JPH02185346A - Profile control method - Google Patents

Abstract

PURPOSE:To reduce projection shapes of the quadrant changing-over time by lost motion, by increasing the speed loop gain of a correction speed by detecting the profile direction of a feeding shaft being turned over. CONSTITUTION:A directional inversion detecting mechanism 28 stores the direction by receiving the feedback pulses PX, PY, PZ fed from the position detector provided on the servomotor of each feeding shaft, detecting the moving direction of the feeding shaft being turned over and outputting a gain control signal, while moving a preset lost motion part, actually the backrush amt. part. A gain control means 29 increases the loop gain of a correction speed VN by receiving this gain control signal. Thus, by increasing the speed loop gain of the profile correction speed VN projection shapes can be decreased to about 1/2 - 1/3 of the past.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tracing control method for machining a workpiece while tracing a model, and particularly to a tracing control method that reduces protrusions when switching quadrants due to lost motion. Regarding.

[Conventional technology]

When performing perfect circular cutting (machining that cuts while tracing a perfect circle) by tracing, if there is lost motion such as backlash in the machine, a protrusion shape will occur at the point where the quadrant changes. This is because during lost motion, even though the servo motor is rotating, the machine does not move, and as a result, the amount of displacement detected by the tracer head does not change, so the speed command to correct the displacement error also does not change. , the tracing response (VN response) was delayed, and a protrusion occurred on the workpiece when switching quadrants.

FIG. 4 is a diagram illustrating an example of a perfectly circular cross section processed by contouring. Workpiece cross section 1 has protrusions 2.3 when switching quadrants.
．． 4 and 5 are occurring.

[Problem to be solved by the invention]

The profiling feed axis normally forms a fully closed loop with the tracer head as the detector, and backlash compensation is not performed on the control device side (although statically the backlash movement is compensated for, the dynamic Generally, there is a state in which the machine does not move, so if there is backlash movement, a protrusion shape will occur on the workpiece.

The present invention has been made in view of these points, and it is an object of the present invention to provide a tracing control method that reduces the shape of a protrusion when switching quadrants due to lost motion.

[Failure to solve the problem]

In order to solve the above problems, the present invention performs a tracing calculation based on the stylus displacement signal detected by the tracer head and uses a tracing control method to control the feed rate of each axis, in which the tracing direction of the feed axis is reversed. detect that
A profiling control method is provided that is characterized by increasing the speed loop gain of the corrected speed.

[Effect]

When the direction of the profiling axis changes, the protrusion shape of the workpiece is reduced by increasing the speed gain of the profiling correction speed loop and moving the tracer head at high speed by a distance corresponding to the lost motion.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 3 is a diagram showing the relationship between the workpiece and the stylus in profile control. The stylus 7 provided at the tip of the tracer head moves at a composite speed (2) of the contouring correction speed component VN and the feed speed component VT according to the deviation. In reality, this composite velocity V is the velocity component Vx and vy of the X axis and Y axis, respectively.
and the X-axis and Y-axis are the velocities Vx and vy, respectively.
to move it. At point P of the model 6, the moving direction of the Y axis changes, and a protrusion 2 is generated on the workpiece as shown in FIG.

In order to reduce the size of this protrusion and improve the machining accuracy of the workpiece, a change in the moving direction of the Y-axis is detected and the velocity loop gain of the profile correction velocity VN is increased. This process will be explained based on a flowchart. FIG. 1 is a flowchart of the process of the profiling control method of the present invention. In FIG. 0, the numerical value following S indicates a step number.

[S1] Check whether the axis tracing direction has been switched, and if it has been switched, proceed to S2.

[S2] Check whether the axis has moved by the amount of lost motion such as backlash with respect to the axis whose direction has been reversed. If it has moved, proceed to S4; if it is moving, proceed to S3.

[S3] The moving direction of the axis has been reversed and is still within the range of lost motion, so multiply the speed loop gain (VN gain) for corrected speed calculation by a constant set in the system parameters to calculate the speed. Increase loop gain.

[S4] Since the movement of the lost motion is completed, the velocity loop gain of the corrected velocity VN is returned to its original value.

[S5] Calculate the tracing speed and execute axis movement.

The profiling control device executes this process at regular intervals and continues profiling control.

Next, a general configuration of a profiling control device for carrying out the present invention will be described. FIG. 2 is a functional block diagram of a profiling control device for implementing the present invention. Displacement synthesis means 2
1 synthesizes the displacement amounts ε8, 1, and ε2 detected from the stylus to obtain a composite displacement ε amount ε. The calculator 22 calculates the standard displacement amount ε. and the resultant displacement amount ε. The corrected velocity calculator 23 calculates a corrected velocity component VN perpendicular to the model surface from the above difference. The feed rate calculator 24 calculates a feed rate component VT horizontal to the model surface from the above difference.

The angle determining means 25 calculates the tracing angle from the displacement amount ε, ε, and ε2. The distribution means 26 outputs the output from the corrected speed VN and the feed rate 24 to each axis according to the output from the angle indexing means 25.

The gate 27 sends tracing speed commands Vx, Vy, Vz to each axis.
is output.

The direction reversal detection means 28 receives a feedback pulse P from a position detector such as a pulse coder provided on the servo motor of each feed axis.
It receives X, PY, and PZ, memorizes the direction, detects that the direction of movement of the feed axis is reversed, and outputs a gain control signal while moving by a preset lost motion amount (actually, backlash amount). Output. The gain control means 29 receives the gain control signal from the axial reversal detection means 28 and increases the loop gain of the corrected speed VN.The normal loop gain is about 30 to 50, but this is increased to 60 to 1.
Increase it to around 00. This value is determined experimentally based on the rigidity of the machine, cutting load, tracing speed, etc. The machine coordinate counter 30 counts the feedback pulses of each feed axis, outputs the machine position XSY, , Z, and displays this on the display device. indicate.

In this way, by increasing the velocity loop gain of the profiling correction velocity VN, the shape of the protrusion can be reduced to about 1/2 to 1/3 of the conventional one.

In the above description, the direction is detected using the feedback pulse from the position detector, but it may also be detected from the tracing speed commands Vx, Vy, and Vz for each axis.

〔Effect of the invention〕

As explained above, in the present invention, when the direction of the feed axis is reversed, the speed loop gain of the profiling correction speed is increased, so it is possible to reduce protrusions in the changed part of the quadrant, and to improve the machining accuracy of the workpiece. is improved.

[Brief explanation of the drawing]

Fig. 1 is a flowchart of processing of the profiling control method of the present invention, Fig. 2 is a functional block diagram of a profiling control device for implementing the present invention, Fig. 3 is a diagram showing the relationship between the workpiece and the stylus in profiling control, FIG. 4 is a diagram illustrating an example of a perfectly circular cross section processed by contouring. 24------------- Tracing speed calculation means 2
5・−・・−・・−・−Angle determining means 28・・−・
......Direction reversal detection means 29------
-1.Gain control means patent applicant Fanuc Co., Ltd. agent Patent attorney Takeshi Hattori-・・−−−−−−−・−−−−Work 2 to 5−・
−・−・−・−Protrusion 6−−1111・−・−・・−Model

Claims (5)

[Claims] (1) In the tracing control method, which performs tracing calculations based on the stylus displacement signal detected by the tracer head and controls the feed rate of each axis, a reversal of the tracing direction is detected and the speed loop gain of the correction speed is applied. A tracing control method characterized by increasing the . (2) The profiling control method according to claim 1, wherein the profiling correction speed loop gain is increased while the profiling axis moves by a distance corresponding to a preset lost motion. (3) The tracing control method according to claim 1, wherein the tracing direction is detected from a feedback pulse of a position detector coupled to a servo motor that controls the axis. (4) The tracing control method according to claim 1, wherein the direction of movement is detected from a command speed to a servo motor that controls the axis. (5) The profile control method according to claim 1, wherein the lost motion is a backlash amount.