JPS5828829B2 - Motor speed control device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a motor speed control device.

Generally, this type of device includes means for obtaining a first pulse having a pulse width corresponding to the speed of the motor, and means for obtaining a second pulse having a predetermined pulse width,
It is known that a speed error signal is obtained by comparing the pulse widths of the first pulse and the second pulse, and the speed of the motor is controlled using the error signal.

As a concrete example of this, the one shown in FIG. 1 can be considered.

In FIG. 1, reference numeral 1 denotes an input terminal, into which, for example, pulses from a pulse generator that generates third pulses (one per rotation, etc.) proportional to the rotation of the DC motor are input.

2 is a T flip-flop, which is triggered by a pulse from the terminal 1 mentioned above.

3 is a monostable multi-by-break, which is triggered by the output of the flip-flop 2.

4 is a NOR gate, and 5 is a Nants gate, to which the output of the flip-flop 2 and the output of the monostable multi-by-break 3 are input.

DI and D2 are diodes whose different poles are connected to the same terminal of a capacitor C, forming a charging and discharging circuit for the capacitor C.

In such a device, when the above-mentioned pulse shown in FIG. 2A is applied to the terminal 1, the pulse width t is output from the output terminal of the T flip-flop 2.

The first pulse shown in FIG. 2B is obtained.

This pulse is input to monostable multi-by break 3,
From the output terminal of the monostable multi-bi break,
The second pulse having a pulse width t3 shown in is obtained.

This pulse width t3 is the above-mentioned pulse width t. is the reference speed.

What is shown in FIG. 2 is the case where the speed is slower than the reference, and the pulse width is t.

>t3. In such a case, the Nant gate 5 to which the pulses shown in FIG. 2B and C are applied has no period in which both inputs are H, and therefore the output becomes H as shown in FIG. 2E.

-10,000, the NOR gate 4 to which the above pulse is input has a period of Δt in which both inputs are L, and during this period, the output is H as shown in the second diagram.

When the output of the Nant gate 5 becomes H, the diode D
2 is reverse biased and capacitor C is not discharged, but
During the period when the output of NOR gate 4 becomes H, diode D1
is forward biased, and the capacitor C is charged through the diode.

When this capacitor C is charged, the speed of the motor is controlled to increase.

The above explanation is for the case where the speed is slow, but when the speed is the same as the reference speed, the pulse width t.

and t3 become equal, and there is no charging or discharging of capacitor C.

Next, the case where the speed is high will be explained with reference to FIG.

In FIG. 3, A-E indicates the pulse at the same point as A-E in FIG.

When the speed is high, the pulse interval at terminal 1 is t.

becomes shorter than t3, and the output of the Nantes gate 5 has E
A period of L occurs as shown in FIG. 2, diode D2 is forward biased and capacitor C is discharged.

The output of the NOR gate 4 has no high period, the diode D1 is reverse biased, and the capacitor C is not discharged.

In such a device, the speed of the motor is high and the pulse width t mentioned above.

When t3 becomes less than 1/2 as shown in FIG. 4, the Noah gate 4 is closed as shown in FIG.
An H period occurs in the output of the Nandt gate 5, and an L period occurs in the output of the Nant gate 5, and the capacitor C is charged after being discharged, and the core
Since the voltage of the 7" sensor C is maintained, the speed of the motor is not controlled to slow down.

In this case as well, the above-mentioned abnormal rotation can be prevented by selecting the maximum value of the rotational speed of the motor in the operating state within a range in which the period of the first pulse exceeds the pulse width of the second pulse. can.

Generally, in a monostable multivibrator, there is a region in which a trigger is not applied for a short period from the trailing edge of a pulse.

Therefore, when using a monostable multi-bibreak as a means of obtaining a pulse with a predetermined pulse width, the period corresponding to the above region is added to the pulse width t3 to obtain the period of the first pulse or the period of the third pulse. It is necessary to select the cycle.

Moreover, instead of using the above-mentioned bistable multi-bi-break, it is also possible to limit the amplitude of the sine wave of the frequency according to the speed and make the rectangular wave a base shape.

Incidentally, in order to select the maximum value of the rotational speed under the operating condition of the motor, the torque/speed curve of the motor or the power supply voltage may be set accordingly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the present invention, and FIGS. 2 to 4 are timing charts of the above block diagram. 2: Flip-flop, 3: Monostable multi-bi break, 4: NOR gate, 5: NAND gate, C: Capacitor

Claims (1)

[Claims] 1 means for obtaining a first pulse having a pulse width depending on the speed of the motor; and means for obtaining a second pulse triggered by the trailing edge of the first pulse and having a constant width with respect to the first pulse. a monostable multi-by-break, a NOR gate to which the first pulse and the second pulse are input, a Nants gate to which the first pulse and the second pulse are input, and charging according to the output of the NOR gate. and a capacitor that is discharged according to the output of the Nandt gate, the pulse width of the first pulse and the pulse width of the second pulse are compared by the Norr gate and the Nandt gate, and The voltage of the capacitor is varied according to the error resulting from the comparison obtained in the output, and the speed of the motor is controlled according to this voltage, and the period of the first pulse is equal to the pulse width of the second pulse. A speed control device for a motor, characterized in that the maximum value of the rotational speed of the motor in the operating state is selected within a range exceeding the above range.