TWI521188B - Error Correction Method for Position Detector - Google Patents

Description

Position detector accuracy correction method

The present invention relates to a method of correcting the accuracy of a position detector.

The inductosyn method of the electromagnetic induction type position detector is applied to a position detecting unit of various machines such as a working machine, an automobile, and a robot. The scale of the inductive synchronizer method includes a linear scale and a rotary scale. The linear scale is applied to, for example, a linear movement axis of a working machine to detect a moving position on the linear movement axis, and the rotary scale is used. The ruler is applied to, for example, a rotating shaft of a working machine to detect the angle of rotation of the rotating shaft.

Linear scales and rotary scales detect position by electromagnetic induction of coil patterns in parallel opposite configurations. The detection principle is explained based on the schematic diagram of FIG. Fig. 5 (a) is a perspective view showing a state in which a slider of a linear scale is aligned in parallel with a scale, and Fig. 5 (b) is a schematic view showing a pattern of the slider and the scale, Fig. 5 (Fig. 5 (b) c) is a graph showing the degree of electromagnetic coupling between the slider and the above scale. Furthermore, although the schematic diagram of the linear scale is shown in Figure 5, the principle of the rotary scale is the same, and the slider and scale of the stator and rotor of the rotary scale and the linear scale, respectively. The ruler corresponds.

As shown in FIGS. 5(a) and 5(b), the detecting portion of the linear scale includes a slider 11 as a primary member and a scale 12 as a secondary member. The slider 11 as the movable portion includes the first slider side coil 13 as the first primary side coil and the second slider side coil 14 as the second primary side coil, and the scale 12 as the fixed portion includes two The scale side coil 15 of the secondary side coil. The coils 13, 14, 15 are folded back in a zigzag manner (ie, formed into a comb-tooth pattern) and The body becomes linear. Further, the coils 13, 14, and 15 are equal in length to each other.

Further, as shown in Fig. 5 (a), the first slider side coil 13 and the second slider side coil 14 and the scale side coil 15 are in a state in which a gap g within a predetermined range is maintained therebetween. Parallel to the ground configuration. Further, as shown in FIGS. 5(a) and 5(b), the relationship between the first slider side coil 13 and the second slider side coil 14 and the scale side coil 15 is shifted by 1/4 pitch.

As a result, when the first slider-side coil 13 and the second slider-side coil 14 are supplied with an alternating current, the slider 11 is moved along the longitudinal direction of the scale 12 as indicated by the arrow A of FIG. 5(a). As shown in FIG. 5(c), the degree of electromagnetic coupling between the first slider side coil 13 and the second slider side coil 14 and the scale side coil 15 is based on the first slider caused by the movement of the slider 11. Since the relative positional relationship between the side coil 13 and the second slider side coil 14 and the scale side coil 15 changes periodically, the scale side coil 15 generates a voltage that periodically changes. Therefore, the position of the scale 12 (i.e., the position of the slider 11 with respect to the scale 12) can be detected based on the voltage.

Here, the first alternating current I _{s is} distributed to the first slider side coil 13 , and the second alternating current I _{c is} distributed to the second slider side coil 14 .

I _s =-I. Cos(kα). Sin(ωt)

I _c =I. Sin(kα). Sin(ωt)

Where I: the magnitude of the current

p: length of the pitch of the coil (angle in the rotary scale)

k: 2π/p

ω: the angular frequency of the alternating current

t: time

α: excitation position

In this case, if it is an ideal linear scale (or a rotary scale), the following voltage V is generated on the scale side coil 15.

V=K(g). I. Sin(k(X-α)). Sin(ωt)...(1)

Where K: depends on the coefficient of the gap g

X: Detection position of the scale (detection position of the slider relative to the length of the scale)

Further, the peak amplitude V _p of the voltage V of the above formula (1) is sampled to have the following values.

V _p = K(g). I. Sin(k(X-α))...(2)

Therefore, the excitation position α is controlled such that α = X, that is, V _p =0 follows the detection position X, and the value of the excitation position α at this time is referred to as the detection position X.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-254785

However, the actual linear scale (or rotary scale) may cause the relationship of the above formula (2) to be unsatisfactory due to manufacturing errors or assembly errors, and the error at the detection position X is accompanied.

Generally, the error occurs remarkably as the period of the coil pitch (pattern pitch) period/integer in the scale side coil, which is called an interpolation error.

The variation of the pattern due to the manufacturing error, or the change in the slope of the scale side coil and the slider side coil, causes the actual interpolation error not to be completely periodic, but becomes the pitch of each coil. Different people.

Therefore, there is a problem that it is difficult to remove the interpolation error even if the same correction value is used to correct all the coil pitches in the scale side coil.

In addition, in the method of correcting the interpolation error of each of the coil pitches in the scale side coil as in the above-described Patent Document 1, it takes extra time to correct the value by using the value, and it is impossible to correct the aging change due to the installation. The problem caused by the variation of the interpolation error.

Therefore, in the present invention, an object of the present invention is to provide a method of correcting the accuracy of a position detector which can easily perform interpolation error correction with a strong aging change.

The accuracy correction method of the position detector according to the first aspect of the present invention is characterized in that the primary side member of the object to be measured and the secondary side member serving as the measuring portion are disposed at a relative position of the second side member a certain speed or angular velocity is changed to thereby detect the position; and the relative position of the secondary member is stored in a distance from the nth stage of passing the object to be measured to the n+1th stage During the length or angle p, the time i in the range between the distances is detected in units of a certain time interval Δt. Δt (i is the natural number of the sample number 0 to N-1), the displacement amount G _n [i]; the time from the above-mentioned nth stage to the above p-th stage of the n+1th stage is set to T, According to S=p/T

To obtain the average speed or average angular velocity S, and according to _{E n [i] = G n} [i] -i. S. ΔtG _n [0]

Calculating an interpolation error E _n [i] within a distance between the nth stage and the (n+1)th stage; and setting the relative position of the current secondary side member, that is, the detection position as the mth stage When the detection position G _{m in the} range between the m+1th stages is reached and na≦m≦n+a (a is a predetermined integer), |G _m -G _n [i]| The minimum i=I interpolation error E _n [I], and according to X'=p. m+G _m -E _n [I]

The detection position X' which is the position from the zero point position of the object to be measured is obtained.

The accuracy correction method of the position detector according to the second aspect of the present invention is characterized in that, in the accuracy correction method of the position detector according to the first aspect of the invention, the interpolation error E is obtained by k (k: integer) times. _n [i] and find the average interpolation error E _na [i], which can be based on E _na '[i]=(E _n [i]+k.E _na [i])/(k+1)

The average interpolation error E _na '[i] including the above interpolation error E _n [i] is obtained, and the average interpolation error of i=I at which |G _m -G _n [i]| becomes the minimum is obtained. E _na '[I], and according to X'=p. m+G _m -E _na '[I]

The above detection position X' is obtained.

According to the accuracy correction method of the position detector of the first aspect of the invention, the relative position of the primary side member to be measured and the secondary side member as the measuring unit arranged at a constant pitch pattern is changed at a constant speed or an angular velocity. And detecting the position of the position; and remembering the relative position of the secondary member to move from the nth stage through the object to be measured to the length or angle p of the 1st step to the (n+1)th stage During the period, the time i in the range between the distances is detected in units of a certain time interval Δt. The displacement amount G _n [i] when Δt (i is the natural number of the sampling number 0 to N-1) sets the time of the above p from the nth stage to the n+1th stage to be T, Find the average velocity or average angular velocity S from S=p/T and according to E _n [i]=G _n [i]-i. S. ΔtG _n [0] finds the interpolation error E _n [i] within the distance between the nth stage and the (n+1)th stage, and the relative position of the current secondary side member, that is, the detection position When the detection position G _{m in the} range between the mth stage and the m+1th stage is set, and na≦m≦n+a (a is a predetermined integer), |G _m -G is obtained. _n [i]| becomes the smallest interpolation error E _i [I] of I=I, and according to X'=p. m+G _m -E _n [I] The detection position X′ which is the position from the zero point position of the object to be measured is obtained, so that the interpolation error correction with strong aging change can be easily performed.

According to the accuracy correction method of the position detector according to the second aspect of the invention, if the interpolation error E _n [i] is obtained k (k: integer) times and the average interpolation error E _na [i] is obtained, The average interpolation error E _na including the above interpolation error E _n [i] is obtained according to E _na '[i]=(E _n [i]+k.E _na [i])/(k+1) '[i], and find |G _m -G _n [i]| to become the smallest i=I average interpolation error E _na '[I], and according to X'=p. Since m + G _{m -} E _na '[I] finds the above-described detection position X', the more the operation is repeated, the more the correction accuracy is improved.

11‧‧‧Sliding parts

12‧‧‧ scale

13‧‧‧1st slider side coil

14‧‧‧2nd slider side coil

15‧‧‧Scale side coil

A‧‧‧ arrow

E _n [i]‧‧‧ interpolation error

G‧‧‧ gap

G _m ‧‧‧Detection location

G _n [i]‧‧‧ displacement

P‧‧‧ spacing

S1~S7‧‧‧ steps

T‧‧‧ time

t‧‧‧Time

X‧‧‧Detection location

X'‧‧‧Detection location

△t‧‧‧a certain time interval

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing the method of correcting the position detector of the first embodiment of the present invention.

Fig. 2 is a schematic view showing the relationship between the distance between the coils on the scale side, the detection position, and the stage.

Fig. 3 is a graph showing the relationship between the amount of displacement, time, and interpolation error in the range of the coil pitch.

Fig. 4 is a graph showing the relationship between the detected position and the error when the correction by the accuracy correction method of the position detector of the first embodiment of the present invention is performed.

Figure 5 is a schematic diagram of the scale of the inductive synchronizer mode. (a) is a perspective view showing a state in which the slider of the linear scale is parallel to the scale, (b) is a schematic diagram showing the slider and the scale, and (c) is the slide. A graph of the degree of electromagnetic coupling between the piece and the above scale.

The electromagnetic induction scale is electromagnetically coupled by a plurality of coils, so the coupling degree is averaged. Therefore, the distribution of the interpolation errors of the two coil pitches adjacent to each other is similar. Therefore, in the accuracy correction method of the position detector of the present invention, the correction is performed using the error of the coil pitch close to each other.

That is, in the accuracy correcting method of the position detector of the present invention, in the movement of the slider, the coil pitch is performed as follows: an error in the coil pitch close to the current position is obtained, and the interpolation error data is obtained (correction) Data), and use this data to make corrections within the coil spacing of the current position. Thereby, the positional dependence of the coil pitch of the interpolation error can be reduced and corrected.

Hereinafter, the accuracy of the position detector of the present invention will be described by way of an embodiment and using a schematic diagram. Correction method.

[Example 1]

The accuracy correction method of the position detector of the first embodiment of the present invention will be described with reference to the drawings. Figure 1 is a flow chart illustrating the method. 2 is a schematic view showing the relationship between the coil pitch, the detection position, and the stage. Further, Fig. 3 is a graph showing the relationship between the displacement amount, the time, and the interpolation error in the range of the coil pitch, and the horizontal axis represents the displacement amount G _n [i] in the range of the coil pitch (see below for details), and the vertical axis Indicates time t. Hereinafter, description will be made based on the flowchart of FIG. 1.

In step S1, in Fig. 2, the slider passes the nth stage of the scale side coil.

In step S2, in FIG. 2, the slider is moved from the nth stage through the scale side coil to the length p of the 1 pitch up to the adjacent (n+1)th stage, A certain time interval Δt is the time in the range of the coil pitch detected by the unit i. The displacement amount when Δt (i is the natural number of the sample number 0 to N-1) is set as the displacement amount G _n [i], and the displacement amount G _n [i] is memorized.

An example of the relationship between the above-described certain time interval Δt and the above-described displacement amount G _n [i] is shown as a black dot in the graph of Fig. 3 . The intervals on the vertical axis of the black dots are all Δt. Furthermore, as shown in the graph of Fig. 3, G _n [N] - G _n [0] = p, usually G _n [0] = 0.

In step S3, it is judged whether or not the time T (see FIG. 3) for moving the pth of the nth to the (n+1) thth time has not reached the predetermined time. When the predetermined time is not reached, the moving speed of the slider from the nth to the n+1th is regarded as high speed, and the process proceeds to step S4. When the time is longer than the predetermined time, the above moving speed is regarded as not being high speed, and the process returns to step S1.

In step S4, the interpolation error E _n [i] in the coil pitch of the nth stage to the (n+1)th stage is obtained by the following equation based on the average speed S=p/T.

E _n [i]=G _n [i]-i. S. ΔtG _n [0]

That is, the relationship between the ideal G _n [i] and Δt when the slider passes T at a certain speed becomes the oblique line in the graph of FIG. 3, but if it is the position of the black point in reality, When a line segment is drawn from the black dots to the solid line in the horizontal axis direction, the length of the line segment becomes the interpolation error E _n [i]. The program obtained by digitizing the program is the above formula.

In step S5, it is determined whether or not the interpolation error E _n [i] is equal to or less than a predetermined value. When the value is less than or equal to the predetermined value, the process proceeds to step S6. If the value is greater than the predetermined value, it is determined that the interpolation error as the scale side coil is too large (the error cannot be detected), and the process returns to step S1.

In step S6, if the interpolation error E _n [i] is obtained k times before and the average interpolation error E _na [i] is obtained, the interpolation error E _n may be obtained by the following equation. [i] average interpolation error E _na '[i] (interpolation error E _n [i] is always stored in EEPROM (Electrically Erasable Programmable Read Only Memory) It can also be used effectively after the power is restarted).

E _na '[i]=(E _n [i]+k.E _na [i])/(k+1)

In the method, the interpolation error data is obtained by the above steps S1 to S6. In addition, the above-mentioned "return to step S1" means that the next coil pitch is again performed from step S1.

In step S7, the correction of the detected position X is performed by the following procedure.

First, the detection position within the range of the detection position X and the coil pitch before correction can be simultaneously detected by the prior art. The position of the current slider, that is, the detection position is set as the detection position G _m within the range of the coil pitch from the mth stage to the m+1th stage, and the detection position from the zero position of the scale side coil before correction X is obtained by the following formula.

X=p. m+G _m

Here, in the mth stage of the scale side coil, it is close to the case where the nth stage of the interpolation error data, ie, na≦m≦n+a (a is a predetermined integer), has been obtained in steps S1 to S6. When it is found, |G _m -G _n [i]| becomes the smallest i. Wherein, the above a is preferably 1, that is, n=m±1, but when the interpolation error data cannot be detected when n=m±1, other interpolation error data is used, so it is expressed as “ Close". Further, as long as the interpolation error in the mth stage is obtained previously, a=0 may be used.

Then, the interpolation error E _n [I] of i=I in which the above |G _m -G _n [i]| is the smallest is obtained, and the zero-point position of the corrected scale side coil is obtained by the following equation. Detection position X'.

X'=p. m+G _m -E _n [I]

Wherein, in the step S6 is inserted to obtain the average error E _na 'when [i] of the case, to obtain _{| G m -G n [i]} | of i = the smallest interpolation error E _na of the average I' [I] Then, the detection position X' which is the position from the zero point position of the corrected scale side coil is obtained by the following equation.

X'=p. m+G _m -E _na '[I]

4 is a graph showing the relationship between the detected position and the error when the method is used for correction, wherein the horizontal axis represents the actual detected position, and the vertical axis represents the error between the actual detected position and the detected position X, X'. The solid line in the graph is the data about X', and the dotted line in the graph is the data about X. As shown in the graph, the error between the corrected detection position X' and the actual detected position is reduced as compared with the detection position X before correction.

Further, in the procedures of the above-described steps S1 to S7, the method for performing the operation for correction is not intentionally performed, but in this method, the correction accuracy is increased as the operation history is increased. In the case where the correction accuracy is so dependent on the operation history record, the operation for correcting may be performed by moving the entire stroke at a constant speed at a high speed.

Further, although the method has been described in the case of applying the method to a linear scale, it can of course be applied to a rotary scale. In the case of application to a rotary scale, the slider may be replaced by a stator, the scale may be replaced by a rotor, the length may be replaced by an angle, and the speed may be replaced by an angular velocity.

If further explained, the application object of the method is not limited to the scale of the electromagnetic induction type position detector, that is, the inductive synchronizer mode.

For example, in the optical encoder disclosed in Fig. 5 of Japanese Patent Laid-Open No. Hei 4-125409, the above steps S1 to S7 can be applied. At this time, the above sliders are respectively replaced with light sources. 11. The collimator lens 12, the index scale 16, and the light receiving element 17 replace the scale side coil with the grid 14 in the main scale 13, and replace the coil pitch with the pitch P between the grids 14. The movable portion of the optical encoder disclosed in FIG. 5 of Japanese Patent Laid-Open No. Hei 4-125409 is not a slider (light source 11, collimator lens 12, index scale 16 and light receiving element 17). The scale and the scale side coil (the grid 14 in the main scale 13).

As described above, the accuracy correction method of the position detector according to the first embodiment of the present invention has been described. However, the present method is a method for correcting the position detector in which the primary side of the object to be measured is arranged in a predetermined pitch pattern. The position of the member and the secondary member as the measuring portion is changed at a constant speed or an angular velocity to detect the position; and the relative position of the secondary member is stored to move from the object to be measured During the period from the n stages to the length of the 1st pitch or the angle p up to the n+1th stage, the time i in the range of the distance is detected in units of a certain time interval Δt. The displacement amount G _n [i] when Δt (i is the natural number of the sampling number 0 to N-1) sets the time of the above p from the nth stage to the n+1th stage to be T, The average velocity or average angular velocity S is obtained from S=p/T and is based on E _n [i]=G _n [i]-i. S. ΔtG _n [0] finds the interpolation error E _n [i] within the distance between the nth stage and the (n+1)th stage, and the relative position of the current secondary side member, that is, the detection position When the detection position G _{m in the} range between m stages and m+1th stages is in the range of na≦m≦n+a (a is a predetermined integer), |G _m -G _n [i] is obtained. ]| becomes the minimum interpolation error E _n [I] of i=I, and according to X'=p. m + G _{m -} E _n [I] The detection position X' which is the position from the zero position of the object to be measured is obtained.

Therefore, in the present method, since the position detector itself is corrected, it is not necessary to use the position detector as the reference, and the operation for correcting is not required, so that the interpolation error correction can be easily performed. Moreover, interpolation error correction with strong aging changes can be performed. Further, it is possible to perform the correction depending on the position, and the effect of the correction can be further exerted.

Further, in the present method, as long as the interpolation error E _n [i] is obtained by k (k: integer) times and the average interpolation error E _na [i] is obtained, E _na '[i ]=(E _n [i]+k.E _na [i])/(k+1) finds the average interpolation error E _na '[i] including the above-described interpolation error E _n [i], and Find the average interpolation error E _na '[I] of |G _m -G _n [i]| which becomes the smallest i=I, and according to X'=p. m + G _{m -} E _na '[I] find the above-described detection position X'.

Thereby, in the present invention, the interpolation error data is sequentially updated, so that the more the operation is repeated, the more the correction accuracy is improved.

[Industrial availability]

The present invention is preferably used as a method of correcting the accuracy of the position detector.

S1~S7‧‧‧ steps

Claims (2)

A method for correcting accuracy of a position detector is characterized in that the position detector arranges a relative position of a primary side member to be measured and a secondary side member as a measuring portion at a constant speed or angular velocity in a predetermined pitch pattern. Changing, thereby detecting the position; and the method is: memorizing the relative position of the secondary member to move from the nth stage through the object to be measured to the n+1th stage During the length or angle p, the time i in the range between the distances is detected in units of a certain time interval Δt. Δt (i is the natural number of the sample number 0 to N-1), the displacement amount G _n [i]; the time from the above-mentioned nth stage to the above p-th stage of the n+1th stage is set to T, Find the average velocity or average angular velocity S from S=p/T and according to E _n [i]=G _n [i]-i. S. ΔtG _n [0] is used to obtain an interpolation error E _n [i] within the distance between the nth stage and the (n+1)th stage; and the relative position of the current secondary side member, that is, the detection position When the detection position G _{m in the} range between the mth stage and the m+1th stage is set, and na≦m≦n+a (a is a predetermined integer), |G _m -G is obtained. _n [i]| becomes the smallest interpolation error E _i [I] of I=I, and according to X'=p. m + G _{m -} E _n [I] The detection position X' which is the position from the zero position of the object to be measured is obtained. For the accuracy correction method of the position detector of claim 1, wherein the interpolation error E _n [i] is obtained by k (k: integer) times and the average interpolation error E _na [i] is obtained, E _na '[i]=(E _n [i]+k.E _na [i])/(k+1) finds the average interpolation error E _na ' including the above interpolation error E _n [i] [i], and find that |G _m -G _n [i]| becomes the smallest i=I average interpolation error E _na '[I], and according to X'=p. m + G _{m -} E _na '[I] find the above-described detection position X'.