JPS6156713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When digitally controlling the motor current of a DC motor at a constant speed using a processing device, the present invention switches the unit digital change amount in multiple stages according to the set speed to follow load fluctuations. This invention relates to a speed control method for DC motors that improves performance.

Conventionally, in order to perform digital constant speed control for printing kanji, alphanumeric characters, etc., the applicant filed a patent application in 1983.
−12647 “Direct current motor speed control method”
is proposed.

The above proposed example will be briefly explained with reference to FIG. When a printer's space motor drive command is given to the processing unit (CPU) 8, the processing unit 8 sends digital data corresponding to the drive current of the DC motor 1 to the D/D.
The analog data is set in the A conversion register 11, and the analog data is transferred from the D/A conversion register 11 to the analog level comparison circuit 10 via the D/A converter 12.
guided by. Next, a motor drive command is sent from the processing device 8 to the drive circuit 9. The analog level comparison circuit 10 compares the level of the analog voltage obtained from the motor current detection resistor 13 and the analog voltage from the D/A converter 12, and if the former is smaller than the latter, the drive circuit 9 supplies current to the DC motor 1. , the current supply is cut off, and the motor current is controlled according to the analog data of the D/A converter 12.

On the other hand, as the DC motor 1 rotates, a pulse train corresponding to the motor rotation period is generated from the pulse encoder 2 via the photodetector 3 and the pulse shaping circuit 4. The period of this pulse train is measured for each pulse train by a pulse period measurement register 5, and compared by a period information comparison circuit 6 with the contents of a reference period information register 7 corresponding to the speed set in advance by the processing device 8. The information of this comparison result is led to the processing device 8, and the processing device 8 takes in this comparison information for each pulse train, determines the slowness of the motor rotation speed, and updates the contents of the D/A conversion register 11. The motor current is increased or decreased by Further, based on the information given from the processing device 8 to the drive circuit 9, constant speed control is performed with respect to the set speed by combining reverse rotation of the motor, dynamic braking, and interruption of the motor current.

When the speed control method according to the above proposed example is applied to the space control of the dot matrix printer mentioned above, the control of the motor current information from the processing device 8 in response to changes in motor rotation is always performed using a constant unit digital change amount (step amount). It is carried out in In the case of the dot matrix printer, for example, the load duty differs between alphanumeric characters and kanji characters, so constant speed drive is performed at a set speed of normal commercial speed or low speed. In this case, if the step amount is constant with respect to load fluctuations, the adaptability will be poor at high speeds, and deviations such as overshoots and undershoots may occur at low speeds.

SUMMARY OF THE INVENTION An object of the present invention is to provide a speed control system for a DC motor that has good responsiveness to load fluctuations and is free from overshoot or undershoot when constant speed drive is performed at different set speeds.

In order to achieve the above object, the DC motor speed control method of the present invention converts the rotational speed of the DC motor controlled to a set speed by a processing device into pulses, and compares the pulse period with a reference period of the set speed. , a means for inputting the comparison information into a processing device to control motor current information, and a means for comparing the motor current information from the DC motor with the motor current information from the processing device and feeding it back to the motor drive system, A speed control method for a DC motor that performs constant speed control digitally, characterized by comprising means for changing the unit digital change amount in multiple stages according to the set speed with respect to the motor current information from the processing device. It is something to do.

The present invention will now be described in detail with reference to examples.

The principle of the present invention is the processing device 8 in the proposed example.
The step amount of the motor current from the motor is changed depending on whether the set speed is high or low. Therefore, the configuration includes a high-speed/low-speed switching circuit 21, which is enclosed by a double frame in FIG. For example, for kanji at low speed, set the step amount to △ _i ,
For alphanumeric characters at high speeds, increase the step amount by 2△ _i
By doing so, it is possible to perform printing with good quick response and without overshoot or undershoot.

FIGS. 2a to 2d are explanatory views of the operation of essential parts of the present invention according to the embodiment of FIG. 1.

Figure a shows the reference period _information value derived from the reference period information register 7 in FIG. Figure b shows the period of a pulse train synchronized with the rotation of the DC motor 1, and it is assumed that the magnitude of the period T _x changes as shown. That is, T _x
Where the value is large, the rotation is slow, and where it is small, the rotation is fast. The magnitude of T _x is measured by a pulse period measurement register, the period information of T _s and T _x is compared by a period information comparison circuit 6, and the comparison information is provided to a processing device 8. Figure c shows the comparison information; it is "1" when T _x > T _s , and "1" when T _x < T
The processing _device 8 takes in this information for each pulse edge in b of the same figure, and generates T _x
> _Ts , the motor current is increased by one step (△ _i ), and if _Tx < _Ts , it is decreased by one step (△ _i ), so that _Tx ≒ _Ts, that is, the motor rotation This is to follow the cycle so that it becomes equal to the reference cycle.

As mentioned above, when kanji, alphabets, and numbers are set to different set speeds by the host device and driven at a constant speed, the step amount must be increased at high speed in response to load fluctuations (△ _i → 2△ _i ) , the speed response deteriorates, and conversely, at low speeds, unless the step amount is reduced (2△ _i
→△ _i ), overshoot or undershoot occurs.

For this purpose, the number of steps is changed for each pulse edge shown in FIG. 2B, depending on the set speed, and is increased or decreased depending on the comparison information "1" or "0" shown in FIG. Figure d is a waveform diagram of motor current information controlled in this way, where waveform A corresponds to low speed and waveform B corresponds to high speed.

As explained above, according to the present invention, when driving at a constant speed with different set speeds, the unit digital change amount is switched in multiple stages according to the set speed, so that load fluctuations can be easily tracked. It is possible to control the speed of a DC motor without any deviation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention shown in comparison with a conventional example, and FIGS. 2 a to 2 d are explanatory diagrams of the operation of the embodiment of FIG. is a pulse encoder, 3 is a photodetector, 4 is a pulse shaping circuit, 5 is a pulse period measurement register, 6 is a period information comparison circuit, 7 is a reference period information register, 8 is a processing device, 9 is a drive circuit, 10 is an analog Level comparison circuit, 11 is a D/A conversion register, 12 is a D/A converter, 13 is a motor current detection resistor,
21 indicates a high speed/low speed switching circuit.

Claims (1)

[Claims] 1. Means for converting the rotational speed of a DC motor controlled to a set speed by a processing device into pulses, comparing the pulse period with a reference period of the set speed, and inputting the comparison information into the processing device to control motor current information. and,
In a speed control method for a DC motor that digitally performs constant speed control, the method comprises means for comparing motor current information from the DC motor with motor current information from the processing device and feeding it back to the motor drive system. A speed control method for a DC motor, comprising means for changing unit digital change amount in multiple stages according to a set speed with respect to motor current information from a device.