EP1095712A1 - Procédé d'alimentation regulée pour converteur et générateur ultrason - Google Patents

Procédé d'alimentation regulée pour converteur et générateur ultrason Download PDF

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Publication number
EP1095712A1
EP1095712A1 EP99121286A EP99121286A EP1095712A1 EP 1095712 A1 EP1095712 A1 EP 1095712A1 EP 99121286 A EP99121286 A EP 99121286A EP 99121286 A EP99121286 A EP 99121286A EP 1095712 A1 EP1095712 A1 EP 1095712A1
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EP
European Patent Office
Prior art keywords
voltage
converter
frequency
pzt
ultrasound
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99121286A
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German (de)
English (en)
Inventor
Peter Solenthaler
Paul Lampel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telsonic AG
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Telsonic AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telsonic AG filed Critical Telsonic AG
Priority to EP99121286A priority Critical patent/EP1095712A1/fr
Publication of EP1095712A1 publication Critical patent/EP1095712A1/fr
Withdrawn legal-status Critical Current

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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
    • B06B1/0207—Driving circuits
    • B06B1/0223—Driving circuits for generating signals continuous in time
    • B06B1/0238—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave
    • B06B1/0246—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal

Definitions

  • the invention relates to a method for regulating the voltage supply for a Ultrasonic converter and an ultrasonic generator with the features of the generic term of the independent claims.
  • Piezoelectric transducer systems are primarily used here because of the capacitive component of the converter in the work area one series and one Have parallel resonance frequency. The same conditions also apply to magnetostrictive transducers, in which only the capacitive component by a is replaced inductive and vice versa.
  • Narrow-band ultrasound converter primarily when used in welding systems for Plastics and metals have to be operated exactly at their resonance frequency, to guarantee a constant vibration amplitude and on the other hand for a reliable operation with increasing load the voltage and Keep current values at the converter within limits.
  • Ultrasonic converters are used in a wide variety of applications. Areas of application are e.g. Welding, cutting, cleaning, screening, sonochemistry and many other applications.
  • the load changes frequently during operation. Through the Coupling the converter to the load becomes the resonant frequency of the converter out of tune during operation and must be readjusted very quickly by means of a regulation become.
  • ultrasonic welding e.g. the welding sonotrode with increasing force pressed on the object to be welded, which in turn on an anvil or bracket.
  • the values that limit the performance of the ultrasonic converter are Converter voltage and the converter temperature. Sufficient cooling is usually sufficient is present so that the problem of converter temperature is easier to solve.
  • the ultrasonic generator (with increasing load) is operated at the parallel resonance frequency f p .
  • the generator works together with the converter as a constant current source in order to keep the mechanical vibration amplitude constant with a variable load.
  • This circuit design means that the active power output is proportional to the load resistance when the converter is operated at its own resonances.
  • the ultrasonic transducer is operated with a constant amplitude.
  • the load on the ultrasound converter may not be increased further in known control methods in order to avoid destruction of the ultrasound converter, in particular of the piezoelectric disks (PZT).
  • phase locked loop It is known to frequency with analog phase locked loops based on the phased locked loop (PLL) circuit to regulate.
  • PLL phased locked loop
  • power means active power. Otherwise it is on Scheinoder Reactive power referenced.
  • the method according to the invention should also be sufficiently fast to achieve a Destruction of the ultrasound converter, to prevent in the event of rapid load changes.
  • a Another object of the present invention is an ultrasonic generator to create that is suitable for performing the inventive method.
  • the converter voltage increases in a first time period increasing load.
  • the voltage supply is regulated in this first time period in a manner known per se.
  • a similar procedure could also be used use sensibly with decreasing load.
  • the periods would be reversed i.e. the second period of high load comes before the Period with low load.
  • Rise and fall of the load can of course can also be repeated in the method and generator according to the invention.
  • Converter voltage in a second time period the amplitude of the output voltage of the ultrasonic generator and / or the frequency of the generator changed in such a way that the converter voltage becomes smaller as the load increases or preferably is or remains equal to the threshold.
  • the method according to the invention makes it possible to further increase the load (R s ) on the ultrasound converter even when the maximum permissible converter voltage is reached. So that the load on the ultrasound converter can be increased further without the risk of destroying the ultrasound converter, either the mechanical amplitude is reduced by reducing the voltage U o and / or the operating frequency of the ultrasound generator is shifted to a range in which the converter voltage is lower. than in the parallel resonance frequency (with the same load).
  • ⁇ are 0 for the serial resonance frequency and 0 for the parallel one Resonance frequency equal to 1 (this provided that the compensation on the converter is matched).
  • the load can continue to increase (R s ) provided that either the voltage U 0 is reduced (the value U 0 in the formula for the converter voltage is reduced, which reduces the active power) and / or if the value of ⁇ in the above formula is reduced.
  • the reduction in the value of ⁇ corresponds to a shift in the operating frequency of the generator from the parallel resonance frequency in the direction of the serial resonance frequency.
  • the phase shift between the voltage U o supplied by the ultrasound generator and the output current I out serves as a controlled variable in the first time period.
  • the setpoint of the phase shift is aimed at a minimum value of the phase shift, ideally 0 °.
  • the frequency of the ultrasonic generator is a manipulated variable. Controlling the phase shift to the value 0 ° means that the generator is operated at a frequency which corresponds to the parallel resonance frequency of the converter. An operation in the serial resonance frequency would be preferable in view of the converter voltage. However, this is because of the missing zero crossing of the phase between the voltage U 0 and the current l out in the case of serial resonance cannot be realized with previously known controllers.
  • the output power of the generator with increasing load on the ultrasonic converter kept constant.
  • the frequency of the ultrasonic generator from the parallel resonance frequency towards the serial resonance frequency changed.
  • the second period, the converter voltage is kept constant and the frequency of the Ultrasonic generator, for example, with increasing load in the direction of the serial resonance frequency updated.
  • the phase shift control variable is advantageous in the first area.
  • the setpoint the phase shift follows an adjustable setpoint curve.
  • the setpoint curve is predetermined depending on the circuit, preferably by a microprocessor, Microcontroller or digital signal processor specified.
  • the second area of the second time period preferably begins when the Frequency of the ultrasound generator approximately the serial resonance frequency of the converter corresponds.
  • the value of the serial and parallel resonance frequency is preferably determined automatically before a load R s is applied to the ultrasound converter or while the load R s is still relatively low, ie when the resonance circuit has a high quality (Q).
  • the value of the frequency spacing and other parameters determined in this way can stored and used to mark the beginning of the second area in the to determine the second period. If the frequency of the generator is going out from the parallel resonance frequency by the previously determined frequency spacing has changed, the frequency of the generator corresponds approximately to the serial resonance frequency. Since the frequency spacing usually changes with increasing load, in general, however, the generator frequency is not exactly the serial resonance frequency correspond.
  • the converter voltage is kept constant at this value when the threshold value of the converter voltage is reached.
  • the voltage U o of the generator is reduced.
  • the phase difference is regulated to a minimum value as defined above, preferably towards zero, so that the frequency of the ultrasound generator roughly follows the parallel resonance frequency.
  • This exemplary embodiment also allows extended operation with a further increasing load, even if the maximum permissible converter voltage has already been reached. In comparison to the first exemplary embodiment, the output power is limited more quickly.
  • the method according to the invention is advantageously carried out with a combination of a fast analog controller part with a slow digital actuator.
  • the analog controller reacts immediately with every load change, the digital controller only intervenes if the phases, current and voltage values have exceeded a certain limit. If the converter voltage is too high, the microcontroller then shifts the operating frequency to a range in the vicinity of f s . This allows the system to be typical at the same voltage 2 deliver greater performance. It is necessary to use an analog component in the control so that short reaction times can be achieved.
  • the regulation of the phase shift requires an adjustment of the frequency of the generator serving as the manipulated variable in the range of milliseconds.
  • control according to the present invention has an additional digital component.
  • the digital component acts on the analog part of the control, in particular by specifying a changed setpoint for the phase shift.
  • the proportion of analog and digital control is variably adjustable.
  • the generator assigns circuits for analog signal processing and circuits digital signal processing.
  • the circuits for digital signal processing work advantageous to that of analog signal processing.
  • FIG. 1 shows the equivalent circuit diagram for an ultrasound generator 2 with an ultrasound converter 1.
  • the generator 2 is operated as a current source and supplies a voltage U 0 with a frequency f, which leads to a converter voltage U pzt and an output current l out .
  • L k denotes an inductive compensation arrangement by means of which the output circuit of the ultrasound generator 2 is matched to the ultrasound converter 1.
  • l out denotes the current supplied by the ultrasonic generator 2.
  • U pzt denotes the converter voltage .
  • the converter voltage is the voltage that is present at the PZT elements (disks) of the ultrasound converter 1.
  • the load acting on the ultrasound converter 1 is denoted by R s .
  • the quantities L s and C s are the electrical equivalents of the mass and the elasticity of the mechanical vibrating structure.
  • Curve 21 denotes the maximum output active power to be achieved when operating the generator in the parallel resonance frequency f p .
  • the power is limited by the maximum voltage U pzt max that can be applied to the converter.
  • Curve 22 denotes the maximum output power that can be reached when the ultrasound generator 2 is operated in the serial resonance frequency f s .
  • the curve 23 shows the profile of the output power of the ultrasound generator 2 in a first embodiment.
  • a first time period t 1 , t 2 the voltage U 0 and thus the mechanical amplitude are kept constant.
  • the output power of generator 2 increases.
  • the frequency f of the ultrasound generator 2 tracks the changing parallel resonance frequency. The tracking is carried out by regulating the difference in the phase position of the voltage U 0 and the output current I out to a value close to 0 °.
  • the voltage U 0 the mechanical amplitude is reduced.
  • the converter voltage U pzt is kept at the maximum permissible value U pzt max.
  • the converter voltage U pzt is a controlled variable.
  • the setpoint is U pzt max .
  • the manipulated variable is voltage U 0 .
  • the voltage U 0 is reduced to a value which corresponds to approximately 50% of the mechanical amplitude in the first partial time period t 1 , t 2 .
  • FIG. 1 An alternative exemplary embodiment is shown in FIG.
  • the second time period t 2 , t 3 is divided into a first area t 2 , t x and a second area t x , t 3 .
  • the regulation in the first and in the second area is different.
  • Curve 24 shows the course of the output power in the alternative embodiment.
  • the output power P out of the generator is kept constant at the maximum value of 100% power with increasing load (R s ), but may also increase.
  • the controlled variable is P out while the voltage U 0 is the manipulated variable.
  • the frequency f of the voltage U 0 is changed from the value of the parallel resonance frequency f p in the direction of the serial resonance frequency f s .
  • the change in frequency f is controlled by regulating the phase difference between voltage U 0 and output current l out on a corresponding setpoint curve (FIG. 5). Starting from the previously determined frequency spacing ⁇ f between the parallel resonance frequency f p and the serial resonance frequency f s , the frequency is shifted from the parallel resonance frequency f p by the frequency spacing ⁇ f.
  • the phase shift ⁇ is regulated to 0 °.
  • the manipulated variable is the frequency f of the voltage U 0
  • the output power P out is kept constant.
  • the phase shift ⁇ no longer has a constant setpoint but follows a setpoint curve which is determined by the digital controller part (see FIG. 5).
  • the setpoint for the permissible phase shift ⁇ is determined in the microprocessor on the basis of the values of U 0 , l out and U pzt .
  • the manipulated variables are the frequency f and the voltage value of U 0. A combination of a digital and analog control method is therefore shown schematically in FIG.
  • the phase shift ⁇ is kept constant.
  • the phase shift is kept constant at the value close to 0 °.
  • the phase shift is kept at a constant value in the second region t x , t 3 . It is thereby achieved that the frequency f of the voltage U 0 roughly follows the serial resonance frequency which changes as the load increases.
  • the converter voltage U pzt is regulated to a constant (to the maximum permissible) value in the time period t 2 , t 3 according to FIG. 2 or in the second range t x , t 3 according to FIG. 3.
  • the manipulated variables are the frequency f and the voltage U 0 of the generator 2.
  • the digital controller is not absolutely necessary since the phase shift ⁇ is regulated to the value close to 0 °.
  • the phase shift .DELTA..phi . Is regulated to a predetermined value specified by the digital controller and dependent on U 0 , l out and U pzt .
  • FIG. 4 shows schematically the dependence of the amount of the load impedance Z L (with a low load) on the frequency f of the voltage U 0 . If the frequency f corresponds to the parallel resonance frequency f p , the load impedance Z L is at a maximum. If the frequency corresponds to the serial resonance frequency f s , the load impedance Z L is minimal.
  • the curve shown in FIG. 4 is determined with a frequency scan.
  • the parallel resonance frequency f p and the frequency spacing ⁇ f between the parallel resonance frequency f p and the serial resonance frequency f s can thus be determined.
  • the measurement of the parallel resonance frequency f p with small loads (idling) makes it possible to start at the beginning of the process with a frequency f of the generator 2 which is close to or corresponds to the parallel resonance frequency f p .
  • the frequency spacing ⁇ f allows the generator to be guided from the parallel resonance frequency in the direction of the serial resonance frequency in the region t 2 , t x according to FIG. 3.
  • FIG. 5 shows a possible setpoint curve for the phase shift according to the exemplary embodiment from FIG. 3.
  • the phase shift ⁇ is constantly regulated to 0 °. This ensures that the frequency f of the voltage U 0 follows the parallel resonance frequency f p .
  • a change in the phase shift ⁇ is permitted in a first range t 2 , t x .
  • the change is specified by the digital controller 3.
  • the phase difference ⁇ is changed so that at time t x the frequency f of the voltage U 0 has changed by approximately the frequency constant ⁇ f compared to the parallel resonance frequency f p .
  • the frequency f of the voltage U 0 corresponds approximately to the serial resonance frequency f s .
  • the phase shift is kept constant at this value.
  • FIG. 6 shows schematically the combination of an analog controller 4 with a digital controller 3 shown.
  • the time-dependent values of the voltage U 0 , the output current I out and the converter voltage U pzt are measured with a measuring arrangement 5.
  • an analog regulator part 4 is used which regulates the generator 2 in frequency f.
  • the setpoint for the phase shift between the voltage U 0 and the output current I out is predetermined for the analog controller 4.
  • the digital controller 3 is programmed (in the exemplary embodiment according to FIG. 3) such that the converter voltage U pzt is specified as a phase shift close to 0 ° until a threshold value U pzt max is reached.
  • the digital controller 3 specifies a phase shift ⁇ which changes according to FIG.
  • the increase in the phase shift can also be gradual, progressive, degressive (see dashed curves in FIG. 5).
  • the digital controller 3 again specifies a constant value for the phase shift ⁇ , which is not, however, equal to 0 °. In this time period, the digital controller also specifies a regulation of the output power P out to the maximum value of 100% nominal power.
  • the analog control loop does not detect a usable phase signal, the takes over digital controller 100% control of the frequency and is calculated from the measured Values the load impedance, which is needed to regulate the frequency.
  • the digital controller contains algorithms that work with multiple resonances in the work area automatically reduce the control range of both controllers and the optimal working frequency selects.
  • the digital controller communicates with a bus and / or user interface. All operating states can a superimposed control or computer for control and Logging will be passed.
  • FIG. 7 shows the schematic block or functional circuit diagram of a control circuit for the ultrasonic generator according to the invention. According to FIG. 7, the proportion is one analog and digital control variably adjustable.
  • the control circuit has a phase comparator 30 for determining the phase between the feedback variables voltage U 0 and output current I out .
  • the phase shift ⁇ determined by the phase comparator 30 is compared in a setpoint comparator 31 with a setpoint ⁇ setpoint.
  • the setpoint ⁇ set is specified by a setpoint generator 40.
  • a setpoint generator or actuator 33 can specify a variable setpoint.
  • the setpoint value output by the actuator 33 can be determined by a digital signal processing arrangement 34.
  • Various setpoints or setpoint curves are specified on the basis of the measured variables output current, voltage and converter voltage.
  • a controller 32 changes via a voltage controlled oscillator acting as an actuator 36 the frequency f of the generator 2.
  • a value of zero or close to zero can be specified by the actuator 40 as the setpoint for the phase shift ⁇ .
  • this operating mode is used.
  • the control is preferably carried out only by the controller 32 in the manner described and thus 100% analog.
  • the control loop also has a threshold limiter 38 for a minimum frequency f min and a maximum frequency f max of the voltage controlled oscillator 36.
  • the frequency range in which the frequency of the oscillator 36 can be adjusted can be determined using the threshold value limiter 38.
  • the limits of the analog control can also be set by the oscillator 36.
  • the control circuit also has schematically illustrated means 35 for switching on and off of the analog controller 32.
  • the analog controller 32 is switched off.
  • the regulation then takes place exclusively digitally via the digital frequency controller 37. This can be done manually or depending on the operating parameters (especially l out U o and U pzt ) by the switch-off means 35.
  • the control loop also has a digital frequency controller 37.
  • the frequency f of the generator 2 can be regulated via a circuit 39 for changing (ie increasing or reducing) the frequency.
  • the proportion is determined by setting the minimum and maximum threshold values f min and f max for the voltage controlled oscillator 36.
  • the frequency of the generator 2 is determined both by the frequency controller 37 and the circuit 39 and by the controller 32 and the oscillator 36. In this context, it is conceivable to influence the threshold limiter 38 with a microprocessor which interacts with the digital frequency controller 37.
  • the working curves of the controllers 32 and 37 as well as the actuator 33 and the setpoint generator 40 can be empirically predetermined and z. B. save and from one Call and process the microprocessor. The goal is maximum output power driving at the various load conditions and destroying the converter to prevent.
  • the properties of the resonance system can be advantageous before starting operation by operating the arrangement in a partial load range.
  • FIG. 8 shows an equivalent circuit diagram of an exemplary embodiment in which the properties of the resonance system are determined by a frequency scan.
  • a resistor R m is inserted in series between the generator 2 and the ultrasound converter 1 in FIG.
  • the resistor R m makes it possible to exclude the risk of overvoltage or overcurrent during the frequency scan to determine the frequency spacing ⁇ f.
  • the resistor R m is bridged during normal operation.
  • the values for ⁇ f and f p and f s determined in this partial load operation can be measured in a known manner by measuring arrangements (not shown) and used for the readjustment of the controllers 37 and 32 as well as the threshold value transmitter 38 and the actuator 33.
  • This system could also work with ultrasonic generators using a different method operate as the one described above for performing a secure frequency scan be beneficial.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Inverter Devices (AREA)
EP99121286A 1999-10-26 1999-10-26 Procédé d'alimentation regulée pour converteur et générateur ultrason Withdrawn EP1095712A1 (fr)

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Application Number Priority Date Filing Date Title
EP99121286A EP1095712A1 (fr) 1999-10-26 1999-10-26 Procédé d'alimentation regulée pour converteur et générateur ultrason

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP99121286A EP1095712A1 (fr) 1999-10-26 1999-10-26 Procédé d'alimentation regulée pour converteur et générateur ultrason

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010004468A1 (de) * 2010-01-13 2011-07-14 Maschinenfabrik Spaichingen GmbH, 78549 Verfahren und Vorrichtung zur Ultraschallbearbeitung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4336509A (en) * 1979-02-20 1982-06-22 Bosch-Siemens Hausgerate Gmbh Oscillation generator for an ultrasonic liquid atomizer
US4849872A (en) * 1986-07-25 1989-07-18 Gaessler Herbert Process and apparatus for phase-regulated power and frequency control of an ultrasonic transducer
US5184605A (en) * 1991-01-31 1993-02-09 Excel Tech Ltd. Therapeutic ultrasound generator with radiation dose control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4336509A (en) * 1979-02-20 1982-06-22 Bosch-Siemens Hausgerate Gmbh Oscillation generator for an ultrasonic liquid atomizer
US4849872A (en) * 1986-07-25 1989-07-18 Gaessler Herbert Process and apparatus for phase-regulated power and frequency control of an ultrasonic transducer
US5184605A (en) * 1991-01-31 1993-02-09 Excel Tech Ltd. Therapeutic ultrasound generator with radiation dose control

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010004468A1 (de) * 2010-01-13 2011-07-14 Maschinenfabrik Spaichingen GmbH, 78549 Verfahren und Vorrichtung zur Ultraschallbearbeitung

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