JP2002132317A - Controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller which can prevent a path from being disordered without any decrease in speed even if a fine error-containing block is generated. SOLUTION: Data of respective blocks of a part program are read in to find the segment lengths of the blocks, which are compared with a previously set permissible value (lower limit); and it is decided that a block whose segment length is shorter than the permissible value is an error-containing block (N51). In this case, the following blocks are sequentially put together until their length exceeds the permissible value to specify an error command block (N51-N52). The start point and end point of the error command block are specified (changed). The start point is determined halfway in the path of the block N4 right before it and the end point is determined halfway in the path of the block N6 right after it; and the command path determined by those start point and end point is interpolated with an arc, a parabola, an NURBS curve, a spline curve, etc. Permissible values may be set by axes and 'the condition that all components are less than the permissible values' may be adopted for error containing block decision making and error command block specification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device (usually a numerical control) for servo-controlling an axis used for moving a moving object (a processing head, a processing table, etc.) of an automatic machine, for example, various processing machines. In particular, the present invention relates to the control device in an automatic machine which requires a moving path along a free curve, such as a processing machine used for die machining.

[0002]

2. Description of the Related Art For example, in a machining machine used for die machining, when a part program for performing machining according to a desired curve (curve at the time of design) is created, CAD / CAM is used.
Is widely used. In general, a part program generated by CAD / CAM is generated by dividing a command from a curve at the time of design into minute line segments having an allowable tolerance. This line segment length is generally determined by the machining shape and the tolerance amount, but a very small block (hereinafter, an error-containing block) may be generated in a portion connecting two curves. Further, in a part program by digitizing, a minute error-containing block may be generated due to reflection of minute unevenness of the model or change in a contact condition between the probe and the model. Conventionally, such a small disturbance in the path is blunted by acceleration / deceleration after interpolation or a servo circuit, and the effect on machining is negligible.

However, in response to recent demands for high-speed and high-precision machining, servo rigidity has been increased, and the acceleration / deceleration time constant after interpolation has been often set to be small. In this case, the instruction path of the part program and the actual machining shape are close to each other, and even the error-containing blocks are faithfully transferred to the machining shape. Also, if machining is performed faithfully according to the command path, shock may occur on the machine if machining is performed at the speed specified by the command.Acceleration / deceleration before interpolation is performed at the corner of the command path to reduce shock. ing. When the deceleration is performed on the error-containing block, the processing time is unnecessarily increased.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems of the prior art. That is, the present invention has improved a control device that servo-controls a moving axis of an automatic machine such as a processing machine for performing a die processing, for a processing program input in the form of data in which a free curve is represented by minute line segments. Even if a minute error-containing block is included, it is possible to avoid appearing as a path disorder without particularly reducing the processing speed, so that the processing speed path can be made closer to the desired shape and the path smoothness can be reduced. It is intended to be improved.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a machining program input to a control device (numerical control device) in a form in which a free curve is represented by a minute line segment. Even if a very small block having a length is set, the command shape of the block is set to curve interpolation, and the start point of the block (that is, the end point of the immediately preceding block) and the end point of the block are changed. The above problem has been solved by correcting the length substantially upward.

[0006] With this, the machining program input to the control device in a form in which the free curve is represented by minute line segments contains CA
Even if a very small block with a line segment length less than the allowable value is set due to D / CAM calculation error or digitizing, the very small block is disturbed in operation (not smooth out of the desired path) Operation).

More specifically, the present invention improves a "control device for controlling the movement of an object in accordance with a command program constituted by a plurality of blocks including straight segments" in the following manner.

First, according to one embodiment of the present invention, the control device is configured to execute the control when the combined amount of each axis component of the linear segment of each block is outside a predetermined allowable range (less than or less than a lower limit length). , Means for determining the block as an error-containing block. Then, for a block determined to be an error-containing block, when the combined amount of each axis component of the segment combined with the next block is within the allowable range, the midpoint of the segment of the block immediately before the error-containing block and the error Means for generating a correction path consisting of a straight line or a curve element connecting the midpoint of the block immediately after the content block, and controlling movement of the object along the correction path.

According to another aspect, the control device includes a means for storing an allowable range for each axis component, and a unit for controlling the block when all the axis components of the linear segment of each block are out of the range. Means for determining as an error-containing block. Then, for the block determined to be the difference-containing block, when at least one of the axis components of the segment combined with the next block is within the allowable range,
Means for generating a correction path composed of a straight line or a curve element connecting the midpoint of the segment of the block immediately before the error-containing block and the midpoint of the block immediately after the error-containing block, further comprising: The movement of the object is controlled.

In accordance with yet another aspect, the control device includes means for estimating a target curve from a sequence of successive blocks, and a distance from which the linear segment of each block is separated from the target curve is a predetermined tolerance. Means for determining the block as an error-containing block when the block is out of the range. Then, for a block determined to be an error-containing block, if the distance of the segment combined with the next block from the target curve is within a predetermined allowable range, the middle of the segment of the block immediately before the error-containing block is determined. Means for generating a correction path composed of a straight line or a curved line element connecting the point and an intermediate point of the block immediately after the error-containing block, and moving and controlling the object along the correction path.

In any of these embodiments, when a block determined as an error-containing block becomes an error-containing block when combined with the next block,
Further, it is preferable to further include a unit for specifying an error command block by repeating determination of whether or not an error-containing block when combined with the next block until the block does not become an error-containing block. Here, the “error command block” refers to a block having a line segment length less than the allowable value obtained in the summation process (the last summed block when the escape from the error-containing state is successful is It is not included in the error command block.)

When the correction path is a curve, the curve may be one of an arc, a parabola, a NURBS curve, and a spline curve.

The midpoint of the immediately preceding block is a point on the immediately preceding block separated from the end point of the immediately preceding block by a predetermined allowable value, and the midpoint of the immediately following block is the starting point of the immediately following block. May be a point on the immediately succeeding block that is separated from a predetermined allowable value.

[0014]

FIG. 1 is a block diagram showing a main part of a control device (numerical control device) used in an embodiment of the present invention. The control device has a program storage area 1 for storing a part program and a parameter storage area 2 for storing parameters for determining various operating conditions. The parameters stored in the parameter storage area 2 include parameters for determining an allowable range (particularly the lower limit) of the allowable line segment length or an allowable range (particularly the lower limit) for each axis component. The parameters can be manually input and changed from the control panel, for example.

The control device further includes a command analysis unit 3, a pre-interpolation acceleration / deceleration processing unit 5, and an interpolation processing unit 6. The output of the interpolation processing unit 6 controls each axis including acceleration / deceleration control accompanying positioning. Control is performed. In this example, the X axis, the Y axis, and the Z axis can be controlled. Further, the command analysis unit 3 reflects the features of the present invention.
Contains a block 4 of the program change.

At the time of executing the automatic operation, the data of the part program in the machining program is read out from the program storage area 1 and input to the command analyzer 3. The command analysis unit 3
This is a pre-processing unit that generates interpolation data from a command of a moving amount or a feed speed for each command block. The preprocessed data is automatically controlled by the pre-interpolation acceleration / deceleration processing unit 4 for a speed command, and is then input to the interpolation processing unit 5 where each axis (for example, X axis, Y axis,
(Axis, Z axis) are divided into movement commands to the respective servo motors and output to the servo control unit.

In the block combining process performed inside the command analysis unit 3, a necessary change is made to the data of the part program and a command route specified by the part program is corrected (corrected route) according to a process described later. ) Is generated, and the corresponding interpolation data is output to the pre-interpolation acceleration / deceleration processing unit 5. The block for this correction is indicated by reference numeral 4 (program change).

Here, as an example, a case will be described in which a part program as shown in FIG. 2 is read out and path movement is executed. For convenience of explanation, it is assumed that the movement is two-dimensional and the X axis and the Y axis are controlled.

The first row N1 has a starting position X = 0, Y = 0,
The motion conditions are G1 (straight line segment designation), G90 (smoothness around corner 90%), command speed (1000 mm /
Minutes). The second row N2 to the eighth row N8 indicate the end point position of each block. For example, the end point position of the first block N2 is X = 5.00, Y = 0.0 (no movement, not described). In the present invention, since the size of the movement specified by each block becomes a problem, the block number, X
Fig. 3 summarizes the axis movement amount, Y axis movement amount, and line segment length in tabular form.
It was shown to.

In this embodiment, a parameter storage area is sequentially compared in advance with an allowable line segment length (for example, 1 mm), and a block shorter than the allowable line segment length is regarded as an error-containing block.
In this example, the movement of the block number N5 corresponds to this. The command shape of the correction path is curve interpolation, and the start point of the error-containing block, that is, the end point of the previous block (block number N4 in this example) and the end point of the error-containing block (block number N5 in this example) are corrected. Input to the analysis unit.

The resulting program block has a smooth shape, so that the processing speed can be increased and the processing shape accuracy can be improved. Here, the curve interpolation includes circular interpolation, parabolic interpolation, spline interpolation, NURBS interpolation, and the like. Such command path shapes before and after correction are as shown in, for example, FIG. 4 (before correction) and FIG. 5 (after correction). That is,
In this example, the movement of the block number N5 is a minute movement outside the allowable range (below the lower limit or less than the lower limit), which is determined as an error-containing block and corrected. The correction is performed so that the path length of the block becomes longer. As shown in FIG. 5, the start point is moved and corrected to the immediately preceding block N5, and the end point is moved and corrected to the next block N6. Then, curve interpolation is performed according to the command shape after the transfer correction, and a smooth path as shown in the figure can be obtained.

Inside of command analysis unit 3 (program change 4)
FIG. 6 is a flowchart showing an outline of an algorithm of the block combination process (path change related portion) performed by the above. The main points of each step of the processing for one cycle are as follows.

Step S1: The data of one block of the part program (see FIG. 2) is read into the command analyzer of the control device. However, in the first processing cycle, the data of the data of N1 (see FIG. 2) is also read.

Step S2: Unprocessed and the most N on the route
With respect to the data of the block on one side, the line segment length of the block is obtained. In the first processing cycle, first, the block N2
5 mm is required as the line segment length of. Similarly, the second time,
In the third and fourth processing cycles, respectively, 3.74
6 mm, 3.325 mm, and 0.575 mm are obtained as line segment lengths. Note that N1 defines an initial position and the like, is not considered to be a block for a movement command, and a line segment length is not calculated.

Step S3: The obtained line segment length is compared with an allowable value (lower limit) defined by a parameter stored in a memory (parameter storage area). Then, the process proceeds to step S4. In this case, it may be said that the error containing block itself becomes the error command block. If it is not shorter than the allowable value (lower limit), it is determined that the block is not an error-containing block, and the processing for the block ends. For example, if the allowable value is 1 mm, the process does not proceed to step S4 in the processing cycle of blocks N2 to N4.

Step S4: The data of the next block is read and added to the data of the block for each of the X and Y components (a sum block is obtained by vector addition of two blocks). Then, the process proceeds to step S5. In the case of an allowable value of 1 mm in the program of FIG.
Is added to

Step S5: A line segment length is calculated for the combined block obtained in step S4, and it is determined whether or not it is shorter than the allowable value (lower limit) as in step S3. If the determination is yes, the process returns to step S4 to read the data of the next block, and obtain the sum block again by the vector addition. Hereinafter, steps S4 and S5 are repeated until a determination result of No is obtained in step S5. When the determination output of No is obtained in step S5, the process proceeds to step S6. At this point, the block that is the latest addition target is set as a block M. Further, the block obtained by the summation becomes the error command block.

Step S6: For the error containing block or the error command block, the positions of the start point and the end point are changed. The position of the starting point after the change is a point on the path designated by the block immediately before the error containing block or the error command block (see FIG. 5 and FIG. 8 described later). Also, the position of the end point after the change is a point on the path designated by the block immediately after the error containing block or the error command block (see FIG. 5 and FIG. 8 described later). It should be noted that various methods can be adopted as to where to specify on the path of the block immediately before or after these blocks. Here, two examples will be given.

Example 1: The starting point is an internal dividing point of a specific ratio (for example, a middle point, 2: 1) on the path section of the immediately preceding block. Similarly, the end point is an internal dividing point of a specific ratio (for example, a middle point, 1: 2) on the route section of the block immediately after, or the like. The specific ratio is separately set in the parameter return area.

Example 2: Calculate the shortage of the line length of the error-containing block or the error command block that is less than the allowable value, and share it by changing the start point and the end point. For example,
The start point and the end point are equally divided, and the corresponding inner division points are determined on the route sections of the blocks immediately before and immediately after the start point (after the change) and the end point (after the change). In this scheme,
Changing the start point and end point ensures that the line segment reaches the permissible value. Furthermore, a line segment length obtained by adding a margin (for example, an additional 10%) to this shortage may be obtained.

When the start point of the error-containing block is changed, the end point of the block immediately before the error-containing block is also changed. Generally, when the start point of an arbitrary error-containing block is changed, the position data is automatically set as the end point position data of the immediately preceding block. Also, with the change of the end point of the error-containing block, the start point of the latest addition target block M is also changed. Generally, when the end point of an arbitrary error-containing block is changed, the data of the end point is used as the data of the start point of the block finally added to the error-containing block.

When the allowable value is 1 mm in the program of FIG.
The process proceeds from step S3 to step S4 for the first time in the processing cycle of block N5, and the data of block N6 is read. Since the sum of the block N5 and the block N6 exceeds the allowable value of 1 mm, the process proceeds from step S5 to step S6, where the start point and the end point of the block N5 (that is, the block N4)
Of the block N6 and the start point of the block N6) are corrected (see FIGS. 4 and 5). Movement control is performed according to a command block including a new movement command corresponding to this correction.

Thus, one cycle of the process is completed. In step S1 in the next cycle, the data of the block next to the block M is read, and the processing of step S2 and subsequent steps is performed. When the allowable value is 1 mm in the program of FIG. 2, the processing cycle of block N5 is followed by block N7.
Is executed.

Strictly speaking, however, the starting point of the block M (block 6 in this example) is changed so that the line segment length of the block M is shortened (see FIG. 5). The line segment length of M may be less than the allowable value. To cope with this possibility, the next process may be performed on the block M itself. In that case,
A line segment between the changed start point and the (unchanged) end point is calculated in step S2, and in step S3, it is determined whether or not the line segment is less than an allowable value, and the subsequent processing is performed in the same manner.

The curve interpolation of the block defined by the starting point and the ending point after the change includes circular interpolation, parabolic interpolation, spline interpolation, NURBS interpolation, and the like, and which one to use is a design choice.

Here, as the determination of an error-containing block (step S3), the line segment length of each block in the part program is sequentially compared with an allowable line segment length previously stored in a memory, and the block segment length of the block is determined. If the length is shorter than the allowable line segment length, the next command block is read.If the length of the combined block is shorter than the allowable line segment length, the next block is further read. A method is described in which the next block is read until the line segment length is longer than the allowable line segment length, and the block or the final total block satisfying the condition that the block length is shorter than the allowable line segment length is set as the error command block.

However, another determination method may be adopted.
For example, the allowable movement amount is set for each axis, step S2 is omitted (not necessary here), and the movement amount of each axis of each block in the part program is compared with the set value in the determination in step S3. If "less than the allowable value for all axes", the process may proceed to step S4 (otherwise, the process ends).

In this case, in step S4, the next command block is read, and if the movement amount of each axis of the combined block is less than the allowable value, the next block is read (step S5 → step S4). The reading of the next block is repeated until all the movement amounts of the respective axes of the block adjusted in this way do not fall below the allowable value, and the block is added (when the sum is cleared by only the next block including the error-containing block and the step S5 is cleared). Alternatively, a method may be adopted in which the final sum block in which all the movement amounts of the respective axes are equal to or smaller than the allowable value is determined to be an error-containing block.

In step S3, a target curve is estimated from each block row, and the distance of each block from the target curve is sequentially compared with an allowable distance stored in a memory in advance. If the distance away from the target curve is smaller than the permissible distance, the error-containing block may be specified by sequentially comparing whether the distance away from the target curve is smaller than the permissible distance together with the next block. The point is that there are various variations in the criterion for judging whether or not an error is included.

In any case, if it is not possible to escape from the error-containing state by one time of the next block summation, the summation of the next block is further repeated, and the blocks summed up immediately before succeeding in exiting from the error-containing state are determined. It is preferable to use an error command block.

FIGS. 7 and 8 show examples of the case where, unlike the cases of FIGS. 4 and 5, the process does not go directly from step S5 to step S6 but returns from step S5 to step S4. The example shown in FIG. 7 shows a case in which two blocks N51 and N52 are included in the original path specified by the part program instead of the block N5 in FIG. In this case, N51, N52
Even if these two blocks are combined, the path length is equal to or less than the allowable value (lower limit), and the path length exceeds the allowable value (lower limit) only after the N6 blocks are further added.

Therefore, in the processing cycle started by reading the block N51 (step S1), step S1 (first) → step S2 (first) → step S3 (first) → step SS4 (first) → step S5 (first time) → step S4 (second time) → step S
Processing is performed in the order of 5 (second time) → step S6 (first time). The next processing cycle is executed for the block N7 (or the block N6 whose starting point has been changed).

[0043]

According to the present invention, even if a small error block due to a calculation error or the like is included in the part program, the block is changed so that it does not appear as a disturbance in the operation path, so that high-precision machining is performed. be able to. In addition, since special acceleration / deceleration control (acceleration / deceleration before interpolation in the corner portion) for preventing disturbance of the operation path is not required, work such as machining is made more efficient.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main part of a control device (numerical control device) used in an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a part program.

FIG. 3 shows, in a table format, block numbers, X-axis movement amounts, Y-axis movement amounts, and line segment lengths for the part program illustrated in FIG.

FIG. 4 shows one example of the shape of a command route before a route change.

5 is a diagram illustrating an example of the shape of the command route after the route is changed with respect to the shape of the command route illustrated in FIG. 4;

FIG. 6 is a flowchart showing an outline of an algorithm of a block joining process (path change related portion).

FIG. 7 shows another example of the shape of the command route before the route change.

8 is a diagram illustrating an example of the shape of the command route after the route is changed with respect to the shape of the command route illustrated in FIG. 7;

[Explanation of symbols]

 1 Program storage area 2 Parameter storage area 3 Command analysis section 4 Program change block 5 Acceleration / deceleration processing section before interpolation 6 Interpolation processing section

Claims (6)

[Claims] 1. A control device for controlling the movement of an object in accordance with a command program composed of a plurality of blocks including a straight line segment; the combined amount of each axis component of the straight line segment of each block is outside a predetermined allowable range. Means for determining the block as an error-containing block, and for the block determined to be an error-containing block, when the combined amount of each axis component of the segment combined with the next block is within the allowable range, the error-containing block Means for generating a correction path consisting of a straight line or a curve element connecting the midpoint of the segment of the block immediately before and the midpoint of the block immediately after the error-containing block, and moving and controlling the object along the correction path. A control device characterized in that: 2. A control device for controlling the movement of an object in accordance with a command program constituted by a plurality of blocks including a straight line segment; means for storing an allowable range for each axis component; Means for determining the block as an error-containing block when all the axis components are out of the range; and for the block determined to be the difference-containing block, even one of the axis components of the segment combined with the next block Means for generating a correction path consisting of a straight line or a curve element connecting the midpoint of the segment of the block immediately before the error-containing block and the midpoint of the block immediately after the error-containing block. A control device for controlling movement of the object along the correction path. 3. A control device for controlling the movement of an object in accordance with a command program composed of a plurality of blocks including a straight line segment; means for estimating a target curve from a sequence of successive blocks; Means for judging the block as an error-containing block when the distance at which the straight line segment is separated is outside a predetermined allowable range; and for the block judged to be an error-containing block, the segment combined with the next block forms the target curve If the distance away from the error-containing block is within a predetermined allowable range, it is composed of straight-line or curved-line elements connecting the midpoint of the segment of the block immediately before the error-containing block and the midpoint of the block immediately after the error-containing block. Means for generating a correction path, and controlling movement of the object along the correction path. Control apparatus according to claim Rukoto. 4. It is determined whether a block determined to be an error-containing block also becomes an error-containing block when combined with the next block, and whether it is an error-containing block when combined with the next block. By repeating until it does not become an error-containing block,
4. The control device according to claim 1, further comprising means for specifying an error command block. 5. The control device according to claim 1, wherein when the correction path is a curve, the curve is one of an arc, a parabola, a NURBS curve, and a spline curve. 6. The intermediate point of the immediately preceding block is a point on the immediately preceding block separated from the end point of the immediately preceding block by a predetermined allowable value, and the intermediate point of the immediately following block is a starting point of the immediately following block. 6. The control device according to claim 1, wherein the point is a point on the immediately subsequent block separated from a predetermined allowable value.