KR20080079590A - Method and apparatus for compensating a stick motion generated at a quadrant changing position in nc machine tools - Google Patents

Abstract

A friction compensation method, a friction compensator, and a motor controller are provided to shorten a time required for adjusting parameters by estimating friction and frictional torque with high precision. A friction compensation method comprises the steps of generating a present position signal by estimating a present position of a movable member using a present position estimation unit(21), obtaining a speed signal by differentiating the present position signal using a differentiator(22), generating a displacement signal by integrating the speed signal using an integrator(24), and obtaining an absolute value of the displacement signal using an absolute value calculator(25). A friction characteristic estimation unit(26) calculates variation for the displacement of the friction or frictional torque. A multiplier(27) calculates variation relative to time by multiplying the variation by the speed signal.

Description

Friction Compensation Method, Friction Compensator and Motor Control Device TECHNICAL TOOLS TECHNICAL AND APPARATUS FOR COMPENSATING A STICK MOTION GENERATED AT A QUADRANT CHANGING POSITION IN NC MACHINE TOOLS

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a motor for driving a feed shaft, such as a table of a machine tool, and more particularly, to compensate for a frictional force or friction torque when reversing the drive direction of a feed shaft when machining a workpiece attached to the table. A friction compensation method, a friction compensator and a motor control device.

In the control of a motor that makes a 2-axis circular interpolation motion in a machine tool, first, a speed command signal of the motor is generated so that the position detection signal and the position command signal of the moving object fed by the motor coincide. Next, a method of generating a torque command signal so that the speed detection signal and the speed command signal of the motor coincide, and controlling the torque of the motor based on this torque command signal is generally adopted.

In the control of such a motor, when reversing the rotational direction of the motor, the machine cannot normally reverse immediately. If the upper limit changes during circular arc cutting due to the friction of the feed drive mechanism, this causes the trajectory of the actual motion to move outward from the command trajectory, causing the trajectory to expand. This phenomenon is called an upper limit projection and is one cause of the deterioration of the contour machining accuracy.

Such a phenomenon occurs that when the direction of movement is reversed, it is necessary to reverse the torque command by the frictional force or the friction torque, but the feed shaft stops temporarily because there is a delay due to the responsiveness of the speed loop generating the torque command signal. It is considered because. Here, since the friction force and the friction torque can be uniquely converted by multiplying the coefficient determined by the structure of the feed drive mechanism, the following description will use the friction force and the friction torque in the same sense.

In order to reduce the upper limit projection described above, Patent Document 1 described below expresses the relationship between the speed and the frictional force by a formula, determines the parameter in advance, and always monitors the position information measured by the encoder so that the direction of motion When the point of inversion is detected and the inversion of this movement direction is detected, the method by which the influence by a frictional force is erased and eliminated by adding the compensation value according to a parameter preset in the period of an abnormal response to a speed command is started. It is.

In addition, Patent Document 2 described below sets a target value of the integrator of the speed control system immediately before inverting the direction of movement to the speed command output from the position controller until the movement amount a reaches from a point where the direction of movement is reversed. A method of applying a compensation value determined by the acceleration at the time of inversion from the movement amount (b) (> a) to the movement amount (c) (> b) is disclosed.

In addition, Patent Document 3 described below determines the rotational direction of the motor from the speed command, which is the output from the position controller, and provides a dead band for speed or acceleration, and outputs a compensation value, and outputs the compensation value from the speed controller. A method of compensating the influence of the frictional force at the time of reversing the movement direction by adding to the in torque command is disclosed.

In addition, the following non-patent document 1 describes the torque at the time of reversing the movement direction by reversing the sign of the integral element of the speed control system and reversing the armature current of the motor when the direction of rotation of the ball screw is reversed. Disclosed is a method for correcting the influence of a sudden change in the.

In addition, in the non-patent document 2 described below, a method of applying a certain correction value to the current command until the load starts to move at the start of the movement or the direction of the movement is reversed, and zeroing the correction value when detecting that the movement has started. Is disclosed.

In addition, in the non-patent document 3 described below, a method of analytically calculating the size of the upper limit protrusion caused by the influence of friction during circular motion is developed, and the position command of the servo system is corrected based on the calculated amount of protrusion. The method of correcting is disclosed.

Patent Document 1: Japanese Patent Application Laid-Open No. 63-250715

Patent Document 2: Japanese Patent Application Laid-Open No. 7-13631

Patent Document 3: Japanese Patent Application Laid-Open No. 11-143548

[Non-Patent Document 1] Kakino Yoshiaki, Ibara Jimin, Nakatsu Zhenbu, Shinohara Jangong: A Study on the Motion Accuracy of NC Machine Tool (6th Report), Generation Mechanism of Stick Motion during Circular Interpolation Transfer, Correction and Precision Work Journal, V01.56, N0.4 (1990) pp. 139 to 144

[Non-Patent Document 2] Casting Noriyuki, Chungwoo Kye-seong, Genji Tsumura, Katsuyoshi Takeuchi, Michiko Ekawa: A Study on the High Precision of Machine Tool Feeding by Bang Bang Control, Journal of the Korean Society of Precision Engineering, V0.60, N0.3 (1994) ) pp.427 to 431

[Non-Patent Document 3] Elder Nagashima, Nori Katsuki, Kuni Kawakari: Theoretical Analysis of Upper Limit Turnover Amount of NC Machine Tool and Correction by Input Adaptive System, Japanese Society of Mechanical Engineers (C), V0.66, N0 .648 (2000) pp. 407 to 413

However, in the above-described methods disclosed in Patent Documents 1, 2, 3 and Non-Patent Document 2, it is necessary to adjust each parameter in accordance with the speed and acceleration of the movement and store it in a memory, and the adjustment of these parameters is an experience. Since it is performed by oversense, there is a problem that a large amount of time is required for adjustment in order to effectively operate the correction.

In addition, in the methods disclosed in Patent Documents 2 and 2 described above, the output of the integrator of the speed control system immediately before reversing the direction of motion is compensated as a frictional force. Since the inertia force is also maximized by this, there exists a problem that the method disclosed by these documents cannot be applied at the time of high motion.

In addition, in the method disclosed in the above-described non-patent document 3, since the motion error is analyzed by ignoring the dynamic characteristics of the servo system, when the speed and acceleration are large and the dynamic characteristics cannot be ignored, There is a problem that the exact amount of protrusion cannot be calculated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to accurately estimate the frictional force or friction torque without affecting the speed and acceleration before and after reversing the direction of movement, It is to provide a friction compensation method and a friction compensator that can significantly reduce the time required for adjustment.

Another object of the present invention is to provide a motor control device capable of significantly improving the motion accuracy when a two-axis circular interpolation motion is performed in a machine tool.

In order to achieve the above object, the present invention is to generate a speed command signal of the motor so that the position detection signal and the position command signal of the moving object is moved by the motor, and the speed detection signal and the speed command of the motor Generates a torque command signal to match the signal, and generates a friction compensation signal that compensates for the frictional force or friction torque generated when inverting the rotation direction of the motor in controlling the torque of the motor based on the torque command signal. In the friction compensation method of using the torque command signal as a correction value,

A step of generating a real position signal by estimating a real position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved;

The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Generating a displacement signal from the position and finding its absolute value;

Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Calculating a rate of change of the frictional force or friction torque over time by multiplying the rate signal with respect to the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time;

Model the characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiply the inverse function of the transfer function of the model by the estimated friction force or friction torque to And a step of generating a friction compensation signal.

In addition, the present invention generates a speed command signal of the motor so that the position detection signal and the position command signal of the moving object conveyed by the motor coincide, and the torque command so that the speed detection signal of the motor and the speed command signal coincide. In generating a signal and controlling the torque of the motor based on the torque command signal, a friction compensation signal for compensating for the frictional force or the frictional torque generated when the rotation direction of the motor is reversed is generated to generate the signal. In the friction compensator to be a correction value,

Means for estimating the actual position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved;

The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Means for generating a displacement signal from the position and finding its absolute value,

Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Means for calculating the rate of change of the frictional force or friction torque over time by multiplying the rate signal with respect to the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time;

Means for modeling a characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiplying the inverse function of the transfer function of the model by the estimated friction force or friction torque to generate the friction compensation signal; Characterized in that provided.

In addition, the present invention is a position controller for generating a speed command signal of the motor so that the position detection signal and the position command signal of the moving object to be moved by the motor, and the speed detection signal and the speed command signal of the motor match A speed controller for generating a torque command signal, a friction compensator for generating a friction compensation signal for compensating for the frictional force generated when reversing the rotation direction of the motor, and a value obtained by adding the torque command signal and the friction compensation signal. In the motor control device having a torque controller for controlling the torque of the motor based on,

The friction compensator,

Means for estimating the actual position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved;

The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Means for generating a displacement signal from the position and finding its absolute value,

Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Means for calculating the rate of change of the frictional force or friction torque over time by multiplying the rate signal with respect to the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time;

Means for modeling a characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiplying the inverse function of the transfer function of the model by the estimated friction force or friction torque to generate the friction compensation signal; It is characterized by including.

According to the friction compensation method and friction compensator according to the present invention, a velocity signal is obtained by differentiating a real position signal of a moving object, and by integrating this speed signal, a displacement signal is generated from a position at which the moving object reverses the direction of motion and its absolute value. To obtain the rate of change of the frictional force or friction torque using a model representing the relationship between displacement and frictional force or friction torque, and multiply the rate signal by the rate of change for this displacement to obtain the rate of change over time. Since the frictional force or the frictional torque are estimated by integrating the change rate, the frictional force or the frictional torque can be estimated with high accuracy without being influenced by the speed and acceleration before and after the direction of movement is reversed.

Moreover, according to the friction compensation method and friction compensator which concerns on this invention, the model which estimates the actual position of a moving body, the model which shows the relationship of a displacement and friction force or friction torque, and each parameter of a model from a torque command signal to the torque of a motor Since many are known and there are few parameters that require substantially adjustment, the time required for adjustment of parameters can be significantly shortened compared with the conventional one.

Moreover, according to the motor control apparatus which concerns on this invention, since the friction compensator which can estimate a friction force or a friction torque with high precision is made into a component as mentioned above, when making a 2-axis circular interpolation motion by a machine tool, The movement precision can be improved significantly.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on suitable embodiment shown in drawing. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows schematic structure of one Embodiment of the friction compensator which concerns on this invention, and the motor control apparatus containing this. In Fig. 1, the table 2 as a moving body which is conveyed by the motor 1 is supported by a linear motion guide mechanism (not shown) so as to be movable, and the rotational motion of the motor 1 is a ball screw ( Through the power transmission mechanism including 3) and the nut 4, it is converted into the linear motion of the table 2. Thus, by controlling the motor 1, the position, speed and acceleration of the table 2 can be controlled.

In order to control the motor 1, the table 2 is equipped with a linear encoder (not shown) for detecting its position, and the motor 1 is attached with a taco generator or a rotary encoder (not shown) for detecting its speed. It is. The position controller 11 generates the speed command signal of the motor 1 so that the position command signal applied from the host controller and the position detection signal of the table 2 detected by the linear encoder coincide with each other. ) The speed controller 12 generates a torque command signal so that the speed command signal applied from the position controller 11 and the speed detection signal of the motor 1 detected by the taco generator or rotary encoder coincide with the adder 14. Add. The friction compensator 13 generates and applies a friction compensation signal to the adder 14 on the basis of the position command signal applied from the host controller to compensate for the frictional force generated when the rotation direction of the motor 1 is reversed. The adder 14 adds the torque command signal applied from the speed controller 12 and the friction compensation signal applied from the friction compensator 13 to apply the frictionally compensated torque command signal to the servo amplifier 15 as the torque controller. . The servo amplifier 15 controls the armature current of the motor 1 to generate torque as faithful as possible to the friction compensated torque command signal.

Of the components constituting the motor control device shown in FIG. 1, the configuration and operation of the position controller 11, the speed controller 12, and the servo amplifier 15 are generally well known, and thus their description is omitted. The configuration and operation of the friction compensator 13 directly related to the present invention will be described in detail after the principle thereof is explained.

The friction force in the drive mechanism of the table 2 shown in FIG. 1 changes rapidly when the direction of movement of the table 2 is reversed, that is, when the direction of rotation of the ball screw 3 is reversed. The response of the control system does not correspond to this change, and for example, an upper limit projection occurs when performing circular arc cutting by performing circular interpolation motion using two orthogonal axes. The friction compensator 13 is for correcting the influence of the frictional force at the time of reversing the movement direction of the table 2.

Therefore, in the feed drive system using the ball screw and the linear rolling guide, the sine wave reciprocating motion of the table with an amplitude of 50 μm (micrometer) and a period of 4 s (second) is considered that the friction force is not affected by the speed and acceleration. When the temporal change of the motor torque in that case was measured, it was found that the motor torque is almost equal to the nonlinear friction torque in terms of the motor shaft. FIG. 2 (a) is a diagram showing the temporal change of the friction torque corresponding to the motor torque, and based on this measurement result, when the horizontal axis is plotted with the table displacement and the vertical axis is the friction torque, it is shown in FIG. As shown, a diagram showing the relationship between the displacement and the friction torque was obtained. As is apparent from FIG. 2B, the displacement and the friction torque are almost proportional in the displacement of 10 μm or less, and the friction torque in the displacement of 10 μm to 40 μm is substantially constant. . In addition, the return motion exhibits the same characteristics, and the friction torque draws a hysteresis loop according to the reciprocation motion.

In the actual motion influenced by the speed and the acceleration, the control system cannot cope with a change in the friction torque as shown in Figs. 2A and 2B, and a motion error occurs. Conversely, if the motor torque is completely followed by the change in the friction torque, the servo system can be realized in which a motion error due to friction does not occur.

This embodiment models the frictional characteristics as shown in Figs. 2A and 2B as a function of displacement from the reversal position in the movement direction by the following equation (1).

f = f _c (2tanh (ax ')-1) sgn (dx' / dt)... (One)

only,

f: friction torque [Nm]

x ': displacement from the position where the moving body reverses the direction of motion

a: inclination of frictional force or friction torque with respect to the displacement of the movable body in the small displacement region of the movable body

f _c : Friction torque when displacement of moving object is big enough [Nm]

sgn: Sign function (+1 when dx '/ dt> 0, 0 when dx' / dt = 0, -1 when dx '/ dt <0)

to be. And the change of the friction torque at the time of reciprocation obtained by calculating the friction torque f at the time of sine wave reciprocation using Formula (1) is shown in FIG. (B) is shown, respectively. As is apparent from Figs. 3A and 3B, the above equation (1) shows that the actual change in friction torque can be estimated.

In this way, according to Equation (1), if the change in the friction torque at the time of inversion of the movement direction is estimated in advance, and the correction value for correcting the torque command signal of the servo system is considered, the influence of friction can be compensated. do. However, by the delay elements existing inside each of the servo amplifier 15 and the motor 1, the friction-compensated torque command signal obtained by correcting the torque command signal in the above formula (1) is supplied to the servo amplifier 15. Even if it is applied, the torque actually output from the motor 1 will be different. Generally, the delay elements of the servo amplifier 15 and the motor 1 are modeled by the torque command filter 16 and the current loop 17, as shown by the block diagram of FIG. In Fig. 4, T _r is a torque command signal applied to the servo amplifier 15, T _m is a motor torque [Nm] actually generated, T _f is a time constant [s] of the torque command filter, and T _i is a current loop. 'S time constant [s], s is the Laplace operator.

In addition, when the friction torque is calculated by the above equation (1) from the actually measured position signal, an error due to the influence of noise or quantization included in the measurement result occurs. If the friction torque is calculated from the position command signal applied from the host controller, the actual position is delayed from the position command signal, and therefore the timing for correcting the torque command signal is not correct. In addition, since the sign function sgn is included in the above formula (1), there is a problem that chattering occurs when applied to an actual machine.

Fig. 5 is a block diagram showing the detailed configuration of the friction compensator 13 which solves the above problems, together with the associated signal waveform. In FIG. 5, the real position estimating unit 21 inputs a position command signal applied from the host controller, and uses the model of the servo control system to which the table 2 is moved. It is to estimate the actual position of to generate a real position signal. The real position estimator 21 is connected with a differentiator 22 which differentiates the real position signal and outputs it as a speed signal. The differentiator 22 detects that the sign of the speed signal is inverted and outputs a reset signal. The integrating detector 23 and the speed signal are integrated to restore the real position signal, and each time the reset signal is output from the sign inversion detecting unit 23, the integral value is reset to zero so that the table 2 adjusts the movement direction. An integrator 24 that has generated a displacement signal from the inverted position is connected, and an integrator 24 is connected to an absolute value calculator 25 for obtaining an absolute value of its output.

In the absolute value calculation section 25, a model representing the relationship between the displacement from the position at which the table 2 reverses the direction of movement and the friction torque is used to determine the displacement (position) of the friction torque as a function of the displacement signal expressed in absolute value. A frictional characteristic estimating section 26 for determining the rate of change for the circuit is connected. The multiplier 27 which multiplies the change rate with respect to the displacement output from the friction characteristic estimation part 26 and the speed signal output from the differentiator 22 and computes the change rate with respect to the time of a friction torque is provided. At the output end of the multiplier 27, an integrator 28 for estimating the friction torque is provided by integrating the rate of change of the friction torque over time. The integrator 28 also models the characteristics from the torque command signal input to the servo amplifier 15 to the torque of the motor 1 actually output, and multiplies the inverse function of the transfer function of the model by the estimated friction torque. The response delay compensator 29 for generating the friction compensation signal is connected.

6 is a block diagram showing the detailed configuration of the response delay compensator 29. The coefficient block 31, the derivative block 32, the adder 33, the differential block 34, and the adder 35 are shown in FIG. It consists of). In Fig. 6, f _e (t) is the estimated friction torque [Nm], T _f is the time constant [s] of the torque command filter described above, T _i is the time constant [s], s of the current loop described above. The Laplace operator described above. In addition, T _rg is a conversion constant from the torque command signal to the torque.

The operation of the friction compensator 13 configured as described above will be described below. First, when the position command signal r is applied from an upper controller not shown, the actual position estimating unit 21 estimates the actual position of the table 2 according to the following equation (2) and then the actual position signal xe (t Create)).

x _e (t) = {1 / (T _c s + 1)} r... (2)

only,

T _c : delay time constant of the whole servo system

s: Laplace operator

to be.

The real position signal x _e (t) generated by the real position estimator 21 is differentiated from the differentiator 22 and output as a speed signal dx / dt, and the sign inversion detector 23 and the integrator 24 are used. And multiplier 27. The sign inversion detector 23 detects that the sign of the speed signal dx / dt is inverted and outputs a reset signal. The integrator 24 outputs the position signal again by integrating the speed signal dx / dt, and since it is reset every time a reset signal is applied from the sign inversion detecting section 23, the displacement from the position inverting the direction of movement Output as a signal (± x '). The absolute value calculator 25 calculates the absolute value of the displacement signal ± x 'and outputs the displacement signal x'. The friction characteristic estimator 26 calculates the rate of change of the friction torque with respect to the displacement as a function of the displacement signal x ', that is, the friction characteristic in the following equation (3). Equation (3) is obtained by differentiating the above equation (1) by one system by the displacement signal xe.

df _e / dx _e = 2af _c {1-tanh ² (ax ')}. (3)

Multiplying the rate of change (df _e / dx _e ) of the friction torque with respect to the displacement obtained in equation (3) by the speed signal (dx _e / dt) output from the differentiator 22 results in the differential value of the estimated value of friction torque. Therefore, the multiplier 27 performs calculation of the following formula (4).

df _e / dt = (df _e / dx _e ) · (dx _e / dt). (4)

Next, the integrator 28 calculates the estimated value f _e (t) of the friction torque by integrating the derivative value df _e / dt of the estimated value of the friction torque. The response delay compensator 29 performs a response delay compensation on the estimated value f _e (t) of the friction torque to generate a friction compensation signal. When the delay elements of the servo amplifier 15 and the motor 1 are modeled as shown in FIG. 4, the response delay compensation unit 29 is configured as shown in the block diagram of FIG. That is, the friction compensation signal is generated by multiplying the inverse function of the transfer function representing the characteristic from the torque command signal to the torque of the motor actually output by the estimated friction torque f _e (t). In Fig. 6, T _f is a time constant [s] of the torque command filter, T _i is a time constant [s] and s of the current loop, and a Laplace operator, and T _rg is a conversion constant from the torque command signal to the friction torque.

Next, in order to confirm the effect of the motor position control apparatus mentioned above, the case where circular interpolation motion is performed without applying this invention and the case where circular interpolation motion is performed by applying this invention is compared. Fig. 7 is a perspective view showing a schematic configuration of a motor control device for performing circular interpolation motion, wherein the servo motor 42 for driving the XY table 41 in the X and Y directions is an X axis servo amplifier 43, respectively. And a personal computer (hereinafter abbreviated as PC) 50 via a Y-axis servo amplifier 44. In addition, two linear encoders 45 are provided to detect the position in the X direction and the position in the Y direction of the XY table 41, respectively. The PC 50 has a digital signal processor (DSP) function, and has functions of the position controller 11, the speed controller 12, and the friction compensator 13 shown in FIG.

Initially, a conventional motor control device (e.g., partial model matching method (Kitamori Shunko: design method of the control system based on the partial knowledge of the control object, Journal of the Korean Society for Measurement and Automatic Control, Vol. 15, No. 4, (1979) ), pp549 to 555) (Ideyu, Sato Ryuta, Masao, Part .: Design of Control System of Feed Drive System by Partial Model Matching Method, 2005 Lecture on Precision Engineering Spring Conference, (2005), pp1133 to 1134) Fig. 8 shows the result of checking the error in the case of performing the circular interpolation motion by adjusting each servo gain). Fig. 8 shows the error between the ideal arc trajectory and the actual trajectory enlarged by 1000 times. Among these, FIG. 8 (a) is an arc trajectory when the feed speed is 3 m / min and the radius is 25 mm, and FIG. 8 (b) is when the feed speed is 6 m / min and the radius is 25 mm. 8C is a circular arc trajectory in the case where the feed speed is 3 m / min and the radius is 10 mm. In all of the results shown in (a), (b) and (c) of FIG. 8, a locus error, i.e., an upper limit protrusion, occurs in the vicinity of 0 °, 90 °, 180 °, and 270 °. Among them, the movement direction of the X axis is reversed at 0 ° and 180 °, and the movement direction of the Y axis is reversed at 90 ° and 270 °. The locus error of the projection shape in the vicinity of each inversion position is that the response of the servo system to the change in the frictional force at the time of inversion of the movement is shown on the arc locus.

Next, the result of having investigated the error at the time of performing circular interpolation motion by applying the friction compensator which concerns on this invention is shown in FIG. 9A, 9B, and 9C are results of circular interpolation motions at the same speed and radius as those shown in Figs. 8A, 8B, and 8C, respectively. In all of the results shown in (a), (b) and (c) of Fig. 9, the locus error of the projection shape in the vicinity of 0 °, 90 °, 180 °, and 270 ° is eliminated, and the movement precision is greatly reduced. It can be seen that the improvement.

Further, in the friction compensator according to the present invention, the delay time constant Tc of the servo system, the friction torque f _c of motor shaft conversion, the rising coefficient a of friction torque, and the time constant T _f of the torque command filter Once the six parameters of the current loop time constant (T _i ) and the torque command to torque conversion constant (T _rg ) are set once, it is necessary to readjust the parameters even if the radius of the circular motion or the feed rate change. There is no. In addition, the parameter associated with the friction, that is, have a tendency parameter other than the friction torque (f _c) and the rising coefficient of the frictional torque (a) in terms of the motor shaft is already known, the parameters required are substantially adjusted to the f _c and only two of a. Therefore, compared with the conventional friction compensator, the time required for parameter adjustment can be significantly shortened.

According to the friction compensator according to the present invention, a rate of change for a displacement of friction force or friction torque is obtained, a rate signal is multiplied by the rate signal for the displacement, and the rate of change for time is integrated, and the rate of change for this time is integrated to give a frictional force or friction Since the torque is estimated, the friction force or the friction torque can be estimated with high accuracy without being influenced by the speed and acceleration before and after reversing the direction of movement. It is possible to improve the movement precision of numerically controlled machine tools, three-dimensional measuring machines, semiconductor manufacturing apparatuses, and robots.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows schematic structure of one Embodiment of the friction compensator which concerns on this invention, and the motor control apparatus containing this.

Fig. 2 is a diagram showing the temporal change of friction torque and the relationship between displacement and torque when the table is sinusoidally reciprocated by a feed drive system.

Fig. 3 is a diagram showing the temporal change of the friction torque obtained by calculation using an approximation equation showing the relationship between the displacement and the friction torque from the position at which the table reverses the direction of movement, and the relationship between the displacement and the torque.

4 is a block diagram showing delay elements of the servo amplifier and the motor;

Fig. 5 is a block diagram showing a detailed configuration of an embodiment of a friction compensator according to the present invention together with an associated signal waveform.

Fig. 6 is a block diagram showing a detailed configuration of a response delay compensator which constitutes one embodiment of a friction compensator according to the present invention.

7 is a perspective view showing a schematic configuration of a motor control device for performing circular interpolation motion.

Fig. 8 is a diagram showing an error between an ideal arc trajectory and an actual trajectory in the case of performing circular interpolation motion using a conventional friction compensator.

Fig. 9 is a diagram showing an error between an ideal arc trajectory and an actual trajectory when the circular interpolation motion is performed using the friction compensator according to the present invention.

(Explanation of symbols for the main parts of the drawing)

1: motor 2: table

3: ball screw 4: nut

11: position controller 12: speed controller

13: friction compensator 14: adder

15: Servo amplifier 16: Torque command filter

17 current loop 21 real position estimation unit

22: differentiator 23: sign inversion detector

24, 28: integrator 25: absolute value calculation unit

26: friction characteristic estimation unit 27: multiplier

29: response delay compensation unit

Claims (5)

Generating a speed command signal of the motor so that the position detection signal and the position command signal of the moving object conveyed by the motor coincide; generating a torque command signal such that the speed detection signal of the motor and the speed command signal coincide; In controlling the torque of the motor based on the torque command signal, a friction compensation method of generating a friction compensation signal for compensating for the frictional force or friction torque generated when the rotation direction of the motor is inverted to be a correction value of the torque command signal. To Generating a real position signal by estimating a real position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved; The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Generating a displacement signal from the position and finding its absolute value; Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Calculating a rate of change of the frictional force or friction torque over time by multiplying the rate signal by the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time; Modeling a characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiplying the inverse function of the transfer function of the model by the estimated friction force or friction torque to generate the friction compensation signal. Friction compensation method characterized in that provided. The method of claim 1, The model which shows the relationship between the displacement from the position which the said moving body reverses a direction of movement, and a friction force or friction torque, Based on the relationship between the displacement of the movable body and the motor torque when the movable body is sine wave reciprocated at an amplitude and a period not affected by the speed and acceleration, the frictional force or the friction torque is an approximation formula that is expressed as a function of the displacement of the movable body. Friction compensation method. The method of claim 2, Friction force or the friction torque f, X ', the displacement from the position in which the movable body reverses the direction of motion A slope of friction force or friction torque with respect to the displacement of the movable body in the microdisplacement region of the movable body a, The frictional force or frictional torque when the displacement of the movable body is large enough, f _c , Let's set the sign function to sgn The approximation formula is f = f _c (2tanh (ax ')-1) sgn (dx' / dt) And the rate of change df _e / dx _e for the displacement of friction force or friction torque is df _e / dx _e = 2af _c {1-tanh ² (ax ')} The friction compensation method characterized by the above-mentioned. Generating a speed command signal of the motor so that the position detection signal and the position command signal of the moving object conveyed by the motor coincide; generating a torque command signal such that the speed detection signal of the motor and the speed command signal coincide; In controlling the torque of the motor based on the torque command signal, the friction compensator generates a friction compensation signal for compensating for the frictional force or friction torque generated when the rotation direction of the motor is inverted to be a correction value of the torque command signal. In Means for estimating the actual position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved; The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Means for generating a displacement signal from the position and finding its absolute value, Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Means for calculating the rate of change of the frictional force or friction torque over time by multiplying the rate signal with respect to the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time; Means for modeling a characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiplying the inverse function of the transfer function of the model by the estimated friction force or friction torque to generate the friction compensation signal; Friction compensator, characterized in that provided. A position controller for generating a speed command signal of the motor so that the position detection signal and the position command signal of the moving object fed by the motor coincide; and generating a torque command signal for the speed detection signal of the motor to match the speed command signal A torque controller, a friction compensator for generating a friction compensation signal that compensates for the frictional force generated when the rotation direction of the motor is reversed, and a torque of the motor based on the sum of the torque command signal and the friction compensation signal. In the motor control device having a torque controller for controlling the, The friction compensator, Means for estimating the actual position of the movable body corresponding to the position command signal by using a model of a control system in which the movable body is moved; The real position signal is differentiated to be a speed signal, the speed signal is integrated to restore the real position signal, and when the sign of the speed signal is inverted, the integral value is reset to zero so that the moving body reverses the direction of movement. Means for generating a displacement signal from the position and finding its absolute value, Using a model representing the relationship between the displacement from the position at which the movable body reverses the direction of movement and the frictional or frictional torque, the rate of change for the displacement of the frictional or frictional torque as a function of the displacement signal expressed in absolute values is obtained, and Means for calculating the rate of change of the frictional force or friction torque over time by multiplying the rate signal with respect to the rate of change, and estimating the frictional force or friction torque by integrating the rate of change over time; Means for modeling a characteristic from the torque command signal input to the torque controller to the torque of the motor actually output, and multiplying the inverse function of the transfer function of the model by the estimated friction force or friction torque to generate the friction compensation signal; The motor control device characterized in that it comprises.

Images