JPS6143777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital servo device in a recording/reproducing device, and by configuring another integral loop in the digital calculation section in addition to the phase control system, it is possible to control the phase caused by external disturbances such as torque fluctuations. It is an object of the present invention to provide a digital servo device for a recording/reproducing device that can completely eliminate the deviation of the control signal from the reference value and control the rotation of the motor so that the phases of the control signal and the reference signal are always equal.

In general, constant speed rotation servo systems for motors include analog servo systems that use analog signals for each circuit making up the servo system, and digital servo systems that use digital signals. Compared to analog servo systems, digital servo systems can reduce the number of resistors, capacitors, etc. used, and therefore have a simpler circuit configuration. It has the advantages of being small and highly reliable, as it uses highly stable clock pulses as a medium, which greatly reduces drift, and since it handles digital information, it is less susceptible to the effects of unnecessary signal weight. There is also a significant improvement from the viewpoint of weight reduction. However, the conventional digital servo system is similar in principle to the analog servo system, and requires circuits such as a phase comparator, a frequency discriminator, a phase modulator, and a frequency modulator.

Furthermore, in the conventional servo system, when the motor load condition is constant, the deviation of the motor's rotational phase from the reference value is zero, but when disturbances such as torque fluctuations are added, the motor's rotational speed changes to the reference value. Although it is equal to the rotational speed, the phase has the drawback that deviations from the reference value constantly occur.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of an embodiment of a digital servo device in a recording/reproducing apparatus according to the present invention. In the figure, 1 is a controlled motor, one rotating shaft is used as a capstan 2, and at one end of the other rotating shaft, magnets with S and N poles are arranged alternately on the circumferential surface at equal intervals. A disk 3 provided thereon is mounted and fixed. Further, a detection head 4 is provided with a gap surface at a position facing and away from a magnet disposed on the circumferential side of the disc 3, and the disc 3 rotates integrally with the rotation of the motor 1.
Each time the magnet crosses in front of the detection head 4, a substantially sinusoidal signal having a repetition frequency proportional to the rotational speed of the motor 1 is outputted from the detection head 4. This approximately sinusoidal signal is converted into a pulse train by the pulse forming circuit 5 and then supplied to the 1/2 frequency divider 6, where conversion errors in the pulse forming circuit 5 are prevented from occurring and the signal is converted into a symmetrical square wave.

This symmetrical square wave is a square wave f having a repetition frequency proportional to the rotational speed of the motor 1 and has a waveform as shown in FIG. At the same time, it is applied to the reset terminal of the binary counter 9 in the microcomputer 8 as a reset pulse.

On the other hand, a control signal of a constant frequency (for example, 30 Hz) is recorded at a predetermined phase on the tape 10, which is held and driven by a capstan 2 and a pinch roller (not shown), in its running direction.
During reproduction, the recorded control signal is reproduced by the fixed control head 11. Therefore, the reproduction control signal from the control head 11 is reproduced at a frequency proportional to the running speed of the tape 10, and is supplied to the comparison signal forming circuit 12. The comparison signal forming circuit 12 is composed of a monostable multivibrator or the like, and forms a comparison signal b shown in FIG. 2B in synchronization with the reproduction control signal a shown in FIG. 2A from the control head 11.
Output to phase comparator 13.

On the other hand, the oscillation output of the crystal oscillator 14 is transmitted through the frequency divider 15.
After being divided into a constant frequency of, for example, 30 Hz, it is supplied to the reference signal generation circuit 16, where it is converted into a ramp wave reference signal c as shown in FIG. 2C having a constant frequency of, for example, 30 Hz. . This reference signal c is supplied to a phase comparator 13, where the phase is compared with the comparison signal b. That is, the phase comparator 13 samples and holds the slope part of the reference signal c during the low level period of the comparison signal b to obtain a signal d as shown in FIG. The voltage is applied to a voltage controlled oscillator (VCO) 17, and its output oscillation frequency is variably controlled. The VCO 17 is applied with the phase error signal d as a control voltage, and outputs an oscillating output signal e as shown in FIG.

The changeover switch 18 is connected to a fixed terminal 18a during reproduction by the recording/reproducing apparatus, and is connected to a fixed terminal 18b during recording. When the recording and reproducing apparatus performs reproduction, the output signal e of the VCO 17 is taken out from the common terminal 18c of the changeover switch 18 and applied to the other input terminal of the AND circuit 7. As a result, the AND circuit 7 gate outputs the output signal e of the VCO 17 only during the high level period of the rotation detection pulse f, and outputs the gate output signal g as shown in FIG. 2G.
is applied to the binary counter 9 as a clock pulse. Note that the clock pulse frequency is set sufficiently higher than the repetition frequency of the rotation detection pulse f to eliminate the generation of quantization noise in digital conversion, which will be described later, and to reduce the cost due to an increase in the counting capacity of the binary counter 9 and the required number of bits. The upper limit is limited in consideration of higher grades.

In this way, the binary count value N counted by the binary counter 9 is calculated by the microcomputer 8.
The digital calculation is performed as follows. This count value N is the number of clock pulses gated by the speed detection pulse f having a repetition frequency corresponding to the rotational speed of the motor 1, as shown in FIG. , and since the frequency of the clock pulse is varied by the phase error signal, the reference signal c
It is also a digital amount corresponding to the phase error between the phase of (reference phase) and the reproduction control signal a, and is calculated by subtracter 19 from the reference digital value _N is subtracted. As a result, the subtracter 19 outputs the error value N _E ( ₌ N - N _R ) as shown in _FIG .
In this embodiment, the signal is multiplied by K ₂ =1/2 ^M (M is an arbitrary integer) and then supplied to the accumulator 22 . The accumulator 22 sequentially adds the output digital values of the arithmetic unit 21 to the second
Their cumulative value N _I (=ΣK ₂・N
_E ), that is, the integrated digital value of the error value N _E is output and applied to the adder 23 .

The adder 23 outputs the cumulative value N _I and the binary counter 9.
The output count value N is added and outputted to the arithmetic unit 24, where it is multiplied by _K1 . Therefore, computing unit 2
The binary number N _p shown in Figure 2 K extracted from 4 is
It is expressed as K ₁ (N+N _I ) and is applied to the DA converter 25 as the output of the microcomputer 8.
The timing of the above digital calculation operation is such that it operates at the falling edge of the speed detection pulse f and is held during the low level period of the speed detection pulse f.

The binary number N _p obtained by digital calculation by the microcomputer 8 as described above is DA
The converter 25 performs digital-to-analog conversion to generate an analog voltage l as shown in FIG. Control.

In this way, in this embodiment, the motor 1, the disc 3, the detection head 4, the pulse forming circuit 5, the 1/2 frequency divider 6, the AND circuit 7, the binary counter 9, the adder 23, the arithmetic unit 24, and the DA In addition to the speed feedback loop consisting of the converter 25 and the motor drive amplifier 26, the digital calculation section of the microcomputer 8 includes a subtractor 19 from a binary counter 9 and a calculation unit 2.
1. By providing an integral loop that reaches the adder 23 via the accumulator 22, and by variable controlling the output oscillation frequency of the VCO 17 using the phase error signal d detected during playback by the recording/reproducing device, and changing the frequency of the clock pulse. It constitutes a phase feedback loop.

As a result, if, for example, the phase of the reproduction control signal a at time _t4 leads the reference phase, the lower part of the slope of the reference signal c is sampled and held by the comparison signal b at this time, so the phase error signal d decreases at time _t4 as shown in FIG. 2D. As a result, the output oscillation frequency of the VCO 17 decreases as shown in FIG. 2E, that is, the frequency of the clock pulse e decreases, and the speed detection pulse f
The number of clock pulses output from the gate between t ₅ and t ₆ decreases, and the value of the count N also decreases as shown by h ₃ in H in the same figure. Therefore, the error value N _E is shown in Figure 2 I.
It becomes negative as shown by i ₃ , and the cumulative value N _I and the calculator 24
The output value N _p decreases as shown by j ₃ and k ₃ in J and K of the figure, respectively, and the rotation of the motor 1 is controlled to be slow so that the reproduction control signal a and the reference phase coincide.

Conversely, if the phase of the reproduction control signal is delayed from the reference phase at the time _t7 shown in FIG. 2A, the phase error voltage d becomes high as shown in FIG. is E in the same figure.
As shown in the figure, the value of the count value N increases since it becomes higher after time _t7 . Therefore, the motor drive voltage l also increases, increasing the rotational speed of the motor 1 to make the reproduction control signal a and the reference phase coincide. In this way, when the phase of the reproduction control signal from the tape 10 deviates from the reference phase due to torque disturbance etc., even if the rotation speed of the motor 1, that is, the running speed of the tape 10 is equal to the reference speed, the frequency of the clock pulse e As a result, the output count value N of the binary counter 9 changes.

On the other hand, the digital calculation unit in the microcomputer 8 controls the drive voltage of the motor 1 so that N is always equal to the reference digital value N _R , that is, so that the error value N _E becomes zero. Therefore, even if N changes due to phase shift,
The rotation of the motor 1 is controlled so that N is equal to N _R , and finally the steady-state deviation from the reference value of the phase can be made completely zero.

Note that when the rotational speed of the motor 1 becomes faster than the reference speed, the period of the speed detection pulse f becomes shorter than the reference value, and due to the phase advance of the reproduction control signal a with respect to the reference phase at this time.
Since the clock pulse frequency from VCO 17 becomes lower than the reference value, the value of N decreases, and on the other hand, when the rotation speed of motor 1 becomes slower than the reference speed, the period of the speed detection pulse f becomes longer than the reference value. And since the clock pulse frequency becomes higher than the reference value, the value of N increases. Therefore, in this case as well, the motor 1 is adjusted so that the error value N _E is always zero.
In order to control the drive signal to the motor 1, the motor 1 is rotated at a constant speed at a predetermined reference rotation speed, and the phase of the reproduction control signal a is also made to match the reference phase.

By the way, the above is the operation of the recording/reproducing apparatus during reproduction, but in this embodiment, the servo system is configured so that the changeover switch 18 can be used to easily change the servo method even during recording.Next, the operation during recording will be explained. do. In recording and reproducing devices such as magnetic recording and reproducing devices and tape recorders, during recording, the information on the tape is generally not phase-locked and the tape is run, but the rotational speed is always constant, that is, the tape running speed is constant. It is necessary that records be made. Therefore, it is not necessary to vary the frequency of the clock pulse using the phase error signal, and it is sufficient to keep the frequency of the clock pulse constant at all times.

Therefore, in this embodiment, the changeover switch 1 is
8 is connected to the fixed terminal 18b side, and a predetermined constant frequency signal from the crystal oscillator 14 is used as a clock pulse to be connected to the AND circuit 7 through the changeover switch 18.
It is configured to apply to. Here, the output oscillation frequency of the crystal oscillator 14 is made to match the free-running oscillation frequency of the VCO 17. This is to make the tape running speed the same during recording and playback.

When recording, set the changeover switch 18 to the fixed terminal 18b.
It is clear from the above description that the motor 1 can be controlled at a constant speed at a predetermined constant rotation speed corresponding to the reference digital value N _R of the memory 20 by simply connecting the motor to the reference digital value N R of the memory 20 . In addition, when recording, tape 10
The control head 11 sends a control signal at a constant period in the tape running direction to the tape 1.
It is recorded in synchronization with the information signal recorded at 0 (not shown).

In this embodiment, the comparison signal forming circuit 1 performs phase control using a rotational phase error related to the rotational phase obtained from the reproduction control signal.
2. Although the phase comparator 13, the reference signal generation circuit 16, etc. are configured to be processed using analog signals, they are not limited to this configuration, and may be configured so that they are processed using digital signals. In this case, by configuring it integrally with the microcomputer 8 and processing it as software, it is possible to further reduce costs. Note that such digitization can be configured in the same manner as the method of detecting digital information related to the rotational speed obtained from the motor 1 in this embodiment, so detailed explanation will be omitted.

Furthermore, although the above embodiments have been described with reference to the application to a capstan motor of a recording/reproducing device, the application may also be applied to a rotary drum motor of a magnetic recording/reproducing device, a turntable rotating motor of a disc-shaped information recording medium reproducing device, etc. is also possible.

As described above, the digital servo device in the recording/reproducing apparatus according to the present invention gate-outputs a clock pulse at every predetermined period of speed detection pulses with a repetition frequency corresponding to the rotational speed of the motor that rotates in relation to the running of the recording medium. By counting the clock pulses output from the gate, a digital value corresponding to the rotational speed of the motor is obtained, and the error value is determined by comparing the digital values with preset reference digital values related to the steady rotational speed of the motor. The integrated output digital value of the error value obtained by cumulative calculation of the error value is added to the above-mentioned digital amount, and then converted into an analog signal, and the analog signal is applied as a drive signal to the above-mentioned motor at the same time. , the phase error between a reproduction control signal with a repetition frequency corresponding to the running speed of the recording medium obtained by reproducing a control signal recorded in advance on the recording medium at a constant period and a reference signal indicating a preset reference phase. The frequency of the clock pulse is variably controlled based on the detected phase error signal, and the drive signal to the motor is controlled so that the error value is always zero, so when disturbances such as torque fluctuations are applied. However, the steady deviation that occurs between the phase of the playback control signal and the reference signal can always be made completely zero.
In addition, the circuit that obtains the phase error signal conventionally used in the analog servo system can be used as is, and the circuit that generates the clock pulse only needs to be changed to a variable frequency oscillator. Furthermore, since it is controlled using digital information, it is extremely The servo operation can be performed stably, and by using a microcomputer in the digital calculation section, the loop gain of the servo system can be easily set and changed by a program, and the accuracy is good. The servo system during recording and playback can be easily switched by simply switching the output with a changeover switch. Therefore, for example, it is possible to fix the output oscillation frequency of a variable frequency oscillator for generating clock pulses during playback to a constant frequency during recording. No control signal generation circuit is required, the circuit configuration can be simplified, and the clock pulse frequency during recording is selected to be the same as the clock pulse frequency during playback when the phase of the playback control signal and the reference phase match. Therefore, it has a number of features such as being able to make the traveling speed of the recording medium the same during recording and during reproduction with a simple circuit configuration without using a frequency dividing means or the like.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing one embodiment of the apparatus of the present invention, and FIGS. 2A to 2L are time charts for explaining the operation of FIG. 1, respectively. 1...Controlled motor, 2...Capstan, 4
...Detection head, 8...Microcomputer,
9... Binary counter, 11... Control head, 13... Phase comparator, 16... Reference signal generation circuit, 17... Voltage controlled oscillator (VCO), 18...
...Selector switch, 19...Subtractor, 20...Memory, 21, 24...Arithmetic unit, 22...Accumulator, 2
3... Adder, 25... DA converter.

Claims (1)

[Scope of Claims] 1. Clock pulses are gated out at every predetermined period of speed detection pulses with a repetition frequency corresponding to the rotational speed of a motor that rotates in connection with the running of the recording medium, and the gated clock pulses are counted. By doing so, digital quantities corresponding to the rotational speed of the motor are obtained and compared with respective reference digital values related to the steady rotational speed of the motor set in advance to obtain error values thereof, and the error values are cumulatively calculated. The integrated output digital value of the error value obtained by the method is added to the above-mentioned digital quantity, and then converted into an analog signal, and at the same time, the analog signal is applied as a drive signal to the above-mentioned motor, and at the same time, a predetermined cycle is applied to the above-mentioned recording medium. Detect a phase error between a reproduction control signal with a repetition frequency corresponding to the running speed of the recording medium obtained by reproducing a control signal recorded in the recording medium and a reference signal indicating a preset reference phase, and detect the detected phase error. A digital servo device for a recording/reproducing apparatus, characterized in that the frequency of the clock pulse is variably controlled based on the signal, and the drive signal to the motor is controlled so that the error value is always zero. 2. A digital servo device in a recording/reproducing apparatus according to claim 1, wherein the motor is a capstan motor. 3. The scope of claims characterized in that the digital calculations for obtaining the digital quantity, the error value, the cumulative calculation value of the error value, and the addition value of the digital quantity and the cumulative calculation value are performed by a microcomputer. A digital servo device in the recording/reproducing apparatus according to item 1 or 2. 4. A changeover switch is provided that changes according to the mode of the recording/reproducing device, and during reproduction, a variable frequency oscillator generates a speed detection pulse with a repetition frequency corresponding to the rotational speed of a motor that rotates in relation to the running of the recording medium at predetermined intervals. By gate-outputting the clock pulses coming in through the changeover switch and counting the gate-output clock pulses, a digital quantity corresponding to the rotational speed of the motor is obtained, and a reference related to a preset steady rotational speed of the motor is obtained. The digital values are compared with each other to obtain their error values, and the integrated output digital values of the error values obtained by cumulative calculation of the error values are added to the digital amounts, and then converted into analog signals. At the same time, applying the analog signal as a drive signal to the motor, a reproduction control signal having a repetition frequency corresponding to the running speed of the recording medium obtained by reproducing a control signal recorded in advance on the recording medium at a constant period. A phase error with a reference signal indicating a preset reference phase is detected, and the detected phase error signal is used to variably control the output clock pulse frequency of the variable frequency oscillator. The output of the fixed frequency oscillator, which is selected from the output of the variable frequency oscillator, is used to control the drive signal to the motor so that the error value is always zero during both playback and recording. A digital servo device in a recording/reproducing device characterized by: 5. The output oscillation frequency of the fixed frequency oscillator is selected to be the same as the output oscillation frequency of the variable frequency oscillator when the phase of the reproduction control signal and the reference phase respectively match. A digital servo device in the recording/reproducing device according to item 4.