JP3089797B2 - Numerical control unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical control apparatus for controlling a generating motion of a working head in a machine tool such as a grinding machine, a piston lathe, and a laser machine, or a robot.

[0002]

2. Description of the Related Art Generally, in a machine tool or a robot, a relative movement of a work head with respect to a work is controlled by a numerical controller. In the numerical control device, trajectory definition data for determining the work trajectory of the work head is set in advance by, for example, a key input operation, and profile data for the work is created based on the trajectory definition data, and the work head is created. . Here, the profile data refers to information on the position of the work head with respect to the work at a plurality of teaching points on the work track.

[0003] Profile data is created from work locus data.
A typical technique to achieve this is spline interpolation. FIG.
FIG. 4 is an explanatory diagram of spline interpolation. In FIG. 14, P
_j-1, P_j, P _{j + 1}, P_{j + 2}, P_{j + 3}Is the locus definition data
The teaching point given by Spline interpolation consists of two consecutive
Providing trajectory definition data by spline function for each point
A new teaching point is extended between teaching points. S
The pline function passes through four consecutive points of the trajectory definition data
It is determined based on a cubic equation. 4 consecutive points_j-1,
P_j, P_{j + 1}, P_{j + 2}Then, the data to be interpolated is
This is data between the j-th and j + 1-th points at the center. So
Spline function S_j(X) in the section [x_j, X_{j + 1}]
In, S_j(X) = A₀+ A₁x₁+ A_Twox_Two ^Two+ A_Threex_Three ^Three ... Equation 1 Where A₀~ A_ThreeIs a coefficient. And below
Continuation conditional expression of S_j(X_j) = Y_j ............ Equation 2 S_j-1(X_j) = Y_j ............ Equation 3 S '_j-1(X_j) = S '_j(X_j) ............ Equation 4 S ″_j-1(X_j) = S ″_j(X_j) ...... From the formula 5, S_jFind (x), between the j-th and j + 1-th points
Interpolate the data of Next consecutive 4 points P_j, P_{j + 1},
P_{j + 2}, P_{j + 3}Then, the spline function S_{j + 1}(X)
Between the j + 1 and j + 2 points
Interpolate the data of

[0004]

However, the motion created by the spline interpolation has a disadvantage that the change of the velocity component and the acceleration component becomes steep due to the accuracy of the position component. For this reason, there is a problem that the smoothness of the movement in the generating motion of the working head cannot be obtained, and the properties of the machined surface deteriorate in the machine tool.

FIGS. 15 to 17 show the above-mentioned speed component and acceleration component, and exemplify a machine tool for processing a rotationally driven work on a cam surface with a tool such as a cutting tool or a grinding wheel. The trajectory definition data shown in FIG. 15 is given by the positional relationship between the tool and the spindle serving as the rotation center of the workpiece, the forward / backward movement amount (lift amount) of the tool with respect to the spindle, and the rotation angle of the spindle. Here, the tool corresponds to a work head. Assuming that such a trajectory definition data represents a non-circular cam surface as shown in FIG. 15 with a rotation angle taken on the horizontal axis, for example, the velocity component x 'of the profile data obtained by spline interpolation The acceleration component x ″ becomes as shown in FIGS. 16 and 17, and particularly, the steepness of the change in acceleration becomes remarkable, which adversely affects the cam surface properties.

Therefore, conventionally, when profile data is created by a spline interpolation technique, as shown in a flowchart of FIG. 18, a velocity component and an acceleration component are obtained from the profile data, and these are smoothed and processed again. Seeking. However, even with such smoothing processing, the continuity of the velocity and acceleration data of the profile data is incomplete.

On the other hand, as another method of interpolating profile data from trajectory definition data, there is a method using Fourier transform. However, the method using the Fourier transform is
Since a function that defines the entire work trajectory is obtained from all trajectory definition data, the number of trajectory definition data matches the order of the developed frequency function data. Accordingly, a large amount of trajectory definition data is required to obtain an accurate work trajectory.

The present invention eliminates sharp changes in velocity and acceleration components based on profile data extended on a work trajectory by spline interpolation, thereby significantly improving the smoothness of the generating motion of the work head. It is intended to provide a numerical control device.

[0009]

The present invention is shown in FIG.
Thus, an ideal machining locus is defined between the data of the locus definition data a that defines the relative work locus of the work head with respect to the workpiece.
While expanding the data amount by interpolating new data of
Interpolating means 1 for creating inter-profile data b
4, a Fourier transform unit 15 to be deployed to further Fourier series the in <br/> between profile data b obtained by the spline interpolation means 14, the output of the Fourier transform means 15 to the components of n th order limit Data limiting means 16 to perform
It said inverse transforming the Fourier series to the n-th intermediate pro
Relative work locus of the work head based on fill data b
Are within the allowable range of the ideal machining locus.
Inverse Fourier transforming means 17 for obtaining final profile data c redefined to be continuous, and driving means 18 for operating the working head based on the final profile data c
Is provided.

[0010]

In the numerical controller, the trajectory definition data a is expanded by the spline interpolation means 14 to obtain intermediate profile data b, and the intermediate profile data b is subjected to a Fourier transform to restrict the Fourier series component to the nth order. Later, the inverse profile conversion is performed to obtain the final profile data c. Therefore,
The final profile data c obtained by the Fourier transform and the inverse transform functions to increase the continuity of the intermediate profile data b obtained by the spline interpolation means 14, and the steep change of the velocity component and the acceleration component of the final profile data c is reduced. Disappears. Thereby, the movement of the generating motion in the working head becomes smooth.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. FIGS. 2 and 3 show a piston lathe to which the present invention is applied, and FIG. 3 is a schematic right side view partially sectioned as viewed from the right side of FIG. The cutting tool T corresponding to the work head is mounted on the tool mount 2. A piezoelectric actuator 1 is provided on the tool mount 2, and the cutting tool T is driven forward and backward in the direction of the arrow in accordance with a signal input to the piezoelectric actuator 1.

On the other hand, the tool mount 2 is fixedly mounted on a tool mount table 5. The tool mounting table 5 is slidable with respect to the base 6 by a linear guide 4 provided between the base 6 and both sides in the longitudinal direction. The tool mount table 5 is provided with the linear motor 3, and the tool mount table 5 is driven to move forward and backward in the direction of the arrow in accordance with a signal input to the linear motor 3.

FIGS. 4 and 5 are schematic block diagrams showing the connection relationship between the control system of the piston lathe and the numerical controller according to the present invention for controlling the same. The control system of the control device 10 and the control system of the piezoelectric actuator 1 are shown in FIGS. 11 and a control system 12 for the linear motor 3.
0 is connected by a bus. The control device 10 includes a data processing unit 1 controlled by a computer (not shown).
0a and a repetition control unit 10b.

The data processing unit 10a includes a memory 30 storing ideal profile data (corresponding to trajectory definition data a) in a cross section orthogonal to the axis of the workpiece W;
A spline interpolator 31 for interpolating data from 0 using a spline function, and a Fourier transformer for converting the intermediate profile data 31a from the spline interpolator 31 into m-order frequency function data which is a function of the rotational angular velocity ω of the work W. 32; data limiting means 33 for limiting the frequency function data from the Fourier transformer 32 to components of the 0th to nth order (n <m); A frequency separator 34 for separating the frequency function data having a small frequency function and a frequency function data having a low frequency and a large amplitude. The low frequency function data from the frequency separator 34 is inversely transformed to obtain the final profile data 3.
5a, and a Fourier inverse transformer 36, which inversely transforms high-frequency function data from the frequency separator 34 to obtain final profile data 36a.
It is composed of Then, the low-frequency final profile data 35a is stored in the command value memory 23 of the control system 12 of the linear motor 3, and the high-frequency final profile data 36a is stored in the command value memory 20 of the control system 11 of the piezoelectric actuator 1. It is memorized.

The control systems 12 and 11 actually store the linear motor 3 and the piezoelectric actuator 1 based on the low-frequency final profile data 35a and the high-frequency final profile data 36a stored in the command value memories 23 and 20.
Are operated, response value memories 24 and 21 for storing response values when a test cutting operation is performed. These response value memories 24 and 21 are command value memories 23,
20 is a memory for correcting the low-frequency and high-frequency final profile data 35a and 36a stored in the memory 20. This correction is performed by the repetition control unit 10b.

The control system 11 of the piezoelectric actuator 1
Outputs a command value based on high-frequency and small-amplitude data stored in the command value memory 20 by a synchronization signal output based on the rotation of the main shaft 13, and is fed back from a position sensor (not shown) of the piezoelectric actuator 1. A position deviation signal, which is a deviation from the position signal, is output to a high voltage power supply 22 for driving the piezoelectric element to control the piezoelectric actuator 1.

The control system 12 of the linear motor 3 includes the control system 1
As in the case of 1, the synchronization signal based on the rotation of the spindle 13
A command value based on low-frequency, large-amplitude data stored in the command value memory 23 is output, and a position deviation signal that is a deviation from a position signal fed back from a position sensor (not shown) of the linear motor 3 is output to a servo amplifier. 25 to control the linear motor 3. The speed signal of the linear motor 3 is directly fed back to the servo amplifier 25.

As described above, the piezoelectric actuator 1 and the linear motor 3 are controlled based on the final profile data 35a and 36a stored in the command value memories 23 and 20.
The tool T is driven by the generating motion in which the two operations are combined.
Now, a procedure for obtaining the final profile data 35a and 36a from the ideal profile data, which is the most characteristic feature of the present invention, will be described with reference to FIGS.

When the rotation speed of the spindle 13 is commanded, a computer (not shown) executes the program shown in FIG.
Ideal profile data written in M30 (FIG. 7)
(See (a)). The ideal profile data read in step 100 is spline-interpolated in step 102 and expanded to intermediate profile data 31a as shown in FIG. As described above, the spline interpolation is performed by obtaining a spline function from conditional expressions (1) to (6) for every two central points of four consecutive points and performing interpolation. Similarly to the ideal profile data, the intermediate profile data 31a has a tool T corresponding to the amount of deviation from a perfect circle.
And the rotation angle θ (360 °) of the main shaft 13 are represented by m
It consists of equally displaced angles. Since the displacement angle is converted into the time t, it can be treated in the same way as the time axis data as shown in FIG.

Next, in step 104, the intermediate profile data 31a as time axis data is developed into a Fourier series. The frequency function data f (θ) m of the Fourier series obtained at this time (see FIG. 7D) is, for example, 512 assuming that the number m of the intermediate profile data 31a is 512.
It is expanded as the following frequency function data. In the present invention, since such high-order frequency function data is not required, the order is limited to the 0th to nth (n <m) as shown in FIG. 7E (see step 106).

The frequency function data from the 0th order to the 6th order when n = 6 is given by the following equation: f (θ) _n = a ₀ + a ₁ cos (2ωt + ρ ₁ ) + a ₂ cos (4ωt + ρ ₂ ) + a ₃ cos ( 6ωt + ρ ₃ ) + a ₄ cos (8ωt + ρ ₄ ) + a ₅ cos (10ωt + ρ ₅ ) + a ₆ cos (12ωt + ρ ₆ ) Expression 6

The next step 108 is the processing of the frequency separator 34. The frequency function data of the equation (6) is converted from zero-order to second-order low-frequency data f _L (θ) _n = a ₀ + a ₁ cos (2ω).
t + ρ ₁ ) + a ₂ cos (4ωt + ρ ₂ ) and third- to sixth-order high-frequency data f _H (θ) _n = a ₃ cos (6ω
t + ρ ₃ ) + a ₄ cos (8ωt + ρ ₄ ) + a ₅ cos
(10 ωt + ρ ₅ ) + a ₆ cos (12 ωt + ρ ₆ ) are separated and taken out (see FIGS. 7F and 7G).

[0023] In next step 110, returning data f _L (θ) _n of the low frequency to the final profile data 35a of the low-frequency components shown in FIG. 7 (h), the high frequency data f _H (θ)
_n is returned to the final profile data 36a of the high frequency component shown in FIG. In step 112, the final profile data 35a of the low frequency component is stored in the instruction value memory 23.
And the final profile data 36a of the high frequency component is stored in the instruction value memory 20.

As described above, according to the present invention, the ideal profile data is spline-interpolated to secure a sufficient data amount, and the final profile data is obtained based on the Fourier transform in which the intermediate profile data is limited by the nth order components. In the embodiment, the final profile data divided into the low frequency component and the high frequency component is obtained by driving the linear motor 3 with the low frequency component and driving the piezoelectric actuator 1 with the high frequency component. The continuity of the speed component and the acceleration component of each of the components 3 is improved, and as a result, the movement of the piezoelectric actuator 1 can be smoothed.

FIGS. 8 to 10 show the final profile data 35 stored in the command value memories 23 and 20 according to the present invention.
FIG. 17 shows the position characteristics, speed characteristics, and acceleration characteristics in the case of temporarily synthesizing a and 36a.
It can be seen that the sharp change disappears as compared with the conventional characteristics of FIG. The correction performed by the repetition control unit 10b is as follows. That is, the repetition control unit 1
0b, the final profile data 35a, 3a of the low frequency component and the high frequency component stored in the command value memories 23 and 20.
The command value and response value of the low-frequency component and the response value of the high-frequency component stored in the response value memories 24 and 21 are Fourier-transformed by the data processing unit 10a and the Fourier transformer 31, respectively. The deviation between the gain and the phase is calculated every time.

Next, after correcting the frequency function data based on the calculated deviation, the low-frequency component and the high-frequency component are inversely transformed by the Fourier inverse transformers 35 and 36 to indicate the final profile data 35a, 36a. The values are stored in the instruction value memories 23 and 20, respectively, and the instruction values before correction are updated. The numerical controller according to the present invention includes:
It can also be applied to the numerically controlled grinding machine shown in FIG.
In FIG. 11, reference numeral 40 denotes a bed for numerically controlled grinding, on which a table 41 is arranged slidably in the Z-axis direction parallel to the main shaft axis. A headstock 42 having a spindle 43 mounted thereon is disposed on the table 41.
3 is rotated by a servomotor 44. A tailstock 45 is placed on the right end of the table 41.
Of the cam W by the center 46 of the
A work W having a is sandwiched. The work W fits into a positioning pin 48 projecting from the main shaft 43, and the work W
Is the same as the rotation phase of the main shaft 43.

Behind the bed 40, a tool feed shaft (X axis)
The tool table 49 that can move forward and backward is guided along the
Supports a grinding wheel G that is driven to rotate by a motor 54. The tool table 49 is connected to a servo motor 55 via a feed screw (not shown), and is moved forward and backward by forward and reverse rotation of the servo motor 55. Drive unit 59, 6
0 is input with a movement command pulse from the numerical controller 10 ', and the servomotors 55 and 44 driven by the drive units 59 and 60 are supplied with a pulse generator 52,
50 and speed generators 53 and 51 are connected,
These outputs are fed back to each of the drive units 59 and 60, and feedback control of speed and position is performed.

The numerical controller 30 is a device for controlling the grinding of the workpiece W mainly by numerically controlling the rotation of the servomotors 55 and 44. The numerical controller 10 'includes:
A tape reader 5 for inputting ideal profile data, machining cycle data, and the like corresponding to the locus definition data a of the present invention.
6, a keyboard 58 for inputting control data and the like, and a CRT display device 57 for displaying various information are connected.

When the present invention is applied to such a numerically controlled grinding machine, since the grinding wheel G is driven only by the servomotor 55, the n-th order grinding machine is not used via the frequency separator as in the above-described embodiment. The servo motor 55 is controlled by the final profile data obtained by inversely converting the frequency function data limited by the above. Further, the present invention can be applied to a laser processing robot as disclosed in Japanese Patent Application Laid-Open No. 2-36406.

FIG. 12 shows a laser processing robot described in the publication. In FIG. 12, a laser beam head (working head) 61 corresponding to a working head includes
And the upper and lower bases 62 are
It is movable in the axial direction. The carrier 63 is movable in the Y-axis direction with respect to the Y-axis rail 64,
4 is movable in the X-axis direction with respect to the X-axis rail 65. The upper and lower table 62, the carrier 63, and the Y-axis rail 64 are driven by a servomotor via ball screws. Further, the laser beam head 61 has rotation axes P to R axes that rotate about the respective X to Z axes, and is turned by a servo motor (not shown).

Such a robot is provided with each of X to Z axes and P
A three-dimensional creation motion is performed based on position information given to the R axis. Even in the case of three-dimensional motion, it is easy to extend the trajectory definition data by the spline interpolation method described with reference to FIG. 14, perform Fourier transform, data restriction and inverse transform of the intermediate data, and obtain final data. is there. Although the three application examples have been described above, the significance of the present invention is that, as shown in FIG. 13, a certain allowable range is allowed for the actual machining shape with respect to the ideal machining shape (trajectory). By limiting with a predetermined order, variation of the trajectory within the allowable range is effectively generated, and the working head performs a smooth generating motion.

[0032]

As described above, according to the present invention, the frequency function data obtained by Fourier transforming the intermediate profile data obtained by expanding the trajectory definition data by spline interpolation is restricted to a predetermined order, so that the working trajectory of the working head can be reduced. The continuity was improved, and the abrupt changes in the velocity and acceleration components due to the final profile data were eliminated, and the smoothness of the generating motion in the working head could be significantly improved.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a numerical control device according to the present invention.

FIG. 2 is a schematic configuration diagram showing a first embodiment of a machine tool to which the present invention has been applied;

FIG. 3 is a right side view of FIG. 2;

FIG. 4 is a block diagram showing an electrical configuration of a numerical control device and a control system in the embodiment.

FIG. 5 is a block diagram illustrating the numerical controller according to the embodiment in more detail;

FIG. 6 is a flowchart showing a processing procedure of a computer used in the numerical controller.

FIG. 7 is a characteristic diagram showing an operation of each unit in the numerical control device.

FIG. 8 is a characteristic diagram showing a position component of final profile data obtained by the present invention.

FIG. 9 is a characteristic diagram showing a velocity component of final profile data obtained by the present invention.

FIG. 10 is a characteristic diagram showing an acceleration component of final profile data obtained by the present invention.

FIG. 11 is a schematic configuration diagram showing another machine tool to which the present invention is applied.

FIG. 12 is a schematic configuration diagram showing still another machine tool to which the present invention is applied.

FIG. 13 is an explanatory diagram illustrating the basic idea of the present invention.

FIG. 14 is an explanatory diagram of spline interpolation used in the present invention.

FIG. 15 is an explanatory diagram of given trajectory definition data.

FIG. 16 is a characteristic diagram showing a velocity component based on conventional profile data.

FIG. 17 is a characteristic diagram showing a velocity component based on conventional profile data.

FIG. 18 is a flowchart illustrating a conventional numerical control procedure.

[Explanation of symbols]

14 ... spline interpolation means, 15 ... Fourier transform means,
16 data limiting means, 17 Fourier inverse transform means, 1
8. Drive means. DESCRIPTION OF SYMBOLS 10 ... Numerical control apparatus, 10a ... Control apparatus, 30 ... Memory, 31 ... Spline interpolator, 33 ... Data limiting means, 34 ... Frequency separation means, 35, 36 ... Fourier inverse transformer, 31a ... Intermediate profile data, 35
a, 36a: Final profile data.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 19 / 4103,19 / 4093

Claims (1)

(57) [Claims] 1. A numerical control device in which a relative work locus of a work head with respect to a workpiece is set in advance by trajectory definition data, and the work head is created and moved based on the trajectory definition data. Ideal between
Interpolate new data on the machining path to reduce data volume
A spline interpolation means for creating the intermediate profile data expanded, a Fourier transform means for developing a further Fourier series the in <br/> between profile data obtained by the spline interpolation means, an output of said Fourier transform means n Data limiting means for limiting the components up to the next order, and inversely transforming the Fourier series up to the n-th order into the intermediate profile data
The relative working path of the working head
So that its speed and acceleration are continuous within the allowable range of the trace
A numerical control device comprising: an inverse Fourier transform unit for obtaining redefined final profile data; and a driving unit for operating the work head based on the final profile data.