JP3368105B2 - Stepping motor control device and stepping motor control method - Google Patents

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 system, and particularly to a case where it has a plurality of drive modes, that is, a case where it is driven by means such as slow-up / down or a constant speed operation at a plurality of speeds. In this case, the present invention relates to a stepping motor control method.

[0002]

2. Description of the Related Art A constant voltage drive system is a typical example of a conventionally known drive system for a stepping motor. This method is widely used because it has a simple circuit configuration and is the cheapest in terms of cost. On the other hand, a constant current drive method is known as a drive method for coping with high-speed rotation. This is to detect a current value flowing in a motor winding and drive a switching element such as a transistor according to the detected current so as to reach a set current value. In the former constant voltage type stepping motor drive circuit, when the driving cycle of the stepping motor becomes high, the inductance of the motor winding delays the rise of the current and causes a torque decrease, which is a drawback that high speed rotation cannot be performed. Further, in the constant current method, high-speed rotation of the motor can be realized, but there is a drawback that the circuit is complicated and the cost is increased because a current detection function and the like are required. Generally, the torque of the stepping motor decreases as the rotation speed increases. Therefore, if the current value is set so that the required torque can be obtained at the high speed rotation, there is a problem that the motor vibrates due to the excessive torque at the low speed rotation and the noise is easily generated. As a motor drive system that solves these problems and enables low-cost and low-noise drive, JP-A-6-
The drive system shown in Japanese Patent No. 54590 has been proposed by the applicant. This is provided with a plurality of pulse generating means whose duty can be set and a means for pulse-width-modulating driving each phase of the stepping motor by the pulse generated by the pulse generating means, and the duty of the pulse within one step of driving the stepping motor. This is a drive system that changes the ratio, rotates the motor at a higher speed and lower vibration than a general constant voltage drive in an open loop, and realizes a simpler and cheaper circuit configuration than a low current drive system.

[0003]

Even in such a drive system, the difference in the rising characteristics of the coil current due to the excitation state of the other phase in the motor, that is, the deviation of the optimum duty depending on the rotation direction, and the bias due to the asymmetry of the driver characteristics. There is a problem in that a desired current value cannot always be obtained and the motor vibrates to generate noise due to a difference in characteristics depending on the current direction of the bowler motor.

Further, since the number of timing divisions of the duty change in each phase is constant regardless of the length of the phase, that is, the rotation speed, the coil current cannot be idealized depending on the rotation speed, which causes vibration. There was a case.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a stepping motor control system in which optimum duty ratio data is selectively used according to the driving of the motor.

[0006]

To achieve the above object, according to the present invention, a pulse width modulation means for generating a pulse width modulation signal by setting duty ratio data and the pulse width modulation signal are provided. A stepping motor control device comprising a drive circuit for inputting and outputting a drive signal to a stepping motor, wherein a storage means for storing the duty ratio data in which the characteristic difference of the operation timing of the drive circuit is corrected in advance, By setting the duty ratio data stored in the storage means in the pulse width modulation means in accordance with the rotation direction of the stepping motor, the drive circuit is different between the forward rotation and the reverse rotation of the motor. The drive signal having a current value is output. Also,
By setting the duty ratio data, a pulse width modulation means for generating a pulse width modulation signal, a drive circuit for inputting the pulse width modulation signal and outputting a drive signal to a stepping motor, and an operation timing of the drive circuit A stepping motor control method comprising: a storage unit that stores the duty ratio data in which characteristic differences are corrected, wherein the duty ratio data stored in the storage unit is pulsed according to a rotation direction of the stepping motor. And a step of setting the width modulation means, and a step of outputting the drive signals of different current values by the drive circuit when the motor rotates in the forward direction and in the reverse direction.

[0007]

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a control circuit of a stepping motor drive circuit. In FIG. 1, 1 is a microcontroller for controlling a motor, 2 is a built-in microcontroller, and pulse signals E and F capable of setting a frequency and a duty ratio. A pulse width modulation unit (hereinafter referred to as a PWM unit) 3 for outputting a signal, an output port for outputting a coded stepping motor drive signal A, B, C, D, 8 is a microcontroller 1 A programmable timer unit 9 incorporated in the ROM, 9 is a ROM storing data such as the drive speed of the motor 4 and the PWM duty ratio, and the data is read by the microcontroller 1.

FIG. 2 shows a stepping motor drive circuit. In FIG. 2, 4 is a two-phase stepping motor connected in bipolar, 4 ₁ and 4 ₂ are coil windings of the two-phase stepping motor 4, 5 _1a , 5 _2a , 5 _3a , 5 _4a and 5 _1b , 5 _2b , 5 _3b , 5 _4b control the current flowing through the coil windings 4 ₁ and 4 ₂ of the stepping motor 4 by the pulse signals E and F, and drive signal A, Transistor for phase excitation and current selection by B, C, D, 6 _1a ,
6 _2a , 6 _3a , 6 _4a and 6 _1b , 6 _2b , 6 _3b , 6 _4b are AND circuits for performing logical operation of drive signals A, B, C, D and pulse signals E, F, 7 _1a , 7 _2a , 7 _3a , 7 _4a and 7 _1b ,
7 _2b , 7 _3b and 7 _4b are transistors 5 _1a , 5 _2a , 5 _3a and 5
It is a flywheel diode that makes a current flow path when _4a and 5 _1b , 5 _2b , 5 _3b , 5 _4b are turned off. Coil winding of the stepping motor 4 as shown in FIG. 2 in this embodiment, 4 ₁ and 4 2 sets of driving circuit ₂ for supplying a current to it is configured symmetrically on the same integrated circuit. Drive signal A
Since C and B and B and D are in an inversion relationship, respectively, it is possible to control with two lines of drive signals A and B or C and D.

Next, the operation of the above configuration will be described.

The drive signals A, B, C and D are signals for selecting the direction of the current flowing through the coil windings 4 ₁ and 4 ₂ of the motor 4, and these drive signals A, B, C and D are A logical operation is performed by the AND circuits 7 _1a , 7 _2a , 7 _3a , 7 _4a and 7 _1b , 7 _2b , 7 _3b , 7 _4b with the pulse signals E and F, and the operation output is the transistor 5 _1a , 5 _2a , 5 _3a , 5 _4a and 5
_1b , 5 _2b , 5 _3b and 5 _4b are on / off controlled to pass a current through the coil windings 4 ₁ and 4 ₂ of the motor 4. The timing at which the drive signals A, B, C, D are changed, that is, the phase drive order and the step time are determined by the microcontroller 1 using the timer unit 8. By selecting the driving order, the rotation direction of the motor 4 is determined, and by adjusting the step time, control of each mode such as acceleration, deceleration, and constant speed driving is performed.

The microcontroller 1 also causes the PWM unit 2 to output pulse waveforms E and F. These pulses are set to have a constant frequency and to be output at a predetermined duty for each constant timing depending on the speed. The microcontroller 1 also uses the timer unit 8 to determine the timing for changing the duty ratio. The transistors 5 _1a , 5 _2a , 5 _3a , 5 _4a and 5 are formed by the drive signals A, B, C and D and the pulse signals E and F.
_1b , 5 _2b , 5 _3b and 5 _4b are on / off controlled to supply a current to the coil windings 4 ₁ and 4 ₂ of the motor 4, and by repeating this, windings 4 ₁ and 4 ₂ of the motor 4 are supplied. The flowing current can be controlled by the duty ratio of the pulse signals E and F.

An example of PWM duty data stored in the ROM 9 is shown in FIGS. Number 1 in the top row
To 8 and 9 to 16 are ROM addresses assigned for convenience, and the numerical values in the lower row are the PWs stored in each address.
M duty ratio is shown.

Motor drive waveforms based on the PWM duty ratio data of FIGS. 3-1 and 3-2 are shown in FIGS. 4-1 and 4-2. The pulse signals E and F here are not actual pulse waveforms, but the duty ratios of the pulses are expressed by their signal levels. Here, FIG. 4-1 is a drive waveform when the motor is rotated in the forward direction, and FIG. 4-2 is a drive waveform when the motor is rotated in the opposite direction.

In FIG. 4A, the microcontroller 1
Changes the drive signals A and C and sets the PWM pulse output to 50% according to the value 50 stored in the address 9 of the ROM 9. After that, when the time of 1/4 of the step cycle has elapsed, the PWM duty ratio is set to 70% according to the numerical value 70 stored in the address 10 of the ROM 9. Thereafter, similarly, the PWM data stored in the address 9 to the address 16 is sequentially read from the ROM 9 and the duty ratio is set.

Regarding the pulse signal F, FIG.
As shown in FIG. 5, a value which is 90 degrees out of phase with the pulse signal E is set in the same procedure, but different data stored at different addresses in the ROM 9 are used. In this embodiment, the values of address 1 to address 8 which are set to be 10% lower than the pulse signal E by the PWM duty ratio are used.

Since the current flowing through the motor 4 is affected by the inductance of the motor windings 4 ₁ and 4 ₂ and the back electromotive force and other winding currents, the PWM duty ratio and the motor current are not generally proportional. It is possible to control the current waveform in a sine wave shape by storing in the ROM 9 duty ratio data in which the influence of is corrected in advance.

[0019] Here, the pulse signals E and PWM duty ratio to be used differs from a pulse signal F driving signal A, and the coil winding 4 ₁ controlled by C and the pulse signal E,
Driving signal B, and in order to have different current characteristics at the time of actual driving by the influence coil winding 4 ₂ of each other controlled by D and the pulse signal F.

Taking the moment when a current starts to flow in one motor coil as an example, the inductance changes depending on the state of the other coil current at that time, which affects the current characteristics.

As shown in FIG. 4, the driving order of the driving signals A, B, C and D has the opposite relationship in the rotation direction of the motor.

When rotating in the forward direction, the drive signals B and D are driven with a delay of 90 degrees from the drive signals A and C. On the contrary, at the time of reverse rotation, the drive signals B and B are advanced by 90 degrees from the drive signals A and C.
D is driven.

For the above reason, the current characteristics of the coil also have an opposite relationship between forward rotation and reverse rotation. Taking the case of forward rotation as an example, when a current is started to flow in the motor coil winding 4 ₁ + direction, the maximum current in the − direction flows in the other coil winding 4 ₂ . Therefore, the coil winding 4 ₂
Current does not easily flow into the coil winding 4 _{2. On the other hand} , when starting to flow a current in the + direction in the coil winding 4 ₂ , the current in the + direction also flows in the coil winding 4 ₁ , so it does not hinder the current. . For the above reason, a control signal having a large PWM duty ratio is applied to the coil winding 4 ₁ that is difficult to flow during normal rotation so that both actual coil current values are corrected.

During reverse rotation, the phase relationship of the coil current is opposite to that described above, so the duty ratio data stored in addresses 9 to 16 of the ROM 9 is applied to the pulse signal F side as shown in FIG. 4-2. things a large signal of PWM duty ratio applied to the coil windings 4 ₂ side, on the contrary, using the duty ratio data stored in the address 8 from address 1 to the pulse signal E side.

(Embodiment 2) In Embodiment 1, in order to correct the current characteristic depending on the rotation direction of the motor, the control is performed by different PWM duty ratios depending on the rotation direction.

In an actual circuit, however, another factor affecting the driving conditions is the difference in the current characteristics due to the characteristic deviation of the driving transistor. In the second embodiment, in the same configuration as the first embodiment, a motor drive driver IC
An example in which the characteristic difference of is corrected by the PWM duty ratio is shown.

The driver circuit will be described with reference to FIG. Hybrid-connected two-phase stepping motor 4
The coil windings 4 ₁ and 4 ₂ are connected to the circuit blocks inside the target integrated circuit. Circuit blocks connected to the winding 4 ₁ controlled by the drive signals A and C and the pulse signal E and the drive signals B and D
And the winding 4 controlled by the pulse signal F
_Since the circuit blocks connected to ₂ are exactly the same, the circuit on one side will be described.

The rotation speed and direction of the stepping motor 4 are controlled by changing the drive signals A, B, C, D and the pulse signals E, F as shown in FIG. 4-1 or FIG. 4-2. The operation of the driver circuit at that time has been described with reference to the example 1.

The drive signal B is "H" and the drive signal D is "L".
Then, the input on one side of the AND circuits 6 _2b and 6 _3b connected to the transistors 5 _2b and 5 _3b becomes "H" level, and the transistors 5 _2b and 5 _3b between the "H" level of the pulse signal F are
Turns on. A positive current flows through the coil winding 4 ₂ connected during this time. On the contrary, when the drive signal B becomes "L" and the drive signal D becomes "H", the transistors 5 _1b and 5 _4b are turned on, so that the current flows in the same coil winding 4 ₂ in the opposite direction. .

However, in the driver integrated circuit, a certain characteristic difference occurs in the operation timing of the transistor 5 due to the internal wiring length and the arrangement of the transistors. The combination of the transistors 5 _2b and 5 _3b has slightly better frequency characteristics and faster operation than the combination of the transistors 5 _1b and 5 _4b . Especially in the rising characteristics, the difference is remarkable. FIG. 6 shows the output response characteristic with respect to the input pulse width. OU here
T3 is an output characteristic when the transistors 5 _1b and 5 _4b are turned on and is a reverse current in this embodiment, and OUT4 is an output characteristic when the transistors 5 _2b and 5 _3b are turned on and is a forward current.

As is apparent from this figure, even if the PWM duty ratios given by the pulse signals E and F are the same, a deviation occurs in the time when the circuit is actually turned on. As a result, the same coil winding causes a phenomenon that the current value varies depending on the current direction,
It causes vibration and noise. If the same PWM duty ratio is applied, OUT3, that is, the forward current of the transistor 5 _1b , has a faster response time of the noise transistor, and as a result, the ON time becomes shorter and the current becomes smaller.

In the integrated circuit of this embodiment, since the internal circuits are symmetrically arranged as described above, the circuits connected to the coil windings 4 ₁ and 4 ₂ have the same tendency.

Therefore, as shown in FIG. 5, the PWM duty ratio data extracted from the ROM 9 is selected in the direction of current, and in the forward direction, from the address 9 to the address 1 of the ROM 9 is selected.
6 is used, and the data stored in addresses 1 to 8 is used in the reverse direction. In this way, the deviation of the driver is corrected.

[0034]

As described above in detail, according to the present invention, by setting the duty ratio of the pulse for each timing determined by the timer function, the duty of the pulse can be changed within one step of the stepping motor drive. Since the ratio can be changed and the duty ratio data can be made different in the forward rotation direction of the motor at the same drive speed of the same phase of the stepping motor, the optimum duty ratio data can be selected according to the drive of the motor. It is possible to solve the problem of vibration and noise of the motor caused by the difference in the characteristics in the rotation direction. Further, since a plurality of duty ratio data are independently set for each phase of the stepping motor, it is possible to solve the problem caused by the difference in characteristics between the phases of the motor.

Further, the duty ratio data using the same drive speed for the same phase of the stepping motor is made different between the forward current drive and the reverse current drive, and the optimum duty ratio data is selected according to the drive of the motor. Therefore, it is possible to correct the characteristic that the drive circuit tends to have. As described above, according to the present invention, the deviation of the drive circuit can be corrected without taking any special means in terms of circuit.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a stepping motor drive circuit showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a motor drive circuit controlled by the control circuit of FIG.

3A is a diagram showing a first example of PWM duty ratio data stored in the ROM of FIG. 1. FIG. (2) is a diagram showing a second example of the PWM duty ratio data stored in the ROM of FIG. 1.

FIG. 4 (1) is a drive waveform diagram during motor reverse rotation based on the PWM duty ratio data shown in FIGS. 3-1 and 3-2. (2) is a drive waveform diagram at the time of normal rotation of the motor based on the PWM duty ratio data shown in FIGS. 3-1 and 3-2.

FIG. 5 is a drive waveform diagram of the motor showing PWM duty ratio data selected in the direction of current.

FIG. 6 is an output response characteristic diagram with respect to an input pulse width.

[Explanation of symbols]

1 Maskro Controller 2 Pulse Width Modulation Unit 3 Output Port Built in Maskro Controller 1 2 Phase Stepping Motor 4 ₁ , 4 ₂ 2 Phase Stepping Motor 4 Coil Winding 5 _1a , 5 _2a , 5 _3a , 5 _4a 5 _1b , 5 _2b , 5 _3b , 5 _4b Transistors 6 _1a , 6 _2a , 6 _3a , 6 _4a , 6 _1b , 6 _2b , 6 _3b , 6 _4b AND circuit 7 _1a , 7 _2a , 7 _3a , 7 _4a , 7 _1b , 7 _2b , 7 _3b , 7 _4b Flywheel diode 8 Timer unit 9 ROM

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-6-54590 (JP, A) JP-A-1-218393 (JP, A) JP-A-5-96072 (JP, A) JP-A-3- 65097 (JP, A) JP 62-155799 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 8/00

Claims (3)

(57) [Claims] 1. By setting duty ratio data,
Pulse width modulation means for generating a pulse width modulation signal;
Input the pulse width modulation signal and drive it to the stepping motor.
With a drive circuit that outputs a motion signal
A controller for correcting the characteristic difference of the operation timing of the drive circuit in advance.
The storage means for storing the duty ratio data and the above-mentioned items depending on the rotation direction of the stepping motor.
The duty ratio data stored in the storage means
By setting the width modulation means, the normal rotation of the motor
At the time of reverse rotation, the drive circuit drives at different current values.
Stepping motor control characterized by outputting signals
Your device . 2. The driving circuit comprises a transistor,
The difference in the characteristics of the operation timing is the previous
And the transistor based on the wiring length inside the drive circuit
The stepping motor control device according to claim 1, wherein the stepping motor control device has the following operating characteristics . 3. By setting duty ratio data,
Pulse width modulation means for generating a pulse width modulation signal;
Input the pulse width modulation signal and drive it to the stepping motor.
Drive circuit for outputting motion signal and operation timing of the drive circuit
Stores the duty ratio data with the corrected characteristic difference
And a stepping motor control method provided with
There, depending on the rotation direction of the stepping motor, the Symbol
The duty ratio data stored in the storage means
The drive circuit is different between the step of setting the width modulation means and the forward rotation and the reverse rotation of the motor.
And a step of outputting the drive signal of a current value.
Characteristic stepping motor control method .