CN103894590B

CN103894590B - Cast by digital ultrasonic-frequency power supply control system

Info

Publication number: CN103894590B
Application number: CN201310524468.6A
Authority: CN
Inventors: 李晓谦; 蒋日鹏; 张立华; 赵啸林; 彭浩
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2013-10-31
Filing date: 2013-10-31
Publication date: 2016-09-07
Anticipated expiration: 2033-10-31
Also published as: CN103894590A

Abstract

The invention discloses a kind of design cast by digital ultrasonic-frequency power supply control system, including following aspect: (1) present invention proposes a kind of design casting based on DSP2808 digital ultrasonic-frequency power supply control system, supersonic generator main circuit and includes: rectifier transformer, diode rectifier circuit, MOSFET single-phase full bridge inverter circuit, analog input unit, waveform conversion electricity forms with match circuit；(2) existing auto-excitation type ultrasonic power is susceptible to the phenomenon of off resonance, and native system devises manually and automatically two kinds of mode of operations, controls to realize the real-time tracking of frequency by software.The frequency real-time tracking realized by software is that maximum virtual value based on electric current controls, and is maximum feature according to current effective value during resonance；(3) advantages such as test proves, it is big that the ultrasonic power of this programme design has tracking frequency scope, longevity of service, have all had than original auto-excitation type ultrasonic power and have been significantly improved.

Description

Cast by digital ultrasonic-frequency power supply control system

Technical field

This patent relates to the control technical field of aluminum alloy casting technique, in particular, provides A kind of digital ultrasonic power control system.

Background technology

Now, typically use and before metal freezing or in process of setting, apply additional physical field Method, i.e. utilizes the interaction between metal and physical field, improves its solidified structure.? Applying ultrasonic in Solidified Process of Aluminum Alloys is to improve its institutional framework, the one of raising mechanical property Effective method, the process optimization of beneficially aluminium alloy cast form and tissue modulation, obtain Obtain high performance cast article.When ultrasonic wave is propagated in the melt, melt is by periodically alternation The effect of sound field, produces a series of nonlinear effect such as cavitation, acoustic streaming, adds the shape of metal Core rate, can produce obvious grain refining effect, and the temperature simultaneously making alloy overall becomes with chemistry Divide homogenization, such that it is able in the mechanical property fundamentally improving aluminium alloy.

Supersonic generator aspect, 20th century the mid-80 begin to use high-power high-frequency Switching transistor, amplifier form mostly based on self-excitation D class half-bridge or full-bridge, afterwards he The high power module amplifier swashing formula the most constantly occurs.Signal is occurred by auto-excitation type ultrasonic power Device, power amplifier, output transformer and transducer etc. are whole and have arrived one, constitute one and close Loop back path, makes whole generator by amplitude, phase feedback, produces enough power, make to change Can remain in resonant frequency by device, and separated exciting ultrasonic power includes two parts, front Level be signal generator, rear class is power amplifier, finally by output transformer coupled after add On transducer.

In ultrasonic casting experiment, ultrasonic transducer system and high temperature aluminium alloys melt contacts, it is humorous Vibration frequency, impedance etc. can occur significantly to change.The most domestic normal ultrasound waves power supply Yin Qicai Using auto-excitation type circuit, frequency-tracking narrow range, the energy converting system working time is the longest, its resonance frequency The output frequency (frequency deviation degree) of rate deviation generator is the biggest, and tool heads vibration amplitude is the fewest, when When frequency deviation reaches to a certain degree, ultrasonic power will take protection act so that system stops Run, it is necessary to just can work on after energy converting system is cooled down, cause casting to be interrupted.Owing to changing Can system be affected bigger by high temperature aluminium alloys melt, the domestic conventional analog ultrasonic electric of self-excitation , often there is off resonance in source cisco unity malfunction, causes tool heads end face amplitude to reduce and arrange disappearance, Ultrasonic machining can not effectively be carried out.It is therefore desirable to design one can follow resonant frequency automatically Digital ultrasonic-frequency power supply.It is carried out frequency-tracking, rate-adaptive pacemaker scope is increased, fits Aluminium alloy is answered to cast condition of work.

Summary of the invention

The technical problem to be solved is to provide one can meet particular aluminum alloy casting Safe and reliable, the power control system that real-time is high, with strong points made.

In order to solve above-mentioned technical problem, the particular aluminum alloy casting power supply control that the present invention provides System processed,

Ultrasonic power is that by AC-DC-AC, power frequency 220V voltage is converted into high frequency voltage Output, promotes piezoelectric transducer vibration, obtains ultrasonic wave；

Obtain flowing through the electric current of transducer and transducer two ends by Hall element detection Voltage, DSP gathers electric current and voltage signal, sends with frequency, the side in dead band through computing Ripple forms two-way to drive circuit and drives signal to promote opening and closing of inverter；

Casting resonant ultrasonic tool generator system includes: TMS320F2808DSP circuit master control Device, rectifier transformer, diode rectifier circuit, MOSFET single-phase full bridge inverter circuit, The conversion of analog input unit, waveform and match circuit；

Control circuit main controller is TMS320F2808DSP, and major function is to receive various setting Determining information and instruction, the break-make of the pwm signal control MOSFET producing certain frequency is defeated Go out the voltage signal of required voltage amplitude and frequency, make transducer always work in resonant frequency Point, meanwhile, also man-machine interaction, signal sampling and fault self-diagnosis function；

Main circuit is mainly made up of diode controlled rectifier and PWM inverter, passes through The pwm signal of DSP output certain frequency controls MOSFET inverter regulation output voltage And frequency；

Waveform conversion comprises high-frequency power transformer with match circuit, is used for boosting and isolating, Avoid load end inductance to produce instantaneous pressure under high frequency effect and damage power device；

DSP adjusts the defeated of MOSFET in time by the phase place of sampling and outputting voltage and electric current Going out electric voltage frequency, the resonant frequency of real-time tracking transducer, meanwhile, DSP detects fault in real time Main circuit is protected by signal, the performance that the system that reaches is non-maintaining.

Optionally, the software of frequency-tracking realizes comprising both of which: one is manually The mode of button changes frequency, if frequency shift is a lot, directly inputs numeral and changes frequency； One is that autotrack mode changes frequency；

It is maximum feature according to current effective value during resonance, at a resonant condition, ultrasonic changes The impedance of energy system is minimum, therefore will export maximum current, uses the method for frequency sweep to search for super The resonant frequency of sound energy converting system, the virtual value of described electric current is defined as:

First gathered according to time interval t within several cycles by programming when of practical operation Multiple discrete point electric current ix, then find two adjacent some iA, iB in these are put, make Obtaining iA<0, iB>0, obtaining iA point has a zero crossing in iB point, then finds N-2 backward Individual, N=T/t, T=1/f so that this N number of point falls in a cycle, by Approximation draws its virtual value.

Use the power control system of technique scheme, during work, use ac-dc-ac inverter former Reason, it is achieved the continuously adjustabe of output frequency, can regulate output work by rectifier transformer simultaneously Rate size, uses LCD to show voltage and current parameter and frequency parameter in real time.

The present invention compensate for the deficiency that conventional ultrasonic-frequency power supply control system exists, and adds metal Nucleation rate, obvious grain refining effect can be produced, make the overall temperature of alloy and change simultaneously Studying point uniformly, aluminium alloy capability is improved.The present invention have high reliability, high flexibility, High EMC, can long-term stable operation；Easy to maintenance, standardization and seriation can be realized.

In sum, the present invention is a kind of real-time designed for particular aluminum alloy casting Reliable and stable power supply high, with strong points, based on TMS320F2808 microprocessor controls System.

Accompanying drawing explanation

Fig. 1 is ultrasonic power device hardware entire block diagram；

Fig. 2 is frequency automatic Search/Track program flow diagram.

Detailed description of the invention

The invention will be further described with detailed description of the invention below in conjunction with the accompanying drawings.

Seeing Fig. 1, control circuit main controller is TMS320F2808, and inverter bridge makes purpose method The MOSFET of semiconductor company realizes the FREQUENCY CONTROL to output voltage signal, and analog quantity is defeated Enter unit to be made up of Hall element and advance signal process circuit, therefrom obtain electric current, voltage Live signal, thermocouple is obtained the temperature signal of load, then data is delivered to by AD sampling Control mainboard to process；Display unit uses the LCD MODULE of high-quality LCD128645ZK, often screen can show 8 × 4 Chinese characters (16 × 16) or 128 × 64 The figure of pixel makes simultaneously, and native system also has the functions such as fault self-diagnosis.

Equipment is after powering on and preheating inspection normally, and main program completes to initialize, and enters Automatically search for resonant frequency, after band resonant frequency searches, enter the frequency-tracking stage.From Shown in dynamic search rate and trace routine flow chart 2.

The invention have the advantage that

(1) this supply unit is the design of extraordinary aluminum casting purposes, have the strongest specific aim and Practical value；

(2) use total digitalization directly to control technology and replace original analog control technique.Logical Cross DSP technology to realize controlling and signal processing function；

(3) contrast before use by device monitor electric current and the phase place of voltage, the present invention Use frequency search algorithms based on electric current maximum virtual value, it is achieved the real-time tracking of frequency.? Under condition of resonance, the impedance of ultrasonic transducer system is minimum, therefore will export maximum current, uses The method of frequency sweep searches for the resonant frequency of ultrasonic transducer system；

(4) advantages, all ratio such as the ultrasonic power of this programme design has tracking frequency scope greatly, longevity of service are original Auto-excitation type ultrasonic power has had and has been significantly improved.

Claims

1. a digital type ultrasound wave power control system based on aluminum alloy casting technique, it is characterised in that:

Ultrasonic power is by AC-DC-AC, power frequency 220V voltage to be converted into high frequency voltage export, and promotes pressure Electricity energy converting system vibration, obtains ultrasonic wave；

Obtaining flowing through electric current and the voltage at transducer two ends of transducer by Hall element detection, DSP adopts Colleeting comb and voltage signal, send the square wave with frequency, dead band through computing and form two-way to drive circuit Signal is driven to promote opening and closing of inverter；

Casting resonant ultrasonic tool generator system includes: rectifier transformer, diode rectifier circuit, MOSFET The conversion of single-phase full bridge inverter circuit, analog input unit, waveform and match circuit；

Control circuit main controller is TMS320F2808 DSP, and major function is to receive various set informations and refer to Order, the pwm signal producing certain frequency controls break-make output required voltage amplitude and the frequency of MOSFET Voltage signal, make transducer always work in resonant frequency point, meanwhile, also man-machine interaction, signal are adopted Sample and fault self-diagnosis function；

Main circuit is mainly made up of diode controlled rectifier and PWM inverter, certain by DSP output The pwm signal of frequency controls MOSFET inverter regulation output voltage and frequency；

Waveform conversion comprises high-frequency power transformer with match circuit, is used for boosting and isolating, it is to avoid load end Inductance produces instantaneous pressure under high frequency effect and damages power device；

DSP adjusts the output voltage frequency of MOSFET in time by the phase place of sampling and outputting voltage and electric current, The resonant frequency of real-time tracking transducer, meanwhile, DSP detects fault-signal in real time and protects main circuit Protect, the performance that the system that reaches is non-maintaining.

Digital type ultrasound wave power supply based on aluminum alloy casting technique the most according to claim 1 controls system

System, it is characterised in that:

The software of frequency-tracking realizes comprising both of which: a kind of is that the mode of manually button changes frequency Rate, if frequency shift is a lot, directly inputs numeral and changes frequency；One is that autotrack mode changes frequency Rate；

It is maximum feature, at a resonant condition, the resistance of ultrasonic transducer system according to current effective value during resonance Anti-minimum, therefore will export maximum current, use the method for frequency sweep to search for the resonance frequency of ultrasonic transducer system Rate, the virtual value of described electric current is defined as:

First within several cycles, multiple discrete points are gathered according to time interval t by programming when of practical operation Electric current ix, then finds two adjacent some iA, iB in these are put so that iA<0, iB>0, obtains IA point and iB point there is a zero crossing, then finds N-2 point, N=T/t, T=1/f so that this N backward Individual point falls in a cycle, byApproximation draws its virtual value.