JPH04247503A - Controller - Google Patents

Abstract

PURPOSE:To present the controller which can switch the moving amount of an object to be controlled per one command pulse over a wide range, move the object to be controlled little by little and prevent a servo system from being instable even when the multiplicaiton factor of a position signal feedback loop is changed. CONSTITUTION:The controller is provided with a first pulse multiplier making the command pulse G1-fold, an encoder 6 detecting the position of the object to be controlled, a second pulse multiplier 7 making the detection pulse of the encoder 6 G2-fold, a deviation counter 2 detecting deviation between pulses multiplied by the first and second pulse multipliers 1 and 7 each other, and a divider 3 making the output of the deviation counter 2 1/G2-fold. Corresponding to the output of the divider 3, a driving source 5 is driven.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device, and more particularly to a control device for controlling the position of a controlled object in accordance with the amount of command pulses.

0002

2. Description of the Related Art A control device is known as a pulse train input servo device that controls the position of a controlled object in accordance with the amount of input command pulses. FIG. 4 shows a conventional example of such a control device. In FIG. 4, a servo motor 15 serving as a drive source drives a controlled object 19 via a pinion 18 that is rotationally driven by its rotation shaft. The servo motor 15 has an encoder 16 that detects its rotational position, and by counting detection pulses of the encoder 16, the position of the controlled object 19 can be detected.

The servo motor 15 is driven according to an input command pulse, and the command pulse is once multiplied by G1 by a pulse multiplier 11. On the other hand, the detected pulse of the encoder 16 is multiplied by G2 by a pulse multiplier 17. The command pulse multiplied by G1 and the output of the encoder 16 multiplied by G2 are input to the deviation counter 12, and the deviation of both is detected. Deviation counter 12
The servo motor 15 is driven via the servo amplifier 14 according to the deviation signal detected by the servo amplifier 14 . When the deviation becomes zero, the driving of the motor 15 is stopped and the controlled object 19 is positioned at the target position.

0004

[Problem to be solved by the invention] According to the above conventional example,
By appropriately setting the ratio of the magnifications G1 and G2 by the two pulse multipliers 11 and 17, the amount of rotation of the motor 15 per one command pulse can be changed and the amount of movement of the controlled body 19 can be changed.

Two pulse multipliers 1 in the above conventional example
Reference numerals 1 and 17 are a combination of digital circuits and the like, and the pulses are multiplied by a hardware configuration. For example, regarding the pulse multiplier 17, since the encoder 16 outputs A-phase and B-phase pulses whose phases are different by 90 degrees as shown in FIG.
Alternatively, the encoder output pulses can be configured to be multiplied by 1, 2, or 4 times by generating pulses at the rise and fall of one-phase pulses, or even at the rise and fall of two-phase pulses. ing.

As mentioned above, the pulse multiplier in the conventional control device multiplies the pulses by the hardware configuration, so the multiplication rate can only be selected from 1x, 2x, and 4x. , the amount of movement of the controlled object per command pulse cannot be changed over a wide range. Furthermore, if the value of G2 is decreased, the detection position accuracy, that is, the resolution of the encoder will deteriorate, and if the value of G2 is changed, the position loop gain will change, causing resonance, and the servo system will become unstable. Furthermore, in order to move the controlled object minute by minute, the ratio of G1 and G2 must be set to 1, for example.
It may be set to a numerical value such as 000/999, but since the multiplier of the multiplier in conventional control devices is limited to 1, 2, and 4 times, the controlled object can be set to a minute amount. It cannot be moved one by one.

The present invention has been made to solve the problems of the prior art, and makes it possible to switch the amount of movement of a controlled object per one command pulse over a wide range, and to It is an object of the present invention to provide a control device that can move the servo system by minute amounts, and can also prevent the servo system from becoming unstable even if the multiplication factor of the position signal feedback loop is changed.

[0008]

[Means for Solving the Problems] The present invention includes a first pulse multiplier that multiplies a command pulse by G1, an encoder that detects the position of a controlled object, and a second pulse multiplier that multiplies a detection pulse of the encoder by G2. a multiplier, a first pulse multiplier and a second pulse multiplier;
It has a deviation counter that detects the deviation between the multiplied pulses by the pulse multiplier, and a divider that converts the output of the deviation counter to 1/G2, and drives the drive source according to the output of the divider. It is characterized by

[0009]

[Operation] The deviation between the command pulse multiplied by G1 by the first pulse multiplier and the encoder detection pulse multiplied by G2 by the second pulse multiplier is detected by the deviation counter, and the output pulse of the deviation counter is detected by the divider. The driving source is driven according to the output of this divider, and the position of the controlled object is controlled. By arbitrarily setting the ratio of G1 and G2,
The amount of movement of the controlled object per command pulse can be varied over a wide range from a very small amount to a large amount. Since G2 of the feedback system is reduced to 1/G2 by a divider, it is ignored, and even if G2 is greatly varied, the servo system will not become unstable.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device according to the present invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, a servo motor 5 serving as a drive source drives a controlled body 9 via a pinion 8 that is rotationally driven by its rotation shaft. The servo motor 5 has an encoder 6 that detects its rotational position.
The position of the controlled object 9 can be detected by counting the detection pulses.

The servo motor 5 is driven according to the input command pulse, and the command pulse is once multiplied by G1 by the pulse multiplier 1. The detected pulse of the encoder 6 is multiplied by G2 by a pulse multiplier 7. G
The command pulse multiplied by 1 and the output of the encoder 6 multiplied by G2 are input to the deviation counter 2, and the deviation of both is detected.

The configuration up to this point is substantially the same as the conventional example. However, as a component clearly different from the conventional example, a divider 3 is provided after the deviation counter 2, and the deviation signal detected by the deviation counter 2 is divided into 1/G2. be. A servo motor 5 is driven via a servo amplifier 4 in accordance with the deviation signal converted to 1/G2 by a divider 3. Command pulse multiplied by G1 and G2
When the deviation from the multiplied detection pulse by the encoder 6 becomes zero, the driving of the motor 5 is stopped and the controlled object 9 is positioned at the target position.

The pulse multiplier 1, the pulse multiplier 7 and the divider 3 can be composed of a microcomputer,
G1 and G by microcomputer software
The value of 2 can be set freely and precisely.

The operation of the above embodiment will be explained with reference to FIG. G1, G2 of pulse multipliers 1, 7 and divider 3
Set the value arbitrarily from outside the servo loop. Now, when a command pulse is input, the command pulse amount is changed to pulse multiplier 1.
is multiplied by G1 and stored in register R1. Further, the position feedback pulse amount from the encoder 6 is multiplied by G2 by the pulse multiplier 7 and stored in the register R2. The difference R3 between the value of register R1 and the value of register R2 is calculated by the deviation counter 2, and the sum of the value calculated previously and stored in register R3 and the value of R3 calculated this time is calculated and this is used as the deviation value. It is stored in register R3 as . Deviation value R3
is divided into 1/G2 by the divider 3, and this value is stored in the register R4. The value of register R4 is output to servo amplifier 4, and servo motor 5 is driven according to the value of register R4. The above operations are repeated, and finally the driven body 9 is controlled to a position corresponding to the command pulse.

By the way, if the driven object is a moving table or the like, even if the basic design is to move 10 mm per 10,000 pulses, in reality it will move slightly from the target movement position due to the mechanical processing precision of the pinion and rack. It may shift. In order to correct this deviation, the command pulse rate or position feedback pulse rate may be changed. According to the conventional example, the pulse rate can only be changed to a very limited value such as 1, 2, or 4 times and within a narrow range, so it is difficult to make fine adjustments to the driven body. Another drawback is that the loop gain fluctuates due to changes in the position feedback pulse rate, making the servo system unstable.

In this regard, according to the above embodiment, the ratio G1/G2 of the multiplication rate of the command pulse and the feedback pulse is set to a very small ratio, for example 999/1000, so that the amount of movement per pulse is made very small. By doing so,
The position of the driven body can be finely adjusted. Further, the ratio G1/G2 of the above multiplication rate is set to 100/1 or 1/10, for example.
It is also possible to increase the amount of movement per pulse by setting a large ratio such as 0. In short, the pulse rate for controlling the position of the driven body can be changed over a wide range from a very small value to a large value.

Furthermore, since the feedback pulse is multiplied by G2 to calculate the deviation from the command pulse as described above, the resolution of the encoder 6 is not reduced. Furthermore, even if the feedback pulse is multiplied by G2, the output of the deviation counter 2 is made 1/G2 by the divider 3, so the servo system remains stable even if the value of G2 is set arbitrarily. The reason why the servo system is stable even if the value of G2 is set arbitrarily will be explained below.

FIG. 3 shows a model of the embodiment shown in FIG. In Figure 3, X(s) is the command position, Y(
s) indicates the output position, and Kp indicates the position loop gain. The servo amplifier has a sufficient frequency band compared to the deviation counter, and is represented by a block with a gain of x1. When the transfer function P(s) of this position control loop is calculated,

[Math 1] becomes. Rearranging this formula, we get

[Math. 2] The stability of the servo system is determined using the denominator of Equation 2, but by inserting 1/G2, G2 disappears from the denominator of Equation 2. This means that G2 is ignored, and even if the value of G2 is greatly changed, the position control servo system remains stable.

[0019]

Effects of the Invention According to the present invention, the ratio of the multiplication rate between the command pulse and the feedback pulse from the encoder G1/G2
can be arbitrarily set from a very small value to a large value, and thereby the pulse rate for controlling the position of the driven body can be changed over a wide range from a very small value to a large value. Furthermore, since the feedback pulse is multiplied by G2 to calculate the deviation from the command pulse, the resolution of the encoder is not reduced. Furthermore, even if the feedback pulse is multiplied by G2, the output of the deviation counter is made 1/G2 by the divider, so G
Even if the value of 2 is arbitrarily set, the servo system remains stable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a control device according to the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment.

FIG. 3 is a block diagram showing a model of the above embodiment.

FIG. 4 is a block diagram showing an example of a conventional control device.

FIG. 5 is a timing chart showing the multiplication operation of the pulse multiplier in the conventional example.

[Explanation of symbols]

1 First pulse multiplier 2 Deviation counter 3 Divider 5 Motor as a driving source 6 Encoder 7 Second multiplier 9 Driven body

Claims (1)

[Claims] 1. A first pulse multiplier that multiplies a command pulse by G1, an encoder that detects the position of a controlled object, a second pulse multiplier that multiplies a detection pulse of the encoder by G2, and a first pulse multiplier that multiplies a command pulse by G1. It has a deviation counter that detects the deviation between the multiplied pulses by the multiplier and the second pulse multiplier, and a divider that converts the output of the deviation counter to 1/G2,
A control device that drives a drive source according to the output of the divider.