JP3068989B2 - 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 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 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. Although the parameter Δt is obtained from the tangent vector pt ′, the tangent vector pt ′ cannot accurately obtain the ratio between the movement amount per one pulse distribution cycle and the parameter change amount of the spline curve, and the parameter Δt is used when the curvature is large. Causes a calculation error of the parameter Δt, and cannot move accurately on the spline curve at the command speed. In addition, it is not easy to obtain a tangent vector when performing interpolation of a spline curve, and when interpolating a trajectory composed of a plurality of spline curves, the machine may vibrate in the traveling direction (tangential direction of the spline curve). Smooth acceleration / deceleration control that does not cause a problem is not taken into account, 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. There was a point.

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 interpolation becomes impossible and the search length is set too large, an allowable error cannot be guaranteed, and the setting of the search length becomes troublesome. NU
When the RBS curve is interpolated by the above-described method, there is a problem that it takes a long calculation time and high-speed interpolation control cannot be performed. Further, for a general worker, accuracy assurance is important, but assurance of machining speed is also important. A numerical control device that can freely select the priority between accuracy and speed is desired, but it has not been able to respond to such a request.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can perform speed control in consideration of acceleration / deceleration control such as acceleration control at a start point and deceleration control at an end point. It can be driven smoothly, has a simple calculation method to calculate the parameters of the spline curve corresponding to the commanded speed, and further has a method of accurately calculating the parameters of the spline curve corresponding to the commanded speed. A locus composed of a spline curve can be smoothly driven on the spline curve in consideration of acceleration / deceleration control. If the spline curve is not smoothly connected, the speed of deceleration control or stop at the connection point is determined. An object is to obtain a numerical control device capable of performing control.

[0010]

According to the present invention, there is provided a numerical controller for inputting a command locus in the form of a spline curve.
Command input unit, and the sprout output from the command input unit.
From the current command position on the in-curve and the line segment length of one or more line segments connecting the end point or in the spline curve
And the end point distance calculator you distance was calculated output provided Te,
Distance to the end point output from the end point distance calculation unit
Speed command output unit you work without an output feed speed instruction in accordance with the
Speed command output from the speed command output unit
An acceleration / deceleration control unit that controls the speed and outputs a smooth speed command;
Before corresponding to the speed command output from the acceleration / deceleration control unit
Using the parameter variation of the serial spline curve, a parameter calculator you parameter calculation outputs of the scan <br/> spline curve, the scan output from the parameter calculator
The spline curve using the parameters of the spline curve
It is obtained so as to include a spline curve position calculation unit for calculating a next command position location on.

Further, the numerical control apparatus according to the present invention, prior to
Parameter change amount of the serial parameter calculation unit includes at least processing cycle before parameter variation, at least one processing
It is obtained by the so that to calculate using the ratio of the movement amount calculated from the period before the command position.

Further, the numerical control device according to the present invention includes a
Command input section to input command locus in the form of spline curve
And the spline curve output from the command input unit
From the current command position above to the end point of the spline curve
Given as the length of one or more segments connecting
An end point distance calculation unit for calculating and outputting a distance to be output, and the end point
According to the distance to the end point output from the distance calculation unit
A speed command output unit for creating and outputting a feed speed command,
Acceleration / deceleration control of the speed command output from the speed command output section
An acceleration / deceleration control unit for outputting a smooth speed command;
The above-mentioned sprag corresponding to the speed command output from the speed control unit.
Using the parameter variation of the in-curve, the spline
Parameter calculator that calculates and outputs curve parameters
And the splice output from the parameter calculation unit.
On the spline curve using the parameters of the
Spline curve position calculation to calculate the next command position in
Unit and speed command output from the acceleration / deceleration control unit
Distance and spline curve at least one processing cycle before
Compare the travel distance calculated from the command position above,
A parameter correction unit that corrects the amount of parameter change is provided.
It is something that can be obtained.

Further, the numerical control device according to the present invention includes a finger
Command input to input command trajectory in the form of multiple spline curves
And power unit, the connection state determining unit for determining the continuity of the connection points of the spline curve of the multiple, in the connection state determining unit
Before and after the spline curve is judged to be connected to the continuous case, the current command position on the spline curve
Connecting the end point or in the spline curve of the rear portion 1
And the end point distance calculating unit for calculating a distance given as a line segment length of One or more segments, the output from the end point distance calculation unit
The speed command is created and output according to the distance to the end point
Output from the speed command output unit
Acceleration / deceleration control of the speed command to output a smooth speed command
Output from the acceleration / deceleration control unit
Parameter change of the spline curve corresponding to the speed command
Calculate the parameters of the spline curve using
A parameter calculation unit for outputting and outputting, and the parameter calculation unit
Using the parameters of the spline curve output from
To calculate the next command position on the spline curve
And a spline curve position calculation unit that performs the calculation .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG . 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 controller according to Embodiment 1 of the present invention . In the figure, 1 is a trajectory command P
(t) (where t is a parameter defining a spline curve, abbreviated as a parameter hereinafter) and a feed speed command Vcom
Is a command input unit for inputting the Each command is input as one block or a plurality of blocks as required, and stored. 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.

[0016] 6 is a parameter calculation unit for calculating a parameter for determining the position on the spline curve corresponding to the speed command Vs of deceleration controller 5, 7 parameters and command input section from the parameter calculation part 6 of Yoko Command position (xk, yk, zk) to servo control system from curve command from 1
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).

[0018]

(Equation 1)

[0019] Here, BS i, _{n (t)} is a B-spline function, d _i is the control point of the 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.

In 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).

[0021]

(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 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, the parameter change amount Δt ′ when the current command position P (k−1) on the spline curve P (t) is changed by the minute 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).

[0029]

(Equation 3)

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

[0031]

(Equation 4)

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

Δtk = α · Vs * ΔTs (10)

Next, in 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 FIG. 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 are
Since the configuration is the same as that of the first embodiment, the description is omitted. Reference numeral 8 denotes a movement amount calculation unit for calculating the movement amount ΔP (k-1) of the command position during one processing cycle obtained from the command position one processing cycle ago and the command position two processing cycles ago.
9 is the movement amount ΔP (k−1) of the command position and the parameter change amount Δt (k−1) output one processing cycle ago (one processing cycle ago).
From the parameter change amount Δtk), a ratio α between the parameter change amount and the movement amount is calculated, and a parameter 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. 1 in that tk is obtained.

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).

[0038]

(Equation 5)

Next, in step ST21, the parameter calculator 9 calculates 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 is changed by the parameter change.
Since there are no conversion amounts Δt (k−1) and ΔP (k−1), they cannot be determined. To determine the α ratio in the starting Accordingly, exemplary
As shown in Expression (7) of the first embodiment, the movement amount ΔP ′ when the minute parameter Δt ′ is changed is calculated, and the ratio α
Is used.

In the above embodiment, the ratio α between the parameter change amount and the movement amount was 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 FIG. 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 figures, 1 to 7 are embodiments .
Since the configuration is the same as that of the first embodiment, the description 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), the difference β of 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).

[0047]

(Equation 6)

Next, at step ST32, the difference β
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, Pa
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.

[0051] The parameter correction method of this embodiment, the use in combination with a parameter calculation method of the second embodiment, parameters corresponding to the speed command is obtained simply and accurately.

Embodiment 4 FIG. 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
Since they are the same as those of the first embodiment, description thereof will be 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. Note that this connection state determination unit 12
The determination as to whether or not the connection state is continuous can be made based on, for example, the direction and length of the tangent vector at the connection point. When the trajectory command is represented by a B-spline curve, it can be determined from the positional relationship between the 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 P (t), P2s is P2 (t)
, P2e (t) is the end point of P2 (t), and P1e and P2s coincide. The trajectory commands in FIGS. 10 and 11 are started from P1s, move at the speed command Vcom, and stop at the end point P2e. The points Pa and Pb are command positions on P1 (t), and Pa is the case where the distance to the end point P1e of the spline curve P1 (t) is sufficient for deceleration control.
Pb is the case where the distance to the end point P1e of the spline curve P1 (t) is not enough 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 deceleration operation is not necessary, and the process proceeds to step ST5. Flows. However, 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 determination is performed by the determination unit 12. If Figure 1
If it is determined that the connection is continuous, such as 0, the process proceeds to step ST42. If it is determined that the connection is not continuous, as illustrated in FIG. 11, the process proceeds to the step of decelerating and stopping at the end point P1e of P1 (t). The processing of ST6 is performed. Step ST
At 42, since the connection points are continuous, the end point is set to the end point P2e of the next trajectory command P2 (t), and the distance Le to the end point is calculated again by the following equation (16) in step ST3. Move on to processing.

[0055]

(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 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, 21 is N
This is a curve input unit for inputting a URBS spline curve. The format is G code, IGES
(Initial Graphics Exchange Specif
The exchange format such as cation) may be set as an input format, and the curve input unit 21 stores the curve data to be stored in the numerical controller. 22
Is a curvature evaluator that evaluates the curvature of the spline curve input from the curve input unit 21 and stores the result as internal data. A speed command generator that generates a feed speed command at each position on the curve based on the obtained curvature evaluation data and a given speed command value. Reference numeral 24 denotes an acceleration / deceleration control and interpolation unit that calculates the number of pulses for each axis in accordance with the value of the feed speed command generated by the speed command generation unit 23.

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 expressed by the following equation (17).

[0061]

(Equation 8)

It should be noted that also in equation (17), BS
_{i, n (t)} is a B-spline function, d _i is the control point in three-dimensional space, w _i is a weight. By changing the control points d _i and the weights w _i , the shape of the curve can be changed. On the other hand, the curvature k of the curve is expressed by the following equation (18).

[0063]

(Equation 9)

Here, P ′ in the above 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 the 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.

Accordingly, 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).

[0069]

(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).

[0071]

[Equation 11]

All the expressions enclosed 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).

[0073]

(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 control points of Beze curve is represented by Q ₆ from Q0 as shown in Figure 18. At this time, the curve CV is that the convex closure property to a property that always exists in a convex body V1 made from a control point Q ₀ of Q _6. By using this property, it is possible to know the range of the absolute value of the curve CV1. 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 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).

[0078]

(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).

[0080]

[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 numerical controller according to Embodiment 6 of the present invention .
Is a block diagram showing the. 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 N input from the curve input unit 21.
A curve conversion unit that converts the URBS curve into a plurality of rational Besee curves is a rational Bethey curve interpolation unit that interpolates each rational Beze curve converted by the curve conversion unit 25.

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 ST35 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 represented by control points and knot vectors, and the rational Bethey curve is represented 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 d ₀ , d ₁ ,... D _{L + 2} , and weights are w ₀ , w ₁ ,.
If w _{L + 2} and the knot vector are given by u ₀ , u ₁ ,... U _L , and Δ ₀ to Δ _L are defined as Δ _i = u _{i + 1} −u _i , the plurality of rationals The Besee curve is i = 1 to L−
1 is expressed as in the following equation (25).

[0086]

(Equation 15)

Here, b _3i and b in the above equation (25)
_3i-1 and b _3i-2 are control points of a rational Bethey curve, and v _3i , v _3i-1 and v _3i-2 are weights of each rational Bethey curve and are given by the following equation (26). .

[0088]

(Equation 16)

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

[0090]

[Equation 17]

(Equation 18)

In these equations (27) and (28), v
₀ , v ₁ , v ₂ and v _3L-2 , v _3L-1 , v _3L are represented by the following equations (29) and (30).

[0092]

[Equation 19]

(Equation 20)

Such a conversion is performed as shown in FIG.
The d ₅ from the control point d ₀ of NURBS curve converts the control points b ₀ rational Beze curve b _9, from b ₀
Each set of control points of b ₃ , b ₃ to b ₆ , and b ₆ to b ₉ becomes three rational Bethey curves of CV1, CV2, and CV3 shown in FIG.

After such a conversion has been performed,
In the numerical control device according to the sixth aspect, since the rational Besee curve interpolating unit 26 having the function of interpolating the rational Besee curve is provided, the same effect as that of directly controlling the NURBS curve by interpolation 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 the sixth embodiment 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 shows a numerical controller according to Embodiment 7 of the present invention .
Is a block diagram showing the. In the figure, reference numeral 27 denotes a curvature evaluation by converting the input position command data into the form of a NURBS curve when a conventionally used straight line command, arc command, elliptical command, etc. using a G code is input. It is a command conversion unit input to the 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 is the form of implementation
Since the process proceeds in the same manner as that described in Embodiment 5 , its description is omitted. 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 shows a numerical controller according to Embodiment 8 of the present invention .
Is a block diagram showing the. 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; and 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 process 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 of 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 control device of the eighth embodiment, the selection information for instructing the speed priority mode and the selection information for instructing the accuracy priority mode are based on the input selection information.
The operator can select the type of the spline curve interpolation processing.

[0104]

As is evident from the foregoing description, according to the present invention, sprite from the current command position of the input spline song line
One or more line segments that connect to the end of the curve
The next command on the spline curve from the parameter calculated from the speed command based on the distance given as the division length
Calculate the position and realize smooth movement
Since it is configured to so that to output a speed command controlling acceleration and deceleration to, it is possible to perform interpolation of the spline curve while deceleration control, it is possible to achieve high speed of the machine械工operation, high precision effect There is.

According to the present invention , the parameter calculation unit
The parameter change is calculated from the parameter change at least one processing cycle before and the command position at least one processing cycle before.
Since it is configured so calculated that using the ratio of the amount of movement to be calculated, can reduce the calculation time of the spline curve parameters, cost reduction of the numerical controller has the effect that can be expected.

According to the present invention, the output from the acceleration / deceleration control unit
A distance corresponding to the speed command, at least one processing peripheral
Movement, which is calculated from the command position on the period before the spline curve
Parameter to correct the parameter change amount by comparing the
Since it is configured to include the data correction unit, it is possible to perform accurate speed control, and there is an effect that the speed and precision of machining can be increased.

According to the present invention, a plurality of spline curves
Even when expressing the command trajectory with multiple spline curves,
A connection state judgment unit that judges continuity at connection points
Te, when the front and rear of the spline curve by the connection state determining unit determines to be connected to a continuous, on spline curve
The current end point between the spline curve of the rear part from the command position of
Given as the length of one or more segments connecting
Since it is configured to calculate the distance to be, also it is possible to smoothly control the machine tool in a complex trajectory with a plurality of spline curves, there is an effect that it is possible to achieve faster machining, higher precision .

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a flow of the 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 control device 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 Embodiment 5 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 explaining the convex hull property of a rational Besee curve in the 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 showing an example of a speed command generated by a speed command generator of the 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 control device 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 conversion from a NURBS curve to a rational Bethey 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 controller 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 a flow of an overall operation of the embodiment .

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

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

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 command input unit 3 end point distance calculation unit 4 speed command output unit 6 parameter calculation unit 7 spline curve position calculation unit 9 parameter calculation unit 10 parameter correction unit 11 parameter conversion unit 12 connection state judgment unit 21 curve input unit 22 curvature evaluation unit 23 Speed command generator 25 Curve converter 26 Rational Besee curve interpolator 27 Command converter 31 Selection information input unit 32 Speed priority selector 33 Accuracy priority selector

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 19/4103 G05B 19/416

Claims (4)

(57) [Claims] 1. A command locus is input in the form of a spline curve.
Command input section,On the spline curve output from the command input unit
Before the current command position End point of the spline curveContact with
Given as the length of one or more subsequent line segments
Calculate and output distanceEnd distance calculation unit,  End point distance calculationDistance from the output to the end point
The speed at which the feed speed command is created and output according toDegree command output section
When, The speed command output from the speed command output unit is controlled by acceleration / deceleration.
An acceleration / deceleration control unit that outputs a smooth speed command, Before corresponding to the speed command output from the acceleration / deceleration control unit
Using the parameter change of the spline curve, Note
Calculate the parameters of the pline curveOutputParameters
Calculation section and, The spline tune output from the parameter calculation unit
Previous with line parameters Notation spline curveAbove
Next command positionAnd a spline curve position calculator that calculates the
Numerical control unit equipped. 2. A parameter change of the parameter calculator.
The amount is at least 1 treatment cycle before parameter variation,
Movement calculated from the command position at least one processing cycle before
Numerical controller according to claim 1 you calculated using the ratio of the amount. 3. Inputting a command locus in the form of a spline curve
Command input section, On the spline curve output from the command input unit
Before the current command position End point of the spline curveContact with
Given as the length of one or more subsequent line segments
Calculate and output distanceEnd distance calculation unit,  End point distance calculationDistance from the output to the end point
The speed at which the feed speed command is created and output according toDegree command output section
When,  The speed fingerSpeed command output from the command output section
An acceleration / deceleration control unit that outputs a smooth speed command, Before corresponding to the speed command output from the acceleration / deceleration control unit
Of the spline curve Using the parameter change amount, Note
Calculate the parameters of the pline curveOutputParameters
Calculation section and,  The parameterBefore output from the data calculatorNote spline song
Using the parameters of the line, place
Next command positionCurve position calculator for calculating the position
When, The distance corresponding to the speed command output from the acceleration / deceleration control unit
Release and the finger on the spline curve at least one processing cycle earlier
Movement amount calculated from the command position In comparison, the parameter
ーOf changeNumber with parameter correction unit to correct
Value control device. 4. A command trajectory in the form of a plurality of spline curves
Command input section to input with,  PreviousNote multipleJudge continuity at the connection point of the plumb curve
Connection status judgment unit,In the connection state determination unitBefore and after
It is determined that the spline curves are connected continuously
IfAfter the current command position on the spline curveDepartment
End point of the spline curveOne to connect with
The distance given as the length of multiple line segmentsEnd to calculate
Point distance calculator and,  End point distance calculationDistance from the output to the end point
Speed to create and output speed command according toOutput unit and,  The speed fingerSpeed command output from the command output section
An acceleration / deceleration control unit that outputs a smooth speed command, Before corresponding to the speed command output from the acceleration / deceleration control unit
 Parameter of the spline curveUsing the data change amount,
Calculate and output the parameters of a pline curveParameters
Calculation section and,  The parameterThe spline music output from the data calculator
Using the parameters of the line,Notation spline curveOn top
Next command positionAnd a spline curve position calculator that calculates
Numerical control device equipped with.