JPH11345017A - Numerical controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a numerical controller shortening the time required for the evaluation of a curvature and accelerating machining. SOLUTION: This numerical controller is provided with a curve input part 21 for inputting a position command by the form of a spline curve, a curvature evaluation part 22 for evaluating the curvature of the spline curve inputted from the curve input part 21 and a speed command generation part 23 for generating a feed speed command based on the curvature evaluated in the curvature evaluation part 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical controller for controlling a machine tool, a robot, and the like.

[0002]

2. Description of the Related Art FIG.
FIG. 2 is a block diagram showing a conventional numerical control device disclosed in Japanese Unexamined Patent Publication No. 2 (Kokai) No. 2; In the figure, reference numeral 41 denotes a command tape on which a command is punched, and reference numeral 42 denotes a tape reader for reading the command tape 41. Reference numeral 43 denotes a pre-processing unit for performing pre-processing of the read data, reference numeral 44 denotes a central processing unit (hereinafter, referred to as a CPU) for executing the arithmetic processing of the numerical control, and reference numeral 45 denotes a memory accessed by the CPU 44. 46 is a pulse distributor that distributes interpolation data as command pulses for each axis of the tool, 47 is a servo control circuit that drives a servomotor based on the command pulses,
48 is the servo motor.

Next, the operation will be described. First, the tape reader 42 reads tool movement data from the command tape 41 on which the command position and command speed are punched. When the read data includes the G code of the interpolation command, the preprocessing unit 43 sets a spline curve based on the commanded point sequence. The CPU 44 calculates the amount of movement per unit time in the tangential direction of the set spline curve, and
The tool trajectory is calculated in accordance with a program for creating interpolation data stored in. The interpolation data created in this way is distributed by the pulse distributor 46 as command pulses for each axis of the tool, and the respective servo control circuits 47
Sent to The servo control circuit 47 controls the servomotor 48 according to the received command pulse, and moves the tool via a ball screw or the like by the rotation of the servomotor 48.

As described above, in the above numerical control device, first, a tangent vector is obtained, a parameter change amount for moving on a spline curve at a constant speed is calculated from the tangent vector, and according to the parameter change amount, The interpolation point on the spline curve is calculated for each pulse distribution cycle, and the spline curve is calculated based on the cubic spline curve. The parameter Δt of the spline curve for moving the spline curve at a constant speed is determined by the movement amount f for each pulse distribution and the tangent vector pt ′.
Was required from.

[0005] In addition, as a document which describes a technique related to such a conventional numerical control device, there is, for example, Japanese Patent Application Laid-Open No. 3-19963. The curve interpolating device disclosed in Japanese Patent Laid-Open Publication No. Hei 3-19963 interpolates a given arbitrary curve with a minute line segment so as to guarantee a desired allowable error. The curvature of the curve at the position is compared with the curvature of the curve near the current position by the search length, and the line segment length is determined from the result of the determination.

Also, "Computer Aided Design", Vol. 19, No. 9 (1
(September 987), pp. 485-498, entitled “Curve and Surface Constructions Useing Rational Bee Splines”
and surface constructions using rational B-spline
s), rationalized B-splines (Non Unifo
The rm Rational B-Spline (NURBS) curve is becoming widely used in computer aided design (CAD).

[0007]

Since the conventional numerical control device is constructed as described above, it is an interpolation system that moves on a spline curve at a constant speed, and the interpolation method moves in the traveling direction (tangential direction of the spline curve). Therefore, smooth acceleration / deceleration control that does not cause vibration of the machine is not considered,
Since smooth acceleration control at the start point and deceleration control at the end point are not performed, smooth mechanical control on the spline curve cannot be performed. Further, since the robot moves on the spline curve at a constant speed, appropriate speed control in accordance with the curvature of the spline curve is not performed, so that mechanical control cannot be smoothly performed on the spline curve and processing accuracy is poor. Further, since the parameter Δt of the spline curve for moving on the spline curve at a constant command speed is obtained from the tangent vector pt ′, not only the calculation time is increased, but also the spline curve of the spline curve obtained for moving at the constant speed command is obtained. The parameter Δt is a tangent vector pt ′
However, the tangent vector pt 'cannot accurately calculate the ratio between the movement amount per pulse distribution period and the parameter change amount of the spline curve, and a calculation error of the parameter Δt occurs where the curvature is large. However, it cannot move on the spline curve exactly at the command speed.
In addition, it is not easy to obtain a tangent vector when performing interpolation of a spline curve. Even when a locus composed of a plurality of spline curves is interpolated, the machine may vibrate in a traveling direction (tangential direction of the spline curve). The problem is that smooth acceleration / deceleration control that does not cause a problem is not considered, and smooth acceleration control at the start point and deceleration control at the end point are not performed, so that mechanical control on the spline curve cannot be performed smoothly. was there.

In the conventional interpolation method, if the search length is set too small, the allowable error is sufficiently guaranteed, but the line segment becomes too small, and the subsequent processing in the linear interpolation part cannot follow up. If the interpolation cannot be performed and the search length is set too large, the allowable error cannot be guaranteed and the setting of the search length becomes troublesome. Also, NUR
When the BS curve is interpolated by the above-described method, there is a problem that it takes a long time to perform calculation and high-speed interpolation control cannot be performed. Further, for a general worker, it is important to guarantee the accuracy but also important to the machining speed. There is a demand for a numerical control device which is an element and can freely select priority between accuracy and speed. However, there has been a problem that such a request cannot be met.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and controls the interpolation speed in accordance with the curvature of a given curve to improve the accuracy after machining and reduce abnormal vibration of a machine tool. It is an object of the present invention to obtain a numerical control device that reduces the amount.

It is another object of the present invention to provide a numerical control device which shortens the time required for evaluating the curvature and realizes high-speed machining.

[0011]

A numerical controller according to the present invention includes a curve input unit for inputting a position command in the form of a spline curve, and a curvature for evaluating the curvature of the spline curve input from the curve input unit. An evaluation unit and a speed command generation unit that generates a feed speed command based on the curvature evaluated by the curvature evaluation unit are provided.

The numerical controller according to the present invention has a function of evaluating a curvature of a spline curve while changing a parameter at a predetermined pitch.

In the numerical controller according to the present invention, the curvature evaluator has a function of converting the spline curve into a plurality of rational Bezet curves and a function of evaluating the curvature of each converted rational Bezet curve. It was done.

In the numerical controller according to the present invention, the curvature estimating unit converts the spline curve into a plurality of rational Bezet curves and the curvature of the spline curve based on control points of the converted rational Bezet curves. And a function to evaluate.

In the numerical control device according to the present invention, the speed command generation unit may be configured to determine a curvature at each point of the given spline curve, an allowable error between the spline curve and the interpolated line segment,
And a function for obtaining the speed of each point from the interpolation unit time, and comparing the obtained speed of each point with a given speed command value, in a section where the given speed command value is smaller, a spline And a function of setting the speed command value to the speed of the curve.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a numerical control device according to Embodiment 1 of the present invention. In the figure, 1 is a locus command P (t) (where t
Is a parameter defining a spline curve (hereinafter abbreviated as a parameter) and a command input unit for inputting a feed speed command Vcom. Each command is input as one block or a plurality of blocks as required, and stored. Also,
The trajectory command P (t) is input in the form of a spline curve.

Reference numeral 2 denotes a speed pattern generation unit including an end point distance calculation unit, a speed command output unit, and an acceleration / deceleration control unit, which will be described later. Reference numeral 3 denotes a distance Le from the current command position to the end point of the spline curve. The end point distance calculation unit 4 controls the feed speed command Vcom so that the distance Le to the end point calculated by the end point distance calculation unit 3 can be moved and stopped, and outputs it as a speed command Vout to be input to the acceleration / deceleration control unit. The speed command output units 5 and 5 are acceleration / deceleration control units that perform acceleration / deceleration control so that the speed command Vout of the speed command output unit 4 changes smoothly. For this acceleration / deceleration control, for example, a trapezoidal acceleration / deceleration control method described in Japanese Patent Application Laid-Open No. 1-237806 or an exponential function acceleration / deceleration control method conventionally used may be used. Here, the trapezoidal acceleration / deceleration control method operates so as to specify acceleration ΔF, perform acceleration / deceleration at the commanded acceleration ΔF, and perform acceleration / deceleration control until the speed reaches the commanded speed. A speed command Vout input to the acceleration / deceleration control unit 5,
The integrated value of the difference between the output speed commands Vs is the following distance Ld
Is stored in the acceleration / deceleration control unit 5. When the input Vout becomes 0, the acceleration / deceleration control unit 5 sends the speed command Vs until the integral value of the output speed Vs of the acceleration / deceleration control unit 5 reaches the following distance Ld. It works to keep outputting. This acceleration / deceleration control unit 5
Is output as a speed command obtained by synthesizing the feed speed of each axis of the servo system.

Reference numeral 6 denotes a parameter calculation unit for calculating a parameter for determining a position on the spline curve corresponding to the speed command Vs of the acceleration / deceleration control unit 5. Reference numeral 7 denotes a parameter from the parameter calculation unit 6 and the command input unit 1. Command position (xk, yk, zk) to servo control system from curve command from
Is a spline curve position calculation unit that calculates.

Next, the operation will be described. Here, FIG.
Is a flowchart showing the flow of the overall processing of the operation. The processing is executed at a constant processing cycle (sampling cycle) ΔTs. These processes are realized by a computer system including a CPU, a memory, an input / output (I / O) interface, and the like. Now, it is assumed that the spline curve P (t) (0 ≦ t ≦ 1) in FIG. 3 is given as a command locus. Ps is the starting point and the coordinates are (xs, ys, zs
), Pe is the end point and the coordinate values are (xe, ye, ze), P
(k-1) is the current command position (position command output to the servo control system one processing cycle before) and the coordinates are (x (k-1), y (k-1)
, Z (k-1)). It is assumed that the spline curve P (t) is expressed, for example, in the form of a B-spline curve shown in the following equation (1).

[0020]

(Equation 1)

Here, BSi, n (t) is a B-spline function, and di is a control point in a three-dimensional space. When the parameter t is determined, the position coordinates on the spline curve are determined from the equation (1). By the way, when the parameter t = 0, P
When s point and t = 1, it is Pe point.

Referring to FIG. 2, in step ST1, it is determined whether or not a trajectory command is read for one block. If the trajectory command has not been read, step ST
2, a trajectory command block expressed in the form of a B-spline curve as in equation (1) and a feed speed command in this block are read. Next, in step ST3, the parameter t = t (k-1) at the current command position P (k-1) (x (k-1), y (k-1), z (k-1)). And Current command position P (k
The distance Le from -1) to the end point Pe is calculated using, for example, the following equation (2).

[0023]

(Equation 2)

Thereafter, in steps ST4 to ST6, the speed command output unit 4 calculates the distance Le to the end point, the following distance Ld (k-1) one processing cycle before the following distance Ld, and the above-mentioned feed speed command Vcom. The speed command Vcom is controlled so as to stop accurately at the end point, and the speed command Vout is output. The speed command Vout is determined under the conditions shown by the following equations (3) to (5).

<Condition 1> If Le−Ld (k−1) ≧ Vcom * ΔTs, Vout = Vcom (3) <Condition 2> 0 <Le−Ld (k−1) <Vcom * If ΔTs, Vout = (Le−Ld (k−1) / ΔTs... (4) <Condition 3> If 0 ≧ Le−Ld (k−1), Vout = 0. ... (5)

That is, in step ST4, the conditions 1 to 3 are determined. Except for condition 1, all deceleration operations are performed. If the condition 1 is satisfied, an operation of YES is performed, and if not, an operation of NO is performed. In step ST5, Vout is calculated as in equation (3).
To determine. In step ST6, the speed command Vout is determined according to the conditions 2 and 3 as shown in the equations (4) and (5). Next, in step ST7, the speed command Vout is subjected to acceleration / deceleration control, and the speed command Vs is calculated and output. As the acceleration / deceleration method, for example, the trapezoidal acceleration / deceleration method described above is used. The following distance L
d is modified by the following equation (6) and used in the next processing cycle.

Ld = Ld (k−1) + (Vout−Vs) * ΔTs (6)

Next, in step ST8, a parameter change amount Δt ′ when the current command position P (k−1) on the spline curve P (t) is changed by a small parameter Δt ′.
And the ratio α of the moving distance ΔP ′. Spline curve P
The coordinates of the current position P (k-1) on (t) are (x (k-1)
, Y (k-1), z (k-1)) and the parameter is t (k-1)
The position P (t (k−1) + Δt ′) at t (k−1) + Δt ′, which has changed by a small parameter Δt ′, can be calculated using the above-described equation (1), and the coordinate value at that time is (x ( k-1) ', y (k
-1) ', z (k-1)'). The ratio α is obtained by the following equation (7).

Α = Δt ′ / ΔP ′ (7)

However, in the above equation (7), the moving distance Δ
P ′ is given by the following equation (8).

[0031]

(Equation 3)

The parameter variation Δt ′ is set to a value that satisfies the following equation (9).

[0033]

(Equation 4)

Next, in step ST9, the parameter change amount Δtk corresponding to the speed command Vs is calculated by the following equation (1).
0).

Δtk = α · Vs * ΔTs (10)

Next, at step ST10, the spline curve P (t) is calculated using the estimated parameter variation Δtk.
The upper position P (t (k-1) +. DELTA.tk) is calculated using equation (1). The coordinate calculation value of P (t (k-1) + Δtk) is output to the servo control system as a command position. Then step ST
At 11, the coordinates of the position P (t (k-1) +. DELTA.tk) are calculated as x (k-1) = xk, y (k-1) = yk and z (k-
1) As = zk, these are stored as the current command positions in the next processing cycle.

When the curvature of the spline curve is small, the same effect can be obtained by obtaining α from the tangent vector.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing a numerical control device according to Embodiment 2 of the present invention. In the figure, 1 to 5 and 7 have the same configurations as those of the first embodiment, and therefore the description thereof is omitted. 8 is 1
The movement amount calculation unit calculates the movement amount ΔP (k-1) of the command position during one processing cycle obtained from the command position before the processing cycle and the command position two processing cycles before. Reference numeral 9 denotes a movement amount ΔP (k−1) of the command position and a parameter change amount Δt (k−1) output one processing cycle ago (a parameter change amount Δtk before one processing cycle).
, The ratio α between the parameter change amount and the movement amount is calculated, and the parameter t is calculated from the speed command Vs of the acceleration / deceleration control unit 5 and the ratio α, and the parameter t (k−1) one processing cycle before.
This is a parameter calculation unit different from that of the first embodiment, which is denoted by reference numeral 6 in FIG.

Next, the operation will be described. Here, FIG.
Is a flowchart showing the flow of the operation, in step S
Since T1 to ST7 and steps ST8 to ST11 perform the same processing as that of FIG. 2, their description is omitted. At step ST20, the command position (x (k-1), y (k-1), z (k-1)) to the servo system in the previous processing cycle and the command position (x (k-2),
y (k-2), z (k-2)), the moving amount ΔP (k-1) is obtained by the following equation (11).

[0040]

(Equation 5)

Next, in step ST21, the parameter calculator 9 sets the parameter change amount Δ
t (k-1) and the movement amount ΔP (k-1) of the command position during one processing cycle
Then, the ratio α between the parameter change amount and the movement amount is calculated by the following equation (12).

Α = Δt (k−1) / ΔP (k−1) (12)

In this method, the ratio α between the parameter change amount and the movement amount at the start point of the spline curve cannot be obtained because the parameter change amounts Δt (k−1) and ΔP (k−1) do not exist. Therefore, in order to obtain the ratio α at the starting point, as shown in equation (7) of the first embodiment, the amount of movement ΔP ′ when the minute parameter Δt ′ is changed is obtained, and the ratio α
Is used.

Further, in the above embodiment, the ratio α between the parameter change amount and the movement amount is calculated using the parameter change amount Δt (k−1) and the movement amount ΔP (k−1) one processing cycle before. But,
The calculation may be performed using the parameter change amount and the movement amount before several processing cycles.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing a numerical control device according to Embodiment 3 of the present invention. In the figure, 1 to 7 have the same configurations as those of the first embodiment, and therefore the description thereof is omitted. Numeral 10 determines whether the parameters obtained by the parameter calculator 6 are valid, and if not, corrects the parameters, and corrects the position command to the servo control system obtained by the spline curve position calculator 7. This is a parameter correction unit.

Next, the operation will be described. Here, FIG.
Is a flowchart showing the flow of the operation, in step S
In T1 to ST9 and ST11, the same processing as that in FIG. 2 is performed, and the description thereof is omitted. In step ST30, similarly to step ST10 in FIG. 2, the position P (t (k-1) + Δtk) on the spline curve is calculated using equation (1) using the parameter change amount Δtk obtained in step ST9. The coordinate values (xk, yk, zk) are obtained. Next, in step ST31, the acceleration / deceleration control unit 5
Amount V during one processing cycle of command speed Vs output from
s * ΔTs, the command positions (x (k−1), y (k−1), z (k−1)) calculated in the previous processing cycle and the command positions (xk, yk, zk) and the difference β from the movement amount ΔPk of the command position during one processing cycle is determined by the following equation (13).

Β = Vs * ΔTs−ΔPk (13)

Here, the difference β of the movement amount is a value corresponding to the speed error, and is caused by a calculation error of the parameter change amount Δtk. The movement amount ΔPk is obtained by the following equation (14).

[0049]

(Equation 6)

Next, at step ST32, the difference β of the movement amount
Is determined to be less than or equal to the allowable value. If difference β is equal to or smaller than the allowable value, the process proceeds to step ST34; otherwise, the process proceeds to step ST33. The allowable value is a value determined from the maximum acceleration and the like that can be allowed by the servo control system. In step ST34, the command position (xk, yk, zk) obtained in step ST31 is output as a position command for the servo system. On the other hand, in step ST34, the parameter change amount Δtk is corrected. For example, the following equation (1
Correct using 5).

Δtk = (Vs * ΔTs / ΔPk) * Δtk (15)

The parameter variation Δtk corrected here
, The position on the spline curve is calculated again in step ST30, and the parameter change amount Δtk, that is, the difference β
Are repeated until the value becomes equal to or less than the specified value.

When the parameter correction method according to the present embodiment is used in combination with the parameter calculation method according to the second embodiment, a parameter corresponding to a speed command can be easily and accurately obtained.

Embodiment 4 Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram showing a numerical controller according to Embodiment 4 of the present invention. In the figure, 1 to 5 and 7 are the same as those of the first embodiment, and the description thereof is omitted. Reference numeral 11 denotes a parameter conversion unit different from that of the first embodiment, which is denoted by reference numeral 6 in FIG. 1 in that a determination as to whether or not to reduce the speed command is output to a connection state determination unit described later. 12, when the trajectory command is represented by a plurality of spline curves, it is determined whether or not the connection state between the spline curves is continuously connected. If it is determined that the connection state is continuous, the spline curve is determined. This is a connection state determination unit that changes the position of the end point. The determination as to whether or not the connection state is continuous by the connection state determination unit 12 can be made based on, for example, the direction and length of the tangent vector at the connection point. When the trajectory command is B
When represented by a spline curve, it can be determined from the positional relationship between control points representing the B-spline curve near the connection point.

Next, the operation will be described. Here, FIG.
Is a flowchart showing the flow of the operation, in step S
In T1 to ST11, processes equivalent to those in FIG. 2 of the first embodiment are performed, and therefore description thereof is omitted. now,
As shown in FIGS. 10 and 11, it is assumed that the trajectory command is represented by two B-spline curves P1 (t) and P2 (t). P1s
Is the start point of P1 (t), P1e (t) is the end point of P1 (t), and P2s is P
The start point of 2 (t), P2e is the end point of P2 (t), and P1e and P2s
Are consistent. The trajectory command shown in FIGS. 10 and 11 is started from P1s, and moves at the speed command Vcom.
Stop at The points Pa and Pb are command positions on P1 (t), Pa is when the distance to the end point P1e of the spline curve P1 (t) is sufficient for deceleration control, and Pb is the spline curve P1. This is the case where the distance to the end point P1e in (t) is not sufficient for deceleration control.

For example, if the current command position is Pa, the distance between the current command position Pa and P1e is calculated in step ST3, it is determined in step ST4 that no deceleration operation is necessary, and the process proceeds to step ST5. Flows. But,
When the current command position has reached a position such as Pb, if it is determined in step ST4 that a deceleration operation is necessary, the process proceeds to step ST40, and it is determined whether or not there is a next trajectory command. If the next trajectory command does not exist, the process proceeds to step ST6, and if there is, the process proceeds to step ST41. In step ST41, it is determined whether the next trajectory command (P2 (t) in FIGS. 10 and 11) is continuously connected to the currently moving trajectory command (P1 (t) in FIGS. 10 and 11). The connection state determination unit 12 determines. if,
If it is determined that the connection is continuous as shown in FIG. 10, the process proceeds to step ST42. If it is determined that the connection is not continuous as shown in FIG. 11, the speed is reduced at the end point P1e of P1 (t).
The process of step ST6 is performed so as to stop. In step ST42, since the connection points are continuous, the end point is set as the end point P2e of the next trajectory command P2 (t), and in step ST3, the distance Le to the end point is calculated again by the following equation (16). Move on to processing.

[0057]

(Equation 7)

However, the coordinates of the current command position Pb are (xb, yb, zb), and the coordinates of P2e are (x2e, y2e,
z2e).

As described above, the connection state of the trajectory command of the spline curve is determined, the position of the end point is changed, and the speed control is performed. Therefore, even when the trajectory command is expressed by a plurality of spline curves, smooth interpolation control is performed. It can be performed.

Embodiment 5 FIG. Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a block diagram showing a configuration of a numerical controller according to Embodiment 5 of the present invention. In the figure, reference numeral 21 denotes a curve input unit for inputting a NURBS spline curve. The format is G code, IGES (Initial Graphics Exchange Specification; Initial)
An exchange format such as Graphics Exchange Specifcation may be used as an input format, and the curve input unit 21 stores curve data to be stored inside the numerical controller. Reference numeral 22 denotes a curvature evaluator for evaluating the curvature of the spline curve input from the curve input unit 21 and storing the result as internal data. Reference numeral 23 denotes curve data of the input spline curve, a curvature evaluator 22.
Is a speed command generation unit that generates a feed speed command at each position on the curve based on the curvature evaluation data evaluated in step (1) and the given speed command value. 24 corresponds to the value of the feed speed command generated by the speed command generator 23,
An acceleration / deceleration control and interpolation unit that calculates the number of pulses for each axis.

Next, the operation will be described. Here, FIG.
3 is a flowchart showing the entire operation flow of the numerical control device. First, in step ST51, N
Convert a URBS curve into a plurality of rational Besee curves. Next, in step ST52, the range of curvature of each rational Besee curve is calculated. And finally, step ST
At 53, the feed speed in each rational Bethey curve is set. Thereafter, the respective steps ST51 to ST53
Is described in detail.

Here, the NURBS curve is generally represented by the following equation (17).

[0063]

(Equation 8)

Note that also in this equation (17), BSi,
n (t) is a B-spline function, di is a control point in a three-dimensional space, and wi is a weight. By changing the control points di and the weights wi, the curve shape can be changed. On the other hand, the curvature k of the curve is expressed by the following equation (18).

[0065]

(Equation 9)

Here, P ′ in equation (18) is N
A first derivative of equation (17) showing the URBS curve,
P ″ is also the second derivative.

Assume that a NURBS curve as shown in FIG. 14 is given. Symbols A to H in the figure each indicate a position on the curve. FIG. 15 shows a change in the curvature of the NURBS curve shown in FIG. This figure 1
In FIG. 5, the parameter is plotted on the horizontal axis and the curvature is plotted on the vertical axis.
It shows how the curvature changes corresponding to each point from to the point H, and the feed speed is set based on that.

FIG. 16 is a flowchart showing an example of a processing procedure in the curvature evaluator 22. First, the value of the parameter t is initialized in step ST61, and then the curvature k is calculated in step ST62. It is determined in step ST63 whether or not the obtained curvature k can be sent at the given command speed Fs, and a parameter section that requires interpolation and cannot be interpolated at the given command speed is registered. Hereinafter, while the parameter t is incremented by a predetermined pitch Δt in step ST65, steps ST62 to ST62 are repeated until it is detected in step ST66 that the parameter t has exceeded its maximum value.
The process of ST66 is repeated.

As a result, in the example shown in FIG. 15, BC, DE, F
G is the parameter tb to tc, td to te,
It will be registered from tf to tg.
The disadvantages of this method are that the curvature may not be able to be evaluated depending on the pitch at which the parameter is incremented, and that the number of points from the minimum value to the maximum value of the parameter must be examined. It takes time.

FIG. 17 is a flowchart showing another example of the processing means in the curvature evaluator 22.
The NURBS curve is converted into a plurality of rational Bethey curves, and a range in which the curvature can be obtained in each rational Bethey curve is calculated. This method will be described in detail. Generally, a rational Bethey curve is expressed as in the following equation (19).

[0071]

(Equation 10)

On the other hand, the curvature k of the curve is calculated by the equation (1) as described above.
Although expressed by 8), by substituting equation (19), the curvature of this rational Bethey curve can be transformed into the following equation (20).

[0073]

[Equation 11]

All the expressions surrounded by the absolute value symbols in the expression (20) can be expressed by the Beze expression, and the following expression (2)
It can be expressed as 1).

[0075]

(Equation 12)

Incidentally, the expression expressed by the Besee equation has a convex hull property. FIG. 18 is an explanatory diagram for explaining the convex closure property. Suppose that the control points of the Besee curve are represented by Q0 to Q6 as shown in FIG. At this time, the property that the curve CV always exists in the convex body V1 formed by the control points Q0 to Q6 is called convex hull. If this property is used, it is possible to know the range of the absolute value of the curve CV. Therefore, if this property is used, the range of the curvature k can be known by using the fact that each of A, B, and C in the equation (21) is a Bethey equation. . That is, the following equation (2)
2) kmin and kmax can be obtained.

Kmin ≦ k ≦ kmax (22)

Here, the curvature k of the kmin and kmax
Can be obtained smaller and larger than the minimum value and the maximum value, respectively, but can be said to be useful characteristic values for knowing the global nature of the curve. As described above, the curvature characteristic value k
Since min and kmax can be obtained only from the control points, there is an advantage that the calculation is faster as compared with the above method.

Next, a speed command is generated by a speed command generator 23 based on the processing result of the curvature evaluator 22. FIG. 19 is a flowchart illustrating a processing procedure of the speed command generation unit 23. First, in step ST81, tolerance τ,
The maximum speed Fmax is determined from kmax and the sample time ΔT. As shown in FIG. 20, the relationship between the curvature k, the tolerance τ, and the interpolated line segment length Δl can be expressed by the following equation (23).

[0080]

(Equation 13)

Therefore, assuming that the sampling time is ΔT, the maximum value Fmax of the speed required to guarantee the tolerance τ can be obtained by the following equation (24).

[0082]

[Equation 14]

In the next step ST82, the speed is compared with the given speed command value Fs, and the steps ST83 and ST8 are performed.
In step 4, a small value is selected to determine the actual feed speed F. FIG. 21 is an explanatory diagram showing an example of the speed command thus obtained. In the section AB, the section CD, the section EF, and the section GH, the given command speed Fs is taken, the section F is taken in the section BC and the section FG, and the speed F2 is taken in the section DE. As described above, the speed command generator 23 obtains the section indicated as the parameter range and the traveling speed in that section.

FIG. 22 is an explanatory diagram for explaining the processing of the acceleration / deceleration control and the interpolation unit 24 based on the obtained speed command. The acceleration / deceleration control / interpolation unit 24 generates pulses to be actually sent to the servo system based on the command speed pattern so as not to exceed the given acceleration. The input data to the acceleration / deceleration control and interpolation unit 24 are the section of the curve and the command speed, the command speed before and after, and the allowable acceleration. When the speed in the section is higher than the speed in the preceding section, acceleration control is performed within a range not exceeding a predetermined acceleration. If the speed in that section is higher than the speed in the subsequent section, deceleration control is performed within a range not exceeding a predetermined acceleration. In this deceleration control, speed reduction processing is performed while checking the distance between the point and the current point each time so as to reach the section end point.

Embodiment 6 FIG. Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 23 is a block diagram showing a numerical control device according to Embodiment 6 of the present invention.
In the figure, reference numeral 21 denotes a curve input unit equivalent to the one designated by the same reference numeral in FIG. 12 to receive and input a position command value in the form of a NURBS curve. Reference numeral 25 denotes a curve conversion unit for converting the NURBS curve input from the curve input unit 21 into a plurality of rational Bezer curves, and reference numeral 26 denotes a rational Bezer curve for interpolating each rational Bezer curve converted by the curve converter 25. This is a curve interpolation unit.

Next, the operation will be described. Here, FIG.
FIG. 4 is a flowchart showing a flow of processing of the numerical control device according to the sixth embodiment. First, the curve conversion unit 25
In step ST91, the NURBS curve to be interpolated, which has been input from the curve input unit 21, is once converted into a plurality of rational Besee curves, and is output to the rational Besee curve interpolator 26. The rational Besee curve interpolating unit 26 having received it sets the ratio i of the rational Besee curve to the initial value 1 in step ST92, and then executes the interpolation process of the i-th rational Besee curve in step ST93. Hereinafter, step ST
While incrementing i by 1 at step 94, step S
Until it is detected at T95 that the i has become equal to the number of rational Besee curves sent from the curve conversion unit 21,
Steps ST93 to ST95 are repeated. In this way, the plurality of rational Besee curves converted from the NURBS curve by the curve conversion unit 25 are sequentially subjected to the interpolation process, and a series of processes ends when the interpolation process of all the rational Besee curves is completed.

Here, the NURBS curve is expressed by control points and knot vectors, and the rational Bethey curve is expressed only by control points. In the case of a cubic equation, the NURBS curve is converted into a plurality of rational Bethey curves as follows. That is, the control point (vertex coordinate value) of the NURBS curve
Are d0, d1,... DL + 2, and weights are w0, w1,.
... WL + 2, the knot vector is given by u0, u1,... UL, and when Δ0 to ΔL are defined as Δi = ui + 1−ui, the plurality of rational Bethey curves are i = 1 to L−
1 is expressed as in the following equation (25).

[0088]

(Equation 15)

Here, b3i, b in the above equation (25)
3i-1 and b3i-2 are the control points of the rational Bethey curve, and v3i, v3i-1 and v3i-2 are the weights of the rational Bethey curves and are given by the following equation (26).

[0090]

(Equation 16)

Note that Δ in the above equation (26) is Δ = Δi−2
+ Δi-1 + Δi. In the case of i = 0 and i = L, that is, the first and last are represented by the following Expressions (27) and (28).

[0092]

[Equation 17]

(Equation 18)

In these equations (27) and (28), v
0, v1, v2 and v3L-2, v3L-1, v3L are represented by the following equations (29) and (30).

[0094]

[Equation 19]

(Equation 20)

Such a conversion is performed as shown in FIG.
The control points d0 to d5 of the NURBS curve are converted into the control points b0 to b9 of the rational Besee curve, and b0 to b3
, B3 to b6, and b6 to b9 become three rational Bethey curves CV1, CV2, and CV3 shown in FIG.

After such a conversion is performed, the numerical controller according to the sixth embodiment includes the rational Bezier curve interpolation unit 26 having a function of interpolating the rational Bezey curve. The same effect as the direct interpolation control can be obtained. Note that the interpolation by the rational Besee curve interpolating unit 26 can be realized by the method described in the description of the fifth embodiment. Thus NURBS
Since the curve is converted into a rational Bezier curve and interpolated, there is no need to calculate a heavy NURBS curve, and a numerical control device capable of performing NURBS interpolation at high speed can be realized.

It goes without saying that Embodiment 6 is also applied to a NURBS curve.

Embodiment 7 FIG. Next, a seventh embodiment of the present invention will be described with reference to the drawings. FIG. 27 is a block diagram showing a numerical control apparatus according to Embodiment 7 of the present invention.
In the figure, reference numeral 27 denotes NURBS when a linear command, an arc command, an elliptical command, or the like using a conventionally used G code is input.
This is a command conversion unit that converts the data into a curve format and inputs the converted data to the curvature evaluation unit 22. The other parts are denoted by the same reference numerals as the corresponding parts in FIG. 12, and the description thereof is omitted.

Next, the operation will be described. When the position command data is input in the form of a NURBS curve, the data is received by the curve input unit 21 and input to the curvature evaluator 22. On the other hand, when a position command is input as a linear command, an arc command, an elliptical command, or the like using a conventionally used G code, the command is input to the command conversion unit 27 and the data of the position command is converted into a NURBS curve. And then input to the curvature evaluator 22. Subsequent processing proceeds in the same manner as described in the fifth embodiment, and a description thereof will not be repeated. This makes it possible to maintain compatibility with existing NC codes such as G codes, and also to unify internal processing.

Embodiment 8 FIG. Next, an eighth embodiment of the present invention will be described with reference to the drawings. FIG. 28 is a block diagram showing a numerical controller according to Embodiment 8 of the present invention.
In the figure, reference numeral 31 denotes a selection information input unit for inputting selection information for instructing whether to perform interpolation processing with speed priority or accuracy priority. Reference numeral 32 denotes a case where selection information designating speed priority is input. A speed priority selection unit for selecting interpolation control such that the amount of movement per unit time is constant; a precision priority selection unit for selecting interpolation control for guaranteeing tolerance when selection information for designating accuracy priority is input; Department.
Reference numeral 34 denotes a curve interpolating unit that executes a spline curve interpolation process in accordance with the interpolation control selected by the speed priority selecting unit 32 or the accuracy priority selecting unit 33.

Next, the operation will be described. Here, FIG.
9 is a flowchart showing the flow of the overall operation of the numerical controller according to the eighth embodiment, FIG. 30 is a flowchart showing the procedure of the spline interpolation process, and FIG. 31 is an explanatory diagram showing an example of the language input. The G code “G9.0” of sequence number 004 shown in FIG. 31 is a precision priority code as selection information for instructing the precision priority mode, and the G code “G9.
“1” is a speed priority code as selection information for instructing the speed priority mode, ie, enters the precision priority mode after “G9.0” of sequence number 004, and enters the speed priority mode after “G9.1” of sequence number 010. Enter priority mode.If nothing is set, priority is given to precision by default.

As shown in FIG. 29, when the processing is started, in step ST101, the program is first read line by line. Next, it is determined in step ST102 whether or not the read code is a speed priority code, and in step ST103 whether or not the read code is an accuracy priority code. If the read code is a speed priority code, the internal variable cnt1 is set to “0” in step ST104. If it is an accuracy priority code, the internal variable cnt1 is set to "1" in step ST105. If neither of the above is true, it is determined in step ST106 whether or not it is a spline interpolation code. If not, normal code processing is executed in step ST107, and the spline interpolation code is used. If there is, spline interpolation processing is executed in step ST108.

When the spline interpolation process is started, first, in step ST111 in FIG. 30, the internal variable cnt
It is determined whether 1 is “0”. as a result,
If the internal variable cnt1 is “0”, step ST112
Then, the speed priority selection unit 32 selects speed-priority interpolation control so that the moving amount per unit time is constant, and the curve interpolation unit 34 executes speed-priority spline curve interpolation processing based on the selection. On the other hand, if the internal variable cnt1 is “1”, in step ST113, the interpolation control for guaranteeing the tolerance is selected by the accuracy priority selection unit 33, and the curve interpolation unit 34 executes the interpolation process of the spline curve by giving priority to the accuracy based on the selection. I do.

Note that a specific method of interpolation processing with priority on accuracy can be realized by the method described in the first embodiment. Further, the interpolation process with priority on speed can be realized by obtaining a distance to be moved per unit time, obtaining an increment value of a parameter corresponding to the distance, and outputting a position command value.

As described above, according to the numerical controller of the eighth embodiment, the input selection information for instructing the speed priority mode and the selection information for instructing the precision priority mode are based on the input selection information.
The operator can select the type of the spline curve interpolation processing.

[0106]

As described above, according to the present invention, a curvature estimating section for evaluating the curvature of a spline curve input from a curve input section, and a feed based on the curvature evaluated by the curvature estimating section. And a speed command generation unit that generates a speed command, so that a feed speed command is generated based on the evaluation result of the curvature of the input spline curve, and the interpolation speed is determined by the degree of curvature of the given curve. It is possible to improve the accuracy after processing by being controlled, and it is also possible to prevent unreasonable acceleration / deceleration, thereby providing an effect that abnormal vibration of the machine tool can be reduced.

According to the present invention, the curve evaluator is configured to have a function of evaluating the curvature of the spline curve while changing the parameter at a predetermined pitch, so that the curvature can be easily evaluated and the speed of machining can be increased. This has the effect of realizing the conversion.

According to the present invention, the curvature estimating unit is configured to have a function of converting a spline curve into a plurality of rational Bezier curves and a function of evaluating the curvature of each converted Bezier curve. Since the spline curve can be converted into a plurality of rational Bezier curves and the curvature can be evaluated for each of them, the processing time required for the curvature evaluation can be reduced and the speed of machining can be increased.

According to the present invention, the curvature estimating unit has a function of converting a spline curve into a plurality of rational Bezier curves and a function of evaluating the curvature of the spline curve based on the control points of each converted Bezier curve. With such a configuration, it is possible to further reduce the processing time required for the evaluation of the curvature, and it is possible to increase the speed of machining.

A speed command generation unit for calculating a curvature at each point of the given spline curve, an allowable error between the spline curve and the interpolated line segment, and a speed of each point from the interpolation unit time; The obtained speed of each point is compared with a given speed command value, and in a section where the given speed command value is smaller, a function of setting the speed command value to the speed on the spline is provided. As a result, the traveling speed in each section indicated as the parameter range can be set appropriately, and the effect of achieving higher precision in machining can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a numerical control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of an operation of the embodiment.

FIG. 3 is an explanatory diagram showing an example of a spline curve in the embodiment.

FIG. 4 is a block diagram showing a numerical control device according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of the operation of the embodiment.

FIG. 6 is a block diagram showing a numerical control device according to a third embodiment of the present invention.

FIG. 7 is a flowchart showing a flow of the operation of the embodiment.

FIG. 8 is a block diagram showing a numerical controller according to Embodiment 4 of the present invention.

FIG. 9 is a flowchart showing a flow of the operation of the embodiment.

FIG. 10 is an explanatory diagram showing an example of a spline curve in the embodiment.

FIG. 11 is an explanatory diagram showing another example of a spline curve in the embodiment.

FIG. 12 is a block diagram showing a numerical control device according to a fifth embodiment of the present invention.

FIG. 13 is a flowchart showing a flow of an overall operation of the embodiment.

FIG. 14 is an explanatory diagram showing an example of a NURBS curve in the embodiment.

FIG. 15 is an explanatory diagram showing a change in curvature of the NURBS curve.

FIG. 16 is a flowchart illustrating an example of an operation of the curvature evaluation unit according to the embodiment.

FIG. 17 is a flowchart showing another example of the operation of the curvature evaluation unit.

FIG. 18 is an explanatory diagram for describing the convex hull property of a rational Bethey curve in the above embodiment.

FIG. 19 is a flowchart showing a flow of an operation of a speed command generator according to the embodiment.

FIG. 20 is an explanatory diagram showing a relationship between a curvature, a tolerance, and an interpolation line segment length.

FIG. 21 is an explanatory diagram illustrating an example of a speed command generated by a speed command generator according to the above embodiment.

FIG. 22 is an explanatory diagram for explaining an operation based on the speed command in the acceleration / deceleration control and interpolation unit of the embodiment.

FIG. 23 is a block diagram showing a numerical controller according to Embodiment 6 of the present invention.

FIG. 24 is a flowchart showing a flow of the operation of the embodiment.

FIG. 25 is an explanatory diagram showing a conversion from a NURBS curve to a rational Besee curve in the embodiment.

FIG. 26 is an explanatory diagram showing the converted rational Besee curve.

FIG. 27 is a block diagram showing a numerical control device according to Embodiment 7 of the present invention.

FIG. 28 is a block diagram showing a numerical controller according to Embodiment 8 of the present invention.

FIG. 29 is a flowchart showing the flow of the overall operation of the embodiment.

FIG. 30 is a flowchart showing a flow of a spline interpolation process according to the embodiment.

FIG. 31 is an explanatory diagram showing an example of language input according to the embodiment.

FIG. 32 is a block diagram showing a conventional numerical control device.

[Explanation of symbols]

21 Curve input unit, 22 Curvature evaluation unit, 23 Speed command generation unit

Claims (5)

[Claims] 1. A curve input unit for inputting a position command in the form of a spline curve, a curvature evaluation unit for evaluating a curvature of a spline curve input from the curve input unit, and a curvature evaluated by the curvature evaluation unit And a speed command generation unit for generating a feed speed command based on the command. 2. The numerical controller according to claim 1, wherein the curvature evaluator has a function of evaluating the curvature of the spline curve while changing parameters at a predetermined pitch. 3. The method according to claim 1, wherein the curvature estimating unit has a function of converting the spline curve into a plurality of rational Bezier curves and a function of evaluating the curvature of each converted Bezier curve. Numerical control device as described. 4. A curvature estimating unit having a function of converting a spline curve into a plurality of rational Bezier curves and a function of evaluating a curvature of a spline curve based on control points of the converted rational Bezey curves. The numerical control device according to claim 1, wherein: 5. A function of a speed command generator for calculating a curvature at each point of a given spline curve, a permissible error between the spline curve and the interpolated line segment, and a speed of each point from an interpolation unit time. Has a function of comparing the obtained speed of each point with a given speed command value and setting the speed command value to a speed on a spline curve in a section where the given speed command value is smaller. 2. The method according to claim 1, wherein
Numerical control apparatus as described in.