CN110646673A - Automatic impedance matcher for magnetostrictive transducer - Google Patents
Automatic impedance matcher for magnetostrictive transducer Download PDFInfo
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- CN110646673A CN110646673A CN201910939903.9A CN201910939903A CN110646673A CN 110646673 A CN110646673 A CN 110646673A CN 201910939903 A CN201910939903 A CN 201910939903A CN 110646673 A CN110646673 A CN 110646673A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/08—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with magnetostriction
Abstract
The invention relates to an automatic impedance matcher for a magnetostrictive transducer. The automatic impedance matcher comprises an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module; the impedance matching module comprises two sets of 8 paths of relay modules with an optical coupling isolation function, a 5V direct-current power supply, 16 CBB matching capacitors and 16 resistors with the resistance value of 1k omega; the two sets of relay modules have the same structure and respectively comprise 8 relays connected in parallel; the DC + and DC-ports of each set of relay module are respectively connected to the anode c and the cathode d of a 5V direct-current power supply; the high-low level of each relay triggers the selection terminals S1-S16 to be respectively plugged with a matched H jumper cap. The invention enables the transducer to continuously and stably work in a resonance state under different environments, working conditions and loads, and obviously improves the working efficiency of the transducer.
Description
Technical Field
The invention relates to an impedance matcher, in particular to an automatic impedance matcher for a magnetostrictive transducer. The method specifically adopts an impedance matching module, a signal acquisition module, a feedback module and a single chip microcomputer control module to realize the dynamic automatic impedance matching between a power supply and the magnetostrictive transducer.
Background
Magnetostrictive transducers are electromagnetic mechanical devices that convert energy using magnetostrictive materials, which are devices that convert one form of energy into another form of energy. The method is widely applied to the fields of underwater sound, ultrasonic, active vibration control and the like.
The impedance matching between the magnetostrictive transducer and the power supply directly affects the operating efficiency of the magnetostrictive transducer. In recent years, the manufacturing process of the magnetostrictive transducer is mature, but the application of the magnetostrictive transducer is restricted by the relatively slow development of intelligent impedance matching.
In order to improve the performance of the magnetostrictive transducer, such as output power and energy conversion efficiency, impedance matching between the transducer and a power supply is required. The magnetostrictive transducer is in a resistance sense and can be equivalently connected in series with a resistor and an inductor, and the resistance matching is carried out on the magnetostrictive transducer according to the circuit knowledge, so that the sensitivity of the magnetostrictive transducer can be eliminated, the magnetostrictive transducer can work in a resonance state, and the working performance is improved. At present, two main impedance matching methods are static matching and dynamic matching.
The principle of static matching is that the impedance characteristic of the magnetostrictive transducer is measured by a precise impedance analyzer to obtain the values of the equivalent resistance R and the equivalent inductance L of the transducer, and the capacitance value to be matched is obtained by formula calculation in combination with the resonant frequency, so that matching is completed. Through static matching, the reactive power of the transducer can be eliminated, so that the transducer works in a resonance state, the working efficiency is improved, and the method is simple and feasible. However, during the operation of the transducer, the impedance characteristics of the transducer may change due to changes in the environment, temperature, load, etc., thereby causing a frequency drift phenomenon. At this point, the applied matching capacitance will no longer meet the requirements and the transducer will no longer operate at resonance.
The dynamic matching mainly includes a variable capacitance matching method and a frequency tracking method. The principle of the variable capacitance matching method is that a control circuit controls the rotation of a driving motor according to the detected amplitude, phase and other information of voltage and current, so that the numerical value of a variable capacitor is adjusted, and impedance matching is completed. The method has the advantages of complex structure and high cost. The principle of the frequency tracking method is that a control circuit adjusts the output frequency of a driving power source according to information of the amplitude, phase, etc. of detected voltage and current. On the premise of ensuring that the matching capacitance parameter determined by static matching is not changed, the output frequency of the driving power supply is changed along with the change of the resonance frequency of the transducer, and dynamic impedance matching is indirectly completed. The method has more complex structure and elements, needs static matching as assistance, and is more suitable for occasions where the output frequency needs to be changed.
Disclosure of Invention
In view of the above-mentioned impedance matching deficiencies, the present invention provides an automatic impedance matcher for magnetostrictive transducer with high speed, wide range and high precision and a method for implementing the same. According to the automatic impedance matcher, a signal acquisition module consisting of high-precision sampling resistors is selected to acquire circuit signals, so that extra phase difference caused by a sampling circuit is effectively avoided; two sets of 8-path relay modules with optical coupling isolation functions are selected, and each relay is connected with a capacitor. The single chip microcomputer is used for controlling the relay, and under the premise that the output frequency of the driving power supply is not changed, the input voltage and the current of the transducer are locked to be in the same phase state by adjusting the matching capacitance value in a variable step length mode, so that automatic impedance matching is completed. The transducer can continuously and stably work in a resonance state under different environments, working conditions and loads, and the working efficiency of the transducer is obviously improved.
The technical scheme of the invention is as follows:
an automatic impedance matcher for a magnetostrictive transducer comprises an impedance matching module, a signal acquisition module, a feedback module and a single-chip microcomputer control module;
the connection relationship is as follows: one end of the impedance matching module is connected with the output end of the power supply, and the other end of the impedance matching module is connected with one end of the magnetostrictive transducer; one end of the signal acquisition module is connected with the output end of the power supply, the other end of the signal acquisition module is connected with the other end of the magnetostrictive transducer, and the output end of the signal acquisition module is connected with one end of the feedback module; the other end of the feedback module is connected with one end of the singlechip control module; the output end of the singlechip control module is connected to the signal input end of the impedance matching module, and the PC is connected to the other end of the singlechip control module;
the impedance matching module comprises two sets of 8 paths of relay modules with an optical coupling isolation function, a 5V direct-current power supply, 16 CBB capacitors and 16 resistors with the resistance value of 1k omega; the two sets of relay modules have the same structure and respectively comprise 8 relays connected in parallel; the DC + and DC-ports of each set of relay module are respectively connected to the anode c and the cathode d of a 5V direct-current power supply; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with a matched H jumper cap; the input signal trigger port IN1-IN16 of each relay is respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normally open end NO1-NO16 of each relay is connected to the m end which is connected to the output end of the transducer driving power supply; the common end COM1-COM16 of each relay is correspondingly connected with one end of a CBB capacitor, the other end of each CBB capacitor is connected with an n end, and the n end is connected with the input end of the transducer; the normally closed end NC1-NC16 of each relay is connected with one end of a 1k omega resistor, and the other end of each resistor is connected to the other end of the CBB capacitor;
the signal acquisition module comprises three precision sampling resistors R31、R32、R33(ii) a The connection relation is a resistor R31One end of the impedance matching module is connected with the m end of the impedance matching module; resistance R31Another terminal of (1) and a resistor R32One end of the two ends are connected; resistance R32Another terminal of (1) and a resistor R33One end of the two ends are connected; resistance R33And to an input b2 of transducer b; resistance R31And is also connected to an output terminal a1 of power supply a; resistance R32One end of the voltage sampling terminal is also connected with a voltage sampling terminal SV 2; resistance R32The other end of the voltage sampling circuit is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; resistance R33One end of the current sampling terminal is also connected with a current sampling terminal SC 2; resistance R33And the other end of (2) also samples the currentTerminal SC 1; the n-terminal of the impedance matching block is connected to the other input terminal b1 of transducer b.
The feedback module circuit comprises a differential amplifier adopting an LM324 type operational amplifier, a proportional amplifier adopting the LM324 type operational amplifier and a phase difference detection circuit;
the phase difference detection circuit comprises two high-speed zero-crossing comparators A and B consisting of LM339 chips, a D trigger adopting a 74LS74 chip and an exclusive-OR gate adopting a 74LS86 chip; the connection relation of the modules is that the positive input end of the differential amplifier is connected with the current sampling end SC2 of the signal acquisition module, the negative input end of the differential amplifier is connected with the current sampling end SC1, and the output end of the differential amplifier is connected with the negative input end of a high-speed zero-crossing comparator A in the phase difference detection circuit; the input end of the proportional amplifier is connected with a voltage sampling port SV2 of the signal acquisition module, and the output end of the proportional amplifier is connected with the negative input end of a high-speed zero-crossing comparator B in the phase difference detection circuit; the output ends of the two high-speed zero-crossing comparators are respectively connected to a D port and a CLK port of the D trigger, and a set input S and a reset input R of the D trigger are both grounded; the output ends of the two high-speed zero-crossing comparators are respectively connected to the input ends of the exclusive-or gates.
The control method of the magnetostrictive transducer automatic impedance matcher comprises the following steps:
the first step, the device is powered on and started, the system is initialized, and then the second step is carried out;
secondly, after delaying for 10ms, the signal acquisition module performs voltage sampling and current sampling on the transducer;
thirdly, the single chip microcomputer judges whether the zero-crossing frequency n of current in one period is greater than 3, if yes, two sets of 8-path relay modules with the optical coupling isolation function in the impedance matching module are controlled, the matching capacitor is increased according to the Step length of Step0 being 1 mu F by controlling the starting and stopping of the relay, and then the third Step is returned to continue judging; if n is greater than 3, executing the fourth step;
step four, judging whether the phase difference theta output by the feedback module is more than 50 degrees, if yes, making Step equal to 1 mu F, namely, a large Step length, and jumping to the Step seven; if not, executing the fifth step;
fifthly, judging whether the phase difference theta output by the feedback module is more than 20 degrees, if yes, making Step equal to 0.2 mu F, namely, the Step length, and jumping to the seventh Step; if not, executing the sixth step;
sixthly, judging whether the phase difference theta output by the feedback module is more than 5 degrees, if yes, making Step be 0.1 mu F, namely, a small Step length, and executing the seventh Step; if theta is greater than 5 degrees, the automatic impedance matching is finished once, and the operation is finished;
and seventhly, judging whether the phase relation Q of the voltage and the current output by the feedback module is 0, and controlling two sets of relays in the relay module with the optical coupling isolation function in the impedance matching module according to a judgment result: if Q is equal to 0, increasing the matching capacitor according to the Step value of Step by controlling the starting and stopping of the relay, and then jumping back to the second Step; if Q is not equal to 0, reducing the matching capacitance according to the Step value of Step by controlling the starting and stopping of the relay, and then jumping back to the second Step; and continuing to execute the automatic matching process until the theta is not over 5 degrees in the sixth step, and ending the operation.
The invention has the beneficial effects that:
1. the magnetostrictive transducer automatic impedance matcher has high matching precision (0.1 muF), wide matching range (0.1-39.0 muF) and high matching speed (ms level).
2. The signal acquisition module of the automatic impedance matcher samples voltage and current signals in real time, the feedback module processes the sampled signals and feeds the sampled signals back to the single-chip microcomputer control module on line, the single-chip microcomputer control module controls the start and stop of a relay according to a matching program to realize the real-time automatic switching of series capacitors, the optimal matching capacitor is selected, and the automatic impedance matching of the magnetostrictive transducer is completed. The automatic impedance matcher can adjust the input voltage and the current of the transducer to be in the same phase state on the premise of ensuring that the output frequency of the driving power supply is unchanged, so that a good sine working current waveform is obtained, and the transducer is always kept to work in a resonance state.
3. The signal acquisition module of the automatic impedance matcher samples voltage and current signals by adopting a resistance sampling method, avoids extra phase difference brought by a sampling circuit, and improves the precision of automatic impedance matching by nearly 20% compared with other sampling methods.
4. The automatic matching program of the invention adopts a variable step length method for matching. Three step lengths with different sizes are selected according to the phase difference, so that the automatic impedance matching time can be effectively shortened by about 30%, and the matching efficiency is improved.
5. The 89S51 main control chip adopted by the control module is an 8-bit main control chip, so that the performance is stable, the cost is low, and the processing speed and the processing precision of the instruction are ensured while the cost is saved; the Flash memory is included, so that the program can be repeatedly modified, the development period is shortened, data and instruction information can be effectively transmitted in the working process of the system, and a good reaction mechanism is provided when an external power supply is suddenly damaged; the volume is small, so that the volume of the product is minimized; and a static clock mode is adopted, so that electric energy is saved, and the control circuit is convenient to reduce power consumption.
6. The automatic impedance matcher has the advantages of simple, ingenious and reasonable structure, capability of meeting the requirement that a magnetostrictive transducer needs sinusoidal current for power supply, capability of solving the frequency drift phenomenon caused by the impedance characteristic of the transducer along with the change of environment and load, and capability of continuously and stably working in a resonance state under different environments, working conditions and loads, and capability of effectively increasing the output characteristics of the transducer such as output amplitude, output displacement and output acceleration. The work efficiency of the magnetostrictive transducer is remarkably improved (from lower than 40% to nearly 70%), and the magnetostrictive transducer can be widely applied to the fields of low-frequency underwater sound, ultrasound, active vibration control and the like.
Drawings
Fig. 1 is an overall configuration diagram of an automatic impedance matching device.
Fig. 2 is a block diagram of an impedance matching module. Wherein 1 represents a relay module I; 2 represents a relay module II; 3 represents a 5V direct current power supply; 4 represents a CBB capacitor; 5 represents a resistance R; and 6 represents a jumper cap H.
Fig. 3 is a block diagram of a signal acquisition module.
Fig. 4 is a circuit configuration diagram of the feedback module. Wherein 41 represents a differential amplifier, 42 represents a proportional amplifier, 43 represents a phase difference detection circuit, 44 represents a high-speed zero-crossing comparator a, 45 represents a high-speed zero-crossing comparator B, 46 represents a D flip-flop, and 47 represents an exclusive or gate.
Fig. 5 is a diagram of a control method of an automatic impedance matcher for a magnetostrictive transducer, where n is a zero-crossing number of a cycle of an input current of the transducer, θ is a phase difference between an input voltage and a current of the transducer, and Q is a lead-lag relationship between the input voltage and the current of the transducer.
FIG. 6 is a waveform diagram of the input voltage and current of a 20kHz magnetostrictive transducer after automatic impedance matching is completed. Where the square wave represents the transducer input voltage and the sine wave represents the transducer input current.
Detailed Description
The invention is described below with reference to the drawings, which do not limit the invention in any way.
As shown in fig. 1, an automatic impedance matcher for a magnetostrictive transducer comprises an impedance matching module, a signal acquisition module, a feedback module and a single-chip microcomputer control module;
the connection relationship is as follows: one end of the impedance matching module is connected with the output end of the power supply, and the other end of the impedance matching module is connected with one end of the magnetostrictive transducer; one end of the signal acquisition module is connected with the output end of the power supply, the other end of the signal acquisition module is connected with the other end of the magnetostrictive transducer, and the output end of the signal acquisition module is connected with one end of the feedback module; the other end of the feedback module is connected with one end of the singlechip control module; the output end of the single chip microcomputer control module is connected to the signal input end of the impedance matching module, and the PC is connected to the other end of the single chip microcomputer control module.
The impedance matching module is used for providing a matching capacitor between the driving power supply and the magnetostrictive transducer, completing tuning between the power supply and the transducer and eliminating reactive loss of the transducer, so that the working efficiency of the system is improved; the signal acquisition module is used for acquiring input voltage and input current signals of the transducer and transmitting the working state of the circuit to the feedback module in real time; the feedback module is used for amplifying the acquired voltage and current signals, then judging the voltage and current phase lead-lag relationship and the voltage and current phase difference, and transmitting the information obtained after the processing and the judgment to the single chip microcomputer control module; the singlechip control module is used for carrying out online control on the impedance matching module according to the information provided by the feedback module based on a preset matching program, automatically switching the matching capacitor in real time, selecting the optimal matching capacitance value and completing automatic impedance matching between the driving power supply and the transducer.
The impedance matching module structure is shown in fig. 2, and the module comprises two sets of 8-path 5V relay modules 1 and 2 with the optical coupling isolation function, a 5V direct-current power supply 3, 16 CBB capacitors 4 and 16 resistors 5 with the resistance value of 1k omega; the two sets of relay modules have the same structure and respectively comprise 8 relays connected in parallel; the DC + and DC-ports of each set of relay module are respectively connected to the positive pole c and the negative pole d of the 5V direct current power supply 3; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with a matched H jumper cap (high-level trigger jumper cap) 6; the input signal trigger port IN1-IN16 of each relay is respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normally open end NO1-NO16 of each relay is connected to the m end which is connected to the output end of the transducer driving power supply; the common end COM1-COM16 of each relay is correspondingly connected with one end of a CBB capacitor 4, the other end of each CBB capacitor 4 is connected with an n end, and the n end is connected with the input end of the transducer; the normally closed end NC1-NC16 of each relay is connected with one end of a 1k omega resistor 5, and the other end of the resistor 5 is connected with the other end of the CBB capacitor 4;
the relay modules 1 and 2 adopt 8 paths of 5V relay modules with an optical coupling isolation function of Telesky company, and the relay modules comprise SRD-05VDC-SL-C type power relays, small packaged optocouplers, high-power voltage-resistant triodes, red and blue signal indicator lamps, double-sided PCB boards and the like, are reasonable in layout and ingenious in structure, and are suitable for various single-chip microcomputer controls; the 5V direct current power supply 3 is an LRS-35-5 type direct current power supply of Mingmei corporation, and has stable output voltage and excellent performance; the 16 CBB capacitors 4 have capacitance values selected according to a specification table of 1 0.1 muF, 2 0.2 muF, 1 0.5 muF, 1 muF, 2 muF, 3 muF and 6 4 muF respectively, and 16 CBB capacitors are distributed in a row in order along the sequence from the relay 1 to the relay 16 of the relay module; the resistor 5 is a metal film resistor RJ series MF1/4W type, and has the advantages of good temperature characteristic, stable performance, high precision, simple and light structure;
the working principle of the impedance matching module shown in fig. 2 is that when the single chip outputs a high level, the relay is triggered, the common terminal COM of the relay is connected with the normally open terminal NO, and the CBB capacitor 4 is connected to the two terminals m and n to perform impedance matching between the driving power supply and the transducer; when the relay is not triggered, the common end COM of the relay is connected with the normally closed end NC, and two ends of the CBB capacitor 4 are connected with a 1k omega resistor 5 to form a loop, so that the function of capacitor discharging is achieved;
the structure of the signal acquisition module is shown in figure 3, and the module comprises three precision sampling resistors R31、R32、R33(ii) a The connection relation is a resistor R31One end of the impedance matching module is connected with the m end of the impedance matching module; resistance R31Another terminal of (1) and a resistor R32One end of the two ends are connected; resistance R32Another terminal of (1) and a resistor R33One end of the two ends are connected; resistance R33And to an input b2 of transducer b; resistance R31And is also connected to an output terminal a1 of power supply a; resistance R32One end of the voltage sampling terminal is also connected with a voltage sampling terminal SV 2; resistance R32The other end of the voltage sampling circuit is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; resistance R33One end of the current sampling terminal is also connected with a current sampling terminal SC 2; resistance R33And the other end thereof is also connected to a current sampling terminal SC 1. The voltage sampling terminal SV2 and the current sampling terminals SC1 and SC2 are connected to the input terminal of the feedback module. The n-terminal of the impedance matching block is connected to the other input terminal b1 of transducer b.
Wherein the resistance R is31、R32And R33The resistance values of the resistor are respectively 1M omega, 1k omega and 1 omega, RX70-3W type high-precision wire-wound sampling resistors are adopted, the power is 3W, the withstand voltage value is 1000V, the insulation voltage value is 1400V, the resistance value deviation is about 0.05%, the temperature coefficient is about +/-5- +/-10, and RX7The 0 type resistance has high stability and high reliability up to 0.1 and 1 multiplied by 10-5The insulating material has the characteristics of firm structure, high precision, good insulating property, small temperature coefficient and the like, and meets the design requirement.
The working principle of the signal acquisition module shown in fig. 3 is that two large resistors R31、R32After the voltage of the original circuit is divided, the obtained voltage is only one thousandth of the original voltage, so that the influence of a high-voltage signal generated by the main circuit on a rear-stage sampling circuit can be effectively avoided. The circuit can not only reflect the working state of the circuit in real time and accurately, but also ensure that the sampling circuit does not interfere with the acquired signal as far as possible and does not bring extra phase difference to the sampling signal. By collecting the resistance R32Voltage signals at two ends can finish voltage signal sampling of the transducer; by collecting the resistance R33The voltage signals at the two ends can indirectly complete the current signal sampling of the transducer.
The feedback module has a circuit structure as shown in fig. 4, and comprises a differential amplifier 41 adopting an LM324 type operational amplifier, a proportional amplifier 42 adopting an LM324 type operational amplifier, and a phase difference detection circuit 43;
the phase difference detection circuit 43 further includes two high-speed zero-crossing comparators a44 and B45 composed of LM339 chips, a D flip-flop 46 using 74LS74 chip, and an xor gate 47 using 74LS86 chip; the connection relationship of the modules is that the positive input end of the differential amplifier 41 is connected with the current sampling end SC2 of the signal acquisition module, the negative input end is connected with the current sampling end SC1, and the output end of the differential amplifier 41 is connected with the negative input end of a high-speed zero-crossing comparator A44 in the phase difference detection circuit 43; the input end of the proportional amplifier 42 is connected with the voltage sampling port SV2 of the signal acquisition module, and the output end of the proportional amplifier 42 is connected with the negative input end of the high-speed zero-crossing comparator B45 in the phase difference detection circuit 43; the output ends of the two high-speed zero-crossing comparators 44 and 45 are respectively connected to a D port and a CLK port of the D flip-flop 46, and a set input S and a reset input R of the D flip-flop 46 are both grounded; the outputs of the two high speed zero crossing comparators 44 and 45 are coupled to the inputs of an exclusive or gate 47, respectively.
The LM324 operational amplification circuit in the feedback module has the characteristics of wide power voltage range, low static power consumption and low price, and can amplify very weak voltage and current signals obtained by sampling on the premise of saving cost; the LM339 chip is a common chip in the voltage comparators, four independent voltage comparators are integrated in the LM339 chip, and zero-crossing detection of voltage signals and current signals can be finished respectively.
The working principle of the feedback module shown in fig. 4 is that the differential amplifier 41 and the proportional amplifier 42 respectively amplify the current and voltage signals acquired by the signal acquisition module to obtain an analog signal I, U; then the amplified analog signal I, U is respectively sent to a zero-crossing comparator A44 and a zero-crossing comparator B45, and a digital signal Phase-I, Phase-U with the same frequency as the amplified analog signal is obtained; then, the digital signal Phase-I, Phase-U is sent to the D terminal and the CLK terminal of the D flip-flop 46, respectively, because the S terminal and the R terminal of the D flip-flop 46 are both grounded (same as low level), so the rising edge of CLK triggers the level of the Q terminal, Q outputs the same logic value as the D terminal, the output Q represents the voltage-current Phase relationship, Q is 0 (low level) represents that the voltage Phase leads the current, Q is 1 (high level) represents that the voltage Phase lags the current; the digital signal Phase-I, Phase-U is sent to the xor gate 47, and its output is the voltage-current Phase difference θ.
The single-chip microcomputer control module selects 89S51 of an ATMEL89 series single-chip microcomputer compatible with all Intel 8031 instruction systems as a main control chip, and 89S51 is a low-power-consumption and high-performance CMOS8 bit single-chip microcomputer produced by American ATMEL company. The high-density nonvolatile memory is produced by adopting a high-density nonvolatile memory technology, is compatible with a standard 8051 instruction system and pins, and is very convenient to develop. The AT89S51 comprises 32 external bidirectional input/output (I/O) port lines, and the relay can be started and stopped by outputting a level signal, so that the switch is controlled to complete the function of the control circuit. The Serial Communication Interface (SCI) is connected with a serial communication interface of an upper computer (PC) through an RS232 type data transmission line, and data transmission between the AT89S51 and the upper computer is realized through setting a communication protocol between the AT89S51 and the upper computer.
The control method of the magnetostrictive transducer automatic impedance matcher is shown in fig. 5, and comprises the following steps:
the first step, the device is powered on and started, the system is initialized, and then the second step is carried out;
secondly, after delaying for 10ms, the signal acquisition module performs voltage sampling and current sampling on the transducer;
thirdly, the single chip microcomputer judges whether the zero-crossing frequency n of current in one period is greater than 3, if yes, two sets of 8-path relay modules with the optical coupling isolation function in the impedance matching module are controlled, the matching capacitor is increased according to the Step length of Step0 being 1 mu F by controlling the starting and stopping of the relay, and then the third Step is returned to continue judging; if n is greater than 3, executing the fourth step;
step four, judging whether the phase difference theta output by the feedback module is more than 50 degrees, if yes, making Step equal to 1 mu F, namely, a large Step length, and jumping to the Step seven; if not, executing the fifth step;
fifthly, judging whether the phase difference theta output by the feedback module is more than 20 degrees, if yes, making Step equal to 0.2 mu F, namely, the Step length, and jumping to the seventh Step; if not, executing the sixth step;
sixthly, judging whether the phase difference theta output by the feedback module is more than 5 degrees, if yes, making Step be 0.1 mu F, namely, a small Step length, and executing the seventh Step; if theta is greater than 5 degrees, the automatic impedance matching is finished once, and the operation is finished;
and seventhly, judging whether the phase relation Q of the voltage and the current output by the feedback module is 0, and controlling two sets of relays in the relay module with the optical coupling isolation function in the impedance matching module according to a judgment result: if Q is equal to 0, increasing the matching capacitor according to the Step value of Step by controlling the starting and stopping of the relay, and then jumping back to the second Step; if Q is not equal to 0, reducing the matching capacitance according to the Step value of Step by controlling the starting and stopping of the relay, and then jumping back to the second Step; and continuing to execute the automatic matching process until the theta is not over 5 degrees in the sixth step, and ending the operation.
In the system initialization process in the first step, the initial capacitance C is made to be 0; the 10ms delay sampling time is used for enabling the measured data to timely and truly reflect the working state of the circuit after one-time adjustment, and ensuring the smoothness of the whole automatic impedance matching program; the third step, the zero-crossing times n of the current in one period can be directly obtained by the single chip microcomputer according to an output pulse signal Phase-I of a zero-crossing comparator A44 in the feedback module, when n is greater than 3, the current is in an underdamping state of an RLC series circuit, and the voltage and current phases cannot be compared, so that the matching capacitance value is too small at the moment, and the matching capacitance needs to be increased by large step length to ensure the subsequent steps; if theta is greater than 5 degrees and is not true in the fifth step, the voltage and the current of the transducer are close to the same phase, the reactance of the transducer is approximately 0, and the transducer is considered to work in a resonance state; step four, Step five and Step six, selecting three Step sizes according to different sizes of input voltage and current phase difference theta of the transducer, wherein when theta is larger than 50 degrees, the Step size is large 1 mu F, when theta is larger than 20 degrees and smaller than 50 degrees, the Step size is medium 0.2 mu F, and when theta is larger than 5 degrees and smaller than 20 degrees, the Step size is small 0.1 mu F, so that the automatic impedance matching speed can be effectively improved; and if the phase relation Q of the input voltage and the current of the transducer is 0, the voltage phase leads the current and the matching capacitance needs to be increased, and if Q is 0, the voltage phase lags the current and the matching capacitance needs to be reduced.
The operation principle of the control method of the magnetostrictive transducer automatic impedance matcher shown in fig. 5 is that the single chip microcomputer selects to increase or decrease the matching capacitance value according to the leading-lagging relation of the input voltage and the current phase of the transducer, three different step values are adopted according to the phase difference of the input voltage and the current of the transducer, the value of the matching capacitance is adjusted on line in real time, the phase difference of the voltage and the current is locked to be approximately 0 quickly, and the automatic impedance matching function is completed. After one-time automatic impedance matching is completed, the resonance frequency of the transducer can shift due to changes of ambient temperature, load and the like, and the transducer can not work in a resonance state any more. Therefore, during the operation of the transducer, an automatic impedance matching program is called every 0.5S to ensure that the transducer continuously and stably operates in a resonance state.
As shown in fig. 6, the automatic impedance matcher is used for a 20KHz magnetostrictive transducer, and after automatic impedance matching is completed, experimental tests are performed on input voltage and current of the transducer to obtain a waveform diagram. Wherein the square wave represents the input voltage and the sine wave represents the input current, and the peak value of the input current reaches 5A when the input voltage is about 30V. As can be seen from the figure, after the matching of the automatic impedance matcher is completed, the input current of the transducer is in a standard sine waveform, and the input voltage and the input current of the transducer are in the same phase. Experiments verify that the automatic impedance matcher can quickly complete automatic impedance matching between a driving power supply and a magnetostrictive transducer, meet the requirement that the magnetostrictive transducer needs sinusoidal current for power supply, ensure that the transducer continuously and stably works in a resonance state, and effectively improve the working efficiency of the transducer.
The operation process of the automatic impedance matcher is as follows:
in the working process of the circuit, the signal acquisition module acquires voltage and current signals in real time between the driving power supply and the magnetostrictive transducer and sends the acquired signals to the feedback module; the feedback module firstly amplifies the acquired signals, then converts the analog signals obtained by amplification into digital signals, and then judges and processes the digital signals to obtain the phase difference between voltage and current and the advance or lag relationship between voltage and current; and transmitting an output signal obtained after judgment and processing of the feedback module into the single chip microcomputer, and controlling a relay in the impedance matching module by the single chip microcomputer as shown in figure 5 to complete automatic impedance matching of the magnetostrictive transducer. The capacitance value of the CBB capacitors in the impedance matching module, the number of the CBB capacitors, and the initial value of the matching capacitors, the phase difference threshold value, and the step length in fig. 5 can be appropriately adjusted according to actual conditions. During operation of the automatic impedance matcher, a digital input display circuit (PC) may monitor the frequency, phase difference, phase relationship, etc. for display.
The design of the invention is a closed circuit, the whole circuit part can be concentrated on a PCB printed circuit board, and the integration level of the system is higher after the design is minimized. All the elements and the shells are supplied in the market, the quality is reliable, the structure is ingenious and reasonable, and the manufacturing cost is low.
The invention is not the best known technology.
Claims (3)
1. An automatic impedance matcher for a magnetostrictive transducer is characterized by comprising an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module;
the connection relationship is as follows: one end of the impedance matching module is connected with the output end of the power supply, and the other end of the impedance matching module is connected with one end of the magnetostrictive transducer; one end of the signal acquisition module is connected with the output end of the power supply, the other end of the signal acquisition module is connected with the other end of the magnetostrictive transducer, and the output end of the signal acquisition module is connected with one end of the feedback module; the other end of the feedback module is connected with one end of the singlechip control module; the output end of the singlechip control module is connected to the signal input end of the impedance matching module, and the PC is connected to the other end of the singlechip control module;
the impedance matching module comprises two sets of 8 paths of relay modules with 5V band optical coupling isolation functions, a 5V direct-current power supply, 16 CBB capacitors and 16 resistors with the resistance value of 1k Ω; the two sets of relay modules have the same structure and respectively comprise 8 relays connected in parallel; the DC + and DC-ports of each set of relay module are respectively connected to the anode c and the cathode d of a 5V direct-current power supply; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with a matched H jumper cap; the input signal trigger port IN1-IN16 of each relay is respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normally open end NO1-NO16 of each relay is connected to the m end which is connected to the output end of the transducer driving power supply; the common end COM1-COM16 of each relay is correspondingly connected with one end of a CBB capacitor, the other end of each CBB capacitor is connected with an n end, and the n end is connected with the input end of the transducer; the normally closed end NC1-NC16 of each relay is connected with one end of a resistor of 1k Ω, and the other end of each resistor is connected to the other end of the CBB capacitor;
the signal acquisition module comprises three precision sampling resistors R31、R32、R33(ii) a The connection relation is a resistor R31One end of (A)The m end of the impedance matching module is connected with the m end of the impedance matching module; resistance R31Another terminal of (1) and a resistor R32One end of the two ends are connected; resistance R32Another terminal of (1) and a resistor R33One end of the two ends are connected; resistance R33And to an input b2 of transducer b; resistance R31And is also connected to an output terminal a1 of power supply a; resistance R32One end of the voltage sampling terminal is also connected with a voltage sampling terminal SV 2; resistance R32The other end of the voltage sampling circuit is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; resistance R33One end of the current sampling terminal is also connected with a current sampling terminal SC 2; resistance R33The other end of the current sampling terminal is also connected with a current sampling terminal SC 1; the n-terminal of the impedance matching block is connected to the other input terminal b1 of transducer b.
2. The automatic impedance matcher for magnetostrictive transducer as claimed in claim 1, characterized in that the feedback module circuit comprises a differential amplifier using LM324 type operational amplifier, a proportional amplifier using LM324 type operational amplifier and a phase difference detection circuit;
the phase difference detection circuit comprises two high-speed zero-crossing comparators consisting of LM339 chips, a D flip-flop adopting a 74LS74 chip and an exclusive-OR gate adopting a 74LS86 chip; the connection relation of the modules is that the positive input end of the differential amplifier is connected with the current sampling end SC2 of the signal acquisition module, the negative input end of the differential amplifier is connected with the current sampling end SC1, and the output end of the differential amplifier is connected with the negative input end of a high-speed zero-crossing comparator A in the phase difference detection circuit; the input end of the proportional amplifier is connected with a voltage sampling port SV2 of the signal acquisition module, and the output end of the proportional amplifier is connected with the negative input end of a high-speed zero-crossing comparator B in the phase difference detection circuit; the output ends of the two high-speed zero-crossing comparators are respectively connected to a D port and a CLK port of the D trigger, and a set input S and a reset input R of the D trigger are both grounded; the output ends of the two high-speed zero-crossing comparators are respectively connected to the input ends of the exclusive-or gates.
3. The method for controlling an automatic impedance matcher for a magnetostrictive transducer according to claim 1, comprising the steps of:
the first step, the device is powered on and started, the system is initialized, and then the second step is carried out;
secondly, after delaying for 10ms, the signal acquisition module performs voltage sampling and current sampling on the transducer;
thirdly, the singlechip judges the zero crossing times of the current in one periodn>If the impedance matching module is established, controlling two sets of 8-path relay modules with the optical coupling isolation function in the impedance matching module, increasing the matching capacitance according to the Step length of Step0=1 μ F by controlling the starting and stopping of the relay, and returning to the third Step to continue judging; n is>If 3 is not true, executing the fourth step;
fourthly, judging the phase difference output by the feedback moduleθ>If 50 degrees is established, if the 50 degrees is established, Step =1 μ F, namely the Step length is large, and then the seventh Step is skipped; if not, executing the fifth step;
fifthly, judging the phase difference output by the feedback moduleθ>If 20 degrees is established, if the 20 degrees is established, Step =0.2 μ F, namely the Step length is determined, and the seventh Step is executed again; if not, executing the sixth step;
sixthly, judging the phase difference output by the feedback moduleθ>If 5 degrees is true, if true, Step =0.1 μ F, namely, the Step length is small, and the seventh Step is executed;θ>if the 5 degrees are not established, the automatic impedance matching is finished once, and the operation is finished;
seventhly, judging the phase relation between the voltage and the current output by the feedback moduleQIf the signal is true, controlling relays in two sets of 8 relay modules with optical coupling isolation functions in the impedance matching module according to a judgment result:Qif the =0 is established, increasing the matching capacitor according to the Step value of Step by controlling the starting and stopping of the relay, and then jumping back to the second Step;Qif not, reducing the matching capacitor according to the Step value of Step by controlling the starting and stopping of the relay and jumping back to the second Step; continuing to execute the automatic matching process until the sixth stepθ>The 5 ° is not established and the run is finished.
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| CN111504444A (en) * | 2020-04-22 | 2020-08-07 | 清华大学 | Device and method for determining resonant frequency of giant magnetostrictive ultrasonic transducer |
| CN111766552A (en) * | 2020-07-06 | 2020-10-13 | 河北工业大学 | Automatic impedance matching device and method for magnetic characteristic measurement system |
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