Controlling method to follow-up target valve

Abstract: A controlling method in a control system comprising a target value setting portion (1) for setting a target value Y of the controlled physical quantity, a desired variation operation portion (2) for obtaining a desired variation dXw of the controlled physical quantity in accordance with a target value Y and a present value of the controlled physical quantity, a control demand output portion (3) for outputting a control demand value in accordance with the desired variation dXw so as to change the controlled physical quantity by the function of the controlled apparatus (4) in accordance with the control demand value is caused the controlled physical quantity to follow a target value smoothly to maximum.

Description: The present invention relates to a target value follow-up controlling method. In a controlling system of digits to be measured, calculated; outputted for each control cycle, a control demand value obtained by the calculation. in accordance with a present value of a certain controlled physical quantity and a target value given by some means are given to a controlled apparatus so as to operate the controlled apparatus in accordance with a control demand value for causing the controlled physical quantity to change to follow up the target value. This controlling operation is widely effected in an automatic control system. In this type of controlling method, it is a primary object to smoothly follow the controlled physical quantity to a target value. But a long time is often required to reach the target value. It is often impossible to follow the target value by a hunting operation caused. Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent in the prior art and for its essential object to provide an improved target value follow-up controlling method. Another important object of the present invention is to provide an improved target value follow-up controlling method capable of causing the controlled physical quantity as smoothly as possible to follow up the target value. According to the invention, as defined by claim 1, there is provided a target value follow-up controlling method comprising the steps of setting, in a target value setting portion of a control system which comprises, in succession, said target value setting portion, a desired variation operation portion, a control demand output portion, and a controlled apparatus, a target value (Y) of a controlled physical quantity for the present cycle, obtaining, in said desired variation operation portion, a desired variation per cycle (dXw) of the controlled physical quantity on the basis of said target value (Y) and a present measured value (X) of the controlled physical quantity; and obtaining in said control demand output portion a control demand value (Z) to be output to-the controlled apparatus during the present cycle, whereby said desired variation per cycle (dXw) of the controlled physical quantity is calculated by the desired variation operation portion by separating the total deviation (Y-X) of the controlled physical quantity into two component parts, namely into a new deviation (dY) and into an existing deviation (Y -1 -X), on the basis of the formula; dXw = dY x m + (Y -1 -X)xn where; m: is the first deviation elimination rate where: 0 ≤ m ≤ 1, n: is the second deviation elimination rate where; 0 ≤ n ≤ 1, dY: is the variation of the target value for present cycle where; dY = Y - Y -1 , Y -1 : is the target value of controlled physical quantity for present cycle, calculated in the previous cycle, X: is the present measured value of the controlled physical quantity, Y: is the target value of the controlled physical quantity for next cycle, calculated in present cycle. In accomplishing these and other objects, according to one preferred embodiment of the present invention, the target follow-up controlling method further comprises the steps of outputting the control demand value Z in accordance -with inverse function Z = f -1 (dXw), whereby the said inverse function relates to the inverse of a function f which defines the relationship between the control demand value Z and a variation dX of the controlled physical quantity and whereby the controlled apparatus (4) responds to said obtained control demand value Z by changing said controlled physical quantity. In a preferred embodiment of the present invention, a control demand value Z to be outputted at the present cycle Z = f -1 (dXw, P) where P is a parameter reflecting the condition of the control system. The f can be considered an expectation value with respect to distribution. The P shows a parameter collectively when the reaction of the controlled apparatus (4) changes with respect to the same Z. For example, the P can be X or dX, the other physical quantity capable of measuring operation for reference, or a combination of them. Assume that the P is included in the function f if necessary, and it can be made as simple as dX = f (Z), Z = f -1 (dXw). The function f is to previously suppose a proper shape as defined by claim 2 of parent application 93 121 118.9 so that a constant in it can be learned from the actual value. Since in embodiments of the present invention Y is a target value of the next cycle calculated by the present cycle, Y -1 = Y - dY shows the target value of the present cycle calculated by the previous cycle. Namely, the total deviation (Y - X) can be separated into the new deviation dY and the existing deviation (Y - dY - X). A recommended shape of the function g means the respective independent setting of disappearing speed of the elimination rate of the existing deviation and the disappearing speed of the new deviation. The above described coefficients m, n- discriminate, when the method is implemented according to accompanying claims 4 to 7, situations by the sign of dY, (Y - X) and the other methods, can be set in accordance with the situation, and the control has an effect especially of restraining the hunting operation. The invention will be better understood by referring, by way of example, to the accompanying drawings, in which; Fig. 1 is a diagram showing a control system to which a controlling method of the present invention is applied; Fig. 2 is a time chart showing the following to a target value of the present value; and Fig. 3 is a time chart showing the control operation of the apparatus of Fig. 2. Before the description of preferred ways of implementing the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Fig 1 shows a control system to which a particular form of the controlling method of the present invention is applied. Reference numeral 1 is a target value setting portion for calculating a target value Y in accordance with some measured value 3 for reflecting an external input A and / or a control system condition, reference numeral 2 is a desired variation operation portion for obtaining a desired variation dXw of the controlled physical quantity in accordance with the target value Y and a measured value X of the controlled physical quantity, reference numeral 3 is a control demand output portion for outputting a control demand value Z in accordance with a desired variation dXw and a parameter P for reflecting the condition of the control system, reference numeral 4 is a controlled apparatus to be operated in accordance with a control demand value Z. The control demand output portion 3 is defined as an inverse function Z =f -1 (dX, P) of a function (namely, a characteristic function of a controlled apparatus (4) dX = f (Z, P) between a control demand value Z and a variation dX of the controlled physical quantity to be realized through a controlled apparatus (4) due to outputting of a control demand value Z during one control cycle. When the desired variation dXw is inputted to the control demand output portion (3), Z = f -1 (dXw, P) is outputted. The function f can be considered an expectation value with respect to distribution having certain dispersion. A parameter P summarily shows a parameter in a case where the reaction of a controlled apparatus (4) changes with respect to the same control demand value Z. For example, the P may be X or dX, the other physical quantity to be measured for reference or a combination of them. The function f is to previously suppose a proper shape so that a constant in it can be learned from actual values. When the function f is supposed as dX = a x Z + b as the simplest example, a constant b only can be learned with a constant a being fixed. It is considered for the b to be slowly followed towards (dX - a x Z) calculated from each actual result values Z and dX. The Z with respect to dXw is obtained as Z = (dXw - b) / a with the use of leaned b in accordance with the inverse function f -1 of this case. In accordance with a preferred way of putting the invention into effect, when the desired variation dXw exceeds a limit of the control performance of the controlled apparatus (4), the dXw enters a region of the function f -1 not defined. In this case, a maximum value is given immediately as the Z and the X is left from the Y. A way of dealing with this problem is achieved by the following control. A desired variation operation portion 2 is taken into consideration. dXw = W - X shows the desired variation to be expected by the next cycle, wherein the present value is X, Y is a target value of the next cycle, W is a desired value showing how far X is approached in the next cycle. Y -1 is a target value with respect to the present cycle calculated by the previous cycle and dY = Y - Y -1 is a variation of a target value. Assume that dXw = (Y - X) x n, because the (Y - X) is a deviation between a target value arid the present value. This means that the deviation is intended to be eliminated by 1 / n cycle. Y - X = dY + (Y -dY - X) = dY + (Y -1 - X) Assume that dXw = dY × m + (Y -1 -X) × n (0 ≤ m ≤ 1, 0 ≤ n ≤ 1) and it is intended to be eliminated with 1 / m cycle in 1 / m cycle in the former, and 1 / n cycle in the latter with the total deviation value (Y - X) being split up as between the new deviation dY and the existing deviation (Y -1 -X). The following advantage is provided by the separation between the disappearing speed of the new deviation and the disappearing speed of the existing deviation. When the sign of the dY is different from that of (Y -1 -X), it is found from the combination of m, n that the sign of dXw can be inverted. This suggests from the situation that the control characteristics can be changed considerably depends upon a situation by only change in m, n. When m, n are made larger (close to 1), weaker noises, instead of faster following, are provided. When the m, n are made smaller (close to 0), it becomes opposite. In addition to the above described common characteristics, there is a considerable effect in restraining the hunting that the phase delay of the X with respect to Y is reduced when the m / n is made larger. From the fact, it is recommended that the phase be considered seriously, namely, m / n be relatively made larger, at a time when (dY > 0) and (Y or Y -1 be < X or ≤ X, namely, Y is smaller than X) or (dY < 0) and (Y or Y -1 be > X or ≥ X, namely, Y is larger than X). At a time except for it, the following property is considered seriously, namely, m / n is relatively made small. In further detailed control, the sign of the variation ddY of the dY can be also considered. As the phase should be considered most seriously at a time when (dY > 0) and (Y is smaller than X) and (ddY > 0) or (dY < 0) and (Y is larger than X) and (ddY < 0) the m / n can be set into two stages, three stages or four stages from three sign relation. At a time dY = 0, following property is considered seriously, namely, m / n is required to be kept relatively smaller (in this case, it means that n is substantially made sufficiently large, because dY × m = 0) Even except for it, the division is effected in accordance with the characteristics of the control system, and m and n can be switched in value in accordance with the case. When the noise of Y is relatively small, m can be made larger. When the noise of Y is sufficiently small practically, m = 1 is desirable. If m = 1, X = Y -1 in dY = const, namely, when the change speed of the Y is constant, the following operation can be effected without constant deviation (needless to say, the controlling operation is restricted to time where dY is within the performance range of the controlled apparatus). Noises of X may become large especially when the Z changes suddenly. The n often cannot be made too large except when the following property is not considered seriously. When such fear exists, dXw including noises is calculated, thereafter a filter may applied upon dXw so as to calculate Z. The calculation is effected till Z with the noises being included as they are, and thereafter, the filter processing operation is effected. The outputting operation can be effected. The relation among the above described noise and m, n show the relative tendency strictly. As is clear from the foregoing description, the present method is especially effective in a case where a target value is adapted to change in connection with the controlled physical quantity. Some factors, for example, a case where the capability of the controlled apparatus is lower than the dXw temporarily, if Y comes smaller after X is left later than Y because of dispersion or the like in the response of the controlled apparatus and thereafter, namely, if dY becomes negative, the X still tries to follow the Y, thus the X outruns the Y, so that a hunting phenomenon is caused. It is known that a phenomenon where X and Y outruns each other because of the shift in phase is likely to be caused in a case where there is some cause and effect relationship between X and Y. According to the present method, the Z can be made negative relatively earlier when the dY becomes negative. Therefore, X is restrained from outrunning Y so that a stable controlling operation can be restored.

Claims: A target value follow-up controlling method comprising the steps of setting, in a target value setting portion (1) of a control system which comprises, in succession, said target value setting portion (1), a desired variation operation portion (2), a control demand output portion (3), and a controlled apparatus (4), a target value (Y) of a controlled physical quantity for the present cycle, obtaining, in said desired variation operation portion (2), a desired variation per cycle (dXw) of the controlled physical quantity on the basis of said target value (Y) and a present measured value (X) of the controlled physical quantity; and obtaining in said control demand output portion (3) a control demand value (Z) to be output to the controlled apparatus (4) during the present cycle, whereby said desired variation per cycle (dXw) of the controlled physical quantity is calculated by the desired variation operation portion (2) by separating the total deviation (Y-X) of the controlled physical quantity into two component parts, namely into a new deviation (dY) and into an existing deviation (Y -1 -X). on the basis of the formula; dXw = dY x m + (Y -1 -X)xn where; m: is the first deviation elimination rate where: 0 ≤ m ≤ 1, n: is the second deviation elimination rate where; 0 ≤ n ≤ 1, dY: is the variation of the target value for present cycle where; dY = Y - Y -1 , Y -1 : is the target value of controlled physical quantity for present cycle, calculated in the previous cycle, X: is the present measured value of the controlled physical quantity, Y: is the target value of the controlled physical quantity for next cycle, calculated in present cycle. A target value follow-up controlling method as claimed in claim 1, further comprising the step of having the deviation elimination rates m, n each adapted to be changed in their value by some character to reflect the condition of the control system. A target value follow-up controlling method as claimed in claim 2, further comprising the step of having the ratio m/n of the deviation elimination rates m, n adapted to be set relatively larger by the desired variation operation portion (2), when dY > 0, and Y is smaller than X or dY < 0 and Y is larger than X, than under all other operating conditions. A target value follow-up controlling method as claimed in claim 3, further comprising the step of having the ratio m/n of the deviation elimination rates m, n adapted to set largest by the desired variation operation portion (2) in a case where dY > 0, Y is smaller than X and ddY > 0 or dY < 0 and Y is larger than X and ddY < 0 when the variation of the dY is made ddY. A target value follow-up control method as claimed in claim 1, further comprising a step of having the deviation elimination rate m of the new deviation adapted to be set to m=1 by the desired variation operation portion (2). A target value follow-up controlling method as claimed in claim 1, 2, 3, 4 or 5, further comprising the step of having a variation dXw restrained, from dXw -1 outputted in the previous cycle with respect to dXw once calculated by-the desired variation operation portion (2), and thereafter outputting it. A target value follow-up control method as defined in claim 1, 2, 3, 4 or 5, further comprising the step of having a variation dZ restrained, from Z -1 outputted with the previous cycle with respect to Z once calculated by the control demand output portion (3), and thereafter outputting it. A target value follow-up controlling method as defined in claim 1, 2, 3, 4, 5, 6 or 7, further comprising the step of having the target value setting portion (1) adapted to be set depending at least upon the measured value which is relative to controlled physical quantity or controlled physical quantity.

Inventors: KATO KAZUHIRO, MIYAWAKI YOICHI, TAKATA KOJI, KATO, KAZUHIRO, MIYAWAKI, YOICHI, TAKATA, KOJI, Kato, Kazuhiro c/o Itami Works of, Miyawaki, Yoichi c/o Itami Works of, TAKATA, KOJI C/O ITAMI WORKS OF
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES, LTD.
Application year: 1993
Main classification: G05B15
IPC codes: G05B15