JP2851557B2 - Stepping motor drive controller - 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 drive control device using a micro step drive for the purpose of reducing the vibration of a stepping motor.

[0002]

2. Description of the Related Art A stepping motor rotates by an angle corresponding to the number of pulses by switching the current supply state of each winding by adding a command pulse from the outside. However, mechanical vibration generated immediately after the switching is problematic. Often becomes. As a countermeasure for this, there is a technique called a micro-step driving method. This aims to smooth the rotation by gradually changing the current distribution of each energized phase, but from the viewpoint of avoiding hardware complexity and giving a resolution with a remarkable substantial effect. In general, the transition of the current between the phases is divided from several stages to ten and several stages.

[0003]

Since the stepping motor also changes the back electromotive force by increasing or decreasing the pulse rate, in order to maintain the torque generated at high speed rotation, a high power supply voltage that overcomes the back electromotive force is maintained. At the same time, it is necessary to reduce the voltage so that an excessive current does not flow during low-speed rotation. Providing a current control function is generally the most effective means. However, when the pulse width control (hereinafter referred to as PWM control) resolution for the maximum voltage, that is, the voltage control accuracy of the inverter, is determined, the inverter circuit applies a sinusoidal voltage to each phase and controls the current. At the time of low voltage output and at the time of high voltage output, the resolution with respect to the voltage fluctuation width of each phase changes. Especially when the output voltage is small, the voltage accuracy is reduced and the waveform distortion becomes remarkable. Regarding the current detection method of the prior art,
For example, in the case of the two-phase motor having two independent windings A and B shown in FIG. 3 , each winding can be PWM-controlled by two sets of H-bridge inverters. A-phase coil 101, B-phase coil 10
2, current detection resistors 111 and 112 are connected to detect current of each phase. However, in a stepping motor having three or more phases of multi-phase windings, simply inserting resistors in each arm cannot detect the phase current of the motor. For this reason, when a three-phase winding is provided, for example, as shown in FIG. 4 , the current detector 210 is inserted into each phase from the inverter unit 40 of the stepping motor 220 and the detected value is input to the current control unit 200. The current detector 210 used here is of an insulated type, or requires a special configuration due to a large change in the voltage of the detection unit, resulting in high cost. By using these, the brushless servo of the stepping motor can be used. The price advantage over the motor is lost.

Therefore, if it is possible to adopt a power supply current detection method in which all phases are collectively used, it is cost effective. As another cause of the vibration phenomenon, there is a resonance phenomenon with respect to the vibration frequency inherent to the stepping motor, which can be solved by the above-described micro-step driving method.
For example, when there is torque ripple due to current waveform distortion, vibration may occur due to the approach between the torque ripple frequency and the motor resonance frequency. In this case, it is known that the use of mechanical means such as a damper to suppress the resonance phenomenon is effective in reducing the vibration, but by reducing the size of the torque ripple, it is possible to suppress the vibration generator itself. An object of the present invention is to provide a multi-phase stepping motor drive control device provided with a means for reducing the vibration of the stepping motor as described above.

[0005]

[Means for Solving the Problem] FIG.
It is a block diagram which shows the structure of a reference example. Figure 5
The micro-step drive uses an externally applied pulse.
Signal processing unit 70 and excitation signal generating unit 6 based on the
Inverter section by PWM control voltage signal generated at 0
Current realized by the PWM method at 40 and further provided separately
The current control is performed by the control unit 20. For this reason,
The output from the inverter unit 40 is a stepping motor 50
The PWM control resolution is set to 0
100% range, and separately from the current control unit 2
The mark on the inverter unit 40 is set so that the current becomes a predetermined current by 0.
Control the applied voltage. Therefore, when operating with low current,
However, since the PWM resolution does not decrease,
Generation can be suppressed and the stepping mode
The control of the data 50 can be performed. Means for solving the above problems include receiving a pulse train command signal for each direction from the outside, and making an angle proportional to the pulse amount proportional to the pulse amount by a speed based on the frequency of the pulse train command (hereinafter referred to as pulse rate). In the stepping motor drive control device that rotates by the specified angle, the stepping motor is driven by a polyphase inverter unit having a voltage control function for applying a stepwise output voltage to each phase, and a DC power supply unit and an inverter A current detector for detecting a total DC current between the units, and a current controller for controlling a voltage applied to the inverter unit for controlling the total DC current detected by the current detector to be constant, a motor being provided. Adjusting the waveform of the applied voltage by the polyphase inverter section,
The amplitude is controlled by the current control unit.

Since the stepping motor is a kind of synchronous motor, the stepped output voltage of the inverter has a frequency waveform synchronized with the back electromotive force of the motor.
Assuming that the number of phases of the stepping motor is n, a sine wave having the same cycle as one cycle 2π of the stepping motor back electromotive force or one cycle is divided into m, and this is sampled every 2π / m, A sinusoidal staircase voltage is applied to each phase with a phase difference of 2π / n, and the current detection signal of the current detector is passed through a smoothing circuit having a time constant larger than the natural frequency of the stepping motor. Detect and control this constant. Alternatively, the staircase output voltage of the inverter section is obtained by dividing one cycle of a trapezoidal wave or a sine wave in which a maximum voltage section and a minimum voltage section are respectively π / n for one cycle 2π of the stepping motor back electromotive force into m. This is sampled at intervals of 2π / m, and a trapezoidal step voltage is approximated to each phase and the phase difference is 2π / n.
Is configured to be applied in the relationship of

[0007]

With the above arrangement, the current control device controls the voltage applied to the inverter so as to adjust the detected current to a predetermined value, and controls the voltage applied to the stepping motor in cooperation with the current control and the inverter. By doing so, the vibration at the time of starting the stepping motor can be reduced.

[0008]

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. The same reference numerals in FIG . 2 denote the same parts as in FIG. FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention, and FIG. 3 is a characteristic diagram showing the relationship between the rotation angle (electrical angle) and the inverter output voltage when the number of motor phases is n = 3 in the second embodiment. is there. In FIG. 2 , when the number of phases of the stepping motor 50 is n, a sine wave having the same cycle as one cycle 2π of the speed electromotive force of the stepping motor 50 or one cycle is divided into m equal parts, and the divided angle is obtained. The inverter output voltage is sampled every 2π / m, and applied as a sinusoidal staircase voltage to each phase with a phase difference of 2π / n. As a result, each phase current becomes a sinusoidal current, so that the torque ripple of the generated torque can be reduced. For example, n
= 3, that is, in the case of a three-phase stepping motor, the current control unit 20 performs constant current control on the power supply side of the inverter circuit 40 that changes the phase current into a sine wave, thereby generating a six-fold frequency ripple in the phase current of the stepping motor. I do. This, as shown in FIG. 3, the stepping motor 50
For example, by using a current detection signal output from a current detection unit 82 constituted by a differential amplifier for current control via a smoothing circuit 83 having a large time constant with respect to the natural frequency of It is possible to eliminate the influence of ripples and perform current control with low vibration.

<Embodiment 2> FIG. 2 is a block diagram showing the configuration of Embodiment 2 of the present invention, and FIG.
FIG. 13 is a characteristic diagram illustrating a relationship between a rotation angle (electrical angle) and an inverter output voltage in the case of No. 3; In FIG. 3, when the number of phases of the stepping motor 50 is n, a sinusoidal wave having the same period as one cycle 2π of the speed electromotive force of the stepping motor 50 or one cycle is divided into m equal parts, and the divided angle is obtained. The inverter output voltage is sampled every 2π / m, and applied as a sinusoidal staircase voltage to each phase with a phase difference of 2π / n. As a result, each phase current becomes a sinusoidal current, so that the torque ripple of the generated torque can be reduced. For example, in the case of n = 3, that is, in the case of a three-phase stepping motor, the current controller 20
, A six-fold frequency ripple occurs in the phase current of the stepping motor. As shown in the embodiment of FIG. 2, this is applied to the natural frequency of the stepping motor 50 via a smoothing circuit 83 having a large time constant, and for example, the current which is the output of a current detector 82 constituted by a differential amplifier. By using the detection signal for current control,
The influence of ripple included in the detection signal can be removed, and current control can be performed with low vibration.

[0010]

[0011]

According to the present invention, the vibration at the time of starting the stepping motor can be reduced by a simple structure in which the power supply current of each phase winding of the stepping motor is collectively detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

2 is a characteristic diagram showing the relationship between the rotational angle and the inverter output voltage in Example of the present invention.

FIG. 3 is a current detection circuit diagram for performing PWM control of a two-phase winding stepping motor using two conventional inverters having an H-bridge configuration.

FIG. 4 is a block diagram showing current detection of a winding in a conventional three-phase stepping motor.

FIG. 5 is a characteristic diagram showing a relationship between a rotation angle and a trapezoidal wave inverter output voltage in a reference example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Main power supply 20 ... Current control part 30 ... Smoothing capacitor 40 ... Inverter part 50 ... Stepping motor 60 ... Excitation signal generation part 70 ... Signal processing part 81 ... Power supply current detection resistance 82 ... Current detection part 83 ... Smoothing circuit 101 ... 2 A-phase coil of phase stepping motor 102: B-phase coil of two-phase stepping motor 111: A-phase power supply current detection resistor 112: B-phase power supply current detection resistor 120: switching transistor 200: current control unit 210: current detector 220: synchronization Motor CWP: Forward rotation input command pulse CCWP: Reverse input command pulse if1, if2, ifa, ifb: Current detection signal ifu, ifv, ifw: Current detection signal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shunichi Kawamata 3-93 Aioimachi, Kiryu-shi, Gunma Japan Servo Co., Ltd. (56) References JP-A-3-93495 (JP, A) JP-A-53- 813 (JP, A) JP-A-7-46894 (JP, A) JP-A-6-153590 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02P 8/18 H02P 8 / 12

Claims (1)

(57) [Claims] A pulse train command for each direction from the outside,
A 3-phase scan <br/> stepping motor drive control device to rotate the stepping motor the angle in proportion to the pulse amount at a rate in accordance with the frequency of the pulse train command, stepped output to each phase of the stepping motor An inverter unit having a voltage control unit for applying a voltage; a current detection unit provided between the inverter unit and the DC power supply unit for detecting a DC current; And a current control unit for controlling a voltage applied to the inverter unit so as to adjust to a value of: a stepping motor drive control device for controlling an applied voltage to the stepping motor in cooperation with the current control unit and the inverter unit in, stepped output voltage generated by the inverter unit is positive
Sine wave or this sine wave cycle is divided into m equal parts and 2π / m
The voltage value sampled for each angle is
When applied with a phase difference of 2π / 3 to the three phases of
To the detection signal of the current detector of the stepping motor
Via a smoothing circuit with a time constant greater than the natural frequency
Input to a current control unit to control the DC current to a predetermined value
Stepping motor drive control device, characterized in that.