JP2000353006A - Numerical controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To work a smooth curved surface in the pick feed direction as well by suppressing generation of difference in levels between paths. SOLUTION: A midpoint Pc of a segment to connect adjacent points Pi, j, Pi, j+1 of a path Pi is calculated. A perpendicular can be drawn down on the segment to connect the adjacent points of front and rear paths Pi-1, Pi+1 from the midpoint Pc and the minimum segment of the length of the perpendicular is selected. Smooth curves f(t), g(t), h(t) to pass points (Pi, j, Pi, j+1, Qs, Qe, Rs, Re) on both ends of the respective segments are calculated. An auxiliary point PjH is inserted between the points Pi, j, Pi, j+1 by a midpoint f(1/2) of the curve for the path Pi and positions g(tq), h(tr) on the respective curves corresponding to positions Qc, Rc of respective legs. The auxiliary points are inserted between respective points, the auxiliary points are added to a command point string of the path Pi and the smooth curve is calculated. Such calculation is similarly performed for respective paths as well, the difference in levels between the paths are eliminated and the curve is made to be smoothly continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical control device used for a machine tool for processing a workpiece having a smooth surface such as a die.

[0002]

2. Description of the Related Art In the machining of a curved surface of a mold or the like, a curved surface machining program is formed by instructing one path as a machining path by using a series of points and instructing a plurality of passes by pick feed little by little. are doing. On the basis of such a machining program, the numerical controller converts a minute line segment between commanded points into a smooth curve, for example, NURB
An S curve, a spline curve, a Bezier curve, and the like are connected by a minus and interpolation is performed based on this curve.

[0003]

In the above-mentioned prior art, the numerical controller obtains a curve passing through the points of the point sequence along the path of the commanded machining shape point sequence and interpolates based on this curve. Due to the processing, the processing of the curve is performed almost smoothly within one pass. However, the relationship between adjacent passes is merely picked, and no consideration is given to smoothing a curved surface between the passes. Therefore, depending on the curved surface, a step may occur between adjacent passes, and the processed surface may not be smooth.

In particular, the traveling direction (machining direction) of each pass is 1
When a path is instructed not in the direction but in a round trip, or when the path has an inflection point, the step between adjacent paths tends to increase. That is, there has been a problem that a step is generated in the pick feed direction at the time of processing the curved processing surface. Therefore, an object of the present invention is to provide a numerical control device capable of suppressing occurrence of a step between paths.

[0005]

According to the present invention, a program in which a plurality of pick feeds and a sequence of machining shape command points are alternately commanded is read, and a smooth curve connecting the sequence of machining shape command points is determined, and the curve is obtained. The present invention relates to a numerical control device that performs interpolation based on a machining shape command point sequence for obtaining a smooth curve and a machining shape command point sequence before and after a pick feed for the machining shape command point sequence. Is read, and based on the relationship between the machining shape command point sequence to seek the smooth curve and the preceding and subsequent machining shape command point sequences, the machining shape command point sequence to seek the smooth curve. Auxiliary points are added between the sequence of points, and the machining shape command point sequence to which the auxiliary points have been added is corrected with a smooth curve, so that a smooth curve can be obtained without generating a step in the pick feed direction. So that can be obtained.

In particular, a pick feed is interposed between the machining shape command point sequence corresponding to any two adjacent points in the machining shape command point sequence, and two points on the preceding machining shape command point sequence are interposed.
Point, and picking up the machining shape command point sequence corresponding to two adjacent points of the machining shape command point sequence, picking two points on the subsequent machining shape command point sequence, A function that smoothly connects the two points is obtained, an auxiliary point on the machining shape command point sequence is obtained using the function, and an auxiliary point taking into account the curve of the path before and after this path is added to the machining shape command point sequence. By obtaining a smooth curve by this processing shape command point sequence, and performing interpolation and processing based on this curve,
A smooth curved surface can also be processed in the pick feed direction.

[0007]

FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention. One pass for machining is instructed by a machining shape instruction point sequence of points indicating three-dimensional coordinate positions, and after a predetermined amount of pick feed, the next pass is instructed, and this is sequentially repeated. A processing program for processing a three-dimensional curved surface is formed. Any i-th path consists of the commanded machining shape commanded sequence of points in the machining program P _i, the previous path from the path P _i (i-th path immediately before pick-feed to the path) The path following P _i−1 and the i-th path P _i (the path immediately after pick feed from the i-th path) is set to P _{i + 1} . In the example of FIG.
An example in which a pass is instructed in a round trip is described.
-1) The path P _i-1 moves from left to right in FIG. 1, the i-th path P _i moves from right to left, and the (i + 1) -th path P _{i + 1} moves from left to right. Arbitrary two points of the machining shape command point sequence constituting the i-th pass P _i are defined as P _{i, j} and P _{i, j + 1} .

[0008] During each line segment line segment P _i connecting these two _{points, j} P _i, with respect to _{j + 1,} connecting the front and rear of the path P _i-1, sequence of points P i _{+ 1} of the path P _i, one Find the closest line segment. That is,
A line segment P _{i, j} connecting two points in the sequence of points in the path P _i ,
Since the closest line segment connecting P _{i, j + 1} and two points in the preceding and following paths P _i-1 and P _{i + 1} is adjacent to each other,
In the processing of these line segment regions, a smooth curve between the points P _{i, j} and P _{i, j + 1} of the path P _i and a smooth curve between the points correspond to the adjacent paths so that no step is generated. If a smooth curve is considered in consideration of the curve in the line segment, it is possible to process a smooth curved surface without generating a step in the pick feed direction.

As a method of obtaining a line segment closest to the line segment P _{i, j} P _{i, j + 1} , in the present embodiment, a line segment P _{i, j} P _{i, j + 1} is calculated from the midpoint Pc of the line segment P _{i, j} P _{i, j + 1.} It is determined whether the perpendicular can be lowered for each line segment of the paths P _i-1 and P _{i + 1} of this path. If there is no line segment that can be lowered, this correction process is not performed. Is selected as the closest line segment. In the example of FIG. 1, on the path P _i-1 , the points P _{i-1, a}
Line connecting the preparative point _{Pi-1, a + 1,} the path P _{i + 1,} line segments connecting the points P _{i + 1, b} and the point _{P i + 1, b + 1} , the line segment P _{i, j} It is assumed that a line segment closest to P _{i, j + 1} has been detected. Note that the foot dropped from the midpoint Pc to the line segment P _{i-1, a} P _{i-1, a + 1} is Qc (coordinate position), and the line segment P _{i + 1, b} P _{i + 1, The} foot lowered to _{b + 1} is defined as Rc (coordinate position).

Then, as described later, a pick feed
In order to obtain a smooth curved surface in the direction, the point sequence of the path Pi
Determine the start and end points to correct. Vector (P
_{i-1, a}P_{i -1, a + 1}) Is the vector (P_{i, j}P_{i, j + 1}Same direction as)
, That is, the vector (P _{i-1, a}P_{i-1, a + 1}) And ba
Kutor (P_{i, j}P_{i, j + 1}) Is positive, the point P
_{i-1, a}Is the starting point Qs and the point P_{i-1, a + 1}Is the end point Qe. vice versa
Vector (P_{i-1, a}P_{i-1, a + 1}) Is the vector (P_{i, j}P
_{i, j + 1}), The vector (P_{i-1, a}P_{i-1, a + 1})When
Vector (P_{i, j}P_{i, j + 1}) Is not positive, the point P
_{i-1, a}To the end point Qe, point P_{i-1 , a + 1}Is the starting point Qs.

Similarly, the vector (P_{i + 1, b}P_{i + 1, b + 1})But
Vector (P_{i, j}P_{i, j + 1}) In the same direction as the vector (P
_{i + 1, b}P_{i + 1, b + 1}) And vector (P_{i, j}P_{i, j + 1})
If positive, point P_{i + 1, b}Is the starting point Rs and the point P_{i + 1, b + 1}The end point
Re. Conversely, the vector (P _{i + 1, b}P_{i + 1, b + 1}) Is baek
Torr (P_{i, j}P_{i, j + 1}), The vector (P_{i + 1, b}
P_{i + 1, b + 1}) And vector (P_{i, j}P_{i, j + 1}) Is a positive inner product
If not, point P_{i + 1, b}To the end point Re, point P_{i + 1, b + 1}Starting point R
s.

Since the example of FIG. 1 shows an example of a reciprocating path, the traveling direction in each path changes alternately, and the vector (P _{i-1, a} P _{i-1, a + 1} ) and the vector (P
_{i + 1, b} P _{i + 1, b + 1} ) and the vector (P _{i, j} P _{i, j + 1} ) are in the opposite directions, and the inner product is not positive. Therefore, the points P _{i-1, a} and P _{i + 1, b} on the starting point side of each path P _i-1 and P _{i + 1} are changed to the end point Q
e, Re, the end point P _{i-1, a + 1} , and the point P _{i + 1, b + 1} are the start points Q
s and Rs.

Next, in order to obtain a smooth curve, the point P
_{i, j} , point P _{i, j + 1} , point Qs, point Qe, Rs, tangent vector P _{i, j} ′ of Re, P _{i, j + 1} ′, Qs ′, Qe ′, Rs ′,
Re ′ is obtained, and the points Qs, Qe and the tangent vector Qs ′,
From Qe ′, through point Qs and point Qe, g (0) = Qs,
g (1) = Qe Smooth curve (Bézier curve, NU
RBS curve, spline curve) g (t) is generated. For example, in the case of a spline curve, g (t) = Agt ³ + Bgt ² + Cgt + Dg, and this spline curve equation g (t) and an equation obtained by differentiating this equation, a point Qs, a point Qe, and a tangent vector Q
The coefficients Ag, Bg, Cg, and Dg of the spline curve equation g (t) are obtained from s ′ and Qe ′, and the spline curve equation g
(T) is generated.

Similarly, the points Rs and Re and the tangent vector R
From s ′ and Re ′, through point Rs and point Re, h (0) =
A smooth curve (Bézier curve, NURBS curve, spline curve) h (t) that satisfies Rs, h (1) = Re can be generated.

Further, the points P _{i, j} , P _{i, j + 1} , and the tangent vectors P _{i, j} ′, P _{i, j + 1} ′ make the points P _{i, j} , P _{i, j + 1} , A smooth curve (Bézier curve, NURBS curve, spline curve) f (t) that satisfies f (0) = P _{i, j} and f (1) = P _{i, j + 1} is generated.

As the tangent vector, an arc passing through three points before and after the point for which the tangent vector is to be obtained is obtained, and the tangent vector of this arc at the point for which the tangent vector is to be obtained is defined as the tangent vector. . For example, the path P _i
Point P _i, tangent vector P _i at _{j, j} 'in the front and rear of point _{P i, j-1, P} i, j + 1 and the point P _i, obtains an arc passing through 3 points _j, the The tangent vector at the point P _{i, j} in the arc is defined as the tangent vector at the point P _{i, j} . The starting point of the path,
At the end point, since there is no point before or after, the tangent vector at the start point is an arc passing through the three points of the start point and the next two points following the start point, and the tangent vector at the end point is the tangent vector at the end point and the point before the end point. It is determined based on an arc passing through two of three points. For example, a tangent vector P _{i, 1} ′ at the start point P _{i, 1} of the path P _i is obtained by calculating an arc passing through the start point P _{i, 1} , the next point P _{i, 2} , and the next point P _{i, 3.} A tangent vector P _{i, 1} ′ of the starting point P _{i, 1} is obtained. In addition, the end point P _i, tangent vector P _i in _{ni, ni} 'is two points before the end point P
_It is determined from an arc passing through _{i, ni-2, Pi , ni-1} and the end point _{Pi, ni} .

The thus obtained adjacent path P_i-1,
P_i, P_{i + 1}Is a line segment connecting consecutive points in
A smooth curve g that smoothly connects the points at both ends of a straight line segment
Based on (t), h (t) and f (t), the path P_iSmooth
Path P before and after the curve f (t)_i-1, P_{i + 1}of
The path P is affected by the smooth curves g (t) and h (t).
_{i- 1}, P_i, P_{i + 1}The smooth curve of the pick feed direction
The processing point sequence is corrected so that it continues smoothly. this
In the embodiment, the point P_{i, j}And point P_{i, j + 1}Curve g between
(T), h (t), f (t)_jHSeeking
In this case, the path P _iSmooth curve as command point of
I want to ask.

In this embodiment, parameters tq and tr based on the ratio of the distance from the start point to the position of the foot with respect to the distance from the start point to the end point are determined by the following equations (1) and (2). tq = | QsQc | / | QsQe | (1) tr = | RsRc | / | RsRe | (2) Next, an arithmetic operation of the following three equations is performed to obtain an auxiliary point P _{jH to} be _{interpolated.} Ask for. P _jH = (K1 * f (1/2) + K2 * g (tq) + K3 * h (tr)) / (K1 + K2 + K3) (3) In the above three equations, K1, K2, and K3 are weights of each point. This value may be K1 = 2, K2 = K3 = 1, or the like.

[0019] That is, in this embodiment, there the path P _i of adjacent points P _{i, j,} the point P _i, the closest distance to the line segment connecting the _{j + 1,} the front and rear of the path P _i-1, by detecting the line segment connecting the points adjacent P i _{+ 1,} the path P _i points P _{i neighboring, j,} point P _i, the curve of the front and rear of the path close to the curve passing through _{j + 1} The intermediate point position f (1/2) of the smooth curve f (t) passing through the detected and adjacent points P _{i, j} and P _{i, j + 1,} and the closest detected line segment in the preceding and following paths Are weighted for each position by means of positions g (tq) and h (tr) on the smooth curves g (t) and h (t) passing through the points at both ends of With
P _{i, j,} and the point P _i, is to insert the auxiliary point P _jH between _{j + 1.} Then, by determining the smooth curve of the path P _i regarded as a command point sequence also the inserted auxiliary points, among paths taking into account the longitudinal paths P _i-1, P i _{+ 1} of the curve of the path P _i Are also smoothly continuous.

Although the primary equation of the third equation is used as an equation for calculating the auxiliary point _PjH , a quadratic equation or a cubic equation may be used if necessary. The auxiliary point P _jH obtained in this way is also the i-th point.
Smooth curve of the i path P _i regarded as a command point of the path P _i (Bezier curve, NURBS curve, spline curve) f (t)
Generate

The above is the operation principle for obtaining a smooth curved surface also in the pick feed direction in the present embodiment.
FIG. 2 is a block diagram of a main part of a numerical control device that corrects a point sequence of a machining program and controls machining based on an operation principle for obtaining a smooth curved surface also in the pick feed direction. The processor 11 is a processor that controls the numerical controller 10 as a whole, and a ROM
The system program stored in the memory 12 is read out, and the numerical controller 10 is entirely controlled in accordance with the system program. The RAM 13 stores temporary calculation data, display data, and the like. The CMOS memory 14 is backed up by a battery (not shown), is configured as a nonvolatile memory that retains a storage state even when the power of the numerical controller 10 is turned off, and stores a machining program and the like.

The interface 15 is an interface for an external device, to which an external device 82 such as a paper tape reader, a paper tape puncher, or a floppy disk driver is connected. The processing program is read from the memory means of the external device 82 and stored in the CMOS memory 14.
The CMOS memory 1 edited in the numerical controller 10
4 can be output to an external memory.

A PMC (programmable machine controller) 16 controls a machine tool by a sequence program built in the numerical controller 10. That is, in accordance with the functions instructed by the machining program, these sequence programs convert the signals into necessary signals on the machine tool side, and output the signals from the I / O unit 17 to the machine tool. Various actuators on the machine tool are operated by this output signal. Also,
Upon receiving signals from limit switches on the machine tool side and various switches on the machine operation panel, necessary processing is performed, and the signals are passed to the processor 11. Image signals such as the current position of each axis, alarms, parameters, and image data are sent to the display device of the display / MDI unit 80 and displayed on the display device. The interface 18 receives data from the keyboard in the display / MDI unit 80 and passes the data to the processor 11.
The interface 19 is connected to the operation panel 81 and passes commands from the operation panel to the processor 11.

The axis control circuits 30, 31, and 32 receive the movement commands of the X, Y, and Z axes from the processor 11, and output the commands of the respective axes to the servo amplifiers 40, 41, and 42. The servo amplifiers 40, 41, 42 drive the servo motors 50, 51, 52 of each axis in response to this command. Pulse coder 60, 61, 62 as a position / speed detector is attached to servo motors 50, 51, 52 of each axis.
The feedback signal from the pulse coder is fed back to the axis control circuits 30, 31, 32. Each of the servo control CPUs incorporated in the axis control circuits 30, 31, and 32 performs each processing of a position loop and a speed loop based on these feedback signals and the above-mentioned movement command, and performs final drive control. A torque command is obtained for each axis to control the positions and speeds of the servo motors 50, 51, and 52 for each axis.

The spindle control circuit 70 outputs a spindle speed signal to the spindle amplifier 71 in response to a spindle rotation command and a command such as spindle orientation. Upon receiving the spindle speed signal, the spindle amplifier 71 rotates the spindle motor 72 at the commanded rotation speed. In addition, the rotational position of the spindle motor 72 is positioned at a predetermined position by an orientation command. The rotation speed of the spindle motor 72 is detected by a position coder 73 as a speed detector.
Feedback is provided via interface 20.

The configuration of the numerical controller described above is the same as the configuration of the conventional numerical controller. The difference is that a processing program for obtaining a smooth curved surface is also stored in the pick feed direction of the present invention stored in the ROM 12. A G code and an auxiliary code for selecting the function mode of the present invention for executing the function of the present invention are provided.
The start of the function mode of the present invention is designated by "G05.1Q5", and the end of this function mode is instructed by "G05.1Q0". An example of a program for executing this function is as follows. G05.1Q5; Start of this function mode X1.234Y2.345Z3.456: Start of first pass X1.345Y2.346Z3.567; ..... X120.234Y2.348Z3.678; Y3.348; End of pass. Pick feed command X120.234Y3.348Z3.655; 2nd pass start X120.113Y3.348Z3.588; ... X1.234Y3.348Z3.455; Y4.348; 2nd pass end, pick feed command ······ G051Q0; End of this function mode In the above program example, the difference from the conventional program is
At the beginning and end of this program, codes “G05.1Q5” and “G05.
1Q0 "is programmed. Further, the numerical controller automatically determines the order of the pass in the same manner as in the related art. As an automatic discrimination method, for example, an angle for discriminating whether or not a point sequence is arranged in a direction almost in contact with each other is set. When the angle between the point strings is equal to or smaller than the set angle, the path is determined to be continuing and the processing is automatically determined. Instead of the automatic discrimination, a conventional method of instructing the number of the pass or the pick feed on a program can also be adopted.

Therefore, in this embodiment, as shown below, paths are commanded from the first to the m-th, and in each path, points are commanded from 1 to ni (i = 1 to m). This will be described below. First pass: P _1,1 , P _1,2 , ..., P _{1, n1} Second pass: P _2,1 , P _2,2 , ..., P _{2, n2} ... .. M-th pass: P _{m, 1} , P _{m, 2} ,... P _{m, nm In} this machining program, as shown in FIG. It is assumed that Then, a program instructing each path in a point sequence is input from the external memory 82 or the like via the interface 15 and stored in the CMOS memory 14, and then the program is executed. The processor 11 outputs “G
When the code of “55.1Q5” is read, FIGS.
The processing shown in is performed.

Firstly, processed shape commanded sequence of points P _1,1 of the first _{pass, P 1,2, P 1,3 ··· P} 1, n1 smooth curve (Bezier curve in the same manner as conventionally, NURBS curve ,
A spline curve is generated and stored (step S1).
Next, the index i is set to "2" and the index j is set to "1" (steps S2 and S3), and the j-th and (j + 1) -th points P _{i, j} and P _{i, j} of the i-th path are set. ₊₁ tangent vector P
_{i, j} ′ and P _{i, j + 1} ′ are obtained (step S4). As described above, if the point for which the tangent vector is to be obtained is an intermediate part of the point sequence, the points P _{i, j-1} and P _i before and after this point P _{i, j} are shown in FIG. _{, j + 1} , an arc passing through the three points is obtained, and a tangent vector of the arc at the point is obtained. If the point for which the tangent vector is to be obtained is the start point or the end point of the path, three points following the point (FIG.
At three points of _{Pi, 1} , _{Pi, 2} , _{Pi, 3} or _{Pi, ni-2} ,
This tangent vector is obtained by obtaining an arc passing through P _{i, ni-1} , P _{i, ni} ) and obtaining a tangent vector of the point of this arc.

If i = 2 and j = 1, the point P _{i, j} = P
_2,1 , P _{i, j + 1} = tangent vector P _{i, j} ′ of P _2,2 =
P _2,1 ′, P _{i, j + 1} ′ = P _2,2 ′ are the points P _2,1 , P _2,2 ,
It is determined from an arc passing through the three points P _2,3 . Next, the midpoint P between the point P _{i, j} (= P _2,1 ) and the point P _{i, j + 1} (= P _2,2 )
c is obtained (step S5), and an adjacent point of the (i-1) th path which is one path before the i-th path which is the path from the midpoint Pc (P _{1 of} the first path when i = 2) _{, 1} , P _1,2 , P _1,3
... _Line segment P _{i-1, k} P _{i-1, k + 1} (k is 1) connecting P _{1, n1}
When the vertical line is dropped from (i.e., changes to n _i-1 -1), it is determined whether or not the foot Qc of the vertical line is on the line segment (step S6). Is not inserted. If there is at least one, the process proceeds to step S7, and the length of the perpendicular | PcQc of the line segments
Is the smallest line segment P _{i-1, k} P _{i-1, k + 1} (k = _{1 to} n _i-1
Select -1). The selected line segment is a line segment _{Pi-1, aPi-1, a + 1} as shown in FIG.

Then, the vectors (P _{i-1, a} , P _{i-1, a + 1} )
And the inner product of the vector (P _{i, j} , P _{i, j + 1} ) is obtained. If the inner product is positive and in the same direction, the start point Qs of the line segment is set to the points P _{i-1, a} ,
The end point Qe is assumed to be _a point Pi _{-1, a + 1} . Conversely, if the inner product is not positive and the direction is the opposite direction, the start point Qs of the line segment is set to the point P
_{i-1, a + 1} , and the end point Qe as a point P _{i-1, a} (step S
8). Since the examples shown in FIG. 1 and FIG. 3 are program examples of the reciprocating path, the directions are opposite and the inner product is not positive, so that the point P _{i-1, a + 1} is the starting point Qs and the point P _{i-1, a} is the end point Qe.

Similarly, adjacent points of the (i + 1) th pass one after the i-th pass from the midpoint Pc (when i = 2, P _3,1 , P _3,2 , P _3,3 ... P _{3, n3} ) and drop a perpendicular line to a line segment P _{i + 1, k} P _{i + 1, k + 1} (k changes from 1 to n _{i + 1} -1). Then, it is determined whether or not the leg Rc of the perpendicular line is on the line segment (step S9). If there is no leg, the process proceeds to step S17, and the insertion processing of the auxiliary point is not performed. If there is at least one, the process proceeds to step S10,
Among the line segments, the line segment P _{i + 1, k} P _{i + 1, k + 1} (k = _{1 to} n _{i + 1} −1) having the smallest perpendicular line length | PcRc | is selected. As shown in FIG. 1, the selected line segment is divided into a line segment P _{i + 1, b} P
_{i + 1 and b + 1} .

Then, the vectors (P _{i + 1, b} , P _{i + 1, b + 1} )
And the vector (P _{i, j} , P _{i, j + 1} ) is obtained. If the inner product is positive and in the same direction, the starting point Rs of the line segment is set to the points P _{i + 1, b} ,
The end point Re is set to points P _{i + 1 and b + 1} . Conversely, if the inner product is not positive and the direction is the opposite direction, the start point Rs of the line segment is set to the point P
_{i + 1, b + 1} , and the end point Re as a point P _{i + 1, b} (step S1
1). Since the examples shown in FIG. 1 and FIG. 3 are the program examples of the reciprocating path, since the direction is reversed and the inner product is not positive, the points _{Pi + 1, b + 1} are the starting point Rs, the points Pi _{+ 1, b} is the end point Re.

Next, the tangent vectors at the start points Qs, Rs, end points Qe, Re of the line segment having the perpendicular legs Qc, Rc lowered from the midpoint Pc obtained in steps S8 and S11 are calculated by the above-described method. Qs', R
s', end points Qe 'and Re' are obtained (step S1).
2). Then, as described above, it passes through the points Qs and Qe based on the points Qs and Qe and the tangent vectors Qs 'and Qe',
g (0) = Qs, g (1) = Qe, a smooth curve (Bézier curve, NURBS curve, spline curve) g
(T) is generated (step S13). Similarly, the point R
s, Re and the tangent vector Rs ', Re'
A smooth curve (Bézier curve, NURBS curve, spline curve) h (t) that passes through s and Re and satisfies h (0) = Rs and h (1) = Re is generated (step S14).

Further, from the points P _{i, j} , P _{i, j + 1} , and the tangent vectors P _{i, j} ′ and P _{i, j +1} ′ of each point, the points P _{i, j} and P _{i , j + 1} , f (0) = P _{i, j} , f (1)
= P _{i, j + 1} (Bezier curve, NURB
An S curve and a spline curve) f (t) are generated (step S15). Then, the obtained smooth curve f (t) between the two points in the i-th pass of the path and the smooth curve between the two points in the (i-1) -th and (i + 1) -th paths before and after the i-th pass are obtained. Based on the simple curves g (t) and h (t), a continuation process for smoothly continuing the curved surface in the pick feed direction is executed. That is, in this embodiment, as described above, the parameters tq and t are calculated by the first and second equations.
r is calculated, and by performing the calculation of the third equation, the smooth curve of the path before and after the i-pass is added, and the curve of the path such that the smooth curve before and after the i-path smoothly continues in the pick feed direction is calculated. In order to obtain, an auxiliary point _PjH is _obtained between two points of the i-pass (step S16).

Next, the index j is incremented by "1" (step S17), and it is determined whether or not the index j is equal to or greater than the score ni of the point sequence of the i-pass (step S18). Returning to step S4, the above-described processing is repeated, and if a perpendicular can be drawn from the midpoint Pc of the line connecting the adjacent points to the line connecting the adjacent points of the preceding and succeeding paths, An auxiliary point P _jH is inserted between them. Thus, when the value of the index j reaches the score ni of the point sequence and the insertion process of the auxiliary point for the i-path is completed, the process proceeds from step S18 to step S19, where each inserted auxiliary point P _kH (k is 1 to ni (Up to -1) is also regarded as a command point, and a smooth curve (Bézier curve, NURBS curve, spline curve) is obtained in the same manner as the conventional method based on a point sequence obtained by adding the auxiliary point P _KH to a point sequence _specified by the program. Generate

Next, the index i is incremented by "1" to determine whether the index i is equal to or greater than the number m of paths set by the program (steps S20 and S21). If not, the flow returns to step S3. S3 and the following processes are performed, and the above-mentioned auxiliary point is inserted into each path. This auxiliary point is also added to the point sequence specified by the program, and the path before and after the path is picked up. Obtain a smooth curve so that it continues smoothly in the feed direction. Then, when the value of the index i reaches the number m of passes specified by the program, a smooth curve is generated in the same manner as in the past based on the point sequence specified as the m-th pass which is the last pass.

Based on the smooth curve thus obtained,
The processor 11 performs an interpolation process, distributes the movement command to each of the X, Y, and Z axes, and controls the axis control circuits 30, 31,
Reference numeral 32 performs feedback control of the position, speed, and current, and drives and controls the servomotors 50, 51, and 52 of the respective axes via the servo amplifiers 40, 41, and 42. In the above-described embodiment, an area between two points in a point sequence on a preceding and succeeding path closest to a machining area between two points in the point sequence of the path is determined, and the determined two points on the preceding and succeeding paths are determined. , And a smooth curve passing through the two points on the path, an auxiliary point _PjH is determined near the midpoint between the two points. Instead of one point, a plurality of auxiliary points such as two points and three points may be obtained.

For example, to obtain two points,
Instead of the intermediate point Pc of the line segment P _{i, j} P _{i, j + 1} connecting the two points,
A line segment that allows a perpendicular line to be drawn from a point that is one-third of the line segment P _{i, j} P _{i, j + 1} and a point that is two-thirds of the path before and after the path is determined. A smooth curve passing through both end points is obtained in the same manner as described above, and the position of each smooth curve corresponding to this foot is determined by the position of the foot with the perpendicular line dropped down, and 1/3, 2 of the smooth curve passing through the corresponding point of the path. / 3 are weighted, and two auxiliary points are inserted between the corresponding points P _{i, j} and P _{i, j + 1 of the} path, and a point sequence obtained by adding the two auxiliary points is used. A smooth curve of the path may be obtained. In the case where there is no line segment from which a perpendicular line can be drawn to a line segment connecting points of 1/3 of the line segment P _{i, j} P _{i, j + 1} and points of 2/3 from the path before and after the path. In this case, as in the above-described embodiment, the merging may be performed such that the perpendicular is lowered from the intermediate point and the intermediate point is inserted.

Further, in the above-described embodiment, all the smooth curves of each path are obtained, and the interpolation processing is executed based on the smooth curve obtained thereafter. May be executed. That is, the interpolation processing may be performed immediately after obtaining the smooth curve in steps S1, S19, and S22.

[0040]

According to the present invention, even if the path is commanded reciprocally, or the path has an inflection point, it is possible to process a curved surface that is smoothly continuous in the pick feed direction.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an operation principle according to an embodiment of the present invention.

FIG. 2 is a main block diagram of the numerical control device of the same embodiment.

FIG. 3 is an example of a machining shape command point sequence instructed by a machining program.

FIG. 4 is a processing flowchart of a function of the present invention in one embodiment of the present invention.

FIG. 5 is a continuation of the flowchart.

FIG. 6 is a continuation of the flowchart.

[Explanation of symbols]

P _i−1 , P _i , P _{i + 1} Path P _{i , j} point Qs, Rs start point Qe, Re end point Pc intermediate point Qc, Rc

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H269 AB05 AB37 BB03 CC02 CC18 EE07 EE13 EE29 GG02 GG08 JJ02 KK03 NN07 QA05 QB17 QC01 QC06 QC07 RB03 RB08 RB11

Claims (3)

[Claims] 1. A numerical control device which reads a program in which a plurality of pick feeds and a sequence of machining shape command points are alternately commanded, determines a smooth curve connecting the sequence of machining shape command points, and interpolates based on the curve. A process shape command point sequence for obtaining a smooth curve and a preceding and subsequent process shape command point sequence with a pick feed interposed between the process shape command point sequence and the smooth shape curve are obtained. Based on the relationship between the machining shape command point sequence to be performed and the preceding and subsequent machining shape command point sequences, an auxiliary point is added between the sequence of machining shape command point sequences for obtaining the smooth curve. A numerical control device for correcting a machining shape command point sequence to which an auxiliary point has been added with a smooth curve. 2. A numerical control device which reads a program in which a plurality of pick feeds and a sequence of machining shape command points are alternately commanded, determines a smooth curve connecting the sequence of machining shape command points, and interpolates based on the curve. From the machining shape command point sequence for which a smooth curve is to be obtained and the preceding and subsequent machining shape command point sequences, the smooth curve is to be obtained so as to obtain a smoothly continuous curved surface in the pick feed direction. A numerical controller characterized by adding an auxiliary point between a sequence of machining shape command points and correcting the machining shape command point sequence to which the auxiliary point is added with a smooth curve. 3. A pick shape is sandwiched between the machining shape command point sequence corresponding to any two adjacent points in the machining shape command point sequence, and two points on the preceding machining shape command point sequence; and A pick feed is interposed between the machining shape command point sequences corresponding to two adjacent points of the machining shape command point sequence, and two points on the subsequent machining shape command point sequence are selected. The numerical control device according to claim 1 or 2, wherein a function that smoothly connects is obtained, and an auxiliary point on the machining shape command point sequence is obtained by the function.