JP3232252B2 - Positioning control device and positioning control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positioning control device and a positioning control method for a positioning servo system in a machine tool or the like.

[0002]

2. Description of the Related Art For example, in a machine tool requiring a high positioning speed and a high machining feed speed, such as a laser beam machine, a servo motor is controlled based on preset position command data to support a work. The positioning of the processing table and the processing head is controlled. As a technique for performing this positioning control with high accuracy without increasing the gain of the control system or incorporating feedforward control, a so-called frequency-domain inverse transfer function correction control method has been conventionally known. ing. This control method calculates a transfer function in the frequency domain from actual movement position data obtained as a result of control by the position command data and ideal position command data giving an ideal movement amount, and based on the transfer function, This is to correct the frequency characteristics of the position command data.

[0003]

However, the inverse transfer function correction control method in the frequency domain requires FFT (Fast Fourier Transform) processing when calculating the transfer function. This FFT processing takes time, and it has been difficult to perform positioning control at high speed. In particular, when the operation speed of the processing table or the processing head becomes high, the FFT processing cannot be reliably performed with respect to the operation speed, and there is a problem that high-precision positioning control cannot be performed. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a high-speed positioning control without increasing the gain of the control system or incorporating feedforward control. Another object of the present invention is to provide a positioning control device and a positioning control method that can be performed with high accuracy.

[0005]

According to a first aspect of the present invention, there is provided a positioning control device for positioning a control target based on corrected position command data and the corrected position command data. Position data storage means for storing actual movement position data obtained as a result of the control, and a transfer function time for obtaining a transfer function time element at the present time based on the stored corrected position command data and actual movement position data. Element calculating means, and position command data correcting means for correcting position command data based on the obtained transfer function time element, wherein the position of the control target is controlled based on the corrected position command data. is there.

According to the second aspect of the present invention, in the first aspect,
The position data storage means stores the corrected position command data and the actual movement position data for each of a plurality of past data from the latest one.

According to a third aspect of the present invention, in the second aspect,
The position data storage means stores at least five corrected position command data and at least five actual movement position data.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the first differential data calculating means for calculating differential data of the position command data, and the actual moving position stored in the position data storing means. A second differential data calculating means for calculating differential data of the data, wherein the transfer function time element calculating means calculates a transfer function time element based on the corrected position command data, the actual movement position data and the differential data thereof. The position command data correcting means corrects the position command data based on the obtained transfer function time element, the position command data and its differential data.

According to a fifth aspect of the invention, there is provided a positioning control method comprising:
The corrected position command data and the actual movement position data obtained as a result of positioning control of the control object based on the corrected position command data are stored, and the stored corrected position command data and the actual movement position data are stored. Based on the position data, the current transfer function time element is obtained, the position command data is corrected based on the obtained transfer function time element, and the position of the control target is controlled based on the corrected position command data. It was done.

Therefore, the first to fifth aspects of the present invention have the following effects. According to the first and fifth aspects of the invention, the position command data is corrected based on the transfer function time element. Then, the position of the control target is controlled based on the corrected position command data. Further, the corrected position command data and the actual movement position data obtained as a result of performing positioning control of the control target based on the corrected position command data are stored. Then, a transfer function time element at the present time is obtained based on the stored corrected position command data and actual movement position data, and the position command data is corrected based on the obtained transfer function time element.

As described above, the current position command data is corrected by the transfer function time element obtained based on the past corrected position command data and the actual moving position data, and the corrected position command data is added to the corrected position command data. The control target is positioned based on the control. That is, since the inverse transfer function correction control is performed only in the time domain and not in the frequency domain, it is only necessary to perform a simple calculation without performing an FFT, an inverse FFT, or the like that requires a long processing time.

According to the invention of claim 2, since the transfer function time element that changes every moment is sequentially obtained based on a plurality of immediately preceding data, an appropriate transfer function time element is always obtained.

According to the third aspect of the present invention, it is only necessary to store at least five pieces of past data, and it is not necessary to store a large amount of data. Therefore, it is necessary to provide a large-capacity data storage means. Absent.

According to the fourth aspect of the present invention, by calculating the differential data, it is possible to reflect the speed and acceleration of the position command data during the positioning control.
For this reason, the behavior that may occur in the future of the device is reliably predicted, and the positioning control can be performed with higher accuracy.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a control block diagram of the positioning control device of the present embodiment.
This positioning control device controls the position of a processing table supporting a work in the X-axis direction in a laser processing machine, for example.
It is used for controlling the positioning in the axial direction. For example, an AC servomotor is used as the driving means in each axis direction.
Axis controller 11, Y axis controller 12, and Z
It is controlled by the axis controller 13. These controllers 11, 12, 13 are
U (central processing unit), RO storing control programs, etc.
M and a RAM for storing various information. Since the three controllers 11, 12, and 13 have the same configuration, FIG. 1 shows only the X-axis controller 11 and the X-axis servomotor 14 controlled by the controller 11.

A ball screw 15 is connected to the output shaft of the X-axis servo motor 14, and a carriage 16 is screwed to the ball screw 15. A working table (not shown) is connected to the carriage 16. Accordingly, the carriage 16 is moved in the X-axis direction together with the processing table by the rotation of the ball screw 15 accompanying the driving of the servomotor 14. In the present embodiment, the servomotor 14, the carriage 16, and the like are control targets. The position detector 17 detects the rotation angle of the servomotor 14 and
6 is obtained.

The position data program unit 18 has an X axis,
Target movement position data in three directions of the Y axis and the Z axis are programmed in advance. Position command data distribution unit 19
Distributes the target movement position data input from the position data program unit 18 to position command data r (t) in each of the X-axis, Y-axis, and Z-axis directions.
1, 12 and 13.

Here, the X-axis controller 11 will be described. The first differential data calculating section 20 performs first-order differentiation of the position command data r (t) input from the position command data distribution section 19 with time t. r ′ (t) and data r ″ (t) that is second-order differentiated at time t are calculated.
The differential data calculator 20 calculates the speed component and the acceleration component of the position command data r (t). Then, the first differential data calculator 20 calculates the position command data r (t) and the same data r
The differential data r ′ (t) and r ″ (t) of (t) are output to the position command data correction unit 21.

The position command data correction section 21 receives the position command data r (t) and the differential data r '(t), r "(t) input from the first differential data calculation section 20 and a transfer function time to be described later. Transfer function time elements α1, α input from the element operation unit 22
2 and α3, the corrected position command data i (t) is obtained according to the following equation (1). Then, the position command data correction unit 21 calculates the corrected position command data i (t)
Is output to the subtractor 23. i (t) = α1 · r (t) + α2 · r ′ (t) + α3 · r ″ (t) (1) Further, the subtractor 23 outputs the movement position data (actual Then, the subtracter 23 calculates the difference between the input corrected position command data i (t) and the actual movement position data O (t), and calculates the difference. Output to the servo motor drive unit 24.
The servo motor drive unit 24 controls the drive of the servo motor 14 based on the input value.

On the other hand, the actual movement position data O (t) of the carriage 16 output from the position detection unit 17 is also output to the position data storage unit 25. Further, the corrected position command data i (t) output from the position command data correction unit 21 is also output to the position data storage unit 25. Position data storage unit 2
5 is the corrected position command data i (t1) to i (t5) for the past five and the corresponding actual movement position data O (t1) to O (t5) as shown in FIGS. ) Are stored. That is, the position data storage unit 25 stores the latest data i (t)
, O (t), the latest input data i
(t) and O (t) are stored as i (t1) and O (t1) in the column of t1, and the data i stored in the columns of t1 to t4.
(t1) to i (t4) and O (t1) to O (t4) are converted to t2 to t5, respectively.
Are sequentially shifted to i (t2) to i (t5) and O (t2) to O (t
Store again as 5). The data i (t5) and O (t5) stored in the column of t5 are discarded as used data.

The second differential data calculator 26 stores the actual movement position data O (t) stored in the position data storage 25.
By using 1) to O (t5), data O ′ (t1), O ′ (t2), O ′ (t3), and O ′ (t4) that are first-order differentiated at time t, and second-order data at time t Differentiated data O "(t1), O" (t2), O "(t
3) is calculated. For example, as shown in FIG. 2, the first-order differential data O ′ (t1) is obtained by comparing actual movement position data O (t1) and O (t2).
And the second-order differential data O "(t1) represents the position change amount per unit time (that is, the speed) existing between the first-order differential data O '(t1) and O' (t2). In other words, the second differential data calculation unit 26 calculates the speed change amount per unit time (i.e., the amount of acceleration) existing on the basis of the five actual movement position data O (t1) to O (t5). The four actual speed data O '(t1) to O' (t4) and the past three actual acceleration data O "(t1) to O" (t3) are calculated. The data calculation unit 26 calculates three actual movement position data O (t1) to O (t3) and first order differential data O ′ (t1) to O ′ (t
3) and the second-order differential data O "(t1) to O" (t3) are output to the transfer function time element calculation unit 22. The position data storage unit 25 stores the corrected position command data i
The three data i (t1) to i (t3) of (t1) to i (t5) are output to the transfer function time element calculation unit 22.

The transfer function time element operation unit 22 receives the input data O (t1) to O (t3), O '(t1) to O' (t3), and O "(t1).
ＯO ”(t3), i (t1) to i (t3) and transfer function time elements α1, α2, α3 according to the following three equations (2).
Ask for. Then, the transfer function time element calculation unit 22 outputs the obtained transfer function time elements α1, α2, α3 to the position command data correction unit 21. i (t1) = α1 · O (t1) + α2 · O ′ (t1) + α3 · O ″ (t1) i (t2) = α1 · O (t2) + α2 · O ′ (t2) + α3 · O ″ (t2) i (t3) = α1 · O (t3) + α2 · O ′ (t3) + α3 · O ″ (t3) (2) Next, the operation of the positioning control device configured as described above will be described with reference to the flowchart of FIG. The operation of this positioning control device is started, for example, in accordance with the start of a processing operation according to a processing operation program of a laser processing machine.

When the machining operation according to the machining operation program is started, first, data i (t1) to i (t5), O as default values are stored in columns t1 to t5 of the position data storage unit 25.
(t1) to O (t5) are set, and the transfer function time elements α1, α2, α3 are provisionally determined by default values (step S1). That is, at the start of machining, the transfer function time elements α1, α2, α3 are stored in the position data storage unit 25.
This is because the data necessary for calculating is not stored. Next, the target movement position data in the three axis directions in the position data program unit 18 is stored in the position command data distribution unit 1.
9 is distributed to position command data r (t) in each of the X-axis, Y-axis, and Z-axis directions, and is taken into each first differential data calculation unit 20 (step S2).

Subsequently, the first differential data calculator 20 calculates first differential data r '(t) and second differential data r "(t) of the position command data r (t) (step). S3).
Next, based on the data r (t), r '(t), and r "(t) and the transfer function time elements α1, α2, α3, the position command data correction unit 21 according to the above equation (1). Calculates the corrected position command data i (t) (step S).
4).

Then, the servo motor 14 is controlled based on the corrected position command data i (t), for example, to move the carriage 16 to a desired position in the X-axis direction (step S5).

Next, the corrected position command data i (t),
The actual movement position data O (t) of the carriage 16 detected by the position detection unit 17 is
1 are stored as i (t1) and O (t1) (step S
6). At this time, the data i (t1) to i (t4) and O (t1) to O (t4) stored in the columns of t1 to t4 respectively become t2 to t2.
Shifted to the column of t5 in order, i (t2) to i (t5), O (t2)
ＯO (t5).

Next, based on the actual movement position data O (t1) to O (t5) in the position data storage unit 25, first order differential data O '
(t1), O '(t2), O' (t3), O '(t4) and second-order differential data O "(t1), O" (t2), O "(t3) are second differential data The calculation is performed by the calculation unit 26 (step S7).

Subsequently, three actual movement position data O (t1) to
O (t3), three first-order differential data O '(t1) to O' (t3), 3
Two second-order differential data O "(t1) to O" (t3) and three corrected position command data i (t) in the position data storage unit 25.
1), i (t2) and i (t3), according to the above equation (2),
In the transfer function time element calculation unit 22, the transfer function time element α
1, α2 and α3 are calculated (step S8). next,
It is determined whether or not the machining operation program has been completed (step S9), and when it has been completed, all the processes are completed.
On the other hand, if the machining operation program has not been completed,
Returning to step S2, the operations of steps S2 to S9 are repeated.

As described above, in the present embodiment, as shown in the above equation (1), the corrected position command obtained by multiplying the position command data r (t) by the transfer function time element α. The servo motor 14 is controlled based on the data i (t).

That is, in the positioning control, if the target value is R, the input value is I, the output value is O, and the transfer function is G, the transfer function G can be expressed by the following equation (3). G = O / I (3) In this case, if the output value O becomes equal to the target value R, in other words, if G = R / I holds, the positioning control is ideally performed. This G = R / I is given by I =
(1 / G) · R. That is, in the equation (1), if the corrected position command data i (t) is replaced with the input value I and the position command data r (t) is replaced with the target value R, the transfer function time element α becomes (1 / G) Can be replaced by Therefore, by calculating the value of the transfer function time element α, the ideal input value i for the servomotor 14 is obtained.
(t).

The value of the transfer function time element α can be obtained according to the above equation (2). That is, G = O / I in the above equation (3) can be transformed into I = (1 / G) · O. Therefore, in the above equation (2), the past three position command data i (t1) to i (t3) are input values I, and the past three actual movement position data O (t1) to O (t3) are output values. If replaced with O, α can be replaced with (1 / G). Therefore, based on the past three input values and output values, equation (2)
By solving the simultaneous equations according to the above equation, the transfer function time element α can be obtained. That is, the transfer function time element α represents the dynamic characteristic of the positioning control system that changes every moment, and represents the transfer function in the time domain obtained from the immediately preceding input / output value. Therefore, by substituting the transfer function time element α into the above equation (1), an ideal input value i (t) can be given to the servomotor 14.

Since the positioning control device of the present embodiment operates as described above, the following effects are obtained. (A) Since the inverse transfer function correction control is performed only in the time domain and not in the frequency domain, it is not necessary to perform an FFT or an inverse FFT, which requires a long processing time, and the simple equations (1) and (2) can be used. It is only necessary to use simple arithmetic expressions. For this reason, positioning control can be performed at high speed and with high accuracy, and a positioning control device excellent in responsiveness can be provided at low cost.

(B) By calculating the first-order differential data and the second-order differential data of the position command data, it is possible to reflect the speed component and the acceleration component of the position command data during positioning control. For this reason, the behavior that may occur in the future of the device is reliably predicted, and the positioning control can be performed with higher accuracy.

(C) Since the ever-changing transfer function is sequentially obtained based on a plurality of immediately preceding data, an appropriate transfer function can always be reflected in the position command data.

(D) It is sufficient to store only the minimum number of past data required for the operation, for example, five, and it is not necessary to store a large amount, so a large-capacity memory is provided. No need.

The embodiment of the present invention may be modified, for example, as follows. (A) The positioning control device of the present invention is applied to various positioning controls such as control of a device having four or more axes and robot control.

(B) Six or more pieces of past data may be stored, and differential data up to the third order or more may be obtained as differential data. When the data of the nth order is obtained,
Correspondingly, α1 to α (n−
You can ask for up to 1).

[0038]

As described in detail above, according to the present invention, the following excellent effects can be obtained. According to the first and fifth aspects of the present invention, since the inverse transfer function correction control is performed only in the time domain and not in the frequency domain, the FF that requires a long processing time is used.
It is only necessary to perform a simple operation without performing T or inverse FFT. For this reason, positioning control can be performed at high speed and with high accuracy, and a positioning control device excellent in responsiveness can be provided at low cost.

According to the second aspect of the present invention, since the transfer function time element that changes every moment is sequentially obtained based on a plurality of immediately preceding data, an appropriate transfer function time element is always obtained. This is reflected in the position command data.

According to the third aspect of the present invention, it is only necessary to store at least five pieces of past data, and it is not necessary to store a large amount of data. Therefore, it is necessary to provide a large-capacity data storage means. Absent.

According to the fourth aspect of the present invention, by calculating the differential data, it is possible to reflect the speed and acceleration of the position command data during the positioning control. For this reason, the behavior that may occur in the future of the device is reliably predicted, and the positioning control can be performed with higher accuracy.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing each data stored in a position data storage unit.

FIG. 3 is an explanatory diagram showing corrected position command data and actual movement position data.

FIG. 4 is a flowchart showing the operation of the positioning control device.

[Explanation of symbols]

11 ... X-axis controller, 12 ... Y-axis controller, 13 ... Z-axis controller, 14 ... X-axis servomotor as control target, 16 ... Carriage as control target, 17 ... Position detector, 20 ... A first differential data calculating unit as differential data calculating means, 21... A position command data correcting unit as position command data correcting means, 22.
A transfer function time element operation unit as a transfer function time element operation unit; 25, a position data storage unit as a position data storage unit; 26, a second differential data calculation unit as a second differential data calculation unit.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-348316 (JP, A) JP-A-8-227309 (JP, A) JP-A-10-149210 (JP, A) JP-A-7- 295652 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G05B 19/18-19/46 G05B 13 / 02,11 / 36,23 / 02 G05D 3/00-3/12 B23Q 15/00-15/28

Claims (5)

(57) [Claims] 1. Position data storage means for storing position command data after correction and actual movement position data obtained as a result of positioning control of a control target based on the position command data after correction, and the stored correction Transfer function time element calculating means for obtaining a transfer function time element at the present time based on the subsequent position command data and actual movement position data; and position command data for correcting the position command data based on the obtained transfer function time element. A positioning control device having a correcting means, and performing positioning control of a control target based on the corrected position command data. 2. The positioning control device according to claim 1, wherein said position data storage means stores the corrected position command data and actual movement position data for each of a plurality of past data from the latest one. 3. The positioning control device according to claim 2, wherein said position data storage means stores at least five corrected position command data and at least five actual movement position data. 4. A first differential data calculating means for calculating differential data of the position command data, and a second differential data calculating means for calculating differential data of actual movement position data stored in the position data storage means. Wherein the transfer function time element calculating means obtains a transfer function time element based on the corrected position command data and the actual movement position data and its differential data, and the position command data correcting means calculates the transfer function obtained. The positioning control device according to any one of claims 1 to 3, wherein the position command data is corrected based on the time element, the position command data, and its differential data. 5. The corrected position command data and actual movement position data obtained as a result of positioning control of a control target based on the corrected position command data are stored, and the stored corrected position data is stored. The current transfer function time element is obtained based on the command data and the actual movement position data, the position command data is corrected based on the obtained transfer function time element, and the control target is determined based on the corrected position command data. A positioning control method for performing positioning control.