JP2000287498A - Drive control device for stepping motor - Google Patents

Abstract

(57) [Problem] To improve the load throughput by quickly starting a motor when rotating and stopping are repeated. When a motor is started, a motor drive task is called, and first, a post hold timer is checked. If the time is up, the motor is in the hold state. At this time, the motor is switched from the hold state to the drive state, and the pre-hold control is performed for a certain period of time. Also, if the timer is not running,
Since the stepping motor is in the drive state during the post-hold control, the post-hold control is interrupted at this time, and the motor is immediately subjected to slow-up drive control without performing the pre-hold control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a stepping motor for driving a load such as a print head.

[0002]

2. Description of the Related Art For example, in a printer in which a print head is moved along a platen using a stepping motor, when a print command is received, the motor is started, and the stepping motor is driven slow-down, constant-speed rotation, slow-down drive, and so on. The print heads are driven in the order of stop, and the print head is driven during constant-speed rotation to perform printing.

The stepping motor used in such a motor is actually driven and controlled in accordance with a motor driving task routine shown in FIG. 7 in order to prevent loss of synchronism and reverse rotation and accurate positioning of a printing position. It has become. That is, when the motor is started, first, in step S1, the torque of the motor is increased to bring the motor into a drive state.
That is, the voltage applied to the motor winding is increased to increase the winding current and increase the torque. In the case of the constant current chipper drive, the state where the set current is increased is set.

Next, in step S2, pre-hold control is performed. This is because the position of the rotor and the stator of the stepping motor is accurately positioned at the excited position by holding the torque for a certain period of time with the torque increased. If this is not done, the rotation angle of the rotor with respect to the first pulse becomes large, causing a problem that step-out or reverse rotation occurs.

Next, in step S3, the step-up motor is driven to perform a slow-up drive, and the angular velocity of the rotation of the motor is gradually increased. Then, in step S4, the process shifts to constant speed rotation control, and the motor is rotated at a constant angular speed. Thereafter, in step S5, the stepping motor is slowed down, and the angular speed of the rotation of the motor is gradually reduced to finally stop.

Next, in step S6, post hold control is performed. This is because, even after the motor stops rotating and the load such as the print head driven by the motor stops operating, the vibration is generated, and the motor torque increases for a certain time until the vibration stops. That is, hold control is performed in the state in which the control is performed.

The fixed time of the post hold varies depending on the load of the driving system. For example, when the movement of the print head is controlled by using a belt, it is about 100 msec.
In this state, since the torque is large, the rotor and the stator of the stepping motor are accurately positioned at the excited position. Finally, in step S7, the torque of the motor is reduced to bring the motor into a hold state.
Then, in this state, the apparatus stands by for the next motor start.

FIG. 8 shows the above control in terms of the relationship between the change in angular velocity and the change in torque with respect to time during the operation of the stepping motor. That is, the torque of the stepping motor increases at time t0, pre-hold control is performed, then, at time t1, a slow-up drive in which the angular velocity of the motor gradually increases is started, and at time t2, the angular velocity of the motor becomes constant. After shifting to constant-speed rotation control and continuing this until time t3, a slowdown drive in which the angular velocity of the motor gradually decreases at time t3 is started, and at time t4 the motor is stopped and post hold control is performed. Thereafter, at t5, the torque of the motor decreases and the motor enters a hold state.

[0009]

In such drive control of a stepping motor, when the rotation and stop of the motor are continuously repeated, as shown in FIG. 9, a hold state → pre-hold → slow-up drive → constant speed Since control of rotation → slow down drive → post hold → hold state is repeated each time, there is a problem that it takes time to start the motor and the load throughput decreases.

Accordingly, the present invention provides a drive control device for a stepping motor capable of quickly starting the motor when the rotation and stop are repeated, thereby improving the load throughput.

[0011]

According to the first aspect of the present invention,
In the stepping motor drive control device that sequentially performs slow-up drive, constant-speed rotation, slow-down drive, and stop control on the stepping motor that drives the load, and repeats the control, the step-down motor slow-down drive ends. A post-hold timer that counts a certain period of time corresponding to the time required for the vibration accompanying the driving of the post-load to stop, and a post-hold unit that holds the stepping motor in a large torque state while the post-hold timer is performing a count operation. When the motor is started, if the post-hold timer has expired, pre-hold means for increasing the torque of the stepping motor and holding it for a certain period of time before starting the slow-up drive of the stepping motor; and , Post hold Timer in which is provided with a control means for immediately starting the slow-up driving of the stepping motor without the hold control by canceling pre hold means counting the post-hold timer if during counting.

[0012]

Embodiments of the present invention will be described with reference to the drawings. In this embodiment, an embodiment in which the present invention is applied to a printer will be described.

FIG. 1 is a view showing a main part of a printer, in which a belt 4 is stretched between a pulley 2 fixed to a rotating shaft of a stepping motor 1 and another pulley 3, and printing is performed in the middle of the belt 4. The head 5 is attached. The printing head 5 moves left and right along the platen 6 by rotating the belt 4 between the pulleys 2 and 3 by the rotation of the stepping motor 1. The pulley 2,
3, belt 4, and print head 5 constitute a load.

Such a load forms a vibration system due to the elasticity of the belt 4, the mass of the print head 4, and the like. Therefore, when the print head 5 is moved by the stepping motor 1, after the movement is completed, the stepping motor 1 is stopped, and even if the rotor is located at the stationary position, the stepping motor 1 is not moved until the vibration of the vibration system converges. It is necessary to pass a large current and hold the rotor in a stationary position with a strong torque. And
After the vibration of the vibration system converges, the current of the stepping motor 1 is reduced to bring the rotor into a hold state in which the rotor is held at a low torque.

FIG. 2 is a block diagram showing a hardware configuration.
Reference numeral 1 denotes a CPU (central processing unit) constituting a control unit main body; 12, a ROM (read only memory) storing program data for the CPU 11 to control each unit; 13, various memories for data processing (Random access memory) having a table and a table, 14 is a timer, and 15 is an output port.

The timer 14 may be provided in the RAM 13. The CPU 11, the ROM 12, the RAM 13, the timer 14, and the output port 15 are electrically connected to each other via a bus line 16.

The output port 15 is connected to a current driver 17 for controlling the amount of current flowing through the stator winding of the stepping motor 1 and a phase driver 18 for switching and controlling the phase of the stator winding.

The RAM 13 is provided with a timer value table 131 shown in FIG. The timer value table 131 stores time data which is sequentially set in the timer 14 when the stepping motor 1 is controlled from the hold state to the pre-hold → slow-up drive → constant speed rotation → slow down drive → post-hold → hold state. When the stepping motor 1 is driven, the CPU 11 sequentially reads time data from the timer value table 131 and sets the time data in the timer 14.

Then, post-hold time data is read from the timer value table 131 and the timer 1
When set to 4, this timer 14 functions as a post hold timer.

FIG. 4 is a flowchart showing a routine of a motor driving task performed by the CPU 11, and this task is called by the main routine when the motor is started. In this task, first, in step S11, it is checked whether or not the post hold timer 14 is up.
This check is equivalent to checking whether the stepping motor 1 is in the hold state or the drive state.

When the time of the post-hold timer 14 has expired, the motor is in the hold state. In step S12, the CPU 11 reads the pre-hold time data from the timer value table 131 and sets it in the timer 14. Data is output to the output port 15 so that the current of the current driver 17 becomes a drive state in which the torque is large, and then the state becomes a wait state.

When the wait state is reached, the process shifts to pre-hold control in step S13 to return the rotor to the rest position. When the timer 14 finishes counting the pre-hold time, an interrupt is issued to the CPU 11, so that the motor 1 shifts from the wait state to the start state. Then, the process proceeds to the slow-up drive control in step S14.

If the post-hold timer 14 is not operating when the motor is started, the stepping motor 1 is in the post-hold control, the rotor is at the rest position, but the load is not vibrated. It has not yet converged. However, in this state, since the position of the rotor is determined, the post-hold timer 14 is canceled in step S15, the post-hold control is interrupted, and the slow-up in step S14 is immediately performed without performing the pre-hold control. Shift to drive control.

In the slow-up drive control in step S14, slow-up drive is performed for acceleration.
From the timer value table 131, first, throw-up 1
The time data of the pulse is read and set in the timer 14. Then, data is output to the output port 15 so that the phase driver 18 excites the next phase of the stepping motor 1 and the state shifts to the wait state.

The timer 14 counts the set time data and interrupts the CPU 11 when the time is up.
With this interrupt, the CPU 11 releases the wait state, reads the time data of the second slow-up pulse from the timer value table 131, and sets the time data in the timer 14. Then, data is output to the output port 15 so that the phase driver 18 excites the next phase of the stepping motor 1 and the state shifts to the wait state. The timer 14 counts the set time data and interrupts the CPU 11 when the time is up.

In this way, the time data of the last n-th pulse of the slow-up operation is set in the timer 14 and this control is repeated until the wait state is released, thereby performing the slow-up drive control for gradually accelerating.

After the end of the slow-up drive control, a constant-speed rotation control is performed in step S16. In this constant-speed rotation control, the CPU 11 reads out the time data of the constant-speed rotation from the timer value table 131 and sets it in the timer 14. Then, data is output to the output port 15 so that the phase driver 18 switches the phase of the stepping motor 1 according to the constant speed rotation.

The timer 14 counts the set time data, and interrupts the CPU 11 when the time is up. As a result, the process proceeds to the slowdown drive control in step S17.

In the slowdown drive control in step S17, slowdown drive is performed for deceleration.
Is the slowdown 1 from the timer value table 131.
The time data of the pulse is read and set in the timer 14. Then, data is output to the output port 15 so that the phase driver 18 excites the next phase of the stepping motor 1 and the state shifts to the wait state.

The timer 14 counts the set time data and interrupts the CPU 11 when the time is up.
With this interrupt, the CPU 11 releases the wait state, reads the time data of the second pulse of the next slowdown from the timer value table 131, and sets the time data in the timer 14. Then, data is output to the output port 15 so that the phase driver 18 excites the next phase of the stepping motor 1 and the state shifts to the wait state. The timer 14 counts the set time data and interrupts the CPU 11 when the time is up.

In this way, the time data of the m-th pulse of the last slowdown is set in the timer 14 and this control is repeated until the wait state is released to perform slowdown drive control for gradually decelerating.

When the slow-down drive control is completed, the process proceeds to step S18, where the CPU 11 reads out post-hold time data from the timer value table 131, sets it in the timer 14, and ends this motor drive task. At this time, the post-hold time data is set in the timer 14, and at this time, the timer 14 functions as a post-hold timer.

In this post hold, the stepping motor 1 is held in a state where the torque is large, and the rotor and the stator are positioned at the positions where they are excited. When the timer 14 counts up for a certain period of time and times out, a post-hold timer interrupt occurs, and this interrupt starts the post-hold timer interrupt task shown in FIG. Is output to the output port 15 so as to return to the main routine. Thus, the stepping motor 1 is in a hold state in which the stepping motor 1 is held with a small torque, and waits for the next motor start.

In such a configuration, when the motor is started to start printing, the motor drive task is called, and since the stepping motor 1 is initially in the hold state, the post-hold timer times out. The CPU 11 reads the pre-hold time data from the timer value table 131 and sets it in the timer 14, and outputs the data to the output port 15 so that the current of the current driver 17 becomes a drive state with a large torque. Wait state. Thus, the pre-hold control is started. By this pre-hold control, the rotor of the stepping motor 1 is returned to the rest position, and the rotor and the stator are accurately positioned at the excitation position.

When the timer 14 times out, the pre-hold control ends, and the stepping motor 1 is controlled to perform a slow-up drive. With this control, the angular velocity of the motor gradually increases. Then, when the angular speed reaches a predetermined speed, the motor 1 shifts to constant speed rotation control. During this constant rotation, the print head 5 moves at a constant speed along the platen 6 to perform printing.

When a series of printing is completed and the stepping motor 1 is temporarily stopped before the next printing, the stepping motor 1 is slow-down driven. Thereafter, when this control is finished and the rotation of the stepping motor 1 is stopped, the time data of the post-hold is set in the timer 14, and the timer functions as a post-hold timer.

When the next motor starts immediately after the post hold timer 14 starts operating, the timer 1
Since the motor drive task is called before the time of 4 is up, at this time, the post-hold timer 14 is canceled, the post-hold control is interrupted, and the slow-up drive control is started immediately after passing the pre-hold control. .

At this time, the stepping motor 1 is in the driving state by the post hold control, and the rotor and the stator are accurately positioned at the excitation position.
Even if the slow-up drive control is started, problems such as step-out and reverse rotation do not occur.

The stepping motor 1 shifts from slow-up to constant-speed rotation, printing is again performed by the print head 5, and then slows down and stops. Then, the operation again shifts to the post hold control, and the post hold timer 14
Starts the counting operation. Post hold timer 14
After a short time from the start of the operation, the next motor starts. If the timer is not timed out, the post-hold timer 14 is canceled, the post-hold control is interrupted, and the pre-hold is stopped. Slow-up drive control is started immediately after the control is passed.

FIG. 6 shows the above operation in terms of a change in angular velocity with respect to time of the stepping motor 1 and a change in torque with respect to time. As can be seen from this figure, the post-hold control is interrupted and the pre-hold control and the subsequent hold state are passed, so that the next motor can be started more quickly than the conventional control shown in FIG. Can improve the printing throughput.

The time from the stop of the rotation of the stepping motor 1 to the post-hold control and the start of the count operation of the post-hold timer 14 to the start of the next motor is long. If the time is up, the stepping motor 1 has shifted to the hold state in which the stepping motor 1 is held with a small torque. At this time, the pre-hold control is performed for a certain period of time as in the conventional case, and then the control shifts to slow-up drive control. Will be.

In this embodiment, one timer is used, and the timer is controlled by setting pre-hold time data, post-hold time data, and the like. However, the present invention is not limited to this. Control may be performed using a dedicated timer.

In this embodiment, the present invention is applied to a printer. However, the present invention is not limited to this. The point is that the stepping motor is driven by slow-up drive, constant-speed rotation, slow-down drive, and stop. Any control that drives the load by performing each of the above controls can be applied.

[0044]

As described above in detail, according to the present invention, after the motor is slowed down from the constant speed rotation and stopped, when the next motor starts at a relatively short time interval, the post hold control is interrupted. In addition, since the motor can be quickly thrown up after passing the pre-hold control and the subsequent hold state, the motor can be quickly started when the rotation and the stop are repeated, thereby improving the load throughput.

[Brief description of the drawings]

FIG. 1 is a main configuration diagram of a printer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a hardware configuration of a control unit according to the embodiment.

FIG. 3 is a diagram showing a configuration of a timer value table provided in a RAM of FIG. 2;

FIG. 4 is a flowchart showing a routine of a motor drive task performed by the CPU of FIG. 2;

FIG. 5 is a flowchart showing a routine of a post hold timer interrupt task performed by the CPU of FIG. 2;

FIG. 6 is a diagram showing an example of a change in angular velocity and a change in torque with respect to time during operation of the stepping motor in the embodiment.

FIG. 7 is a flowchart showing a routine of a conventional motor drive task.

FIG. 8 is a diagram showing a relationship between a change in angular velocity and a change in torque with respect to time of a stepping motor when executing the task in FIG. 7;

FIG. 9 is a diagram showing an example of a change in angular velocity and a change in torque with respect to time during a conventional stepping motor operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stepping motor 4 ... Belt 5 ... Print head 11 ... CPU (Central processing unit) 131 ... Timer value table 14 ... Timer

Claims (1)

[Claims] 1. A stepping motor drive control device which sequentially performs slow-up drive, constant-speed rotation, slow-down drive, and stop control on a stepping motor for driving a load, and repeatedly performs the control. A post-hold timer that counts a certain time period corresponding to the time until the vibration accompanying the driving of the load stops after the slow-down drive ends, and a time period during which the post-hold timer performs the count operation. A post-hold means for holding the motor in a torque state; and, when the motor is started, if the post-hold timer has expired, the stepping motor is increased in torque and held for a predetermined time prior to the start of the slow-up drive of the stepping motor. Pre-hold means When the motor is started, if the post-hold timer is in the counting operation, the control to cancel the counting operation of the post-hold timer and immediately start the slow-up drive of the stepping motor without performing the hold control by the pre-hold means. A drive control device for a stepping motor, characterized by comprising means.