JP2512727B2 - Servo controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a servo control device.

(Prior Art) For example, in a retrofit of a general-purpose machine tool, in a system that uses a general-purpose numerical control machine tool, since the machine has rattling, the position of the work table is adjusted using a digital length measuring device. Directly detect it as the actual position detection value,
Servo control is generally performed by a completely closed loop type servo control.

(Problems to be Solved by the Invention) However, in the case of such a conventional method, the load held by the machine is reduced from the viewpoint of the drive system motor, and the work is prevented even if the motor rotates. The dead zone where the table does not move. Therefore, when an external force is applied to the table and a positional deviation occurs, a command to correct the deviation is output from the numerical control device, the motor rotates in the direction to compensate, and the next position detection pulse is input. It will turn. However, since no electrical control is performed in this dead zone, a phenomenon occurs in which the motor rotates excessively, causing hunting and degrading the positioning accuracy.

The present invention has been made in view of such a conventional problem, and performs position control of a small displacement in a positioning region of a target position that exceeds the limit of digital control by switching to an analog control characteristic curve. Accordingly, it is an object of the present invention to provide a servo control device that can perform accurate positioning without hunting.

[Structure of the Invention] (Means for Solving the Problems) In view of the conventional problems as described above, the present invention detects the movement of the load moved by the servomotor to detect the sin wave (A phase) and the cos wave. Position detector that outputs a wave (B phase) signal, and a sin wave (A phase) and a cos wave (B phase) from the position detector
Phase) into a rectangular wave, and outputs it as a feedback pulse to the numerical control device side, and a waveform shaping circuit to give to the gate control circuit, and the sin wave and cos wave from the position detector are input together with the sin wave and cos wave. A waveform synthesizing circuit for synthesizing the inverted sin wave and the inverted cos wave to give to the waveform switching circuit, and rectangular waves of the rectangular waves A phase and B phase from the waveform shaping circuit are combined and a gate signal is created. And a waveform switching circuit for switching which of the synthesized waves from the waveform synthesizing circuit is to be output by a gate signal from the gate control circuit, and the waveform switching circuit. The analog signal is input as a servo command value and the command value from the D / A converter on the numerical controller side is input as a servo command value, and the gate control signal from the gate control circuit is input. By the operation of the analog switch, the input switching circuit that selects the command value voltage from the waveform switching circuit or the command value voltage of the D / A converter and gives it to the servo amplifier, and the command value voltage of the D / A converter are input. , When this command value voltage enters the range of 1 LSB of the reference voltage value, it is judged that the load has reached the positioning region and a comparator circuit that gives an output to the gate control circuit, and a signal from this comparator circuit And the gate control circuit that outputs the gate control signal to the analog switch of the input switching circuit.

(Embodiment) Conceptually showing a servo control device according to this embodiment,
As shown in FIG. 1, a motor 5 for driving a load 3 having a position detecting means 1
A servo amplifier 7 for applying a predetermined driving force to the motor 5, a command value calculating means 9 for comparing a position detected by the position detecting means 1 with a target position and outputting a new servo command value, In a minute positioning area before and after the target position of the load, a positioning area command value creating means 11 that outputs a servo command value that changes in an analog manner with the target position being 0, and whether the load is in the positioning area with respect to the target position Control means 13 for determining whether or not, when the load is determined to be in the positioning region by this means,
The control characteristic switching means 15 is provided for supplying the servo command value from the positioning area command value creating means 11 to the servo amplifier 7 in place of the servo command value from the command value computing means 9.

FIG. 2 shows a detailed block diagram of an embodiment of the present invention. Further, FIG. 3 and subsequent figures show signal waveforms of respective parts of the servo control device shown in this block diagram.

The position detector 21 as a position detecting means is installed on a work table (not shown) as a load, and the movement of the table is determined by a sine wave and a cosine wave as shown in FIG. 3 (a). Output as a wave signal.

The positioning area command value creating means is a waveform shaping circuit 23, a waveform synthesizing circuit 25, a waveform switching circuit 27, and a gate control circuit 29.
It consists of

The waveform shaping circuit 23 uses the sine wave (A
Phase) and the cos wave (B phase) are shaped into rectangular waves as shown in FIGS. 3 (b) and 3 (c) and output as feedback pulses to the numerical controller 31 side.

Further, the sin wave and the cos wave from the position detector 21 are input to the waveform synthesizing circuit 25, where sin wave
The inversion sin wave and the inversion con wave are combined together with the wave and the cos wave, and they are given to the waveform switching circuit 27.

The waveform switching circuit 27 has the configuration shown in FIG. 5, and switches which of the synthesized waves from the waveform synthesizing circuit 25 is output by a gate signal from the gate control circuit 29.

As shown in FIG. 6, the gate control circuit 29 synthesizes rectangular waves of phases and phases from the rectangular waves A phase and B phase from the waveform shaping circuit 23, and further, FIG. 3 (g) to (j). And, the gate signals MODE1 to MODE4 as shown in FIGS. 7A to 7D are created, and the analog switches SW1a to SW1d of the waveform switching circuit 27 are generated.
Give to.

Therefore, in the waveform switching circuit 27, as shown in FIG.
As shown in (f), analog switches SW1a to SW1d and SW
Analog switches SW1a to SW1d on the signal line synchronized with 2 and conducting by this analog switch SW2
The sine wave that passes through is output sequentially.

The input switching circuit 33 as the control characteristic switching means is also provided with the analog switch SW3, and the analog signal is input to the input terminal from the waveform switching circuit 27 as the servo command value. The analog switch SW3 is turned on / off by a gate signal from a gate control circuit 35 described later.

A command value voltage from the D / A converter 37 on the side of the numerical control device 31 as command value calculating means is given to the input switching circuit 33 as a servo command value. This command value voltage follows the characteristics shown in FIG.

Further, the command value voltage of the D / A converter 37 is input to a comparator circuit 39 as a control means, and is compared there with a reference voltage value ref. Here, the reference voltage value ref is the ninth
As shown in the figure, the command value voltage of the D / A converter 37 is set to a voltage value that makes it 1 LSB, and the range (−ref to r
When the command value voltage is input to (ef), the comparator circuit 39 determines that the work table has reached the positioning area. Therefore, an output is given to the gate control circuit 35, and the gate control circuit 35 gives a gate control signal to the analog switch SW3 of the input switching circuit 33.

The input switching circuit 33 selects either the command value voltage from the waveform switching circuit 27 or the command value voltage of the D / A converter 37 by the operation of the analog switch SW3, and supplies it to the servo amplifier 41.

 The operation of the servo controller having the above structure will be described below.

Normally, the command value voltage from the D / A converter 37 is given to the servo amplifier 41 via the input switching circuit 33, and the servo amplifier 41 changes the rotation speed of the servomotor (not shown) to the eighth value by this command value voltage. Determined according to the characteristics shown in the figure, and give a predetermined rotation to the servo motor.

The rotation of the servo motor moves the table, and the position displacement is detected by the position detector 21.

The detection signals of the position detector 21 are sin waves and cos waves shown in FIGS. 3 (a) and 4 and the analog signals are input to the waveform shaping circuit 23.

The waveform shaping circuit 23 shapes the waveform of the sine wave and the cos wave, and outputs the rectangular wave signal shown in FIGS. 3B and 3C to the numerical controller 31 side. At the same time, this rectangular wave is supplied to the gate control circuit 29.

On the side of the numerical controller 31, the rectangular wave is multiplied by 4 to generate a feedback pulse signal as shown in FIG. 3 (d).

Then, the numerical control device 31 processes the rectangular wave signal, calculates a new command value voltage by comparison with the target position, and gives it to the D / A converter 37.

The D / A converter 37 converts this digital command value into an analog voltage and inputs it as a command value voltage to the servo control device side. In the servo control device, this command value voltage is input as a new servo command value in the input switching circuit 33. Via servo amplifier
Give to 41.

In this way, the table as a load is moved to near the target position by the rotation of the servo motor.

The table moves near the target position, and the command value from the D / A converter 37 at a certain timing is 1 of the reference value.
When the comparator circuit 39 detects that the signal is within the LSB range, the gate control circuit 35 gives a gate control signal to the input switching circuit 33 from this detection signal, and the analog switch SW3 is instructed from the waveform switching circuit 27. Switch to value voltage.

The waveform switching circuit 27 responds at each timing P1, P2, ..., P6, ... As shown in FIGS.
Command value voltage curve S1 in MODE1, command value voltage curve in MODE2
In S2 and MODE3, the command value voltage curve S3 and in MODE4, the command value voltage curve S4 stands at the output of the analog switch SW2 in sequence.

Therefore, by the switching operation in the input switching circuit 33 described above, when the gate control signal comes, the waveform switching circuit
The voltage at the output of 27 is given to the servo amplifier 41 as a command value voltage.

That is, when the output of the D / A converter 37 is within 1 LSB at the timing P3, the command value voltage on the command value voltage curve S3 for the corresponding MODE3 is the servo amplifier 41.
Will be input to.

Therefore, when the work table is stopped in the positioning area and the command value voltage of the D / A converter 37 is within the range of 1 LSB, the command value from the waveform switching circuit 27 is always zero unless there is a disturbance. It is a voltage and the servo motor is stopped.

In this stopped state, the table moves due to disturbance, but when the amount of movement is small and has not reached 1 LSB,
The command value from the D / A converter 37 remains 0V, and the command value voltage according to S3 is given from the waveform switching circuit 27, and the servomotor performs position correction according to this command value voltage curve S3.

If there is a disturbance exceeding 1 LSB, the servo amplifier 41
The command value voltage for is switched so as to be controlled by the feed pulse from the ordinary position detector 21.

With the command voltage of the normal D / A converter 37,
As shown in the figure, the command value voltage is zero in the zero-cross region, and the position cannot be corrected for a minute disturbance. However, in the case of this embodiment, the eleventh
As shown in the figure, in the zero-cross area, the analog command voltage waveform is used to connect the 37 command value voltage curves of the D / A converter to enable position correction in a narrow range of the positioning area.

In this embodiment, the deviation counter 43 is used instead of the D / A converter 37 as shown by the phantom line in FIG.
It is also possible to input the ".THETA." Signal to the gate control circuit 35 and use the point at which the deviation signal .theta.

Further, when the positioning point is detected from the command value voltage of the D / A converter 37, the gate hold circuit 35 operates the torque hold drive circuit 45 to input it to the torque hold terminal of the servo amplifier 41. It is also possible to avoid the hunting by lowering the gain of the servo amplifier 41 when it approaches. The torque hold drive circuit 45 can be easily configured by a relay circuit as shown in FIG.

[Effects of the Invention] As will be understood from the above description of the embodiments, in short, the present invention detects the movement of the load (3) moved by the servomotor (5) and detects the sin wave (A phase). Position detector (21) that outputs a cos wave (B phase) signal, and the sin wave (A phase) and cos wave (B phase) from the position detector (21) are shaped into a rectangular wave and a feedback pulse is generated. Waveform shaping circuit (23) which outputs to the numerical control device (31) side and gives to the gate control circuit (29) and sine wave and cos wave from the position detector (21) are input. Invert with sin
Wave and inverted cos wave are combined to give a waveform switching circuit (27) to a waveform synthesizing circuit (25) and a rectangular wave from the waveform shaping circuit (23). And a gate control circuit (29) for creating a gate signal (MODE1 to MODE4) and giving it to the analog switches (sw1a to sw1d) of the waveform switching circuit (27), and the gate control circuit (29).
A waveform switching circuit (27) for switching which of the synthesized waves (sin, ▲ ▼, cos, ▲ ▼) is output from the waveform synthesizing circuit (25) by a gate signal from ) From the analog signal as the servo command value and the D / A converter (3
The command value from 7) is input as the servo command value, and the operation of the analog switch (sw3) by the gate control signal from the gate control circuit (35) causes the waveform switching circuit (2
The command value voltage of the D / A converter (37) and the input switching circuit (33) that selects the command value voltage from 7) or the command value voltage of the D / A converter (37) and gives it to the servo amplifier (41). When this command value voltage enters the range of 1 LSB of the reference voltage value, it is determined that the load (3) has reached the positioning area, and the comparator that gives an output to the gate control circuit (35) Circuit (39) and this comparator circuit (3
The gate control circuit (35) for outputting the gate control signal to the analog switch (sw3) of the input switching circuit (33) by inputting the signal from 9).

Therefore, in the present invention, for example, when positioning is performed with the pulse P3 of FIG. 3 (d), the command value voltage of the servo amplifier is set to the third value by the gate signal of FIG. 3 (i).
By switching to the analog signal S3 shown in FIG. 7E and controlling the voltage to be zero, it is possible to perform accurate position control without causing hunting.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a detailed circuit block diagram of the above embodiment, FIG. 3 is a timing chart for explaining the operation of the above embodiment, and FIG. 4 is the above embodiment. 5 is a waveform diagram for explaining the operation of the waveform synthesizing circuit in FIG. 5, FIG. 5 is a block diagram for explaining the operation of the waveform switching circuit in the above embodiment, and FIG. 6 is a waveform diagram showing the output of the waveform shaping circuit in the above embodiment. FIG. 7 is a waveform diagram showing the output of the gate control circuit in the above embodiment, and FIG. 8 is a waveform diagram showing the input from the D / A comparator in the above embodiment.
FIG. 9 is a waveform diagram for explaining the operation of the comparator circuit in the above embodiment, FIG. 10 is a detailed waveform diagram showing the characteristics of the input from the D / A converter in the above embodiment, and FIG. 11 is the input in the above embodiment. FIG. 12 is a waveform diagram showing the output characteristic of the switching circuit, and FIG. 12 is a block diagram showing an example of the torque hold circuit used in another embodiment of the present invention. 1 ... Position detecting means 3 ... Load 5 ... Motor 7 ... Servo amplifier 9 ... Command value calculating means 11 ... Positioning area command value creating means 13 ... Control means 15 ... Control characteristic switching means 21 ... Position detector 23 …… Wave shaping circuit 25 …… Waveform synthesis circuit 27 …… Waveform switching circuit 29 …… Gate control circuit 31 …… Numerical controller 33 …… Input switching circuit 35 …… Gate control circuit 37 …… D / A converter 39 …… Comparator 41 …… Servo amplifier

Claims (1)

(57) [Claims] 1. A sine wave (A phase) and a cos wave (B) are detected by detecting movement of a load (3) moved by a servo motor (5).
Position detector (21) that outputs a phase signal, and the sin wave (A phase) and cos wave (B) from the position detector (21)
Phase) into a rectangular wave, which is output as a feedback pulse to the numerical control device (31) side and also applied to the gate control circuit (29), a waveform shaping circuit (23), and a sine wave from the position detector (21). , Enter cos wave, sin
Wave and cos wave together with the inverted sin wave and the inverted cos wave are added to the waveform switching circuit (27), and the rectangular wave from the waveform shaping circuit (23) A phase and B phase , Phase rectangular waves are combined and gate signal (MODE1
~ MODE4) and apply it to the analog switches (sw1a ~ sw1d) of the waveform switching circuit (27).
9) and the gate signal from the gate control circuit (29), the combined wave (sin, ▲ ▼, c) from the waveform combining circuit (25).
os, ▲ ▼) which outputs the waveform switching circuit (27), and the waveform switching circuit (27) outputs an analog signal as a servo command value and the D / A on the numerical controller (31) side. The command value from the converter (37) is input as a servo command value, and the operation of the analog switch (sw3) by the gate control signal from the gate control circuit (35) causes the waveform switching circuit (2
An input switching circuit (33) for selecting the command value voltage from 7) or the command value voltage of the D / A converter (37) and giving it to the servo amplifier (41), and the command value voltage of the D / A converter (37) When this command value voltage enters the range of 1 LSB of the reference voltage value, it is determined that the load (3) has reached the positioning area, and the comparator that gives an output to the gate control circuit (35) A circuit (39) and the gate control circuit (3) for outputting the gate control signal to the analog switch (sw3) of the input switching circuit (33) by inputting a signal from the comparator circuit (39).
5) A servo control device comprising: