Patent
1994-09-08
1997-10-14
Hafiz, Tariq R.
395900, 395 50, G06F 1518, G06G 700
Patent
active
056779950
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a control method and to a control circuit which effects control using fuzzy logic.
BACKGROUND OF THE INVENTION
An article by Gunter Trautzl having the title "Unscharfe Logic: Fuzzy Logic" has appeared in "der electroniker", No. 3, 1990 at pages 39-43.
In addition to the expression Fuzzy logic for the term "unscharfe Logic", the names, Rule-Base-System, ambivalent logic and multiple value logic are common.
Fuzzy logic had been developed by 1965 in order to be able to also process sets of data that were incomplete or inexact. To this end, with the help of a functional relationship which is often referred to as a Membership-function, the control signal for a control circuit is obtained, for example, from a table of values.
In the said document, this control method is explained on the basis of a carriage on which a bar carrying a mass is fixed so as to be pivotal in the direction of movement of the carriage. The carriage is moved in a horizontal direction by the control circuit such that the bar carrying the mass does not fall over but rather is counter-balanced. Expressed in other words, this means that the carriage imitates the balancing ability of an acrobat who tries to balance a bar in the hollow of his hand.
The status of the bar is described by its angular speed and its angle of deflection which represent the input variables for the controller. The output variable is the speed of the carriage.
This control circuit is described in the following words in the said document:
"The set-up by means of fuzzy logic is as follows: The system has the two input variables, angle .theta. and angular speed w and an output variable, speed v. To start with, one gathers together all the input and output variables according to their values into groups and also provides the functional relationship thereof. For example, one splits the angle into the values, large-positive, middle-positive, small-positive, zero, small-negative, middle-negative, large-negative. Therein, by large, we mean all angles from 20 to 90 degrees (theoretical limit), by middle, all angles between 5 and 25 degrees, by small, all angles between 0 and 10 degrees, as zero, one admits all values between -0.5 degrees and +0.5 degrees. The Membership-function for large is such that, for example, all values above 45 degrees have the relationship factor of 1, but the relationship then drops in order to lie at 0.005 at 20 degrees. The range of values for w and for v is defined in a similar manner. In this way, one achieves an association of the system variables with the Membership-function.
The second part of the set-up for the solution consists in that a system of control is now established in the following form: small-positive. small-positive. small-negative approximate rules (usually values based on experience)."
OBJECT OF THE INVENTION
The object of the invention is now, to develop a control method and a control circuit which effects control using fuzzy logic such that the most important requirements of a control circuit--precision, stability and speed--are fulfilled with the least possible expense.
SUMMARY OF THE INVENTION
In a method in accordance with the first part of claim 1, this object is achieved in that, a plurality of control paths are served by only a single fuzzy controller which is connected to the control paths on a time division multiplex basis.
In a control circuit in accordance with claim 2, this object is likewise achieved in that, a plurality of control paths are served by only a single fuzzy controller which is connected to the control paths on a time division multiplex basis.
BRIEF DESCRIPTION OF THE DRAWINGS
There is shown in
FIG. 1 a first embodiment of the invention;
FIG. 2 a second embodiment of the invention;
FIG. 3 a third embodiment of the invention;
FIG. 4 a fourth embodiment of the invention for a tracking control loop and a focusing control loop.
DETAILED DESCRIPTION
The first embodiment of the invention depicted in FIG. 1 will now be initially described and thereafter its manner
REFERENCES:
patent: 5025499 (1991-06-01), Inoue et al.
Patent Abstracts of Japan, vol. 15, No. 141, 10 Apr. 1991 & Japanese Pat. No. 3-023823 (Omron tateisi Electron Co.) 31 Jan. 1991.
PT Electronica-Elektrotechniek, vol. 46, No. 3, Mar. 1991, Rijswijk NL, pp. 12-15, H. Hellendoorn "Redeneren Met Vage Logica".
Machine Design, vol. 62, No. 18, 6 Sep. 1990, Cleveland, US pp. 92-98, L.A. Berardinis "Tooling Up For The Information Age".
Vestli et al, "Integration of path planning, sensing and control in mobile robots"; Proceedings IEEE International conference on robotics and automation, pp. 243-248 vol. 3, 2-6 May 1993 May 1993.
Huang et al, "A self-paced fuzzy tracking controller for two-dimensional motion control"; IEEE Transactions on systems, man and cybernetics, vol. 20 iss. 5 pp. 1115-1124, Sep.-Oct. 1990 Oct. 1992.
Deutsche Thomson-Brandt GmbH
Hafiz Tariq R.
Herrmann Eric P.
Tripoli Joseph S.
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