JP4581096B2 - Friction compensation method, friction compensator, and motor control device - Google Patents

Description

  The present invention relates to control of a motor that drives a feed shaft such as a table of a machine tool, and in particular, when machining a workpiece attached to a table, a frictional force when reversing the drive direction of the feed shaft or The present invention relates to a friction compensation method for compensating friction torque, a friction compensator, and a motor control device.

  In the control of a motor that performs a two-axis circular interpolation motion on a machine tool, first, a motor speed command signal is generated so that the position detection signal and the position command signal of a moving body fed by the motor coincide with each other. In general, a method is used in which a torque command signal is generated so that the motor speed detection signal and the speed command signal coincide with each other, and the motor torque is controlled based on the torque command signal.

  In such motor control, when the motor rotation direction is reversed, usually the machine cannot be reversed immediately. This is due to the influence of the friction of the feed drive mechanism, and if the quadrant changes during arc cutting, the actual motion trajectory goes out of the command trajectory, causing the trajectory to bulge. This phenomenon is called quadrant protrusion and contributes to a decrease in contour processing accuracy.

  This phenomenon occurs because when the direction of motion is reversed, it is necessary to reverse the torque command by the amount of friction force or friction torque, but there is a delay due to the responsiveness of the speed loop that generates the torque command signal. This is thought to be because the axis is temporarily stopped. Here, since the friction force and the friction torque can be uniquely converted by multiplying by a coefficient determined by the configuration of the feed drive mechanism, the friction force and the friction torque are used in the same meaning in the following description.

  In order to reduce the above-mentioned quadrant protrusion, the following Patent Document 1 expresses the relationship between speed and frictional force by a mathematical formula, determines its parameters in advance, and constantly monitors the position information measured by the encoder. When the direction of movement is reversed, and when the movement direction is reversed, a compensation value according to a preset parameter is added to the speed command during the period of abnormal response. A method for eliminating the effect is disclosed.

  Further, in Patent Document 2 below, the output of the integrator of the speed control system immediately before reversing the motion direction to the speed command output from the position controller until a certain amount of movement a is reached from the point where the motion direction is reversed. A method is disclosed in which a compensation value with a target value is applied from a movement amount b (> a) to a movement amount c (> b) determined by the acceleration at the time of reversal.

  Further, in Patent Document 3 below, the rotational direction of the motor is determined from the speed command that is output from the position controller, and a compensation value is output with a dead zone for speed or acceleration. A method of compensating for the influence of frictional force when reversing the motion direction by adding to a torque command that is an output from a controller is disclosed.

  Non-Patent Document 1 below discloses that the torque at the time of reversing the motion direction is obtained by reversing the sign of the integral element of the speed control system and reversing the armature current of the motor when the rotation direction of the ball screw is reversed. A method for correcting the influence due to a sudden change in the value is disclosed.

  Non-Patent Document 2 below describes a method of adding a certain correction value to the current command until the load starts moving at the start of movement or reversing the movement direction, and setting the correction value to zero when the movement is detected. It is disclosed.

Non-Patent Document 3 below has developed a method for analytically calculating the size of a quadrant protrusion caused by the influence of frictional force during circular motion, and gives a servo system position command based on the calculated protrusion amount. A method of correcting by correcting is disclosed.
JP-A-63-250715 JP-A-7-13631 JP 11-143548 A Yoshiaki Kakino, Yoshitoshi Ihara, Yoshio Nakatsu, Akiyoshi Shinohara: Study on motion accuracy of NC machine tools (6th report), Generation mechanism and correction of stick motion during circular interpolation feed, Journal of Japan Society for Precision Engineering, Vol.56, No.4 (1990) pp.139-144 Noriyuki Koreda, Keisei Okito, Kenji Tsumura, Katsuyoshi Takeuchi, Ikuo Egawa: Research on high precision machine tool feeding by bang-bang control, Journal of Japan Society for Precision Engineering, Vol.60, No.3 (1994) pp.427-431 Kazuo Nagashima, Masahide Katsuki, Kuniharu Kawakami: Theoretical analysis of the amount of quadrant switching on NC machine tools and correction by the input adaptive system, Transactions of the Japan Society of Mechanical Engineers (C), Vol.66, No.648 (2000) pp.407 ~ 413

  However, in the methods disclosed in Patent Documents 1, 2, 3 and Non-Patent Document 2 described above, it is necessary to adjust each parameter according to the speed and acceleration of movement and store it in a memory. Since the adjustment is performed based on experience and intuition, in order to make the correction work effectively, there is a problem that it takes a lot of time for the adjustment.

  In the methods disclosed in Patent Document 2 and Non-Patent Document 2 described above, the output of the integrator of the speed control system immediately before reversing the motion direction is compensated as a frictional force, but the motion direction is reversed. Immediately before, the acceleration is maximized, and the inertial force is also maximized. Therefore, there is a problem that the methods disclosed in these documents cannot be applied during high acceleration motion.

  In the method disclosed in Non-Patent Document 3 described above, since the motion error is analyzed on the assumption that the dynamic characteristics of the servo system can be ignored, when the speed and acceleration are large and the dynamic characteristics cannot be ignored, There was a problem that it was impossible to calculate an accurate projection amount.

The present invention has been made to solve the above problems, and its purpose is to estimate the frictional force or the frictional torque with high accuracy without being affected by the speed and acceleration before and after reversing the direction of motion. It is another object of the present invention to provide a friction compensation method and a friction compensator that can reduce the time required for parameter adjustment.
Another object of the present invention is to provide a motor control device capable of greatly improving the motion accuracy when performing a biaxial circular interpolation motion on a machine tool.

In order to achieve the above object, the present invention generates a speed command signal of the motor so that a position detection signal of the moving body fed by the motor and a position command signal coincide with each other, and detects the speed of the motor. Generating a torque command signal so that the signal and the speed command signal match, and controlling the torque of the motor based on the torque command signal, the frictional force generated when reversing the rotation direction of the motor or In the friction compensation method for generating a friction compensation signal for compensating the friction torque and making the correction value of the torque command signal,
Generating a real position signal by estimating a real position of the mobile body corresponding to the position command signal using a model of a control system in which the mobile body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Generating a displacement signal from a position that reverses the direction and obtaining an absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Obtaining a rate, multiplying the rate of change with respect to the displacement by the speed signal to calculate a rate of change of friction force or friction torque with respect to time, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
The characteristics from the torque command signal input to the torque controller to the motor torque actually output are modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Generating a friction compensation signal;
It is characterized by having.

Further, the present invention generates a speed command signal of the motor so that a position detection signal and a position command signal of a moving body fed and moved by the motor match, and the motor speed detection signal, the speed command signal, Friction compensation that generates a torque command signal so as to match, and compensates the frictional force or friction torque generated when reversing the rotation direction of the motor when controlling the torque of the motor based on the torque command signal In the friction compensator that generates a signal and sets the correction value of the torque command signal,
Means for estimating an actual position of the moving body corresponding to the position command signal and generating an actual position signal using a model of a control system in which the moving body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Means for generating a displacement signal from a position that reverses the direction and obtaining the absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Means for calculating a rate of change, calculating a rate of change of friction force or friction torque with respect to time by multiplying the rate of change with respect to the displacement by the speed signal, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
A characteristic from a torque command signal input to the torque controller to a motor torque actually output is modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Means for generating a friction compensation signal;
It is characterized by having.

In addition, the present invention provides a position controller that generates a speed command signal for the motor so that a position detection signal and a position command signal of a moving body that are moved by a motor match, a speed detection signal for the motor, A speed controller that generates a torque command signal so as to match the speed command signal, a friction compensator that generates a friction compensation signal that compensates for a friction force generated when the rotational direction of the motor is reversed, and the torque In a motor control device comprising a torque controller for controlling the torque of the motor based on a value obtained by adding a command signal and the friction compensation signal,
The friction compensator is:
Means for estimating an actual position of the moving body corresponding to the position command signal and generating an actual position signal using a model of a control system in which the moving body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Means for generating a displacement signal from a position that reverses the direction and obtaining the absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Means for calculating a rate of change, calculating a rate of change of friction force or friction torque with respect to time by multiplying the rate of change with respect to the displacement by the speed signal, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
The characteristics from the torque command signal input to the torque controller to the motor torque actually output are modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Means for generating a friction compensation signal;
It is characterized by including.

  According to the friction compensation method and the friction compensator according to the present invention, the velocity signal is obtained by differentiating the actual position signal of the moving body, and the displacement from the position where the moving body reverses the movement direction by integrating the speed signal. A signal is generated and its absolute value is obtained. Using a model representing the relationship between displacement and friction force or friction torque, the rate of change of the friction force or friction torque with respect to the displacement is obtained, and the rate of change with respect to this displacement is multiplied by the speed signal. Thus, the rate of change with respect to time is obtained, and the rate of change with respect to time is integrated to estimate the friction force or friction torque. The friction torque can be estimated with high accuracy.

  Further, according to the friction compensation method and the friction compensator according to the present invention, the model for estimating the actual position of the moving body, the model representing the relationship between the displacement and the friction force or the friction torque, and the torque command signal to the torque of the motor. Since many parameters of this model are already known and few parameters need to be adjusted substantially, the time required for parameter adjustment can be greatly reduced compared to the conventional model.

  Further, according to the motor control device of the present invention, as described above, since the friction compensator capable of estimating the frictional force or the frictional torque with high accuracy is a constituent element, the biaxial circular interpolation motion is performed by the machine tool. It is possible to greatly improve the motion accuracy when performing

  Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a friction compensator and a motor control apparatus including the same according to the present invention. In FIG. 1, a table 2 as a moving body that is fed by a motor 1 is supported by a linear guide mechanism (not shown) so that the motor 1 can rotate. Is converted into a straight motion of the table 2. Therefore, the position, speed and acceleration of the table 2 can be controlled by controlling the motor 1.

  In order to control the motor 1, a linear encoder (not shown) for detecting its position is attached to the table 2, and a tachometer or a rotary encoder (not shown) for detecting its speed is attached to the motor 1. ing. The position controller 11 generates a speed command signal for 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. Add to. The speed controller 12 generates a torque command signal so that the speed command signal applied from the position controller 11 matches the speed detection signal of the motor 1 detected by the tachometer or rotary encoder, and sends it to the adder 14. Add. The friction compensator 13 generates a friction compensation signal for compensating a friction force generated when the rotation direction of the motor 1 is reversed based on the position command signal applied from the host controller, and applies the friction compensation signal to the adder 14. An 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 the servo amplifier 15 as a torque controller. Add. The servo amplifier 15 controls the armature current of the motor 1 so as to generate a torque that is as faithful as possible to the friction-compensated torque command signal.

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

  The frictional force in the drive mechanism of the table 2 shown in FIG. 1 changes rapidly when the motion direction of the table 2 is reversed, that is, when the rotation direction of the ball screw 3 is reversed. The response of the control system cannot cope with this change, and for example, quadrant projections are generated when circular cutting is performed by performing circular interpolation movement using two orthogonal axes as described above. The friction compensator 13 is for correcting the influence of the frictional force when the movement direction of the table 2 is reversed.

  In view of this, the inventor, in a feed drive system using a ball screw and a linear motion rolling guide, reciprocates a sine wave on a table with an amplitude of 50 μm (micrometers) and a period of 4 s (seconds) in which the friction force is considered to be unaffected by speed and acceleration. It was found that the motor torque was almost equal to the non-linear friction torque in terms of the motor shaft when the motor was moved and the temporal change of the motor torque was measured. FIG. 2A is a diagram showing a temporal change in the friction torque corresponding to the motor torque. When the horizontal axis is plotted as the table displacement and the vertical axis is plotted as the friction torque based on the measurement result, FIG. A diagram showing the relationship between displacement and friction torque as shown in FIG. As is apparent from FIG. 2B, the displacement and the friction torque are almost proportional in the region where the displacement is 10 μm or less, and the friction torque in the region where the displacement is 10 μm to 40 μm is substantially constant. In addition, the same characteristic is exhibited in the return (return) motion, and the friction torque draws a hysteresis loop according to the reciprocating motion.

  In the actual motion affected by the speed and acceleration, the control system cannot cope with the change of the friction torque as shown in FIGS. 2A and 2B, and a motion error occurs. Conversely, if the motor torque is made to completely follow the change of the friction torque, a servo system that does not cause a motion error due to friction can be realized.

In the present embodiment, the friction characteristics as shown in FIGS. 2A and 2B are modeled 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) ... (1)
However,
f: Friction torque [Nm]
x ′: Displacement from a position where the moving body reverses the moving direction a: Friction force or frictional torque gradient f _c against the displacement of the moving body in a minute displacement region of the moving body f _c : Friction when the displacement of the moving body is sufficiently large Torque [Nm]
sgn: sign function (+1 when dx ′ / dt > 0, 0 when dx ′ / dt = 0, −1 when dx ′ / dt <1)
It is. FIG. 3A shows the change in the friction torque during the reciprocating motion obtained by calculating the friction torque f during the sinusoidal reciprocating motion using the above equation (1), and shows the relationship between the displacement and the friction torque. Each is shown in 3 (b). As is apparent from FIGS. 3A and 3B, it can be seen that the actual change in friction torque can be estimated from the above equation (1).

Thus, if the change in the friction torque at the time of reversal of the motion direction is estimated in advance by the above equation (1) and the correction value is used to correct the torque command signal of the servo system, the influence of friction can be compensated. Conceivable. However, even if a torque command signal subjected to friction compensation obtained by correcting the torque command signal by the above equation (1) is added to the servo amplifier 15 due to a delay element existing in each of the servo amplifier 15 and the motor 1. The torque actually output from the motor 1 will be different. In general, the delay element between the servo amplifier 15 and the motor 1 is modeled by a torque command filter 16 and a current loop 17 as shown in 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, T _i Is the time constant [s] of the current loop, and s is the Laplace operator.

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

  FIG. 5 is a block diagram showing a detailed configuration of the friction compensator 13 that solves the above problem, together with related signal waveforms. In FIG. 5, the actual position estimation unit 21 inputs a position command signal applied from the host controller, and uses the model of the servo control system in which the table 2 is fed and moved to determine the actual position of the table 2 corresponding to the position command signal. An actual position signal is generated by estimation. The actual position estimator 21 is connected to a differentiator 22 that differentiates the actual 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 sign inversion detection unit 23 and the velocity signal are integrated to restore the actual position signal. Every time a reset signal is output from the sign inversion detection unit 23, the integration value is reset to zero and the table 2 changes the direction of motion. An integrator 24 that generates a displacement signal from the reversal position is connected to the integrator 24. Further, the integrator 24 is connected to an absolute value calculation unit 25 that calculates an absolute value of the output.

  The absolute value calculation unit 25 uses a model representing the relationship between the displacement from the position where the table 2 reverses the direction of motion and the friction torque, and the friction torque displacement (position) as a function of the displacement signal represented by the absolute value. ) Is connected to a friction characteristic estimation unit 26 for obtaining a change rate with respect to (). A multiplier 27 is provided for calculating the rate of change of the friction torque with respect to time by multiplying the rate of change with respect to the displacement output from the friction characteristic estimation unit 26 and the speed signal output from the differentiator 22. An integrator 28 is provided at the output terminal of the multiplier 27. The integrator 28 estimates the friction torque by integrating the rate of change of the friction torque with respect to time. The integrator 28 models the characteristics from the torque command signal input to the servo amplifier 15 to the actually output torque of the motor 1, and multiplies the estimated friction torque by the inverse function of the transfer function of the model. Then, a response delay compensation unit 29 for generating a friction compensation signal is connected.

FIG. 6 is a block diagram showing a detailed configuration of the response delay compensation unit 29, which includes a coefficient block 31, a differentiation block 32, an adder 33, a differentiation block 34, and an adder 35. 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] of the current loop described above, s is the Laplace operator described above. T _rg is a conversion constant from the torque command signal to torque.

The operation of the friction compensator 13 configured as described above will be described below. First, when a position command signal r is applied from a host controller (not shown), the actual position estimation unit 21 estimates an actual position of the table 2 according to the following equation (2) and generates an actual position signal x _e (t).
x _e (t) = {1 / (T _c s + 1)} r (2)
However,
T _c : Delay time constant of the entire servo system s: Laplace operator.

The actual position signal x _e (t) generated by the actual position estimation unit 21 is differentiated by the differentiator 22 and output as a speed signal dx _e / dt, and is added to the sign inversion detection unit 23, the integrator 24 and the multiplier 27. It is done. The sign inversion detection unit 23 detects that the sign of the speed signal dx _e / dt is inverted and outputs a reset signal. The integrator 24 outputs the position signal again by integrating the speed signal dx _e / dt. However, since the integrator 24 is reset every time a reset signal is applied from the sign inversion detection unit 23, the integrator 24 is displaced from the position where the motion direction is reversed. Output as signal ± x '. The absolute value calculator 25 obtains the absolute value of the displacement signal ± x ′ and outputs the displacement signal x ′. The friction characteristic estimator 26 calculates the change rate of the friction torque with respect to the displacement, that is, the friction characteristic as a function of the displacement signal x ′ by the following equation (3). Equation (3) is obtained by first-order differentiation of the above equation (1) with the displacement signal x _e .
df _e / dx _e = 2af _c {1-tanh ² (ax ′ )} (3)

If the rate of change df _e / dx _e of the friction torque with respect to the displacement obtained by the equation (3) is multiplied by the speed signal dx _e / dt output from the differentiator 22, the differential value of the estimated value of the friction torque is Become. Therefore, the multiplier 27 performs the calculation of the following equation (4).
df _e / dt = (df _e / dx _e ) · (dx _e / dt) (4)

Next, the integrator 28 integrates the differential value df _e / dt of the estimated value of the friction torque to calculate the estimated value f _e (t) of the friction torque. The response delay compensation unit 29 performs 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 compensator 29 is configured as shown in the block diagram of FIG. In other words, a friction compensation signal is generated by multiplying the estimated friction torque f _e (t) by the inverse function of the transfer function indicating the characteristic from the torque command signal to the actually output motor torque. In FIG. 6, T _f is a time constant [s] of the torque command filter, T _i is a time constant [s] of the current loop, s is a Laplace operator, and T _rg is a conversion constant from the torque command signal to the friction torque. It is.

  Next, in order to confirm the effect of the motor position control device described above, the case where the circular interpolation motion is performed without applying the present invention and the case where the circular interpolation motion is performed by applying the present invention are compared. And FIG. 7 is a perspective view showing a schematic configuration of a motor control device that performs circular interpolation motion. Servo motors 42 that drive the XY table 41 in the X direction and the Y direction include an X axis servo amplifier 43 and a Y axis servo amplifier, respectively. The personal computer (hereinafter abbreviated as “PC”) 50 is connected to the personal computer 50. Further, 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 DSP (Digital signal Processor) function, and has the functions of the position controller 11, the speed controller 12, and the friction compensator 13 shown in FIG. 1.

  First, a conventional motor control device (for example, partial model matching method (Toshiyuki Kitamori: control system design method based on partial knowledge of controlled object, Transactions of the Society of Instrument and Control Engineers, Vol. 15, No. 4, ( 1979), pp 549 to 555) (Yuide Ide, Ryuta Sato, Masaomi Tsutsumi: Control system design of feed drive system by partial model matching method, 2005 JSPE Spring Conference Lecture Meeting FIG. 8 shows the result of examining the error when circular interpolation motion is performed using the paper collection, (2005), pp 1133 to 1134). FIG. 8 shows the error between the ideal arc locus and the actual locus magnified 1000 times. Of these, FIG. 8A shows an arc locus when the feed rate is 3 m / min and the radius is 25 mm, and FIG. 8B shows an arc locus when the feed rate is 6 m / min and the radius is 25 mm. FIG. 8C shows an arc locus when the feed rate is 3 m / min and the radius is 10 mm. In all of the results shown in FIGS. 8A, 8B, and 8C, protrusion-like trajectory errors, that is, quadrant protrusions are generated around 0 °, 90 °, 180 °, and 270 °. Among these, 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 protrusion-like trajectory error in the vicinity of each reversal position is a response of the servo system to the change in the frictional force at the time of reversing the motion direction on the circular arc trajectory.

  Next, FIG. 9 shows the result of examining the error when the circular interpolation motion is performed by applying the friction compensator according to the present invention. FIGS. 9A, 9B, and 9C show the results of circular interpolation motion at the same speed and radius as those shown in FIGS. 8A, 8B, and 8C, respectively. is there. In all of the results shown in FIGS. 9A, 9B, and 9C, the protrusion-like trajectory errors in the vicinity of 0 °, 90 °, 180 °, and 270 ° are eliminated, and the motion accuracy is greatly improved. You can see that.

In the friction compensator according to the present invention, the delay time constant T _c of the servo system, the friction torque f _c converted to the motor shaft, the rising coefficient a of the friction torque, the time constant T _f of the torque command filter, the time constant of the current loop If the six parameters of T _i and the torque command-to-torque conversion constant T _rg are set once, it is not necessary to readjust the parameters even if the radius of the circular motion and the feed rate change. Also, parameters related to friction, namely, the case parameters other than the rising coefficient a of the friction torque f _c and friction torque of the motor shaft conversion is known there are many, are substantially adjustment is necessary parameters f _c and a 2 There is only one. Therefore, the time required for parameter adjustment can be greatly reduced as compared with the conventional friction compensator.

  According to the friction compensator according to the present invention, the rate of change with respect to the displacement of the friction force or the friction torque is obtained, the rate of change with respect to the displacement is multiplied by the speed signal to obtain the rate of change with respect to time, and the rate of change with respect to time is integrated. Since the friction force or friction torque is estimated, the friction force or friction torque can be estimated with high accuracy without being affected by the speed and acceleration before and after the motion direction is reversed. If the motor control device is configured with the machine as an element, the motion accuracy of the numerically controlled machine tool, the three-dimensional measuring machine, the semiconductor manufacturing related device, and the robot can be improved.

1 is a block diagram showing a schematic configuration of an embodiment of a friction compensator and a motor control device including the same according to the present invention. It is a diagram which shows the temporal change of the friction torque when a table is reciprocated by a sine wave by a feed drive system, and the relationship between displacement and torque. It is a diagram showing the temporal change of the friction torque obtained by calculating using the approximate expression representing the relationship between the displacement from the position where the table reverses the direction of motion and the friction torque, and the relationship between the displacement and the torque. It is a block diagram which shows the delay element of a servo amplifier and a motor. It is the block diagram which showed the detailed structure of one Embodiment of the friction compensator which concerns on this invention with the related signal waveform. It is a block diagram which shows the detailed structure of the response delay compensation part which comprises one Embodiment of the friction compensator which concerns on this invention. It is a perspective view which shows schematic structure of the motor control apparatus which performs circular interpolation motion. It is the figure which showed the difference | error of the ideal circular locus | trajectory at the time of performing circular interpolation movement using the conventional friction compensator, and an actual locus | trajectory. It is the figure which showed the error of an ideal circular locus | trajectory at the time of performing circular interpolation motion using the friction compensator which concerns on this invention, and an actual locus | trajectory.

Explanation of symbols

DESCRIPTION OF SYMBOLS 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 Actual position estimation part 22 Differentiator 23 Sign inversion detection part 24, 28 Integrator 25 Absolute value calculation unit 26 Friction characteristic estimation unit 27 Multiplier 29 Response delay compensation unit

Claims (5)

A speed command signal of the motor is generated so that a position detection signal of the moving body fed by the motor and a position command signal match, and a torque is set so that the speed detection signal of the motor matches the speed command signal. Generating a command signal, and controlling the torque of the motor based on the torque command signal, generating a friction compensation signal for compensating a frictional force or a friction torque generated when reversing the rotation direction of the motor, In the friction compensation method as the correction value of the torque command signal,
Generating a real position signal by estimating a real position of the mobile body corresponding to the position command signal using a model of a control system in which the mobile body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Generating a displacement signal from a position that reverses the direction and obtaining an absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Obtaining a rate, multiplying the rate of change with respect to the displacement by the speed signal to calculate a rate of change of friction force or friction torque with respect to time, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
The characteristics from the torque command signal input to the torque controller to the motor torque actually output are modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Generating a friction compensation signal;
A friction compensation method comprising: The model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque,
Based on the relationship between the displacement of the moving body and the motor torque when the moving body is reciprocated in a sinusoidal wave with an amplitude and period that is not affected by speed and acceleration, a friction force or a friction torque is a function of the displacement of the moving body. The friction compensation method according to claim 1, which is an approximate expression expressed as: Friction force or the friction torque is f,
The displacement from the position where the moving body reverses the movement direction is represented by x ′,
The slope of the frictional force or frictional torque with respect to the displacement of the moving body in the minute displacement region of the moving body is a,
The friction force or the friction torque when the displacement of the moving body is sufficiently large is expressed as f _c ,
Let the sign function be sgn,
The approximate expression is
_{f = f c (2tanh (ax} ') - 1) sgn (dx' / dt)
The change rate df _e / d x _e of the frictional force or the friction torque with respect to the displacement is expressed by the following equation: df _e / d x _e = 2af _c {1- tanh ² (ax ′)}
The friction compensation method according to claim 2, wherein the friction compensation method is obtained according to: A speed command signal of the motor is generated so that a position detection signal of the moving body fed by the motor and a position command signal match, and a torque is set so that the speed detection signal of the motor matches the speed command signal. Generating a command signal, and controlling the torque of the motor based on the torque command signal, generating a friction compensation signal for compensating a frictional force or a friction torque generated when reversing the rotation direction of the motor, In the friction compensator used as the correction value of the torque command signal,
Means for estimating an actual position of the moving body corresponding to the position command signal and generating an actual position signal using a model of a control system in which the moving body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Means for generating a displacement signal from a position that reverses the direction and obtaining the absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Means for calculating a rate of change, calculating a rate of change of friction force or friction torque with respect to time by multiplying the rate of change with respect to the displacement by the speed signal, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
A characteristic from a torque command signal input to the torque controller to a motor torque actually output is modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Means for generating a friction compensation signal;
A friction compensator characterized by comprising. A position controller that generates the speed command signal of the motor so that the position detection signal and the position command signal of the moving body moved by the motor match, and the speed detection signal of the motor and the speed command signal match. A speed controller for generating a torque command signal, a friction compensator for generating a friction compensation signal for compensating a friction force generated when the rotational direction of the motor is reversed, the torque command signal and the friction compensation In a motor control device comprising a torque controller for controlling the torque of the motor based on a value obtained by adding the signal,
The friction compensator is:
Means for estimating an actual position of the moving body corresponding to the position command signal and generating an actual position signal using a model of a control system in which the moving body is fed;
Differentiating the actual position signal into a speed signal, integrating the speed signal to restore the actual position signal, and resetting the integrated value to zero when the sign of the speed signal is reversed, the moving body moves Means for generating a displacement signal from a position that reverses the direction and obtaining the absolute value thereof;
Using a model representing the relationship between the displacement from the position where the moving body reverses the direction of motion and the frictional force or frictional torque, changes to the displacement of the frictional force or frictional torque as a function of the displacement signal expressed in absolute value Means for calculating a rate of change, calculating a rate of change of friction force or friction torque with respect to time by multiplying the rate of change with respect to the displacement by the speed signal, and estimating the friction force or friction torque by integrating the rate of change with respect to time When,
The characteristics from the torque command signal input to the torque controller to the motor torque actually output are modeled, and the estimated friction force or friction torque is multiplied by the inverse function of the transfer function of the model. Means for generating a friction compensation signal;
A motor control device including the motor control device.

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