CN2489302Y - Closed ring ball-measuring induction rule - Google Patents

Abstract

The utility model relates to the numeral length measuring art and in particular to an automatic measuring ball inducing ruler for the flexible arm. The utility model mainly comprises a mechanical head and a main plate. The four number reading heads in the mechanical head output the one phase excitation signal by two phases; the two phases signal outputs the length numeral signal and the speed imitation signal through the magnifier in the front of the main plate, the S/D convertor, the SCM and so on. The utility model works under the closed situation and adopts the single phase excitation and the double phases output following method. Therefore the utility model has a high precision of convertor and strong anti interference capability; and moreover the utility model has a large measuring converting speed in moving measure.

Description

Closed-loop measuring ball induction ruler

The utility model belongs to the digital length measurement technology, is a kind of ball induction ruler that is used for the automatic control survey of telescopic arm.

The ball induction ruler is a kind of multistage induction sensing element, because the electromagnetism mean effort of multilevel hierarchy, so the output element precision is higher, and installation accuracy is relatively low, and is easy to adjust, reliable.

In the automatic control survey process of telescopic arm, generally adopt the ball induction ruler to carry out telescopic arm length and determine.Ball induction ruler measuring system is made up of with mainboard the machinery head as shown in Figure 1.The machinery head mainly contains scale and read head two major parts are formed, and removing these two parts also needs other annex could constitute complete measuring system, can be installed on the machine, and these annexes comprise scale support and protective device etc.Scale is that 1/2 inch nickel chromium triangle steel ball is formed by an accurate stainless steel cylinder and inner encapsulation diameter, and these ball warps are excessively conscientiously graded, to guarantee the consistance of steel ball magnetic characteristic and size.Read head is the rectangular aluminum box, includes by the big material of a rigidity and does skeleton, and the surface is wrapped with copper cash, is processed into multistage winding, can slide on scale.Also have the swiping device to keep sealing to prevent liquid, iron filings and dust enter.In gauge head, be evenly distributed four read heads, read four the tunnel respectively and differ 90 signals of spending.When passing to sinusoidal current in the gauge head winding, along with scale moves with respect to gauge head, its read head reads and is the electric potential signal that sinusoidal rule changes.

The ball induction ruler that uses is to work in a single-phase excitatory two-phase output times angle phase-detecting mode now, and its theory diagram is seen shown in Figure 2.Produce oscillatory signal by oscillator,, adjust oscillator signal through the clock signal of system generator.The signal of adjusting becomes measuring excited signal in the excited signal generator.Because this excited signal does not satisfy measurement requirement, therefore, through signal amplifier excited signal is amplified again.Excited signal is input to multistage winding, reads signal by read head in the measuring process, exports four road signals at head after read head reads and is merged into one road HV signal, passes through a series of processing of circuit again.Because adopt open loop approach to handle, there is higher dynamic measurement error in existing ball induction ruler in measurement, and can not carry out kinetic measurement, limits it and be applied in the automatic control closed-loop fashion measurement.

The utility model works in closed loop, adopted single-phase excitatory, the tracking amplitude discrimination metering system of two-phase output, purpose provides a kind of conversion accuracy height, anti-environmental interference ability is strong, simultaneously under kinetic measurement, have the closed-loop measuring ball induction ruler of very big measurement slewing rate, and provide rate signal and at the dynamic error of single-phase excitatory existence, this mode has the good restraining effect.

The utility model is made of machinery head and mainboard.Include scale, inductive coil, read head, magnetizing coil, steel cylinder, steel ball and amplifier etc. in the machinery head.The formation of mainboard as shown in Figure 3, by the excited signal device, prime amplifier, S/D converter, compositions such as single-chip microcomputer and I/O interface.

Excited signal device of the present utility model produces a phase excited signal, and a phase excited signal is read by read head.Four read heads carry out two-phase for 0 °～180 ° and 90 °～270 ° and read output, and expression formula is:

u _s=k _uU _mSin θ cos ω t, u _c=k _u.U _aIn the cos θ sin ω t formula, k _uBe voltage transfer coefficient, u _aBe stator winding induced potential maximal value, θ is the corner (electrical angle) with respect to zero-bit, and ω is the excitation power supply angular frequency.

The signal amplitude of above-mentioned two-phase output in carrying out the S/D transfer process, need be amplified to signal three orders of magnitude in the mv magnitude, reaches the V magnitude.Therefore, the utility model utilizes prime amplifier with two phase signals u before the S/D conversion _sAnd u _cEnter processing and amplifying.Signal through prime amplifier is handled is expressed from the next: u _Si=k _vK _uU _mCos ω t, u _Ci=k _vK _uU _mCos ω tcos θ, k in the formula _vBe enlargement factor.

S/D converter of the present utility model is by the high speed sine and cosine multiplier, error amplifier, high frequency filter, phase-sensitive demodulator, voltage controlled oscillator (VCO), up-down counter, compositions such as latch and D/A digital interface.U through the prime amplifier processing _SiAnd u _CiIn the input high speed sine and cosine multiplier, from the high speed sine and cosine multiplier, pass through after the signal multiplication, enter in the error amplifier, obtain error function between input value and the output valve, again successively by high frequency filter and phase-sensitive demodulator, send into voltage controlled oscillator, arrive up-down counter then.A signal part turns back to the high speed sine and cosine multiplier in up-down counter, forms closed loop.Another part is transported to latch.Divide two parts output in latch, a part is transported to single-chip microcomputer and carries out the output of length numeral, and another part is by the laggard line speed simulation of D/A interface output.

Through the high speed sine and cosine multiplier time, this multiplier is with output signal u _SiAnd u _CiWith the measuring system output valve

Corresponding cosine and sine signal multiplies each other, and promptly the cosine and sine signal of length L correspondence multiplies each other, and obtains following signal: $u_a=u_{\mathrm{si}}\cos \mathrm{\φ}=k_v{k}_u{u}_a\·\cos \mathrm{\ωt}\·\sin \mathrm{\θ}\cos \underset{-}{\overset{-}{\mathrm{\φ}}},$ $u_b=u_{\mathrm{ci}}\sin \mathrm{\φ}=k_v{k}_u{u}_m\·\cos \mathrm{\ωt}\·\sin \mathrm{\θ}\sin \underset{-}{\overset{-}{\mathrm{\φ}}}.$

With u _a, u _bSend in the error amplifier, can obtain the error function between input value and the output valve,, utilize this error function feedback that the good restraining effect is arranged at the dynamic error of single-phase excitatory existence:

u _e=k _e(u _a-u _b)=k _ek _vk _u((in the formula of θ-φ): k is k to θ-φ)=ksin ω tsin to sin ω tsin _ek _vk _uu _mProduct, k _eFor the amplification coefficient of error amplifier with u _eAfter sending into High frequency filter phase demodulation link, obtain with

The error signal Δ θ that is directly proportional, after error signal behind the phase demodulation handled, send into voltage controlled oscillator (VCO), the output pulse of voltage controlled oscillator adds in the up-down counter, obtains reflecting the output length signals L of ball induction ruler length scale at the output terminal of up-down counter.

Be used to load the closed-loop control of telescopic arm displacement transducer on the transport vehicle below according to the utility model, be described in further detail the utility model.

The quality of the excited signal of ball induction ruler directly has influence on the performance of its output signal, and then further has influence on measuring system, measuring accuracy.If excitation voltage exists under the distortion situation, the ratio of certain harmonic voltage point paired fundamental voltage composition is through the ball chi, will be in its output voltage in the overtone order increase that is directly proportional, promptly the output voltage degree of distortion will be greater than the excitation voltage degree of distortion, thereby excited signal must guarantee than low distortion.It is 2KHz that the utility model requires this signal frequency---between the 5KHz, amplitude is the sine wave between the 2V-5V.Pumping signal produces and is made up of following two parts in this embodiment:

The design of generation of low distortion signal and low distortion effect.

Vibration produces the cosine and sine signal that degree of distortion is very low for low distortion signal general using high precision RC network, utilizes low distortion amplifier output again.But because frequency values is determined by discrete component, poor stability, if require stability high, generally select for use the crystal oscillator frequency-division filter method to form sine wave, owing to have the larger proportion harmonic component in the waveform that this mode produces, thereby degree of distortion requires to need multiple-stage filtering to eliminate when very low, and this is influence output sinusoidal magnitude value stability easily.Take all factors into consideration and select for use the accurate function generator of ICL8038 monolithic to produce sine wave, amplify output through one-level low distortion amplifier again.Entire circuit is excited signal generation circuit as shown in Figure 5.The sinusoidal wave amplitude that is produced by this generator is 0.5V～0.8V.

After obtaining the low distortion signal, consider the design of low distortion effect.

Because of ball induction ruler input resistance only is 7.2 Ω, therefore when the input voltage amplitude is 4V, nearly 0.6A electric current is arranged, must be through power amplification, behind the general power amplifier, signal might distortion.Therefore select video power amplifier LM380 amplifier for use, as shown in Figure 6.Fig. 6 is expressed as excited signal power amplifier structure figure.After power amplification, excited signal has increased 4 times～6 times.

Because the signal that reads from read head is the millivolt magnitude, and is therefore harsh to the prime amplifier requirement, must be able to amplify weak signal, have very strong anti-electromagnetic interference capability simultaneously.Fig. 7 is the utility model prime amplifier structural representation.

S/D converter of the present utility model is a part crucial in the measuring system circuit, and its conversion accuracy, slewing rate directly have influence on the dynamic and static characteristic of measuring system, can adopt the S/D transfer principle, as shown in Figure 8 with the AD2S84 conversion chip of AD company.

In the utility model, following the tracks of amplitude discrimination formula metering system because A/D adopts, is a kind of increment counting mode, and promptly electrical angle is 0 °～360 °, chip is finished once conversion, scale is crossed a ball with respect to read head, promptly 1/2 inch, utilizes A/D digital signal interface direction signal, periodically clock output, be input to Single Chip Microcomputer (SCM) system and count, proofread and correct interface.As shown in Figure 9, single-chip microcomputer is finished output of length numeral and velocity simulate output.The utility model has the advantages that dynamic perfromance is good, carries out following analysis to the foregoing description.The big input speed 1000mm/s of native system index request amount ², acceleration constant K _A=6f ² _BW=6.520 ²=7.6 * 10 ⁶So hysteresis error (maximum) is measured in its output: $\mathrm{\Δ\φ}=\frac{1000\×{10}^3}{1.6\×{10}^6}=0.625\mathrm{\μm}$

Its step response characteristic such as Figure 10, ordinate represents to export length value among the figure, the horizontal ordinate express time.

It is one have an overshoot face rank damping response curve, t _rBe the rise time, its length depends on the maximum following rate of converter, t _DBe the overshoot time.Step response is t _sBe t _rWith t _DSum, after its expression had just applied, converter can draw the pin-point reading required time. $T_r=\frac{1}{f_{\mathrm{BW}}}---t_s=\frac{5}{f_{\mathrm{BW}}}\·\frac{R}{12}\left(8\right)$ R is a conversion value in the formula, native system R=12

T then _rBe about 1.9ms, t _sBe about 9.6ms

In sum, the method applied in the present invention has changed that ball chi dynamic measurement error was big in the past, the problem that can't dynamically use.

Claims (4)

1, a kind of closed-loop measuring ball induction ruler, form by machinery head and mainboard two parts, the machinery head includes scale, inductive coil, read head, magnetizing coil, steel cylinder, steel ball etc., it is characterized in that on the machinery head, also being placed with amplifier, this amplifier amplifies the signal that read head reads, four read heads carry out two-phase output with a mutually excitatory letter at 0 °～180 ° and 90 °～270 °, mainboard comprises the excited signal device, prime amplifier, the S/D converter, single-chip microcomputer and I/O interface, signal after prime amplifier amplifies is input in the S/D converter to be handled, and enters single-chip microcomputer and I/O interface afterwards; Described S/D converter includes the high speed sine and cosine multiplier, error amplifier, high frequency filter, phase-sensitive demodulator, voltage controlled oscillator, up-down counter, latch and D/A digital interface, two phase signals by the prime amplifier processing, import the high speed sine and cosine multiplier earlier, signal multiplication is after error amplifier becomes the error function signal, pass through high frequency filter more successively, phase-sensitive demodulator, voltage controlled oscillator, arrive up-down counter at last, one the tunnel returns the high speed sine and cosine multiplier in up-down counter, another road is transported to latch, the signal one tunnel that enters latch directly enters single-chip microcomputer and carries out the output of length numeral, and another road enters single-chip microcomputer by the D/A digital interface and carries out velocity simulate output.

2, closed-loop measuring ball induction ruler according to claim 1 is characterized in that the S/D converter selects the AD2S84 conversion chip for use.

3, closed-loop measuring ball induction ruler according to claim 1 is characterized in that the excited signal device comprises excited signal generator and excited signal power amplifier, and excited signal generator signal output frequency is 2KHz～5KHz, and amplitude is 2V～5V.

4, closed-loop measuring ball induction ruler according to claim 3 is characterized in that the excited signal generator selects the accurate letter generator of ICL8038 monolithic for use, and the excited signal power amplifier is selected the LM380 amplifier for use.

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