CN1129787C - Scanning tunnel microscope feedback controller adopting multi-modal fuzzy control algorithm - Google Patents

Abstract

The present invention relates to a feedback control device of a scanning tunnel microscope, which adopts a multimode fuzzy control algorithm. The present invention is provided with a sensor, a scanning control circuit, a control computer, an X scanning drive circuit, a Y scanning drive circuit, a Z scanning drive circuit, an X scanner, a Y scanner and a Z scanner, wherein the sensor amplifies tunnel current signals and transmits the signals to the scanning control circuit; the scanning control circuit receives the reference voltage REF-H and REF-L of the control computer, and simultaneously outputs amplified tunnel current signals Im and control signals Ready; when the tunnel current signals Im are less than REF-H and greater than REF-L, the control signals Ready are in high potentials; otherwise, the control signals Ready are in low potentials; the control computer receives control signals Ready output by the scanning control circuit; when the control signals Ready are of high potentials, the control computer outputs scanning drive signals in an X direction and in a Y direction, and the scanners are controlled to scan in the X direction and in the Y direction; when the control signals Ready are of low voltage, the control computer only outputs scanning drive signals in a Z direction, and the scanners are controlled to scan in the Z direction. The present invention has the advantages of accurate scanning, high speed and no distortion.

Description

Adopt the scanning tunnel microscope feedback controller of multi-modal fuzzy control algorithm

Technical field

The present invention relates to a kind of scanning tunnel microscope, particularly a kind of scanning tunnel microscope feedback controller that adopts multi-modal fuzzy control algorithm.

Background technology

Scanning tunnel microscope can be divided into detection of permanent supreme people's court and constant flow method and detect according to the difference of detection mode.Permanent supreme people's court keeps needle point to do scanning motion on the surface level of a constant altitude above the sample, detects the variation of tunnel current, detects pattern and electrical characteristics that data set has been represented sample surfaces.Can make the pattern image of sample surfaces with this data set.Permanent supreme people's court is because height that needn't mobile needle point, and therefore, test speed is very fast; But it is only applicable to level and smooth relatively sample surfaces.Constant flow method is a height of adjusting needle point with the method for feedback, keeps constant tunnel current, and the movement locus of needle point height has reflected the variation of sample surfaces pattern.Constant flow method can be measured irregular surface accurately; But owing to need the ceaselessly height of mobile needle point, so test speed is slower.Because the unknown of sample surfaces pattern, so constant flow method is the main method of using in present this quasi-instrument.

Because being applied between the electric displacement of voltage and piezoelectric ceramics on the piezoelectric ceramics is nonlinear relationship, therefore can not provide the corresponding relation of determining between voltage and the displacement, can only adopt the control of the way realization displacement of FEEDBACK CONTROL, and adopt which kind of control algolithm, just become the direct key factor that influences control performance.The control algolithm of STM employing at present is PID (or PI) algorithm, because piezoelectric ceramics voltage---the electric displacement curve has severe nonlinear, causes adjusting of pid parameter very difficult.Particularly the variation of factors such as environment, condition, time makes the parameter of initially adjusting no longer suitable, the control characteristic variation, and degree of regulation reduces, and governing speed is slack-off.

There are Digital Instruments Co. (USA), Park InstrumentsCo. (USA) etc. in the manufacturer of current scanline tunnel microscope, the performance of domestic production a little less than, market is captured by above-mentioned two families substantially.DI company is assurance X, Y, and the accuracy of three direction displacements of Z adds capacitance displacement sensor respectively in three directions, and the shift value of piezoelectric ceramics is recorded by capacitive transducer.Shortcoming is that capacitive transducer need be demarcated, otherwise data distortion.

Park company is for improving measuring speed, and (2Hz on basis 10Hz), has added the pre-differentiation function of sample topography in two kinds of sweep velocitys of original system.At the sample surfaces of relatively flat, use sweep velocity (10Hz) faster, at uneven relatively sample surfaces, the sweep velocity (2Hz) with slower is improved sweep velocity.Shortcoming or do not throw off time-based scan method can produce data distortion equally.

Summary of the invention

The object of the present invention is to provide a kind of above-mentioned deficiency that overcomes, guarantee the speed and the accuracy of scanning, the scanning tunnel microscope feedback controller of the employing multi-modal fuzzy control algorithm that data can distortion.

The object of the present invention is achieved like this: the scanning tunnel microscope feedback controller that adopts multi-modal fuzzy control algorithm, include sensor Sensor, control computer, X, Y, the Z scan drive circuit, X-axis, Y-axis, Z axle scanner, it is characterized in that also being provided with scan control circuit, sensor Sensor receives the tunnel current signal, with its amplification, reach scan control circuit, scan control circuit receives reference voltage REF-H and the REF-L that control computer is come, tunnel current signal Im and control signal Ready after output is amplified simultaneously, control signal Ready is noble potential at tunnel current signal Im during less than REF-H and greater than REF-L, otherwise be electronegative potential, control computer receives the control signal Ready of scan control circuit output, when control signal Ready is noble potential, computing machine output X, the scanning drive signal of Y direction, and pass through X respectively, Y scan drive circuit control X-axis and Y-axis scanner are made X respectively, the scanning motion of Y direction; When control signal Ready was low-voltage, computing machine was only exported the scanning drive signal of Z direction, and did the scanning motion of Z direction by Z scan drive circuit control Z axle scanner.

The present invention is owing to adopt the foregoing circuit structure and the responsive computer program, thus have scanning accurately, precision is high, the characteristics that sweep velocity is fast, do not have distortion.

Description of drawings

Fig. 1 is an electric structure frame chart of the present invention;

Fig. 2 is the scan control circuit schematic diagram;

Fig. 3 is the FUZZY ALGORITHMS FOR CONTROL process flow diagram.

Embodiment

As shown in Figure 1, adopt the scanning tunnel microscope feedback controller of multi-modal fuzzy control algorithm, include sensor Sensor, scan control circuit, control computer, X, Y, the Z scan drive circuit, X-axis, Y-axis, Z axle scanner, sensor Sensor receives the tunnel current signal, with its amplification, reach scan control circuit, scan control circuit receives reference voltage REF-H and the REF-L that control computer is come, tunnel current signal Im and control signal Ready after output is amplified simultaneously, control signal Ready is noble potential at tunnel current signal Im during less than REF-H and greater than REF-L, otherwise is electronegative potential.Control computer receives the control signal Ready of scan control circuit output, when control signal Ready is noble potential, computing machine is exported the scanning drive signal of X, Y direction, and does the scanning motion of X, Y direction respectively respectively by X, Y scan drive circuit control X-axis and Y-axis scanner; When control signal Ready was electronegative potential, computing machine was only exported the scanning drive signal of Z direction, and did the scanning motion of Z direction by Z scan drive circuit control Z axle scanner.

As shown in Figure 2, scan control circuit is by two-stage amplifier F1 and F2, comparer B1 and B2, XOR gate E, resistance R 1-R8, adjustable resistance P1 and P2, capacitor C 1-C6 constitutes jointly, the negative signal of sensor Sensor connects the pin 3 of first order amplifier F1 through resistance R 1, the positive signal of sensor Sensor connects the pin 2 of first order amplifier F1 through resistance R 2, the pin 2 of F1 is also by capacitor C 4 ground connection, connect the pin 6 of F1 by resistance R 4, the pin 6 of F1 links to each other with the pin 5 of F1 by capacitor C 2, the pin 5 of F1 connects-the 15V power supply together by the pin 4 of capacitor C 1 and F1, the pin 3 of F1 is also by the in parallel ground connection of resistance R 3 with capacitor C 3, the pin 8 of F1 links to each other with the pin 1 of F1 by adjustable resistance P1, the adjustable end of adjustable resistance P1 and the pin 7 of F1 connect+the 15V power supply together, the pin 6 of F1 is also by capacitor C 5 ground connection, the pin 6 of F1 also connects resistance R 5, and the other end of resistance R 5 is respectively by capacitor C 6 ground connection, receive the pin 2 of second level amplifier F2 by resistance R 6; The pin 2 of second level amplifier F2 links to each other with the pin 6 of F2 by resistance R 7, adjustable resistance P2, and the pin 3 of F2 is by resistance R 8 ground connection, and the pin 4 of F2 connects-the 15V power supply, and the pin 7 of F2 connects+the 15V power supply, and the pin 6 of F2 also connects the pin 3 of comparer B1, B2 respectively; The pin 2 of comparer B1 connects the output reference voltage REF-H of control computer, the pin 2 of B2 connects the output reference voltage REF-L of control computer, the output terminal pin 7 of comparer B1 connects the input end 1 of XOR gate E, the output terminal pin 7 of B2 connects the input end 2 of XOR gate E, the output terminal 3 of XOR gate exports computing machine to, be the Ready control signal, the pin 6 of amplifier F2 is also exported the current input terminal Im that a signal is connected to control computer.The model of amplifier F1 is in this circuit: μ A725, and the model of F2 is: μ A741; The model of comparer B1, B2 is LM393; The model of XOR gate is 7486.

After the output signal of control circuit entered computing machine, computing machine carried out computing according to fuzzy control program, the idiographic flow of its program as shown in Figure 3:

Program is called in internal memory with program from hard disk since 100, the CPU program that brings into operation; 101 executive system initialization, CPU receives operator's tunnel current setting value by a keyboard entry; Traveling probe makes it near sample, and enters tunnel state;

102 read the tunnel current detected value from A/D converter; 103 usefulness tunnel current setting values subtract the tunnel current detected value, and its difference is a deviation, and deviation is composed to deviation register e; Program changes 104 over to;

104 judge that whether deviation register e is zero, if the result is True, then changes 105 over to; If be False, then change 108 over to;

108 carry out the operation of calculation deviation rate of change, and deviation variation rate Δ e is determined by following formula: $\mathrm{\Δe}=\frac{e}{\mathrm{\Δt}};$ The 109 couples of e and Δ e carry out the obfuscation operation, and program changes 110 over to;

110 results according to obfuscation call the fuzzy control rule subroutine; 111 call the fuzzy inference rule subroutine; 112 carry out fuzzy judgment according to result of calculation operates, and draws output variable;

113 according to output variable generation output control increment; Program changes 114 over to;

114 store increment size, and carry out the D/A conversion, the voltage of a 0～5V of output;

115 send this voltage into high pressure generator, and (some piezoelectric ceramic devices is with 0～150V) voltage to produce corresponding 0～300V; 116 are added to this voltage on the piezoelectric ceramics, make probe produce corresponding displacement; Program flow returns 102 then, continue to carry out repeatedly;

105 judge whether each point of inswept presumptive area, if be True, program changes 106 over to; If be False, program changes 114 over to, continues to carry out;

106 pairs of data of being stored are handled, and data are sent into visual memory buffer, for displayed image on display is got ready; 107 FEEDBACK CONTROL EOP (end of program).

Claims (3)

1. scanning tunnel microscope feedback controller that adopts multi-modal fuzzy control algorithm, include sensor Sensor, control computer, X, Y, the Z scan drive circuit, X-axis, Y-axis, Z axle scanner, it is characterized in that also being provided with scan control circuit, sensor Sensor receives the tunnel current signal, with its amplification, reach scan control circuit, scan control circuit receives reference voltage REF-H and the REF-L that control computer is come, tunnel current signal Im and control signal Ready after output is amplified simultaneously, control signal Ready is noble potential at tunnel current signal Im during less than REF-H and greater than REF-L, otherwise be electronegative potential, control computer receives the control signal Ready of scan control circuit output, when control signal Ready is noble potential, computing machine output X, the scanning drive signal of Y direction, and pass through X respectively, Y scan drive circuit control X-axis and Y-axis scanner are made X respectively, the scanning motion of Y direction; When control signal Ready was low-voltage, computing machine was only exported the scanning drive signal of Z direction, and did the scanning motion of Z direction by Z scan drive circuit control Z axle scanner.

2. the scanning tunnel microscope feedback controller of employing multi-modal fuzzy control algorithm according to claim 1, it is characterized in that, scan control circuit is by two-stage amplifier F1 and F2, comparer B1 and B2, XOR gate E, resistance R 1-R8, adjustable resistance P1 and P2, capacitor C 1-C6 constitutes jointly, the negative signal of sensor Sensor connects the pin 3 of first order amplifier F1 through resistance R 1, the positive signal of sensor Sensor connects the pin 2 of first order amplifier F1 through resistance R 2, the pin 2 of F1 is also by capacitor C 4 ground connection, connect the pin 6 of F1 by resistance R 4, the pin 6 of F1 links to each other with the pin 5 of F1 by capacitor C 2, the pin 5 of F1 connects-the 15V power supply together by the pin 4 of capacitor C 1 and F1, the pin 3 of F1 is also by the in parallel ground connection of resistance R 3 with capacitor C 3, the pin 8 of F1 links to each other with the pin 1 of F1 by adjustable resistance P1, the adjustable end of adjustable resistance P1 and the pin 7 of F1 connect+the 15V power supply together, the pin 6 of F1 is also by capacitor C 5 ground connection, the pin 6 of F1 also connects resistance R 5, and the other end of resistance R 5 is respectively by capacitor C 6 ground connection, receive the pin 2 of second level amplifier F2 by resistance R 6; The pin 2 of second level amplifier F2 links to each other with the pin 6 of F2 by resistance R 7, adjustable resistance P2, and the pin 3 of F2 is by resistance R 8 ground connection, and the pin 4 of F2 connects-the 15V power supply, and the pin 7 of F2 connects+the 15V power supply, and the pin 6 of F2 also connects the pin 3 of comparer B1, B2 respectively; The pin 2 of comparer B1 connects the output reference voltage REF-H of control computer, the pin 2 of B2 connects the output reference voltage REF-L of control computer, the output terminal pin 7 of comparer B1 connects the input end 1 of XOR gate E, the output terminal pin 7 of B2 connects the input end 2 of XOR gate E, the output terminal 3 of XOR gate exports computing machine to, be the Ready control signal, the pin 6 of amplifier F2 is also exported the current input terminal Im that a signal is connected to control computer.

3. the scanning tunnel microscope feedback controller of employing multi-modal fuzzy control algorithm according to claim 1, after the output signal that it is characterized in that control circuit enters computing machine, computing machine carries out computing according to fuzzy control program, and the idiographic flow of its program is:

Program is called in internal memory with program from hard disk since 100, the CPU program that brings into operation; 101 executive system initialization, CPU receives operator's tunnel current setting value by a keyboard entry; Traveling probe makes it near sample, and enters tunnel state;

102 read the tunnel current detected value from A/D converter; 103 usefulness tunnel current setting values subtract the tunnel current detected value, and its difference is a deviation, and deviation is composed to deviation register e; Program changes 104 over to;

104 judge that whether deviation register e is zero, if the result is True, then changes 105 over to; If be False, then change 108 over to;

108 carry out the operation of calculation deviation rate of change, and deviation variation rate Δ e is determined by following formula: $\mathrm{\Δe}=\frac{e}{\mathrm{\Δt}};$ The 109 couples of e and Δ e carry out the obfuscation operation, and program changes 110 over to;

110 results according to obfuscation call the fuzzy control rule subroutine; 111 call the fuzzy inference rule subroutine; 112 carry out fuzzy judgment according to result of calculation operates, and draws output variable;

113 according to output variable generation output control increment; Program changes 114 over to;

114 store increment size, and carry out the D/A conversion, the voltage of a 0～5V of output;

115 send this voltage into high pressure generator, produce the voltage of corresponding 0～300V; 116 are added to this voltage on the piezoelectric ceramics, make probe produce corresponding displacement; Program flow returns 102 then, continue to carry out repeatedly;

105 judge whether each point of inswept presumptive area, if be True, program changes 106 over to; If be False, program changes 114 over to, continues to carry out;

106 pairs of data of being stored are handled, and data are sent into visual memory buffer, for displayed image on display is got ready; 107 FEEDBACK CONTROL EOP (end of program).

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