JPS6295998A - Controller for motor - Google Patents

Abstract

PURPOSE:To generate torque in a motor, and to reduce vibrations extremely by mounting a fixed-bias generating circuit and supplying the motor with predetermined forward-rotation and reverse-rotation motor currents even when motor currents are small. CONSTITUTION:An output from a referance-voltage generating circuit 5 and an output from a fixed-bias generating circuit 38 surrounded by a dotted line are applied to a comparator circuit 4. Consequently, forward-rotation and reverse rotation balanced motor currents are made forcibly to flow through a motor and torque is generated even when motor load is small and motor currents are small. Since the balanced motor currents are made to flow, a motor shaft is constrained at a certain fixed value while being revolved, is difficult to be affected by the load fluctuation of a motor output shaft, and is not affected by instantaneous load fluctuation, thus extremely reducing vibrations.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the drive of the final stage output element of a servo motor control device (hereinafter referred to as servo amplifier), which can control rotation using a final stage output element consisting of a transistor or thyristor. The present invention relates to a device for controlling signals to a circuit.

2. Description of the Related Art In conventional servo amplifiers, the comparator outputting forward and reverse rotation signals to the drive circuit has only inputs determined by a reference wave, velocity feedback, and current feedback.

Problems to be Solved by the Invention When a servo amplifier is used to drive a servo motor to operate a robot, the operating speed of the robot is the welding speed (
If the speed is low (about 40cm/mm to 8mm/min), the motor current is small, and in this case, vibration will occur in the robot machine body, and in the case of welding robots, the tip of the welding wire may shake, resulting in poor welding. Ta.

Furthermore, at high speeds, the motor current becomes small when each axis of the robot moves in the direction of gravity, such as from top to bottom, and in this case too, large vibrations may occur in the robot machine body.

Vibration at high speeds has a particularly negative effect on speed reduction mechanisms, causing backlash and bolt loosening.

Note that the state of vibration generation differs depending on the robot type (parallel link type, independent joint type, scalar type, etc.).

It also differs depending on each axis of each robot.

Conventionally, when vibration occurs, it has been dealt with by changing the gain of the servo amplifier's speed control circuit or the OP amplifier used in the current control circuit, but in the case of low speeds such as welding speeds, experimental results suggest that the gain should be changed. Raising the gain tended to reduce vibrations, but this could sometimes be a practical problem; on the other hand, increasing the gain tended to cause harsher vibrations no matter the robot's posture at high speeds.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a servo amplifier that can extremely reduce vibrations generated in the mechanical body of a robot when the robot is operated by driving a servo motor using the servo amplifier.

Means for Solving the Problems The present invention provides the ability to detect forward and reverse rotations below a certain reference motor current that is separately provided at the input of a comparator circuit that outputs forward and reverse rotation signals to the drive circuit. A fixed bias generation circuit is provided which provides a fixed bias equivalent to rotation.

By applying a fixed bias below a set standard motor current, even when the motor load is small and the motor current is small, constant forward and reverse rotation motor currents are supplied to the motor, and torque is applied to the motor. generates vibrations and minimizes them to an extremely low level.

That is, in addition to the current flowing due to the load applied to the output shaft of the motor, a motor current that is balanced between forward rotation and reverse rotation is forced to flow below a set reference motor current to generate torque.

By flowing a balanced motor current, the motor shaft is constrained to a certain value while rotating, making it less susceptible to load fluctuations on the motor output shaft and unaffected by instantaneous load fluctuations. Vibration becomes extremely small.

Example ``Hereinafter, one embodiment of the present invention will be described based on the drawings.

Figure 1 is a block diagram of the motor control device, with input terminal 1
When a command voltage Ei is applied to the motor, signals such as motor forward/reverse directions are obtained through the speed control circuit 2, current control circuit 3, and comparator circuit 4, and are amplified by the drive circuit 6, and then P
A signal is given to the WM power circuit 7, which controls the switching of a control element such as a power transistor, which is the final output element. When a control element such as a power transistor is switched, the servo motor 9 rotates in forward and reverse directions. TGlo generates a voltage proportional to the reverse rotation speed and is fed back to the speed control circuit 2.

The current detection circuit 8 is connected in series with the servo motor 9 and generates a voltage proportional to the magnitude of the DC current, which is fed back to the current control circuit 3.

The comparator circuit 4 is supplied with the output of the reference voltage generation circuit 6 and the output of a fixed bias generation circuit 38 surrounded by a dotted line.

Further, a DC voltage is supplied to the PWM power circuit 7 from a DC power supply circuit 11.

Details of the humpator circuit 4 will be explained with reference to FIG. Further, details of the drive circuit 6 will be explained with reference to FIG. Furthermore, a PWM power circuit 7 and a DC power circuit 11
The details will be explained with reference to FIG.

In FIG. 2, the outputs of comparators 14 and 16 are applied to transistors 16-19 and photocouplers 20-2.
Controls the primary side of 3.

Resistors 40 and 41 are provided to provide the output of the fixed bias generation circuit 38 to the co/parators 14 and 15.

Next, referring to FIG. 3, FIG. 3 shows a drive circuit for only one element of the power transistor 7. 24 is a secondary side light receiving element of the photocoupler 2o, and the output of this light receiving element 24 is Okay, transistor 25 is ON L.
, when transistor 25 is turned on, transistor 27 is turned off, , transistor 26 is turned on and supplies a pace current to the power transistor.

Explaining FIG. 4, the circuit configurations of 6b, 6c, and 6d are exactly the same as 6a, and the drive circuit 6b receives the signal from the photocoupler 21 in FIG. The drive circuit 6d is controlled to control switching of the power transistors 34 to 37, and rotate the motor 9 in forward and reverse directions. 34-3
7 is a freewheeling diode.

FIG. 5 shows the output of the comparator circuit when only the signals 12 and 13 are input to the comparator circuit 4, and 42 is the output of the current control circuit 3 and the feedback voltage of the signal 12. The polarity is reversed.

b shows the drive signal of the photocoupler 20 in FIG. 2, that is, the output of the drive circuit 6a in FIG. 4.

Similarly, C is the photocoupler 22, drive circuit 6cSd is the photocoupler 23, and drive circuit 6d.

e indicates a signal to the photocoupler 21 and the drive circuit 6b.

6, comparator circuit 4 has signals 12.
This figure shows a case where the feedback voltage signal 12 is zero volts when only 13 inputs are given.

That is, this is a case where the motor drive current is not flowing.

FIG. 7 shows the photocoupler drive signal and the drive circuit signal when the output 39 of the fixed bias generation circuit 38 is applied when the feedback voltage 12 is zero volts. Motor 1 drive current is flowing. 43 is signal 39
The polarity of is reversed.

Details of the fixed bias generation circuit 38 (only a portion) are shown in FIG.

To explain FIG. 8, the output (±14■) of the square wave generation circuit is given to the inverting terminal 45 of the ○P amplifier 44, and the output of the OP amplifier 44 is set at the value set by the variable resistor 46. 39 is obtained. The output 39 is, for example, ±1V
~±6V is set.

On the other hand, a DC voltage proportional to the motor current is applied to the inverting terminal 48 of the OP amplifier 47. The DC voltage to the inverting terminal 48 is obtained from the output of the current detection circuit 8 shown in FIG. The value is about 3v.

The variable resistor 49 outputs the output 39 below the reference motor current.
This is for setting the reference motor current when applying a more fixed bias, and is set to about -0.5V to -1.5V.

Here, to show the actual value, for example, when the starting current is 15A, when 15A flows, the voltage at the inverting terminal 48 becomes -3V, so if the voltage of the variable resistor 49 is set to -1V,
When it exceeds 5A, the output of the OP amplifier 47 becomes H(14
V). If the output of the op amplifier 47 becomes H, the FE
When the T (N-channel junction type silicon field effect transistor) 50 is ON, the output of the OP amplifier 44 becomes zero volts.

In other words, a fixed bias was given below 6A, but
When the voltage exceeds 5A, the fixed bias from the output terminal 39 becomes zero port.

As described above, by applying a fixed bias to the input of the comparator circuit below a certain set reference motor current, a balanced motor current flows, the motor shaft is restrained, and the motor output The axis is
It is not affected by load fluctuations, and vibrations are significantly reduced.

As is clear from FIG. 7, the control order of the final stage output elements in FIG. 4 at the timing in FIG. 7 is 6c, 6
d-+6a, 6cm5ea, eb-sect.

6b = ac and ad again, and in this embodiment, the conventional motor drive method can absorb the motor training energy when the final stage output element is OFF, and the switching control method can be directly adopted, and the feedback voltage is zero, That is, even when the motor current is zero or the feedback voltage is small, that is, even when the motor current is small, a balanced motor current can be passed, so that vibrations can be extremely reduced.

The control order in the case of no feedback voltage in FIG. 6 is 6a, 6cm+6d, 6b-6a again.

6C, the motor drive current does not flow, and vibrations are likely to occur if there is a load change.

As a method for obtaining a fixed bias, as shown in FIG. 7, a rectangular wave generation voltage is applied to 46 in FIG. 8 using the signal in the reference wave generation circuit 5 of FIG. 1, and a fixed bias of the same frequency as the reference wave is generated. However, as mentioned above, the state of vibration generation differs depending on the form of the robot and each axis of each robot, so the frequency of the fixed bias and the bias as shown in Fig. All you have to do is make the size variable and set it. In addition, the reference motor current setting for giving a fixed bias is also shown in Figure 8-49.
It is sufficient to make it variable as shown in .

Effects of the Invention According to the present invention, there is no need to attach an expensive acceleration sensor or the like for detecting the magnitude of vibration to the arm of the robot machine body to reduce the vibration, and the vibration can be controlled reliably at low cost.

Further, the final stage output element may be two power transistors or a thyristor. Furthermore, it is extremely useful because it can be applied to a servo amplifier for an AC servo motor.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a motor control device showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a comparator circuit of the same device,
Figure 3 is a circuit diagram of the drive circuit of the same device, Figure 4 is a circuit diagram of the PWM power circuit and DC power supply circuit of the same device, Figures 5 to 7 are signal waveform diagrams of the main parts of the device, FIG. 8 is a circuit diagram of the main part of the fixed bias generation circuit of the same device. 2... Speed control circuit, 3... Current control circuit, 4... Comparator circuit, 5... Reference voltage generation circuit, 6... Drive circuit, 7 ...,
PWM power circuit, 8...Current detection circuit, 9...
Motor, 38--Fixed bias generation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 8 Figure 3?

Claims (1)

[Claims] In a motor control device that controls a motor using a control element such as a transistor or a thyristor, a drive circuit for the control element, a forward rotation to the drive circuit,
In addition to the comparator circuit that outputs a reverse rotation signal and the input determined by the reference wave, speed feedback, and current feedback, the input of the comparator circuit outputs a forward rotation below a certain reference motor current that is separately provided.
A motor control device equipped with a fixed bias generation circuit that provides a fixed bias equivalent to reverse rotation.