JPS6295983A - Controller for motor - Google Patents

Abstract

PURPOSE:To reduce vibrations generated in the machine body of a robot by previously applying a fixed bias to an input to a comparator circuit outputting forward rotation and reverse rotation signals to a drive circuit. CONSTITUTION:When a command voltage Ei is applied to an input terminal 1, the signals of the forward and reverse rotation of a motor are acquired through a speed control circuit 2, a current control circuit 3 and a comparator circuit 4. The signals are transmitted over a control element such as a power transistor through a drive circuit 6 and a PWM power circuit 7. An output from a reference-voltage generating circuit 5 and an output from a fixed-bias generating circuit 38 are sent to the comparator circuit 4. When a fixed bias is transmitted at all times, the motor is supplied with prescribed forward- rotation and reverse-rotation motor currents continuously even when motor load is small and motor currents are small, thus generating torque in the motor, then reducing vibrations.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a final stage output element of a servo motor control device (hereinafter referred to as a servo amplifier) capable of controlling rotation using a final stage output element consisting of a transistor or a thyristor. The present invention relates to a device for controlling signals to a drive 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 (4
When the speed is low (about 0 crn/min to 80 crn/min), the motor current is small, and in this case, vibrations 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.

In addition, at high speeds, the motor current is small even 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. As the gain was increased, the vibration tended to decrease, but this could sometimes be a problem in practical use.On the other hand, when the gain was increased, the vibration tended to increase even when the robot was in any position 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 In the present invention, a separately provided fixed bias equivalent to forward rotation and reverse rotation is always applied to the input of a comparator circuit that outputs forward rotation and reverse rotation signals to the drive circuit. A fixed bias generation circuit is provided.

By always applying a fixed bias, even when the motor load is small and the motor current is small, constant forward and reverse rotation motor currents are always supplied to the motor and torque is generated in the motor. This makes vibrations extremely small.

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 at all times to generate torque. By flowing a balanced motor current, the motor shaft is restrained at a certain value while rotating, and is less affected by load fluctuations on the motor output shaft, and does not fluctuate against instantaneous load fluctuations. Without it, the 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 command voltage Ei is applied to speed control circuit 2. Current control circuit 3. Signals such as motor forward/reverse signals are obtained through the comparator circuit 4, and are amplified by the drive circuit 6.
A signal is applied to the WM power circuit 7, which controls switching of a control element such as a power transistor, which is a final output element.

When a control element such as a power transistor is controlled by switching, the servo motor e rotates in forward and reverse directions, and TGlo generates a voltage proportional to the number of forward and reverse rotations, and the speed control circuit 2
will be given feedback.

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 5 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 comparator circuit 4 will be explained with reference to FIG. Further, the drive circuit 6 will be explained with reference to FIG. Furthermore, details of the PWM power circuit 7 and the DC power supply circuit 11 will be explained with reference to FIG.

In FIG. 2, the outputs of comparators 14 and 15 (7) are applied to transistors 16 to 19, and photocoupler 20
~23 primary side is controlled. The resistors 40.degree. and 41 are provided to provide the output of the fixed bias generation circuit 38 to the comparators 14 and 15.

Next, referring to FIG. 3, FIG. 3 shows a drive circuit for only one element of the power transistor 7. Reference numeral 24 is a secondary side light receiving element of a photocube 720, and the output of this light receiving element 24 is , the transistor 26 turns on,
When transistor 26 turns on, transistor 27 turns on
FF L, transistor 26 turns on and supplies base current to the power transistor.

Explaining FIG. 4, the circuit configurations of ab, ec, and ad 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 7-Lee wheeling diode.

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

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

Similarly, C is a photocoupler 22 and a drive circuit 6c, and d is a photocoupler 23 and a drive circuit ad.

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 at zero voltage, and when the feedback voltage 12 is at zero voltage. However, the motor drive current is flowing. 43 is the signal 39 with the polarity reversed.

By constantly applying a fixed bias to the input of the comparator circuit 4 as described above, a balanced motor current flows, and the motor shaft is restrained.
The motor output shaft is not affected by load fluctuations, and vibration is extremely small.

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, ad
-+6a, 6cm5ea, 6b-+6d.

6b = sc and ad again, and in this embodiment, the conventional motor and driving method can directly adopt the switching control method that can absorb the motor training energy when the final stage output element is OFF, and the feed bank voltage is zero volts. 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.

In addition, the control order when there is no feedback voltage in FIG. 6 is 6a, 6C, 46d, 6b - 6a, 8c again, and the motor drive current does not flow, and if there is a load fluctuation,
Prone to vibration.

As a method for obtaining a fixed bias, in FIG. 7, a configuration is used in which a signal in the reference wave generation circuit ε of FIG. 1 is used to provide a fixed bias of the same frequency as the reference wave, but as described above, Since the state of vibration generation differs depending on the form of the robot and each axis of each robot, the frequency and magnitude of the fixed bias may be made variable and set accordingly.

Effects of the Invention As described above, according to the present invention, vibration can be reduced with a simple configuration, and the magnitude of vibration can be detected in the arm of the robot machine body. There is no need to attach and control expensive acceleration sensors to reduce vibrations, and the control can be done inexpensively and reliably.

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,
FIG. 3 is a circuit diagram of the drive circuit of the same device, FIG. M4 is a circuit diagram of the PWM power circuit and DC power supply circuit of the same device, and FIGS. 6 to 7 are signal waveform diagrams of the main parts of the same device. 2... Speed control circuit, 3... Current control circuit, 4... Comparator circuit, 5...
Reference wave generation circuit, 6... Drive circuit, 7...
・PWM nozzle circuit, 8...Current detection circuit, 9
...Motor, 38...Fixed bias generation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person N
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ζsaζ αsa (sha 4 I! 2! 8; Goko Do U) Castle

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,
A comparator circuit that outputs a reverse rotation signal, and a fixed bias generation circuit that always applies a fixed bias equivalent to forward rotation and reverse rotation to the input of the comparator circuit, in addition to the input determined by the reference wave, speed feedback, and current feedback. A motor control device equipped with