JPH04245307A - Numerical controller and acceleration/deceleration control method - Google Patents

Abstract

PURPOSE:To perform high-speed, high-accuracy machining under smooth deceleration control. CONSTITUTION:Movement data and a feed speed are supplied from a machining program 1. Acceleration alpha capable of reducing the tool feed speed at the movement start point of a block which commands a tool path below a feed speed commanded by the block is set previously with a parameter, etc. A determining means 5 determines the timing of the start of the reduction of the tool feed speed. A varying means 6 for the acceleration changes the acceleration alpha to new acceleration alpha1 matching the remaining distance of the tool path in the block by the processing timing of the machining program 1. The varied acceleration is supplied to an accelerating and decelerating means 2 to perform an accelerating and decelerating processing based upon the value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical control device, and more particularly to a numerical control device for controlling a machine tool that performs high-speed, high-precision machining.

0002

2. Description of the Related Art A numerical control system (CNC) can automatically machine a workpiece into a desired shape by moving a tool at a predetermined speed along a machining path instructed by a machining program. In particular, in machine tools that perform high-speed, high-precision machining, the pre-interpolation acceleration/deceleration function of the CNC is used to eliminate errors in the machining shape of a workpiece due to delays in acceleration/deceleration. The pre-interpolation acceleration/deceleration function is a function that performs acceleration/deceleration processing of the tool feedrate, which is executed at a predetermined processing cycle, before executing pulse distribution when the tool feedrate is program-controlled together with the tool path. This function applies acceleration/deceleration to the tangential speed for interpolation (pulse distribution).
Shape errors caused by interpolation can be reduced to zero. Therefore, when controlling a plurality of servo axes of a tool simultaneously, trajectory errors due to servo tracking delay can be effectively reduced by using the pre-interpolation acceleration/deceleration function together with the feedforward control.

In a conventional numerical control device, a constant acceleration value is set in advance in parameters, etc., and the amount of movement of each axis is calculated so that the tool feed rate is specified by the machining program of the block being executed. In addition, the timing to start deceleration is determined by monitoring the remaining distance of the previously read block or the remaining distance of the block being executed. In other words, the remaining distance to the end of the block (
That is, from the timing at which it is determined that the distance required for deceleration (number of pulses) has become less than the distance required for deceleration, a speed command is issued in which the speed is sequentially decelerated by a set constant speed (for example, .alpha.mm/sec). Then, the pulses that could not be ejected until the tool stops after deceleration is completed can be ejected again after the speed has been decelerated to zero, or the deceleration can be temporarily interrupted during deceleration until the target speed is reached. By discharging the tool, acceleration and deceleration processing of the tool feed rate was executed.

FIG. 6 is a diagram illustrating two conventional methods of deceleration processing. Here, the horizontal axis is the time axis, and the vertical axis is the speed axis. FIG. 6A shows a deceleration process in which the remaining pulses are discharged after deceleration, and FIG. 6B shows a deceleration process in which the deceleration is temporarily interrupted. Now, the speed is commanded at a constant speed F1 until time t=0, and in both cases, the moving distance until the end of deceleration is assumed to be L. In case (A), the speed at the end of deceleration is zero, and the speed is decelerated at a constant acceleration until time 8T, that is, by the set speed α. but,
Because of the time interval T defined by the speed determination calculation cycle, as long as this acceleration is fixed, it is not possible to set the timing of the start of deceleration so as to reliably eliminate the irregular movement distance after stopping. Also, in the case of (B),
Since the target speed at the end of deceleration is not zero, the four surplus pulses defined by the moving distance L are absorbed by the command speed after time 5T. For this reason,
Even if the vehicle decelerates from the deceleration timing t=0 at the set acceleration α based on the same moving distance L, the deceleration must be temporarily interrupted midway.

[0005]

[Problems to be Solved by the Invention] In the deceleration method in such conventional numerical control devices, acceleration processing immediately after deceleration,
Or it involves a temporary interruption during deceleration. for that,
By giving a shock to the mechanical system of a numerically controlled machine tool,
This has the problem of increasing the tool trajectory error. In particular, in the case of a servo system that uses feedforward control, when trying to follow acceleration/deceleration pulses,
Larger acceleration/deceleration pulses will occur, and the mechanical shock will be more severe.

[0006] The present invention has been made in view of the above points, and it is an object of the present invention to provide a numerical control device for performing smooth deceleration without causing such a shock during deceleration. Another object of the present invention is to provide an acceleration/deceleration control method that eliminates disturbances during deceleration when acceleration/deceleration is applied before interpolation.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a tool at the movement start point of the block that commands the tool path when programmatically controlling the tool path and tool feed rate from multiple blocks of the program. In a numerical control device that executes acceleration/deceleration processing of the tool feed rate based on a set acceleration that allows deceleration until the feed rate becomes equal to or less than a commanded feed rate, the tool feed rate is decelerated based on the set acceleration. The method is characterized by comprising a determining means for determining a start timing, and a changing means for changing the set acceleration to a new acceleration commensurate with the remaining distance of the tool path within the block based on the determined timing. A numerical control device is provided.

In addition, in the acceleration/deceleration control method in which acceleration/deceleration is applied before interpolation using this numerical control device, if the remaining distance of the pre-read block is less than the distance required for deceleration, the acceleration is adjusted to match the remaining distance of the block. There is also provided an acceleration/deceleration control method characterized by controlling the feed rate of a tool by decelerating the tool by changing the amount.

[0009]

[Operation] When deceleration is necessary, the optimum acceleration is newly determined based on the timing of the start of deceleration and the remaining distance at that time so that the acceleration during deceleration is constant. If you decelerate with the newly determined acceleration, all remaining distance will be lost at the end of deceleration.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing acceleration/deceleration control in the numerical control device of the present invention. The machining program 1 instructs the numerical control device to move data and feed speed. The feed rate is supplied to the acceleration/deceleration means 2 and subjected to acceleration/deceleration processing. For example, the tool feed rate is commanded at a speed applied with linear acceleration/deceleration. This tool feed rate and the movement data of the machining program 1 are supplied to the interpolation means 3, which determines the pulses to be distributed to each axis. Here, distribution pulses for two axes are given to the X-axis control means 41 and the Y-axis control means 42, respectively, to drive and control the respective axis motors Mx and My of the machine tool.

[0011] Here, the numerical control device has an acceleration α that can decelerate the tool feed rate at the movement start point of the block that commands the tool path according to the machining program 1 to below the feed speed commanded by the block. It is set in parameters etc. When the determining means 5 executes acceleration/deceleration processing of the tool feed rate based on this acceleration α,
Determine when to start reducing tool feed rate. Reference numeral 6 denotes an acceleration changing means, which changes the acceleration α to a new acceleration corresponding to the remaining distance of the tool path within the block at each processing timing (T) of the machining program 1 based on the timing determined by the determining means 5. Change to α1. The changed acceleration is given to the acceleration/deceleration means 2, and acceleration/deceleration processing is executed based on the value.

FIG. 2 is a diagram illustrating a state of deceleration caused by a new acceleration α1 that has been changed. The horizontal axis is the time axis, and the vertical axis is the speed axis. Now, the speed is commanded at a constant speed F1 until time t=0, and the speed at the end of deceleration is F1.
The moving distance until the speed is reduced to 2 is assumed to be L, which is the same as in the case of FIG. In the present invention, the remaining distance L by time t=9T
The tool is decelerated by a new acceleration α1 that can discharge all of the deceleration, and therefore the tool being decelerated is controlled to move at a constant acceleration state. Of course, even if the speed at the end of deceleration is zero, all speed pulses have been emitted before the tool stops, so there is no need to issue a movement command to adjust the remaining distance after the tool has stopped. is necessary.

[0013]Although linear acceleration/deceleration is explained here, the same applies generally to exponential acceleration/deceleration or bell-shaped acceleration/deceleration. However, compared to linear acceleration/deceleration, the relationship between remaining distance and speed is more complicated, and it is unavoidable that the load on the calculation capacity of the numerical control device becomes greater. Also, depending on the moving distance, the new acceleration α1 may match the parameter-set acceleration α. Further, the deceleration at 9T at the end of deceleration does not necessarily match α1. Furthermore, here the speed is set for each processing timing (T) based on the new acceleration set for each program block, but if deceleration continues at the specified speed across multiple blocks for,
The acceleration set by pre-reading the machining program can be used.

FIG. 3 is a flowchart illustrating the procedure of deceleration control in pre-interpolation acceleration/deceleration. In the figure, the number following S indicates the step number. Note that this deceleration control processing is a part of the acceleration/deceleration control processing steps described below, and is executed at each processing timing (T) described above.

[S1] Here, conditions for starting deceleration control are determined. That is, it is determined whether the remaining distance of the previously read block is less than the distance required for deceleration, and if it is determined that deceleration is to start, the process proceeds to step 2. [S2] When deceleration is required, a new acceleration α1 is calculated at which the remaining distance of the previously read block or the remaining distance of the currently executed block is completely discharged at the end of deceleration. [S3] The old acceleration α set in advance as a parameter is saved, and the newly calculated acceleration α1 is commanded to the acceleration/deceleration means 2. [S4] Start deceleration at the calculated acceleration α1. [S5] If it is determined in step 1 that deceleration has not started, that is, deceleration is already in progress, the process proceeds to step 5, where it is determined whether or not deceleration control has ended. If it is determined that the vehicle will continue to decelerate, the process will proceed to step 4, where the vehicle will further decelerate at an acceleration α1. [S6] When the deceleration control ends, the saved acceleration α is restored.

FIG. 4 is a flowchart outlining the processing procedure for acceleration/deceleration control in the numerical control device of the present invention. Here, the flow of ITP processing for each cycle (ITP cycle) defined by the calculation speed of the processor used and the flow of preprocessing for this ITP processing will be explained separately.

On the ITP processing side, a routine is executed that determines the speed using an ITP interrupt with a cycle of, for example, 8 msec, and instructs the control means of each axis to distribute pulses. On the other hand, on the preprocessing side, a routine is executed that decodes the machining program and calculates the data necessary for its execution. That is,
[S11] Read the NC program from the NC tape or memory, and decode the G code program and part program necessary for speed determination contained therein. [S12] Processing necessary for deceleration control is executed according to the decoded program. That is, the speed of each block and the remaining distance required to determine the timing to start deceleration are calculated. The calculated results are passed to the ITP processing routine along with data in an executable format necessary for the ITP processing.

[S13] Di such as the feed speed override signal, single block stop signal, feed hold signal, and reset signal is monitored to obtain a signal corresponding to the actual speed. [S14] Acceleration/deceleration is determined based on signals based on the preprocessing data and input data, and the speed is determined. At the end of this step, the deceleration control routine shown in FIG. 3 is executed to determine a new acceleration α1 suitable for the remaining distance during deceleration control. [S15] According to the speed data determined in step S14, an interpolation calculation is performed to determine distribution pulses for each axis. [S16] An output pulse that instructs the control means of each axis to receive the interpolation result and a signal that informs the internal state of the NC or a signal Do that controls the machine are output.

The above description has been about setting a new acceleration to eliminate disturbances in speed changes during deceleration control, but this can be applied not only to deceleration but also to acceleration. However, in general, excess pulses during acceleration can be absorbed during deceleration, and in the current state of linear acceleration/deceleration control, there is little need to intentionally change the acceleration.

FIG. 5 is a hardware block diagram showing the overall configuration of the numerical control device (CNC) of the present invention. The processor 11 executes the above-mentioned acceleration/deceleration processing of the tool feed rate according to a system program stored in the ROM 12, and also controls the entire numerical control device. ROM1
2 uses EPROM or EEPROM. A DRAM is used as the RAM 13, and various data are stored therein. A machining program 14a is stored in the nonvolatile memory 14.
, parameters, etc. are stored and a battery-backed CMOS or the like is used, so the contents are retained even after the numerical control device is powered off. Also, non-volatile memory 1
4 also stores parameters such as the set acceleration α.

The PMC (Programmable Machine Controller) 15 receives commands for the M function, S function, T function, etc., decodes and processes the commands using a sequence program 15a, and outputs an output signal for controlling the machine tool. In addition, it receives limit switch signals from the machine side or switch signals from the machine operation panel, processes them in the sequence program 15a, and outputs output signals to control the machine side. Signals necessary for the numerical control device are sent via the bus 25 to the RAM 13 and read by the processor 11.

The graphic control circuit 16 converts the data stored in the RAM 13, such as the current position and amount of movement of each axis, into a display signal and sends it to the display device 16a, which displays it. As the display device 16a, a CRT, liquid crystal display, or the like is used. The keyboard 17 is used to input various data.

The axis control circuit 18 receives a position command from the processor 11 and outputs a speed command signal for controlling the servo motor 20 to the servo amplifier 19. The servo amplifier 19 amplifies this speed command signal and drives the servo motor 20. A pulse coder 21 that outputs a position feedback signal is coupled to the servo motor 20. pulse coder 2
1 feeds back a position feedback pulse to the axis control circuit 18. In addition to the pulse coder 21, a position detector such as a linear scale may be used. These elements are required for the number of axes, but since the configuration of each element is the same, only one axis is shown here.

The input/output circuit 22 exchanges input/output signals with the machine side. In other words, the limit switch signal on the machine side,
The PMC 15 receives the switch signal from the machine operation panel and reads it. It also receives an output signal from the PMC 15 for controlling a pneumatic actuator, etc. on the machine side, and outputs it to the machine side.

The manual pulse generator 23 outputs a pulse train for precisely moving each axis in accordance with the rotation angle, and is used to precisely position the machine. Manual pulse generator 23 is usually mounted on a machine operation panel. In the figure, a spindle control circuit, a spindle amplifier, a spindle motor, etc. for controlling the spindle are omitted. Further, although there is one processor here, a multi-processor system using a plurality of processors can be used depending on the system.

[0026]

[Effects of the Invention] As explained above, by eliminating disturbances during deceleration, the numerical control device of the present invention can perform smooth machining without giving shocks to the mechanical system due to acceleration and deceleration. It becomes possible. Therefore, according to the numerical control device of the present invention, it is possible to accelerate and decelerate the tool feed rate of the machine tool, eliminate errors in the machining shape of the workpiece under program control, and perform high-speed, highly accurate machining.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing acceleration/deceleration control in a numerical control device of the present invention.

FIG. 2 is a diagram illustrating a state of deceleration due to a new acceleration α1.

FIG. 3 is a flowchart illustrating a procedure for deceleration control in pre-interpolation acceleration/deceleration.

FIG. 4 is a flowchart outlining a processing procedure for acceleration/deceleration control.

FIG. 5 is a hardware block diagram showing the overall configuration of a numerical control device (CNC) of the present invention.

FIG. 6 is a diagram illustrating two conventional methods of deceleration processing.

[Explanation of symbols]

1. Machining program 2 Acceleration/deceleration means 3 Interpolation means 41 X-axis control means 42 Y-axis control means 5.Decision means 6. Means for changing acceleration

Claims (3)

[Claims] Claim 1: When programmatically controlling the tool feed rate along with the tool path from multiple blocks of the program, the tool feed rate at the movement start point of the block that commands the tool path can be decelerated until it becomes equal to or less than the commanded feed speed. In a numerical control device that executes acceleration/deceleration processing of the tool feed speed based on a set acceleration, a determining means for determining a timing to start decelerating the tool feed speed based on the set acceleration, and the determined timing. A numerical control device comprising: changing means for changing the set acceleration to a new acceleration commensurate with the remaining distance of the tool path within the block based on the above. 2. The acceleration/deceleration processing of the tool feed rate is performed at a predetermined processing cycle and for a plurality of drive means of the tool.
2. The numerical control device according to claim 1, wherein the control is performed before performing pulse distribution. 3. An acceleration/deceleration control method in which the numerical control device according to claim 1 applies acceleration/deceleration before interpolation,
Acceleration/deceleration characterized in that when the remaining distance of the read-ahead block is less than the distance required for deceleration, the acceleration is changed to an amount commensurate with the remaining distance of the block to perform deceleration and control the feed rate of the tool. Control method.