JPS63189904A - Correcting system for circular orbit - Google Patents

Abstract

PURPOSE:To cut out a true circule at a high speed by inputting an arc command with a radius expressed by an equality I when it is defined that positional loop gain is Kp, the objective radius of a tool track is R is and a feeding angular speed is omega. CONSTITUTION:The coordinates Xe, Ye of a starting point and the coordinates Xc, Yc of a center are respectively inputted and a computing means 4 calculates a radius R from the input data on the basis of an equality II. Then, a feeding speed F is inputted and the means 4 calculates an angular speed omega=F/R from the previously obtained radius R and the feeding speed F. A corrected radius R1 is calculated on the basis of the equality I and R1conomegat and R1sinomegat are respectively set up in an X-axis function generating means 6 and a Y-axis function generating means 7. Then, the means 6, 7 respectively output X-axis and Y-axis command pulses to X-axis and Y-axis servo mechanisms 8, 9.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an arc command method in an NC device.

(Prior art) Conventionally, when an arc command is given to the positioning servo system to cut an arc with an NC machine tool, when the feed rate is high or the radius of the arc is small, the shape of the cut workpiece is not the same as the command. I knew from experience that the radius would not be as expected. Therefore, in order to obtain a circular arc with a commanded radius, a method has been adopted in which cutting is performed by keeping the feed rate low.

(Problems to be Solved by the Invention) The conventional arc command method described above not only cannot perform high-speed arc cutting, but also has the disadvantage that it requires repeated cutting and radius measurement to approach the desired shape. .

The present invention automatically corrects the radius and gives a circular arc command of the corrected t diameter to the servo system, thereby making it possible to cut a perfect circle as fast as the servo system allows. The purpose is to provide a method.

(Means for Solving the Problems) The circular trajectory correction method of the present invention uses a secondary positioning servo system that can be approximated by two primary servo systems, where the position loop gain is KP + the target radius of the tool path is R1, and the feed angular velocity is When ω, R,=RxFCL;7/ is characterized in that a circular arc command with a radius expressed as R,=RxFCL;7/ is input to the positioning servo system.

(Function) In a servo system where the velocity loop gain is set sufficiently larger than the position loop gain, the secondary system position loop can be approximated by two independent primary system position loops as shown in Figure 4. can do. Here, X+ (s)
, 31+ (s) , are the human power of the servo system X+
(t), 'I+ Laplace transform of (L), Xo(
S).

yo(s) are the outputs of the servo system xo(t) and y, respectively
Laplace transform of o(t), to II) I (S) * to p
y(S) is the position loop gain. As is clear from FIG. 4, the following equation holds.

From equation (+), the following equation holds true.

xo(s) = Mountain soup master Xt(S) Now, x, (t) = Rcosωt, y, (t) = R
sinωt, × at t<0. (t) = yo(t) =
By performing Laplace transform on X+(t) and 3F+(t) assuming 0, and further performing partial fraction expansion, the following equation is obtained.

xo (S) = f Senichi Oka Kou Kuchizai 酊Here, K □ (S), py (S) is a constant that does not depend on S, and □ is □, and if we perform the inverse Laplace transform, we get
×. (s) = 428x, (-ni,, 1), 11 units (ni,, cos ωL + ωsin ωt) 4←(1)C
p in O8ωt+, sinωL) The first term of both equations (4) is an unsteady solution and corresponds to a transient state, and converges to 0 at t→ω. Further, the second term is a steady solution and corresponds to a steady state. Therefore, when enough time has passed since the initial time 1=0, Xo(1)=Tzu-r(,, cos ωt+m5in
ωt). Normally, the position loop gains of the X and Y axes can be made equal by adjustment, etc., so this is the wing, 8. et al.

= .

Xo(1)-k(K pcosω as commandωsinωt
) Therefore, ×. (1)" + yo (t)" = e
−(7) From equation (6), output×a (t) −yo
The trajectory of (t) is RX K.

/JT21; It is a circular arc with a radius of 1-.

In other words, if the position gain is sufficiently large compared to ω, there is no problem since /J1fuku;1−→1, but if ω is large, the arc will have a radius smaller than the target radius R. It ends up. For example, in a positioning servo system where 1 pulse = 1 μ, = 507 sec, feed rate F = 1 m/
a+in, R= 10c- case ω= += 10'
X 1/60x 10-'rad/sec At this time,
/ FLT-Self = 0.9999944 and Rx O
,9999944=99999.44-, which is about 1
This causes pulse errors.

, = 507 sec, F = 1 m/sin,
For R= 1 cm, (13= 10' x 1
/60x 1G''''=5/3 rad/sec.

At this time, Kp/−rζη”T; V = 0.
999449 and Rx 0.999449=99
The radius becomes 94.49-, which is 5 pulses smaller.

Normally, the minimum interpolation distance (resolution) that can be controlled by command pulses
is the distance δ corresponding to one command pulse. therefore,
If R-Rx is /F-Work > a, the radius R is multiplied in advance by the correction factor FCη;1/, and "C
Rr = RX nQ]7/l.

By giving a circular arc command with radius H to the servo system, a circular arc with radius H can be realized at any angular velocity.

(Example) Next, an example of the present invention will be described with reference to the drawings.

Fig. 1 is a block diagram of an embodiment of the NC device to which the roundness correction method of the present invention is applied, Fig. 2 is a flow chart showing the operation of Fig. 1, and Fig. 3 shows the interpolation path of the tool machining end. FIG.

X-axis current position register 1, Y-axis current position register 2 and position loop gain register 3 each indicate the starting point 2 of cutting.
The coordinates of the three points xs, ymJ5 and position loop gain are
is held. The calculation means 4 calculates the coordinates of the starting point P×□y,
and position loop gain for each register 1.
From the coordinates (x (+, yc)) of the center pc of the arc of the feed rate F1 read from 2.3 and also input from the input means 5 and the position R (xm, ys) of the starting point P of the arc, the arc radius R1 Calculate the feed angular velocity ω, and the correction factor $/, and the corrected radius R, = RX (on month 7; , cosωt.

II, set sinωt. X-axis number generation means 6, Y
The inter-axis number generating means 7 are R and cosωL, respectively.

II, a command pulse proportional to sinωt is output to the X-axis servo mechanism 8 and the Y-axis servo mechanism 9 until the tool machining end reaches the end point pa (xa, y,). X-axis servo mechanism 8
, Y-axis servo mechanism 9 outputs an X-axis output and a Y-axis output, respectively.

Next, the operation of this embodiment will be explained.

First, start point coordinates (xs, ya), center coordinates (X6.ye
) are input respectively (step 21). The calculation means 4 calculates the radius "xm-xc" from these input data.
'1m-Yc is calculated (step 23).

Next, the feed rate F is input (step 24). The calculating means 4 calculates the angular velocity ω=F/R from the radius R and the feed rate obtained in step 23 (step 25), and further calculates the corrected radius R,=RxFLη;1/, step 26), R, cos ωt in the center number generation means 6
, R and sin ωt are respectively set in the Y-axis number generation means 7 (step 27). Then, the X-axis number generation means 6 and the Y-axis number generation means 7 output X-axis and Y-axis command pulses to the X-axis servo mechanism 8 and Y-axis servo mechanism 9, respectively (step 28).

〔Effect of the invention〕

As explained above, the present invention approximates the position loop of the secondary servo system with two primary position loops, and outputs the arc radius correction factor determined by analysis to the servo system as an arc command. By automatically calculating and giving a corrected radius arc command to the servo system before cutting, it is possible to cut a perfect circle at high speed within the speed gain range of the servo system.

[Brief explanation of the drawing]

Figure 1 shows an NCvt to which the circular orbit correction method of the present invention is applied.
A block diagram of an embodiment of W, FIG. 2 is a flowchart showing the operation of the device shown in FIG. 1, FIG. 3 is a diagram showing an interpolation path at the tool machining end, and FIG. FIG. 3 is a diagram showing two primary system position loops that approximate a servo system. 1-X-axis current position register, 2-Y-axis current position register, 3-position loop gain register, 4-arithmetic means, 5-human power means, 6-X-axis number generation means, 7-Y-axis number generation means , 8-X-axis servo mechanism 1, 9-Y-axis servo mechanism, pc, p,, p, - center, starting point and ending point, (
×. , yc) - center coordinates, (Xm, y,) - start point coordinates, (xs, ya) - end point coordinates, R - target radius of the tool path.

Claims (1)

[Claims] In a secondary positioning servo system that can be approximated by two primary servo systems, the position loop gain is K_p, the target radius of the tool path is R,
When the feed angular velocity is ω, R_1=R×√(K_p^
2+ω^2)/K_p A circular orbit correction method characterized by inputting a circular arc command with a radius represented by 2+ω^2)/K_p to the positioning servo system.