JP2003047269A - Servo controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo controller wherein the occurrence of instability due to application of a machine position detector is suppressed and positioning operation is implemented with accuracy at high speed. SOLUTION: A servo system is of full-closed loop wherein a machine 3 driven by a motor 1 is provided with a position sensor 4, and a machine rotational position θL outputted therefrom is inputted to a subtractor 5 and used as a feedback signal. The servo system is provided with a displacement differentiator 10. A torque current correction signal ΔIq* is calculated both from a motor rotational position θM detected by a position sensor 2 and the machine rotational position θL, and is fed back through a subtractor 11 so that the production of mechanical vibration is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo controller for position control, and more particularly to a servo controller suitable for a system using a connecting shaft to drive a load.

[0002]

2. Description of the Related Art For position control of an electric motor in a servo controller, a semi-closed circuit is used in which a detected value of a position detector directly connected to the shaft of the electric motor (hereinafter referred to as an electric motor position detector) is used as a feedback signal for control calculation.・ The loop method is generally used.

However, this method has an advantage that stable control can be easily obtained, but it depends on the accuracy and thermal expansion of the driving force transmission system (for example, a speed reducer) connecting the electric motor and the machine (load). There was a problem that errors and the like would appear as positioning errors as they were.

Therefore, when a precision machine tool having a high machining accuracy is required, especially when positioning accuracy is required, for example, a linear scale or the like is attached to the final position control target of the machine such as the workpiece mount. A full closed loop system in which a position detector (hereinafter referred to as a mechanical position detector) is directly attached and the detected value is used as a feedback signal has been conventionally used.

[0005] Here, as a technique related to this kind of technique, for example, the disclosures in the following publications can be cited. JP-A-09-182478, JP-A-09-258830, JP-A-10-148184, JP-A-11-324911

The above-mentioned prior art has the following problems. In other words, the driving force transmission system has rigidity, and therefore it is unavoidable that vibrations occur.However, when vibrations occur here, the vibrations also occur in the detection values from the final position control target part of the machine. As a result, the position control system oscillates and becomes unstable in the related art.

Therefore, in the prior art, it is necessary to reduce the position control gain before use, which results in a problem that it is difficult to realize a positioning operation at high speed. An object of the present invention is to provide a servo control device that suppresses the occurrence of an unstable state due to the application of a mechanical position detector, and that can perform highly accurate and high speed positioning operation.

[0007]

The above-mentioned object is to provide a motor connected to a machine, a power converter for driving the motor, and a speed command value in accordance with a deviation of a position detection value of the machine from a position command value. A position controller to obtain, a speed controller to obtain a torque current command value according to the deviation of the detected speed value of the electric motor with respect to the speed command value, and a current to control the output current of the power converter according to the torque current command value. In a servo controller provided with a controller, a position deviation differentiating means for calculating a torque current correction value according to a deviation between the position detection value of the electric motor and the position detection value of the machine is provided, and the torque current is corrected by the torque current correction value. It is achieved by modifying the command value.

Similarly, the above object is to provide an electric motor connected to the machine, an electric power converter for driving the electric motor, and a position controller for obtaining a speed command value according to a deviation of a position detected value of the electric motor from a position command value. A speed controller that obtains a torque current command value according to a deviation of a detected speed value of the electric motor with respect to the speed command value; and a current controller that controls an output current of the power converter according to the torque current command value. The servo control device is provided with position deviation differentiating means for calculating a torque current correction value according to a deviation between the detected position value of the electric motor and the detected position value of the machine, and corrects the torque current command value by the torque current correction value. Even if it is done, it will be achieved.

At this time, the position deviation differentiating means obtains the torque current correction value by multiplying the differential value of the deviation between the detected position value of the electric motor and the detected position value of the machine by a constant representing a differential gain. You may

Therefore, the feature of the present invention is to correct the torque current command value by using the deviation between the detected value of the position detector directly attached to the electric motor and the detected value of the position detector directly attached to the machine. Therefore, it can be said that the position control system is highly stabilized.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The servo control device according to the present invention will be described in detail below with reference to the embodiments shown in the drawings.
FIG. 1 is an embodiment of the present invention. In the figure, reference numeral 1 is an electric motor, which serves as a servomotor for driving a machine serving as a load. An electric motor position detector 2 is attached to the shaft of the electric motor 1 and serves to detect the motor rotation position θ _M. Reference numeral 3 denotes a machine to be servo-controlled, which is, for example, a machine tool connected to the electric motor 1 via a driving force transmission system such as a ball screw.

A machine position detector 4 is an electric motor 1 of the machine 3.
It is attached to the final position control target part by
Functions to detect the machine rotation position θ _L. At this time, in the case of the machine tool described above, the final position control target is, for example, a workpiece mount (XY table),
Therefore, in this case, the position detector 4 is a linear encoder type.

Numeral 5 is a subtractor, which serves to compare the position command θ ^* given from the outside with the mechanical rotation position θ _L and output the deviation between them.

A position controller 6 inputs the deviation between the position command θ ^* output from the subtracter 5 and the mechanical rotation position θ _L and outputs a speed command N ^* . Reference numeral 7 denotes a speed calculator, which operates to calculate the rotation speed N of the electric motor 1 from the electric motor rotation position θ _M. 8 is also a subtractor, and the speed command N ^* and the rotation speed N
And outputs these deviations.

Reference numeral 9 denotes a speed controller, which inputs a deviation between the speed command N ^* and the rotation speed N from a subtractor 8 and outputs a torque current command Iq ^*.
To output. Reference numeral 10 denotes a position deviation differentiator, which has a function of differentiating the deviation between the electric motor rotation position θ _M and the machine rotation position θ _L to calculate a torque current correction signal ΔIq ^* .

Reference numeral 11 is also a subtractor, and functions to output a new torque current command Iq ^* 'by comparing the torque current command Iq ^* with the torque current correction signal ΔIq ^* . A current detector 12 serves to detect the current value of the electric motor 1, that is, the torque current value Iq. Reference numeral 13 is also a subtracter, which functions to output the deviation between the new torque current command Iq ^* 'and the new torque current value Iq.

Then, the output of the subtractor 13 is input to the current controller 14, where the new torque current command Iq ^{* is} supplied ^.
′ And the voltage command V ^* corresponding to the deviation of the torque current value Iq are generated and supplied to the power converter 15. As a result, the electric motor 1 is rotated according to the position command θ ^* given from the outside. Thus, the positioning of the final position control target portion of the machine 3 can be obtained.

Next, the operation of this embodiment will be described. In this embodiment, as is apparent from the configuration of FIG. 1, the mechanical rotational position θ _L output from the mechanical position detector 4 is shown.
It constitutes a full-closed-loop type servo device using a feedback signal as a feedback signal. Therefore, when the driving force transmission system (torque transmission mechanism) between the electric motor 1 and the machine 3 is regarded as a spring system, The block diagram of is as shown in FIG.

In this block diagram, τ _M is the electric motor 1
Generated torque, J _M is the inertia of the motor 1, C _F
Is the viscosity constant, K _F is the spring constant, J _L is the inertia of the driven portion of the machine 3, and the motor rotation position θ _M and the machine rotation position θ _L are as described above.

Then, the resonance frequency f peculiar to this system is
_{The a} [Hz] and anti-resonance frequency f _z [Hz] can be expressed by the following equations (1) and (2).

[0021]

[Equation 1]

[Equation 2] Next, FIG. 3 shows an operation example in the case of using the full closed loop method in which the mechanical rotation position θ _L is used as a feedback signal. Here, in the operation example of FIG. 3, in order to see the effect of the position deviation differentiator 10 in the configuration which is the feature of the present invention, that is, the embodiment of FIG. 1, the differential gain Kd (described later) to be set is Especially, the characteristics when the positioning operation is performed by setting it to 0. In this case, the resonance frequency f _a = 45 [Hz] and the anti-resonance frequency f _z = 35 [Hz]. It can be seen that the position θ _L is unstable due to vibration (vibration frequency 35 [Hz]).

Therefore, in order to analyze the vibration phenomenon in this case, the closed loop transfer function θ _L / θ ^*. (S) from the position command θ ^* to the mechanical rotation position θ _{L is} calculated, and the following equation (3) is obtained. Get on the street. In addition, s is a Laplace operator.

[0023]

[Equation 3] Next, the closed loop transfer function θ _L / θ ^* expressed by equation (3)
・ The closed loop frequency characteristic (gain / phase characteristic) by (s) is as shown in Fig. 4. It is seen that the gain is obtained when the phase characteristic becomes -180 degrees near the anti-resonance frequency 35 [Hz]. Since the characteristic is 0 [dB] (= 1) or more and there is no phase margin (appropriate value: 40 to 60 degrees), there is concern that unstable vibration may occur near the anti-resonance frequency 35 [Hz]. It can be seen that this corresponds well with the characteristics of FIG.

However, in the case of the embodiment shown in FIG. 1, the above unstable vibration can be suppressed by setting the differential gain Kd of the position deviation differentiator 10 to a predetermined value. Therefore, this point will be described below.

First, the position deviation differentiator 10 will be described. It has a structure as shown in FIG.
Motor rotation position θ _M and machine rotation position θ input here
_L is first supplied to the subtractor 10a, and these deviations (θ _M
−θ _L ) is taken. Then, this deviation is input to the differentiator 10b, is differentiated here, and is multiplied by the constant Kd (differential gain described above) to obtain the torque current correction signal Δ.
Iq ^* is output.

Next, as a result, suppression of unstable vibration obtained by the embodiment of FIG. 1 will be described. First, the differential gain Kd of the position deviation differentiator 10 is set to a predetermined value, and then the closed loop transfer function θ _L / θ ^* · (s) from the position command θ ^* to the mechanical rotation position θ _L is obtained. It becomes as shown in the following equation (4). In this formula (4), n is added to each term of the denominator and the numerator to distinguish it from the above formula (3) (for example, al ₅ → aln ₅ , bl ₅ → bln ₅ ).

[0027]

[Equation 4] Therefore, comparing this equation (4) with the above equation (3),
By setting the differential gain Kd of a predetermined value in the position deviation differentiator 10, only the term of al _{4 in} the denominator of the expression (3) changes, and the term aln ₄ of the denominator of the expression (4) changes It can be seen that a part X surrounded by a square frame is added.

Here, the part X = added by setting a predetermined value as the differential gain Kd
Looking at {J _L K _d / K _F (J _M + J _L )}, this is
As is clear from the equation (4), the value C _F relating to the viscous friction coefficient
It can be seen that / K _F is increased equivalently and the damping ratio for the vibration of the mechanical system is changed in the direction of decreasing the vibration.

Therefore, the transfer function θ _L / θ ^{* of} this equation (4)
The closed loop frequency characteristic (gain / phase characteristic) due to (s) is as shown in FIG. 6, and the differential gain is 0 (Kd
= 0), the anti-resonance frequency 35

Gain characteristics near 0 Hz are 0

[DB] (= 1) or less, because it is also improved phase characteristic, it can be seen that the transfer function ^{_{θ L / θ * · (s}} ) is in the sufficiently stable.

FIG. 7 shows an operation example when the positioning operation is performed in this state. As shown in the figure, in this case, the vibration disappears from the rotational position characteristic θL of the machine, and stable positioning operation is obtained. Therefore, it can be seen that the effect of suppressing the unstable vibration by providing the position deviation differentiator 10 is great.

Next, another embodiment of the position deviation differentiator will be described with reference to FIG. Also in the case of the position deviation differentiator 10A shown in FIG. 8, the electric motor rotational position θ _M and the mechanical rotational position θ _L input to the position deviation differentiator 10 A are first supplied to the subtractor 10 a and these deviations (θ _M −θ _L ) Is taken. Then, this deviation is input to the differentiator 10c, and after being differentiated here, the constant Kd ₁ and the constant Kd ₂ are multiplied,
The torque current correction signal ΔIq ^* is output. Even if the position deviation differentiator 10A shown in FIG. 8 is used, the same vibration suppression as that of the position deviation differentiator 10 shown in FIG. 5 can be obtained.

By the way, the embodiment described with reference to FIG. 1 relates to a so-called full closed loop type servo device in which the mechanical rotation position θ _L output from the mechanical position detector 4 is used as a feedback signal. The present invention can also be implemented as a semi-closed loop type servo device under the same configuration as the embodiment of FIG.

FIG. 9 shows an embodiment of the present invention by the semi-closed loop system. The difference between the embodiment of FIG. 9 and the embodiment of FIG. The only signal is the electric motor rotational position θ _M output from the electric motor position detector 2, and other configurations include the point that the mechanical position detector 4 and the position deviation differentiator 10 are provided. 1 is the same as that of the embodiment shown in FIG.

[0034]

According to the present invention, there is no possibility that mechanical vibration will occur even when applied to the driving of a machine having a low mechanical rigidity, and therefore, the advantages of applying the mechanical position detector can be fully utilized. A highly accurate and high speed positioning operation by the servo motor can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a servo control device according to the present invention.

FIG. 2 is a block diagram of a driving force transmission system according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing an example of a positioning operation operation when the differential gain is set to 0 in the embodiment of the present invention.

FIG. 4 is a closed loop frequency characteristic diagram from a position command to a machine position when the differential gain is set to 0 in the embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a position deviation differentiator according to an embodiment of the present invention.

FIG. 6 is a closed loop frequency characteristic diagram from a position command to a machine position when a differential gain is set to a predetermined value in one embodiment of the present invention.

FIG. 7 is a closed loop frequency characteristic diagram from a position command to a machine position when a differential gain is set to a predetermined value in one embodiment of the present invention.

FIG. 8 is a block diagram showing another example of the position deviation differentiator according to the embodiment of the present invention.

FIG. 9 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 Electric motor (servo motor) 2 Motor position detector (motor position detector) 3 machines 4 Machine position detector (machine position detector) 5, 8, 11, 13 Subtractor 6 Position controller 7 Speed calculator 9 Speed controller 10 Position deviation differentiator 12 Current detector 14 Current controller 15 Power converter

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H303 AA01 AA06 AA10 CC03 CC04                       DD01 GG20 HH02 HH07 JJ02                       KK04 KK18 KK19 KK33 LL03                 5H550 AA18 BB05 DD01 GG01 GG02                       GG03 GG05 HB08 JJ23 JJ25                       LL07 LL22 LL35 LL36 PP10                 5H576 AA17 BB04 DD02 DD10 EE01                       GG01 GG02 GG04 GG10 HB01                       JJ23 JJ25 LL07 LL22 LL41                       LL42 PP01

Claims (3)

[Claims] 1. A motor connected to a machine, a power converter for driving the motor, a position controller for obtaining a speed command value according to a deviation of a position detection value of the machine from a position command value, and the speed. A servo controller including a speed controller that obtains a torque current command value according to a deviation of a detected speed value of the electric motor from a command value, and a current controller that controls an output current of the power converter according to the torque current command value. In, a position deviation differentiating means for calculating a torque current correction value according to a deviation between the position detection value of the electric motor and the position detection value of the machine is provided, and the torque current command value is corrected by the torque current correction value. A servo control device characterized by being configured. 2. A motor connected to a machine, a power converter for driving the motor, a position controller for obtaining a speed command value according to a deviation of a position detection value of the motor from a position command value, and the speed. A speed controller that obtains a torque current command value according to a deviation of the speed detection value of the electric motor with respect to the command value,
In a servo control device including a current controller that controls an output current of the power converter according to the torque current command value, a torque current correction value is set according to a deviation between a position detection value of the electric motor and a position detection value of the machine. A servo control device characterized in that a position deviation differentiating means for calculating is provided and the torque current command value is corrected by a torque current correction value. 3. The invention according to claim 1 or 2, wherein the position deviation differentiating means multiplies the differential value of the deviation between the detected position value of the electric motor and the detected position value of the machine by a constant representing a differential gain. Then, the servo control device is configured to obtain the torque current correction value.