JPH0515197A - Drive control method for step motor - Google Patents

Abstract

PURPOSE:To provide a closed loop drive control method through which a step motor can arrive correctly at a target position without causing step-out even when the load increases due to various factors at the time of acceleration driving. CONSTITUTION:In a step for acceleration driving a step motor 3 through a control circuit 1 and a driving circuit 2 according to an accelerating part table in a slewing table, lagging amount of the rotational position of the step motor 3 with respect to a rotational position commanded on the accelerating part table is detected by means of an encoder 4 and a lagging amount detecting circuit 5. Thus detected lagging amount is then compared in a comparing circuit 6 with a preset value and when the lagging amount reaches the set value, switching is made to equi-speed driving and the stepping defined on the accelerating part table is finished through the equi-speed driving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving and controlling a stepping motor used for carriage feeding or paper feeding of a serial printer by open loop control based on a slewing table.

[0002]

2. Description of the Related Art As a drive control method of a stepping motor used for carriage feed or paper feed of a serial printer, open loop control, which has a great cost advantage, has been widely adopted. The open loop control is to control the stepping motor from starting to stopping according to a preset speed pattern. The speed pattern is generally known as slewing, and is set in the form of a slewing table in which drive pulse numbers sequentially given to the stepping motor are associated with pulse widths. Then, for example, in the case of carriage feeding, an optimal slewing table is selected from a plurality of slewing tables according to the type of print command to control the stepping motor.

FIG. 5 shows an example of a slewing table in the carriage feed. FIG. 5A is an accelerating section table in the step of accelerating driving the stepping motor, and FIG. 5B is a constant-velocity section table in the step of uniformly driving the stepping motor. The numerical value of the counter corresponding to the drive pulse number and the pulse width are shown. Is associated with the value of the timer corresponding to.

Further, a schematic configuration of a conventional drive control device for performing open loop control is shown in a block diagram of FIG. As shown in the figure, the control circuit 1 which receives the operation command gives an excitation signal to the drive circuit 2, and the drive circuit 2 drives the stepping motor 3 with a drive pulse in accordance with the operation mode defined by the control circuit 1. The stepping motor 3 is step-operated. Then, the control circuit 1 and the drive circuit 2 apply a drive pulse to the stepping motor 3 according to the slewing table to control the speed of the stepping motor 3 to a target speed and rotate it to a target position.

Further, the relationship between the target speed ω0 of the stepping motor 3 thus controlled and the time is shown in the characteristic diagram of FIG. 7 in association with the width of each drive pulse of the slewing table.

As shown in the figure, upon start-up, the pulse width (timer value) is 5 msec according to the above-mentioned acceleration section table.
(Milliseconds) to 0.5 msec, gradually shortening 1
The 28th drive pulse is given to accelerate the stepping motor 3. After that, 0.5 ms according to the constant velocity section table
Equal-width N driving pulses are applied to drive at a constant speed. Printing is performed during the constant speed feeding of the carriage by this constant speed driving. Therefore, the constant speed count number N, which is the number of drive pulses for constant speed driving, is set according to the number of dots and the number of characters of a printed character.

After the above-mentioned constant speed driving, deceleration driving is performed according to a deceleration table (not shown). In this example, the deceleration table is constructed by arranging the 28 drive pulses of the accelerating unit table in reverse, that is, arranging from the side having the shorter pulse width.

[0008]

In the conventional control method described above, the drive torque is always applied in accordance with the slewing table regardless of the magnitude of the load applied to the stepping motor 3, so that the most torque is required. When a large load is applied to the stepping motor 3 during the acceleration drive, for example, in the case of carriage feed of a serial printer, when the carriage feed resistance increases due to a change in environmental temperature, vibration, or a change in printer attitude, There is a problem that the stepping motor 3 is out of step. If the step-out occurs, the rotational position after that becomes incorrect and the target position cannot be correctly reached.

Conventionally, in order to prevent step-out due to such an increase in load, it is necessary to use a stepping motor having an output power larger than necessary, which would lose the cost merit of the open loop control.

For a load increase due to a change in environmental temperature, a method has been proposed in which a temperature sensor is provided to detect the environmental temperature, and the output power of the stepping motor is changed according to the detected temperature (Japanese Patent Laid-Open No. HEI-2). -46195), it is not possible to cope with an increase in load due to factors other than changes in environmental temperature.

Further, a method has been proposed in which a dummy feeding step is provided in the carriage feeding to store the input power pattern (Japanese Patent Laid-Open No. 2-301469), but it requires closed loop control of the stepping motor and the dummy feeding step. If a load change occurs before executing the procedure, it cannot be dealt with.

The present invention has been made in order to solve the above problems. Even when the load increases due to various factors during acceleration driving, the stepping motor can be correctly reached to the target position without stepping out. It is an object of the present invention to provide a drive control method by open loop control that can be performed.

[0013]

In order to achieve the above object, in the drive control method according to the present invention, in the step of accelerating and driving the stepping motor in accordance with the accelerating unit table of the slewing table, the command by the accelerating unit table is given. The delay amount of the rotation position of the stepping motor with respect to the rotation position is detected. When the delay amount reaches a preset value, the driving is switched to the constant speed driving, and the constant speed driving completes the step amount set in the acceleration table.

[0014]

When the delay amount of the rotational position of the stepping motor reaches the set value, the driving is switched to the constant speed driving so that the time of each driving pulse given to the stepping motor is kept long and the stepping motor It is possible to maintain the output torque and prevent out-of-step due to increased load.

Further, even if the driving is switched to the constant speed driving during the acceleration driving, the stepping amount determined by the accelerating section table is completed, so that the stepping motor is set to the target without reducing the determined rotation amount. The correct rotation position can be reached.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a drive control device for carrying out the drive control method according to the present invention.

As shown in the figure, in this drive control device, in addition to the control circuit 1 and the drive circuit 2 provided in the conventional drive control device shown in FIG. 6, an encoder 4 connected to a stepping motor 3 and control are performed. A delay amount detection circuit 5 and a comparison circuit 6 connected to the circuit 1 are provided.

The encoder 4 detects the rotational position of the stepping motor 3 driven by the control circuit 1 and the drive circuit 2 and outputs a detected position signal.

The delay amount detecting circuit 5 outputs a drive pulse which is output in synchronization with the detected position signal from the encoder 4 and the excitation signal from the control circuit 1, that is, in synchronization with the drive pulse of the stepping motor 3. Based on the monitor signal, the delay amount of the rotation position of the stepping motor 3 from the command rotation position is detected.

Further, the comparison circuit 6 compares the delay amount detected by the delay amount detection circuit 5 with the delay amount set value preset in the comparison circuit 6, and the detected delay amount is equal to or more than the set value. If it becomes, the delay signal is sent to the control circuit 1
Send to. The delay amount set value should be appropriately set according to its output torque and use conditions so as not to cause stepping out of the stepping motor 3, and is set to a value of about 2 to 2.5 times the step angle, for example. To be done.

FIG. 2 is a block diagram showing a concrete example of the configuration of the control circuit 1. As shown in the figure, the CPU 11 is the main body, and the program memory 12 that stores the slewing table and the data for the recording head drive, the RAM 13 that temporarily stores and organizes various data read from the program memory 12, and the drive pulse monitor. A counter / timer 14 that outputs a signal and a recording head drive signal is provided.

Next, the drive control method according to the present invention by the drive control device having the above-mentioned configuration will be described with reference to the flow chart of FIG. 3 and the characteristic diagram of FIG.

When an operation command is input to the control circuit 1, the CPU 11 of the control circuit 1 first makes a slewing selection (S-1), and a target speed pattern from start to stop of the stepping motor 3 is read from the program memory 12. Read selectively. The slewing table of the selected target speed pattern is the same as that in the conventional example shown in FIG. Then, in the characteristic diagram of FIG. 4, the time change of the selected target speed ω0 is shown by a solid line in correspondence with the width of each drive pulse of the slewing table. Also, for the deceleration unit table (not shown) of the slewing table,
As in the case of the conventional example, it is assumed that the 28 drive pulses of the accelerating unit table shown in FIG. 5A are arranged in reverse, that is, from the side having the shorter pulse width. Of course, the acceleration unit table and the deceleration unit table may be asymmetrical.

After the above slewing selection, the control circuit 1
Initializes the counter of the selected slewing table and sets the counter value n to n = 1 (S-
2) Then, according to the accelerating unit table of the slewing table, the stepping motor 3 is accelerated for one count (S-3).

Then, the control circuit 1 judges whether or not the comparison circuit 6 has output a delay signal (S-4), and if it does not output it, then it is determined whether or not the acceleration count of the accelerating unit table has ended, in this case. , It is determined whether the numerical value n of the counter has reached 28 (S-5). If it has not reached, the value n of the counter is incremented by 1 (S-6) and the acceleration drive is continued.

In this way, the control circuit 1 continues to accelerate and drive the stepping motor 3 in accordance with the accelerating section table when the stepping motor 3 does not receive a large load and the comparison circuit 6 does not output the delay signal. Then, after the value n of the counter reaches 28 and the acceleration drive is completed (S-
5), constant speed driving is performed according to the constant speed unit table (S-
7) Then, deceleration driving is performed according to the deceleration unit table (S-8) and stopped. On the other hand, while the acceleration drive is being performed according to the acceleration table, the load received by the stepping motor 3 becomes abnormally large due to some factor, for example, due to an increase in the feed resistance of the carriage, and is indicated by a broken line in the characteristic diagram of FIG. As measured by the stepping motor 3 ω
When 1 becomes gradually smaller than the target speed ω0 and the delay amount of the rotation position of the stepping motor 3 from the command rotation position reaches the set value, the comparison circuit 6 outputs a delay signal.

Then, it is judged that the delay signal is output (S-
4) The control circuit 1 does the timer value of the accelerating unit table after the delay signal output time t1 to the same value as the value at the count at the time t1, or a count close to the time t1, for example, at the previous count. A constant constant velocity timer value is set by extending and fixing the value to the same value (S-9). Then, constant speed driving is performed according to the constant speed timer value (S-10).

That is, when the delay amount of the rotational position of the stepping motor 3 from the command rotational position reaches the set value and the delay signal is output in the step of accelerating the drive according to the accelerating unit table, the constant speed drive is performed. After the switching and the delay signal output time t1, the driving is performed at a constant control speed ω2 as shown by the alternate long and short dash line in the characteristic diagram of FIG.

In this way, when the delay amount reaches the set value, the driving is switched to the constant speed driving, so that the time of each driving pulse given to the stepping motor 3 is kept long and the output torque of the stepping motor 3 is kept. Hold
It is possible to prevent step-out due to increased load.

After switching to the constant speed driving in this way, the control circuit 1 continues the constant speed driving until the acceleration count of the accelerating section table is finished, until the numerical value n of the counter reaches 28 in this embodiment (S-11). , 12). In this way, even if the driving is switched to the constant speed driving during the acceleration driving, the stepping amount determined by the accelerating unit table is completed, so that the stepping motor 3 is set to the target without reducing the determined rotation amount. The correct rotation position can be reached.

After the end of the acceleration count, the control circuit 1 shifts to the constant speed driving by the constant speed unit table (S-13). Even in this constant velocity driving process, the timer value of the constant velocity part table of the selected slewing table is replaced with the above constant velocity timer value, and the constant velocity timer value is used for the total number of constant velocity counts on the constant velocity part table. Drive at a constant speed. That is, the driving is continued at the same constant control speed ω2 as the acceleration driving process.

In the case of a serial printer, printing is performed during the constant speed feeding of the carriage by this constant speed driving. Therefore, the constant speed count number N is set according to the number of dots of the printed character and the number of characters.

After the constant velocity driving for the total number of constant velocity counting is completed, the control circuit 1 shifts to the deceleration driving by the deceleration unit table. First, the counter of the deceleration unit table is initialized and the numerical value n of the counter is set. Set n = 1 (S-1
4), followed by deceleration drive for one count (S-1
5).

Next, the control circuit 1 determines whether the current count timer value is shorter than the constant speed timer value (S-16). If it is short, the timer value of the count is extended to the same value as the constant speed timer value (S-1).
7). Therefore, in this case, the driving at the constant control speed ω2 is continued. If the current count timer value is equal to or greater than the constant speed timer value, the timer value according to the deceleration unit table is used for driving.

In this way, the control circuit 1 continues the deceleration drive until the deceleration count of the deceleration table is completed, until the numerical value n of the counter reaches 28 in this embodiment (S-1).
(8, 19), and after the deceleration count ends, the stepping motor 3 is stopped.

[0037]

As described above, according to the drive control method of the present invention, even when the load increases due to various factors during acceleration driving, the stepping motor can be correctly reached to the target position without stepping out. be able to.

Therefore, it is not necessary to use a stepping motor having an output power larger than necessary, so that the cost advantage of the open loop control can be maintained.

Moreover, since the open loop control is performed, the load on the control circuit can be reduced as compared with the closed loop control.

Furthermore, the drive control method according to the present invention can be applied to drive control of any stepping motor used as a drive source, not limited to stepping motors used for carriage feeding and paper feeding of serial printers. The same effect can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a drive control device for implementing a drive control method according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of a control circuit of the drive control device.

FIG. 3 is a flowchart illustrating a drive control method according to the present invention.

FIG. 4 is a characteristic diagram showing a target speed, an actually measured speed, and a control speed of the stepping motor in the embodiment.

FIG. 5 is a diagram showing an example of a slewing table, (a)
Is an acceleration unit table, and (b) is a constant velocity unit table.

FIG. 6 is a block diagram of a drive control device in a conventional example.

FIG. 7 is a characteristic diagram showing a target speed of a stepping motor in a conventional example.

[Explanation of symbols]

 1 control circuit 2 drive circuit 3 stepping motor 4 encoder 5 delay amount detection circuit 6 comparison circuit

Claims (1)

Claim: What is claimed is: 1. A drive control method for rotating a stepping motor to a target position by open loop control based on a slewing table. The stepping motor is accelerated and driven according to an accelerating unit table of the slewing table. In the process, the delay amount of the rotation position of the stepping motor with respect to the command rotation position by the acceleration table is detected, and when the delay amount reaches a preset value, it is switched to the constant speed drive and the constant speed drive is performed. A drive control method of a stepping motor, characterized in that the step amount defined by the acceleration table is completed by driving.