential EB of the PIl-i common line 1 as a reference level.

Therefore, the 24V of DC power supply E8 applied to the power supply terminal
The points O and O have positive and negative potentials with respect to the reference level EB, and the positive and negative power supplies necessary to operate the operational amplifier OP are obtained from the DC power supply E.

In this way, in this embodiment, the operational amplifier, which generally requires dual positive and negative sources, can be driven with only a single DC power source E8, thereby simplifying the configuration of the power supply circuit.

At the output terminal of the operational amplifier OP, an output voltage Ea based on the common line l is obtained as shown in the following equation.

a K((Ei+ECM)-Ef-EOM) K(Ei-Ef) ・・・・・・(1
) However, % E CM : Common mode noise between input signal voltage Ei (→ side and ground, R1 + R3 = R2 + R4, R5 = R6 = RR6) RL In equation (1), the EcMO term is not included, so it is common mode noise. The operational amplifier OP can eliminate the influence of input signal voltage Ei at any level.
i can receive it.

This comparison amplifier output Ea is applied to the voltage-current conversion circuit 4.

The voltage-current conversion circuit 4 includes a voltage-current conversion resistor R0, a common base transistor Q6. Q7, a level shift transistor Q8, and resistors R10 and R1□.

A current equal to the comparator amplifier output Ea divided by the voltage-current conversion resistor R0 flows through the emitter of the transistor Q6'* or Q7.

Transistor Q6. Ql;j Since it constitutes a common base circuit, its collector current has a constant current characteristic that is approximately equal to the emitter current.

By the way, since a voltage VBE□tVBE2 exists between the emitter and base of the transistors Q6 and Q7, no output current is generated at the collector unless the comparison amplifier output Ea exceeds these values.

This base-emitter voltage provides a dead zone for the servo mechanism.

When the comparator output Ea is positive with respect to the common line l and exceeds VRWI, a current ia flows through the emitter of the transistor Q6, and a collector current 12 approximately equal to this is generated.

On the other hand, when the comparator output Ea is negative with respect to the common line l and exceeds VBE2, a current ia flows through the emitter of the transistor Q7, and a collector current substantially equal to this flows through the resistor R1o.

Transistor Q7 and level shift transistor QB
hfe is very large and assuming that each base current is zero, the collector current 11 of the transistor Q8 becomes as shown in the following equation.

However, BE3: Base-emitter voltage of transistor Q8, Therefore, by adjusting the resistor R1 (MRI□O ratio, the current 1 at the positive saturation value of the comparison amplifier output Eg
2 and the current 11 at the negative saturation value can be made equal.

The voltage-current converter 4 can obtain two currents j1)i2 having constant current characteristics proportional to the polarity and magnitude of the comparison amplifier output Ea.

The value of the current 11t12 can be adjusted by the value of the resistor R0.

These two currents jl) 12 with constant current characteristics are applied to the pulse oscillator 5 or 6, respectively.

The pulse oscillator has the same configuration using a 5.6F'i unijunction transistor (hereinafter referred to as UJT).

The pulse oscillator 5 (6) generates a current 11 (i
2), and when the terminal voltage reaches the peak point voltage ■P1 (vP2) of the UJT, the UJT turns on and the charge stored in the capacitor is discharged via the resistor R12 (R13), and the resistor R1° A positive pulse voltage as shown in FIG. 3 is generated at (R13).

When the capacitor is discharged, the UJT is turned off again, the capacitor is charged again and the above operation is repeated, and the current 11
The repetition frequency f1 (f2) is proportional to the magnitude of (i2)
) produces a relaxation oscillation.

Since the current i□, 12 has a constant current characteristic, the current 1
1j12 remains unchanged.

Therefore, the oscillation frequencies fl and f2 of the pulse oscillators 5 and 6
G'i is approximately proportional to the magnitude of the comparison amplifier output Ea, and is expressed by the following equation.

However, ■D4. ■D5: Contact potential of diode between vine and base of UJT Frequency f1 of this pulse oscillator 5, 6. A pulse output f2 is applied to the pulse motor drive circuit 7.

In this way, two
Since the oscillator is driven by the two current outputs of the voltage-current converter, it has a very simple configuration using only three transistors, two solid unijunction transistors, a few resistors, and a capacitor. Variable frequency pulse output can be obtained.

When the pulse motor drive circuit '7 receives the pulse output of the pulse oscillator 50 with a frequency f1, it reversely rotates the four-phase two-excitation type pulse motor 8 in synchronization with the number of pulses, and with respect to the frequency f2 of the pulse oscillator 6, Rotate it forward.

Four sets of modes are required to excite the four phases of the pulse motor 8.

The truth table is shown below.

When 2-bit level signals ql and q2 are made to correspond to the four sets of modes for exciting these four phases, the logical equation becomes as follows.

a=q1q2+qlq2=c b=q"(12+q"(12=d...)
・(4) C: q1q2+qlq2:ad=qlq2+q1q2=b The excitation mode for normal rotation of the pulse motor changes in the order of I→■→■→■→■.

Therefore, the carry of the level signal q2 is performed when the level of the level signal q1 changes from 1 to 0 (1→0).

Also, since the reversal excitation mode changes in the order of I→■→■→■→I, the shift of level signal q2 is performed when the level of level signal q1 changes from O to 1 (0→1). .

In this embodiment, these logic circuits are constructed by a two-package two-man powered four-Nando game A2°A4, an open collector output 2-input canand gate A5 and a JK flip 70 tube A3 each in one package.

A timing chart of each of these circuits is shown in FIG.

Note that various other configurations of the logic circuit of the pulse motor drive circuit 7 can be used as necessary.

Since the pulse oscillators 5 and 6 are constructed using UJTs and produce positive pulse outputs, they are convenient for driving logic circuits.

As explained above, in this invention, in order to adjust the drive frequency of the pulse motor to the deviation, two common-base transistors are used to convert the deviation voltage into two currents with constant current characteristics corresponding to the polarity and magnitude of the deviation voltage. This is achieved by combining the voltage-current converter used and two pulse oscillators using unijunction transistors, so operation is stable even when the human input signal changes slowly, and the dead zone is made up of two common-base transistors. It is possible to realize a servo mechanism using a pulse motor that is completely stable with a pace-emitter voltage of 1, and has a simple overall configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the servo mechanism of the present invention, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a connection diagram showing a concrete configuration of the servo mechanism of the present invention, and Fig. FIG. 4 is a configuration explanatory diagram showing an example of a displacement electric converter used in the servo mechanism of the present invention, and FIG. 5 is a timing chart of the servo mechanism of the embodiment shown in FIG. 1...Terminal to which input signal voltage Ei is applied, 2...
...Circuit that generates feedback voltage Ef, 3...
Comparison amplifier, 4... Voltage-current converter, 5, 6.
...Pulse oscillator, 7...Pulse motor drive circuit, 8...Normal motor.

Claims (1)

[Scope of utility model registration request] It has an amplifier that compares and amplifies the input signal voltage and the feedback voltage, and two common-base transistors to which the output voltage of the comparison amplifier is commonly applied to the emitter through a resistor, and the polarity and magnitude of the output voltage of the comparison amplifier are a voltage-current converter that converts into two currents with corresponding constant current characteristics; two oscillators using unijunction transistors that generate pulse outputs of frequencies corresponding to the two current outputs of the voltage-current converter; A servo mechanism comprising a pulse motor drive circuit that rotates the pulse motor in the forward or reverse direction according to pulse outputs from these two oscillators, and a circuit that generates a feedback voltage according to the rotation of the pulse motor. .