CN110646673B - Automatic impedance matcher of magnetostriction transducer - Google Patents
Automatic impedance matcher of magnetostriction transducer Download PDFInfo
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- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
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Abstract
The invention relates to an automatic impedance matcher of 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 5V optocoupler isolation function, a 5V direct current power supply, 16 CBB matching capacitors and 16 resistors with resistance value of 1kΩ; 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 relay module are respectively connected to the positive electrode c and the negative electrode d of the 5V direct current power supply; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with an H jumper cap matched with the high-low level trigger selection ends S1-S16. The invention can make the transducer continuously and stably work in resonance state under different environments, working conditions and loads, and remarkably improves the working efficiency of the transducer.
Description
Technical Field
The present invention relates to an impedance matcher, and more particularly, to an automatic impedance matcher for a magnetostrictive transducer. The dynamic automatic impedance matching between the power supply and the magnetostrictive transducer is realized by adopting an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module.
Background
Magnetostrictive transducers are electromagnetic mechanical devices that utilize magnetostrictive materials to convert energy, and are devices that convert energy of one form into energy of another. The method is widely applied in the fields of underwater sound, ultrasound, active vibration control and the like.
Impedance matching between the magnetostrictive transducer and the power supply directly affects the working efficiency of the magnetostrictive transducer. In recent years, the manufacturing process of the magnetostrictive transducer is mature, but the development of intelligent impedance matching is relatively slow, so that the application of the magnetostrictive transducer is restricted.
In order to improve the output power, energy conversion efficiency, and other performances of the magnetostrictive transducer, impedance matching needs to be performed between the transducer and the power supply. The magnetostriction transducer is in resistance and inductance, can be equivalently connected with a resistor and an inductor in series, and is subjected to impedance matching according to circuit knowledge, so that the inductance of the magnetostriction transducer can be eliminated, and the transducer can work in a resonance state, thereby improving the working performance. Currently, the main impedance matching modes include two main types of 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 required to be matched is calculated by a formula in combination with the resonance frequency, so that the matching is completed. Through static matching, reactive power of the transducer can be eliminated, and the transducer can work in a resonance state, so that 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 are changed due to the changes of the environment, the temperature, the load and the like, so that the phenomenon of frequency drift is brought. At this point the applied matching capacitance will no longer meet the requirements and the transducer will no longer operate at resonance.
Dynamic matching mainly includes a variable capacitance matching method and a frequency tracking method. The variable capacitance matching method is based on the principle that the control circuit controls the rotation of the driving motor according to the detected voltage and current amplitude, phase and other information, so as to regulate the value of the variable capacitor and complete impedance matching. 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 supply according to information such as the amplitude, phase and the like of the detected voltage and current. On the premise of ensuring that the parameters of the matching capacitor determined by static matching are not changed, the output frequency of a driving power supply is changed along with the change of the resonant frequency of the transducer, and the dynamic impedance matching is indirectly completed. The method has complex structure and elements, needs static matching as an aid, and is suitable for occasions where the output frequency needs to be changed.
Disclosure of Invention
Aiming at the defects of impedance matching, the invention aims to provide an automatic impedance matcher of a magnetostrictive transducer with high speed, wide range and high precision and an implementation method thereof. The automatic impedance matcher selects the signal acquisition module consisting of the high-precision sampling resistor to acquire the circuit signal, so that the extra phase difference caused by a sampling circuit is effectively avoided; two sets of 8-path relay modules with optical coupling isolation function are selected, and each relay is connected with one capacitor. The singlechip is used for controlling the relay, and on the premise of ensuring that the output frequency of the driving power supply is unchanged, the matching capacitance value is adjusted in a step-variable mode to lock the input voltage and current of the transducer to the same phase state, 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 remarkably improved.
The technical scheme of the invention is as follows:
The automatic impedance matcher of the magnetostrictive transducer comprises an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module;
The connection relation 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 meanwhile, 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 optocoupler isolation function, a 5V direct current power supply, 16 CBB capacitors and 16 resistors with resistance value of 1kΩ; 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 relay module are respectively connected to the positive electrode c and the negative electrode d of the 5V direct current power supply; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with an H jumper cap matched with the high-low level trigger selection ends S1-S16; the input signal trigger ports IN1-IN16 of each relay are respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normal open ends NO1-NO16 of each relay are connected to an m end, and the m end is connected to the output end of the transducer driving power supply; the common terminals COM1-COM16 of each relay are correspondingly connected with one end of a CBB capacitor, the other end of each CBB capacitor is connected with an n-terminal, and the n-terminal is connected with the input end of the transducer; the normally-closed ends NC1-NC16 of each relay are connected with one end of a 1k omega resistor, and the other end of each resistor is connected with the other end of the CBB capacitor;
the signal acquisition module comprises three precise sampling resistors R 31、R32、R33; one end of the resistor R 31 is connected with the m end of the impedance matching module; the other end of the resistor R 31 is connected with one end of the resistor R 32; the other end of the resistor R 32 is connected with one end of the resistor R 33; the other end of the resistor R 33 is connected with one input end b2 of the transducer b; one end of the resistor R 31 is also connected with one output end a1 of the power supply a; one end of the resistor R 32 is also connected with a voltage sampling end SV 2; the other end of the resistor R 32 is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; one end of the resistor R 33 is also connected with the current sampling end SC 2; the other end of the resistor R 33 is also connected with a current sampling end SC 1; the n-terminal of the impedance matching module is connected to the other input terminal b1 of the 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 composed of LM339 chips, a D trigger adopting a 74LS74 chip and an exclusive-OR gate adopting a 74LS86 chip; the connection relation of the module 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 the 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 electrode input end of the 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 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 automatic impedance matcher of the magnetostrictive transducer comprises the following steps:
the method comprises the steps of firstly, powering on the device, initializing a system, and then carrying out a second step;
step two, after delaying for 10ms, the signal acquisition module samples the voltage and the current of the transducer;
Thirdly, judging whether the zero crossing frequency n >3 of the current in one period is met or not by the singlechip, controlling two sets of 8 relay modules with the optocoupler isolation function in the impedance matching module if the zero crossing frequency n >3 of the current in one period is met, increasing the matching capacitance according to the Step length of Step0 = 1 mu F by controlling the start and stop of the relay, and returning to the third Step for continuous judgment; executing the fourth step if n >3 is not true;
Fourth, judging whether the phase difference theta >50 DEG output by the feedback module is true, if so, enabling step=1μF, namely, a large Step length, and then jumping to a seventh Step; executing a fifth step if the first step is not true;
Fifthly, judging whether the phase difference theta >20 degrees output by the feedback module is true, if so, enabling step=0.2 mu F, namely, a middle Step length, and then jumping to a seventh Step; if not, executing a sixth step;
A sixth Step of judging whether the phase difference theta >5 DEG output by the feedback module is true, and if so, making step=0.1 mu F, namely a small Step length, and executing a seventh Step; if theta is larger than 5 DEG, the automatic impedance matching is finished, and the operation is finished;
Seventh, judging whether the phase relation Q=0 of the voltage and the current output by the feedback module is met, and controlling relays in two sets of 8 paths of relay modules with the optocoupler isolation function in the impedance matching module according to a judging result: if Q=0 is met, the matching capacitance is increased according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; if Q=0 is not met, the matching capacitance is reduced according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; and continuing to execute the automatic matching flow until theta >5 DEG is not established in the sixth step, and ending the operation.
The beneficial effects of the invention are as follows:
1. The automatic impedance matcher of the magnetostrictive transducer has high matching precision (0.1 mu F), wide matching range (0.1-39.0 mu F) 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 singlechip control module on line, and the singlechip control module performs start-stop control on the relay according to a matching program to realize real-time automatic switching of the series capacitor, select the optimal matching capacitor and complete automatic impedance matching of the magnetostrictive transducer. The automatic impedance matcher can adjust the input voltage and current of the transducer to the same phase state on the premise of ensuring that the output frequency of the driving power supply is unchanged, so that a good sinusoidal 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 adopts a resistance sampling method to sample voltage and current signals, avoids extra phase difference brought by a sampling circuit, and improves the accuracy of automatic impedance matching by approximately 20 percent compared with other sampling methods.
4. The automatic matching program of the invention adopts a variable step size method for matching. Three step sizes with different sizes are selected according to the phase difference, so that the automatic impedance matching time of approximately 30% can be effectively shortened, and the matching efficiency is improved.
5. The 89S51 main control chip adopted by the control module is an 8-bit main control chip, has stable performance and low cost, and ensures the processing speed and the processing precision of instructions while saving the cost; the Flash memory is contained, 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 an excellent reaction mechanism is provided for sudden damage of an external power supply; the volume is small, so that the volume of the product is minimized; by adopting a static clock mode, electric energy is saved, and a control circuit is convenient to reduce power consumption.
6. The automatic impedance matcher has a simple, ingenious and reasonable structure, meets the requirement that the magnetostrictive transducer needs sinusoidal current for power supply, and can solve the frequency drift phenomenon caused by the change of the impedance characteristic of the transducer along with the environment and the load, so that the transducer can continuously and stably work in a resonance state under different environments, working conditions and loads, and the output characteristics such as the output amplitude, the output displacement and the output acceleration of the transducer are effectively increased. The working efficiency of the magnetostrictive transducer is obviously improved (from 40% to 70%) so that the transducer can be widely applied to the fields of low-frequency underwater sound, ultrasound, active vibration control and the like.
Drawings
Fig. 1 is a diagram of an overall structure of an automatic impedance matcher.
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 CBB capacitance; 5 represents a resistor 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 denotes a differential amplifier, 42 denotes a proportional amplifier, 43 denotes a phase difference detection circuit, 44 denotes a high-speed zero-crossing comparator a,45 denotes a high-speed zero-crossing comparator B,46 denotes a D flip-flop, and 47 denotes an exclusive or gate.
Fig. 5 is a diagram of a control method of the magnetostrictive transducer automatic impedance matcher, where n is the number of zero crossings of a period of the input current of the transducer, θ is the magnitude of the phase difference between the input voltage and the current of the transducer, and Q is the lead-lag relationship between the input voltage and the phase of the current of the transducer.
FIG. 6 is a graph of input voltage and current waveforms of the 20kHz magnetostrictive transducer after automatic impedance matching is completed. Where square waves represent the transducer input voltage and sine waves represent the transducer input current.
Detailed Description
The invention is described below with reference to the accompanying drawings, which do not limit the invention in any way.
As shown in fig. 1, the automatic impedance matcher of the magnetostrictive transducer comprises an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module;
The connection relation 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 meanwhile, 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 is used for providing matching capacitance between the driving power supply and the magnetostrictive transducer, completing tuning between the power supply and the transducer, and eliminating reactive power loss of the transducer, thereby improving the working efficiency of the system; 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, judging the voltage and current phase lead-lag relation and the voltage and current phase difference, and transmitting the information obtained after the processing and the judgment to the singlechip control module; the singlechip control module is used for carrying out on-line 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 capacitor value and completing the automatic impedance matching between the driving power supply and the transducer.
The impedance matching module structure is shown in figure 2, and the module comprises two sets of 8 paths of relay modules 1 and 2 with an optical coupling isolation function and 5V direct current power supply 3, 16 CBB capacitors 4 and 16 resistors 5 with resistance value of 1kΩ; 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 relay module are respectively connected to the positive electrode c and the negative electrode 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 an H jumper cap (high-level trigger jumper cap) 6 matched with the high-low level trigger selection ends S1-S16; the input signal trigger ports IN1-IN16 of each relay are respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normal open ends NO1-NO16 of each relay are connected to an m end, and the m end is connected to the output end of the transducer driving power supply; the public terminals COM1-COM16 of each relay are correspondingly connected with one end of a CBB capacitor 4, the other end of each CBB capacitor 4 is connected with an n-terminal, and the n-terminal is connected with the input end of the transducer; the normally-closed ends NC1-NC16 of each relay are 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 are 8 paths of relay modules with 5V optocoupler isolation functions of telesky company, and are composed of SRD-05VDC-SL-C 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, ingenious in structure and suitable for control of various singlechips; the 5V direct current power supply 3 is an LRS-35-5 direct current power supply of Mingwei company, and has stable output voltage and excellent performance; the capacitance values of the 16 CBB capacitors 4 selected according to the specification table are respectively 1 0.1 mu F, 2 0.2 mu F,1 0.5 mu F,1 mu F, 2 mu F, 3 mu F, 64 mu F and 16 CBB capacitors are orderly distributed in a row along the sequence from the relay module relay 1 to the relay 16; the resistor 5 is a metal film resistor RJ system MF1/4W type, and has the advantages of good temperature characteristic, stable performance, high precision and simple and light structure;
the working principle of the impedance matching module shown in fig. 2 is that when the singlechip outputs a high level, the relay is triggered, the public end COM of the relay is communicated with the normally open end NO, and the CBB capacitor 4 is connected to the two ends m and n to perform impedance matching between the driving power supply and the energy converter; when the relay is not triggered, the public 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 resistor 5 with the impedance of 1kΩ to form a loop, so that the capacitor discharging function is realized;
The structure of the signal acquisition module is shown in fig. 3, and the module comprises three precise sampling resistors R 31、R32、R33; one end of the resistor R 31 is connected with the m end of the impedance matching module; the other end of the resistor R 31 is connected with one end of the resistor R 32; the other end of the resistor R 32 is connected with one end of the resistor R 33; the other end of the resistor R 33 is connected with one input end b2 of the transducer b; one end of the resistor R 31 is also connected with one output end a1 of the power supply a; one end of the resistor R 32 is also connected with a voltage sampling end SV 2; the other end of the resistor R 32 is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; one end of the resistor R 33 is also connected with the current sampling end SC 2; the other end of the resistor R 33 is also connected to the current sampling terminal SC 1. The voltage sampling terminal SV2 and the current sampling terminals SC1, SC2 are connected to the input terminal of the feedback module. The n-terminal of the impedance matching module is connected to the other input terminal b1 of the transducer b.
The resistors R 31、R32 and R 33 are respectively 1MΩ, 1kΩ and 1 Ω, RX70-3W type high-precision wire-wound sampling resistor is adopted, the power is 3W, the withstand voltage is 1000V, the insulation voltage is 1400V, the resistance deviation is about 0.05%, the temperature coefficient is about + -5 + -10, the RX70 type resistor has high stability and high reliability grade up to 0.1 and 1X 10 -5/h, and the resistor has the characteristics of firm structure, high precision, good insulativity, small temperature coefficient and the like, and meets the design requirements.
The working principle of the signal acquisition module shown in fig. 3 is that after the voltage of the original circuit is divided by two large resistors R 31、R32, 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 the later-stage sampling circuit can be effectively avoided. The working state of the circuit can be accurately reflected in real time, the sampling circuit can be guaranteed not to interfere the acquired signal as much as possible, and no extra phase difference is brought to the sampled signal. The voltage signal sampling of the transducer can be completed by collecting the voltage signals at two ends of the resistor R 32; the current signal sampling of the transducer can be indirectly completed through collecting the voltage signals at two ends of the resistor R 33.
The circuit structure of the feedback module is shown in fig. 4, and the module comprises a differential amplifier 41 adopting an LM324 type operational amplifier, a proportional amplifier 42 adopting the LM324 type operational amplifier and a phase difference detection circuit 43;
The phase difference detection circuit 43 further comprises two high-speed zero-crossing comparators A44 and B45 composed of LM339 chips, a D trigger 46 adopting a 74LS74 chip and an exclusive OR gate 47 adopting a 74LS86 chip; the connection relation of the module 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 the 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 electrode 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 the D port and the CLK port of the D flip-flop 46, and the set input S and the reset input R of the D flip-flop 46 are grounded; the outputs of the two high-speed zero-crossing comparators 44 and 45 are connected to the inputs of an exclusive-or gate 47, respectively.
The LM324 operational amplifier circuit in the feedback module has the characteristics of wide power supply voltage range, small 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 comparator, four independent voltage comparators are integrated inside the LM339 chip, and zero crossing detection of voltage and current signals can be respectively completed.
The feedback module shown in fig. 4 works in the principle that the differential amplifier 41 and the proportional amplifier 42 amplify the current and voltage signals acquired by the signal acquisition module to obtain analog signals I, U; the amplified analog signal I, U is respectively sent to a zero-crossing comparator A44 and a zero-crossing comparator B45 to obtain a digital signal Phase-I, phase-U with the same frequency; then the digital signal Phase-I, phase-U is sent to the D terminal and 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 (both are low level), the rising edge of CLK triggers the Q terminal level, Q outputs the same logic value as the D terminal, Q is the output Q indicates the voltage-current Phase relationship, Q is 0 (low level) indicates that the voltage Phase is advanced to the current, Q is 1 (high level) indicates that the voltage Phase is retarded to the current; the digital signal Phase-I, phase-U is fed into the exclusive or gate 47, whose output is the magnitude of the voltage-current Phase difference θ.
The singlechip control module selects 89S51 of ATMEL89 series singlechips compatible with all Intel 8031 instruction systems as a main control chip, and 89S51 is a low-power-consumption high-performance CMOS 8-bit singlechip produced by ATMEL company in the United states. The high-density nonvolatile memory technology is adopted for production, and is compatible with a standard 8051 instruction system and pins, thereby being extremely convenient for development. The AT89S51 contains 32 external bidirectional input/output (I/O) ports, and can start and stop the relay through outputting level signals so as to control the switch to complete the function of a control circuit. The Serial Communication Interface (SCI) is connected with the serial communication interface of the upper computer (PC) through an RS232 data transmission line, and data transmission between the AT89S51 and the upper computer is realized through setting a communication protocol between the two.
The control method of the automatic impedance matcher of the magnetostrictive transducer is shown in fig. 5, and comprises the following steps:
the method comprises the steps of firstly, powering on the device, initializing a system, and then carrying out a second step;
step two, after delaying for 10ms, the signal acquisition module samples the voltage and the current of the transducer;
Thirdly, judging whether the zero crossing frequency n >3 of the current in one period is met or not by the singlechip, controlling two sets of 8 relay modules with the optocoupler isolation function in the impedance matching module if the zero crossing frequency n >3 of the current in one period is met, increasing the matching capacitance according to the Step length of Step0 = 1 mu F by controlling the start and stop of the relay, and returning to the third Step for continuous judgment; executing the fourth step if n >3 is not true;
Fourth, judging whether the phase difference theta >50 DEG output by the feedback module is true, if so, enabling step=1μF, namely, a large Step length, and then jumping to a seventh Step; executing a fifth step if the first step is not true;
Fifthly, judging whether the phase difference theta >20 degrees output by the feedback module is true, if so, enabling step=0.2 mu F, namely, a middle Step length, and then jumping to a seventh Step; if not, executing a sixth step;
A sixth Step of judging whether the phase difference theta >5 DEG output by the feedback module is true, and if so, making step=0.1 mu F, namely a small Step length, and executing a seventh Step; if theta is larger than 5 DEG, the automatic impedance matching is finished, and the operation is finished;
Seventh, judging whether the phase relation Q=0 of the voltage and the current output by the feedback module is met, and controlling relays in two sets of 8 paths of relay modules with the optocoupler isolation function in the impedance matching module according to a judging result: if Q=0 is met, the matching capacitance is increased according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; if Q=0 is not met, the matching capacitance is reduced according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; and continuing to execute the automatic matching flow until theta >5 DEG is not established in the sixth step, and ending the operation.
In the system initialization process in the first step, the initial capacitance c=0; the time delay sampling time of 10ms in the second step is used for enabling measured data to timely and truly reflect the working state of a circuit after one-time adjustment, and ensuring the smoothness of the whole automatic impedance matching program; the zero crossing times n of the current in one period in the third step can be directly obtained by using the singlechip according to the output pulse signal Phase-I of the zero crossing comparator A44 in the feedback module, and when n is more than 3, the comparison of voltage and current phases cannot be performed in an underdamped state of the RLC series circuit, which indicates that the matching capacitance value is too small at the moment, and the matching capacitance needs to be increased by adopting a large step size so as to ensure the proceeding of the subsequent steps; the theta of the fifth step is not equal to 5 degrees, which means that 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 at the moment; step values Step in the fourth Step, the fifth Step and the sixth Step are different according to the input voltage and the current phase difference theta of the transducer, three Step sizes with different sizes are selected, wherein when theta is more than 50 degrees, a large Step size 1 mu F is selected, when theta is more than 20 degrees and less than or equal to 50 degrees, a medium Step size 0.2 mu F is selected, when theta is more than 5 degrees and less than or equal to 20 degrees, a small Step size 0.1 mu F is selected, and the automatic impedance matching speed can be effectively improved; the phase relation q=0 of the input voltage and the current of the transducer in the seventh step is satisfied, which means that the voltage phase is advanced to the current, the matching capacitance needs to be increased, and q=0 is not satisfied, which means that the voltage phase is retarded to the current, and the matching capacitance needs to be reduced.
The working principle of the control method of the magnetostrictive transducer automatic impedance matcher shown in fig. 5 is that the singlechip selects to increase or decrease the matching capacitance value according to the phase lead-lag relation of the input voltage and the current 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, and the automatic impedance matching function is completed. After one automatic impedance matching is completed, the resonant frequency of the transducer will drift due to changes in ambient temperature, load, etc., and the transducer will no longer operate in a resonant state. Therefore, in the working process of the transducer, an automatic impedance matching program is called every 0.5S, so that the transducer is ensured to continuously and stably work 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 the input voltage and current of the transducer, and a waveform diagram is obtained. Where the square wave represents the input voltage and the sine wave represents the input current, the peak value of the input current reaches 5A at an input voltage of about 30V. 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 prove that the automatic impedance matcher can rapidly complete automatic impedance matching between a driving power supply and the magnetostrictive transducer, meets the requirement that the magnetostrictive transducer needs sinusoidal current to supply power, can ensure that the transducer continuously and stably works in a resonance state, and effectively improves 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 into the feedback module; the feedback module firstly amplifies the acquired signals, then converts analog signals obtained by the amplification into digital signals, and then judges the digital signals to obtain the voltage and current phase difference magnitude and the voltage and current lead or lag relation; and transmitting the output signal obtained after the judgment and processing of the feedback module to a singlechip, and controlling a relay in the impedance matching module by the singlechip as shown in figure 5 to complete the automatic impedance matching of the magnetostrictive transducer. The capacitance value of the CBB capacitors in the impedance matching module, the number of CBB capacitors, and the initial value of the matching capacitors, the phase difference threshold value and the step length in fig. 5 can be properly adjusted according to practical situations. During operation of the automatic impedance matcher, a digital input display circuit (PC) may display and monitor frequency, phase difference, phase relationship, etc.
The invention is designed as a closed circuit, the whole circuit part can be concentrated on one PCB printed circuit board, and the system has higher integration level after the design is minimized. All the elements and the shells are supplied in the market, and the device has reliable quality, ingenious and reasonable structure and low manufacturing cost.
The invention is not a matter of the known technology.
Claims (2)
1. The automatic impedance matcher for the magnetostrictive transducer is characterized by comprising an impedance matching module, a signal acquisition module, a feedback module and a singlechip control module;
The connection relation 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 meanwhile, 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 optocoupler isolation function, a 5V direct current power supply, 16 CBB capacitors and 16 resistors with resistance value of 1 kI; 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 relay module are respectively connected to the positive electrode c and the negative electrode d of the 5V direct current power supply; the high-low level trigger selection ends S1-S16 of each relay are respectively inserted with an H jumper cap matched with the high-low level trigger selection ends S1-S16; the input signal trigger ports IN1-IN16 of each relay are respectively connected with an external bidirectional input/output (I/O) port of the singlechip control module; the normal open ends NO1-NO16 of each relay are connected to an m end, and the m end is connected to the output end of the transducer driving power supply; the common terminals COM1-COM16 of each relay are correspondingly connected with one end of a CBB capacitor, the other end of each CBB capacitor is connected with an n-terminal, and the n-terminal is connected with the input end of the transducer; the normally closed ends NC1-NC16 of each relay are connected with one end of a1 kI resistor, and the other end of each resistor is connected with the other end of the CBB capacitor;
The signal acquisition module comprises three precise sampling resistors R 31、R32、R33; one end of the resistor R 31 is connected with the m end of the impedance matching module; the other end of the resistor R 31 is connected with one end of the resistor R 32; the other end of the resistor R 32 is connected with one end of the resistor R 33; the other end of the resistor R 33 is connected with one input end b2 of the transducer b; one end of the resistor R 31 is also connected with one output end a1 of the power supply a; one end of the resistor R 32 is also connected with a voltage sampling end SV 2; the other end of the resistor R 32 is also respectively connected with a voltage sampling end SV1 and the other output end a2 of the power supply a; one end of the resistor R 33 is also connected with the current sampling end SC 2; the other end of the resistor R 33 is also connected with a current sampling end SC 1; the n end of the impedance matching module is connected with the other input end b1 of the transducer b;
The control method of the automatic impedance matcher of the magnetostrictive transducer comprises the following steps:
the method comprises the steps of firstly, powering on the device, initializing a system, and then carrying out a second step;
step two, after delaying for 10ms, the signal acquisition module samples the voltage and the current of the transducer;
Thirdly, judging whether the zero crossing frequency n >3 of the current in one period is met or not by the singlechip, controlling two sets of 8 relay modules with the optocoupler isolation function in the impedance matching module if the zero crossing frequency n >3 of the current in one period is met, increasing the matching capacitance according to the Step length of Step0 = 1 mu F by controlling the start and stop of the relay, and returning to the third Step for continuous judgment; executing the fourth step if n >3 is not true;
Fourth, judging whether the phase difference theta >50 DEG output by the feedback module is true, if so, enabling step=1μF, namely, a large Step length, and then jumping to a seventh Step; executing a fifth step if the first step is not true;
Fifthly, judging whether the phase difference theta >20 degrees output by the feedback module is true, if so, enabling step=0.2 mu F, namely, a middle Step length, and then jumping to a seventh Step; if not, executing a sixth step;
A sixth Step of judging whether the phase difference theta >5 DEG output by the feedback module is true, and if so, making step=0.1 mu F, namely a small Step length, and executing a seventh Step; if theta is larger than 5 DEG, the automatic impedance matching is finished, and the operation is finished;
Seventh, judging whether the phase relation Q=0 of the voltage and the current output by the feedback module is met, and controlling relays in two sets of 8 paths of relay modules with the optocoupler isolation function in the impedance matching module according to a judging result: if Q=0 is met, the matching capacitance is increased according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; if Q=0 is not met, the matching capacitance is reduced according to the Step value of Step by controlling the start and stop of the relay, and then the second Step is skipped; and continuing to execute the automatic matching flow until theta >5 DEG is not established in the sixth step, and ending the operation.
2. The automatic impedance matcher of magnetostrictive transducer according to claim 1, wherein 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 trigger adopting a 74LS74 chip and an exclusive-OR gate adopting a 74LS86 chip; the connection relation of the module 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 the 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 electrode input end of the 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 grounded; the output ends of the two high-speed zero-crossing comparators are respectively connected to the input ends of the exclusive-OR gates.
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| CN113533854B (en) * | 2020-04-13 | 2023-04-11 | 上海交通大学 | Impedance on-line measurement and dynamic matching device of ultrasonic transducer |
| CN111504444B (en) * | 2020-04-22 | 2021-11-05 | 清华大学 | Device and method for determining resonant frequency of giant magnetostrictive ultrasonic transducer |
| CN111766552B (en) * | 2020-07-06 | 2022-12-27 | 河北工业大学 | Automatic impedance matching device and method for magnetic characteristic measurement system |
| CN113992052B (en) * | 2021-10-28 | 2023-08-18 | 河北工业大学 | Automatic tracking device for resonant frequency of magnetostrictive transducer |
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