JPS62125412A - Speed control method for motor - Google Patents

Abstract

PURPOSE:To prevent an impact or vibrations produced by a machine system by performing the control so that a motor has a smooth speed change. CONSTITUTION:The data obtained by fractionating a smooth curve like a since curve is recorded to a memory 4 in order to a smooth speed change of a DC servo motor 12. This data is successively read out according to the address shown by an address counter 5 and converted into the analog data by a D/A converter 8. This analog data undergoes the conversion of frequency through a V/F converter and is supplied to a driver circuit 11 in the form of a command pulse train having a prescribed frequency. The circuit 11 gives the PLL control to the motor 12 by the command pulse train and a feedback pulse train. Thus the motor 12 is revolved while undergoing the speed control with the data obtained based on a smooth curve (sine curve). As a result, the motor 12 has no sudden change of acceleration.

Description

[Detailed description of the invention] Sanuni n! TECHNICAL FIELD The present invention relates to a method for controlling the speed of a motor, and more particularly to a method for controlling the rotational speed of a servo motor used in a servo mechanism of an industrial robot, a machine tool, or the like.

Conventionally, in the servo mechanisms of industrial robots and machine tools, servo motors, cutting motors, etc. are generally used as the drive source for moving and positioning workpieces between predetermined positions. .

For example, in digital speed control of a DC servo motor, a command pulse train generated by a pulse generation circuit is D-A converted, the motor is rotated by a rotation angle set according to the command pulse train, and at this time, a feedback pulse train is generated by an encoder. Based on the deviation 1 between the command pulse train and the command pulse train, the DC
The servo motor is made to rotate at an appropriate angle. In the conventional method for speed control of the DC servo motor mentioned above,
As shown in Fig. 4, the time-speed characteristic of the DC servo motor has a substantially trapezoidal speed pattern consisting of a linear acceleration section (A), a constant speed running section (B), and a linear deceleration section (C). A DC servo motor is driven to rotate according to a speed pattern, and the workpiece is positioned at a target position by stopping at a certain point.

In addition, for positioning control of DC servo motors, there is a stagnation control method and I) L L (PHASE LOCKED).
In the former accumulation control method, the DC servo motor starts rotating when the deviation Mm of the number of pulses between the command pulse train and the feedback pulse train has been accumulated by a predetermined amount, as shown by the broken line in Figure 4. and follow,
It decelerates and stops even near the target point assuming a certain delay.

On the other hand, in the latter PLL control method, the command pulse train (α)
In this method, the DC servo motor starts rotating at the same time as the command pulse train (α) is input, as shown by the solid line in Figure 4, and the feedback pulse train (β) is controlled in phase. It follows the target without any delay and stops at the target point.

■Bill j, glossy 1yunζ1i! By the way, in the speed control of the DC servo motor using the conventional method described above, the speed characteristic (A) becomes approximately trapezoidal as shown in FIG. 4, and the maximum speed in the constant speed traveling section (B) cannot be controlled. However, the slowdown characteristics in the linear acceleration section (A) and the linear deceleration section (C) cannot be controlled at will. When the speed of the DC servo motor is controlled according to the speed characteristic (a) shown in FIG. 4 in this way, the time-acceleration characteristic becomes as shown in FIG. As is clear from this acceleration characteristic (b), D
C servo motor rotation start point (a), linear acceleration section (
From A) to constant speed traveling section (B) - Time of transition (b),
The acceleration changes rapidly at the time (C) when the constant speed running section (B) shifts to the linear deceleration section (C) and at the time when the rotation stops (d). Therefore, when the DC servo motor is driven to rotate at high speed, there is a problem in that shocks and vibrations are generated in the mechanical system.

For divination.

The present invention has been proposed in view of the above problem, and a technical means for solving this problem is to control the rotational speed of the workpiece positioning motor so that the speed characteristic of the motor is a smooth curve. This is a motor speed control method in which a command pulse train is generated based on data set so that the motor is rotated by the command pulse train.

According to the method of the present invention, the command pulse train is generated based on data set so that the speed characteristic of the motor becomes a smooth curve. Since the speed of the motor can be controlled, the above problems can be easily solved.

An example of an apparatus in which the motor speed control method according to the present invention is applied to a PLL control system DC sanipo motor will be described with reference to FIG. FIG. 1 shows a circuit configuration block diagram of a speed control device.1. In the figure, (1) is the CPU (central processing circuit), (2) is the CPU (1)
The selector circuit (3) controls data transfer between the CP tJ (
1) and a buffer circuit that temporarily stores the data transferred between the peripheral device and the circuit described later, and (4) is a buffer circuit in which data set so that the speed characteristics of the motor become a smooth curve is written. The data in this memory (4) is, for example, the speed characteristic subdivided by time, and the speed per unit time is divided into 16 bits.

is replaced with the original digital value. (5) is an address counter that specifies the address of the data written in the memory (4), and is counted up or down by the clock pulse oscillator (6). (
7) is a latch circuit that latches the data sent from the memory (4), and (8) is a D/D converter that converts the data sent from the memory (4) through the launch circuit (7) to a predetermined voltage value to analog. A converter (9) is a V/T' converter that converts the voltage value converted into analog by the D/A converter (8) into a frequency, and (10) is a converter based on the control signal from the selector circuit (2). A rotation direction switching circuit (11) is a driver circuit for driving the DC servo motor (12), and the rotation direction switching circuit (11) is a driver circuit for driving the DC servo motor (12). Based on the signal l)c-po motor (
12) is rotated by a PLL control method. (13) is a rotation direction determination circuit that determines the rotation direction of the DC servo motor (12) based on a feedback pulse train sent from an encoder (14) connected to the DC servo motor (12); (15) is a rotation direction determination circuit for determining the rotation direction of the DC servo motor (12); Motor (12)
A coordinate management absolute counter that manages the rotation angle coordinate of the DC servo motor (12) counts and amplifies the rotation angle coordinate to a positive value according to the output signal sent from the rotation direction determination circuit (13) if the DC servo motor (12) rotates normally. Also, the above D
If the C servo motor (12) is in reverse rotation, the rotation angle coordinate is counted down to a negative value.

In the speed control of the DC servo motor (12) according to the method of the present invention, as shown in FIG. The data obtained by time-dividing this speed characteristic (c) as described above is read out sequentially for each address specified by the address counter (5). This read data is converted into analog by a D/A converter (8), and then frequency converted by a V/F converter (9). The generated command pulse train (α') having the desired frequency is input to the driver circuit (11), and this command pulse train (α') and the feedback pulse train (β') of the encoder (14) are synchronized in phase. Based on the command pulse train (α'), the DC servo motor (12) is rotationally driven while being speed controlled according to the speed characteristic (c) in FIG. 2 described above. At this time, since the rotational acceleration characteristic (d) of the DC servo motor (12) is set in a substantially sine curve shape as shown in FIG. 3, the acceleration does not change suddenly.

In the above embodiment, the speed control of a PLL control type DC servo motor was explained, but the method of the present invention is not limited to this, and can be applied to speed control of a pool control type DC servo motor or a stainless pig motor. Of course, it is also applicable. However, in the DC servo motor using the pool control method, the command pulse train and the feedback pulse train are not synchronized. Therefore, in the method of the present invention, the DC servo motor using the PLL control method, in which the command pulse train and the feedback pulse train are phase-synchronized, is preferable. It is.

According to the method of the present invention, the motor is rotationally driven while controlling its speed using a command pulse train based on data set so that the speed characteristic of the motor becomes a smooth curve. This makes it possible to prevent shocks and vibrations that occur during operation, making it easier to achieve highly accurate and stable positioning.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an example of an apparatus for implementing the motor speed control method according to the present invention, FIG. 2 is a characteristic diagram showing the time-speed relationship in the method of the present invention, and FIG. 3 is a diagram showing the method of the present invention. It is a characteristic diagram which shows the time-acceleration relationship in . FIG. 4 is a characteristic diagram showing the time-speed relationship in the conventional method.
FIG. 5 is a characteristic diagram showing the time-acceleration relationship in the conventional method. (12) --- Work positioning motor (DC servo motor), (c) --- Speed characteristics, (α') -- Command pulse train. Hanike Akata Meng's Kakyou no E Takesumi Diagram 4 - t7z method 1 Hungry Country Figure 5

Claims (1)

[Claims] (1) When controlling the rotational speed of the workpiece positioning motor, a command pulse train is generated based on data set so that the speed characteristic of the motor becomes a smooth curve, and the motor is rotationally driven by this command pulse train. A motor speed control method characterized by: