JPH05304792A - Servo control device - Google Patents

Abstract

(57) [Summary] [Purpose] Stable and smooth current control is possible even when the load on the servo motor changes. [Configuration] A for observing the main circuit DC voltage of the inverter 6
The D / D converter 14 and the CPU 15 that turns on the regeneration transistor 5 when the main circuit DC voltage exceeds a value that should be observed when the servo motor 13 is in an unloaded state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier for converting an alternating current into a direct current, a current control type inverter for inputting the converted direct current and converting it into an alternating current, and supplying it to a servomotor, and between the rectifier and the inverter. And a servo control device including the regeneration transistor provided in the.

[0002]

2. Description of the Related Art FIG. 5 is a schematic configuration diagram showing a conventional example of a servo control device.

The rectifier 42 is composed of, for example, a thyristor bridge, and inputs a three-phase alternating current composed of R phase, S phase, and T phase through a breaker 41 (hereinafter referred to as MCCB41),
The output terminal of the rectifier 42 is a capacitor 43 that smoothes the output of the particle sizing device 42 into a main circuit direct current, a regenerative resistor 44 and a regenerative transistor 45 that are connected in series.
And a current-controlled inverter 46 including six power transistors are connected in parallel with each other. The regenerative resistor 44 and the regenerative transistor 45 are used for discharging when a main circuit DC voltage higher than the main circuit withstand voltage is generated.

The three conductors U, V, W of the inverter 46 are connected to the servomotor 53 between the three-phase alternating current, and two of these conductors U, V are provided with current detecting resistors in the middle. 52 is provided. Each current detection resistor 52
Both ends of are connected to the current amplifier 54 by conductors (not shown). The current amplifier 54 outputs a signal obtained by amplifying a deviation between a current command given in advance and a voltage between both ends of each current detection resistor 52 (feedback of a voltage proportional to the current of the servo motor 53). Current amplifier 5
The signal output terminal of 4 is connected to the input terminal of the base drive 55, and the output terminal of the base drive 55 is connected to the bases of the power transistors of the inverter 46.

This servo control device includes a servo motor 53.
The output current is controlled so that a current based on the current command is supplied to the servo motor 53 regardless of the load.

In addition, the output voltage controllable forward and reverse rectifiers connected in anti-parallel, the L and C filters on the output side of the rectifier, and the DC power passed through this filter are converted into variable frequency AC power. And an output voltage controllable inverter circuit that supplies a load to the load.The fluctuation range of the rectifier output DC voltage is narrower than the DC voltage value that changes in response to fluctuations in the AC input voltage when the forward side rectifier is uncontrolled. That can regenerate the load feedback power controlled by the
No. 237), a controllable rectifier connected to an AC bus, a DC intermediate circuit having a coil and a capacitor, and the output of the controllable rectifier is input via this DC intermediate circuit to supply power to a motor. In the electric motor control device for controlling the speed of the electric motor, the direct current intermediate inverter is provided with a voltage source inverter, and a speed control circuit for controlling the output frequency and the output voltage of the inverter based on the set value of the speed setter. An inverter input DC current detection circuit that detects the magnitude of the DC current supplied from the circuit to the inverter, and a current controller that adjustably feeds back the output current of the controllable rectifier according to the detected value detected are provided. Those (see Japanese Patent Publication No. 61-109491) are known.

[0007]

In the above-mentioned conventional servo control device, when the main circuit DC voltage becomes high due to load fluctuation of the servomotor, the increased main circuit DC voltage is immediately lowered and becomes constant. It has no means to control it. In this type of servo control device, it is known that the response of the current becomes faster when the DC voltage of the main circuit becomes higher and the response becomes slower when it becomes lower. If the current amplifier gain is increased in order to speed up the part where the response is slow, there is a problem that vibration may occur at the part where the response is fast.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a servo control device which controls a main circuit DC voltage to be constant even if there is a load change of a servo motor and enables stable and smooth current control. To do.

[0009]

In the servo control device of the present invention, the observing means for observing the DC voltage on the DC input end side of the inverter, and the observed DC voltage are substantially in the unloaded state of the servo motor. And a control means for turning on the regeneration transistor when the value exceeds a value to be observed.

The control means preferably turns off the rectifier when turning on the regeneration transistor.

[0011]

[Operation] By turning on the regeneration transistor,
The DC voltage of the main circuit does not exceed the value that should be observed in the unloaded state of the servo motor, but becomes almost constant. Therefore, the response speed of the current becomes almost constant, and stable and smooth control becomes possible.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a servo control device of the present invention, and FIG. 2 is a block diagram showing an example of a rectifier 2.

The rectifier 2 comprises, for example, three thyristors 21, 22, 23 and three diodes 24, shown in FIG.
It consists of a thyristor bridge consisting of 25 and 26
Three-phase alternating current consisting of three phases, S phase and T phase
(Referred to as CCB1) for rectification. Rectifier 2
At the output end of the capacitor, a capacitor 3 for smoothing the output of the rectifier 2 into a main circuit DC, a regenerative resistor 4 and a regenerative transistor 5 connected in series, and a current control type including six power transistors The DC input terminal of the inverter 6 is connected to each other in parallel by two conductors P and N.

The three conductors U, V, W of the inverter 6 are 3
It is connected to a servomotor 13 for phase alternating current, and a current detecting resistor 12 is provided in the middle of each of the two conducting wires U and V of these. Both ends of each current detection resistor 12 are connected to a conductor and an A / D converter (not shown), and the output terminal of this A / D converter is the central processing unit 1.
5 (hereinafter referred to as CPU 15) is connected to the input end. The CPU 15 outputs a signal corresponding to an amplified value of a deviation between a current command given in advance and a voltage across both ends of each current detection resistor 12 (feedback of voltage proportional to the current of the servo motor 13), and the regeneration transistor 5 Is a control means for turning on. CP
The signal output end of U15 is connected to the input end of the base drive 16 and the base of the regenerative transistor 5, and the output end of the base drive 15 is output to the base of each power transistor of the inverter 6.

A is connected to the two conductors P and N for passing the direct current of the main circuit.
Two input terminals of the / D converter 14 are connected to each other, and an output terminal of the A / D converter 14 is connected to an input terminal of the CPU 15. The A / D converter 14 constitutes an observation means for observing the main circuit DC voltage of the inverter 6.

Next, the operation of this embodiment will be described.

FIG. 3 is a timing chart showing the phase of the AC power supply and the ignition timing of the thyristor bridge 2 in this embodiment.

First, in the CPU 15, the A / D converter 14
The main circuit DC voltage (voltage between PN) is input. When the main circuit DC voltage is high, the CPU 15 causes the regeneration transistor 5 to
Is turned on to discharge the voltage charged in the capacitor 3 and all the thyristors 21, 22, 23 of the thyristor bridge 2 are turned off to lower the DC voltage of the main circuit. When the main circuit DC voltage is low, the thyristors 21, 22, 23 of the thyristor bridge 2 are turned on so that the main circuit DC voltage becomes high. In order to set a certain constant voltage V, each thyristor 21, 22, 23 is turned on and off at the timing shown in FIG.

During the above operation, the level of the main circuit DC voltage is
A value that should be observed when the servo motor 13 is in a no-load state is used as a reference. This standard is + 10% to − depending on the loss and variation of the servo control device and the servo motor 13.
It may be changed by about 20%.

Further, the CPU 15 controls the output current so as to supply the current based on the current command to the servo motor 13 regardless of the load of the servo motor 13.

FIG. 4 is a current control block diagram of this embodiment.

Current amplifier gain K _{i for} proportional operation
[V / A] is K _i = (main circuit DC voltage / 2) / saturation current value. However, the saturation current value is the saturation value of the output current of the CPU 15.

In FIG. 4, R is the resistance value of the servo motor 13, L is the reactance of the servo motor 13, K _t is the torque constant of the servo motor 13, and J is the overall inertia.
K _e is an induced voltage constant.

Considering that the induced voltage is corrected, the current amplifier transfer function is as follows.

I / i _ref = K _i / (K _i + R + SL) The cutoff frequency f _c is as follows.

F _c = (K _i + R) / (2πL) = (main circuit DC voltage / 2 / saturation current value + R) / (2πL) Therefore, by keeping the main circuit DC voltage constant,
A stable response is always obtained.

[0028]

As described above, according to the present invention,
Since the DC voltage of the main circuit is kept constant, a constant current response can always be obtained, and a high-speed response can be achieved as a whole, and stable and smooth current control can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a servo control device of the present invention.

FIG. 2 is a configuration diagram showing an example of a rectifier 2.

FIG. 3 is a timing chart showing the phase of the AC power supply and the ignition timing of the thyristor bridge in this embodiment.

FIG. 4 is a current control block diagram of the present embodiment.

FIG. 5 is a schematic configuration diagram showing a conventional example of a servo control device.

[Explanation of symbols]

 1 MCCB 2 Thyristor bridge 3 Capacitor 4 Regenerative resistor 5 Regenerative transistor 6 Inverter 12 Current detection resistor 13 Servo motor 14 A / D converter 15 CPU 16 Base drive

Claims (2)

[Claims] 1. A rectifier for converting alternating current to direct current, a current control type inverter for inputting the converted direct current to convert to alternating current and supplying it to a servomotor, and a rectifier provided on the direct current input end side of the inverter. In a servo controller including a regenerative transistor, an observing unit that observes a DC voltage on the DC input end side of the inverter, and the observed DC voltage is observed when the servo motor is in a no-load state. A servo control device comprising: a control unit that turns on the regeneration transistor when the value exceeds a predetermined value. 2. The servo control device according to claim 1, wherein the control means turns off the rectifier when turning on the regeneration transistor.