Programmed control is supersonic the frequency that machines power source dogs and constant control

In This Paper, the Reason Of Treating Current As Feedback Is Analyzed With Circuit Theory, the System Of Ultrasonic Generator Controlled With A Single-chip Computer And The Realization Methods Of Frequency Tracking And Amplitude Stabilizing Are Introduced, the Software Of Adaptive Tracking And PID Are Completed.

1 brief introduction is supersonic in machining a process, area of the temperature of oscillatory system, stiffness, dead load, treatment, tool wears away the change that waits for an element, make systematic natural frequency produces drift, this asks supersonic generator has frequency to dog automatically function, protect supersonic system to make sure treatment quality is mixed at the same time, requirement generator has the function that adjusts output power according to load. Traditional supersonic generator uses valve oscillator to generate high frequency signal, via ultrasonic arising after power magnifies, its defect is to realize frequency to dog hard, the change that cannot get used to load (be like: Of the tool change, wear away wait for) , and valve returns the job at linear area, loss is big; Additional, working stability is poor, and the ability that start is poor. Supersonic power source uses IGBT of power parts of an apparatus in the article, it works at switch condition, loss is small and working frequency is tall; Use sheet piece machine software runs Bu Changpin rate dogs automatically, accelerated dog speed, and search limits precision of bigger, search is tall; Undertake amplitude and power are controlled automatically outputting, realized constant amplitude and output of power of unit load constant, rose to machine quality and efficiency thereby, realized frequency number to show protect with software. Principle of 2 supersonic generator 2.

The academic basis basis that 1 choice electric current measures as feedback control the equivalent of machinery and report is theoretical, supersonic transducer can use equivalent of network of a two port, if the graph is shown 1 times, r, R states transducer inputs voltage, electric current, z, Z expresses mechanical Duan Zhen motivation, brace up fast, rz is mechanical impedance. The Z parameter equation of the network is: , because transducer loss can be ignorred relative to sound energy, z is equivalent to pure reactance parameter, criterion Z parameter equation can express to be: Graph 1 transducer equivalent is two-terminal buccal network (1)(2) 　 couplet stands (1)(2) type solves: (3)(4) 　 is become type (on the right side of 3) model most hour, the virtual value of R takes maximum, become so (when 5) , namely when transducer is syntonic, the voltaic virtual value that inputs transducer is the greatest. By type (4) gets: (6) 　 by vertical brace up the characteristic and knowable X22Rz of transducer, type (6) can simplify for: (When 7) is syntonic, zhen Zizhen A is: (8) ω is syntonic horn frequency, type (7) generation enters type (8) gets: (Transducer of X22 of 　 of 9) 　 , X21 is inherent parameter is constant, when ｜ R ｜ is constant, output amplitude A is constant. Analyse by above knowable: Can adjust virtual value of transducer electric current as feedback quantity inversion frequency and rectification output voltage, implementation exceeds sound system resonance control and amplitude are constant output control. 2.

Supersonic generator principle sees construction of system of 2 supersonic generator graph 2. Suddenly Er sensor obtains signal of voltaic virtual value, send sheet via signal of number of fast A/D translate into piece machine, odd a signal of virtual value of machine analysis electric current, through D/A output voltage control presses the oscillation frequency that accuses oscillator VCO, repass hardware circuit forms dead band to protect power switch component, prevent direct; Use finally special spark integrated circuit sparks switch component. At the same time odd a machine use detected voltaic value to control synchronous oscillator through D/A, undertake rectification is controlled, achieve transducer to input the purpose with constant electric current. Because virtual value of inversion around electric current is approximate equal, before exiling check Yu Ni changes normally in actual circuit. Graph 3 control circuit and software realize block diagram of principle of 2 supersonic generator 3.

1 inversion control and change Bu Changpin rate dogs odd a machine undertake the signal of load current virtual value that detects and the biggest load current comparative, decide D/A outputs the size of voltage, the bulk that controls the input voltage that accuses an oscillator to decide to output frequency through adjusting thereby (pressure accuse an oscillator to choose MC1046B, when inputting voltage to rise 5V from 0V, output frequency is the) of square wave signal of 10 ～ 30kHz, those who make is as syntonic as transducer; Dead band forms circuit to use trigger of only stable state to form dead band time (but the) of set of power switch parts of an apparatus that the basis chooses; Drive piece uses EXB841 of module of IGBT special drive to have drive. In machining a process, the cent of natural frequency change of oscillatory system is slow frequency change and instantaneous frequency change. The drift of the syntonic frequency that wears away to be caused with temperature change by the tool attributes slow change; The drift of the syntonic frequency that causes by the change of load and systematic stiffness attributes sudden change, frequency dogs automatically requirement generator dogs well and truly of systematic natural frequency slow or sudden change. If the graph is shown 3 times,electric current and frequency concern, among them the natural frequency that F1 represents a system, systematic work hereat when frequency, the electric current that has shed transducer is the biggest, tool head amplitude is the biggest; And after machining period of time, frequency may arrive adrift F2, only right now tool head amplitude gift is the greatest. Graph electric current of 3 luffing lever (admittance) the concern with frequency is additional, because luffing lever material machines appearance of craft, Zhen Ziben body to wait for a reason, can make brace up child have sex of much peak value (3) seeing a picture, so, when beginning to machine, go with greater pace progress first search of natural frequency limits, when the search is in frequency domain to natural frequency, convert change the pace grows a search. In machining a process, systematic natural frequency is slow when change, use half step progress to be searched all right; Should plant as a result of some when reason natural frequency is choppy, small step pitch searchs syntonic dot to need longer time, the influence machines efficiency, if use the method that grows with half step after the stride is long to undertake searching first, saved many time undoubtedly, assured to dog speed and precision; Notice at the same time: When natural frequency is choppy, as a result of brace up child sex of much peak value, the likelihood dogs to be nodded to lesser voltaic peak value, i1 of limits of reason set electric current, exceed range (namely under I1) when, undertake whole journey of natural frequency limits is searched afresh. Join dog the improvement of limits changes block diagram of pace long search sees a picture 4. Graph 4 change A of block diagram of pace long search -- detected electric flow, b -- frequency control measures output, c -- search condition is chief, b3, B4 -- dog limits set quantity, amax -- the biggest electric current, bmax -- the frequency when maximum of corresponding electric current controls an amount, I -- the search dogs frequency 3.

2 commutate circuit and transducer output are constant amplitude control is machined actually in, mechanical load is often change (the metabolic) of the diameter when machining alveolus, although frequency dogs good, laden accretion also can cause those who output power of load of amplitude, unit to drop; Especially in process of ultrasonic device work, luffing lever from have carry turn into to carry for nothing (or carry for nothing turn into have carry) when, mechanical impedance urgent revulsion is small (or big) , supersonic generator and transducer are damaged extremely easily, the stable dependability that machines exterior quality and process to rise at the same time, requirement transducer passes missive machinery to power follows laden change and change, namely amplitude of tool head output is constant. Use job of transducer constant electric current, voltaic adjustment through adjusting the discretion of voltage of output of commutate of single-phase bridge-type half control comes true, adjust namely brilliant brake is in charge of spark time will achieve adjust voltage adjusts thereby the purpose of transducer electric current, specific control circuit sees a picture 5. When beginning the work, odd a machine output a set controls an amount, undertake modulatory according to sampling electric current and set electric current next. Adjust methodological cent is moved for the hand and automatic two kinds of means. The hand changes way is to adjust directly the size of resistor Rp, change rectification to output the size of voltage thereby; Automatic means is the sheet of voltaic signal classics that will detect piece after machine computation, through D/A output controls what odd crystallization body is in charge of to guide a time, odd form transistor guides while spark brilliant brake canal, make brilliant brake canal guides, when main circuit voltage is retrorse brilliant brake canal closes by oneself. Means of this kind of control still has the following advantage: Can judge transducer breakdown and part of oscillatory system join to whether become loose through outputting power; When load is too big, stop automatically to rectification is outputted and call the police; Frequency dogs when malfunction, start a system afresh. Graph circuit of 5 commutate control is odd a machine give electric current to make output electric current to dog quickly, use increment type number PID adjustment means, to overcome integral saturation, the decision after judgement uses the means that PD or PID adjust. Specific PID block diagram sees a picture 6, among them Ae is set electric current, u1 controls an amount for correspondence of electric current of the biggest output, k is scale enlarge multiple, I is integral enlarge multiple, d is differential enlarge number. Graph algorithmic block diagram of 6 commutate PID this circuit uses 4 hardware join and main program block diagram odd a machine and outside receive EPROM program memory to form control core, with Huo Er check flows piece with fast A/D converter composition inputs a passageway, adjust circuit and V/F module and special drive with two D/A piece composition outputs a passageway. Join means sees bibliographical reference [2] . The main program sees a picture 7. Graph block diagram of 7 main programs 5 last word 　 (1) frequency dogs technology and stable amplitude technology while introduce, improved work efficiency namely, assured to machine exterior quality again. (2) is passed hold voltaic virtual value constant, stable amplitude is a kind of approximate method, but through sheet piece the adjustment of machine can obtain favorable result. (3) is odd piece engine system is one kind is opened model system, can add new control way at any time, and need not change hardware circuit, realize systematic protection through software, reduced cost. (If 4) uses two CPU, one undertakes inversion is controlled, one undertakes rectification is controlled, the effect will be more ideal, can show frequency and amplitude at the same time. CNC Milling