JP3629242B2 - Magnetic encoder and its harmonic error reduction method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic encoder capable of reducing harmonic errors and a method for reducing harmonic errors of the magnetic encoder.
[0002]
[Prior art and its problems]
Magnetic encoders are known as angle measuring means. An invention has been proposed in which this magnetic encoder is mounted as an angle measuring means such as a conventional surveying instrument, for example, a total station or theodolite. This type of magnetic encoder includes a magnetic drum that rotates together with the collimating telescope and a magnetic sensor that detects a rotation angle of the magnetic drum. A multi-pole magnetic layer magnetized at an equal pitch with a division number N (N is a positive integer) is formed on the outer peripheral surface of the magnetic drum, and a magnetic sensor is disposed so as to face the multi-pole magnetic layer. The The magnetic sensor includes, for example, four magnetoresistive elements arranged at a pitch smaller than the pitch of the multipolar magnetic layer. Therefore, by detecting the resistance value of the magnetoresistive element that changes with the rotation of the magnetic drum, the rotation angle of the magnetic drum is measured with the pitch accuracy of the multipolar magnetic layer, and the angle between these pitches is interpolated. It can be measured by calculation.
[0003]
However, in the case of a magnetic encoder, the number of divisions of the multipolar magnetized layer cannot be increased as much as the optical encoder, and the pitch is large. Therefore, the division is caused by a dimensional error, a deviation of the magnetoresistive element from the ideal value, etc. There is a problem that the influence of the harmonic distortion within one pitch, that is, the harmonic error is large.
[0004]
OBJECT OF THE INVENTION
The present invention has been made in view of such a problem of the prior art, and an object thereof is to provide a magnetic encoder suitable for a surveying instrument and capable of reducing a harmonic error of an arbitrary order and a method for reducing the harmonic error. And
[0005]
SUMMARY OF THE INVENTION
To achieve this object, a magnetic encoder of the present invention includes a magnetic drum having a multi-pole magnetic layer magnetized at an equal pitch on the outer peripheral surface, and a plurality of magnets arranged opposite to the outer peripheral surface of the magnetic drum. A magnetic encoder that includes a sensor and outputs a detection signal that periodically changes according to a relative rotation angle when the magnetic sensor and the magnetic drum rotate relative to each other;
W magnetic sensors arranged at intervals shorter than one pitch of the multipolar magnetic layer so that the phase of the detection signal is shifted by θm so as to correct the harmonic error of an arbitrary order;
Two sets of signals Aout in the form of the output level (Vm) of the detection signal output from the w magnetic sensors when the magnetic drum and the magnetic sensor rotate relative to each other and the following equations (1) and (2). , Bout is obtained.
[Expression 1]
_{^{Aout = Σ w m = 1 Vm}} × sinθm
[Expression 2]
_{^{Bout = Σ w m = 1 Vm}} × cosθm
The calculated signals Aout and Bout are interpolated to obtain the rotation angle of the rotating unit.
Where m is the order (integer) of the harmonic error to be corrected, and θ is the electrical angle.
Further, the harmonic error reduction method of the present invention includes a rotating part having a multi-pole magnetized layer magnetized at an equal pitch on the peripheral surface, and a plurality of rotating parts arranged opposite to the outer peripheral surface of the rotating part. Is provided with a magnetic sensor that outputs a detection signal that periodically changes in accordance with its rotation angle, and each magnetic sensor is arranged at one pitch of the multipolar magnetic layer so as to correct a harmonic error of an arbitrary order. Are arranged so that the phases of the detection signals are shifted by θm, and the output levels (Vm) of the detection signals of the w magnetic sensors detected when the rotating unit rotates, Calculate as two vector signals Aout and Bout by the following formulas 1 and 2,
[Expression 1]
_{^{Aout = Σ w m = 1 Vm}} × sinθm
[Expression 2]
_{^{Bout = Σ w m = 1 Vm}} × cosθm
Furthermore, the calculated signals Aout and Bout are interpolated to obtain the rotation angle of the rotating unit.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings. FIG. 1 is a rear view showing a total station equipped with the magnetic encoder of the present invention with a part cut so that the main part of the magnetic encoder can be seen. FIG. 2 shows the total station with the main part of the magnetic encoder. FIG.
[0007]
As is well known, the total station 11 includes a bottom plate 13 for mounting on a tripod and the like, a leveling table (base unit) 17 supported on the bottom plate 13 by three leveling screws 15, and a leveling table 17. A U-shaped gantry (main body) 21 that is pivotally supported via a vertical shaft 19 and has a pair of struts 21a, and an altitude degree shaft 23 between two struts 21a of the cradle 21. A collimating telescope 25 and the like that are pivotally supported are provided. The altitude division axis 23 is fixed to the left and right of the collimating telescope 25 and is supported so as to be rotatable with respect to the two column portions 21a of the gantry 21. In FIG. Only the axis 23 is shown.
[0008]
The vertical shaft 19 is rotatably supported by a vertical bearing 27 fixed to the leveling table 17. And the base 21b which connects the support | pillar part 21a is being fixed to the upper end part of the vertical axis | shaft 19, and the stand 21 is supported by the vertical axis | shaft 19 so that rotation is possible. The altitude division shaft 23 is pivotally supported by an altitude division bearing 29 fixed to the pair of support columns 21 a of the gantry 21. In this way, the collimating telescope 25 is pivotally supported on the gantry 21 so as to be rotatable in the vertical direction via the altitude division axis 23, and further to the leveling gantry 17 so as to be rotatable in the azimuth direction via the gantry 21 and the vertical shaft 19. It is pivotally supported.
[0009]
Further, between the vertical shaft 19 and the vertical bearing 27, the relative rotation angle (horizontal angle) of the vertical shaft 19 (the collimating telescope 25 mounted on the gantry 21) with respect to the leveling table 17 (vertical bearing 27) is measured. A magnetic encoder 41 is mounted as a horizontal fraction, and the altitude division axis 23 and the gantry 21 have an altitude for measuring the rotation angle (altitude angle) of the altitude division axis 23 (collimation telescope 25) relative to the gantry 21. A magnetic encoder 51 is attached as a fraction. These magnetic encoders 41 and 51 are respectively arranged at predetermined intervals with respect to the magnetic drums 43 and 53 fixed to the bearing 27 and the shaft 23, and the multipolar magnetized layer formed on the outer peripheral surface of the magnetic drums 43 and 53. Magnetic sensor units 44 and 45 and magnetic sensor units 54 and 55 arranged in close proximity to each other are provided. In the present invention, the medium shape of the magnetic drums 43 and 53 is not limited to the illustrated embodiment, and includes a disk, cylinder, and columnar shape.
In this embodiment, in the magnetic encoder 41, the magnetic sensor units 44 and 45 rotate relative to the magnetic drum 43, and in the magnetic encoder 51, the magnetic drum 53 rotates relative to the magnetic sensor units 54 and 55. .
[0010]
Although not shown in detail, the signal processing means for detecting the output signals of the magnetic sensor units 44 and 45 and the magnetic sensor units 54 and 55 to determine the rotation angles of the magnetic encoders 41 and 51, that is, the horizontal angle and the altitude angle. The electronic circuit 61 (see FIG. 4) including the arithmetic means is mounted on the base 21b of the gantry 21. Operation panels 31 and 32 having a keyboard for operating and controlling the total station 11 and a display for displaying basic data and distance measurement results input by the keyboard are provided on both front and rear surfaces of the gantry 21. (See FIG. 2).
[0011]
1 and 2, reference numeral 33 is a hand grip for carrying the total station 11, and reference numeral 34 is a dust cover attached to the gantry 21 to protect the magnetic encoder 41 and a battery (not shown). Reference numerals 35 and 36 denote an eyepiece lens and an objective lens of the collimating telescope 25, respectively.
[0012]
The configuration of the magnetic encoders 41 and 51 will be described in detail. Since the basic configuration of the magnetic encoders 41 and 51 is the same, the configuration of one magnetic sensor unit 54 of one magnetic encoder 51 will be described with reference to FIGS. FIG. 3 is an enlarged view for explaining the relationship between each magnetic sensor of the magnetic sensor unit 54 of the magnetic encoder 51 and the multipolar magnetic layer 53a of the magnetic drum 53, and FIG. 4 is a diagram of a magnetoresistive element provided in the magnetic sensor. It is a wiring diagram which shows a connection. The magnetic sensor unit 54 is fixed to an angle 56 (see FIG. 1), and is fixed to the gantry 21 via the angle 56.
[0013]
On the outer peripheral surface of the magnetic drum 53, a multipolar magnetized layer 53a is formed that is magnetized at an equal pitch with a division number N (N is a positive integer). A magnetic pole pitch (interval between pole boundaries) of each magnetic pole 53aN of the multipolar magnetic layer 53a is λ. The electrical angle of the magnetic pole pitch λ is 2π. A magnetic sensor unit 54 is disposed so as to face the multipolar magnetized layer 53a with a predetermined gap. The magnetic sensor unit 54 includes eight magnetoresistive elements 4a1, 4b1, provided on a facing surface of a single planar substrate 54a and the planar substrate 54a facing the multipolar magnetized layer 53a, corresponding to a λ / 4 pitch. 4a2, 4b2, 4a3, 4b3, 4a4, 4b4. The magnetic sensor unit 54 is arranged so that a perpendicular line standing at the center thereof passes through the rotation center of the magnetic drum 53.
[0014]
When the magnetic drum 53 rotates, the magnetic encoder 51 detects a change in the resistance value of the magnetoresistive elements 4a1 to 4a4 and 4b1 to 4b4 depending on the change of the magnetic field 3 generated by the multipolar magnetic layer 53a. This is an incremental magnetic encoder that detects the rotation angle ω of the magnetic drum 53 at a λ / 4 pitch from a change in resistance value. An angle smaller than the λ / 4 pitch (fine rotation angle) is obtained by so-called interpolation calculation.
[0015]
As shown in FIG. 3, the eight magnetoresistive elements 4a1, 4b1, 4a2, 4b2, 4a3, 4b3, 4a4, 4b4 are composed of an A phase composed of four magnetoresistive elements 4a1 to 4a4 and four magnetoresistive elements. It is divided into B phase consisting of elements 4b1 to 4b4. The A phase magnetoresistive elements 4a1, 4a2, 4a3, 4a4 and the B phase magnetoresistive elements 4b1, 4b2, 4b3, 4b4 are alternately arranged, and the same phase magnetoresistive elements 4a1-4a4, 4b1-4b4. Are equal pitches of λ / 2, and the pitches between adjacent magnetoresistive elements of other phases are equal pitches of λ / 4.
[0016]
These A-phase and B-phase magnetoresistive elements 4a1 to 4a4 and 4b1 to 4b4 are bridge-connected as shown in FIG. That is, the magnetoresistive elements 4a1, 4a2 and the magnetoresistive elements 4a3, 4a4, the magnetoresistive elements 4b1, 4b2, and the magnetoresistive elements 4b3, 4b4 connected in series are connected in parallel, and the A phase terminals e ₀ , e ₁ are connected between the series resistors. And B phase terminals e ₀ ′ and e ₁ ′ are drawn out. The electronic circuit 61 applies a constant voltage V between the magnetoresistive elements connected in a bridge connection, and changes in voltage appearing at the A phase terminals e ₀ and e ₁ and the B phase terminals e ₀ ′ and e ₁ ′. A change in the magnetic field is detected based on (phase), and the rotation angle ω of the magnetic drum 53 is measured. That is, each rotation ω is measured by counting the number of phase changes.
[0017]
According to this embodiment, the resistance values a1, a2, a3, and a4 of the A-phase magnetoresistive elements 4a1 to 4a4 change according to the change of the magnetic field 3 acting by the rotation of the magnetic drum 53 as shown in the following equation. .
a1 = R ₀ + Rsin (Nω)
a2 = R ₀ + Rsin (Nω + π) = R ₀ −Rsin (Nω)
a3 = R ₀ + Rsin (Nω + 2π) = R ₀ + Rsin (Nω)
a4 = R ₀ + Rsin (Nω + 3π) = R ₀ −Rsin (Nω)
Here, ω is the rotation angle of the magnetic drum 53, R ₀ is the resistance value when there is no magnetic field, R is a coefficient (resistance ratio), and N is the number (number of divisions) of the multipolar magnetic layer 53a.
[0018]
Therefore, when the outputs of the terminals e ₀ and e ₁ are differentially amplified, the A-phase output Aout is
Aout = α × R × V / R ₀ × sin (Nω)
Where α is the amplification factor.
[0019]
Since the B-phase magnetoresistive elements 4b1 to 4b4 are arranged with a λ / 4 pitch shift with respect to the A-phase magnetoresistive elements 4a1 to 4a4, the outputs of the terminals e ₀ ′ and e ₁ ′ are differentially amplified. Then, the output Bout of the B phase is
Bout = α × R × V / R ₀ × cos (Nω)
It becomes.
[0020]
By detecting the zero cross point of the A-phase output Aout and the B-phase output Bout, the rotation angle of the magnetic drum 53 can be detected in units of 4 × N, that is, 360 / (4 × N) (°). In this way, the detection pitch is reduced to four times the division number N, and the resolution is increased. In surveying instruments, detection of an angle Δω smaller than (1 / N) / 4 is required, and a division number greater than or equal to N may be required. Therefore, the following interpolation calculation based on the outputs Aout and Bout of the A and B phases can increase the resolution by reducing the detectable detection pitch and increasing the detection pitch number without increasing the number of divisions. .
Δω = tan ⁻¹ (Aout / Bout)
[0021]
In the case of the above magnetic encoder, the number of divisions of the multi-pole magnetic layer cannot be increased as much as the optical encoder, and the pitch is large. Therefore, the division is caused by a dimensional error, a deviation of the magnetoresistive element from the ideal value, etc. The effect of harmonic errors (harmonic distortion) within one pitch is large. For this reason, it is very difficult to satisfy the demand for higher accuracy, and it is necessary to correct the harmonic error in order to satisfy it. To that end, the number of sensor units or magnetoresistive elements must be increased. . For example, according to the prior art, in order to correct one n-order harmonic error, it is necessary to prepare two sets of similar sensors and arrange the sensors so that the electrical angle is shifted by Π / n. In this case, 16 magnetoresistive elements that are twice the above eight are required, and in order to eliminate k harmonic errors, the magnetoresistive elements are required up to 2 ^k times. However, if the number of magnetoresistive elements is increased in one sensor unit, the width of the sensor unit is increased, and the influence of the curvature of the magnetic drum, that is, the difference in distance from the magnetic drum to the magnetoresistive element is likely to occur, and the error increases. There is a problem.
[0022]
Therefore, according to the embodiment of the present invention, w magnetoresistive elements are arranged with a phase difference (θm at an arbitrary interval) within one wavelength λ, that is, one pitch corresponding to an electrical angle 2π so as to correct a desired harmonic error. ) And the output change Vm with respect to the resistance change of the w magnetoresistive elements generated when the magnetic drum rotates is expressed by the following equations (1) and (2) as a vector-like A phase detection signal Aout, Calculated as the detection signal Bout.
[Expression 1]
_{^{Aout = Σ w m = 1 Vm}} × sinθm
[Expression 2]
_{^{Bout = Σ w m = 1 Vm}} × cosθm
Furthermore, an interpolation calculation is executed based on the calculated detection signals Aout and Bout to detect an angle (fine angle) Δω smaller than 2π / w pitch.
Δω = tan ⁻¹ (A / B)
[0023]
The embodiment will be further described with reference to FIGS. This embodiment is an example applied to the magnetic encoder of the total station shown in FIGS. 1 and 2, and FIGS. 5 and 7 show parts corresponding to FIG. In these drawings, members common to those in FIGS. 1 and 2 are denoted by the same reference numerals.
[0024]
The first embodiment shown in FIGS. 5 and 6 shows an arrangement structure of magnetoresistive elements for correcting first-order, second-order and third-order harmonic errors. The magnetic sensor unit 540 includes 12 magnetoresistive elements S ₁ , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , S ₈ , S ₉ , S ₁₀ , S ₁₁ , S _12. Has been. Each of the magnetoresistive elements S _{1 to} S ₁₂ is within one pitch (the pitch of the magnetic poles 53aN of the multipolar magnetic layer 53a) in which the outer peripheral surface is divided into N and N magnetic poles are formed (the pitch of the magnetic poles 53aN of the multipolar magnetic layer 53a). It is arranged in the sensor unit 540 so that an equal phase difference of π / 6 occurs within an electrical angle of 2π and 1 wavelength λ. That is, the interval between the magnetoresistive elements S _{1 to} S ₁₂ is π / 6. Therefore, when the magnetic drum 53 rotates, since the magnetoresistive elements _S 1 _{to S 12} are the magnetic field 3 undergo changes deviation [pi / 6 out of phase, the resistance value of the magnetic resistance elements _S 1 _{to S 12} is, [pi / 6 Phase shifts by 6 and changes. Therefore, the magnetoresistive elements S _{1 to} S ₁₂ are grounded via the respective reference resistors R ₀₁ and the reference voltage Vc is applied (see FIG. 6). Then, a digital value by A / D converter 63 the voltage at the connection point of the magnetoresistive element _S 1 _{to S 12} and the reference resistor _{R 01} as the output _{level, V 1, V 2, V} 3, V 4, V 5, V ₆ , V ₇ , V ₈ , V ₉ , V ₁₀ , V ₁₁ , V ₁₂ are converted. The digital values are averaged by the following formulas 3 and 4 to convert them into A-phase detection signal Aout and B-phase detection signal Bout, and at the same time, correct the first, second and third harmonic errors. doing.
[Equation 3]
_{^{Aout = Σ w m = 1 Vm}} × sinθm
sin θm = sin (2π / w × (m−1))
Aout = V ₄ −V ₁₀ +1/2 (V ₂ + V ₆ −V ₈ −V ₁₂ ) +3 ^−1/2 / 2 (V ₃ + V ₅ −V ₉ −V ₁₁ )
[Expression 4]
_{^{Bout = Σ w m = 1 Vm}} × cosθm
cos θm = cos (2π / w × (m−1))
Bout = −V ₁ −V ₇ +1/2 (V ₃ + V ₁₁ −V ₅ −V ₉ ) +3 ^1/2/2 (V ₂ + V ₁₂ −V ₆ −V ₈ )
_However, V 1 _{~V 12} is the absolute value of the difference voltage from the reference voltage Vc.
[0025]
The coarse rotation angle ω is obtained by counting the zero cross points of the digital signals Aout and Bout obtained by the above calculation.
[0026]
An angle (fine rotation angle) Δω smaller than ¼ pitch (phase difference π / 2) can be obtained by interpolating the calculated values Aout and Bout by the following formula.
Δω = tan ⁻¹ (Aout / Bout)
[0027]
In this embodiment, since the output levels of the magnetoresistive elements S _{1 to} S ₁₂ are A / D converted, the magnetic field difference due to the influence of the curvature of the magnetic drum 53 can be corrected for each magnetoresistive element. Errors caused by individual differences in magnetoresistive elements can also be corrected.
[0028]
A second embodiment of the magnetic sensor unit of the present invention is shown in FIG. This second embodiment is an embodiment where a plurality of magnetoresistive elements cannot be arranged in the electrical angle 2π in the magnetic sensor unit 541. In the second embodiment, each of the twelve magnetoresistive elements S _{1 to} S ₁₂ is an A phase group (magnetoresistance elements S ₁ , S ₃ , S ₅ , S ₇ , S ₉ , S ₁₁ ), It is divided into B phase groups (magnetoresistive elements S ₂ , S ₄ , S ₆ , S ₈ , S ₁₀ , S ₁₂ ), and the interval between the magnetoresistive elements of each A, B phase group is π / 3 in electrical angle, The interval between the A group and the B group is set to 2π + π / 6 in terms of electrical angle and is arranged within 4π. That is, the pitch of each of the magnetoresistive elements S ₁ , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , S ₈ , S ₉ , S ₁₀ , S ₁₁ , S ₁₂ is substantially π / 6
[0029]
These magnetoresistive elements S _{1 to} S ₁₂ are connected in the same manner as in the embodiment shown in FIG. The outputs of these magnetoresistive elements S _{1 to} S ₁₂ are each A / D converted by the A / D converter 63, and the digital value is substituted into the above equations 3 and 4 by the arithmetic circuit 65, so that the A phase And B-phase detection signals Aout and Bout are obtained by calculation, and an interpolation operation is executed based on the detection signals Aout and Bout to obtain a rotation angle.
[0030]
In the embodiment shown in FIG. 6, all the output signals of the magnetoresistive elements S _{1 to} S ₁₂ are used after A / D conversion. However, in the embodiment of the present invention, the output signal coefficients are the same. It is also possible to reduce the number of outputs and the A / D conversion processing amount by adding the resistance elements in an analog manner, that is, processing by connecting them in series. FIG. 8 shows an embodiment in which magnetoresistive elements having the same coefficients in Equations 5 and 6 are added in an analog manner. In the second embodiment relating to the connection of the magnetoresistive elements, the magnetoresistive elements S ₄ and S ₁₀ and the reference resistor R ₀₂ , the magnetoresistive elements S ₁ and S ₇ and the reference resistor R ₀₂ , the magnetoresistive elements S ₂ and S ₆ , S ₈ , S ₁₂ and reference resistor R ₀₂ , and magnetoresistive elements S ₃ , S ₅ , S ₉ , S ₁₁ and reference resistor R ₀₂ are connected in series, respectively. Are inserted in parallel between the constant voltage (Vc) terminal and the ground. Then, the output level (voltage) at the connection point between each reference resistor R ₀₂ and the magnetoresistive elements S ₁₀ , S ₇ , S ₁₂ , and S ₁₁ is taken out as outputs e ₁₁ , e ₂₁ , e ₃₁ , and e _41. The outputs e ₁₁ , e ₂₁ , e ₃₁ and e ₄₁ are converted into digital values by the A / D converter 63.
[0031]
The detection signals Aout and Bout are obtained by substituting e ₁₁ , e ₂₁ , e ₃₁ , and e ₄₁ converted into digital values into the following equations 5 and 6 corresponding to equations 1 and 2.
[Equation 5]
Aout = e ₁₁ +1/2 (e ₃₁ ) +3 ^−1/2 / 2 (e ₄₁ )
[Formula 6]
Bout = −e ₂₁ +1/2 (e ₄₁ ) +3 ^1/2 / 2 (e ₃₁ )
In addition, interpolation,
Δω = tan ⁻¹ (Aout / Bout)
To obtain an angle (fine rotation angle) Δω smaller than π / 6 by zero cross point detection of each element.
[0032]
As described above, according to the embodiment of the present invention, the twelve magnetoresistive elements S _{1 to} S ₁₂ corresponding to the first, second, and third orders to be corrected are replaced with 1 / (order × 2) of the electrical angle π. And two sets of detections having a vector-like phase difference by calculating the output levels (Vm) of the magnetoresistive elements S _{1 to} S ₁₂ by the formulas (1) and (2). Since the rotation angle of the magnetic drum 53 is obtained by obtaining the signals Aout and Bout and further substituting the detection signals Aout and Bout into the interpolation equation, the harmonics of a number of orders can be obtained without increasing the magnetoresistive elements. The error can be corrected. In addition, since the output signals of the magnetoresistive elements S _{1 to} S ₁₂ are first A / D converted, errors such as the influence of the curvature of the magnetic drum 53 can be easily and quantitatively corrected. Furthermore, since there is no need to provide a plurality of sensor units, it is not necessary to position the sensor units, and it is possible to prevent human error due to adjustment errors.
[0033]
In the present embodiment, the twelve magnetoresistive elements S _{1 to} S ₁₂ are arranged with a phase difference of π / 6 within one pitch and 2π of the multipolar magnetized layer 53a. The number and the phase difference are not limited to this.
[0034]
【The invention's effect】
As is apparent from the above description, the present invention provides each magnetic sensor with an interval shorter than one pitch of the multipolar magnetized layer so as to correct a harmonic error of an arbitrary order, and the phase of the detection signal. Are arranged so that they are deviated by θm, and the output levels (Vm) of the detection signals of the w magnetic sensors are obtained as two vector-like signals A and B by the equations (1) and (2), and the calculation is further performed. Since the signals A and B are interpolated to obtain the rotation angle of the rotating part, a large number of harmonic errors can be corrected with a small number of magnetic sensors.
[Brief description of the drawings]
FIG. 1 is a rear view showing a total station equipped with a magnetic encoder to which the present invention is applied, with a part cut so that the main part of the magnetic encoder can be seen.
FIG. 2 is a side view showing the total station with a part cut so that the main part of the magnetic encoder can be seen.
FIG. 3 is an enlarged view for explaining a relationship between a magnetic drum and a magnetic sensor of the magnetic encoder.
FIG. 4 is a circuit diagram showing an example of connection of magnetoresistive elements of the magnetic encoder.
FIG. 5 is a diagram showing a main part of a first embodiment of the magnetic encoder of the present invention applied to the total station shown in FIGS.
6 is a circuit diagram showing a first embodiment of connection of magnetoresistive elements in the magnetic encoder shown in FIG. 5; FIG.
FIG. 7 is a diagram showing a main part of a second embodiment of the magnetic encoder of the present invention applied to the total station shown in FIGS.
8 is a circuit diagram showing a second embodiment of the connection of the magnetoresistive element of the embodiment shown in FIGS. 5 and 7. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Total station 13 Bottom plate 15 Leveling screw 17 Leveling stand 19 Vertical axis 21 Mounting base 23 Altitude division axis 25 Collimating telescope 27 Vertical bearing 29 Altitude degree bearing 41 51 Magnetic encoder 43 53 Magnetic drum (rotating part)
53a Multi-pole magnetized layer 53aN Magnetic pole 44 54 Magnetic sensor unit 540 541 Magnetic sensor unit 61 Electronic circuit 63 A / D converter (A / D conversion means)
65 Arithmetic circuit (calculation means)
S ₁ S ₂ S ₃ S ₄ S ₅ S ₆ S ₇ S ₈ S ₉ S ₁₀ S ₁₁ S ₁₂ Magnetoresistive element (magnetic sensor)

Claims (11)

A magnetic drum having a multi-pole magnetic layer magnetized at an equal pitch on the outer peripheral surface; and a plurality of magnetic sensors arranged opposite to the outer peripheral surface of the magnetic drum, the magnetic sensor and the magnetic drum being relatively When rotating, the magnetic sensor outputs a detection signal that periodically changes according to the relative rotation angle,
W magnetic sensors arranged at intervals shorter than one pitch of the multipolar magnetic layer so that the phase of the detection signal is shifted by θm so as to correct the harmonic error of an arbitrary order;
The two sets of vector-like signals Aout by the output level (Vm) of the detection signal output from the w magnetic sensors when the magnetic drum and the magnetic sensor rotate relative to each other and the following equations (1) and (2). A magnetic encoder comprising a calculating means for obtaining Bout.

2. The magnetic encoder according to claim 1, wherein the calculating means further calculates the relative rotation angle by interpolating the calculated signals Aout and Bout. The interpolation operation is expressed by the equation tan ⁻¹ (Aout / Bout).
The magnetic encoder according to claim 2, wherein the calculation is performed by the following. 4. The magnetic encoder according to claim 2, wherein the magnetic sensor is a magnetoresistive element, and the magnetoresistive element is disposed on a single substrate. 5. The magnetic encoder according to claim 4, wherein an output signal of each of the magnetoresistive elements is A / D converted, and an interpolation operation is performed by the equations (1) and (2) based on the digital signals that have been A / D converted. 6. The magnetic encoder according to claim 5, wherein each digital signal after A / D conversion is corrected by a predetermined coefficient. The magnetic encoder according to claim 5 or 6, wherein output signals having the same coefficient in the equations (1) and (2) are added by analog processing, and the added output signals are A / D converted. The magnetic encoder according to claim 7, wherein the analog processing is to connect the corresponding magnetoresistive elements in series. The magnetism according to any one of claims 1 to 8, wherein the magnetic encoder is mounted on a surveying instrument equipped with a collimating telescope as an angle measuring device for measuring an altitude angle or an azimuth angle of the collimating telescope. Type encoder. A magnetic drum having a multi-pole magnetic layer magnetized at an equal pitch on the outer peripheral surface, and a plurality of magnetic sensors arranged opposite to the outer periphery of the magnetic drum, the magnetic sensor and the magnetic drum rotating relative to each other A method of reducing harmonic errors of a detection signal periodically changing according to the relative rotation angle, which is output by each magnetic sensor when
Each of the magnetic sensors is arranged so as to correct a harmonic error of an arbitrary order so as to have an interval shorter than one pitch of the multipolar magnetized layer and the phase of the detection signal is shifted by θm,
The output level (Vm) of the detection signal output from the w magnetic sensors when the magnetic drum and the magnetic sensor are rotated relative to each other, and two vector-like signals Aout, A method for reducing harmonic errors of a magnetic encoder, wherein Bout is calculated.

11. The method for reducing harmonic errors of a magnetic encoder according to claim 10, further comprising a step of interpolating the calculated signals Aout and Bout to obtain a rotation angle of the rotating unit.

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