JP3394121B2 - Numerical control unit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of numerical control axes, and stores in advance the positions to be controlled in each control cycle of each numerical control axis to be controlled. In addition, while controlling each numerical control axis according to the position that should be in each control cycle,
The present invention relates to a numerical control (hereinafter, referred to as NC) device capable of changing a feed rate by changing a feed rate during a processing operation. 2. Description of the Related Art Normally, an NC device controls each control target axis in accordance with a commanded machining program. That is, N
The C device obtains the position of each control cycle of the control target axis by interpolation from the G code command indicating the locus indicated in the machining program, the F code command indicating each feed speed, and the target position command of each control target axis. Further, acceleration / deceleration processing is performed to enable a smooth operation with respect to the interpolation position obtained by calculation, and the motor is controlled so as to sequentially perform positioning at the position obtained by performing acceleration / deceleration processing. A configuration diagram of an example of such an NC device will be described with reference to FIG. In the example of FIG. 7, two axes X and Z are provided as control target axes. The program analyzing unit 31 sequentially reads out the machining programs PR from the program storage unit 30 one block at a time, analyzes and analyzes the G code command, the F code command, the target position command of each axis to be controlled, etc. Is generated and sent to the function generator 32. The function generator 32 calculates G
With reference to data PD such as a code command, an F code command, and a target position command for each controlled axis, the position of each controlled axis in each control cycle is interpolated. Here, the interpolation calculation calculates the moving distance per control cycle time from the control cycle time and the feed rate commanded by the F code command, and calculates the travel distance per the command code by the G code command until it reaches the commanded target position. , The positions of the control target axes separated by the movement distance per control cycle time are sequentially calculated. Function generator 3
The position of each control target axis, which has been subjected to the interpolation calculation in step 2, is transmitted to the X-axis acceleration / deceleration means 33 each time the clock signal CL is sent from the control clock generator 1, and to the Z-axis interpolation data IZ. Is transferred to the Z-axis acceleration / deceleration means 34. The X-axis acceleration / deceleration means 33 creates command data CX obtained by smoothing the X-axis interpolation position data IX and transfers it to the X-axis motor control unit 9. The X-axis motor control unit 9 controls the X-axis motor in accordance with the command data CX. A command MX to be controlled is created to control the X-axis motor. Further, the Z-axis acceleration / deceleration means 34 creates command data CZ obtained by smoothing the Z-axis interpolation position data IZ and transfers the command data CZ to the Z-axis motor control unit 10. A command MZ for controlling the motor is created to control the Z-axis motor. [0003] Further, many NC apparatuses have a feed rate function as a function of changing a feed rate instructed by a machining program PR during execution of a machine operation. This feed rate function reads the feed rate change ratio FR commanded by an external switch or the like into the function generating unit 32 via the feed rate reading unit 2, and the function generating unit 32 reads the moving distance per control cycle time. Feed rate change rate F
This is realized by calculating the distance multiplied by R and calculating the positions of the control target axes separated by the calculated distance on the trajectory specified by the G code command. Here, the control cycle can be shortened as long as the interpolation calculation and the acceleration / deceleration processing are simple processes that are completed in a short time. Now, when processing a shape (for example, a cam shape) that cannot be expressed by a simple function, and when the processing distance is relatively limited and high-precision processing is required, interpolation calculation processing and acceleration / deceleration are performed in advance. There is an NC apparatus that performs a sequential positioning process in accordance with a command position for each control cycle in which the process is performed. In such an NC device, a storage device for storing a large amount of command position data is required. However, since there is no need to perform interpolation calculation processing and acceleration / deceleration processing for each control cycle, the control cycle can be shortened. In addition, shortening the interpolation interval enables high-precision machining. FIG. 8 is a configuration diagram of an example of such an NC device.
And will be described. As in the example of FIG. 7, two axes X and Z are provided as control target axes. The interpolated data storage unit 7 stores the command positions of the control target axes which have been subjected to interpolation calculation processing and acceleration / deceleration processing for each control cycle by an external device (not shown) in advance. Each time the control clock CL is transferred from the control clock generator 1, the transfer unit 6 reads, from the interpolated data storage unit 7, the command position PC of each control target axis that has undergone interpolation calculation processing and acceleration / deceleration processing for each control cycle. The reading and the X-axis command position CX are only sequentially transferred to the X-axis motor control unit 9 and the Z-axis command position CZ is only sequentially transferred to the Z motor control unit 10, and the processing to be performed in each control cycle is small, and the control cycle is shortened. High precision processing is possible by shortening the interpolation interval. [0006] However, such an NC device cannot use the feed rate function that is possible with the general NC device shown in FIG. In order to change the feed rate during machine operation, an interpolation process must be performed during machine operation.
This is because the same interpolation processing as that of the C device is performed, and the control cycle cannot be shortened. Therefore, in such an NC device, a highly-completed machining program and interpolated command position data can be machined with high accuracy with little error. Each time the feed rate is changed, a huge amount of interpolated data must be re-created by an external device, which is very troublesome. The present invention has been made in view of the circumstances described above, and an object of the present invention is to store in advance the positions that should be in control cycles of a plurality of numerical control axes to be controlled, and to store the positions in each control cycle. N to control each numerical control axis according to position
An object of the present invention is to provide an NC apparatus having a feed rate function that does not cause an excessive increase in processing time and suppresses the occurrence of errors in the C apparatus. SUMMARY OF THE INVENTION The present invention has a plurality of numerical control axes, and for each of the numerical control axes to be controlled, a position to be present in each control cycle of the numerical control axis is determined in advance. A feed rate command for instructing a speed change rate of the plurality of numerical control axes in the numerical control device for controlling the numerical control axes according to a position that should be in each control cycle for each of the numerical control axes. Means, virtual control cycle calculating means for multiplying the control cycle by a speed change ratio commanded by the feed rate command means to calculate a virtual control cycle, and the virtual control cycle calculated by the virtual control cycle calculating means A virtual control cycle integrating means for integrating the virtual control cycle, a position to be stored for each control cycle of the numerical control axis, the virtual control cycle integration means, Actual control position calculating means for calculating the position of the numerical control axis for each control cycle from the virtual control cycle integration time integrated by the means, and the actual control position calculating means for each numerical control axis. Axis control means for controlling the numerical control axis according to the position of the numerical control axis is achieved. Further, a feed rate adjusting means for smoothing a temporal change of a speed change rate instructed by the feed rate instructing means is provided, and the virtual control cycle calculating means sets the speed change rate to the speed change rate smoothed by the feed rate adjusting means. This is more effectively achieved by calculating the virtual control cycle by multiplying the control cycle. In the present invention, the feed rate command means receives an external feed rate command as a speed change rate, and the virtual control cycle calculation means calculates a virtual control cycle from the control cycle and the speed change rate. The virtual control cycle integration means calculates the virtual control cycle integration time by integrating the virtual control cycle, and the actual control position calculation means calculates the command position of each control axis which should be in each control cycle and the virtual control cycle. The position of each numerical control axis for each control cycle is calculated from the accumulated time and the axis control means controls each numerical control axis according to the position of each numerical control axis for each control cycle calculated by the actual control position calculation means. I do. For this reason, the position of each numerical control axis that should be in each control cycle is stored in advance, and even in the NC device that controls each numerical control axis in accordance with the position that should be in each control cycle, excessive processing time is required. The feed rate can be changed by the feed rate command without causing the increase in the feed rate. Further, the feed rate adjusting means is:
Since the virtual control cycle is calculated by smoothing the external feed rate command and referring to the smoothed speed change ratio, it is possible to perform a smooth operation even for a rapid speed change command. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same components as those of the conventional example shown in FIGS. 7 and 8 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a configuration diagram showing an embodiment of an NC grinding machine to which the NC device according to the present invention is applied. In the present invention, the feed rate reading unit 2 reads a feed rate command from the outside (not shown) in synchronization with a clock CL generated for each control cycle from the control clock generating unit 1 and feeds the feed rate command as a speed change rate FR. It is sent to the rate control unit 3. The feed rate adjustment controller 3 creates a smoothed speed change ratio FS obtained by smoothing the speed change ratio FR and sends it to the virtual control cycle calculator 4. The virtual control cycle calculation unit 4 calculates a virtual control cycle VT by multiplying the control cycle fixedly determined by the NC device by the smoothing speed change rate FS, and sends it to the virtual control cycle integration unit 5. The virtual control cycle integration unit 5 calculates the virtual control cycle integration time IVT by integrating the virtual control cycle VT, and sends the virtual control cycle integration time IVT to the data transfer unit 6 and the actual command position calculation unit 8. The data transfer unit 6 reads the necessary data PC from the interpolated data storage unit 7 with reference to the virtual control cycle integration time IVT and sends it to the actual command position calculation unit 8. 6
Command position (X-axis data CX and Z-axis data CZ) from data PC and virtual control cycle integration time IVT
Is calculated, and the X-axis data CX is sent to the X-axis motor controller 9.
The Z-axis data CZ is transferred to the Z-axis motor control unit 10, respectively. Next, a feed rate reading section 2, a feed rate adjustment control section 3, a virtual control cycle calculation section 4, a virtual control cycle integration section 5, a data transfer section 6, an actual command position calculation, which are main parts of the present embodiment. The detailed operation in the unit 8 is shown in the flowchart of FIG. 2, FIG. 3 showing the temporal change of the feed rate FR, FIG. 4 showing the temporal change of the smoothing speed change ratio FS, and the temporal change of the virtual control cycle integration time IVT. 5 and FIG. 6 illustrating a method of calculating the actual command positions CX and CZ. First, the feed rate reading unit 2 reads a feed rate (speed change rate) FR from the outside in each control cycle (step S1). FIG. 3 shows that the feed rate (speed change rate) FR read from the outside is 100% (1) to 50% when the time TS has elapsed from the start of the axis operation.
(0.5) is shown. Next, the feed rate adjustment controller 3 smoothes the temporal change of the feed rate (speed change rate) FR, and calculates a smoothed speed change rate FS (step S2). As the smoothing method, various known methods such as a moving average process can be considered, but a detailed description is omitted because it is not directly related to the present application. FIG. 4 shows the smoothing speed change rate F
S indicates a temporal change of S. In a section from the time point TS to a time point TE at which a predetermined time constant elapses, 100%
The smoothing speed change ratio FS is smoothly reduced from (1) to 50% (0.5). Next, the virtual control cycle calculation section 4 multiplies the smoothing speed change rate FS by the control cycle CT unique to the control device to calculate a virtual control cycle VT according to the following equation (1) (step S3). VT = FS * CT The virtual control cycle integration unit 5 integrates the virtual control cycle VT to calculate a virtual control cycle integration time IVT (step S4). FIG. 5 shows a temporal change of the virtual control cycle integration time IVT. Even in the same control cycle CT, the virtual control cycle VT is changed to VT1, VT2, VT3 by multiplying the smoothing speed change rate FS. , The virtual control cycle integration time IVT correspondingly
Also, the rate of increase changes as IVT1, IVT2, and IVT3. The data transfer section 6 reads out the interpolated data PC corresponding to the virtual control cycle integration time IVT from the interpolated data storage section 7 (step S5). The interpolated data storage unit 7 stores the interpolated data, that is, the position P where each numerical control axis (X axis and Z axis in this example) should be in each control cycle.
Cn is stored corresponding to each control cycle (control cycle integration time) tn, and data to be read is selected assuming that the virtual control cycle integration time IVT is equal to the control cycle integration time tn. Here, when the virtual control cycle integration time IVT is not an integral multiple of the control cycle CT, there is no corresponding interpolated data. In that case, however, the control cycle integration times before and after the virtual control cycle integration time IVT are not included. Read the corresponding interpolated data. That is, when the following equation 2 holds, the control cycle integration time tn = CT * n and tn + 1 = CT * (n +
Both the interpolated data PCn and PCn + 1 corresponding to 1) are selected and sent to the actual command position calculating unit 8. CT * n <IVT <CT * (n + 1) n: integer Next, in the actual command position calculating section 8, the virtual control cycle integration time IVT and the interpolated data transferred from the data transferring section 6 are calculated. The actual command positions CX and CZ are calculated from the PC (step S6). When the virtual control cycle integration time IVT is an integral multiple of the control cycle CT in the actual command position calculator 8, the interpolated data PC is used as the actual command positions CX and CZ. Otherwise, as described above, the interpolated data PCn, PCn + 1 corresponding to the control cycle integration times before and after the virtual control cycle integration time IVT, as described above.
Then, the actual command position C is calculated by proportional distribution from the fractional time OD obtained by dividing the virtual control cycle integration time IVT by the control cycle CT, and the control cycle CT. The actual command positions C calculated with respect to the X axis and the Z axis using Equation 3 below are CX and CZ, respectively. C = PCn + ((PCn + 1) -PCn) × OD / CT The X-axis motor controller 9 controls the X-axis motor and the Z-axis motor controller 10 controls the Z-axis motor according to the actual command positions CX and CZ. Are respectively controlled (step S7). The above steps S1 to S7 are executed for each control cycle. FIG. 6 is a diagram for explaining a method of calculating the actual command position C, where tn is the n-th control cycle integration time and PCn
The command data of each numerical control axis which should be at the control cycle integration time tn stored in the interpolated data storage unit 7 is
n indicates the actual command position calculated by the actual command position calculator 8. In the example of FIG. 6, the virtual control cycle at the control cycle integration time tn + 1 is CT1, and the virtual integration time integration time is IV.
Since T1 and tn <IVT1 <tn + 1, the actual command position calculation unit 8 includes the control cycle integration times tn and tn +
1 is sent, and the actual command position calculator 8 calculates X according to the above equation (3).
The actual command positions CX and CZ with respect to the axis and the Z axis are calculated. Here, if the feed rate remains unchanged at 100%, the position PC is added to the control cycle integration time tn + 3.
Control is performed so as to be at n + 3. For example, when the feed rate is changed to 50% in the control cycle integration time tn as described above, the position at the control cycle integration time tn + 3 is controlled so as to be at the position Cn + 3. This means that the feed speed has been reduced. As described above, according to the present invention, even in the NC apparatus which controls each numerical control axis based on the interpolated data on which the interpolation acceleration / deceleration processing has been performed, the feed rate is changed during the machining operation. By doing so, it is possible to change the feed speed. Also, even when the feed rate is suddenly changed, the speed change becomes smooth due to the smoothing, and no load is imposed on the machine. The arithmetic processing is also simple and does not impose a significant burden on the processing time of the control device. Further, even if the feed speed is changed, no error equal to or larger than the shape error generated by the linear approximation to the command data is generated, and high-accuracy machining can be maintained. Further, since the method of the present invention can perform processing independently for each control axis, there is also an advantage that even if the number of control axes increases, distributed processing can be easily performed by a plurality of control devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an NC grinding machine to which a numerical controller according to the present invention is applied. FIG. 2 is a flowchart illustrating an operation example of the numerical controller according to the present embodiment. FIG. 3 is a diagram showing a temporal change of a feed rate in the present embodiment. FIG. 4 is a diagram showing a temporal change of a smoothed speed change ratio in the embodiment. FIG. 5 is a diagram showing a temporal change of a virtual cycle integration time in the embodiment. FIG. 6 is a diagram illustrating a correspondence between interpolated data and an actual command position in the present embodiment. FIG. 7 is an example of a block configuration diagram of an NC grinding machine to which a conventional NC device having a feed rate function is applied. FIG. 8 shows a conventional NC controlled based on interpolated data.
It is an example of the block block diagram of the NC grinder to which the apparatus is applied. [Description of Signs] 1 control clock generation unit 2 feed rate reading unit 3 feed rate adjustment control unit 4 virtual control cycle calculation unit 5 virtual control cycle integration unit 6 data transfer unit 7 interpolated data storage unit 8 actual command position calculation unit 9 X-axis motor control unit 10 Z-axis motor control unit 30 Program storage unit 31 Program analysis unit 32 Function generation unit 33 X-axis acceleration / deceleration means 34 Z-axis acceleration / deceleration means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05B 19/18-19/46 B23Q 15/00-15/28

Claims (1)

(57) [Claims] [Claim 1] It has a plurality of numerical control axes and is an object to be controlled.
For each of the numerical control axes, the position that should be in each control cycle of the numerical control axis is stored in advance, and for each of the numerical control axes , the numerical control axis is controlled according to the position that should be in each control cycle. In the numerical control device, a feed rate command unit that commands a speed change ratio of the plurality of numerical control axes, and a virtual control period is calculated by multiplying the control period by a speed change ratio commanded by the feed rate command unit. Virtual control cycle calculation means, virtual control cycle integration means for integrating the virtual control cycle calculated by the virtual control cycle calculation means, and the numerical control system stored in advance for each of the numerical control axes.
Actual control position calculating means for calculating the position of the numerical control axis for each control cycle from the position that should be at each control cycle of the control axis and the virtual control cycle integration time integrated by the virtual control cycle integrating means; Axis control means for controlling the numerical control axis in accordance with the position of the numerical control axis calculated by the actual control position calculating means for each of the numerical control axes .