JP2007072943A - Position control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position control device capable of determining a feed forward gain by simple algebra calculation.
SOLUTION: A position control means 21 for performing a proportional operation on a position deviation and outputting a speed command, and a speed control means 22 for performing a proportional and integral operation on the speed deviation and outputting it, and generating a torque command When provided with speed feedback control systems 22 to 27 for driving the controlled object, and feedforward control means 30 for outputting a speed command compensation amount for compensating for a delay of the speed feedback control system and adding it to the speed control means, the feedforward control means The differential means 31 for differentiating and outputting the position command, the low-pass filter means 32 for inputting the output of the differential means and outputting only the low-frequency component, and the inverse of the transfer function of the speed feedback control system And feedforward compensation means 33 that multiplies the output of the filter means and outputs the result.
[Selection] Figure 4

Description

  The present invention relates to a position control device having a feedforward control function.

  Currently, feedforward control is introduced in NC machine tools and robots in order to improve the follow-up performance. However, the design of the feedforward compensator has a problem that advanced technology based on experience and a great deal of time are required. Many methods have been proposed to solve such problems. Among them, conventional examples that are considered to be closely related to the present invention are listed below.

<First Conventional Example>
When tuning the feed drive system control system that governs the shape creation of NC machine tools, the feedforward gain is the Laplace of the tracking error e (t) so that the tracking error in the steady state with respect to the speed step input is zero. It is shown that the final value theorem is obtained from the transformation E (s) (for example, see Non-Patent Document 1 below).

<Second Conventional Example>
In order to perform the optimum adjustment of the positioning state in a short time, when each feedforward controller of position compensation and speed compensation is performing feedforward control with two feedforward gains, the value of these feedforward gains. It is shown that the positioning state of the mechanical system is optimized only by adjusting the adjustment gain by setting the value of the monotonically increasing function with the adjustment gain as an argument (see, for example, Patent Document 1 below).

<Third conventional example>
As a positioning servo controller that can easily realize the required response characteristics even when adjusting the disturbance response, a feedforward controller is added to the feedback controller to make the control system a two-degree-of-freedom system, and the feedback gain and feed It has been shown that the gain adjustment for determining the response characteristic required only by adjusting the adjustment gain can be simplified by using the forward gain as a monotonically increasing function having the adjustment gain as an argument (for example, Patent Document 2).

<Fourth Conventional Example>
As a position control device that realizes control that finely adjusts the minute model error of the controlled object while maintaining the response to disturbance optimally, and realizes control with high speed without exciting mechanical resonance by simple adjustment. The model position, model speed, and model torque calculated by the model signal calculation unit are used as input for position, speed, and torque feedforward control. If there is a model error, the feedforward gain can be adjusted independently. Is finely adjusted (see, for example, Patent Document 3 below).

<Fifth conventional example>
It is possible to automatically select and set the controller used in each control unit constituting the motor control device according to the control target, so that a wide variety of control targets can be controlled with high performance. As an electric motor controller, it is shown that an excitation signal is input to a feedback controller to identify the frequency characteristics of a control target, and a feedforward controller and a feedback controller are automatically selected based on the identified model. (For example, see Patent Document 4 below).

<Sixth Conventional Example>
As a servo control device that can significantly reduce the position deviation by quickly and automatically adjusting the feed forward gain, when the control system operates according to the command from the command value generator and drives the controlled machine, the feed forward gain error When the estimation unit operates and estimates the gain error from the deviation from the command value of each output and outputs it to the feedforward control unit, the feedforward control unit detects the position error relative to the control system based on the estimated gain error. It is shown that the feedforward gain is adjusted to be 0 (see, for example, Patent Document 5 below).

Yoshiaki Kakino et al .: Study on feed drive system total tuning in NC machine tools (2nd report), Journal of Precision Engineering, Vol.60, No.2, (1995) JP 2001-350525 A (summary) JP 2001-356822 A (summary) JP 2001-249720 A (summary) JP 2005-198404 (Abstract) JP-A-6-250702 (summary)

  However, in the first and fourth conventional examples described above, although the adjustment procedure is determined, in reality, vibrations, speed overshoots, etc. occur in the response due to the effects of machine rigidity, etc. In the second and third conventional examples, if one gain is determined empirically, other gains are determined, but the first one gain is determined. Had the problem of requiring specialized knowledge. Furthermore, when the methods described in the first to fourth conventional examples are implemented, it is necessary to adjust the gain by the operator, and there is a problem that the adjustment must be repeatedly performed to obtain an optimum response. there were.

  Further, in the first to fourth conventional examples described above, the feedforward gain is fixed at the adjusted value. Therefore, an error may occur without being able to follow the position command with a different motion state. In the fifth and sixth conventional examples, there is a problem that an arithmetic device for automatically adjusting the gain is required when a tracking error occurs.

  The present invention was made in order to solve the above-described problems of the conventional example, and the purpose thereof is to determine the feedforward gain by simple algebra calculation without having a high level of expertise. Another object of the present invention is to provide a position control device that does not require adjustment of the feedforward gain while observing the response after the determination of the feedforward gain.

  Another object of the present invention is to provide a position control device capable of following a position command having a different motion state.

In order to achieve the above-mentioned object, the present invention multiplies the deviation between the position command of the torque-controlled object to be controlled and the actual position detection signal by a proportional gain and outputs it as the speed instruction of the object to be controlled. And a speed control means for outputting a sum of a value obtained by multiplying a deviation between the speed command and the actual speed detection signal to be controlled by a proportional gain and a value obtained by performing an integral operation, and the speed control means A speed feedback control system that generates a torque command for the control object based on the output of the control signal, and torque drives the control object in accordance with the torque command; Position control comprising: a feedforward control means for outputting a compensation amount and adding to the speed control means as a compensation amount for the speed command outputted from the position control means In the location,
The feedforward control means includes
Differentiating means for differentiating and outputting the position command;
Low-pass filter means having a cut-off frequency substantially coinciding with the cut-off frequency of the speed feedback control system, inputting the output of the differentiating means and outputting only a low-frequency component;
A feedforward gain obtained by multiplying the output of the low-pass filter means by the feedforward gain, using the reciprocal of the transfer function of the speed feedback control system when regarded as a second-order lag system of the speed feedback control system as a feedforward gain. Forward compensation means,
It is characterized by having prepared.

  In the present invention, since the reciprocal of the transfer function of the speed feedback control system when regarded as a second-order lag system of the speed feedback control system is used as a feedforward gain, simple algebra calculation can be performed even without a high level of expertise. Provided is a position control device that can determine a feedforward gain and does not need to adjust the feedforward gain while looking at the response after the determination of the feedforward gain.

  Further, according to the present invention, the feedforward control means has a differentiating means for differentiating and outputting the position command, and a cut-off frequency that substantially coincides with the cut-off frequency of the speed feedback control system. Since it is composed of a low-pass filter means that outputs only the component, and a feedforward compensation means that regards the reciprocal of the transfer function of the speed feedback control system as a feedforward gain that is regarded as a second-order lag system of the speed feedback control system. Since the order of the numerator and the order of the denominator of the feedforward control means are the same, a position control device capable of following a position command having a different motion state is provided.

Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings.
FIG. 1 is a perspective view showing a schematic configuration of a feed drive mechanism 10 as a control target to which the present invention is applied. In FIG. 1, linear ball bearing guide rails 12 and 12 are mounted in parallel on both sides of the surface of a substrate 11 having a rectangular planar shape, and a motor fixing base 13 is mounted on one end in the longitudinal direction. Has been. A servo motor 14 is mounted on the outer end surface of the motor fixing base 13, and an output shaft of the servo motor 14 protrudes in an intermediate portion of the guide rails 12 and 12. On the extension of the output shaft of the servo motor 14, a pair of shaft support tables 15, 15 are mounted separately. End portions of ball screws 16 that engage with the nuts 17 are supported on the shaft support bases 15 and 15 via radial bearings 19, respectively. A work table 18 is mounted so as to overlap a part of the guide rails 12 and 12 in the longitudinal direction. Linear ball bearings are mounted on both sides of the work table 18 on the back side shown in the drawing, and a nut 17 is mounted on the center.

  The feed drive mechanism 10 shown in FIG. 1 converts the rotation of the servo motor 14 into a linear motion of the work table 18 by the ball screw 16 and the nut 17 and is used as a part of a servo system of a general NC machine tool. Has been. In such a servo system, since the natural frequency of the feed drive mechanism 10 is sufficiently larger than the natural frequency of the servo system, it can be expressed by a dynamic model as shown in FIG. The dynamic model can be expressed by the equation of motion shown in the following equation (1).

Where θ is the rotation angle [rad] of the servo motor, x _t is the displacement of the table (hereinafter also used as a detection signal for the actual position) [m], l is the lead of the ball screw [m], and T _m is the servo. Motor torque [Nm], c is a viscous friction coefficient (hereinafter abbreviated as viscosity coefficient) [Nm / (rad / s)] in terms of motor shaft, and f is a friction torque [Nm] in terms of motor shaft. J is the total moment of inertia [kgm ² ] of the feed drive mechanism in terms of the motor shaft. From the moment of inertia J _b [kgm ² ] of the servo motor and ball screw and the mass M _t [kg] of the table and ball screw It is calculated by the following equation (2).

FIG. 3 is a block diagram showing the configuration of an embodiment of the position control device according to the present invention. In this embodiment, the above-described feed drive mechanism 10 is a control target, and a control system is added to the control target to constitute a servo system. This servo system includes a position feedback control including a speed feedback control system as a minor loop. It is a system. In Figure 3, the position control means 21 to output as the position subtracts the detection signal x _t of the actual position from the command r, the speed command by multiplying a proportional gain K _pp on the difference with respect to the work table 18, its output The speed control means 22 is connected to. The speed control means 22 adds the speed command output from the position control means 21 and the speed command compensation output from the feedforward control means 30 described later in detail, and detects the rotational speed of the ball screw 16 from the sum. The value obtained by subtracting the signal and multiplying the obtained value by the proportional gain K _vp and the value integrated by the integral gain K _vi are added and output as a torque command. Is connected to converter gain multiplication means 23 for multiplying a converter gain DA for conversion into an electrical signal, for example, a voltage signal. The converter gain multiplication means 23 is further connected to an adjustment gain multiplication means 24 for multiplying and outputting a torque command adjustment gain T _rg for adjusting the relationship between the torque command and the output of the torque control amplifier (not shown). ing. At the output end of the adjustment gain multiplication means 24, there are a torque command filter means 25 having a torque command filter time constant T _f [s] and a torque control delay means 26 having a torque control delay time constant T [s]. The torque commands connected in sequence and output from the torque control delay means 26 are applied to a torque control device (not shown). The torque control device adds the torque command applied thereto and the friction torque f [Nm] converted from the motor shaft set from the outside, and controls the output torque of the servo motor 14 according to the sum. Here, the feed drive mechanism including the servo motor 14 is represented by an inertia moment element 27, an integration element 28, and a motion conversion element 29.

  Among the above components, the speed control unit 22, the converter gain multiplication unit 23, the adjustment gain multiplication unit 24, the torque command filter unit 25, the torque control delay unit 26 and the inertia moment element 27 constitute a speed feedback control system. The speed feedback control system, the position control means 21, the integration element 28, and the motion conversion element 29 constitute a position feedback control system.

Further, in parallel with the position control means 21, a feedforward control means 30 for differentiating the position command r with a feedforward gain _Kff (s) and outputting it as a speed command compensation is provided. As shown in the block diagram of FIG. 4, the feedforward control means 30 has a differentiating means 31 for differentiating and outputting the position command r, and a cut-off frequency that substantially matches the cut-off frequency of the speed feedback control system. The low-pass filter means 32 that inputs the output of the differentiation means 31 and outputs only the low-frequency component, and the reciprocal number of the transfer function of the speed feedback control system when regarded as the second-order lag system of the speed feedback control system and then, and a feed-forward compensation means 33 for outputting by multiplying the feed to the output of the low pass filter means 32 forward gain K _ff (s).

  The overall operation of the servo system configured as described above can be easily understood by those skilled in the art, and will not be described. However, even if speed and position feedback control is performed, the servo delay It is a problem that a tracking error due to. The present embodiment is provided with the feedforward control means 30 shown in FIG. 4 for the purpose of suppressing this tracking error, and the detailed configuration and design procedure will be described below.

When the servo system is constructed as shown in FIG. 3 with the feed drive mechanism 10 shown in FIG. 1 as the control target, the table displacement x _{t is determined} from the position command r by setting the transfer function of the speed feedback control system as G _v (s). The closed loop transfer function up to is expressed by the following equation (3).

In this servo system in order to follow the table displacement x _t so that the error is not in the position command r, the gain of the transfer function from the position command r to table displacement x _t may be such that the 1. Therefore, when the feed-forward gain K _ff (s) is solved with the left side of the equation (3) as 1, the following equation (4) is obtained.

From equation (4), the feedforward gain K _ff (s) is obtained from the reciprocal of the transfer function G _v (s) of the speed feedback control system and the lead l of the ball screw 16. However, it is necessary to consider the delay of the speed feedback control system in determining the feedforward gain K _ff (s). Therefore, in this embodiment, it is considered as a second-order lag system of the speed feedback control system so that the feedforward control means 30 satisfies the following expression (5).

Here, the cut-off frequency ω _n is the loop gain of the speed feedback control system, which is the proportional gain K _vp of the speed feedback control system, the converter gain DA, the torque command adjustment gain T _rg, and the total moment of inertia J of the feed drive mechanism 10. It can be obtained as shown in the following equation (6).

When the feedforward control means 30 is designed as shown in the equation (5), since the order of the numerator is larger than the order of the denominator, the cutoff frequency is almost _equal to the cutoff frequency ω _n of the speed feedback control system. It is necessary to introduce an equal low-pass filter to increase the denominator order.

Therefore, as shown in FIG. 4, the feedforward control means 30 is constituted by the differentiation means 31, the low-pass filter means 32 and the feedforward compensation means 33, and thereby, first, the position command value input by the differentiation means 31. r is differentiated to obtain a speed command value, and after passing through the low-pass filter means 32, the speed command compensation is output by the feedforward compensation means 33 having the transfer function K _ff (s) shown in the equation (5).

FIG. 5 is a flowchart showing an example of the design procedure of the feedforward control means 30. Here, in step S101, the total moment of inertia J of the feed drive mechanism 10 is calculated, and in step S102, the filter time constant _Tf , the signal converter gain DA, and the torque command adjustment gain _Trg are examined. In step S103, the cutoff frequency ω _n of the speed feedback control system is calculated according to the equation (6). In step S104, the lead 1 of the ball screw 16 of the feed drive mechanism 10 is checked. In step S105, a feedforward compensation element having a transfer function of equation (5) is constructed. In the final step S106, as shown in FIG. 4, a third-order low-pass filter having a cutoff frequency ω _n is constructed.

FIG. 6 is a flowchart showing an example of a processing procedure when the function of the feedforward control means 30 is given to a personal computer. In this case, the position command r is time-differentiated in step S201, and low-pass filter processing is executed on the time differential value in step S202. Next, the value subjected to the low-pass filter processing in step S203 is multiplied by the feedforward gain K _ff (s) to obtain the speed command compensation, and then in step S204, the speed command compensation is added to the speed command.

  As is clear from the above description, according to the present invention, the feedforward gain can be determined by simple algebra calculation without having a high level of expertise, and a response is obtained after the determination of the feedforward gain. A position control device is provided that does not require adjustment while looking.

In the above-described embodiment, the case where the control target is a feed drive mechanism using a ball screw has been described. However, the present invention is not limited to this and may be applied to position control of an electric motor. it can. In this case, the motion conversion element 29 in FIG. 3 may be removed and the output θ of the integration element 28 may be fed back to the position control means 21 as a position detection signal.
In the above embodiment, the torque command is converted into the voltage signal by the converter gain multiplication means 23. However, the torque command is not limited to the voltage signal, and may be a current signal or a frequency signal. As long as the signal is good.
Furthermore, in the above embodiment, the converter gain multiplication unit 23 and the adjustment gain multiplication unit 24 are provided. However, the signal converter gain DA and the torque command adjustment gain T _rg are combined into a single gain multiplication unit. It is good.

Next, an experimental example in which the above-described position control device is applied to an XY drive mechanism and the error of its ramp response and circular interpolation motion is examined is taken as a first embodiment, and applied to a 5-axis control machining center to perform blade shape processing. An experimental example will be described below as a second embodiment.
<First embodiment>
FIG. 7 is a perspective view showing a schematic configuration of the XY drive mechanism 40 to which the above-described position control device is applied. The servo motors that drive the XY table 41 in the X direction and the Y direction are respectively an X axis servo amplifier 42 and a Y axis. The servo amplifier 43 is connected to a personal computer (hereinafter abbreviated as PC) 50. In addition, two linear encoders 44 are provided to detect the position in the X direction and the position in the Y direction of the XY table 41. The PC 50 has a DSP (Digital signal Processor) function, and has the functions of the position control means 21, speed control means 22, converter gain multiplication means 23, adjustment gain multiplication means 24 and feedforward control means 30 shown in FIG. I have it. The X-axis servo amplifier 42 and the Y-axis servo amplifier 43 have the functions of the adjustment gain multiplication means 24, torque command filter means 25, and torque control delay means 26 shown in FIG. 3, respectively, and torque control omitted in FIG. It has the function of an amplifier.

Here, many adjustment methods for the proportional gain K _pp , the velocity proportional gain K _vp , and the speed integral gain K _vi have been proposed so far. In the first embodiment, the partial model matching method (Toshiyuki Kitamori: Design method of control system based on partial knowledge, Proceedings of the Society of Instrument and Control Engineers, Vol. 15, No. 4, (1979), pp 549-555) (Yoshi Ide, Ryuta Sato, Masaomi Tsutsumi) The above servo gains were adjusted according to the control system design method of the feed drive system by the partial model matching method, the 2005 Annual Meeting of the Precision Engineering Society Spring Conference, (2005), pp 1133 to 1134). The servo gain used is shown in Table 1 below. Further, a third-order Butterworth filter, which is a kind of low-pass filter, is used as the filter of the feedforward control means 30, and its cutoff frequency is substantially the same as the cutoff frequency ω _n of the speed feedback control system. Set.

  When the servo gain was adjusted as described above and the lamp response was examined by setting the cut-off frequency of the Batterworth filter, the characteristics indicated by the wavy line in FIG. 8 were obtained. For comparison, when the lamp response when the feedforward control was not performed was examined, the characteristic indicated by the thick solid line in FIG. 8 was obtained. Comparing these two characteristics, when feedforward control is not performed, there is a steady deviation from the command indicated by a thin solid line, but when the feedforward control of the present invention is introduced, the response is somewhat oscillatory. It can be seen that the command is being followed.

  Next, when the X-axis and Y-axis were driven simultaneously to perform a circular interpolation motion with a radius of 25 mm and a feed rate of 3000 mm / min, the results shown in FIG. 9 were obtained. The locus in FIG. 9 is obtained by enlarging the radial error by about 1000 times. (A) shows a case where feedforward control is not performed for comparison, and (b) shows a general-purpose control system for comparison. The case of the conventional feedforward controller used is shown, and (c) shows the case where the feedforward control of the present invention is introduced. When these three characteristics are compared, when the feedforward control shown in (a) is not performed, a phenomenon that the radius decreases smaller than the target radius occurs due to the servo delay, as shown in (b). In the control by the conventional feedforward controller, most of the target radius protrudes outside the target radius, and the control using the feedforward control of the present invention shown in FIG. It can be seen that it is following correctly.

<Second embodiment>
FIG. 10 is a perspective view showing a schematic configuration of a 5-axis control machining center 60 that applies the present invention to perform blade shape machining. The rigid and rigid bed 61 includes a gate-shaped mounting base 62 integrated with the bed 61 in the front rear part, and an X-axis drive mechanism 63 is attached to the upper end of the mounting base 62, and its movable part. A Z-axis drive mechanism 64 is attached to the front. The Z-axis drive mechanism 64 has a rotary shaft supported in the vertical direction, and can be cut by attaching an end mill (not shown) as a tool to the lower end thereof. Further, a Y-axis drive mechanism 65 that is reciprocally driven in the front-rear direction, that is, the Y direction, is provided at the center of the bed 61 in the left-right direction. This Y-axis drive mechanism 65 mounts a workpiece, and rotates it in the direction of arrow A with the X-axis direction as the axis, and C-axis movement in which it rotates in the direction of C arrow with the Z-axis direction as the axis. Are provided at the same time.

  FIG. 11 shows a simulation assuming that an airfoil is machined using a 5-axis control machining center 60 with the end mill placed perpendicularly to the blade surface (Yuya Yokobori, Ryuta Sato, Masaomi Tsutsumi: including the swivel axis in the 5-axis control machining center. Analysis of feed drive system behavior, Proceedings of the 5th Annual Meeting of the Japan Society of Mechanical Engineers, Production Processing and Machine Tool Division, (2004) pp153-154) The relationship between the shape of the blade tip and the axial speed of the rotating shaft was shown. It is explanatory drawing. In FIG. 11, in order to apply the end mill 71 perpendicularly to the surface of the workpiece 72 and perform the airfoil processing along the feed direction 73, the AC shaft drive mechanism 66 for the workpiece 72 is used with the A axis inclined 90 degrees. Simultaneous three-axis movement is required to simultaneously perform C-axis movement and X-axis movement and Y-axis movement with respect to the end mill 71. In the case of such processing, the speeds of the respective axes in the A portion and the B portion which are the blade tip portions greatly vary.

  In this simulation, when the feedforward control according to the present invention is introduced into each drive control system of the X axis and the Y axis, and when the circular interpolation motion is performed on the X axis and the Y axis, the radius reduction amount becomes zero. Comparison was made with the conventional feedforward control adjusted as described above. The servo gain was adjusted by a partial model matching method as in the case of the XY drive mechanism 40 shown in FIG.

  FIG. 12 is a view showing the shape of the blade tip as a result of blade shape processing by simulation. As is apparent from FIG. 12, in the conventional feedforward control adjusted so that the radius reduction amount becomes zero, a dent caused by cutting deeper than the target value occurs at the blade tip where the speed change of each axis is large. Therefore, it is expected that the processing accuracy will be greatly deteriorated even in actual processing. On the other hand, when the feedforward control of the present invention is introduced, the target value and the locus of the tool tip coincide with each other. This is because, in the conventional feedforward control, even if it is optimally adjusted for one motion, another motion cannot follow and an error may occur. This also shows that the position command can be followed.

  As is apparent from the above description, according to the present invention, a position control device capable of following a position command having a different motion state is provided.

In each of the above embodiments, the functions of the position control means 21, the speed control means 22, the converter gain multiplication means 23, the adjustment gain multiplication means 24, and the feedforward control means 30 shown in FIG. Some or all of them can be configured as independent computing units.
In each of the above embodiments, the batterworth filter is used as the filter of the feedforward control means 30, but the same effect as described above can be obtained even if a low-pass filter other than this is used.

It is a perspective view which shows schematic structure of the feed drive mechanism as a control object to which this invention is applied. It is a dynamic model expressing the feed drive mechanism shown in FIG. It is a block diagram which shows the structure of one Embodiment of the position control apparatus which concerns on this invention. It is a block diagram which shows the detailed structure of the feedforward control means which comprises the position control apparatus shown in FIG. It is the flowchart which showed an example of the design procedure of the feedforward control means shown in FIG. It is the flowchart which showed an example of the process sequence at the time of giving a personal computer the function of the feedforward control means shown in FIG. It is a perspective view which shows schematic structure of the XY drive mechanism to which the position control apparatus based on this invention is applied as 1st Example. FIG. 8 is a characteristic diagram showing a ramp response of the position control device according to the present invention applied to the XY drive mechanism shown in FIG. 7 together with a case where feedforward control is not performed. The trajectory error when the circular interpolation motion is performed by the position control device according to the present invention applied to the XY drive mechanism shown in FIG. 7 is shown together with the case where the feedforward control is not performed and the case where the conventional feedforward controller is used. FIG. It is a perspective view which shows schematic structure of the 5-axis control machining center which applies this invention as 2nd Example and performs blade shape processing. The relationship between the shape of the tip of the blade and the shaft speed of the rotating shaft was simulated assuming that the blade shape is machined by placing the end mill perpendicular to the blade surface using the 5-axis control machining center shown in FIG. FIG. The figure which showed the shape of the wing tip part which simulated airfoil processing performed by putting an end mill perpendicularly to a wing surface using the 5-axis control machining center shown in Drawing 10, and the case by the conventional feedforward control It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Feed drive mechanism 14 Servo motor 16 Ball screw 17 Nut 18 Work table 21 Position control means 22 Speed control means 30 Feed forward control means 31 Differentiation means 32 Low-pass filter means 33 Feed forward compensation means 40 XY drive mechanism 41 XY table 42 X Axis servo amplifier 43 Y-axis servo amplifier 44 Linear encoder 50 Personal computer (PC)
60 5-axis control machining center 63 X-axis drive mechanism 64 Z-axis drive mechanism 65 Y-axis drive mechanism 66 AC-axis drive mechanism

Claims (3)

Position control means for multiplying the deviation between the position command of the control target to be torque driven and the detection signal of the actual position by a proportional gain and outputting it as the speed command of the control target; the speed command and the actual speed of the control target A speed control unit that outputs a sum of a value obtained by multiplying the deviation from the detection signal by a proportional gain and a value obtained by performing an integral operation, and generates a torque command for the control target based on the output of the speed control unit And output a speed feedback control system for torque driving the controlled object in accordance with the torque command, and a speed command compensation amount for inputting the position command and compensating for a delay of the speed feedback control system. In a position control device comprising feedforward control means for adding to the speed control means as a compensation for the speed command,
The feedforward control means includes
Differentiating means for differentiating and outputting the position command;
Low-pass filter means having a cut-off frequency substantially coinciding with the cut-off frequency of the speed feedback control system, inputting the output of the differentiating means and outputting only a low-frequency component;
A feedforward gain obtained by multiplying the output of the low-pass filter means by the feedforward gain, using the reciprocal of the transfer function of the speed feedback control system when regarded as a second-order lag system of the speed feedback control system as a feedforward gain. Forward compensation means,
A position control device comprising the position control device. The cutoff frequency of the speed feedback control system is ω _n , the proportional gain of the speed control means is K _vp , the converter gain for converting the signal output from the speed control means to a predetermined electrical signal is DA, and the predetermined The speed feedback control system is expressed by the following equation, where T _rg is a torque command adjustment gain that converts the electrical signal of the motor into a torque command, and J is the total moment of inertia of the controlled object to be torque driven.

Where the coefficient related to the motion conversion of the controlled object is M, the Laplace operator is s, and the feedforward gain is K _ff (s), the feedforward compensation means

The position control device according to claim 1, wherein the relationship is satisfied. The feedforward control means is characterized in that a third-order lowpass filter having a cutoff frequency ω _n is constituted by the differentiating means, the lowpass filter means, and the feedforward compensation means. The position control device according to claim 1 or 2.

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