JPS62226206A - Control system for synchronous position - Google Patents

Abstract

PURPOSE:To prevent the asymmetrical properties due to disturbance by feeding the position shifts of both master and slave axes back to each position control system. CONSTITUTION:A large arch-shaped column 11 of a machine tool, etc., contains foot parts 12 and 13 symmetrical to each other and ball screw shafts 14 and 15. These shafts 14 and 15 are driven by motors 16 and 17 respectively. The motors 16 and 17 are actuated by the position command value R to secure synchronism between shift positions C1 and C2 of both parts 12 and 13. When the synchronous positioning is carried out between both parts 12 and 13 through each of position control systems 1 and 2, the command value R is supplied to both systems 1 and 2 to obtain the outputs of both systems, i.e., the mutual differentials between positions C1 and C2. Then the compensation elements H1 and H2 of both systems 1 and 2 are applied to those differentials (C1-C2) and (C2-C1) to obtain the value of compensation. This value of compensation is fed back to the value R is both systems 1 and 2 respectively. Thus the constant responsiveness is secured to the value R.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a synchronous position control system, and is a control method for synchronously positioning the legs on both sides of a machine tool, etc., equipped with a movable structure such as a concave structure. Regarding the method.

[Background technology and its problems]

When driving a large concave column or the like in a machine tool or the like, for example, as shown in FIG. A motor 16.17 is connected to each of the ball screw shafts 14.15, and each motor 16.17 is driven according to the position command value.
．． 13 movement positions C1 and Cz are controlled by the same amount.

A conventional synchronous position control system is shown in FIG. In the same figure, 21
．． 22 is a position control system for each axis L4.15, and 23 is a compensation circuit. R is position command value, GI.

G2 is a transfer function for the position command value R in each position control system 21, 22 to the movement position c, , C2. H moves to 1 position C+, C! A compensation element of the compensation circuit 23 that works to eliminate the deviation of the P control, PI control, PI
D control etc. are used. That is, in this method, the two axes 14, 15 are divided into a master axis and a slave axis, and the movement position of the slave axis is controlled to match the movement position of the master axis.

With this configuration, if some disturbance (e.g. cutting load, friction, etc.) is applied to the master shaft and this causes the master shaft to shift its position, the rotor of the motor will rotate and the position will shift. If a disturbance occurs, the slave shaft side moves to compensate for the positional deviation, eliminating the positional deviation in both wheels.On the other hand, if a disturbance is applied to the slave shaft side, the master shaft side does not move. The slave shaft side uses its own disturbance suppression ability to eliminate positional deviations caused by disturbances. Therefore, with this type of control method, even if a machine with a symmetrical structure is created, the response of each control system to disturbance cannot be made symmetrical, so the mechanical response will be asymmetrical, and the final workpiece will also be worked asymmetrically. This will result in

This situation is shown in FIGS. 7(A) and 7(B). In other words, at points A and B on the machine that are symmetrical with respect to the central axis of the machine, if a disturbance F is applied in a stepwise manner to the master shaft side, the slave shaft side will move to compensate for the positional deviation. ,
The maximum displacement of the machine at that time is as shown in Fig. 7(A). On the other hand, if a step-like disturbance F of the same size is applied to point B on the slave axis side, the master axis side will hardly move, so the maximum displacement of the machine at that time will be as shown in Figure 7 (B).
become that way. In other words, since the cutting surface is asymmetrical, the cut surface of the workpiece to be machined is also asymmetrical.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a synchronous position control method that does not cause such conventional problems, that is, asymmetry due to disturbances.

[Means and actions for solving problems] Therefore,
The present invention aims to achieve the above object by eliminating the conventional distinction between a master axis and a slave axis and feeding back positional deviations on both axis sides to each position control system.

That is, in a system in which a position control system B is provided on both sides of a movable structure to move each side based on a position command value, and these two position control systems position both sides of the movable structure synchronously, both sides of the movable structure are The problem of asymmetry caused by disturbances is solved by determining the difference in the movement position of the position, applying a compensation element to this difference to determine a compensation value, and feeding back this compensation value to each position control system.

〔Example〕

FIG. 1 shows a first embodiment of the invention.

In the figure, R is a position command value, G + and G z are transfer functions, H+, to movement positions C+ and Cz with respect to the position command value R in the position control systems 1 and 2 on each axis side.

H2 is a compensation circuit 3+ for each position control system 1, 2.

3t compensation element.

First, the position command value R is input to each position control system 1, 2, and the output of each position control system 1, 2, that is, each movement position C+, C
mutual difference of z (C, -C,), (Cz Ct)
seek. Then, these differences (C, -Cz), (C
2-c+), the compensation element IN+ of each position control system 1.2,
Hz is applied to obtain a compensation value, and this is applied to each position control system 1.
．． E-back is performed to the position command value R of 2.

Therefore, in this method, the movement value ic of both position control systems 1.2
Since the difference between l and Cz, that is, the positional deviation, is fed back to the position command value R of each position control system 1.2, the responsiveness to the command value is the same, and the problem of asymmetry with respect to disturbance can be solved.

Therefore, this point will be explained based on FIG. 2, which is a diagram in which disturbance elements are added to FIG. 1. In the same figure, T.

T2 is the torque disturbance for each position control system 1.2, 1)+
, Di are transfer functions (D+ ``Ct
/T+, Dz -Ct /Tt), the position command value R and the disturbance T1. Position control system 1 for Tt,
The response C,,C, of 2 is expressed by the following equation.

C+ (R1TI, Tz) 1 + GI Hl + Gz Hzl
+G1 Hl +Q, triC2(R, TI, T
z) 1 + GI HI + Gz Hzl +
G I Hl + Gz Hz Therefore, the error E of the movement position C2 of the position control system 2 with respect to the movement position CI of the position control system 1 is expressed by the following formula % Formula % In this formula (3), the first term is the position command value The second term is the position error caused by the disturbance T to the position control system IG, and the third term is the position error caused by the disturbance T2 to the system 2.

For comparison, we found a similar formula for the conventional mask-slave method.
Set l = O, H, = H (' Since it becomes a thing again, CAI-GI R+ Dl TI...
・・・・・・・・・ (4) 1 +0g H1+Gz
It becomes H.

Usually, each position control system is configured to show the same response, so it can be regarded as GI'''Gz, Dr -Dz.

Also, if the system is configured so that each compensation element is the same, Hl"Hz will be obtained, and (1) to (3) 2 and (
Equations 4) to (6) are each converted as follows.

GA+= GI R+ Dr TI...
・・・・・・・・・・・・・・・ (4″)1+GI
Comparing Equation H (3°) and Equation (6'), Equation (3') is the same as Equation (6') with H" 2 H+. This simply doubles the gain of the compensation element. Therefore, it can be seen that if the gain of H is set to 1/2 of H, there is no difference in position error between the conventional system and the present system.

In addition, the stability of the system can be determined by examining the characteristic equation.

The characteristic equation of the conventional method is 1+-G, H=O, and in the present method, it is l +2C;I H,=O, and there is no difference for the same reason as above.

Next, let's examine the symmetry of both equations against disturbances. Now, if we consider the case shown in Figure 3, there is a disturbance FA at point A.
When , a disturbance of T is applied to the first axis (for example, on the position control system 1 side) and a disturbance of TzA is applied to the second axis (on the position control system 2 side). Here, if the command value is R, the displacements of the first and second axes are respectively C+(R, TIA, TlA)
, Cz(R, TIA, Txa). Also, when a disturbance F of the same magnitude is applied to a point B that is symmetrical to point A with respect to the central axis, a disturbance T4 is applied to the first axis and TzIl is applied to the second axis, but the structure of the machine is symmetrical. If the structure is Tll1=T2A, Tll1TZA. Therefore, the displacements of the first and second axes are each C+ (R9T
li, Txa) = C+ (R, TlA, TI
A), C2(R,71B,Tzs) = C2
(R, TZA, TIA).

Therefore, the difference ER between the displacement of C4 when disturbance F is applied to point A and the displacement of 02 when the same disturbance F8 is applied to point B is E R+ = CI (RlTIA, TzA)
C2 (11, TZA, TIA) - ○. Similarly, the difference ER between the displacement of 02 when disturbance F is applied to point A and the displacement of 01 when the same disturbance F is applied to point A is E Rz = C2 (R, TIA, TEA ) C
4(R, TZA, TlA)=0. That is, in this method, when a disturbance of the same magnitude is applied to a mechanically symmetrical position, the response of the control system for each axis is symmetrical.

On the other hand, when we examine the response of the conventional method to similar disturbances, we find that E Rs+ = CAl (R, TIA, TZA)
CA2(R,TZA,TIA)E RA2=C
A2 (R, TIA, TZA) - CAI (R, Ding ZA
, TIA). Therefore, in the conventional system, the responses to disturbances are equal only when the disturbances applied to both wheels are equal (T la = 72A).

FIG. 4 shows a second embodiment of the invention.

This one corresponds to the compensation elements H,,H! in FIG. Assuming that [■] is the same, the difference (CI
-c,) to obtain a compensation value by applying a compensation element H, and subtracting this from the position command value R of the position control system 1, while adding it to the position command value R of the position control system 2. be.

In addition, the compensation element H in FIGS. 1, 2, and 4
+, Hz, normal P control, PI control, P'l
D control etc. can be used.

〔Effect of the invention〕

As described above, according to the present invention, even when cutting a workpiece that is symmetrical with respect to the central axis, the workpiece can be made symmetrical without becoming asymmetrical.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a block diagram with disturbance elements added to Figure 1, Figure 3 is a diagram showing the maximum displacement when disturbance is applied to points Δ and B, which are symmetrical to the central axis in Figure 2, and Figure 4. is a block diagram showing a second embodiment of the present invention, FIG. 5 is a perspective view showing a position control system for a concave movable structure, FIG. 6 is a block diagram showing a conventional equivalent position control system, and FIG. is a diagram showing displacement when an external force is applied to points A and B that are symmetrical about the central axis in this method. 1.2...Position control system, R...Position command value, cl. C2... Movement position of each position control system, Do, Dz...
Torque disturbance, C,, C2...Transfer function to the movement position with respect to the position command value in each position control system, Hl. H,,H...Compensation element for each position control system.

Claims (2)

[Claims] (1) In a method in which position control systems are provided on both sides of a movable structure to move each side based on position command values, and both position control systems position both sides of the movable structure synchronously, both sides of the movable structure are 1. A synchronous position control system characterized in that a difference in movement position is determined, a compensation element is applied to this difference to determine a compensation value, and this compensation value is fed back to each position control system. (2) In claim 1, the differences between the two moving positions are determined, and each compensation value is determined by applying a compensation element for each position control system to each difference, and each compensation value is A synchronous position control method characterized by feeding back to each position control system.