JP3381880B2 - Servo control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo system controller used for servo of machine tools, industrial robots, FA and the like.

[0002]

2. Description of the Related Art In a conventional servo system, a speed control system is disclosed in, for example, Japanese Patent Laid-Open No. 62-77605 or Technical Report "Yasukawa Electric".
Volume 55 No. 3 1991 p. 174 of 3.3
PI or IP control is used as described in (2).

[0003]

However, the conventional PI
Alternatively, in the IP speed control system, when the load has a vibration characteristic, only a low gain that does not make the vibration characteristic unstable can be set, and the response of the control system becomes slow. There was a point. FIG. 11 is a block diagram of the servo system. FIG. 10 shows a dynamic characteristic model of a controlled object in which the vibration characteristic is taken into consideration and its pole-zero arrangement on the s-plane for this servo system. Where ω ₁ = (K · (1 / J _M +1
/ J _L )) ^1/2 ω ₂ = ((K / J _L )) ^1/2 , which are the resonance and anti-resonance angular frequencies, respectively. R
e is a real axis and Im is an imaginary axis. 13A shows a block diagram of the PI speed control system, and FIG. 13B shows a block diagram of the IP speed control system. FIG. 11C shows the pole-zero arrangement of the open loop transfer function. Here, G _V (s) is the transfer function of the controlled object shown in FIG. The pole-zero arrangement of the controlled object is the same for the PI and IP speed control systems. FIG. 14 shows a root locus when the gain Kv is increased from zero in the PI and IP speed control system. 14
(A) shows that when ω ₂ is sufficiently larger than 1 / T _i , both the rigid system, which is the origin pole, and the vibration characteristics have a fast response and are sufficiently stabilized. However, if a smaller integration time is set in order to make the response of the rigid system faster, as shown in FIG. 14 (b), the vibration characteristics are sufficiently stabilized, but the poles of the rigid system have zero points of antiresonance. The rigid system has a slow response and a vibration-like response with small damping. This is an unfavorable characteristic in a servo system. Therefore, an object of the present invention is to provide a control device that can set a high gain and is excellent in responsiveness and damping.

[0004]

In order to solve the above problems, the present invention uses one-degree-of-freedom vibration characteristics as a load, and performs one-cycle transmission in a servo-system controller for controlling the motor speed by PI or IP. Phase lead filter to function Glead
Insert (s) = (T ₁ s + 1) / (T ₂ s + 1) (where T ₁ > T ₂ , T ₁ and T ₂ are the time constants of the phase advance filter, and s is the Laplace operator). , Ω ₂ is the antiresonance angular frequency of the vibration characteristic which is the zero point of the transfer function from the motor torque to the motor speed, and T _i is the integration time which is the reciprocal of the integral gain in the integral control of PI or IP control. The anti-resonance zero point s = jω ₂ and the PI or IP control zero point s = −1 / T _i , the phase lead filter zero point s = −1 / T ₁ and the pole s = −1 / T ₂ Angle φ ₁ = arctan (ω ₂ , T _i ), φ ₂ = arcta
n (ω ₂ , T ₁ ), φ ₃ = arctan (ω ₂ , T ₂ ).
Is set to satisfy the phase condition of φ ₁ + φ ₂ −φ ₃ ≈π / 2. Further, in a servo system control device that controls the motor speed by PI or IP by using a vibration characteristic of one degree of freedom as a load, a phase advance filter Glead (s) = (T ₁ s + 1) /
(T ₂ · s + 1) (where T ₁ > T ₂ , T ₁ and T ₂ are the time constants of the phase advance filter, s is the Laplace operator), and ω ₁ from the motor torque to the motor speed is inserted. When the resonance angular frequency of the vibration characteristic that is the pole of the transfer function and T _i are the integration time that is the reciprocal of the integral gain in the integral control of PI or IP control, the pole of the vibration characteristic s = j
ω ₁ and the zero point s = −1 / of PI or IP control
An angle φ ₁ ′ = arctan formed by T _i , the zero point s = −1 / T ₁ and the pole s = −1 / T ₂ of the phase advance filter.
(Ω ₁ , T _i ), φ ′ ₂ = arctan (ω ₁ ,
T ₁ ), φ ′ ₃ = arctan (ω ₁ , T ₂ ) is φ ′ ₁ +
It is characterized in that it is set so that the phase condition of φ ′ ₂ −φ ′ ₃ ≈π / 2 is satisfied. In addition, the speed command or the absolute value of the speed is compared with the limit speed that can be set. It is characterized by having done. In addition, the speed control system is
It is characterized in that position control is performed so that it is incorporated as a group. Regarding the absolute value of the deviation | e | of the position control system, a function f (| e |) is defined in advance, and a = f (| e |)
Then, the transfer function of the phase lead filter to be inserted into the open loop transfer function of the control system is (aT ₁ s + 1) / ((1-
a) T ₂ · s + 1). Further, the present invention is characterized in that a phase advance filter is inserted from a positioning start point to a positioning completion point, and a first-order lag filter or a second-order lag filter is inserted into the loop transfer function of the speed control system once the positioning is completed.

[0005]

1 and 2 are block diagrams of a speed control system in which a phase advance filter is inserted. FIG. 1A shows the case where the PI speed control system is inserted in the forward loop.
(B) is a case where it is inserted in the feedback loop in the PI speed control system. Further, FIG. 2 (a) shows the case of insertion in the forward loop in the IP speed control system, and FIG. 2 (b) shows the case of insertion in the feedback loop in the IP speed control system. In either case, the pole-zero arrangement and the root locus of the speed control system are the same. FIG. 3A is a pole-zero arrangement of the PI and IP speed control system in which a phase advance filter is inserted. When a phase advance filter is inserted and T ₂ <T ₁ and T ₂ <T _i , their root loci show the rigid system and vibration characteristics regardless of the setting of T _i , as shown in FIG. 3B. As compared with the case without the phase advance filter, the response is remarkably fast and the characteristic of damping property, that is, good stability can be set. For example, it is possible to make settings such as the square and x mark in FIG.

[0006]

EXAMPLES Specific examples of the present invention will be described below. The specific design conditions of the phase advance filter are presented. First, it is a condition that the poles of the rigid system are converged on the real axis without being directed to the antiresonance zero point. It is assumed that the integration time T _{i is} the time constants T ₁ and T _{2 of the} phase advance filter (T ₁ > T ₂ ). Two zeros s =
The angles between −1 / T _i , s = −1 / T ₁ and the pole s = −1 / T ₂ and the antiresonance zero s = jω ₂ are φ ₁ , respectively.
When φ ₂ and φ ₃ , φ ₁ = arctan (ω ₂ · T _i ) φ ₂ = arctan (ω ₂ · T ₁ ) φ ₃ = arctan (ω ₂ · T ₂ ), but (φ ₁ + φ _By designing to satisfy the condition that ( _2- φ ₃ ) is approximately π / 2 (phase condition 1), the rigid system always converges on the real axis, and a speed control system with fast response and good damping can be realized. FIG. 4 is a diagram showing the phase condition 1.
Next, the conditions for stabilizing the vibration characteristics most are presented. Two zeros s = -1 / T _i , s = -1 / T ₁ and pole s =-
When the angles formed by 1 / T ₂ and the vibration characteristic pole s = jω ₁ are φ ₁ ′, φ ₂ ′, and φ ₃ ′, φ ₁ ′ = arctan (ω ₁ · T _i ) φ ₂ ′ = arctan (ω ₁ · T ₁ ) φ ₃ '= arctan (ω ₁ · T ₂ ), but (φ ₁ ' + φ ₂ '-φ ₃ ') satisfies the condition (phase condition 2) that it is approximately π / 2. With such a design, the vibration characteristic becomes the most stable condition, and a speed control system with fast response and good damping can be realized. Figure 5 shows phase condition 2
FIG. In order to realize the servo system as shown in Fig. 1, first, the speed control system with the above-mentioned phase advance filter inserted is configured, and appropriate phase conditions, gains and parameters are set, and high response and high attenuation are set. The speed control system may be realized and a position feedback control loop may be added to this speed control system. In the digital servo system, the effect of position quantization is large, and it is necessary to make the parameters of the phase advance filter variable depending on the size of the deviation. FIG. 6 shows a block diagram of a position control system that realizes this. Here, the block 15 is a non-linear function of the absolute value of the position deviation, which inputs | e | and outputs the variable parameter a, and a = f (| e |). A block 16 is a phase advance filter whose characteristic is variable by a variable parameter a, and its transfer function is Glead (s) = (aT ₁ s + 1) / ((1-a)
・ T ₂ · s + 1). With such a variable parameter phase advance filter, it is possible to realize a servo system which is always highly responsive and highly stable even in a digital servo system, regardless of the magnitude of the position deviation. An implementation example of the phase advance filter will be described. FIG. 7 shows an example of an analog circuit using an operational amplifier, capacitance, and resistance. FIG. 8 shows an example of realization of a phase advance filter by digital calculation. u is an input, y is an output, and i is a sample time. 17 is a delay memory of 1 sample,
Reference numerals 18 and 19 are parameters that determine the characteristics of the filter. Ts is a sampling period. In the case of digital, it can be realized by a digital hard circuit or a software program. In the case of digital, a variable parameter phase advance filter can be easily realized by setting the parameters 18 and 19 to variable parameters. In the digital servo system, the stability condition at an extremely low speed including stop and the stability condition at a speed higher than this are different. At extremely low speeds, the influence of the quantization error is large, and the first-order lag filter may be more easily stabilized than the phase-lead filter. In such a case, as shown in FIG. 9, a determination circuit that compares the speed command or the absolute speed value with a settable speed limit, a changeover switch that operates in conjunction with the determination circuit, and a phase advance filter (T ₁ s + 1) / ( T ₂ s
+1) and a first-order lag filter 1 / (T _f s + 1) (T _f is a filter time constant) are provided, and if the speed is equal to or higher than the limit speed, the switch terminal 1 is connected to the phase lead filter, and if less than the limit speed, the switch terminal is connected. 2 is connected and inserted into the open loop transfer function of the first-order lag speed control system. A positioning determination circuit for determining the positioning state is provided, and as shown in FIG. 10, the switch terminal 1 is connected and the phase advance filter is connected from the start point of positioning to the end point of positioning, and the switch terminal 2 is connected once the positioning is completed. 1st-order lag filter 1 /
(T _f s + 1) or second-order lag filter 1 / (T _{f 1}
s + 1) (T _{f 2} s + 1) (T _{f 1} and T _{f 2} are filter time constants) are inserted into the open loop transfer function of the speed control system.

[0007]

As described above, according to the present invention, regarding the servo system having the vibration characteristic, by inserting the phase advance filter in the speed control system and setting the parameter to a specific condition, An extremely high response and highly stable speed and position servo system can be realized. Furthermore, since this method can be realized only by adding a simple phase advance filter,
It also has a high economic effect.

[Brief description of drawings]

FIG. 1 PI speed control system with a phase lead filter inserted

FIG. 2 is an IP speed control system in which a phase advance filter is inserted.

FIG. 3 PI and IP with a phase lead filter inserted
Pole-zero arrangement and root locus of speed control system

FIG. 4 Phase condition 1

FIG. 5: Phase condition 2

FIG. 6 is a block diagram of a position servo system in which a parameter of a phase advance filter is changed as a function of position deviation.

FIG. 7 is a diagram showing realization of a phase advance filter by an analog circuit.

FIG. 8 is a diagram showing realization of a phase advance filter by digital calculation.

FIG. 9 is a diagram for explaining filter switching before and after a limit speed.

FIG. 10 is a diagram illustrating filter switching before and after completion of phase determination.

FIG. 11 is a block diagram of a servo system.

FIG. 12 is a diagram showing a dynamic characteristic model of a controlled object.

FIG. 13 (a) PI speed control system (B) IP speed control system (C) Pole-zero arrangement of open-loop transfer function

FIG. 14: Root locus of PI and IP speed control system

[Explanation of symbols]

1 Control Target 2 Mechanism 3 Motor 4 Position and Speed Detector 5 Position Control Controller 6 Speed Control Controller 7 Power Amplifier 8 Speed Calculator 9 Position Command r 10 Position x 11 Speed v 12 Speed Command v _r 13 Current Command i _r 14 Current i 15 Non-linear function of position deviation 16 Variable parameter Phase advance filter 17 1-sample delay memory 18, 19 Phase advance filter parameters

Continuation of front page (51) Int.Cl. ⁷ identification code FI G05D 3/12 306 G05D 3/12 306S 13/62 13/62 Q (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 5 / 00 G05B 11/36 G05B 13/02 G05D 3/12 G05D 13/62

Claims (6)

(57) [Claims] 1. A servo system controller for controlling a motor speed by PI or IP by using a vibration characteristic of one degree of freedom as a load, and a phase lead filter Glead as a loop transfer function.
Insert (s) = (T ₁ s + 1) / (T ₂ s + 1) (where T ₁ > T ₂ , T ₁ and T ₂ are the time constants of the phase advance filter, and s is the Laplace operator). , mode of ω ₂
Vibration, which is the zero of the transfer function from torque to motor speed.
The anti-resonance angular frequency of dynamic characteristics, T _{i, is controlled} by PI or IP.
Integration time, which is the reciprocal of the integration gain in the integral control
And the antiresonance zero s = jω ₂ and PI or
Zero point s = -1 / T _i of IP control , phase lead filter
Zeros s = -1 / T ₁ and the angle between the pole s = -1 / T ₂
φ ₁ = arctan (ω ₂ , T _i ), φ ₂ = arcta
n (ω ₂ , T ₁ ), φ ₃ = arctan (ω ₂ , T ₂ ).
Satisfies the phase condition of φ ₁ + φ ₂ −φ ₃ ≈π / 2
Servo control device characterized by being set to. 2. A motor having a one-degree-of-freedom vibration characteristic as a load.
System for servo system to control speed of PI or IP
, The phase advance filter Glea is added to the open loop transfer function.
d (s) = (T ₁ s + 1) / (T ₂ s + 1) (only
Then, T ₁ > T ₂ , T ₁ , T ₂ is the time constant of the phase lead filter.
The number, s inserts a Laplace operator), the omega ₁ Mo
Vibration, which is the pole of the transfer function from the data torque to the motor speed.
PI or IP control of resonance angular frequency T _i of dynamic characteristics
Integration time which is the reciprocal of the integration gain in the integration control of
, The vibration characteristic pole s = jω ₁ and PI or I
-P control zero s = -1 / T _i , phase lead filter zero
The angle φ formed by the point s = -1 / T ₁ and the pole s = -1 / T _{2
1 '= arctan (ω 1,} T i), φ' 2 = arcta
n (ω ₁ , T ₁ ), φ ′ ₃ = arctan (ω ₁ ,
The phase condition that T ₂ ) is φ ′ ₁ + φ ′ ₂ −φ ′ ₃ ≈π / 2
Servo system control characterized by being set to meet
Your device. 3. A speed command or absolute value of speed can be set.
If the speed exceeds the limit speed, the phase advance
Filter, first-order lag filter if less than limit speed
Is inserted in the open loop transfer function of the speed control system.
The control device for the servo system according to claim 1 or 2.
Place 4. A speed control system is assembled as a minor loop.
2. The position control is performed so as to be tightly inserted.
4. The servo system control device according to any one of 3 to 3. 5. The absolute value of the deviation of the position control system | e |
Then, the function f (| e |) is defined in advance, and a = f (|
e |), the position to be inserted into the open loop transfer function of the control system
The transfer function of the phase-lead filter is (aT ₁ · s + 1) /
((1-a) T ₂ · s + 1),
The servo system control device according to claim 4. 6. A positioning start point to a positioning completion point
Positioning of the phase advance filter has been completed until
After that, speed up the first-order lag filter or the second-order lag filter.
It is characterized in that it is inserted into the open loop transfer function of the control system.
The servo system control device according to claim 4.