JPH0382385A - Servo motor controller - Google Patents

Abstract

PURPOSE:To improve frequency response characteristic by correcting a current command by a deviation between an acceleration signal and an estimate acceleration as a model criterion of a control system in a speed controller for a servo motor, providing a limiter and limiting the current of the motor. CONSTITUTION:In a speed control loop having the sum of a value obtained by integrating a deviation signal between a speed command V(S) and a motor speed W(S) by an integration term K1S and a value obtained by feeding back the speed W(S) through a proportional term K2 as a torque command T(S), a criterion model alpha(KT/JM), a differentiating operator S, a correction gain KA are provided, and a limiter for limiting a current to a predetermined value or less is further provided. That is, the acceleration of the motor is fed back by the operator S, the acceleration is estimated with a current command as a criterion, compared with an acceleration signal, and the command T(S) is corrected. Thus, the frequency response of a control system is improved. An inverter and a motor are protected against an overcurrent by the limiter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a servo motor control device with improved characteristics such as frequency response characteristics.

The speed control system of a conventional servo motor can be shown as a block diagram in FIG. 4, if disturbances are ignored.

In the figure, K is an integral gain, 2 is a proportional gain, 2 is a torque constant, Jw is a motor rotor inertia, and β is a constant representing the magnitude of load inertia. This speed control system consists of the sum of the deviation signal between the speed command V (s) and the motor speed W (s), integrated by the integral term Kl/S, and the motor speed W (s) fed back through the proportional term 2. In addition, in a synchronous motor, the magnetic flux distribution and current of the motor are related to the torque, so current loop control is performed on the torque command T (s) to control the motor. is driving.

Problems to be Solved by the Invention In such a speed control system, there is a time delay in response due to /S in the integral term, and the control system may oscillate and become unstable, or vibration may occur when the motor is stopped. There was a problem.

The present invention aims to solve the problems of the prior art, and also provides a servo motor control device that protects an inverter that drives and controls the motor and the motor itself.

Means for Solving the Problems In order to achieve the above object, the servo motor control device of the present invention is configured as follows. That is, means for differentiating the speed of the servo motor to form an acceleration signal, means for estimating acceleration as a control system model standard using the current command output from the speed control loop, and the acceleration signal and the estimated acceleration. and a limiter for controlling the current flowing through the servo motor to a predetermined value or less with respect to the corrected current command. The above issues were resolved.

Effect: By having the above configuration, according to the present invention, the stability of the servo motor control system can be improved, and the influence of load fluctuations and disturbances can be reduced. In addition, since feedback control of acceleration is performed, even if the servo motor suddenly stops for some reason and the acceleration suddenly increases, the current will be limited by the limiter, so the inverter that controls the motor current and the motor itself will be This prevents the current from flowing, protecting the inverter and motor.

EXAMPLES Hereinafter, examples of the present invention will be explained with reference to the drawings. Since the present invention uses model-norm adaptive control, the principle of this control will be explained first. FIG. 3 is a block diagram showing an example of a parallel model reference control system. As shown in this figure, the reference model is placed in parallel with the controlled object, and the output of the controlled object ■. a7 and the output i of the normative model
. A correction signal C(e) is created by the difference e of a7, and this is converted to ■. .

It was designed to be added to. Such model-based adaptive control is likely to have the advantage of quick response and adaptive control of the control system.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, explanations are omitted for the same symbols as in Fig. 4, but the reference model α (KT / J M
), a differential operator S, and a correction gain KA are provided, and a limiter is provided to limit the current flowing through the servo motor to a predetermined value or less. That is, by providing a differential operator S, the motor speed is differentiated to form an acceleration feedback system, the acceleration is estimated using the current command as a standard, and the current command is corrected by comparing it with the acceleration signal. In response to a current command, a limiter prevents a current exceeding a predetermined value from flowing to the motor.

Next, the transfer function W (s)/V (s) shown in FIG. 1 is determined.

(1) When correction gain KA=O (conventional example) (W (s
) /V (s) ) = (KTKl) / (JM (1+β) s'
+Kr K2 s+Kt Kl )...(1) ;= , knee 1 (K 1= (1+β.)Kt.

K2=(1+β0)K20 β: Constant β corresponding to actual inertia. : 1o:β to the constant corresponding to the inertia ratio of the load. = 20:β for the integral gain of the velocity loop when O. If it is the proportional gain of the velocity loop when = 0, then β - β. In Case of, (
1) The formula is (W (s) /V (s)) = (Kt Klo (1+β.))/(J, (1+
βo)S'+KT (1+βo) K2O3+KT
KIO(1+β.))= , Wn'/(S'+
2ζWnS+Wn') ... can be expressed as song (2). However, (Kr KIO) /JM =Wn2. (KT/
JM) Let K20=2ζWn.

(2) Correction gain KA≠0. When coefficient α=0 (W (
a) /V (S) ) = (KtKx)/[(JM(1+β) +KT K
A) S2+ KT K2 S +Kt Kt]
(3), and adding only acceleration feedback corresponds to a pseudo increase in the rotor inertia of the motor.

(3) When correction gain KAToo, coefficient α≠0 (when model standard control and acceleration feedback are added) (W (S)/V (S)) = KTK, (1+αKAKt/JM))/ (JM (
1+β)+KT KA) S2+KT K2 (
1+(αKAKT/JM)) S+ KT Kl (
1+ (αKAKT/JM)) Here, (to α?/JM
) = α′, then (W (s) /V (s) ) = (Kt K1(1+α′ KA) )/[(J
M (i + β) + Kt KA ) S' + (K
, K20(1+βo) (1+KA a') S
)+ (KTKIO(1+βo)(1+a' KA)
)] Next, KA is (Kt KA/J M(1+β))=
When the apparent rotor inertia is set to be P, that is, when the apparent rotor inertia is multiplied by (1+P), α' is KA
If α' = P, then α is p (JM (1+β)
/Ky)・α(Kt/JM) =p, α= 1
/(1+β), so the transfer function is (W (s) /V (s)) ” (KT Kl.(1+β.)(1000P)l/[J
M (1+β)(1+yen S2+KT K20(1+β.

) (1 + Yen S + Kt Klo (1 + βo) (1 + P)
]=(KT Kl.(1+β.))/[JM(1+β)
S2+Kt K20 (1+βo)S+Kr Klo
(1+β,)] −·−−−(4).

In other words, Equation (4) shows that the speed group is K for the command.
It shows the same behavior as A=O (conventional example), and at the same time, the inertia of the motor rotor apparently increases, indicating that the stability of the speed control system is increased.

FIG. 2 is a block diagram of a speed limiting system that takes into account the influence of disturbances. Before considering the influence of disturbances, let us consider the influence of changes in inertia on the transfer function.

(1) Transfer function H(s) −(W(s)/V(s))=(when motor inertia coefficient β is β(S))
Kt Klo (1+a' KA) (1+β.))/[
(JM(1+β(8)) +Kf KA) 82+K
T K20 (1+βo) (1+KA (X')
S+KT K,. (1+β.)(1+α'KA)](
5) (6H(s)/8β(S)) = (Kt Klo(1+α'KA) JMs2(1+β
o))/[(JM(1+β(s))+KT KA S2
+KT K20 (1+βo) (1+KAa')
S+Kt Klo(1+βo)(1+a' K
A )]'(6) Here, if KA=0, (?3Ho (s) /8β(S)) =-KTKIO(1+βo) Jv S2/ (JM
(1+β(s))S2+Kt K20 (1+βO)
'r KIO(1+β.))2・・・・・・(7
) Next, Gl (8) = (6H(s) /6β(s) ) / (6Ho
(s) /8β(S))・・・・・・(8) When calculating, KA = P・(1+βt) x (Ju/Ky), α=
When 1/(1+β,), KAα' = KA X (Kt/Jv) α=P(
1+βr) (JM/Kt)・(KT/JM)X
(1/ (1+β,)) = P, and 1+β(s)”=1+β, then Gl (s) = [(JM(1+β1) S2+KT K20(1+β
O) S+Kr Klo(1+β.))2 x (1+P)]/[(1+p)' (JM (1
+β+)'s2+Kt K20(1+β.) S+Kt
Klo(1+β,))2]=1/ (1,000P)
...It becomes song (9). this
In equation (9), the correction gain KA is determined so that the rotor inertia of the motor is multiplied by (1+P), and α is determined so that the cutoff frequency and diving coefficient of the speed control system are KA=0.
If it is set to be equal to
/(1+P) times.

(2) Transfer function when considering torque disturbance To(s) in Fig. 2 Now, torque command T (s) = (K, / S) V (s) ((
Kl / S) +2) W (s) Correction torque signal A (s) = KA ((CIKT/JM)T (8)
SW (S)) Motor speed W (s) = ! 1/ (S Ju (1+β))l
[To (s) + niA (T (s) +A (s)
) ], then the following formula holds true.

W (s) = [1/ (S JM (1+β))]
['ro (s) +Kt [T (S) +KA
((to α?/JM) T (s)-8W(s))]
] ・・・・・・(10) Next, (SJM(1+β) W (s) ) =To (S) +KT (1+KAα(Ki/J
v) ) 'r (s)S Kt W (s) KA =T, (s) +KT (to 1+' Aα(K,
/JM)) [(Kl /s) v (s) −((Kl
/S) +2) w (s) ]-3K, W (
8) KA ・・・・・・(11) S' JM (1+β)W(s) =STo (s) +Kt (1+KA a') (
Kl V (s) - (Kl + SK2) W (S)
) -82KT W (S) KA・・・・・・(1
2) [(J, (1+β) +KA KT ) S' +KT
K2 (1+KA a')S+Kt Kl (1+K
A a')] w (s) = STo (s) +Kt
K1 (1+KA α'), V (8)...(
13) From this, equation (10) becomes W (s) =
[KTKto(1+βo) (1+KA α')V
(8)+STD (s)] / [(JM (1+
β) 10KA KT) S2+Kt K20(1+β
o ) (1+KA a') S+Kt Klo(1
+βo)(1+KAα′)] (14) Also, considering how the motor speed W(s) changes due to a change in the disturbance To(s), (6w (s)/6To (s)) = 8/ [(JM (1+β)+KAKa) S20Kt
K20 (1+βo) (1+KA a')
S+Kt K,o (1+βo) (1+KA a'
) ] (t5). Here, the motor speed when KA=0 is Wo(
s), then Wo (s) ” (KTKIO(1+βo) V (s) + S
To (s) )/(JM(1+β) S2+Kt
K20 (1+βo)S+Ky Kl. (1+β.)
......(16), so (?3Wo (s) /8To (s) )=To (
s) / (9(1+β)S2+KT K20 (1+
βo ) S+Kt K,o (1+β.))...
...(17) Therefore, G7I)(s) = (6W (s) /6To (s) )/(6WO (S)/PJTD (S)) = (JM(1+β)S2+KT K20 (1+β)
S+Kt Klo (1+βO))/[(JM (1
+β)+KA KT) S2+Kt K2O(1+βo
) (1+KA a') S+Kr Klo (1
+β. )(1+KAα')1...(18) holds true.

Next, KA=P (1+β) (J, /to, ), α=1
/ (1+β), then G7゜00 = UM (1+β) S2+KT K20 (1+β
)S+Kr Klo (1+β,))/(1+yen (J
M(1+β) 82+Kt K20(1+βo) S
+KT KIO(1+β.))=1/(1,000P)
...(19).
In equation (19), the correction gain KA is determined so that the rotor inertia of the motor is multiplied by (1+P), and α is set so that the cutoff frequency and diving coefficient of the speed control system are KA=0.
It is shown that if it is set to be equal to the case of , the influence of the disturbance torque fluctuation on the motor speed W(8) is reduced to 1/(1+P).

As described above, in the present invention, disturbance suppression performance is improved by performing acceleration feedback control instead of current feedback control.

On the other hand, when the servo motor suddenly stops rotating for some reason, the acceleration changes significantly. In particular, Figures 1 and 2
In the figure, the acceleration feedback signal obtained by differentiating the motor speed W(s) with the differential operator S becomes a large value due to the sudden stop of the motor, but the reference model α (K
The estimated acceleration signal output from t/JM) is
Due to delays in position loops, speed loops, etc., the value does not become large at the same time as the motor stops rotating. As a result, the corrected current command becomes a large value, and a large current command is output to the inverter that controls the current flowing to the servo motor, which may damage the inverter and the servo motor itself. Therefore, the present invention, as shown in FIGS. 1 and 2,
By passing the corrected current command through the limiter and limiting the current to a predetermined value or less, the inverter and servo motor are protected by preventing an excessive current command from being input to the inverter.

In conventional current loop control, a limiter is provided for the torque command value T(S) (current command value) output from the normal speed loop, but in this case, the current feedback signal cannot exceed the command value. However, in the case of acceleration feedback control, since the acceleration feedback signal changes significantly, it is necessary to set a limit on the current command (torque command) output from the speed loop. Therefore, a limiter is provided in the acceleration feedback loop to prevent an excessive current command from being input to the inverter.

As described in detail, the present invention provides a servo motor speed control system with a loop that differentiates the motor speed to form an acceleration signal, and uses a current command to specify the acceleration as a model standard. This estimated value is compared with the acceleration signal, the current command is corrected, and the corrected current command is limited by a limiter to prevent an excessive current command from being input to the inverter, increasing the frequency response. In addition, the influence of disturbances and load fluctuations can be reduced and stable control can be performed, and an excessive current command is not input to the inverter, thereby preventing damage to the inverter or servo motor itself.

[Brief explanation of drawings]

FIGS. 1 and 2 are block diagrams of the present invention, FIG. 3 is a block diagram illustrating model-based control, and FIG. 4 is a block diagram of a conventional example. S...differential operator, 1/S...integral operator. K1...integral gain, 2...proportional gain, KT・
... Torque constant, JM ... Motor inertia, KA
...Correction gain.

Claims (1)

[Claims] means for differentiating the speed of the servo motor to form an acceleration signal; means for estimating acceleration as a control system model standard using a current command output from the speed control loop; means for determining the deviation by comparison; means for correcting the current command using the deviation signal;
A servo motor control device comprising: a limiter for controlling a current flowing through the servo motor to a predetermined value or less in response to a corrected current command.