JPH04133696A - Step motor driving system - Google Patents

Abstract

PURPOSE:To shorten starting and stopping time and to eliminate positional shift of stopping by a method wherein a constant current corresponding to a specified driving current is fed, the level thereof is lowered in the following stage, pulse width and driving current are set at prescribed values corresponding to a predetermined speed, and the pulse width and the driving current are increased when a step motor is stopped. CONSTITUTION:A constant current amplifier 2 sets the pulse width and the current value at levels higher than those corresponding to a constant rotational speed, so that a maximum torque is produced at starting time, based on designated driving signal 3 and current operation mode signal 4. Thus set current is fed to a specified phase coil. The pulse width and the current value are then decreased gradually thus making a smooth transition to steady speed state. The step motor is finally settled in constant speed rotation through two phase excitation. At the time of stoppage, the pulse width and the current value are increased gradually. According to the constitution, starting and stopping time of the step motor 1 is shortened and positional shift is suppressed at the time of stopping.

Description

[Detailed Description of the Invention] [Summary] Regarding a step motor drive method that starts and stops a step motor, the pulse width and drive current are increased at the time of starting and stopping to increase torque and reduce the number of steps.・Aiming to shorten the time required for stopping and reduce the deviation of the stop position, a step motor with two-phase excitation and a constant current that supplies a constant current to the step motor based on the instructed drive signal and drive current are used. It supplies the corresponding constant current to the step motor according to the drive signal (initially long pulse width) and the instructed drive current (initially large current value) instructed at startup, and then At this stage, the respective values are decreased and the drive signal pulse width and drive current value are gradually set to the specified values for a predetermined speed, while at the time of stopping, the drive signal pulse width and the drive current are increased to stop the drive signal. Configure.

[Industrial application field]

The present invention relates to a stenopmoke drive system for starting and stopping a step motor.

[Conventional technology]

Conventionally, when starting a step motor from a stopped state to a constant speed by driving a step motor, for example, a two-phase drive as shown in FIG.
) As shown in the conventional example, constant current is applied for 4ms, 4ms, 2
ms, 2 ms, and thereafter pulses with a width of 1 ms at a constant speed were supplied to the step motor as shown in the figure. Furthermore, when stopping from a constant speed, a similar deceleration current is supplied to stop the motor.

Hereinafter, a brief explanation will be given of (7) and (in Fig. 4).

FIG. 7 ta+ shows an example of the structure of a two-phase step motor.

Here, A, B, A, and B represent terminals (phases) that supply current to the two-phase step motor, and the two-phase step motor is driven by supplying two-phase currents shown in FIGS.

FIG. 7('b) shows the current waveform of two-phase excitation. Here, AXB, A, and B are the corresponding terminals of No. 711(a) (
This shows the current waveform supplied to the phase.

Conventionally, the current waveform of a constant current value shown in Figure 7) was
(a) Since the motor was supplied to a two-phase step motor and started from a stopped state to a constant speed, a constant current with pulse widths of 4 ms, 4 ms, 2 ms, and 2 ms was supplied as shown in the conventional example (in Fig. 4). Drive current was supplied to the step motor to start it at a constant speed. Further, when stopping from a constant speed, a constant deceleration current is similarly supplied to the step motor.

[Problems to be Solved by the Invention] Conventionally, when a large torque is required at startup and stop, the 1lii time at startup is initially increased as described above, and the time at constant speed is gradually increased. Therefore, in the conventional example shown in FIG. 4, 4 staves and a total of 12 ms were required.

Therefore, when used in a mechanical part that requires positioning of a step motor, it is necessary to start and stop the step motor from a position obtained by subtracting the number of steps required for starting and stopping from a predetermined total amount of movement. However, when starting/stopping is performed based on a sensor output signal, there is a problem that, for example, a time lag until stopping inevitably results in a lag in the stopping position. For this reason, it is desirable for a device that drives and controls a step motor using a sensor output signal as a trigger to reduce the number of steps required for starting and stopping as much as possible, and to reduce the positional deviation required for starting and stopping.

The present invention increases the pulse width and drive current to increase torque and reduce the number of steps when starting and stopping.
The purpose is to shorten the time required for stopping and reduce the deviation of the stopping position.

[Means to solve the problem]

FIG. 1 shows a system configuration diagram of the present invention.

In FIG. 1, a step motor 1 is a two-phase excitation step motor.

The constant current amplifier 2 supplies a constant current to the step motor 1.

Drive signal 3 is a signal for driving the step motor by two-phase excitation.

The current operation mode signal 4 is a mode signal for specifying a constant current value to be supplied to the step motor 1.

[Function] As shown in FIG. 1, the present invention allows the constant current amplifier 2 to generate maximum torque at startup based on the instructed drive signal 3 and the instructed current operation mode signal 4. Then, set the pulse width and current value to be thicker than the constant speed rotation speed. Supply this to the coil of the specified phase. Next, gradually reduce the pulse width and current value so that the speed transitions smoothly to the constant speed state. do.

Finally, a constant speed rotation state is achieved by two-phase excitation. On the other hand, when stopping, the pulse width and current are increased in the same way to stop the motor.

Therefore, it is possible to increase the pulse width and pulse current value that drive the pulse motor 1 during start-up and stop, increase the torque, and reduce the number of steps, reducing the time required for start-up and stop of the step motor 1 before stopping. It becomes possible to reduce positional deviation.

〔Example〕

Next, the configuration and operation of one embodiment of the present invention will be explained in detail using FIGS. 1 to 60.

In the first time, the step motor 1 is a two-phase excitation step motor, and has a configuration as shown in FIG. 7+8+ described above.

The constant current amplifier 2 supplies a constant current to the step motor 1 based on the instructed drive signal 3 and current operation mode signal 4, and is, for example, a circuit example shown in FIG. 6, which will be described later.

The drive signal 3 is a signal for driving the step motor 1 by two-phase excitation, and here, I N-A, IN-B,
These are IN-A and IN-B signals.

The current operation mode signal 4 is a mode signal that specifies a constant current value to be supplied to the step motor 1, and is a mode signal that specifies a constant current value to be supplied to the step motor 1.
This is a mode signal that supplies four different currents to the step motor 1 as shown in FIG. 3 by a combination of two bits of PWD2.

I10 port 5 connects to microprocessor 6 via HAS
Alternatively, it is an input/output port for setting the drive signal 3 and current operation mode signal 4 to the constant current amplifier 2 from a higher-level controller.

The microprocessor 6 executes ■/○ according to a program not shown, as shown in a fifth concave flowchart to be described later.
A drive signal 3 and a current operation mode signal 4 are notified to the constant current amplifier 2 via the port 5, and the step motor 1 is controlled to start, drive at constant speed, stop, etc.

First, the present invention will be explained in detail using FIG.

Figure 7 +8+ shows the relationship between time and speed of the step motor 1 in Figure 1;
shows the relationship between time and current. The dotted line in the figure is the conventional example.

The first acceleration section (■) in Fig. 2 tb+ is the step motor 1
This shows a state in which a large current (■1) is supplied to the coil of the fourth @ (aj) as shown in (■).

The second acceleration section of
This shows a state in which a second magnitude current (2) is supplied to the coil as shown in (2) in Fig. 4 (fa).

The two-phase excitation shown in ■ in Figure 4 (al
The supplied state is shown in ゛.

When the motor stops, a large current is similarly supplied, and after the motor stops, a holding torque stopping current I4 is supplied.

As described above, the step motor 1 with two-phase excitation is driven using a current with a large current value and a large pulse width at startup, and is gradually turned off and driven with a specified current at a constant speed.
When stopping, the two-phase excited step motor 1 is similarly decelerated using a current with a large current value and a large pulse width, and after stopping, the starting torque and deceleration torque are increased by supplying a holding current. It becomes possible to reduce the number of steps required for starting and stopping. A detailed explanation will be given below.

FIG. 3 shows an example current operation mode signal according to the present invention.

This is the first country current operating mode signal 4 PWD 1
, by the combination of 2 bits of PWD2, the constant current amplifier 2 performs constant current control (power supply voltage is set to 0N10FF) so that the step motor 1 is supplied with a current that is 11: maximum torque 01: strong torque 10: normal rotation 00: holding. Is there a constant current law?l).

FIG. 4 shows the excitation method at startup. 41r+a+ shows this embodiment, and FIG. 4(b) shows a conventional example.

A current as shown in FIG. 4 (in the case of this embodiment of al, the already mentioned second opening) is supplied. That is, at startup, the second
During the first acceleration period shown in Figure 2, a large current as shown in Qo (a current that generates a maximum torque of 11 in PWD1 and pWD2 in Figure 3) is supplied to the stethoscope motor 1, and during the second acceleration period shown in Figure 2, When , a second large current as shown in ■' (a current that generates a strong torque with PWDI and PWD2 of 01 in Figure 3) is supplied to the step motor 1, and when two-phase excitation is shown in Figure 2, ■ Normal current as shown in “(Fig. 3 PW
I) l, current when PWD2 is in normal rotation of 10) is supplied to the step motor.

Incidentally, in the case of the conventional example shown in FIG. 4 (bl), a constant current is always supplied as shown in the figure, as already described in the section of the prior art.

Next, the operation of the structure shown in FIG. 1 will be explained in detail in accordance with the order of the fifth review flowchart.

(1) When the start of the step motor is instructed (in the case of eYEs), the drive signal 3 of the first acceleration section and the current operation mode signal (signal with PWD 1 and PWD 2 of 11) 4 are notified to the constant current amplifier 2. Step motor 1
In Fig. 4 (a) ■° current (second opening) ■) is applied to (
@, ■). Then, current is passed for a predetermined number of steps (
When the 4th tbta+ is ■', only one step of current is applied).

(2) After flowing for a predetermined number of steps (if YES), notify the constant current amplifier 2 of the drive signal 3 of the second acceleration section and the current operation mode signal (PWDI, a signal in which PWD2 is 01) 4. , the current shown in Fig. 4 (al ■゛ (■ in Fig. 2 (b)) is passed through the step motor 1 (■, [phase]).Then, the current is passed for the predetermined number of steps (Fig. 4). [a)
``■'', current is passed for only one step).

(3) After running the specified number of steps (in case of OYES)
, drive signal 3 during steady rotation and current operation mode signal (
Notify the constant current amplifier 2 of the signal (signal PWD 1, PWD 2 is 10) 4, and flow the current ta + ■' (■) of Fig. 4 ta + ■' (second opening) to the step motor 1 ([phase], [phase]) . Then, current is applied for a predetermined number of steps.

(4) After passing a current through the step motor 1 for a predetermined number of steps at a constant speed (in the case of OYES), the current is passed in the same manner as at startup. That is, the drive signal 3 of the first $i speed section and the current operation mode signal (signal in which PWDl and PWD2 are 01) are notified to the constant current amplifier 2, and the step motor 1
Apply deceleration current to (■, ■). Then, a deceleration current is caused to flow for a predetermined number of steps.

(5) After passing current through the step motor 1 for a predetermined number of steps (in the case of OYES), drive signal 3 for the second deceleration section
and current operation mode signal (PWDl, PWD2 are 11
signal) 4 to the constant current amplifier 2, and causes a deceleration current to flow through the step motor 1 (@, [phase]). Then, a deceleration current is caused to flow for a predetermined number of steps.

(6) After passing current through the step motor 1 for a predetermined number of steps (if [phase] is YES), determine whether or not the step motor 1 has advanced by a certain amount, and if YES, stop the step motor 1.
5TOP when YES), N.

When step motor 1 steps out (when @No), ERROR is notified (O, O).

As described above, when starting and stopping, the drive signal 3 and current operation mode signal 4 are notified to the constant current amplifier 2, and the step motor 1 can be started by reducing the current from a large current to the current for steady rotation, or vice versa. By supplying a larger current than the normal current to stop the motor, the torque at starting and stopping can be increased, and it is possible to start or stop steady rotation in a short period of time.

FIG. 6 shows a circuit example of a constant current amplifier according to the present invention.

This is a circuit that supplies a signal of the magnitude specified by the drive signal 3 and the current operation mode signal 4 to the coil of the specified phase, and controls the power supply ON/OFF to generate a current of the specified current value. supplying. This will be explained below.

In FIG. 6, COMPI and COMP2 are comparators.

T" is a transistor that performs 0N10FF control by supplying or cutting off current to the coil of one pole of the step motor 1.

Dl and D2 are diodes that allow current to flow in the opposite direction to the coil when the Tr is turned off.

Rs is a resistance that detects 1i'/Jjc flowing through the coil. The operation will be explained below.

[11 The current flowing through the coil is detected as a voltage by the resistor Rs, and the base l1lI! is detected by COMPI. Compare with voltage Vref. When the voltage of the resistor Rs is lower than the reference voltage Vref, the output of COMPI becomes H level and is input to COMP2, and the output of COMP 2 becomes L level, supplying a signal via the inverter and the AND circuit to the transistor T.
r is in conduction state (I.

n), electric fi+24V, coil, transistor T
r, a current flows through the resistor Rs.

B) The voltage generated across the resistor Rs when the current flows through it is base 1.
! When the voltage becomes higher than the voltage Vref, the output of COMP1 becomes L level, the output of COMP2 becomes H level, and the transistor Tr becomes non-conductive. When the transistor Tr becomes non-conductive, a current 1off in the opposite direction flows into the coil via the diodes DI and D2. And resistance R1
, the voltage of the capacitor C1 increases with a time constant determined by the capacitor CI, and the transistor Tr is held in a non-conducting state until the voltage exceeds a predetermined value (for example, +2V).

Then, when the output of COMP2 becomes L level, the transistor 'Fr becomes conductive. These transistors T
0N10F by repeating conductive and non-conductive states of r
F control and supply a constant current to the coil of the step motor 1. At this time, the magnitude of the current flowing through the coil of the step motor 1 is based on the third country current operation motor signal 4. i! It is sufficient to change the voltage Vref.

〔Effect of the invention〕

As explained above, according to the present invention, since the configuration is adopted in which the pulse width and pulse current value for driving the pulse motor I are increased to increase the torque and reduce the number of steps at the time of starting and stopping, the step motor It is possible to shorten the time required for starting and stopping 1, reduce deviation in the stop position, and improve positioning accuracy.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of the present invention. FIG. 2 is a conceptual diagram of the present invention. FIG. 3 is an example of a current operation mode signal according to the present invention. FIG. 4 is an explanatory diagram of excitation at startup. Flowchart for explaining operation FIG. 6 shows a circuit example of a constant current amplifier according to the present invention. FIG. 7 shows an explanatory diagram of the structure and current waveform of a pulse motor. In the figure, 1 step motor 2: Constant current amplifier 3: Drive signal 4: Current operation mode signal 54 I10 board 6: Microprocessor

Claims (1)

[Claims] In a step motor drive method for starting and stopping a step motor, the step motor (1) is driven by a two-phase excitation step motor (1) and the step motor (1) based on an instructed drive signal and drive current. ) constant current amplifier (2) that supplies constant current to
The drive signal specified at startup (initially the pulse width is long)
A corresponding constant current is supplied to the step motor (1) according to the specified drive current (initially, the current value is large), and in the next step, each value is reduced and the pulse width of the drive signal and the drive are gradually adjusted. 1. A step motor drive method, characterized in that the current value is set to a specified value for a predetermined speed, and on the other hand, when stopping, the pulse width of the drive signal and the magnitude of the drive current are increased to cause the step motor to stop.