JPH0778023A - Method and device for deciding state of control system - Google Patents

Abstract

PURPOSE:To reduce trial and error and to decide the stable state of the control system with high precision by making the decision on the basis of a signal determined on the basis of the transfer function, etc., of a controller and a controlled system and an amount of input signal power to the controlled system. CONSTITUTION:A control command signal is supplied to the controlled system 3 through a subtracter 1 and the controller 2, and the output signal of the controlled system 3 and the output signal of additive uncertainness 4 are added and fed back to the subtracter 1. A 1st signal power calculation part 6 calculates the power of the output signal from the controller 2 for this feedback control system. Further, a subtracter 8 performs subtraction between the output signals of a virtual controlled system 7 and an adder 5 which have the same transfer function with the controlled system 3 and inputs the result to a virtual block 9 having the same transfer function with a part including the controller 2 and controlled system 3. A 2nd signal power calculation part 10 calculates the power of the output signal from the virtual block 9 and a decision part 11 decides the large/small relation between the power values calculated by the power calculation parts 6 and 10 to decide whether the control system is stable or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for determining the state of a control system, and more specifically, an operation instruction signal is supplied to a controlled object via a controller.
The present invention relates to a method and an apparatus for determining whether or not a control system in which an output signal from a controlled object is fed back to a controller and which has an additive uncertainty in parallel with the controlled object is in a stable state.

[0002]

2. Description of the Related Art Conventionally, an operation instruction signal is supplied to a controlled object via a controller, and an output signal from the controlled object is fed back to the controller. If any failure occurs in the control system that has, or if there is a significant disturbance, etc., the control system becomes unstable and if left unattended,
It is known that it is necessary to stop the operation of the control system or readjust the gain of the controller as soon as possible because it may cause a great risk such as failure of the control system. There is.

Therefore, in the operating state of the control system,
It is required to determine whether or not the control system is in a stable state, and immediately notify that the control system is in an unstable state when the unstable state is detected. As a method for satisfying this requirement, conventionally, the deviation between the control target value and the actual control amount is detected, and the magnitude of the deviation and the predetermined threshold value is determined,
A method of notifying that the control system has become unstable on the condition that the deviation exceeds a predetermined threshold has been proposed and actually used. That is, it is possible to determine that the control system is in a stable state if the control target value and the actual control amount are not too far from each other, and it is possible to determine that the control system is in an unstable state if they are far from each other.

[0004]

In adopting the above method, it is necessary that the predetermined threshold value is properly set, but trial and error is necessary to set the appropriate threshold value. However, there is a disadvantage that the number of trials and errors generally increases significantly. That is, when the number of trials and errors is small and the threshold value is not set properly, it is determined that the control system is in the unstable state even though it is in the stable state, or the control system is in the unstable state. Nevertheless, it causes an inconvenience that the stable state is determined. The former inconvenience reduces the operating rate of the control system, and the latter inconvenience causes a failure of the control system, and therefore cannot be ignored at all.

Further, even if the predetermined threshold value is properly set, there is a disadvantage that the state determination based on the threshold value is conservative. Specifically, when the motor load becomes large, the control system is stable, but it is determined that the control system is unstable due to an increase in the deviation.
It is possible to exemplify that it is determined that the industrial robot is in an unstable state due to an increase in position deviation, even if impedance control is well performed when the hand of the industrial robot hits a wall. it can.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to greatly reduce trial and error and maintainability, and it is possible to accurately determine whether or not a stable state exists. An object of the present invention is to provide a method for determining the state of a control system and its apparatus.

[0007]

In order to achieve the above object, a method of determining the state of a control system according to claim 1 is a power determined by an input signal power to a controlled object and a controller and the controlled object. This is a method of obtaining a signal power determined based on a function, a transfer function of additive uncertainty and an input signal to a controlled object, and determining whether or not the control system is stable based on the magnitude of both signal powers.

According to a second aspect of the present invention, there is provided a control system state discrimination device, a first signal power calculating means for calculating the power of an input signal to a controlled object, a transfer function determined based on the controller and the controlled object, and an additive uncertainty. A second signal power calculating means for calculating the power of a signal determined based on the transfer function of 1 and the input signal to the controlled object, and a determining means for determining whether or not the control system is stable based on the magnitude of both signal powers. Contains.

[0009]

According to the method of determining the state of the control system of claim 1, the operation instruction signal is supplied to the controlled object via the controller, and the output signal from the controlled object is fed back to the controller. In determining whether a control system that has an additive uncertainty in parallel with the control target is in a stable state, the transfer function determined based on the power of the input signal to the control target and the controller and the control target. , The power of the signal determined based on the transfer function of additive uncertainty and the input signal to the controlled object is obtained, and it is determined whether the control system is stable or not based on the magnitude of both signal powers. If so, even in a control state in which erroneous determination may be performed, accurate state determination can be performed based on the magnitude relationship between both signal powers. Further, since the deviation in the initial state is large and the variable gain is provided, even in a control system that may possibly become unstable in actual use, accurate state determination can be performed.

According to the second aspect of the present invention, the operation instruction signal is supplied to the controlled object via the controller, and the output signal from the controlled object is fed back to the controller. In determining whether or not the control system having an additive uncertainty in parallel with the controlled object is in a stable state, the power of the input signal to the controlled object is calculated by the first signal power calculation means, and the controller is calculated. And the power of the signal determined based on the transfer function determined based on the controlled object, the transfer function of the additive uncertainty, and the input signal to the controlled object by the second signal power calculation means, and based on the magnitude of both signal powers. The determination means can determine whether the control system is stable. Therefore, according to the conventional method, it is possible to accurately determine the state based on the magnitude relationship between both signal powers even in the control state in which there is a possibility of making an erroneous determination. Further, since the deviation in the initial state is large and the variable gain is provided, even in a control system that may possibly become unstable in actual use, accurate state determination can be performed.

[0011]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 4 is a diagram schematically showing a control system having an additive uncertainty, in which the control target signal r is a subtracter 1 and a controller 2.
Is supplied to the controlled object 3 through, and the additive uncertainty 4 is connected in parallel with the controlled object 3. And controlled object 3
And the output signal from the additive uncertainty 4 are added by the adder 5 and output as the output signal y.
Further, the output signal y is fed back to the subtractor 1.

The input signal of the controller 2 is shown by e, the output signal from the controller 2 is shown by u, the gain of the controller 2 is shown by K, and the transfer function of the additive uncertainty 4 is shown by Δ. Also, G
_n is a transfer function of the model (nominal model) of the actual controlled object (G _n + Δ) obtained by the identification. FIG. 1 is a flow chart for explaining an embodiment of a state discrimination method applied to the control system of FIG.
Calculate the power power (u) of the output signal u from
In step SP2, the transfer function Φ determined based on the controller 2 and the controlled object 3 is calculated, and in step SP3, the calculated transfer function Φ, the transfer function Δ of the additive uncertainty 4 and the output signal u from the controller 2 are calculated. The power (z) of the power of the signal z determined based on Then, in step SP4, it is determined whether the power power (z) is smaller than the power power (u),
If the power power (z) is equal to or higher than the power power (u), the control system is notified in step SP5 that the control system is unstable. In this case, the control system is stopped if necessary. On the contrary, when it is determined in step SP4 that the power power (z) is smaller than the power power (u), the control system is stable.
The processing of step SP1 is performed again.

As is clear from the above description, the control system is passive (power consumption system, power (z) <power).
If (u)}, it is determined that the state is stable, and if not passive, it is determined that the state is unstable. Therefore, it is possible to remarkably improve the state discrimination accuracy as compared with the conventional method of simply comparing the deviation with a predetermined threshold value. The state determination method will be described in more detail.

It is known that if the transfer functions Φ and Δ are stable in the simplest control system shown in FIG. 2, the closed loop system Φ / (1 + ΦΔ) is stable when the equation 1 is satisfied. ing.

[0015]

[Equation 1]

FIG. 3 is a diagram showing a system in which the transfer function is ΦΔ. If the power (power) (x) of the signal x is calculated by Expression 2, ΦΔ is passive when Expression 3 is satisfied. However, z = ΦΔu.

[0017]

[Equation 2]

[0018]

[Equation 3]

From the above description, it can be seen that equation 4 and equation 1 are equivalent.

[0020]

[Equation 4]

Therefore, the transfer functions Φ and Δ are stable, and if the equation 4 is satisfied, the closed loop system Φ / (1 + ΦΔ) is stable. Further, in FIGS. 2 and 3, signals u and z are signals r
, The transfer functions Φ and Δ of FIGS. 2 and 3 are included.
Is stable, and for some angular frequency ω power {u
If (jω)}> power {z (jω)}, the closed loop system u (jω) = Φ / (1 + ΦΔ) r (jω) is bounded.

Next, let us consider a case where the above knowledge is applied to the control system of FIG. Since the control system of FIG. 5 can be obtained by modifying the control system of FIG. 4, K of the control systems of FIG.
_Let Φ be the transfer function of the part including G _n and Φ = K /
It becomes (1 + KG _n ). That is, Φ is stable if K stabilizes the closed loop for the nominal model G _n . Further, from the calculation of the denominator polynomial, u (jω) / r (j
ω) = Φ / (1 + ΦΔ) poles and y (jω) / r (jω)
= (G _n + Δ) Φ / (1 + ΦΔ) poles.

Therefore, when the transfer function Δ is 0, the closed loop is stable (the transfer function Φ is stable), the transfer function Δ is stable, and power {u
If (jω)}> power {z (jω)}, the closed loop system y (jω) = (G _n + Δ) Φ / (1 + ΦΔ) r
(Jω) is bounded. Here, the condition that the closed loop is stable when the transfer function Δ is 0 (the transfer function Φ is stable) and the transfer function Δ is stable is satisfied at the time of designing the control system. Therefore, in the state where the control system is actually operating, power {u (jω)}> power
By determining whether or not {z (jω)}, it is possible to determine whether or not the control system is in a stable state.

However, as a formula for calculating the power of the signal x, the forgetting factor γ (t) (where γ (t)
= Γ ^Tt , 0 <γ ≦ 1} is preferably used.

[0025]

[Equation 5]

[0026]

[Embodiment 2] FIG. 6 is a block diagram showing an embodiment of a control system state discriminating apparatus of the present invention, in which a control target signal r is supplied to a control target 3 through a subtracter 1 and a controller 2, 3 is connected in parallel with an additional uncertainty 4, and the output signal from the controlled object 3 and the output signal from the additional uncertainty 4 are added by the adder 5 and output as the output signal y, and the output signal y Is fed back to the subtractor 1, the first signal power calculator 6 calculates the power power (u) of the output signal u from the controller 2.
Is provided. Then, the output signal u from the controller 2
Is provided as an input, and a virtual controlled object 7 having the same transfer function as the controlled object 3 is provided, and the output signal y and the virtual controlled object 7 are provided.
Is provided with a subtractor 8 for obtaining the difference between the output signal from the subtracter 8 and the output signal from the subtractor 8.
The virtual block 9 having the same transfer function as the transfer function Φ of the portion including the control target 3 and the second signal power calculation unit 10 for calculating the power power (z) of the output signal z from the virtual block 9 is provided. It is provided. Further, the power powe calculated by the first signal power calculator 6
A discriminating unit 11 that discriminates the magnitude of r (u) and the power power (z) calculated by the second signal power calculating unit 10 and outputs a state discrimination signal corresponding to the discrimination result is provided.

The output signal from the virtual controlled object 7 in FIG. 6 is G
_Since it is _n u, the output signal from the subtractor 8 becomes y-G _n u. Here, since y = G _n u + Δu, the subtracter 8
The output signal from is Δu. Therefore, by passing through the virtual block 9, ΦΔu = z is obtained. As a result, the discriminating unit 11 keeps the power power (u), po
Wer (z) is used as an input to determine the magnitude of the two. When power (u)> power (z), a state determination signal indicating a stable state is output, and in other cases, an unstable state is output. Then, a state discrimination signal indicating that is output.

[0028]

[Embodiment 3] FIG. 7 is a block diagram showing another embodiment of the control system state discriminating apparatus of the present invention. The difference from the block diagram of FIG. 6 is that the virtual control target 7, the subtractor 8 and the virtual block are different. Instead of 9, the virtual block 12 having the control target signal r as an input and having the same transfer function as the transfer function Φ of the portion including the controller 2 and the controlled object 3, the output signal from the virtual block 12 and the controller 2 The difference is that the subtractor 13 is provided to obtain the difference from the output signal from the second signal power calculation unit 10 and to supply it to the second signal power calculation unit 10.

Therefore, in this embodiment, the signal Φr can be obtained by the virtual block 12 and the signal Φr-u can be obtained by the subtractor 13. here,
u = Ke (where K is the transfer function of the controller 2 and e is the output signal from the subtractor 1), and e = r-Δu-G
_n u, and Φ = K / (1 + KG _n ) {that is, K =
Since it is 1 / (1-ΦG _n )}, it is clear from the transformation of Φr−u = ΦΔu + Φe + ΦG _n u−Ke = ΦΔu + Φe + (ΦG _n −1) Ke = ΦΔu + Φe−Φe = ΦΔu = z that the subtractor 13 The output signal from is z.

As a result, both powers power (u) and power (z) can be obtained as in the block diagram of FIG. 6, and a discrimination result signal indicating whether or not the control system is stable based on the magnitude of both powers. Can be output. FIG. 8 is a diagram showing changes in the control target signal r (see a in the figure) and the output signal y (see b in the figure), and FIG. 9 is a function f = power indicating the ratio of both powers obtained by the apparatus of FIG. (Z) / pow
FIG. 10 is a diagram showing the change of er (u), and FIG. 10 is a function f = power (z) showing the ratio of both powers obtained by the apparatus of FIG.
The figures showing changes in / power (u) are respectively shown. It should be noted that the disturbance is applied when about 3.25 seconds have passed.

As is clear from these figures, f> 1 after about 0.5 seconds from the disturbance being applied,
It can be seen that it is possible to quickly determine the state of the control system. Figure 1
1 is a diagram showing changes in a control target value (see a in the figure) and an output signal (see b in the figure) of a certain control system, FIG. 12 is a diagram showing changes in control deviation corresponding to FIG. 11, and FIG. It is a figure which shows the change of the function f = power (z) / power (u) which shows the ratio of both powers.

As is apparent from FIG. 11, 650 × 0.
Although the control system becomes unstable after 005 seconds has elapsed, the control deviation shown in FIG. 12 has a maximum value of about 70 in the stable state, a maximum value of about 20 in the unstable state, and a threshold value of 70. Since it is set to a value exceeding, it is impossible to determine whether or not it is in a stable state. On the other hand, the value of the function f shown in FIG. 13 exceeds 1 when 740 × 0.005 sec has elapsed, although there is a slight time delay, and it can be determined that the state is unstable.

[0033]

As described above, according to the invention of claim 1, with the conventional method, even if it is in the control state where there is a possibility of making an erroneous determination, it is possible to obtain an accurate value based on the magnitude relationship between both signal powers. Not only can the state be determined, but the deviation in the initial state is large, and the control system has a variable gain, which may cause instability in actual use.
The unique effect of being able to accurately determine the state is achieved.

According to the second aspect of the present invention as well, the conventional method can accurately determine the state based on the magnitude relationship between the two signal powers even in the control state where there is a possibility of making an erroneous determination. Not only is it possible, but the deviation in the initial state is large, and because it has a variable gain, it is possible to accurately determine the state even in a control system that may be unstable in actual use. Produce an effect.

[Brief description of drawings]

FIG. 1 is a flowchart for explaining an embodiment of a control system state determination method of the present invention.

FIG. 2 is a block diagram showing a simplest control system.

FIG. 3 is a diagram showing a system in which a transfer function is ΦΔ.

FIG. 4 is a diagram schematically showing a control system having additive uncertainty.

5 is a block diagram showing a control system obtained by modifying the control system of FIG.

FIG. 6 is a block diagram showing an embodiment of a control system state determination device of the present invention.

FIG. 7 is a block diagram showing another embodiment of the control system state determination device of the present invention.

FIG. 8 is a diagram showing changes in a control target signal and an output signal.

9 is a diagram showing a change of a function f = power (z) / power (u) showing a ratio of both powers obtained by the apparatus of FIG.

10 is a diagram showing a change of a function f = power (z) / power (u) showing a ratio of both powers obtained by the apparatus of FIG.

FIG. 11 is a diagram showing changes in a control target value (see a in the figure) and an output signal (see b in the figure) of a certain control system.

12 is a diagram showing a change in control deviation corresponding to FIG.

FIG. 13 is a function f = power indicating the ratio of both powers.
It is a figure which shows the change of (z) / power (u).

[Explanation of symbols]

 2 Controller 3 Control Target 4 Additive Uncertainty 6 First Signal Power Calculation Unit 7 Virtual Control Target 8 Subtractor 9 Virtual Block 10 Second Signal Power Calculation Unit 11 Discrimination Unit 12 Virtual Block 13 Subtractor

Claims (2)

[Claims] 1. An operation instruction signal is supplied to a controlled object (3) through a controller (2), and an output signal from the controlled object (3) is fed back to the controller (2). A method for determining whether or not a control system having an additive uncertainty (4) in parallel with a controlled object (3) is in a stable state, the power of an input signal to the controlled object (3), and the control (2) and the controlled object (3) the transfer function which is decided based on, the transfer function of additive uncertainty (4) and the signal power which is decided based on the input signal to the controlled object (3) A method for determining the state of a control system, which comprises determining whether or not the control system is stable based on the magnitude of. 2. An operation instruction signal is supplied to a controlled object (3) via a controller (2), and an output signal from the controlled object (3) is fed back to the controller (2). A device for determining whether or not a control system having an additive uncertainty (4) in parallel with a controlled object (3) is in a stable state and calculating the power of an input signal to the controlled object (3). The first signal power calculating means (6), the transfer function determined based on the controller (2) and the controlled object (3), the transfer function of the additive uncertainty (4) and the input signal to the controlled object (3). Second signal power calculating means (7) (8) (9) (1) for calculating the power of the signal determined based on
0) (12) (13), and a determination means (11) for determining whether or not the control system is stable based on the magnitude of both signal powers.