CN1173151C - Grid type displacement transducer - Google Patents

Abstract

The present invention relates to a grid type displacement sensor which comprises a moveable ruler and a fixed ruler. The present invention is characterized in that the numbers of grid lines of the fixed ruler and the moveable ruler are designed to be not equal, and a difference between the two numbers of grid lines is ued for greatly increasing the number of equivalent grid lines; the number lambada of equivalent grid lines satisfies the relational expression of lambada=NN'/n, wherein N represents the number of the grid lines of the movable ruler, and N' represents the number of the grid lines of the fixed ruler; N' is larger than N, and n represents the greatest common divisor of N and N'. Simultaneously, the present invention also utilizes the relation of the difference between the two numbers of grid lines of the movable ruler and the fixed ruler to eliminate errors of secondary periods except ni (i=1, 2,...) for greatly improving precision. The present invention alters the present situation that one grid line generates one pulse in the prior art and can obtain the highest resolution to precisely measure displacement by using few grid lines; the designed different-grid line displacement sensor has the advantages of easy processing, simple structure, low cost and strong resistance to interference.

Description

Grid formula displacement transducer

Technical field

The invention belongs to geometric sense precision measurement field, relate to a kind of displacement precision measurement apparatus.

Background technology

Grid formula displacement transducer commonly used often utilizes certain physical quantity cyclical variation clocklike in its motion process and forms equally distributed along the space " grid line ", thereby can obtain displacement by the counting to grid line.Utilize the light and shade of Moire fringe to change as grating, the NS pole field that the magnetic grid utilization is recorded changes, and the tooth grid utilize the tooth top teeth groove to cause the gauge head magnetic flux change, holds grid and utilizes the pole plate area change to cause the cyclical variation etc. of electric capacity.Existing grid formula displacement transducer, the density of moving chi and scale is identical, and the grid line number is identical in same distance in other words, and it is limited to be limited to the space incisure density, and resolving power is also limited, can not satisfy the engineering survey requirement.A common issue with that is grid formula sensor is that space grid line number is difficult to further raising, therefore must could satisfy the resolving power requirement that engineering is used to original signal is in addition electronic fine-grained again, this can cause system complex, the cost height, out of order possibility increases, to the harsh series of malpractice such as requirement of at the uniform velocity property proposition of moving.

Summary of the invention

The objective of the invention is to change the present situation of a pulse of one grid line generation in the prior art, can obtain higher resolution with less grid line, propose the amplification that a kind of difference of utilizing moving, scale grid line number realizes equivalent grating line number for this reason, promptly utilized less groove to realize the new sensor-difference wiregrating displacement transducer of more " equivalent grid line ".

For achieving the above object, technical scheme of the present invention is as follows,

A kind of grid formula displacement transducer, comprise moving chi and scale, with fixed, moving chi in 0-360 degree one circle scope or the grid line number in the equal length scope be designed to unequally, with their the increasing considerably of difference realization equivalent grating line number of grid line number, equivalent grating line number λ satisfies relational expression: $\mathrm{\λ}={\mathrm{NN}}^{\′}/n,$ Wherein N is moving chi grid line number, and N ' is a scale grid line number, and N '＞N, n are the highest common factor of N and N '.

Described grid formula displacement transducer, the signal stack of uniform n road, can eliminate except that ni (i=1,2 ...) inferior each second periodicity error in addition.

Described grid formula displacement transducer is characterized in that choosing of the wide dutycycle of grid line should be according to following results:

(1) works as S _N=0.5 o'clock, Y _(x)Amplitude A equal W _{N '}Wide kG of immediate special grid line with it (k=0,1 ..., the product of difference q) and highest common factor n, promptly

A＝|W _N′-Gk|·n(k＝0，1，…，q) (1)

(2) be that special grid line is wide when the scale grid line is wide $W_{{\mathrm{KN}}^{\′}}=\frac{G}{2}(2k-1)$ (k=1,2 ..., q) and S _N=0.5 o'clock, two chi overlap angle change curve Y _(x)Be shaped as triangular wave, it is maximum that amplitude A reaches, and

$A=\frac{G}{2}n----\left(2\right)$

Wherein the moving chi grid line of N-is counted N '-scale grid line number, and establishes the highest common factor of N '＞N n-N and N '

W _N-moving wide the duty of chi grid line angle W _{N '}The wide duty of-scale grid line angle

The S-dutycycle, S ∈ [0,1]

Equivalent grating line number G-resolving power after λ-amplification,

The total overlap angle of Y-two chis

Y _(x)-overlap angle change curve (ripple varied curve)

A-ripple varied curve amplitude (peak-to-peak value), A=Y _Max-Y _Min

Q-W _{N '}Particular value number correlation, $q=\frac{W_{N^{\′}\max }}{G}=\frac{N}{n}$

Below be example with the tooth grid, further specify technical scheme of the present invention:

1 utilizes the grid line difference to realize that equivalent grating line number increases

The tooth grid be the tooth top with inside and outside in-line gears always to overlap area be variable, constitute grid formula sensor thereby this variable can cause that the rule of electric weight such as electric capacity, inductance changes.

As shown in Figure 1, suppose to have a pair of inside and outside relative internal tooth 1-2 and external tooth 1-1, the inside and outside number of teeth is respectively 100, and tooth top width is identical with space width, respectively is 1/2 tooth pitch.When relative motion (unified for external tooth is fixed, internal tooth rotation), obviously two gears overlap total area maximum when interior external tooth aligns or claim to overlap fully, along with interior external tooth staggers gradually, this area reduces gradually, and overlap area when relative with teeth groove to tooth top is zero, strengthen gradually and form circulation, co-variationization is 100 times in one week of motion, so form 100 road grid lines.If interior external tooth is considered as two pole plates, this is the principle of capacitor grid transducer just also, the curve that capacitance C changes with angle as shown in Figure 2, W is the pitch angle, W=360 ° here/100=36 °.

And as shown in Figure 3, the number of teeth that we design external tooth 3-1 is 101, and the number of teeth of internal tooth 3-2 still is 100.If a certain moment, only tooth 1 and tooth 1 ' coincidence alignment (referring to that position, duty angle is at utmost approaching), then other all teeth all can not overlap fully, but have staggered 1/100,2/100 successively ..., 99/100 outer tooth pitch.When internal tooth rotates in 1/101 tooth pitch, only tooth 2 and tooth 2 ' align; Change tooth pitch in 1/101 again, only tooth 3 and tooth 3 ' align ..., so rotating 101 times promptly behind 1 interior tooth pitch, tooth 1 aligns with tooth 2, finishes a partial circulating, and behind 100 partial circulatings, i.e. 100 interior tooth pitches of internal tooth rotation are finished a systemic circulation after the week just.Therefore in this week, aligned condition takes place altogether 100 * 101=10100 time.If inside and outside two gears are used as two pole plates or are turned to two coils, then thereby the grid line number that 10100 cyclical variation formation similar to Fig. 2 amplified might take place and (why says " possible " in the electric capacity of between cog or inductance value in a week motion, though be because variation has taken place single tooth coincidence status, but can remain unchanged at the coincidence total area of two gears in some cases, this is much relevant with the ratio that the pre-teeth groove of tooth accounts for, and the back will go through).

Comparison diagram 1 and Fig. 3, just more common groove and difference line formula groove, as can be seen: under identical mechanical incisure density situation, the latter has obtained than the former much bigger equivalent grating line number.

2 utilize different grid line differences to improve precision

Be not difficult to find out that Fig. 1 overlaps the cyclical variation of area, take place simultaneously at all interior 100 teeth equably to have average effect, obvious benefit is arranged improving precision.And the coincidence area cyclical variation of Fig. 3 all occurs on the tooth at every turn, and the particular location of this tooth is to pursue the tooth alternation against the sense of rotation of annular wheel.Owing to do not possess average effect, the machine-building error will reflect out and out, and precision is relatively poor.The method of remedying is to adjust the number of teeth.

The number of teeth is 4 in for example getting, and the outer number of teeth is 6, then will have 2 tooth and hairs to give birth to the situation of alignment simultaneously at every turn, and as shown in Figure 4, and 180 ° of 2 tooth mutual deviations, the particular location of these 2 teeth by the tooth alternation, but remains 180 ° of mutual deviations against the sense of rotation of annular wheel.In this case, (every through 30 ° of generations once) will take place 4 * 6/2 times in the cyclical variation that overlaps area in a week, and promptly equivalent grating line number is 12 lines/week.

The number of teeth is 8 in for example getting again, and the outer number of teeth is 12, then will have 4 tooth and hairs to give birth to the situation of alignment simultaneously at every turn, and 90 ° of 4 tooth mutual deviations, and the particular location of these 4 teeth by the tooth alternation, but remains 90 ° of mutual deviations against the sense of rotation of annular wheel.In this case, the cyclical variation that overlaps area will take place 8 * 12/4 times in a week, and promptly equivalent grating line number is 24 lines/week.

From above two examples as can be seen, suitably select the number of teeth, can obtain the effect of many read heads diameter reading, thereby geometric errors such as foozle and setting-up eccentricity are played the good restraining negative function.

The wide duty ratio calculation method of 3 grid lines

Can find that in actual design the difference grid have the rule of many uniquenesses.Can determine anodontialy to align simultaneously or have how many teeth to align simultaneously as the selection of the number of teeth and number of teeth difference, thereby precision and equivalent grating line number have been produced material impact; The selection of the facewidth can determine to overlap the total area for another example no change, change size and Changing Pattern, thereby to waveform generation material impact of electrical signal of reaction or the like.It derives as follows in detail:

I) definition

Number N of teeth in the N-'-the outer number of teeth, and establish the highest common factor of N '＞N n-N and N '

W _N-Nei facewidth duty angle W _{N '}-outer facewidth duty angle

The S-dutycycle, S ∈ [0,1]

Equivalent grating line number G-resolving power after λ-amplification,

The total overlap angle of Y-two gears replaces above-mentioned coincidence area to represent the cyclical variation of physical quantity with the coincidence angle.

Y _(x)-overlap angle change curve (ripple varied curve)

y _i-Di i overlaps the relative angular displacement of angle x-two gears to gear

A-ripple varied curve amplitude (peak-to-peak value), A=Y _Max-Y _Min

Q-W _{N '}Particular value number correlation, $q=\frac{W_{N^{\′}\max }}{G}=\frac{N}{n}$

W _{K ' N '}-special facewidth value

Ii) conclusion

(1) highest common factor as N and N ' is n, then equivalent grating line number $\mathrm{\λ}={\mathrm{NN}}^{\′}/n,$ Be Y _(x)Cycle in a week changes number

Inferior.

(2) highest common factor of N and N ' is n, then has n identical to the coincidence status of tooth in rotation process, this n to the position of tooth with rotating alternation (clockwise moving direction or de-rotation direction) successively, always but remain in the geometry symmetric position of 360 °/n of mutual deviation.

This conclusion is extremely important, if n=2, just is equivalent to 2 read head diameter readings, can eliminate except that 2i (i=1,2 ...) inferior each second periodicity error in addition; If n=4 just is equivalent to 4 read head diameter readings, can eliminate each the second periodicity error except that 4i time; Uniform n road signal stack can be eliminated each the second periodicity error except that ni time ^[2]So, can cause good negative function to manufacturing and alignment error.And adverse effect is that n is big more, and λ is more little for equivalent grating line number.

(3) when the outer facewidth be the special facewidth $W_{{\mathrm{KN}}^{\′}}=\frac{G}{2}(2k-1)$ (k=1,2 ..., q) and S _N=0.5 o'clock, two gear overlap angle change curve Y _(x)Be shaped as triangular wave, it is maximum that amplitude A reaches, and

$A=Y_{\max }-Y_{\min }=\frac{G}{2}n----\left(1\right)$

From helping the angle of picking up signal, we wish that A is the bigger the better, and can obtain bigger electric capacity or inductance variable quantity, thereby obtain stronger electric signal.

(4) when the outer facewidth $W_{N^{\′}}\≠\frac{G}{2}(2k-1)$ (k=1,2 ..., q) and S _N=0.5 o'clock, Y _(x)Amplitude A equal W _{N '}Immediate special facewidth kG with it (k=0,1 ..., the product of difference q) and highest common factor n, promptly

A=|W _{N '}-Gk|n (k=0,1 ..., q) (3) and along with W _{N '}Immediate special facewidth value W with it _{KN '}Difference is more and more littler, and the overlap angle change curve will gradually become triangular wave by pulsating wave, and amplitude A is increasing.

Above-mentioned conclusion provides theoretical foundation for the number of teeth, choosing of the facewidth in the difference wiregrating sensor design.In the actual design, take into account equivalent grating line number and many read heads diameter reading and the choose reasonable number of teeth.The number of teeth should be chosen the facewidth that meets conclusion (3) after determining as far as possible.

More than describing with the measurement of angle is example.If line measurement, the groove mode and the vernier caliper of difference grid are similar, but vernier caliper need lean on the alignment of naked eyes identification groove, and the difference grid then can also show with rolling counters forward by sending more umber of pulse.Therefore above-mentioned poor wire grid principle is applicable to the measurement of straight-line displacement fully.

The present invention obtains higher resolution with less grid line and carries out the displacement precision measurement, and the poor wiregrating displacement transducer that designs with this invention is easy to processing, simple in structure, with low cost, strong interference immunity.

Description of drawings

Fig. 1: tooth gate sensor, 1-1-external tooth 1-2-internal tooth;

Fig. 2: capacitor grid transducer capacitance variations curve, W-pitch angle;

Fig. 3: difference wiregrating displacement transducer, 3-1-external tooth 3-2-internal tooth;

Fig. 4: the example that 2 teeth align simultaneously;

Fig. 5: difference wiregrating angular displacement sensor, 5-1-fixed gear 5-2-moving gear.

Fig. 6: difference wiregrating linear displacement transducer, 6-1-scale 6-2-moves chi.

Embodiment

As shown in Figure 5, the design fixed gear 5-1 number of teeth is 100, and the moving gear 5-2 number of teeth is 96, n=4 then, equivalent grating line number λ=100 * 96/4=2400 line/week, diameter 4 read head readings, eliminated remove 4i (i=1,2 ...) inferior each second periodicity error in addition.Choose suitable moving, fixed gear tooth top width by the wide duty ratio calculation method of grid line, moving fixed two gears are used as two pole plates or are turned to two coils, thereby then the grid line number that 2400 the cyclical variation formation similar to Fig. 2 has been amplified takes place in the electric capacity of between cog or inductance value in week motion.According to said method She Ji poor wiregrating displacement transducer has been eliminated each the second periodicity error except that 4i time, resolution G=0.15 °, has promptly realized that with the grid line that is not more than 100 common grid formula displacement transducer needs the resolution that just can reach with 2400 grid lines.

As shown in Figure 6, the design scale 6-1 number of teeth is 104, and the moving chi 6-2 number of teeth is 96, n=8 then, equivalent grating line number λ=104 * 96/8=1248 line/L, diameter 8 read head readings, eliminated remove 8i (i=1,2 ...) inferior each second periodicity error in addition.Choose suitable inside and outside tooth top width by the wide duty ratio calculation method of grid line, inside and outside two gears are used as two pole plates or are turned to two coils, thereby then the grid line number that 1248 cyclical variation formation similar to Fig. 2 has been amplified takes place in the electric capacity of between cog or inductance value in week motion.According to said method She Ji poor wiregrating displacement transducer has been eliminated each the second periodicity error except that 8i time, and has realized that with the grid line that is not more than 104 common grid formula displacement transducer needs the resolution that just can reach with 1248 grid lines.

Claims (3)

1. grid formula displacement transducer, comprise scale and moving chi, it is characterized in that: fixed, moving chi in 0-360 degree one circle scope or the grid line number in the equal length scope unequal, the difference of their grid line number has realized increasing considerably of equivalent grating line number, equivalent grating line number λ satisfies relational expression: $\mathrm{\λ}={\mathrm{NN}}^{\′}/n,$ N is moving chi grid line number, and N ' is a scale grid line number, and N '＞N, n are the highest common factor of N and N '.

2. the described grid formula of claim 1 displacement transducer is characterized in that with uniform n road signal stack, eliminate remove ni (i=1,2 ...) inferior each second periodicity error in addition.

3. according to the described grid formula of claim 1 displacement transducer, it is characterized in that choosing of the wide dutycycle of grid line should be according to following results:

(1) works as S _N=0.5 o'clock, Y _(x)Amplitude A equal W _{N '}Wide kG of immediate special grid line with it (k=0,1 ..., the product of difference q) and highest common factor n, promptly

A＝|W _N′-Gk|·n(k＝0，1，…，q) (1)

(2) be that special grid line is wide when the scale grid line is wide $W_{{\mathrm{KN}}^{\′}}=\frac{G}{2}(2k-1)$ (k=1,2 ..., q) and S _N=0.5 o'clock, two chi overlap angle change curve Y _(x)Be shaped as triangular wave, it is maximum that amplitude A reaches, and

$A=\frac{G}{2}n---\left(2\right)$

Wherein the moving chi grid line of N-is counted N '-scale grid line number, and establishes the highest common factor of N '＞Nn-N and N '

W _N-moving wide the duty of chi grid line angle W _{N '}The wide duty of-scale grid line angle

The S-dutycycle, S ∈ [0,1]

Equivalent grating line number G-resolving power after λ-amplification,

The total overlap angle of Y-two chis

Y _(x)-overlap angle change curve (ripple varied curve)

A-ripple varied curve amplitude (peak-to-peak value), A=Y _Max-Y _Min

Q-W _NParticular value number correlation, $q=\frac{W_{N^{\′}\max }}{G}=\frac{N}{n}$

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