JPS63250715A - Non-linear friction compensating system for servo system - Google Patents

Abstract

PURPOSE:To suppress an abnormal response and to smoothly change a kinetic direction by monitoring a quadrant switching time during the working of a contour, generating a compensating function value for compensating an abnormal response at the time of detecting the switching time and adding the generated value to an input command value in a servo system. CONSTITUTION:A deviation counter 1 computes a deviation between an inputted position command value Xi and an output value from a position encoder 8 for detecting the position of an actuator 6, outputs the deviation value, detects the time when the command value Xi or the deviation value is converted from a positive or a negative to a negative or a positive, i.e. a switching point of a circular arc, and outputs a switching detecting signal. A compensating function generating part 2 previously includes a compensating function formula, and when its parameter is set up and the switching detecting signal is inputted, generates and outputs a compensating function value. An addition value 3 adds the output of the counter 1 to that of the generating part 2 and a D/A converter 4 D/A converts the added output. The analog command value is inputted to a servo amplifier part 5 to control the actuator 6.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a processing control method for a numerical control device that controls contour processing of a servo actuator that drives a machine tool.
In particular, the present invention relates to the nonlinear ySl compensation method.

(Prior art) In this type of machining method, whether the machining device is a sliding mechanism or a rotary mechanism, the output torque of the actuator is In addition to the load torque, it is necessary to overcome the static Wtla force and also to overcome the Coulomb friction force, and the situation at that time will be explained below.

Usually, the transfer function of the actuator (such as a motor), the current loop, and the speed loop are considered, and each f
When the constants of the ilJ controller are adjusted appropriately, the position control system is represented by the block diagram shown in FIG.

The deviation between the manually input position command value X and the feedback of the actual actuator position x0 is the current value in the control system! 1. Torque command value T, but when starting from a stationary state, due to nonlinear disturbance due to static friction force and Coulomb friction force shown in dotted parentheses, the torque execution value T
, draws a non-linear curve as shown in FIG. 8 for the torque command value T, and when it starts to rotate in the opposite direction, it decreases once and then increases again. Point a on the curve corresponds to static friction force, T,
,, is the torque command value to overcome the static IF friction force,
Also, the dot corresponds to the Coulomb friction force, and Td2 is the torque command value to overcome the Coulomb friction PfA force.
are shown respectively. Furthermore, regarding y −jdl −
This is the same case as the x1 lottery mentioned above and the four pillars.

Figure 9 shows that X, YII+
! Arc locus 10 when performing arc cutting in a plane including h
In the coordinate diagram showing , it is assumed that the bite enters the fourth quadrant from the first quadrant at point C. Point F is also a quadrant cut point. FIGS. 10(a) and 10(b) are curves showing position command values X and y in the xI and Y wheel directions, respectively, corresponding to machining of the circular arc locus 10. When the movement of the actuator of each axis changes from the positive direction to the negative direction or from the negative direction to the positive direction with respect to the position command values X i and Y +, it is affected by the physical phenomenon described in L. Figure 11(a).

(b) shows the disturbances in the actuator operating speeds VX, V, in the vicinity of points C, D, and F, where the arc locus 10 intersects the X and Y axes, respectively, and is shown within the dotted line. It appears as a protrusion on an arc cut in response to the abnormal response of the actuator. Figure 12 shows 1 point C.
This figure shows the protrusion 11 on the machining line that occurs near the point, and similar protrusions also occur at points, F, and other quadrant switching points (not shown). These protrusions 11 are desired to be as small as possible since they cause errors in the correct circular shape. , the radial height is Δr, and currently Δ”=8~
10 μm, and it is desired to reduce it to Δr=2 to 3 μm.

In order to eliminate the protrusion 11 mentioned above, the position command value x+
, 3/i changes from the positive direction to the negative direction, instantaneously applies torque to overcome the static force and the Coulomb friction force, so that the actuator immediately rotates smoothly in the opposite direction from the stop n. There must be. On the contrary, position command value X+ *'! The same holds true when + changes from a negative direction to a positive direction.

Conventionally, this type of nonlinear friction compensation method has been proposed to reverse the connection direction of the integral capacitor when the speed control system of the servo device is configured using a proportional-integral controller.

A number of proposals have been made to change the label.

[Problem that the invention seeks to solve]

The conventional nonlinear friction compensation method described above is not effective unless 1) the required torque change at a speed zero signal is symmetrical between when it goes from positive direction to negative direction and when it goes in the opposite direction. 2) Static friction force and Coulomb The disadvantage is that if the frictional force and the kinetic frictional force at the beginning of movement are significantly different, the effect will be weak.

[Means for solving the problem] The nonlinear nB compensation method for the servo system of the present invention constantly monitors the quadrant switching point during contour machining by the machine tool.
When this time point is detected, a compensation function value is generated to compensate for a preset abnormal response at the time of quadrant switching, and the compensation function value is added to the input command value of the servo system.

[Effect]

In this way, the nonlinear thickness torque when starting from the static +h state, which is the cause of the abnormal response of the servo actuator, is investigated in advance, and the compensation function formula and parameters corresponding to the compensation function generation part in the control system are given. The quadrant switching point during machining is constantly monitored, and at that point, the compensation function generator generates a predetermined compensation function value, and this is added to the input command value of the servo system, which prevents abnormal responses of the servo actuator. can be suppressed, and the movement direction can be changed smoothly.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the nonlinear I! of the servo system of the present invention. FIGS. 2(a) and 2(b) are block diagrams showing the main parts of a numerical control device to which an embodiment of the I-friction compensation method is applied, and the configuration of a servo drive section controlled by the device, respectively. A diagram showing an example of the speed command value compensation function pattern used in the example, Figure 3 (
a) and (b) are respectively shown in Fig. 2 (a) and (b).
), Fig. 4 is a block diagram when the compensation function pattern is added to the input command value in the position control block diagram shown in Fig. 7, and Fig. 5 is a diagram showing the current value corresponding to the compensation/function pattern of (a) is a diagram showing the input speed command value curve without compensation, FIG. 5(b) is a diagram showing the compensation function pattern added to the input speed command value V, and FIG. A diagram showing a human speed command value curve when the compensation function pattern of FIG. 5(b) is added, and FIG. 6 is a flowchart showing the processing of the numerical control device according to the present embodiment.

The deviation counter 1 in Fig. 1 is a manually input position command value x1.
and a position encoder 8 that detects the position of the actuator 6.
The deviation from the output value from is calculated and the deviation value is output, and the position command value x1 or deviation value changes from positive to negative.
Or when it changes from negative to positive, that is, the quadrant switching point of the arc is detected and a switching detection signal is output. The compensation function generator 2 has a compensation function formula in advance, and when its parameters are set and a switching detection signal is input manually, it generates and outputs a compensation function value. The adder 3 adds the outputs of the deviation counter 1 and the compensation function generator 2, and the D/A converter 4 performs D/A conversion on the output of the adder 3. This analog command value is manually input to the servo amplifier section 5 to control the actuator 6.

Next, the operation of this embodiment will be explained with reference to the flowchart of FIG.

First, calculation of the parameters of the compensation function example having the patterns shown in FIGS. 2(a) and 2(b) will be explained. As already explained with respect to Figure 8,
In the figure, Tdl corresponds to the static +PI Ii force, and T11□ corresponds to the Coulomb friction force, and these values can be measured in the form of converted current values. That is,
If you start applying torque to the end of the motor shaft and read the current value of 1 dl at the moment the motor starts rotating, this is the torque command value T.
Corresponds to dl. Then very low speed (e.g. lrpm)
If you rotate the motor and measure the current value 1d2,
This corresponds to the torque command value Td□.

Therefore, first, the width ΔW of the protrusion 11 on the arc 10 in FIG.
Assuming that the time during which ΔT occurs is 8T, determine how much time ΔT should be shortened. The shorter the value, the better, but there is also a relationship with the mechanical part of the device, so A 5

+u is determined (n=2 to 5).

Next, FIGS. 2(a) and 2(b) show patterns of compensation function values VC used when there is almost no difference between the two values and when there is a considerable difference, respectively. In FIG. 11, in the abnormal response parts such as points C, D, and F, the speed loop is considered to be an oven loop, so the block diagram when adding the compensation function value vc to the speed command value Vl is shown in FIG. This can be shown as shown in Figure 4. Therefore, for the current value [8], the curves shown in Figures 3(a) and (b) correspond to the compensation function patterns in Figures 2(a) and (b), respectively, and both have a proportional term and Ji'! It is shown as a sum of terms.

From Figure 3(a).

From FIG. 3(b), since k is usually 1 (empirical value = o, 1 to 0, 2), the second term is omitted and the following is obtained.

By the above calculation, the parameters A + , B I, B
2 is determined and set in the compensation function generator 2 (step 21). The deviation counter 1 is the position command value Xi and the detected position X of the actuator 6 fed back from the position encoder 8. are compared, the deviation is calculated and output (step 22), and it is determined whether the sign of the deviation is reversed, that is, when the quadrant of the arc 101 is switched (
Step 23). When the quadrant switching time is detected, the detection A and - signals are sent from the deviation counter 1 to the compensation function generation section 2, which generates the compensation function value ■ゎ (step 24), and the addition section 3 converts the deviation value and compensation. Both function values VC are added manually, and the deviation value is output when the quadrant is not switched, and the total value with the deviation value is output when the quadrant is cut (step 25).

Next, the D/A converter 4 converts the human power from the adder 3 into D/A and sends it to the servo amplifier 5, and repeats the same operation (step 26).

In this way, comparing the manually input position command value x1 and the detected position XO fed back from the position encoder 8,
When the sign of that deviation reverses.

That is, at the time of quadrant switching, by adding a compensation function value ve according to a preset parameter during a certain W normal response period (δT) to the speed command value v1, the actuator 8 is adjusted to compensate for static friction (static friction), aerodynamics, and Coulomb f9 coefficient. It can overcome forces and smoothly reverse the direction of motion. FIG. 5 shows a curve when the compensation function value vc is added to the speed command value V.

In the drawings and explanations mentioned above, inputs and operations in the X-axis direction are described, but the same applies to the X-axis direction.

[Effects of the Invention] As explained below, the present invention provides a compensation function that compensates j+D for the nonlinear J and frictional force that is the cause of the Omiya response of the actuator that occurs when switching quadrants during contour addition 1. Parameters are calculated and set in the control system, while the quadrant switching point is constantly monitored and when the arrival of the quadrant switching point is detected,
By generating a surface compensation function value and adding it to the human power value of the servo system during the period of abnormal response, it is possible to reduce the To minimize abnormalities (protrusions),
It can be easily realized using software, and the compensation value can be changed freely in terms of parameters and time width, so it can be handled only on the servo system side, regardless of the type of machine tool, servo amplifier section, actuator, etc. There is an effect that it can be done.

[Brief explanation of the drawing]

FIG. 1 shows the main parts of a numerical control device that uses a nonlinear friction compensation method for a servo system of the present invention and the configuration of a servo drive section controlled by the device, and FIG. (a) and ('b) are diagrams showing examples of speed command value compensation function patterns used in this embodiment, respectively, and Fig. 3 (
a) and (b) are respectively Fig. 2(a). (b) A diagram showing current values corresponding to the compensation function pattern,
Figure 4 is a block diagram of the position control system of a normal servo system (
Fig. 7) is a block diagram when the compensation function pattern is added to the input command value, Fig. 5 (a) is a graph showing the human speed command value curve without compensation, and Fig. 5 (b) is the servo A diagram showing the compensation function pattern added to the input speed command value Vi to the amplifier section, FIG. 5(C) is similar to FIG. 5(b)
6 is a flowchart showing the processing of the numerical processing device according to this embodiment, and FIG. 7 is a block diagram of the speed control system of a normal servo system. Figure 8 is a coordinate diagram showing the torque command value T near the quadrant switching point and the arc locus when performing circular cutting, and Figures 10 (a) and (b) are respectively for the machining shown in Figure 9. Graphs 11(a) and 11(b) showing the X-axis and Y-axis position command values withstand, respectively, show the operating speed V of the actuator that occurs when switching quadrants for the circular arc machining shown in FIG. 9. , V, and FIG. 12 is a diagram showing the state of protrusions on the machining line caused by the disturbance in the operating speed of the actuator in FIG. 11. ■...deviation counter, 2...compensation function generator,
3.J addition section, 4.D/A conversion section,
5... Servo amplifier section, 6... Actuator, 7
・-TG, 8--Position encoder, 10--Circular arc, 11--Protrusion, 21-
26...Step, A,,B,,B2...Parameter, δT...Period, k...Coefficient (percent), X+, yr" position command value, ■,...Speed command Value, vc...compensation function value, K1
... proportionality constant, T ... integral constant, K ... torque constant, 1. ...Current value, T1...Torque command value, Ta...Torque effective value, J...Moment of inertia. T1.1...Torque command value corresponding to Shizuichi Atsushi, '''
12...Torque command value corresponding to Coulomb friction, C,
D, F... Quadrant switching point, VX, V,... Actuator speed, Δr... Height of protrusion 11, ΔW... Width of protrusion 11.

Claims (1)

[Claims] In a nonlinear friction compensation method for a servo system that controls contour machining of a machine tool, the quadrant switching point is constantly monitored during contour machining, and when the quadrant switching point is detected, a preset quadrant is switched. A nonlinear friction compensation method for a servo system, characterized in that a compensation function value that compensates for an abnormal response during switching is generated, and the compensation function value is added to an input command value of the servo system.