JPS60143470A - Speed control circuit of magnetic tape device - Google Patents

Abstract

PURPOSE:To eliminate quantizing errors of the periodical counting value of a rotational pulse which occurs due to difference in the winding radius of a magnetic tape and to secure the stable traveling speed of magnetic tape by providing a means which has a constant measured counting value by the standard clock of the output signal period of a rotation speed detector at any time. CONSTITUTION:A magnetic tape reel 3 has a tachopulse generator which generates a rotational pulse 1' (it generates one pulse at every rotation), and a magnetic tape reel 4 has another tachopulse generator which generates a rotational pulse 2' (it generates N pulses at every rotation). A radius calculation counting circuit 5 counts the number of pulses (n) of the rotational pulse 2' during one period T1 of the rotational pulse 1'. Thus, calculation of winding radii Ra and Rb is executed. The pulse period T2 of the rotational pulse 2' is the following equation: T2=2piRb/V0.N (V0 is the constant speed of a magnetic tape 1). Even if the Rb changes when the pulse period T2 is counted by a period measurement counting circuit 8 by inputting it through a counting clock generation circuit 9, a pulse may be generated after setting the clock period to gamma= T2/M=2piRb/V0.N.M from the counting clock generation circuit 9 so that the counting value will have a constant value M.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention provides a method for controlling the running speed of a magnetic tape using a signal output from a rotational speed detector provided in a magnetic tape reel drive motor. The present invention relates to a speed control circuit for a magnetic tape device.

(b) Background of the technology Magnetic tape 2. Magnetic tape running speed control for recording accurate data in the positive position.

There is a rising run control section from the start of running to constant speed running, a stable running speed control section where the magnetic tape runs at a stable constant speed, and a falling run control section to stop the magnetic tape at a predetermined position. , each travel control section needs to be accurately controlled.

Various methods have already been put into practical use for driving magnetic tape, but recently, as the recording density of magnetic tape has improved, smaller magnetic tape reels have been used to wind the magnetic tape. The reel-to-reel system, which directly drives magnetic tape reels, was adopted.

In the case of the above method, there is a method of controlling the running speed of the magnetic tape by using an output signal from a rotational speed detector (tacho pulse generator) provided in one of the motors that drive the magnetic tape reel.

Since the speed error may become large depending on how the output signal from the rotational speed detector (tacho pulse generator) is used, there is a need to develop a usage method that reduces the speed error.

(C) Problems with the Prior Art A conventional method for controlling the rotational speed of a magnetic tape reel in a magnetic tape device employing a reel-to-reel system will be described with reference to one drawing.

FIG. 1 is a diagram of a conventional magnetic tape reel rotation speed control circuit, in which (A) shows a circuit configuration diagram and (B) shows a reference pulse waveform.

In the figure, 1 is a magnetic tape and 2 is a magnetic head.

3.4 is a magnetic tape reel, 5 is a counting circuit for radius calculation,
Reference numeral 6 indicates a radius calculation circuit, 7 a motor current calculation circuit, and 8 a period measurement counting circuit. Also, Ra is the winding radius of the magnetic tape 1 wound on the magnetic tape reel 3, Rb is the winding radius of the magnetic tape 1 wound on the magnetic tape reel 4, and ■ is the winding radius of the magnetic tape 1 wound on the magnetic tape reel 3. The resulting rotational pulse.

(2) is a rotation pulse in which the magnetic tape reel 4 follows the magnetic tape reel 3 and generates n pulses per rotation while the rotation pulse is being output, and (2) is a clock pulse.

T1 indicates the period of the rotation pulse ■, T2 indicates the period of the rotation pulse ■, and T3 indicates the period of the clock pulse ■.

FIG. 1 shows a magnetic tape 1 for magnetically recording and retaining data.
A magnetic head 2 magnetically records data on a magnetic tape 1
．． Radius calculation counting circuit 5° for counting the rotation pulses ■ and rotation pulses ■ of the magnetic tape reels 3 and 41 on which the magnetic tape 1 is wound and stored.The winding radius Ra, l? is determined by the output from the radius calculation counting circuit 5. Radius calculation circuit for calculating b6. A motor current calculation circuit 7 that calculates the drive current to be applied to the drive moke (not shown) for the magnetic tape reel 3.4 based on the output signals from the radius calculation circuit 6 and the period measurement counting circuit 8.
It consists of a period measurement counting circuit 8 that counts the period of the two-rotation pulse (2) using the clock pulse (2), compares it with built-in reference speed information, and outputs speed error information to the motor current calculation circuit 7.

A speed detector (tacho pulse generator, etc. 2 not shown) is connected to a drive motor for magnetic tape reel 4 (not shown)
When speed control is performed to run the magnetic tape 1 at a constant speed, the winding radius 1? It is necessary to change the pulse period of the rotation pulse (2) generated by the speed detector (tacho pulse generator) in accordance with b. A clock pulse generated at the pulse period T2 of this rotation pulse ■ and a constant reference period ■
is input to the period measurement counting circuit 8, the pulse period T2 is counted by the clock pulse ■, and compared with the reference speed information (stored in the period measurement counting circuit 8), the speed error information is sent to the motor current calculation circuit 7. Output to.

The motor current calculation circuit 7 uses the information from the radius calculation circuit 6 to calculate the drive motor for the magnetic tape reels 3 and 4 (not shown).
A drive current to be passed through is calculated, and a drive motor (not shown) for the magnetic tape reel 3.4 is driven and controlled using the calculated drive current to run the magnetic tape 1 at a constant speed. However, in the conventional method described above, the error rate between the target count value and the actual count value of the actual speed differs depending on the magnitude of the pulse period T2 of the one-rotation pulse (2). In other words, the radius of one turn is 1? When b is small, the target count value due to the clock pulse ■ with a pulse period T2 is small, and when the second winding radius Rb is large, the target count value due to the clock pulse ■ with a pulse period r2 also becomes large, but the actual count value relative to the target count value The error rate (target count value - actual count value/target count value X100) increases as the target count value decreases, and decreases as the target count value increases.

In particular, when the difference between the minimum winding radius Rb and the maximum winding radius Rh is large, the quantization error in counting the target count value cannot be ignored in terms of speed control, which has the disadvantage of impairing the stability of the running speed of the magnetic tape 1. Ta.

(d) Object of the Invention The object of the present invention is to provide a new speed control circuit for a magnetic tape device that eliminates the above-mentioned drawbacks.

In particular, it is an object of the present invention to realize a speed control circuit for a magnetic tape device that can eliminate quantization errors in rotational pulse period counts due to differences in the winding radius of the magnetic tape and ensure a stable running speed of the magnetic tape.

(e) Structure of the Invention The present invention provides a speed control circuit for a magnetic tape device that controls the running speed of a magnetic tape based on a signal output from a rotation speed detector provided in a tape reel drive motor, The period of a reference clock for measuring the period of the signal output by the speed detector is changed according to the winding radius of the magnetic tape on the tape reel, and the period of the reference clock for measuring the period of the signal output from the rotation speed detector is changed. means is provided to ensure that the measured count value is always constant, and the period count value of the rotational pulse that is the output of the rotational speed detector is free from quantization errors caused by differences in the winding radius of the magnetic tape,
This can be achieved by a speed control circuit for a magnetic tape device, which is characterized by being able to ensure a stable running speed of the magnetic tape.

(f) Examples of the invention The present invention will be explained below with reference to the drawings.

FIG. 2 shows an embodiment of a speed control circuit for a magnetic tape device according to the present invention.

In the figure, 9 indicates a counting clock generation circuit.

Note that the same symbols as in FIG. 1 indicate the same contents, and ``■'' indicates the output pulse of the counting clock generation circuit 9.

This embodiment is composed of the circuit configuration shown in FIG. 1(A) and a counting clock generating circuit 9 that generates a clock pulse ■' whose period T3 is varied according to the winding radius Rb of the magnetic tape 1. ing.

Next, the operation of this embodiment will be explained.

The magnetic tape reel 3 generates a rotation pulse ■ (one pulse is generated for each rotation), and the magnetic tape reel 4 generates a rotation pulse ■ (one pulse occurs every rotation).
It is equipped with a tacho pulse generator (speed detector, not shown) which generates N pulses per rotation.

The radius calculation counting circuit 5 counts the number n of rotation pulses (2) during one period T1 of the rotation pulse (2). This results in
Calculation of the winding radii Ra and Rh in the radius calculation counting circuit 5 is performed using the following equations. However, Ra: Winding radius of the magnetic tape reel 3 Rb: Winding radius of the magnetic tape reel 4 Rmax: Magnetic tape reels 3, 4 Maximum radius Rmin: The pulse period T2 of the minimum half-rotation pulse ■ of the magnetic tape reels 3 and 4 is T2-2πRb/ν0・N(
However, vO is the constant speed of the magnetic tape 1). Furthermore, in order to ensure that when this pulse period T2 is inputted and outputted through the counting clock generation circuit 9 and counted by the period measuring counting circuit 8, the counted value remains a constant value M even if the second winding radius Rb changes. It can be seen that the clock period τ from the counting clock generation circuit 9 can be set to the following relationship. That is, one period τ=T
It is sufficient to generate a pulse ``2'' that satisfies 2/M=2πRb/VO-N.M.

In order to digitally output the pulse ■' with the above period τ to the period measurement counting circuit 8, the radius of 2 turns is 1? b is Rmi
When changing from n to Rmax, the minimum pulse period T2 is 72m1n, the maximum is 72max, and the winding radius is 11
Assuming that the radius calculation circuit 6 can sample 100 variations of b, the period τ in the Lnth sample is the period τ−T
min +Ln ((T2max -72m1n)
/100) (where rmin is the clock cycle at the minimum value of the winding radius Rb). Let the period of the reference clock in the counting clock generation circuit 9 be TO, and TO= (T2m
ax −1'2m1n ) /100, the frequency division ratio K
= r /TO=' Crmin +Ln ((T2
It is sufficient to provide a frequency dividing circuit of max -72m1n) /1001) /To in the counting clock native circuit 9.

A pulse whose period τ changes according to changes in the winding radius Rb so that the count value remains constant M even if the winding radius Rb changes.
The period measurement counting circuit 8 which receives the input from the counting clock generation circuit 9 counts the actual speed and outputs the difference from the built-in reference speed as a speed error to the motor current calculation circuit 7. Drive control of 3 and 4 drive motors (not shown).

(g) Effects of the Invention According to the present invention as described above, it is possible to eliminate the quantization error of the rotational pulse period count due to the difference in the winding radius of the magnetic tape in TI', and to ensure a stable running speed of the magnetic tape. This has the advantage of being able to provide a speed control circuit for a magnetic tape device.

[Brief explanation of drawings]

Figure 1 is a conventional magnetic tape reel rotation speed control circuit diagram.
FIG. 2 shows an embodiment of a speed control circuit for a magnetic tape device according to the present invention. In the figure, 1 is a magnetic tape and 2 is a magnetic head. 3.4 is a magnetic tape reel, 5 is a counting circuit for radius calculation,
Reference numeral 6 indicates a radius calculation circuit, 7 a motor current calculation circuit, 8 a counting circuit for period measurement, and 9 a counting clock generation circuit. Does #1 scream? I'm so drunk I'm so drunk

Claims (1)

[Claims] A speed control circuit for a magnetic tape device that controls the traveling speed of a magnetic tape based on a signal output from a rotation speed detector provided in a tape reel drive motor, the circuit comprising: a cycle of the signal output from the rotation speed detector; Means for changing the period of a reference clock for measuring the period of the magnetic tape according to the winding radius of the magnetic tape on the tape reel, so that the count value measured by the reference clock of the output signal period of the rotational speed detector is always constant. A speed control circuit for a magnetic tape device, characterized in that it is provided with: