The measurement technique of machine tool transmission error considers to sum up

Factory of machine tool of Shanghai of institute of tool of Chengdu of laser of 632 pairs of frequency 0.

Chongqing of 158 university of Tokyo of magnetism bar sensor manage in university China factory of machine tool of work college Hanjiang university of American power Si Kangxing factory of machine tool of Han Chuan of university of industry of Shandong of 21 inductions synchronized 120.

Transmission error of 72 current and commonly used a few kinds of machine tools measure the partial application circumstance of sensor to see right table. What export way according to signal is different, can be sensor cent imitate type and digital type two kinds big. Type sensor can divide the number to make type wait for a few kinds for increment type, very form and signature again. In computer test system, the output signal of imitate type sensor needs to use modulus converter (A/D) undertakes digitlizing handling, and the cost that changes in the A/D below high resolution circumstance is higher, in addition solve tiny imitate signal (like class of small bend over) interference rejection question is quite difficult also. In digital type sensor, very form coder can output collateral number signal, need not A/D changeover, easy with computer interface. But rise as what measure precision, the cost of very form coder is higher and higher also, the cost that changes high even at high accuracy A/D, because this is in,a lot of actual application circumstances are accepted hard. The production cost of increment type sensor and sensor of signal modulation type is inferior, interference rejection capability is stronger, fractionize technology is used to raise resolution substantially below the condition that can not changing coder reticle density, in transmission catenary precision accordingly these two kinds of sensor in measuring are used most. Common increment type sensor includes the sensor of bar of grating increment coder, magnetism, coder that hold bar to wait; Sensor of signal modulation type basically has interferometer of inductive synchronized, laser, seismometer, change coming back to press implement etc. Measure a principle basically of the transmission error of dynamic measurement technique of transmission error of 3 machine tools. Set θ 1, θ the 2 displacement that are input, take-off respectively (angular displacement or) of displacement of the lines, the academic drive between input, output is compared for I, be like with θ 1 as fiducial, the poor value of the actual displacement of take-off and academic displacement is δ of transmission catenary error namely, namely 1/i of θ of 2- of δ = θ . Move according to counterpoint signal θ 1, θ the measurement technique of 2 is different, transmission error measurement technique can be divided to measure a way than measuring law and count two kinds big. 3.

Transmission error of 1 machine tool is compared measurement technique the output signal θ of two sensor 1, the 2 phasic relations between mirrorred θ the transmission error of transmission catenary. When transmission error TE=0, namely transmission is timer than constant, θ 1, θ 2 between the phasic relationship that keeps constant; When transmission changes than I happening, θ 1, the 2 phasic relations between also produce θ subsequently change. Determine than measuring a law to be passed namely θ 1, the 2 phasic relations between come to θ TE of indirect measurement transmission error. As the development of digital technology, computer technology, compare photograph → number to compare the development process of the photograph than number of photograph → computer from imitate than measuring a law to experience. Imitate compares look doctrine to touched hairdo phase meter commonly usedly to use imitate to compare look doctrine namely. Imitate compares the principle of the photograph. Two signal are the same as frequency signal to enter via turning into after scale down than photograph plan, the T of time difference δ between them depends on θ 1, θ the 2 phasic difference δ between (T) . Classics is bistable after trigger is differentiated, Δ T commutation is measure Δ U with the imitate that occupies sky comparing to answer relatively than rectangular wave, the change that takes sky comparing reflected the transmission error of transmission catenary namely. Imitate puts in the following problem than surveying a system: ① δ (T) is the periodic function that be cycle with 2 π and changes by definite pattern, set F to be phasic change frequency, f of ω =2 π is horny frequency, have &delta(t)= δ (ω T) . Two signal see graph 2b than the undee graph when the photograph. Right now, phasic measuring is the repetition that is cycle with 1/f is measured, by the condition 0 ≤ δ (2 π of ω T) ≤ are knowable, Δ U and δ (T) has linear concern. As a result of δ (ω T) shows periodic change, because this asks analogue recording expresses the time constant of the head: Be less than the change that be measured the cycle of phasic difference, namely: τ ≤ 1/f, when accurate reading been not obtain inside cycle of a phasic change afore otherwise, a cycle already began to repeat after, change with respect to what cannot record phasic difference in real time so. The trends that compares look doctrine because of this imitate measures performance poorer, the trends that cannot get used to modal analysis to handle gauges a demand. ② is measured resolution and measure limits to be restricted each other, if raise resolution, can reduce span, need to configure span to choose circuit for this, the phasic difference of the signal that be measured must be less than 360 ° . ③ asks to enter the two signal frequency that compares photograph plan identical, can undertake is the same as frequency comparing photograph only namely, the scale down because of these two signal / frequency multiplier must satisfy transmission compare metabolic requirement, circuit structure is complex, interference rejection ability is poor, suitable scope is lesser. Law number compares digital comparing photograph to use logistic door and tally to come true, phasic difference measures formal output with the number directly, its compare photograph principle. θ of 1/ of θ of the two signal that be the same as frequency gets U1 of signal of two groups of pulse, U1 after plastics of 2 classics enlarge, they pass what logistic door circuit controls tally to leave respectively, close. The computation result of tally is θ namely 1, θ the 1 time-interval Δ T between, it and phasic difference δ (T) becomes direct ratio. Set it is T than believing date is periodic, have δ (T/T of T)=2 π Δ . The number is than measuring the main characteristic of the law: ① depends on not only as a result of Δ T value the phasic poor &delta(t) of two signal, and still concern with the frequency of two signal. Accordingly, to obtain relatively the measurement of high accuracy result, must make sure two all have than photograph pulse signal and clock signal relatively high accuracy. periodic T is compared in inside, any causing the element that changes than believing size frequency measures the effect the outcome. ② although the number compares a few inadequacy of the photograph than making up for imitate, measure stability and dependability to rise somewhat, but still can apply to only with frequency comparing photograph. Personal computer fractionize compares look doctrine 20 centuries since 80 time, test instrument personal computer is changed make the significant progress trend that measures a technology. Measure in machine tool transmission error in, personal computer fractionize compares look doctrine (measure a principle) begin to get applied extensively. Personal computer fractionize compares the personal computer that look doctrine is doctrine of digital comparing look to turn application. Because the computer has function of function of powerful logic, numeric operation and control, the fractionize of high frequency clock that realizes two signal extremely easily, than photograph and output, because of this periphery circuitry make simpler. If graph 3b place is shown, transmission error is δ (T)=2 π Nt/N. In comparing photograph process, Ø of high frequency pulse arises by exterior oscillating circuit no longer, and the clock CP that uses computer interior directly; The computation of pulse CP employs tally of logistic door circuit no longer, and use the computer inside but process designing is time / tally. Personal computer fractionize has following advantages than measuring a way: ① compares photograph signal twice beardless frequency is same (be measured namely the drive of transmission catenary is worth) than can be random, in the computation of transmission catenary error, transmission comparing is one constant. ② can be aleatoric value than phasic difference, do not suffer phasic difference to must be less than the limitation of 360 ° . ③ realized clock fine dispenses to compare the unifinication of the photograph, make hardware interface circuitry simplifies greatly. As a result of but the scale down number of process designing tally can be controlled by computer software, because this can adjust sampling frequency conveniently, in order to get used to the measurement of error of catenary of the drive below different rotate speed. The fractionize precision of ④ system and measure precision taller, facilitate form intelligence to change, muti_function survey a system. 3.

Imitate of measurement technique of computation of transmission error of 2 machine tools compares photograph and number to be the same as frequency comparing photograph than all be, compare photograph signal with frequency to obtain, must have transmission score frequency above all; Produce 2 π to make sure each error limits is not sent phasic retroflexion, still need to undertake span scale down. Because scale down can be reduced,measure resolution, because this must have times frequency first before scale down, this makes measure a system to become relatively complex. In addition, because of,to be not integer transmission is compared cannot scale down and cannot undertake metrical. Digital computation measures a law to use be different from frequency comparing photograph, because this does not need to undertake to two pulse signal scale down is handled, can use two sensor to output the quantitative impact between pulse to calculate directly machine tool transmission error. Direct computation measures a way direct computation measures law principle. Those who set sensor of input, take-off every turn output signal number is λ respectively 1, λ 2, choose take-off θ 2 as fiducial axis, sampling interval T is equal to θ the cycle of 2 pulse signal or its integer times. According to the definition of transmission error, the transmission error when J second sampling is: δ (π of 1/&lambda2)] 2 of λ of J)= [N1(tj)-N2 (tj (i / λ 1. As a result of θ 1, θ the 2 pulse alignment that are the disperse on time, in measuring a process accordingly, sampling time-interval (N2 2 pulse of θ ) inside the J) of θ of computation N1 (t of 1 pulse of θ is along with time change, and it is blame integer normally (5) seeing a picture. Such, the 2 π of error Δ that place of Δ of its decimal part causes / λ 1 by oversight. In addition, of actual transmission system (2) of λ of I λ 1/ always is not integer certainly, namely pulse θ the frequency of 1 is not θ certainly the integer of 2 times, if regard N1 theory as integer,processing will cause academic error, restrict its to use range thereby. Computation of personal computer fractionize measures computation of fractionize of law personal computer to measure law principle. The measurement of this method measure is: 2 pulse of a θ serve as before ① open the door signal, 2 pulse of a θ serve as after close signal, be opposite with tally θ the pulse of 1 several N1 have count; ② uses clock pulse CP to be opposite pulse alignment θ 1 undertake interpolation fractionize, to θ the decimal and periodic computation of 1 pulse signal is worth T Δ and integral and periodic computation to be worth T2 to part computation; ③ computation transmission error: &delta(t)= (N0+T Δ / λ of π of 2) 2 of λ of 1/ of T2- I λ 1. Computation of personal computer fractionize measures a law to have the following advantage: ① can be reduced effectively measure error Δ ; ② can make full use of computer interior resource and software control will simplify exterior hardware circuit; ③ will measure sampling, data processing and result analysis be in harmony to be an organic whole, realized intelligence to change measure. CNC Milling