JP3513100B2 - Control device - Google Patents

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 numerical control) for servo-controlling an axis used for moving an object to be moved (machining head, machining table, etc.) of an automatic machine, for example, various machining machines. It is also referred to as a device), and more particularly, to the control device in an automatic machine that requires a moving path along a free curve, such as a processing machine used for mold processing.

[0002]

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

However, in response to recent demands for high-speed and high-precision machining, servo rigidity is increased and the acceleration / deceleration time constant after interpolation is often set small. In that case, the command path of the part program and the actual machining shape are close to each other, and even the error-containing block is faithfully transferred to the machining shape. Also, when machining is performed faithfully according to the command path, the machine may be shocked if it is processed at the speed as commanded.Therefore, the corners of the command path are accelerated / decelerated before interpolation to reduce the shock. ing. If this deceleration is performed on the error-containing block, the processing time is unnecessarily increased.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to overcome the above problems of the prior art. That is, the present invention improves a control device that servo-controls a moving axis of an automatic machine such as a processing machine that performs die machining, and relates to a machining program input in the form of data in which a free curve is represented by a minute line segment. Even if a minute error-containing block is included, it is possible to avoid appearing as a disturbance of the route without causing a decrease in the machining speed. Therefore, the machining speed path can be made closer to the desired shape and the path smoothness can be improved. It is intended to improve.

[0005]

According to the present invention, in 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, a line segment equal to or less than a set allowable value is set. Even if a very small block with 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, and the same line segment is changed. The above problem is solved by substantially increasing the length.

As a result, in the machining program input to the control device in a form in which the free curve is represented by minute line segments, CA
Even if a minute block with a line segment length less than the allowable value is set due to D / CAM calculation error or digitizing, etc., the minute block is disturbed in operation (it is not smooth out of the desired path and is not smooth). Behavior) is prevented.

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

First, according to one aspect of the present invention, the controller determines that the combined amount of each axial component of the straight line segment of each block is outside a predetermined allowable range (less than or equal to the lower limit length). A means for determining the block as an error-containing block is provided. Then, for a block determined as an error-containing block, if the combined amount of each axial component of the segment combined with the next block is within the allowable range, the segment midpoint of the block immediately preceding the error-containing block and the error Further, there is further provided a means for generating a correction path composed of a straight line or a curved line element connecting the midpoint of the block immediately after the containing block, and the movement of the object is controlled along the correction path.

According to another mode, the control device stores a permissible range for each axis component, and when each axis component of the straight line segment of each block is out of the range, And means for determining as the error-containing block. Then, for the block determined to be the difference-containing block, if even one axis among the axial components of the segment combined with the next block is within the allowable range,
And a means for generating a correction path consisting of a straight line or a curved line element connecting the midpoint of the segment of the block immediately preceding the error-containing block and the midpoint of the block immediately after the error-containing block. Control the movement of the object.

According to yet another form, the control device estimates the target curve from the sequence of each successive block, and the distance that the straight line segment of each block is away from the target curve has a predetermined tolerance. And means for determining the block as an error-containing block when it is out of the range. Then, for the block determined to be the 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 segment of the block immediately preceding the error-containing block is midway. And a means for generating a correction path composed of a straight line or a curved line element connecting the point and the midpoint of the block immediately after the error-containing block, and the movement of the object is controlled along the correction path.

In any of these embodiments, if the block determined to be the error-containing block is also the error-containing block when combined with the next block,
Further, it is preferable to further include means for specifying the error command block by repeating the determination as to whether or not the block includes an error-containing block when combined with the next block until the block does not become the error-containing block. Here, the “error command block” is a block having a line segment length less than the allowable value obtained in this summation process (the last summed block when successfully exiting the error-containing state is Error command block is not included).

If the modified path is a curve, the curve may be one of a circular arc, a parabola, a NURBS curve or a spline curve.

Further, 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 preset 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 block immediately after that which is separated by a preset allowable value from.

[0014]

1 is a block diagram showing the main part of a control device (numerical control device) used in an embodiment of the present invention. First, 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 a parameter for defining an allowable range (especially lower limit) of the allowable line segment length or an allowable range (especially 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 section 3, a pre-interpolation acceleration / deceleration processing section 5, and an interpolation processing section 6, and the output of the interpolation processing section 6 includes acceleration / deceleration control for positioning, for each axis. Control is performed. In this example, the X axis, Y axis, and Z axis can be controlled. Further, in consideration of the features of the present invention, the command analysis unit 3
Contains a program modification block 4.

When executing the automatic operation, the data of the part program in the machining program is read from the program storage area 1 and input to the command analysis section 3. The command analysis unit 3 is
It is a pre-processing unit that generates data for interpolation from the command of the movement amount and the feed rate for each command block. The preprocessed data is automatically controlled in speed command by the pre-interpolation acceleration / deceleration processing unit 4 and then input to the interpolation processing unit 5 so that each axis (eg, X-axis, Y-axis)
(Z axis, Z axis) is divided into movement commands to the servo motors and output to the servo control unit.

In the block combination processing performed inside the command analysis unit 3, the necessary change is made to the data of the part program and the command path designated by the part program is modified according to the processing described later (correction path). ) Is created 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 (specified straight line segment), G90 (90% smoothness around the corner), commanded speed (1000 mm /
Minutes). The second row N2 to the eighth row N8 represent 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, the size of the movement designated by each block poses a problem, so for the part program illustrated in FIG.
Figure 3 is a table that summarizes the axis movement, Y-axis movement, and line segment length.
It was shown to.

In this embodiment, a parameter storage area is successively compared with an allowable line segment length (for example, 1 mm) in advance, 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 that. The command shape of the correction path is curved 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, and a command is issued. Input to the analysis section.

The resulting program block has a smooth shape, so that the machining speed can be increased and the machining 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 (less than or equal to the lower limit or less), and this is determined to be 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 side, and the end point is moved and corrected to the next block N6 side. 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 the command analysis unit 3 (program change 4)
The flowchart of FIG. 6 shows an outline of the algorithm of the block combination process (path change related part) performed by the above. The main points of each step of processing for one cycle are as follows.

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

Step S2: unprocessed, the most N on the route
For the data of the block on the first side, the line segment length of the block is obtained. In the first processing cycle, first, block N2
A line segment length of 5 mm is required. Similarly, the second time,
In the third and fourth processing cycles, 3.74 each
6 mm, 3.325 mm, and 0.575 mm are obtained as the line segment length. Note that N1 defines the initial position and the like, is not considered as a block of a movement command, and the 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), and if it is shorter than the allowable value (lower limit), it is determined to be an error-containing block. Then, the process proceeds to step S4. In this case, it can 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 process for the block ends. For example, when the allowable value is 1 mm, the process cycle of block N2 to block N4 does not proceed to step S4.

Step S4: The data of the next block is read and added to the data of the corresponding block for each X component and Y component (a combined block is obtained by vector addition of two blocks). Then, the process proceeds to step S5. If the allowable value is 1 mm in the program of FIG. 2, block 5 is block 6
Is summed up with.

Step S5: The line segment length is calculated for the combined block obtained in step S4, and it is determined whether it is shorter than the allowable value (lower limit) as in step S3. If yes, the process returns to step S4 again, the data of the next block is read, and the addition block is obtained again by vector addition. Hereinafter, steps S4 and S5 are repeated until a negative determination output is obtained in step S5. When a negative determination output is obtained in step S5, the process proceeds to step S6. At this time point, the block which is the latest addition target is set as the block M. Further, the block obtained by the summing becomes the error command block.

Step S6: The positions of the start point and the end point of the error containing block or the error command block are changed. The position of the changed start point 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). The position of the changed end point 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). Note that various methods can be adopted as to where to specify on the path of the block immediately before and immediately after. Two examples will be given here.

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

Example 2: The shortage of the line segment length of the error containing block or the error command block, which is insufficient for the allowable value, is calculated and shared by the change of the start point and the change of the end point. For example,
The start point change and the end point change are equally divided, and the corresponding internal division points are set on the route section of each block immediately before and immediately after the start point (after change) and the end point (after change). With this method,
Changing the start and end points ensures that the line segment length reaches the allowable value. Furthermore, a line segment length may be obtained by adding a slight margin (for example, 10% increase) to this shortage.

Incidentally, with the change of the start point of the error containing block, the end point of the block immediately before the error containing block is naturally changed. In general, when the starting point of an arbitrary error-containing block is changed, its position data is automatically set as the ending point position data of the block immediately before it. In addition, the start point of the latest summation target block M is changed along with the change of the end point of the error containing block. Generally, when the end point of an arbitrary error-containing block is changed, the data of the end point is used as the start point data of the block finally added to the error-containing block.

When the allowable value is 1 mm in the program of FIG.
For the first time in the processing cycle of block N5, the process proceeds from step S3 to step S4, and the data of block N6 is read. When 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, and the start point and the end point of the block N5 (that is, the block N4).
End point and the start point of 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 processing is completed. In step S1 of the next cycle, the data of the block next to the block M is read out, and the processing from step S2 onward 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.
Processing cycle is executed.

However, strictly speaking, since 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 block after this change is made. The line segment length of M may be less than the allowable value. In order to deal with this possibility, the next processing 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 it is determined in step S3 whether or not the line segment is less than an allowable value, and the subsequent processing is similarly performed.

The curved line interpolation of the block defined by the changed start point and end point may be circular interpolation, parabolic interpolation, spline interpolation, NURBS interpolation, or the like, and which is adopted is a design choice.

Further, here, as the determination of the error-containing block (step S3), the line segment length of each block in the part program is sequentially compared with the allowable line segment length stored in the memory in advance, and the line segment of the block is calculated. If the length is shorter than the allowable line segment length, the next command block is read.If the line segment length of the combined block is shorter than the allowable line segment length, the next block is read further. A method of reading the next block until the line segment length becomes longer than the allowable line segment length and setting the block or the final summation block satisfying the condition of being shorter than the allowable line segment length as the error command block is described.

However, other determination methods 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 it is "less than the allowable value for all axes", the process may proceed to step S4 (other than that, the process ends).

In this case, in step S4, the next command block is read, and when the movement amount of each axis of the combined block is less than or equal to the allowable value, the next block is further read (step S5 → step S4). The reading of the next block is repeated until the amount of movement of each axis of the blocks thus combined is not less than the allowable value, and the block concerned is added (when step S5 is cleared in only one block next to the block containing an error). Alternatively, a method may be adopted in which the final combined block in which the movement amounts of the respective axes are all equal to or less than the allowable value is determined as an error-containing block.

Further, in step S3, a target curve is estimated from each block sequence, and the distance at which each block is separated from the target curve is sequentially compared with an allowable distance stored in a memory in advance, and each block has a target curve. If the distance away from is smaller than the allowable distance, the error-containing block may be specified by similarly comparing with the next block whether or not the distance away from the target curve is smaller than the allowable distance. The point is that there are various variations in the criteria for determining whether or not an error is contained.

In any case, if the error-containing state cannot be exited by one time of adding the next blocks, the addition of the next block is repeated, and the blocks added up to immediately before the exit from the error-containing state are succeeded. The error command block is preferable.

Different from the cases of FIGS. 4 and 5, FIGS. 7 and 8 show an example of a case of not returning from step S5 to step S6 but returning from step S5 to step S4. The example shown in FIG. 7 represents a case in which, instead of the block N5 in FIG. 4, two blocks N51 and N52 are included in the original path specified by the part program. In this case, N51, N52
Even if these two blocks are combined, the path length is less than the allowable value (lower limit), and the path length exceeds the allowable value (lower limit) only when N6 block is further added.

Therefore, in the processing cycle started by reading the block N51 (step S1), step S1 (first time) → step S2 (first time) → step S3 (first time) → step SS4 (first time) → 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 N7 block (or the N6 block whose start point is changed).

[0043]

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

[Brief description of drawings]

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.

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

FIG. 3 is a table showing a block number, an X-axis movement amount, a Y-axis movement amount, and a line segment length for the part program illustrated in FIG.

FIG. 4 shows an example of the shape of a command route before the route is changed.

5 shows an example of the shape of the command route after the route is changed, with respect to the shape of the command route shown in FIG.

FIG. 6 is a flowchart showing an outline of an algorithm of block combination processing (route change related portion).

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

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

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G05B 19/18-19/46 B23Q 15/00-15/28

Claims (6)

(57) [Claims] 1. A control device for controlling movement of an object according to a command program composed of a plurality of blocks including straight line segments; the combined amount of each axial component of the straight line segments of each block is outside a predetermined allowable range. When the block is determined to be an error-containing block, and if the combined amount of each axial component of the segment combined with the next block is within the allowable range, the error-containing block Of the segment of the block immediately before and the midpoint of the block immediately after the error-containing block, and a means for generating a correction path composed of a straight line or a curved line element, and controlling the movement of the object along the correction path. A control device characterized by: 2. A control device for controlling movement of an object according to a command program composed of a plurality of blocks including straight line segments; means for storing an allowable range for each axis component, and a straight line segment for each block. A 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 axis among the axis components of the segment combined with the next block If it is within the allowable range, a means for generating a correction path composed of a straight line or a curved line element connecting the midpoint of the segment of the block immediately preceding the error-containing block and the midpoint of the block immediately after the error-containing block, A control device comprising: a movement control unit for moving an object along the correction path. 3. A control device for controlling movement of an object according to a command program composed of a plurality of blocks including straight line segments; means for estimating a target curve from a series of consecutive blocks, and each block from the target curve. Means for determining the block as an error-containing block when the distance at which the straight line segment is separated is outside the predetermined allowable range, and for the block determined to be the error-containing block, the segment combined with the next block is the target curve When the distance away from is within a predetermined allowable range, it consists of a straight line or a curved line element connecting the midpoint of the segment of the block immediately preceding the error-containing block and the midpoint of the block immediately after the error-containing block. A means for generating a correction path, and controlling movement of an object along the correction path. Control apparatus according to claim Rukoto. 4. A block determined as an error-containing block is determined whether or not it becomes an error-containing block when combined with the next block, and whether it becomes an error-containing block when combined with the next block. The control device according to any one of claims 1 to 3 , further comprising a unit for specifying an error command block by repeating the process until the block does not become an error containing block. Wherein when said modified path is curved, the curve arc, parabola, is one of the NURBS curve or a spline curve, any of the claims 1 to 4
The control device according to item 1 . 6. 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 preset allowable value, and the midway point of the immediately following block is the start point of the immediately following block. from what of the claims 1 to 5, characterized in that a point on preset allowable value min apart straight after block
The control device according to item 1 .