JP2733665B2 - Numerical control unit - Google Patents

Description

The present invention relates to a numerical control device such as a machine tool, and particularly to a position where a tracking error due to a tracking delay of a servo mechanism becomes a problem during machining according to a machining program. The present invention relates to a numerical control device that automatically determines and executes a dwell at that position.

(Prior Art) A servo system such as a machine tool driven based on a machining program by a numerical controller always has a following delay. For this reason, the curvature is increased. For example, in a portion that bends a corner at a right angle as shown in FIG. 3, the pulse distribution by the first block movement command is completed, and then the next block movement command starts immediately. Since the processing of the next block is started before the processing of the block is completed, the corner portion is rounded as shown by a dotted line in FIG.

To solve such problems: (1) Increase the position loop gain of the servo diameter as much as possible.

(2) A block for commanding a dwell is inserted between the first command block for processing a corner and the next command block in the processing program.

 And other measures have conventionally been taken.

FIG. 4 shows a functional block diagram of a conventional numerical controller when a dwell is programmed in a machining program. In the figure, a machining program 1 is led to a program analysis unit 5 via an input / output control unit 3 and analyzed by the analysis unit 5 block by block. When the analyzed block is a movement command, data of the movement amount and movement speed in each axis direction is created and output to the pulse distribution unit 70. The pulse distribution unit 70 calculates the movement amount (minute speed) per sampling time from the input data and outputs it to the servo control unit 11 to drive the motor 13. When the analyzed block is the block that instructed the dwell, the dwell is performed for the time set in the dwell processing unit 9, and the analysis of the next block is interrupted during that time.

(Problems to be Solved by the Invention) The above countermeasures are as follows. (1) When the position loop gain is increased, the followability is improved, but the maximum acceleration of the servo diameter increases in proportion to the gain,
The position loop gain cannot be increased too much because the impact on the mechanical system increases and causes the accuracy of the machine to deteriorate.

(2) When programming a dwell in a corner, a programmer who creates a machining program tracks the trajectory of the tool and determines whether or not a dwell is necessary according to the shape of the workpiece, and if so, an appropriate dwell time Must be set. All of this can be a huge burden on programmers. Whether the judgment is appropriate or not, productivity is reduced when the dwell time is set unnecessarily long, and processing accuracy is not improved if the dwell time is too short.

 And so on.

(Object of the Invention) The present invention has been made to solve the above problems, and an object of the present invention is to automatically determine a position where a dwell is required during execution of a machining program, and to appropriately determine the position where the dwell is required. An object of the present invention is to provide a numerical controller capable of executing a dwell for an appropriate time.

(Summary of the Invention) A numerical controller according to the present invention sequentially analyzes a machining program for each block by a program analysis unit, and calculates a moving amount in each axis direction and a feed speed in each axis from a commanded tool moving position and a tool feed speed. Numerical control device that creates the data of, calculates the movement amount in each axis direction for each sampling time based on the data created by the program analysis unit in the pulse distribution unit, and outputs the speed command pulse to the servo control unit, A storage unit that stores the values of the allowable acceleration (ACC _P ), the allowable position error (P _E ), and the position loop gain (W _O ) input as parameters, and the amount of movement per sampling time [minute speed] (SVC)
Prior to outputting the speed command pulse corresponding to the speed to the servo control unit, the minute speed (SVC) and the moving amount per sampling time [minute speed] (SVCO) output to the servo control unit in the immediately preceding sampling Of the acceleration (ACC) calculated from the difference between the acceleration and the allowable acceleration (ACC) stored as a parameter.
_P ) and a determination unit that determines whether or not a dwell is necessary, and a minute speed (SVCO) output to the servo control unit.
A calculation unit for calculating a required dwell time (t) as a function of a permissible position error (P _E ) and a position loop gain (W _O ); and a dwell unit for measuring a set time and performing a dwell. And when the determination unit determines that a dwell is necessary, the time for outputting a speed command pulse corresponding to the minute speed (SVC) to the servo control unit is delayed by a dwell time (t).

(Embodiment of the Invention) In the present invention, the numerical control device automatically determines a required position of the dwell without executing the dwell in the machining program, and executes the dwell at that position. This is done in two ways:

(1) Detect the position where each speed increases during tool movement.

(2) Dwell is performed at the detected position for a necessary time.

Dwell time is a constant value with processing accuracy [tolerance]
(P _E ). It is assumed that a position control servo system of a general machine tool responds to a position command with a temporary delay filter characteristic. That is, the relationship between the command and the response is represented by the following equation.

Here, P: machine position [mm], P _C : command position [mm], W _O : one loop gain [rad / sec], S: plasma operator.

P = P _C {1-exp (−W _O t)} If the allowable error is P _E | P _C −P | ≦ P _E | P _C −P | = P _C exp (−W _O t) | ≦ P _E The dwell time may be set so as to satisfy the equation.

An embodiment of a numerical controller according to the present invention will be described below with reference to FIGS. FIG. 1 is a functional block diagram of a numerical controller according to the present invention. In FIG. 1, a machining program 1 includes a program analysis unit 5 via an input / output control unit 3.
And analyzed by the analysis unit 5 block by block. When the analyzed block is a movement command, data of the movement amount and movement speed in each axis direction is created and output to the pulse distribution unit 71 of the pulse distribution processing unit 7. The pulse distribution unit 71 calculates a movement amount [minute speed] SVCα in each axis direction per sampling time to be output to the servo control unit 11 next from the input data, and outputs the value to the comparison determination unit 73. A value and a parameter obtained by calculating the acceleration ACC from the difference between the input value SVCα and the movement amount SVCO per sampling time currently output to the servo control unit 11 stored in the storage unit 19 in the comparison determination unit 73 The value of the allowable acceleration ACC _P stored in the storage unit 21 is compared, and when the value is smaller than the allowable acceleration ACC _P , the output permission signal EN
To the pulse distribution unit 71. When the value of the acceleration ACC is large, the dwell time calculation unit 75 sets the dwell time to the current speed SVCO.
Dwell execution unit 9 determined as a function of the position loop gain W _O stored in the parameter storage unit 21 and the allowable error P _E
Set as the dwell time. The dwell execution unit 9 performs dwell for a set time. After the set time has elapsed, the output permission signal EN is returned to the pulse distribution unit 71. The pulse distribution unit 71 stores the SVC as the SVCO in the storage unit 19 and
Is output to the servo control unit 11.

FIG. 2 is a flowchart showing details of the processing described above. In this figure, the analysis process is a process performed by the analysis unit 5 and is the same as the process performed in the conventional apparatus of FIG. The initialization process is a process that is performed only once when the system is initialized. The pulse distribution process is a process that is executed at regular time intervals by the pulse distribution processing unit 7 in FIG. 4. The processes from ST1 to ST7 determine the movement amount [minute speed] to be moved by one sampling for each axis. This is a process similar to the conventional process for calculating. Where SVCα, D
A subscript α such as ISTα represents an axis. For example, SVCα is SV
It means C _X , SVC _Y , SVC _Z. ST8 calculates the acceleration ACCα generated when the SVCα is output from the movement amount [minute speed] SVCα to be moved by one sampling and the movement amount [minute speed] SVCOα per sampling time currently output to the servo controller. This is the required step. ST9 is a step of obtaining the maximum value ACC _MAX of the acceleration in the ACCarufa. ST10
Is a step of determining that ACC _MAX proceeds to ST13 when compared with the allowable acceleration ACC _P input as the maximum value ACC _MAX and parameters of the acceleration ACC _MAX is less than the allowable acceleration ACC _P moves to ST11 when larger ACC _P . In ST11, the dwell time t is calculated according to the equation. From the formula, the dwell only needs to take the time until the difference between the current position of the axis at which the acceleration becomes maximum and the commanded position falls within the allowable value. Current between the commanded velocity component SVCOα being output to the servo control unit and the command position P _C alpha is There is a relationship.

From this, the dwell time t in ST11 is given by the equation Determined by

In ST12, the time obtained in ST11 is set as the dwell time, and the dwell is executed. ST13 after dwell ends
Move on to In ST13, SVCα is stored as SVCOα, and in ST14, SVC
α is output to the servo control unit.

(Effects of the Invention) As described above, according to the numerical controller of the present invention, (1) Since the dwell is automatically set by the numerical controller, the set position of the dwell and the dwell time are taken into consideration when a machining program is produced. Since there is no need, the burden on the log grammar is reduced.

(2) Since the dwell time is appropriately set as a function of the moving speed of the tool, the tolerance, and the position loop gain, the dwell time is not too long or too short, so that the productivity is improved and the machining accuracy is uniform. .

 And so on.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a numerical controller according to the present invention, FIG. 2 is a flowchart showing details of processing, FIG. 3 is a diagram showing an example in which a machining error occurs due to a delay in following a servo system, and FIG. FIG. 3 is a functional block diagram of the numerical controller of FIG.

Claims (1)

(57) [Claims] 1. A program analyzing unit sequentially analyzes a machining program for each block, and generates data of a moving amount in each axis direction and a feed speed in each axis from a commanded tool moving position and a tool feed speed, In the numerical control device that calculates the amount of movement in each axis direction for each sampling time based on the data created by the program analysis unit in the distribution unit and outputs a speed command pulse to the servo control unit, the allowable acceleration input as a parameter (ACC _P ), a storage unit that stores the value of the permissible position error (P _E ) and the position loop gain (W _O ), and servos the speed command pulse corresponding to the moving amount per minute [Velocity per minute] (SVC) Prior to output to the control unit, the difference between the minute speed (SVC) and the moving amount per sampling time [minute speed] (SVCO) output to the servo control unit in the immediately preceding sampling. Acceleration of the value obtained from (AC
C) and allowable acceleration stored as a parameter (ACC _P )
And a function of the minute speed (SVCO), the allowable position error (P _E ), and the position loop gain (W _O ) output to the servo control unit by comparing the value of the control unit with the value of the dwell. A calculation unit for calculating a dwell time (t) required as follows; and a dwell unit for measuring a time for a set time and performing a dwell, wherein the determination unit determines that a dwell is necessary. A numerical control device characterized in that the time for outputting a speed command pulse corresponding to SVC) to the servo control unit is delayed by a dwell time (t).