JPH06133593A - Method and device for controlling stepping motor - Google Patents

Abstract

PURPOSE:To provide a stepping motor controlling method and device which do not use any closed loop and do not require the preparation of speed data and, at the same time, do not cause stepping out. CONSTITUTION:In this method in which a driving pulse is given to a stepping motor 40 from a motor driver 20 based on an impressed pulse P1 from a speed control means 10, the speed of the motor 40 is controlled based on the difference between the load current at the middle of the rising time t0 and falling time t1 of the pulse P1 and the load current I2 immediately before the falling time t1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor control method and apparatus, and more particularly to a stepping motor control method and apparatus using a closed loop.

[0002]

2. Description of the Related Art Since stepping motors are easy and accurate to control, they are used for various types of electronic equipment such as facsimiles, copiers, printers, and the like for conveying paper.

FIG. 5 shows a conventional controller for a stepping motor. A drive pulse is applied from the motor driver 20 to the stepping motor 40 in response to the applied pulse obtained from the speed control means 100.

As shown in FIG. 6, the torque-speed characteristic of the stepping motor 40 is such that the lower the speed, the larger the torque, and the higher the speed, the smaller the torque. Also, if the speed control in this range is performed in the shaded area in the figure,
It shows the range in which the transition (slewing) from startup / retraction to steady operation can be performed smoothly. Therefore, the speed setting unit 101 of the speed control means 100 is provided with a storage means such as a ROM, gives the storage means an initial speed in accordance with the torque speed characteristic, and gradually increases the set speed to a predetermined speed, Stores speed data.

The output of the speed setting unit 101 is input to the pulse generating unit 102, where a pulse having a frequency corresponding to the speed is output.

[0006]

Generally, the relationship between the pulse motor and the speed is determined by the frequency of the applied pulse. Therefore, the control means 100 can perform reasonable slewing by giving the pulse of the frequency corresponding to the speed torque characteristic shown in FIG. Further, this control can be realized with considerably high accuracy unless a particularly large load is applied, and open control is sufficient as shown in FIG.

However, the control means 100 is not shown in FIG.
To operate in the shaded area of R, the speed setting means 101 R
It is necessary to write speed data in the OM or the like, which makes the work troublesome. Further, when the motor is started, since the torque width that can cope with the load fluctuation is small, when there is a large fluctuation in the load, there is a risk that the motor will step out and stop.

The present invention has been proposed in view of the above conventional circumstances, and an object of the present invention is to provide a stepping motor control method and apparatus which do not need to create speed data and are free from the possibility of step-out. It is what

[0009]

The present invention employs the following means in order to achieve the above object. That is, in the stepping motor control method in which the drive pulse is applied from the motor driver 20 based on the applied pulse P ₁ given by the speed control means 10, the center of the rising time t ₀ and the falling time t ₁ of the applied pulse P ₁ is set. The speed control is performed on the basis of the difference between the load current I _{1 of the part} and the load current I ₂ immediately before the fall t ₁ .

In order to realize the above method, the present invention, as shown in FIG. 1, applies a drive pulse to a stepping motor 40 based on a speed control means 10 and an applied pulse P ₁ applied from the speed control means 10. In a stepping motor control device including a motor driver 20,
Inserted between the motor driver 20 and the stepping motor 40, the load current I _{1 at} the center of the rising t ₀ and the falling t ₁ of the applied pulse P ₁ and the load current I ₂ immediately before the falling t ₁ Confirmation means 3 for detecting the difference between
0 and the speed control means 10 for changing the frequency of the applied pulse P ₁ based on the confirmation result of the detection confirmation means 30.
And is configured to include.

The detection confirmation means 30 is the stepping device.
Current detecting element 4 for detecting a load current flowing through the motor 40
1 and the applied pulse P detected by the current detecting element 41₁ 
Rise time t₀ And fall t₁ Central load
Current I₁ And at the fall t ₁ Last load current I₂ And
A comparator 42 for comparison is provided.

Further, the speed control means 10 sets a predetermined value in the synthesizer 12 to apply the application pulse P of a predetermined cycle.
_With the counter 11 that generates ₁ , the above counter 11
And an acceleration clock generating means 16a for outputting an acceleration clock to the counter 11 to change the predetermined value when the detection confirmation means 30 instructs acceleration, and the detection confirmation means 30 instructs deceleration. When the deceleration clock is present, the deceleration clock is output to the counter 11 and the deceleration clock generating means 16b for changing the predetermined value is provided.

[0013]

4A shows the load current I when the stepping motor is operating with no load or a light load.
(B) shows the load current I when a load is applied to the stepping motor.

Comparing FIGS. 4 (a) and 4 (b), the larger the load, the central portion of the applied pulse P ₁ (FIG. 4 (d)) (the rising time t ₀ and the falling time t of the applied pulse P ₁ ).
The load current I ₁ near the center of ₁ ) becomes large, and the current-time curve becomes nearly horizontal. Furthermore, FIG. 4 at the time of loss of synchronism to (c), the at the center of the applied pulse P ₁ load current I ₁
Is more likely to be larger than the load current I ₂ at the time of falling.

Therefore, the magnitude of the load can be determined by detecting the difference between the load current I ₁ at the center of the pulse and the load current I ₂ immediately before the pulse falling t ₁ .

[0016] Therefore, by detecting the load current I ₁ and t ₁ immediately before the load current I ₂ at the falling pulse falling in the central portion of the applied pulse P ₁ by detecting the recognition means 30 in the present invention, the pulse central load current I _When the difference between _{1 and} the load current I ₂ immediately before the pulse falling time t ₁ becomes smaller than the predetermined range, the fact is transmitted to the control means 10.

The control means 10 determines that the difference is within a predetermined range.
When knowing that the applied pulse P ₁Lower the frequency of
It This reduces the speed of the pulse motor 40.
As a result, the torque will increase and you will avoid step-out.

[0018]

1 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a timing chart thereof.

The stepping motor control device according to the present invention comprises a control means 10, a motor driver 20, and a detection confirmation means 30 inserted between the stepping motor 40.

In the control means 10, first, the counter 11 sets a value corresponding to the oscillation frequency in the synthesizer 12. The synthesizer 12 uses the oscillating frequency of the reference oscillator 13 and the voltage controlled oscillator (VCO) 14 at the next stage based on the set frequency to determine a predetermined frequency (applied pulse P ₂ below) as shown in FIG. The pulse P _{2 of} about 10 to 20 times) is oscillated. The output of the VCO 14 is further frequency-divided by the frequency divider 15 to become the applied pulse P ₁ shown in FIG.

The clock from the acceleration clock generator 16a and the deceleration clock from the deceleration clock generator 16b are input to the multiplexer 17 in the counter 11, and the acceleration or deceleration instruction can be given by the operation described below. ing.

Further, the counter 11 is provided with a maximum rotation speed setting device 18 so that the count value of the counter 11 does not exceed the value set by the maximum rotation speed setting device 18. The counter 11 is also provided with a minimum rotation speed setting device 19, and the initial value is always the value indicated by the minimum rotation speed setting device 19.

The applied pulse P ₁ output from the frequency divider 15 is input to the motor driver 20, where it is converted into a drive pulse and input to the stepping motor 40.
Between the motor driver 20 and the stepping motor 40, a current detection element 31 such as a resistance and an induction coil which constitutes the detection confirmation means 30 is inserted. This current detection element 3
The load current I detected by 1 is small at no load or light load as shown in FIG. 3 (b) or FIG. 4 (a) at the rising time t ₀ of the applied pulse P ₁ ,
The maximum is in t ₁ just before the falling edge of the applied pulse P _1.

The load current I thus detected by the current detecting element 31 is sampled at the center of the rising time t ₀ and the falling time t ₁ of the applied pulse P ₁ and immediately before the falling time t _1. . That is, the VCO 14
The pulse P ₂ more obtained are input to the timing generating circuit 35, wherein the generated near the center of the indicia pressure pulse P ₁ timing pulse S ₁ (FIG. 3 (d)) and the applied pulse P ₁
Timing pulse S generated immediately before the fall t _{1 of
2} (FIG. 3E) is formed.

Then, the sampling pulse S ₁ holds the sampling data D ₁ corresponding to the load current I ₁ at the center of the applied pulse P _{1 in} the sampling hold 36 as shown in FIG. As shown in FIG. 3 (h), the sampling data D ₂ corresponding to the load current I ₂ immediately before the fall of the applied pulse P ₁ is applied to the sampling hold 37 by the pulse S ₂ .
Hold.

The sampling data D ₁ and D ₂ thus held are the timing pulse S ₃ (FIG. 3) generated until the next applied pulse P ₁ rises.
At time t ₂ when (f)) occurs, the comparator 38 compares the _two .

By the way, in FIG. 3 (b) and FIG. 4 (a),
The load current I when no load or light load is shown
As shown in Fig. 4 (b), the central part of the pulse
Becomes nearly horizontal, and when step out occurs, as shown in Fig. 4 (c)
When the center of the pulse falls₁Bigger than last time
Tends to become. Therefore, the load current I at the center of the pulse ₁ 
Load current I just before the fall₂ To the same extent as
The risk of step-out occurs when the size is approaching
Become.

Therefore, in the comparator 38, when the difference between the sampling data D ₂ immediately before the pulse fall t ₁ and the sampling data D ₁ at the center of the pulse becomes smaller than a predetermined value, the fact is indicated by the counter. 11 is transmitted. Up to this point, the multiplexer 17 has input the acceleration clock obtained from the acceleration clock generation circuit 16a to the counter 11, but when the above-mentioned transmission is made, the multiplexer 17 selects the deceleration clock obtained from the deceleration clock generation circuit 16b. The input is made to the counter 11. As a result, the stepping motor 40
The speed will be reduced, the torque will be increased, and step-out will be avoided.

The deceleration needs to be performed rapidly in order to avoid step-out. Therefore, the cycle of the deceleration clock is set to about 100 ms, which is considerably smaller than the cycle of the acceleration clock (about 500 ms).

[0030]

As described above, according to the present invention, the stepping motor can be started and operated without creating the frequency data of the pulse given to the stepping motor, and the speed is reduced when the load current becomes large to some extent. Therefore, even if there is a sudden change in load, the risk of step out is reduced.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a timing diagram of the present invention.

FIG. 4 is a waveform diagram showing a load current.

FIG. 5 is a block diagram of a conventional example.

FIG. 6 is a velocity torque characteristic curve diagram.

[Explanation of symbols]

10 speed control means 12 synthesizer 16a acceleration clock generator 16b deceleration clock generator 20 motor driver 30 detection confirmation means 40 stepping motor 41 current detection element 42 comparator P ₁ applied pulse t ₀ rising edge t ₁ falling edge I ₁ pulse center Part load current I ₂ Load current immediately before the fall of the pulse

Claims (4)

[Claims] 1. A stepping motor control method for applying a drive pulse from a motor driver (20) based on an applied pulse (P ₁ ) given by a speed control means (10), wherein the applied pulse (P ₁ ) Rising edge (t ₀ ) and falling edge (t ₁ )
A stepping motor control method characterized in that speed control is performed based on the difference between the load current (I ₁ ) in the central part of and the load current (I ₂ ) immediately before the fall (t ₁ ). 2. A speed control means (10) and the speed control means (1)
Motor driver (2) that gives a drive pulse to the stepping motor (40) based on the applied pulse (P ₁ ) given by (0).
0) and stepping motor control device, which is inserted between the motor driver (20) and the stepping motor (40), the applied pulse (P ₁ ) rises (t ₀ ) and falls (t ₁ ) The detection confirmation means (30) for detecting the difference between the load current (I ₁ ) at the center of the and the load current (I ₂ ) immediately before the fall (t ₁ ) and the confirmation results of the above detection confirmation means (30) A stepping motor control device comprising: the speed control means (10) for changing the frequency of the applied pulse (P ₁ ) based on the above. 3. A current detection element for detecting the load current flowing through the stepping motor (40) by the detection confirmation means (30).
(41) and the load current at the center of the applied pulse (P ₁ ) detected by the current detection element (41) at the rising edge (t ₀ ) and the falling edge (t ₁ ).
3. The stepping motor control device according to claim 2, further comprising a comparator (42) for comparing (I ₁ ) with the load current (I ₂ ) immediately before the fall (t ₁ ). 4. The speed control means (10) sets a predetermined value in a synthesizer (12) to generate an application pulse (P ₁ ) of a predetermined cycle, and the detection confirmation means (11). When the acceleration command is issued by (30), the acceleration clock generator (16a) that outputs the acceleration clock to the counter (11) and changes the predetermined value, and the detection confirmation means (30) 3. The stepping motor control device according to claim 2, further comprising a deceleration clock generator (16b) that outputs the deceleration clock to output the deceleration clock to the counter (11) to change the predetermined value.