JP3203288B2 - 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 the operation position of a machine in accordance with a given command. The present invention relates to a numerical control device that reduces and realizes highly efficient machining.

[0002]

2. Description of the Related Art In a numerical control device for controlling the operating position of a machine such as a machine tool or a robot, the operation is started or stopped so that an excessive load is not applied to a motor or a sudden shock is applied to a mechanical system. Sometimes slow acceleration / deceleration. FIG. 5 shows an example of the configuration of such a numerical control device. This example is a main part of a numerical controller of a machine tool for controlling an X axis and a Y axis to move a tool according to a machining shape instructed by a machining program.

[0003] The machining program PP is composed of a plurality of blocks, and an instruction for designating a machine operation is described for each block. In general, one command is composed of an address represented by an alphabet and a data word following it, and a plurality of commands are described in one block to specify the operation of the machine.
The linear shape is designated by "G01" and end points "X" and "Y". The arc shape is "G02" (for clockwise arc), "
G03 ”(in the case of a counterclockwise arc) and the end point“ X ”,”
Y ”and“ I ”,“ J ”or an arc radius“ R ”that designates the center point of the arc so that the arc shape is uniquely determined.
The execution data is interpreted block by block, and the execution data for performing the shape interpolation is generated and stored in the execution data buffer 3. A shape command I for defining an interpolation shape and its path length L from a data word such as address "G", "X", "Y", "I", "J" are sent from a data word at address "F".
Are interpreted and generated respectively. Then, the generated execution data is sequentially stored in the empty space of the execution data buffer 3. The execution data buffer 3 is means for storing execution data for a plurality of blocks.

[0004] The following is a description up to the point where interpolation is performed at a constant interpolation cycle based on the execution data and the motor is driven.
The number of the block to be interpolated is i and the time of the interpolation cycle is t
Indicated by The interpolation unit amount calculation unit 4 obtains the feed command F [i] of the same block as the block to be interpolated by the shape interpolation unit 8 from the execution data buffer 3 and adds this to the feed ratio OR [t] read at each interpolation cycle. Multiply the value by the command interpolation unit amount Uc
[t] is calculated and output to the interpolation unit amount cutoff unit 16. The feed ratio OR [t] is determined by an override switch, and the override switch can be operated by an operator. That is, the feed rate can be changed by the operator during machining. The interpolation unit amount cutoff unit 16 outputs the command interpolation unit amount Uc [t] to the smoothing filter 7 as the interpolation unit amount U [t]. However, when starting to interpolate a new block, only the first time T acts to block the command interpolation unit amount Uc [t]. The time T is the same as the time constant T described below. The value of the interpolation unit amount U [t] in the case of interruption is 0.

[0005] The smoothing filter 7 accumulates the input IN by the number of time constants T, and smoothes the output IN by calculating the output OUT according to Equation 1.

(Equation 1) OUT [i]: Current output IN [ik]: Input k times earlier T: Time constant The time constant T is a value determined by the characteristics of the machine.
It is obtained by dividing the allowable machine speed Vmax by the allowable machine acceleration Amax. Here, the interpolation unit amount U [t] output from the interpolation unit amount cutoff unit 16 is treated as an input IN [i], and an output OUT [i] obtained by smoothing this is a smooth interpolation unit amount U ′ [t].
Since the value to be handled is the speed, the smoothing filter 7 has the effect of accelerating and decelerating the input speed and outputting it.

The shape interpolating unit 8 interpolates the shape represented by the shape command I [i] in accordance with the smooth interpolation unit amount U '[t] every interpolation cycle, and outputs an interpolated position P [t]. . Further, the smoothed interpolation unit amount U ′ [t] is subtracted from the remaining path length L ′ [t−1] to obtain a remaining path length L ′ [t]. When the first block is interpolated or when the remaining path length L '[t-1] is equal to or less than 0, the shape command I from the execution data buffer 3 is obtained prior to the interpolation.
[i] and the path length L [i] are obtained. The X-axis and the Y-axis are controlled by the speed distribution means 9, the X-axis servo control means 10, the motor 11, the position detector 12, the Y-axis servo control means 13, the motor 14 and the position detector 15, and the final control target is obtained. A certain tool is moved according to a position P output every interpolation cycle. The components ΔX and ΔY of the moving amount ΔP per interpolation cycle are output from the speed distribution unit 9 to the X-axis servo control unit 10 and the Y-axis servo control unit 13. The movement amount per interpolation cycle is an amount corresponding to the speed.

Finally, FIG. 6 shows an example of a control result based on the shape shown in FIG. The shape in FIG. 3 includes a linear shape ending with G [1], an arc shape ending with G [2], and a linear shape ending with G [3]. FIG. 6A is a diagram showing the command interpolation unit amount Uc output by the interpolation unit amount cutoff unit 16 in a time series. t (G [1]) and t (G [2]) are times when the vehicle passes near the end point G [1] and the end point G [2]. When starting to interpolate a new block, the command interpolation unit amount Uc [t] is interrupted only for the first time T, so the interpolation unit amount U [t]
Is 0. FIG. 6B is a diagram showing the velocity vector of the position P output from the shape interpolation unit 8, that is, the magnitude of ΔP in a time series. The speed becomes 0 at the end point G [1] and the end point G [2]. FIG. 6C is a diagram showing the magnitude of the acceleration vector, which is a change in the speed vector, in a time series. As described above, according to the configuration of the related art, acceleration and deceleration are performed when the operation of the shaft is started or stopped, so that the load and shock applied to the motor and the mechanical system can be reduced. Furthermore, even at a joint of a shape where the course may suddenly change, since the vehicle temporarily stops at each shape command, the acceleration in the normal direction does not exceed the allowable acceleration of the machine.

[0008]

However, in the conventional configuration shown in FIG. 5, since the operation is stopped for each shape command, the processing efficiency is not good. In particular, when the processed shape is composed of a large number of minute line segments, an extreme The processing efficiency becomes worse. Further, the load and shock applied to the motor and the machine are unnecessarily increased. Further, for example, as in the case of the arc-shaped acceleration in FIG. 6C, the allowable acceleration Amax of the machine may be exceeded.
These are not preferable from the viewpoint of processing accuracy and machine durability. An object of the present invention is to provide a numerical controller that realizes highly efficient machining by minimizing a sudden change in the speed of the movement of the shaft to the minimum in order to solve the above problems.

[0009]

According to the present invention, a command is interpreted block by block to generate a shape command, a feed command and a path length and stored as execution data in an execution data buffer. In the numerical control device for controlling the operating position of the machine, a maximum passing speed at which the path normal direction acceleration of the shape represented by the shape command does not exceed the allowable acceleration of the machine is defined, and the execution speed is defined as one of the execution data. A pass speed defining unit that stores the data in the data buffer, and reads the shape command and the path length from the execution data buffer one block at a time, and converts the shape represented by the shape command into a smooth interpolation unit amount given for each interpolation cycle. Therefore, a shape interpolation unit that performs shape interpolation and sequentially outputs a remaining path length obtained by subtracting the smooth interpolation unit amount from the path length, In synchronization with the shape interpolation unit reads one block at a time the feed command, the interpolation unit amount calculation unit that calculates a command interpolation unit quantity by multiplying the ratio sends the feed command,
The path length and the passing speed are read out one block at a time in synchronization with the shape interpolating unit, and the upper limit speed at which the passing speed is reached from a predetermined time ago is read ahead of the path length and the passing speed, and the uninterpolated block. A look-ahead passing speed determination unit that is generated based on the obtained path length and passing speed and the remaining path length, and an interpolation unit amount limit that limits the command interpolation unit amount by the upper limit speed and outputs the command interpolation unit amount as an interpolation unit amount. And a smoothing filter for smoothing the sequentially given interpolation unit amount so as to follow the predetermined time, and outputting the smoothed interpolation unit amount as the smoothed interpolation unit amount. Then, the passage rate is Ri Do from an end point passing speed which is limited at the end of the shape represented by the shape command shaped passage speed which is limited with respect to shape itself represented by geometrical command, a circular arc shape To
In this case, the allowable acceleration is not exceeded.

[0010]

According to the present invention, since the maximum interpolation unit amount limited by the acceleration in the normal direction to the path is given to the smoothing filter for controlling the acceleration in the path direction, the allowable acceleration of the machine and the allowable speed of the machine are given. Interpolation is performed at the maximum speed not exceeding.

[0011]

FIG. 1 shows an embodiment of a numerical controller according to the present invention. The machining program PP, the program interpretation means 1, and the execution data buffer 3 are the same as those of the prior art. However, execution data includes a shape command I, a path length L, a feed F,
Further, it comprises the shape passing speed Vb and the end point passing speed Vg required in the present invention. It is assumed that the number of the block interpreted by the program interpreting means 1 is n. n-1 represents the previous block.

The passing speed defining section 2 defines a passing speed at which the acceleration in the direction normal to the course becomes the allowable acceleration Amax of the machine.
The course normal direction acceleration refers to the acceleration received when the course changes when moving along the commanded machining shape. Since the end point is a joint between the shapes, the course may change, and the shape itself represented by the shape command also changes uniformly if it is a circular arc. Therefore, the end point passing speed Vg and the shape passing speed V are used as the respective passing speeds.
b. The shape passing speed Vb [n] is defined based on the shape command I [n] output from the program interpretation means 1. If the shape command I [n] is a circular arc, it is calculated by Equation 2.

Vb [n] = min (Vmax, √ (R [n] * Amax)) R [n]: Arc radius set in shape command I [n] min (): smaller value If the shape command I [n] is a straight line, the course does not change.
The allowable speed Vmax of the machine is adopted as Vb [n]. on the other hand,
The end point passing speed Vg [n-1] is determined as follows. When moving at the speed v, if the course changes by the angle θ at a certain point, the relationship with the course normal direction acceleration a at that time is expressed by Expression 3.

## EQU3 ## where a / 2 = v.times.sin (.theta. / 2) where the acceleration a in the direction normal to the course is the allowable acceleration Amax of the machine.
In this case, the speed at that time, that is, the speed limit V is given by Expression 4.

V = Amax / (2 × sin (θ / 2)) That is, when changing the course while keeping the allowable acceleration Amax of the machine, the speed limit depends on the angle θ. Therefore, first, the cosine of the course angle θ [n-1] that changes at the end point G [n-1] is obtained from Equation 5 based on the previous shape command I [n-1] and the current shape command I [n]. .

Cosθ [n-1] = ip (E [n-1], S [n-1]) E [n-1]: Tangent line of the end point determined from the previous shape command I [n-1] Direction vector S [n]: tangent direction vector of the starting point determined from current shape command I [n] ip (): function for obtaining inner product of vector Next, from this cosine value, θ [n−1 Finally, the speed limit V is calculated according to Equation 4. Finally, the end point passing speed Vg [n-1] is determined by the speed limit V, the shape passing speed Vb [n-1] of the previous block, and the shape passing speed V of the current block.
Use the smaller one of b [n]. (Equation 6)

Vg [n-1] = min (Vb [n-1], V, Vb [n]) The end point passing speed Vg [n-1] and the shape passing speed Vb [n] defined in this manner. Is stored in the execution data buffer 3.

Hereinafter, as described in the section of the prior art, the number of the block to be interpolated is represented by i, and the time in units of the interpolation cycle is represented by t. Interpolation unit amount calculation unit 4 and shape interpolation unit 8
Is the same as that of the prior art except for the difference in configuration described below. The interpolation unit amount calculator 4 outputs the command interpolation unit amount Uc [t] to the interpolation unit amount limiter 6 described later. The shape interpolation unit 8 outputs the remaining path length L '[t-1] to the prefetch passage speed determination unit 5 described later. The machine operates in accordance with the position P output from the shape interpolating unit 8. The configuration is such that the speed distribution unit 9, the X-axis servo control unit 10, the motor 1 shown in FIG.
1, since it is the same as the position detector 12, the Y-axis servo control means 13, the motor 14, and the position detector 15, the illustration and description in FIG. 1 are omitted.

The look-ahead passing speed determination unit 5 includes a shape interpolation unit 8
Generates an upper limit speed Ul such that the speed at the position P output by the is lower than the passing speed. When a constant value is continuously input, the output of the smoothing filter 7 matches the input after the time constant T. Therefore, the speed at the position P is equal to the passing speed V
In order to satisfy the condition, the speed V may be input to the smoothing filter 7 before the time constant T at which the position P is reached, that is, the speed V may be set to the speed V from a distance of V × T. Here, since the speed is set to be equal to or lower than the passing speed, the upper limit speed Ul [t] as the maximum interpolation unit amount is determined. The data relating to the distance is based on the remaining path length L '[t-1] output from the shape interpolation unit 8 and the path length L [i + j] obtained by sequentially prefetching the execution data buffer 3. The data relating to the passing speed includes the shape passing speed Vb [i], the end point passing speed Vg [i], and the shape passing speed Vb [i + j] of the block interpolated by the shape interpolation unit 8 and the end point passing speed. Based on speed Vg [i + j].

The processing of the prefetch passage speed determining unit 5 at time t in units of the interpolation cycle will be described with reference to the flowchart of FIG. Step S1: Let j be the increment of the number of the look-ahead block with respect to the block interpolated by the shape interpolation unit 8. Since the first target block is a block interpolated by the shape interpolation unit 8, the block is initialized with 0. Step S2: D is the total path length from the position P [t-1] of the previous interpolation cycle to the end point G [i + j] of the target block. First, the remaining path length L '[t-1] output by the shape interpolation unit 8
Corresponds to this. L ′ [t−1] is substituted for D as an initial value. Step S3: The initial value of the upper limit speed Ul is calculated by the shape interpolation unit 8.
Is the shape passing speed Vb [i] of the block being interpolated.

Step S4: The distance d 'affected by the end point passing speed Vg [i + j] of the end point G [i + j] is calculated by Expression 7.

D ′ = Vg [i + j] × (T + 1) T is a time constant, and the addition of 1 is a margin in consideration of a fraction. By comparing d ′ and D, it is determined whether or not the position P [t] that will be output this time by the shape interpolation unit 8 is affected. If D ≦ d ′, it is affected, and the processing from step S5 is performed. Otherwise, it is not affected by the end point passing speed Vg [i + j], and it is not affected by the subsequent blocks. Therefore, the process jumps to step S8 and the final upper limit speed Ul [t].
Determine the value of. Step S5: min () is a function that adopts the smaller value. Influenced end point passing speed Vg [i + j]
Is smaller than the currently held upper limit speed Ul,
means replacing l with Vg [i + j]. Step S6: Update the block number increment j by one to check for the next block. Step S7: With the update of j, the path length L [i + j] of the block is added to the sum D of the path lengths. Then, returning to step S4, the inspection is repeated.

Step S8: The distance d affected by the end point passing speed Vg [i + j] when the fraction is not taken into account is as shown in Expression 8.

D = Vg [i + j] × T If the distance E obtained by subtracting d from the sum D of path lengths is greater than the currently held upper limit speed Ul, the distance E is set to 1 by Ul.
Since the interpolation can be performed more than once, Ul is changed to the final upper limit speed Ul [t].
To be adopted. Otherwise, since the position P [t] may largely enter the range affected by the end point passing speed Vg [i + j], the distance E is used to interpolate at least once.
Is regarded as an interpolation unit amount, and is set as a final upper limit speed Ul [t].
This processing can be executed by the function min (). Step S9: The process ends because the final upper limit speed Ul [t] is determined. As described above, the prefetching passing speed determining unit 5 sequentially checks the presence / absence of the influence based on the end point passing speed Vg of the non-interpolated end point G and the sum D of the path lengths up to the end point passing speed Vg. An upper limit speed Ul [t], which is an interpolation unit amount, which is equal to or lower than the end point passing speed Vg from at least the time before T time is determined.

The interpolation unit amount limiting unit 6 limits the command interpolation unit amount Uc [t] output by the interpolation unit amount calculation unit 4 by the upper limit speed Ul [t] output by the prefetch passage speed determination unit 5.
Specifically, the two are compared, and the smaller one is output to the smoothing filter 7 as the interpolation unit amount U [t].

FIG. 4 shows an example in which the machined shape shown in FIG. 3 is interpolated by the present apparatus. FIG. 3A is a diagram showing the upper limit speed Ul output by the prefetch passage speed determination unit 5 in a time series. t (G [1]) and t (G [2]) are the end points G
[1] is the time of passing near the end point G [2]. It is always below the permissible speed Vmax of the machine. As shown, t (G
[1]) The end point passing speed Vg from just before the time constant T of
Outputs [1]. The same applies to the end point G [2]. In the case of an arc block, the shape passing speed Vb [2] is output.
FIG. 3B is a diagram illustrating the magnitude of the velocity vector at the position P output by the shape interpolation unit 8 in a time series. However, this is the result when the command interpolation unit amount Uc is always larger than the upper limit speed Ul, and the interpolation unit amount U is always equal to the upper limit speed Ul. The speeds near the end points G [1] and G [2] are the end point passing speeds Vg [1] and Vg [2]. FIG. 3C is a diagram showing the magnitude of the acceleration vector, which is a change in the speed vector, in a time series. As shown in the figure, the acceleration is always equal to or lower than the allowable acceleration Amax of the machine.

As described above, according to the present apparatus, the passing speed V based on the allowable course normal direction acceleration is obtained.
Since the upper limit speed Ul which becomes equal to or lower than the passing speed V from the time T before the end point G at which the speed is to be reduced is less than the passing speed V, the interpolation unit amount input to the smoothing filter 7 for suppressing the acceleration in the course direction is limited. The resultant acceleration resulting from the interpolation is also suppressed to an allowable range. However, the processing efficiency is good because the operation is not stopped. Of course, since the present device outputs the position along the given shape, the velocity-dependent trajectory error is extremely small. Further, the interpolation unit amount limiting unit 6
Since the command interpolation unit amount Uc is only limited by the upper limit speed Ul, the operator can change the feed speed within the upper limit speed even during machining. The above description has been made by taking a machine tool that performs shape processing on the XY plane as an example, but the same applies to a machine tool having three or more axes. The same applies not only to a machine tool that performs shape processing, but also to a robot that needs to control a trajectory.

[0021]

As described above, according to the numerical controller of the present invention, the allowable acceleration of the machine and the allowable speed of the machine can be controlled without stopping at each end point even if the processing shape is constituted by minute line segments. It moves smoothly at the maximum speed not to exceed, and efficient machining can be realized. Further, the load and shock applied to the motor and the mechanical system can be reduced, and there is an effect that the processing accuracy and the durability of the machine are improved. Further, since the servo control is performed in accordance with the interpolation position obtained by performing interpolation along the given shape, accurate trajectory control can be maintained. further,
Since the operator can change the feed rate even during machining, it is possible to stop the machine in order to cope with a trouble that has occurred during machining, for example, and the operability does not decrease.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a numerical controller according to the present invention.

FIG. 2 is a flowchart showing an operation example of the apparatus of the present invention.

FIG. 3 is a diagram showing an example of a processing shape.

FIG. 4 is a diagram showing an effect of the device of the present invention.

FIG. 5 is a block diagram showing a configuration of an embodiment of a conventional numerical controller.

FIG. 6 is a diagram showing the effect of the conventional device.

[Explanation of symbols]

 2 Passing speed defining unit 5 Pre-reading passing speed determining unit 6 Interpolation unit amount limiting unit

Continuation of the front page (56) References JP-A-63-182707 (JP, A) JP-A-2-219107 (JP, A) JP-A-6-83430 (JP, A) JP-A-4-245505 (JP) , A) JP-A-7-191728 (JP, A) JP-A-5-73128 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05B 19/416, 19/4155

Claims (2)

(57) [Claims] A command is interpreted block by block, and a shape command is interpreted.
A numerical control device that generates a feed command and a path length, stores the same as execution data in an execution data buffer, and controls an operation position of a machine according to the stored execution data, wherein a path normal direction of a shape represented by the shape command is provided. A passing speed defining unit that defines a maximum passing speed at which the acceleration does not exceed the allowable acceleration of the machine, and stores the passing command as one of the execution data in the execution data buffer; and the shape command and the path length from the execution data buffer. Is read out block by block, and the shape represented by the shape command is shape-interpolated according to the smooth interpolation unit amount given for each interpolation cycle, and the remaining path length obtained by subtracting the smooth interpolation unit amount from the path length is sequentially output. A shape interpolating unit that reads out the feed command one block at a time in synchronization with the shape interpolating unit, An interpolation unit amount calculation unit that calculates a command interpolation unit amount by multiplying the path length and the passage speed by one block in synchronization with the shape interpolation unit, so that the passage speed becomes the passage speed from a predetermined time ago. An upper limit speed, a route length and a passing speed, a route length and a passing speed obtained by pre-reading an uninterpolated block, and a look-ahead passing speed determining unit that is generated based on the remaining route length; and the command interpolation unit. An interpolation unit amount limiting unit that limits the amount by the upper limit speed and outputs the same as an interpolation unit amount; and a smoothing filter that smoothes the sequentially given interpolation unit amount so as to follow a predetermined time and outputs the smoothed interpolation unit amount. And a numerical controller comprising: Wherein said passing rate is Ri Do from an end point passing speed which is limited at the end of the shape represented by the shape command shaped passage speed which is limited with respect to shape itself represented by shape command , Do not exceed the allowable acceleration
The numerical control device according to claim 1, wherein