Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
1999-12-28
2001-10-30
Masih, Karen (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S561000, C318S623000, C318S629000, C318S432000, C318S433000, C318S434000, C318S611000, C318S619000
Reexamination Certificate
active
06310456
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel method for designing a control system and to a control device and method therefor and more particularly, to a control system and method which is suitably used for motion control. The present invention also relates to a control system which can be valid for motor speed control and roll-gap position control of a rolling mill or the like, and can perform load following control concurrently with target-value following control to eliminate an impact drop caused by an abrupt change in a load and to realize such accurate control as to cause substantially no generation of a control deviation.
BACKGROUND ART
Various methods have conventionally been proposed as a control system design method and a theoretical system thereof has been already established. In the design based on the classical control theory, however, its target is directed to a control system having one input and one output so that, in order to control a plurality of states at the same time, a control device relating to the most inner state is designed for each state, a control device for the outer loop is designed outside of the most inner state, and so on. That is, there has been employed a multi-looped control system configuration. More specifically, when targets to be controlled are Gp
1
and Gp
2
as shown in
FIG. 3
, a control device Gc
2
is first designed for the control target Gp
1
, the control device Gc
2
is then designed for a loop system of the control target Gp
1
and a control device Gc
1
and for a control system of the control target Gp
2
, and an output thereof is given as a target value of the control device Gc
1
. Similarly, when there is an outer loop not illustrated, a control device Gc
3
is designed for an object Gp
3
to be controlled, an output thereof is given as a target value of the control device Gc
2
, and so on. In this way, design is carried out sequentially from an innermost system to an outer system to form a multiple loop configuration.
It is well known in such a control method that, if an inner control system does not have a response higher than an outer control system, then stable suitable control cannot be realized. Further, an outer control loop depends on an inner control loop, and has a response delayed with respect to the outer control loop.
Further, in a recent control theory, n control devices are designed at one time based on matrix calculation upon designing control devices for a multiplicity of state variables, but physical phenomenon relationships between the control devices and state quantities to be controlled become unclear, leading to the fact that the control system cannot be easily adjusted.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a control system which can remove restrictions of response performances of a plurality of control systems, and can clarify physical phenomenon relationships between the individual control devices and state variables of objects to be controlled for easy adjustment, by providing predetermined response functions determined by a designer for the plural control systems with respect to the objects to be controlled and by designing the control devices for the respective control systems.
In accordance with the present invention, a control device for each of subsystems is sequentially designed so that a frequency response of a control system to be controlled becomes a predetermined control response, and so that outputs of the control devices are added to be used as an operation input to the object to be controlled. That is, the i-th control device is designed so that the response of the i-th control system becomes a predetermined response function from the control devices until (i−1)-th control device already designed so far and the object to be controlled, and the outputs of the n control devices are added to be used as the input operation quantity of the object to be controlled.
Further, suppression control for a disturbance is carried out in a part of the control devices.
In addition, since a control input signal contains a noise signal of a detector and electrical noise applied to a signal cable, presence of a differentiating operation in control operation or calculation may cause the control system to be made unstable under the influence of such various noises as mentioned above. To avoid such a problem, in accordance with the present invention, the control calculation is converted to a state valuable to be differentiated and a state valuable having a differential relationship therewith, which are converted to different calculation loops, so that the control calculations or operations of all the control devices can include only proportional and integral elements and n-order delay elements such as 1- and 2-order delay elements.
In accordance with the present invention, a first control device performs control of following a state of a final object to be controlled to a target value, a second control device performs control over a load disturbance to be applied to a control system to thereby stabilized the control system. Further, even if there is an disturbance variable in a control system to be controlled, there is a state valuable which is to be controlled to be a predetermined value in an upper system of the control system, in which case a third control device is added by separating the function of the second control device therefrom.
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patent: 6051941 (2000-04-01), Sudhoff et al.
patent: 6107767 (2000-08-01), Lu et al.
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patent: 8-083103 (1996-03-01), None
Inaba Hiromi
Iwaji Yoshitaka
Morooka Yasuo
Nakahara Takashi
Okada Takashi
Hitachi , Ltd.
Kenyon & Kenyon
Masih Karen
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