JPS627784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a servo motor, and in particular, by controlling the rotation of a servo motor by switching from a digital control mode to an analog control mode during rotation, the motor can be reliably moved to a target address. This relates to a control method for stopping.

Normally, servo motors such as DC motors are used as various drive sources, but when used as a drive source for rotating the type wheel of a serial printer, the conventional motor control circuit 1 As shown in the figure, it has a servo motor 2, and the servo motor 2 is provided with a transducer 3. Transducer 3
An inverting differentiator circuit 5, an adder 9, and a count pulse generator 6 are connected to the generator 6, and a control circuit 7 is connected to the generator 6. A switching circuit 10 is connected to the differentiating circuit 5 via an adder 9, and the circuit 10 has a control circuit 7, a rotation voltage setting circuit 11 connected to the control circuit 7, and a motor drive connected to the servo motor 2. Circuit 12 is connected.

Therefore, when rotating and positioning the type wheel using the servo motor 2, when the motor 2 is rotated in the positive direction, a negative drive current I _M is applied to the motor 2 as shown in FIG. , then decelerate motor 2 by switching current I _M to positive,
In the vicinity of the target address, the stop current I _S is further increased in the positive direction.
That is, the motor 2 is stopped at the target address by flowing in the deceleration direction. Also, when rotating in the opposite direction,
As shown in FIG. 2b, the motor is first accelerated with a positive current I _M , then decelerated by switching the current I _M to negative, and stopped with a negative stopping current I _S. These controls are performed in the digital control mode where the drive current I _M flows.
This is done in DCM, and the part where the stop current I _S flows is done in analog control mode ACM. That is, as shown in FIG. 1, when driving the servo motor 2, the control circuit 7 determines the current position (starting address) of the motor 2, that is, the type wheel, and the position of the next character to be printed (destination address). ), the rotational direction of the motor 2 is determined, and the speed at which the motor 2 should be driven is determined and outputted to the rotational voltage setting circuit 11 as a direction signal S1 and speed data DATA. The setting circuit 11 receives the signal S1 and data.
According to DATA, a positive or negative analog rotation signal S2 is sent to the motor drive circuit 1 via a switching circuit 10.
The drive circuit 12 amplifies the signal S2 and applies it to the servo motor 2, thereby driving the motor 2 to rotate in the forward or reverse direction. On the other hand, when the motor 2 rotates, the transducer 3 outputs a position signal S3 as shown in FIG. 3 in synchronization with the rotation of the motor 2.
The signal S3 is input to a count pulse generator 6, and the generator 6 outputs a count pulse CP to the control circuit 7 every half cycle of the signal S3 in synchronization with the signal S3. The control circuit 7 uses the pulse CP to up/down a counter indicating the current address of the type wheel and therefore the motor 2, and changes the speed data DATA output to the setting circuit 11 according to the difference between the current address and the target address. go. As a result, the rotation signal S2 outputted from the setting circuit 11 also changes, and eventually a drive current I _M with a pattern corresponding to the digital control mode DCM as shown in FIG. 2 flows through the motor 2, and the motor 2 is accelerated. After that, it will be decelerated. When the current address of the motor 2 reaches the vicinity of the target address, the control circuit 7 changes the control mode signal S4 from "0" to "1" and outputs it to the switching circuit 10.
The circuit 10 switches the control mode from the previous digital control mode DCM to the analog control mode ACM by the signal S4, and changes the signal output to the drive circuit 12 from the previous rotation signal S2 to the stop signal S5 from the adder 9. do. On the other hand, the inverting differentiator circuit 5
Since the position signal S3 is differentially inverted and outputted, for example, if the motor 2 is moved in the forward direction, the address A0 is
When rotating from A2 to A2, the position signal S3 near address A2 shown in the dashed line in FIG.
is converted into a differential signal S6 shown in the dashed line in FIG. is output to.
(That is, if the signal S3 is θ, the signal S6 is −θ〓
Therefore, the signal S5 becomes -(θ-θ〓.) Therefore,
When the circuit 10 switches to the analog control mode ACM, a positive voltage stop signal S5 is applied to the motor 2, a positive stop current I _S shown in FIG. address A2 of
Make sure to stop. Also, reverse the motor 2,
When rotationally moving from address A4 to A0, the position signal S3 becomes as shown by the solid line in FIG. 4A near address A0, and the differential signal S6 becomes as shown in FIG.
Furthermore, the stop signal S5 becomes as shown by the solid line c in the same figure, and the negative voltage stop signal S5 is applied to the motor 2 by the analog control mode ACM, and as shown in Fig. 2b, the stop signal S5 becomes negative as shown in Fig. A current I _S flows and the motor 2 is reliably stopped at address A0.

Conventionally, the type wheel pitch is a rotation amount corresponding to one cycle of the position signal S3, and therefore each type wheel is rotated at addresses A0, A, which are sequentially set every half cycle of the position signal S3.
Addresses A0, A2, A among 1, A2, ...
4, . . ., and if the motor 2 was stopped at even addresses A0, A2, . . ., it was possible to accurately position the type on the type wheel. However, recently there has been a strong demand for an increase in the number of printed characters, and as a result, it is necessary to place printed characters at odd addresses A1, A3, etc., and to stop the motor 2 at all addresses every half cycle of the position signal S3. It's emerging. but,
In this case, the polarity of the stop signal S5 changes depending on the starting address and the destination address.
That is, the starting addresses are odd addresses A1, A3,
...and the target addresses are also odd addresses A1, A3...
...and the starting address is even address A
0, A2, A4..., and the target address is an odd number address A1, A3..., regardless of the rotation direction, the polarity of the stop signal S5 becomes the opposite polarity to the polarity that should originally be output, and as shown in FIG. As shown by the broken line, the stop current I _S flows in the direction of accelerating the motor 2, making it difficult to stop the motor 2 at the target address. (For example, address A
When the motor 2 is rotated forward from 1 to A3 or from A2 to A3, a positive stop signal S5 must be applied to the motor 2, and a positive stop current I _S must flow, as shown by the solid line in Fig. 2A. However, the actual position signal S3, differential S6, and stop signal S5 flow as shown by the solid line in Figure 4, the signal S5 becomes a negative voltage, and the current I _S also flows as shown by the broken line in Figure 2A. becomes negative, and the motor 2 will be accelerated when entering the analog control mode ACM. Motor 2 to address A
3 to A1 and from A4 to A3, as shown by the solid line in FIG. 2B, the stop current I _S ,
Therefore, even though the stop signal S5 needs to be negative, as shown by the dashed line in FIG.
5 is positive, so the stop current I _S is as shown in Fig. 2b.
It becomes positive as shown by the broken line, and the motor 2 is accelerated. Therefore, the present invention provides a servo motor control method that eliminates the above-mentioned drawbacks by changing the polarity of a stop signal in an analog control mode depending on the starting address and destination address of the motor. The purpose is to

Hereinafter, the present invention will be specifically explained based on an embodiment shown in the drawings.

As shown in FIG. 5, the motor control circuit 1 includes a servo motor 2, but the parts already explained in FIG. 1 are given the same reference numerals as in FIG. 1, and the explanation of those parts will be omitted. Adder 9 and switching circuit 10
The switching circuit 13 and the inverting circuit 15 are connected between them. Since the motor control circuit 1 has the above configuration, when the control mode signal S4 becomes "1",
When the switching circuit 10 is driven and the digital control mode DCM based on the rotation signal S2 changes to the analog control mode ACM based on the stop signal S5, the starting address when the motor 2 rotates becomes an odd number address A.
1, A3, ... and the destination address is also an odd number address A
1, A3, . . . and when the starting address is an even address A0, A2, A4, . . . and the destination address is an odd address A1, A3, . 0'' and is input to the switching circuit 13, and the input via the inverting circuit 15 is outputted to the switching circuit 10 as a stop signal S5. (That is, if the position signal S3 is θ, the output of the inverting circuit 15 becomes θ−θ〓, and the output of the adder 9 −
The polarity is reversed from (θ−θ〓). ) Then, the stop signal S5 applied to the motor 2 via the switching circuit 10 and the drive circuit 12 has the polarity that should originally be output to the motor 2. A stop current I _S flows in the direction in which the motor should be decelerated, and the motor 2 stops accurately at the desired address. (Now, from address A1 to A3,
Or, if the motor 2 is rotated forward from A2 to A3,
As shown in FIG. 4, the stop signal S5 becomes a negative voltage, but its polarity is reversed by the inverting circuit 15 and becomes a positive voltage, and the motor 2 receives a positive stop current as shown by the solid line in FIG. I _S flows and motor 2 stops. Even in the case of reverse rotation from address A3 to A1 and from A4 to A3, the inversion circuit 15 causes the signal S5 to rotate.
The polarity of is negative, as shown by the solid line in Figure 2b,
A negative stop current I _S flows, and the motor 2 stops. ) In addition, if the departure address is an odd numbered address A1, A3, ... and the destination address is an even numbered address A0, A2, A4, ... other than the above case, the departure address is an even numbered address A0, A2, A4, ... When the addresses are even addresses A0, A2, A4..., the switching signal S7 becomes "1" and the switching circuit 13 is directly connected to the adder 9, and the output of the adder 9 is directly sent from the switching circuit 10. The stop signal S5 from the adder 9, which is applied to the motor 2, has a polarity that allows a normal stop current I _S to flow through the motor 2, so the motor 2 stops accurately at the target address. (For example, from address A1 to A4,
When rotating forward from A0 to A2, the stop signal S5 applied to the motor 2 becomes a positive voltage as shown by the dashed line in FIG. 4c, and the normal positive stop current I as shown in FIG. 2a. _S flows. Furthermore, when the motor 2 is reversely rotated from address A3 to A2 and from A2 to A0, the signal S5 becomes a negative voltage as shown by the solid line in FIG. 4c, and as shown in FIG. A current I _S flows. ) In the above embodiment, the present invention was applied to a servo motor for driving a type wheel of a serial printer. Of course, the present invention can be applied to all control systems that require stopping a servo motor.

As explained above, according to the present invention, the polarity of the stop signal S5 in the analog control mode ACM is changed and applied to the motor 2 according to the starting address and destination address of the servo motor 2 such as a DC motor. Therefore, it is possible to stop the motor 2 at an arbitrary address every half cycle of the position signal S3 generated from the transducer 3.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional servo motor control circuit, Fig. 2 is a time chart showing the drive current and stop current when the servo motor rotates and stops, and Fig. 3 shows the position signal from the transducer. FIG. 4 is a time chart showing a position signal, a differential signal and a stop signal at the time of stopping, and FIG. 5 is a block diagram showing an example of a servo motor control circuit to which the present invention is applied. 2...Servo motor, 3...Transducer, A0, A1, A2, A3, A4,...Address, ACM...Analog control mode, DCM...Digital control mode, DATA...Speed data, S
2... Rotation signal, S3... Position signal, S5... Stop signal, S6... Differential signal.

Claims (1)

[Claims] 1. A control circuit 7 that outputs speed data (DATA) according to the deviation between the target position and the current position, and a position signal S3 synchronized with the rotation of the servo motor 2.
a position detector 3 that outputs a differential signal S6 by inverting and differentiating the position signal S3;
an inverting differentiator circuit 5 which outputs the differential signal S6 and the position signal S3, an adder circuit 9 which adds the differential signal S6 and the position signal S3 and outputs a stop signal S5, and a control mode signal S4 from the control circuit 7 that corresponds to the speed data. It consists of a switching circuit 10 that selectively supplies the drive signal or the stop signal S5 to the servo motor drive circuit 12, and controls the motor in a digital control mode in which the drive signal is given to the servo motor when driving, and the stop signal when stopping. The motor is controlled in an analog control mode applied to the motor, and an inverting circuit 15 inverts the stop signal S6 and outputs an inverted stop signal; A control method for a servo motor, comprising a switching circuit 13 that selectively supplies a signal or an inverted stop signal to the switching circuit 10, and controlling the state of the switching signal according to the target position of the motor.