JP2741116B2 - Membership function generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membership function generating circuit capable of changing the grade of a membership function used for fuzzy control.

[0002]

2. Description of the Related Art In fuzzy logic, triangular waveform, normal distribution and arc tangent functions as shown in FIGS. 6A, 6B and 6C are widely used as membership functions representing ambiguity.

When fuzzy control is performed using these membership functions, it is necessary to repeat the calculation many times by changing the membership functions variously until a desired control characteristic is obtained, which takes a great deal of labor and time. Work.

A gradient switching circuit for changing the gradient which is a part of the characteristics of the membership function is disclosed in Japanese Patent Laid-Open No. 62-95.
No. 675.

[0005]

However, when a fuzzy system is to be constructed by combining fuzzy control and judgment processing incorporating a learning function, a large number of conditions taken in from the outside are weighted differently and comprehensive judgment is performed. Therefore, it is not enough to switch the gradient of the membership function, and it is desired to change the weighting (called a grade) of the function.

The present invention has been made in view of the above points, and an object of the present invention is to provide a membership function generating circuit capable of changing the grade of a membership function very easily.

[0007]

Means for Solving the Problems P-MOSFET and N-
A plurality of C-MOS inverters composed of MOSFETs are connected in parallel, and switching for grade switching for connecting or disconnecting each of the C-MOS inverters to or from the main circuit is provided, and all C-MOS inverters connected in parallel are provided. MOS
A resistor is connected in series with the inverter, an input signal is applied to a common gate of each C-MOS inverter, and the sum of currents flowing through all the C-MOS inverters is output as a membership function.

[0008]

The membership function is output as the sum of the currents flowing through all the C-MOS inverters connected in parallel. By turning on and off the switches provided in each of the plurality of C-MOS inverters connected in parallel, By changing the number of C-MOS inverters connected in parallel, the grade of the membership function can be changed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows a current-type basic circuit for generating a membership function having a triangular waveform as an embodiment of a membership function generating circuit according to the present invention.

The membership function generating circuit is a P-MO
A first series circuit in which a switch 1c is connected in series to a C-MOS inverter formed by connecting an SFET 1a and an N-MOSFET 1b in series, and similarly a P-MOSFET 2a
, An N-MOSFET 2b and a switch 2c.
, A P-MOSFET 3a and an N-MOSFE
A third series circuit including T3b and a switch 3c;
A fourth series circuit including a MOSFET 4a, an N-MOSFET 4b, and a switch 4c is connected in parallel, and the entire circuit is connected between a power supply V _DD and ground.

The switches 1c to 4c are turned on and off by an external control signal.

An arbitrary analog input signal V _{1N is} now connected to terminal A.
Is applied and the switches 1c to 4c are sequentially turned on, the output signal V _OUT appearing at the terminal B changes as shown in FIG. That is, the output signal when only the switch 1c is ON is I, the output signal when the switches 1c and 2c are ON is II, the output signal when the switches 1c, 2c and 3c are ON is III, and the switches 1c, 2c and 3c, 4
The output signal when all of c are ON is IV. As can be seen from this figure, in the circuit of FIG.
The grade of the membership function of the triangular waveform generated by itself changes depending on the ON and OFF states of c to 4c. The grade change degree is C-M connected in parallel.
It can be easily changed by selecting the value of W / L (W is the gate width of the MOSFET, L is the gate length) of the OS inverter.

The switches 1c to 4 of the basic circuit shown in FIG.
c and the resistor 5 are realized by a MOSFET, and FIG. 3 shows an example thereof.

In FIG. 3, the same reference numerals as those in FIG. 1 denote the same components, and 1c 'to 4c' denote switches 1c.
N-MOSFET for realizing .about.4c, N-MOSFE 5 'which is always on to realize resistor 5
T.

A grade switching signal S is supplied to a terminal C, and N-
By switching ON and OFF of the MOSFETs 1c 'to 4c', the grade of the membership function can be changed as shown in FIG.

The switches 1c to 4 in the basic circuit
c is N-MOSFETs 1c 'to 4c as shown in FIG.
′, It can be realized by connecting P-MOSFETs in series to the power supply _VDD side of the P-MOSFs 1a to 4a.

By the way, the switch 1c in the basic circuit
To 4c are connected in series with the N-MOSFETs 1c ′ to 4c ′ in series with the ground side of the N-MOSFET of the C-MOS inverter. OFF
, The vertex of the membership function of the triangular waveform tends to move to the right as shown by the broken line in FIG. 2 as the grade increases. Also,
Conversely, switches 1c to 4c in the basic circuit are connected to the power supply side of the P-MOSFET of the C-MOS inverter.
In a circuit realized by connecting MOSFETs in series, the vertex of the membership function of the triangular waveform tends to move to the left as the grade increases.

Therefore, even if the grade changes, the vertex of the membership function does not move to the left or right, but simply moves up and down.
A P-MOSFET may be connected to the power supply side of the MOS inverter, and an N-MOSFET may be connected to the ground side, and these may be turned on or off simultaneously. As another method, the value of W / L of the C-MOS inverter may be selected.

Next, FIG. 4 shows a circuit for generating a membership function of an arctangent waveform which is another embodiment of the membership function generating circuit according to the present invention.

In this embodiment, the P-MOSFET 6a and N
-C-MOS formed by connecting MOSFET6b in series
The inverter is a basic C-MOS inverter, and four bias C-MOs are connected in parallel with the basic C-MOS inverter.
An S circuit is connected. The bias C-MOS circuit includes P-MOSFETs 7a, 8a, 9a, 10
a and N-MOSFETs 7b, 8b, 9b, and 10b are connected in series, and inverters 11 to 14 are connected to the gates of the N-MOSFETs 7b to 10b. Digital switching signal S for switching the grade is applied to terminal C.

Now, an arbitrary analog input signal V
_{When 1N} is applied in advance and, for example, "0111" is given to the terminal C as the switching signal S, the P-MOSFET 7a and the N-
Only the bias C-MOS circuit composed of the MOSFET 7b is turned ON, and this C-MOS circuit is connected to the basic C-MOS inverter.
-MOS bias circuits are connected in parallel. as a result,
The output signal V _OUT appearing at terminal B is as shown by I in FIG. Assuming that the switching signal S given to the terminal C is “0011”, two bias C-MOS circuits are connected in parallel to the basic C-MOS inverter, and the output signal V _OUT obtained from the terminal B is indicated by II in FIG. Will be represented. When the other bias C-MOS circuit is turned on, the output signal V
_OUT becomes as shown by III in FIG. 5, and becomes as shown by IV when all the bias C-MOS circuits are turned on.

The degree of change of the grade is similar to that of the embodiment shown in FIG.
It can be easily changed by selecting the value of W / L of the OS inverter.

In this embodiment, the inverters 11 to 1
4 is connected to the gate of the N-MOSFET instead of P
-It may be connected to the gates of MOSFETs 7a to 10a. However, in this case, the logic of the grade switching signal is reversed.

In each of the above two embodiments, the number of C-MOS circuits connected in parallel is four, but this is optional. The greater the number, the more finely the grade of the membership function can be adjusted. can do.

[0026]

As described above, in the present invention, since the number of C-MOS circuits connected in parallel is changed, the grade can be changed instead of the gradient of the membership function. Can be used for fuzzy control. In particular, it is suitable for constructing a fuzzy system combined with a judgment process incorporating a learning function.

[Brief description of the drawings]

FIG. 1 is a basic circuit of a membership function generating circuit according to the present invention.

FIG. 2 is a characteristic diagram of a membership function obtained by a membership function generation circuit shown in FIG.

FIG. 3 is an embodiment of the membership function generating circuit shown in FIG. 1;

FIG. 4 is another embodiment of the membership function generating circuit according to the present invention.

5 is a characteristic diagram of a membership function obtained by the membership generation circuit shown in FIG.

6A and 6B show typical waveforms of the membership function, in which FIG. 6A shows a triangular waveform, FIG. 6B shows a normal distribution, and FIG. 6C shows an arctangent shape.

[Explanation of symbols]

 1a, 2a, 3a, 4a P-MOSFET 1b, 2b, 3b, 4b N-MOSFET 1c, 2c, 3c, 4c Switch 5 Resistance

Claims (4)

(57) [Claims] 1. A grade switching circuit for connecting a plurality of C-MOS inverters each composed of a P-MOSFET and an N-MOSFET in parallel, and connecting or disconnecting each of the C-MOS inverters to or from the main circuit. A switching means is provided, a resistor is connected in series with all the C-MOS inverters connected in parallel, an input signal is applied to a common gate of each C-MOS inverter, and the sum of currents flowing through all the C-MOS inverters is membership. A membership function generation circuit, wherein the output signal represents a function. 2. The switching means is a P-MOSFE.
2. The membership function generating circuit according to claim 1, wherein the membership function generating circuit is configured by a T or N-MOSFET. 3. The membership function generating circuit according to claim 1, wherein said switching means comprises a P-MOSFET and an N-MOSFET connected in series. 4. A basic C-MOS inverter including a P-MOSFET and an N-MOSFET, a plurality of bias C-MOSFETs connected in parallel with the basic C-MOS inverter, and a plurality of bias C-MOSFETs. MOSF
Switching means for switching ON / OFF each of the ETs independently; applying an input signal to a common gate of the basic C-MOS inverter;
A connection point between both MOSFETs forming a MOS inverter and both MOSFETs forming a bias C-MOSFET
A membership function generation circuit, wherein a connection point of T is connected to form a membership function output terminal.