JP2555226B2 - Control device - Google Patents

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 according to the amount of command pulses.

[0002]

2. Description of the Related Art As a pulse train input servo device, a control device for controlling the position of a controlled object according to the amount of an input command pulse is known. FIG. 4 shows a conventional example of such a control device. In FIG. 4, a servo motor 15 as a drive source drives a controlled body 19 via a pinion 18 which is rotationally driven by its rotation shaft. The servo motor 15 has an encoder 16 for detecting its rotational position, and the position of the controlled object 19 can be detected by counting the detection pulses of the encoder 16.

The servomotor 15 is driven according to an input command pulse, and the command pulse is once multiplied by G ₁ times by the pulse multiplier 11. On the other hand, the pulse detected by the encoder 16 is multiplied by G _{2 in the} pulse multiplier 17. The command pulse multiplied by G ₁ times and the output of the encoder 16 multiplied by G ₂ times are input to the deviation counter 12 and both deviations are detected. The servo motor 15 is driven via the servo amplifier 14 according to the deviation signal detected by the deviation counter 12. When the deviation becomes zero, the driving of the motor 15 is stopped and the controlled body 19 is positioned at the target position.

[0004]

According to the above conventional example,
By appropriately setting the ratio of the magnifications G ₁ and G ₂ by the two pulse multipliers 11 and 17, it is possible to change the amount of rotation of the motor 15 per command pulse and change the amount of movement of the controlled body 19. .

Two pulse multipliers 1 in the above conventional example
Reference numerals 1 and 17 are combinations of digital circuits and the like, and have a hardware configuration for multiplying pulses. For example, regarding the pulse multiplier 17, the encoder 16
As shown in FIG. 5, since the A-phase and B-phase pulses whose phases are different by 90 ° are output, only one-phase pulse rises or one-phase pulse rises and falls, and further two-phase The encoder output pulse is configured to be multiplied by 1, 2, or 4 by generating pulses at the rising and falling edges of the pulse.

As described above, since the pulse multiplier in the conventional control device is adapted to multiply the pulse by the hardware configuration, the multiplication ratio can be selected from only 1, 2, and 4. The amount of movement of the controlled object per pulse of the command pulse cannot be switched in a wide range. Further, when the value of G ₂ is reduced, the detection position accuracy, that is, the resolution of the encoder is deteriorated, and when the value of G ₂ is changed, the position loop gain is changed to cause resonance and the servo system becomes unstable. is there. Further, in order to move the controlled object by a small amount, the ratio of G ₁ and G ₂ is set to, for example, 10
It may be set to a numerical value such as 00/999, but since the multiplication factor of the multiplier in the conventional control device is a limited value such as 1 time, 2 times, and 4 times, it is possible to reduce the amount of the controlled object by a very small amount. You cannot move them one by one.

The present invention has been made in order to solve the problems of the prior art, and makes it possible to switch the movement amount of the controlled object per one command pulse in a wide range and to control the controlled object. It is an object of the present invention to provide a control device capable of moving the motor by a small amount and preventing the servo system from becoming unstable even when the multiplication rate of the position signal feedback loop is changed.

[0008]

According to the present invention, there is provided a first pulse multiplier for multiplying a command pulse by G ₁ ; an encoder for detecting the position of a controlled object; and a _second pulse for multiplying an encoder detection pulse by G ₂ . Pulse multiplier, a first pulse multiplier and a second pulse multiplier
It has a deviation counter for detecting the deviation between the multiplied pulses by the pulse multiplier and the divider for making the output of the deviation counter 1 / G ₂ and drives the drive source according to the output of the divider. It is characterized by doing.

[0009]

The deviation between the command pulse multiplied by G ₁ by the first pulse multiplier and the detection pulse of the encoder multiplied by G ₂ by the second pulse multiplier is detected by the deviation counter, and the output pulse of the deviation counter is divided. It is reduced to 1 / G ₂ by a calculator, the drive source is driven according to the output of the divider, and the position of the controlled object is controlled. By arbitrarily setting the ratio of G ₁ and G ₂ , the movement amount of the controlled object per one command pulse can be changed in a wide range from a very small amount to a large amount. G ₂ of the feedback system is ignored by being made 1 / G ₂ by the divider, and the servo system will not become unstable even if G ₂ is largely changed.

[0010]

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

The servomotor 5 is driven in response to an input command pulse, but the command pulse is once multiplied by G ₁ times by the pulse multiplier 1. The pulse detected by the encoder 6 is multiplied by G _{2 in the} pulse multiplier 7. G ₁
The output of the encoder 6, which is multiplied _twice the multiplied command pulses and G doubling is input to the deviation counter 2, both deviations are detected.

The structure up to this point is substantially the same as that of the conventional example. However, as a component that is clearly different from the above-mentioned conventional example, a divider 3 is provided after the deviation counter 2 so that the deviation signal detected by the deviation counter 2 becomes 1 / G ₂ . Is. 1 / G ₂ with divider 3
The servo motor 5 is driven via the servo amplifier 4 in accordance with the deviation signal that has been set. Command pulse multiplied by G ₁ and G ₂
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 body 9 is positioned at the target position.

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

The operation of the above embodiment will be described with reference to FIG. The values of G ₁ and G ₂ of the pulse multipliers 1 and 7 and the divider 3 are arbitrarily set from outside the servo loop. Now, when the command pulse is input, the command pulse amount is multiplied by G ₁ by the pulse multiplier ₁ and stored in the register R ₁ . The position feedback pulse amount by the encoder 6 is multiplied by G ₂ by the pulse multiplier 7 and stored in the register R ₂ . Register R
The difference R ₃ between the value of _{1 and} the value of register R ₂ is calculated by the deviation counter 2, and the sum of the value previously calculated and stored in register R ₃ and the value of R ₃ calculated this time is calculated. Is stored in the register R ₃ as a deviation value. The deviation value R ₃ is the divider 3
To 1 / G ₂ and this value is stored in the register R ₄ .
The value of the register R ₄ is output to the servo amplifier 4, and the servo motor 5 is driven according to the value of the register R ₄ . The above operation is repeated, and finally the driven body 9 is controlled to the position corresponding to the command pulse.

By the way, when the driven body is a moving table or the like, even if the basic design is such that it moves 10 mm per 10,000 pulses, in reality, it is slightly moved from the target moving position due to the mechanical processing accuracy of the pinion and rack. It may shift to In order to correct this deviation, the command pulse rate or the position feedback pulse rate may be changed. According to the conventional example, the pulse rate is 1 time, 2
It is difficult to finely adjust the driven body because it can be changed only in a narrow range such as double, quadruple, and the loop gain fluctuates by changing the position feedback pulse rate. However, there is a problem that the servo system becomes unstable.

On the other hand, according to the above-described embodiment, the ratio G ₁ / G ₂ of the multiplication ratios of the command pulse and the feedback pulse is set to a very small ratio of 999/1000, for example, 1
The position of the driven body can be finely adjusted by making the amount of movement per pulse extremely small. It is also possible to increase the amount of movement per pulse by setting the ratio of multiplication rates G ₁ / G ₂ to a large ratio such as 100/1 or 1/100. In short, the pulse rate for controlling the position of the driven body can be changed in a wide range from a very small value to a large value.

Since the feedback pulse is multiplied by G ₂ and the deviation from the command pulse is calculated as described above, the resolution of the encoder 6 is not lowered. Further, even if the feedback pulse is multiplied by G ₂ , the output of the deviation counter 2 is set to 1 / G ₂ by the divider 3, so that the servo system is stable even if the value of G ₂ is arbitrarily set. ing. The reason why the servo system is stable even if the value of G ₂ is set arbitrarily will be described below.

FIG. 3 shows a model of the embodiment shown in FIG. In FIG. 3, X (s) is the command position and Y (s) is
(S) indicates the output position, and Kp indicates the position loop gain. The servo amplifier has obtained a sufficient frequency band as compared with 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,

[Equation 1] Becomes Organizing this formula,

[Equation 2] Becomes Judgment of the stability of the servo system is made by the denominator of the equation ₂ , but by adding 1 / G ₂ , the denominator of the equation ₂ disappears G ₂ . This means that G ₂ is ignored, and the position control servo system is stable even if the value of G ₂ is greatly changed.

[0019]

According to the present invention, the ratio G ₁ / G ₂ of the multiplication factor of the command pulse and the feedback pulse from the encoder can be set arbitrarily from a very small value to a large value. The pulse rate for controlling the position of the driven body can be changed in a wide range from a very small value to a large value. Further, since the feedback pulse is multiplied by G ₂ and the deviation from the command pulse is calculated, the resolution of the encoder is not lowered. Moreover, since the by multiplying the feedback pulse _doubling G, and the output of the deviation counter 1 / G ₂ in divider, G ₂
The servo system is stable even if the value of is set arbitrarily.

[Brief description of drawings]

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 above embodiment.

FIG. 3 is a block diagram showing a modeled embodiment 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 Driving Source 6 Encoder 7 Second Multiplier 9 Driven Object

Claims (1)

(57) [Claims] _1. A first pulse multiplier for multiplying a command pulse by G ₁ ; an encoder for detecting a position of a controlled object; a second pulse multiplier for multiplying an encoder detection pulse by G _2; A pulse counter for detecting a deviation between the multiplied pulses by the pulse multiplier and the second pulse multiplier, and a divider for making the output of the deviation counter 1 / G ₂ .
A control device driving a drive source according to an output of the divider.