JP5630660B2 - Magnetic displacement sensor and displacement detection method - Google Patents

Description

  The present invention relates to detection of displacement by a magnetic displacement sensor.

  The applicant has proposed a magnetic displacement sensor that detects a relative position between a row of permanent magnets and a row of coils arranged in parallel (Patent Document 1: JP4513673B). In this magnetic displacement sensor, the coil receives a magnetic field from the permanent magnet and changes its AC impedance, and the current flowing through the coil changes according to the phase based on the arrangement pitch of the permanent magnets. In contrast, the inventor has found that the output of the magnetic displacement sensor changes depending on the relative speed between the permanent magnet row and the coil row, and the influence of the relative speed is caused by the coil near the end of the permanent magnet row. I found something remarkable. As a countermeasure to this, it is not efficient to lengthen the permanent magnet row, and if the position of the moving body in the curve section is detected by a magnetic displacement sensor, even if a long permanent magnet row is provided, the curve Because of the curvature, it is difficult to face the coil row.

  Here is related prior art. In Patent Document 2 (JP2005-195391A), in order to cancel the electromotive force caused by the alternating current from the non-contact power supply line to the moving body, the winding method of the coil in the magnetic displacement sensor is reversed for each piece. The use of two opposite coils in parallel is disclosed. However, Patent Document 2 does not touch on the relative speed between the row of permanent magnets and the row of coils.

JP4513673B JP2005-195391A

  An object of the present invention is to prevent the relative speed between the row of permanent magnets and the row of coils from affecting the output of the displacement sensor, and to reduce the length of the row of permanent magnets.

The magnetic displacement sensor of the present invention detects displacement between a row of permanent magnets to be detected and a row of coils,
Along the detection direction of displacement, there are provided at least two rows of coils consisting of the same number of coils and having the same start and end position of the row along the detection direction of displacement, and a row of permanent magnets,
At least a pair of coils facing each other in the at least two rows of coils are connected in parallel to each other;
A power source for applying a voltage that changes according to sinωt is provided to the at least one pair of coils,
The current flowing through the at least one pair of coils is taken out as an output,
An influence on the output of the displacement sensor due to the relative speed between the row of permanent magnets and the row of coils and the magnetic field from the row of permanent magnets is canceled between the rows of the at least two rows of coils. It is characterized by that.

The displacement detection method of the present invention is a method of detecting displacement between a row of permanent magnets to be detected and a row of coils by a magnetic displacement sensor,
In the magnetic displacement sensor, there are at least two coil rows that have the same number of coils along the displacement detection direction and that have the same start and end positions along the displacement detection direction, and the permanent magnets. A column is provided,
At least a pair of coils facing each other in the at least two rows of coils are connected in parallel to each other;
A voltage that varies according to sinωt from a power source is applied to the at least one pair of coils,
Taking out the current flowing through the at least one pair of coils as an output,
The influence on the output of the displacement sensor due to the relative speed between the row of permanent magnets and the row of coils and the magnetic field from the row of permanent magnets is canceled between the rows of the at least two coils.

  The reason why the output of the magnetic displacement sensor depends on the relative speed is the induced electromotive force generated by the magnetic field from the permanent magnet and the current flowing through the coil. Here, when the length of the coil array is set to two permanent magnets, the direction of the magnetic field exerted on the coil is reversed between the first permanent magnet and the second permanent magnet, so that the induced electromotive force can be canceled. . However, at the end of the magnet row, the induced electromotive force cannot be canceled because, for example, only one permanent magnet faces the coil row. On the other hand, when two rows of coils are provided, the induced electromotive force can be canceled between the rows of coils depending on the direction of the current flowing through the coils and the winding method of the coils. For this reason, the relative speed does not affect the output of the magnetic displacement sensor, and the induced electromotive force is canceled between the coils facing each other, so that it is not necessary that the permanent magnet row completely overlaps the coil row. The magnet row can be shortened. In this specification, the description regarding the magnetic displacement sensor also applies to the displacement detection method as it is, and the description regarding the displacement detection method also applies to the magnetic displacement sensor as it is.

  Preferably, the at least two coils are arranged in the same manner in which the coils facing each other are wound in the opposite direction, or in the opposite direction, or in opposite directions in which the opposite coils are wound. . For example, if the direction of the current is reversed with the same winding method by differential connection, the direction of the induced electromotive force is reversed. In addition, for example, even if the opposite direction of winding is reversed and the direction of current is the same due to the summing connection, the direction of the induced electromotive force is reversed.

Preferably, the at least two coils are arranged in the order of a first coil, a second coil, a third coil, and a fourth coil, each row including four coils.
The first to fourth coils are arranged in the length of one permanent magnet in the row of permanent magnets,
In the at least two coil rows, dummy coils are provided at both front and rear ends of each row, and when viewed from the first coil, the first dummy coil is on the opposite side of the second coil.
A second dummy coil is disposed on the side opposite to the third coil as seen from the fourth coil,
A voltage that varies according to + sinωt is applied to the first coil, the second coil, and the second dummy coil,
A voltage that varies according to −sinωt is applied to the third coil, the fourth coil, and the first dummy coil,
The output of sinθsinωt is extracted from the first coil, the output of cosθsinωt from the second coil, the output of −sinθsinωt from the third coil, and the output of −cosθsinωt from the fourth coil,
When the row of at least two coils moves by one permanent magnet in the row of permanent magnets, the output of the magnetic displacement sensor is configured to change the phase θ by 2π. The dummy coil will be described. The coil at the center of the row has other coils on both sides, whereas the coil at the end of the row has other coils only on one side. For this reason, the mutual inductance between the coils is different between the center and the end of the row, and the impedances of the coils are not uniform. Here, if dummy coils are provided at both front and rear ends of the coil row, the detection coils at any position in the row have other coils on both the left and right sides, and the impedance becomes uniform between the coils.

The figure which shows the track | orbit of a moving body in an Example typically Vertical section of moving object and orbit Block diagram of the traveling drive system of a moving object Diagram showing conversion from output of magnetic displacement sensor to control center position The figure which shows the arrangement | positioning of the coil of the magnetic displacement sensor in an Example with a permanent magnet Block diagram showing a signal processing circuit in a magnetic displacement sensor The figure which shows the arrangement | positioning of the coil of the magnetic displacement sensor in a modification with a permanent magnet The figure which shows arrangement | positioning of the coil in a 2nd modification. The figure which shows the state in which the displacement sensor is partially facing the permanent magnet of an edge part in an Example. The figure which shows the magnetic displacement sensor and the magnet for a detection in a comparative example

  In the following, an optimum embodiment for carrying out the present invention will be shown. The scope of the present invention should be determined according to the understanding of those skilled in the art based on the description of the scope of the claims, taking into account the description of the specification and well-known techniques in this field.

  1 to 10 show a magnetic displacement sensor 22 of the embodiment and its deformation. The sensor 22 detects the position of the moving body 8 in the moving body system 2. In each figure, reference numeral 4 denotes a track on which the moving body 8 travels, and includes a straight section 5 and a curve section 6. The moving body 8 travels along the track 4 by, for example, three wheels 9, 10, and 10 and is guided by the guide rollers 11 and 11 guided by the track 4 in the curve section 6. The track 4 changes 90 ° in the curve section 6, but the curve section 6 is not a ¼ circle, but has a large radius of curvature near the entrance and the exit, and a small radius of curvature at the center. C1 is the center of curvature near the entrance of the curve section 6, C2 is the center of curvature near the center, and C3 is the center of curvature near the exit. In the embodiment, the track 4 is an L-shaped track provided with straight sections 5 and 5 on both sides of the curve section 6, but the layout, type, and structure of the track are arbitrary, and may be a linear track, for example. The type and structure of the moving body 8 are also arbitrary, and may be, for example, an overhead traveling vehicle that travels around along the ceiling space of a building, or a moving body that moves with a ball screw.

  The moving body 8 includes a row 12 of permanent magnets, which are movers of a linear motor. Hereinafter, the row 12 of permanent magnets may be simply referred to as permanent magnets 12. On the side of the permanent magnet 12, the moving body 8 includes a row 14 of magnets to be detected. Hereinafter, this row 14 may be simply referred to as a magnet row 14. G is a control center composed of the center of the moving body 8, and is also the center of the permanent magnet 12, and controls the linear motor based on this position G. Reference numeral 15 is a trajectory of the control center G, 16 is a trajectory of the magnet 14 to be detected, and more precisely, the trajectory of the central portion of the length of the magnet 14 to be detected.

  FIG. 2 shows the track 4 and the moving body 8, and the primary side coil 18 of the linear synchronous motor applies thrust to the permanent magnet 12 of the mover to cause the moving body 8 to travel. In addition, the kind of linear motor is arbitrary, a linear induction motor etc. may be sufficient, and it replaces with a linear motor and a normal traveling motor may be mounted in the moving body 8. FIG. Further, the primary coil 18 of the linear motor may be provided on the moving body 8, and the mover may be provided on the track 4. Reference numeral 20 denotes a coil driving unit that drives the primary coil 18. Reference numeral 22 denotes a magnetic displacement sensor, sometimes simply referred to as a displacement sensor 22, which detects the row 14 of magnets to be detected. The moving body 8 receives non-contact power supply from the track 4 side, 24 is a litz wire, and 25 is a coil for receiving power. Reference numeral 26 denotes a support of the track 4. Instead of the non-contact power supply, a contact-type power supply method may be used, or a lithium ion battery or the like may be mounted on the moving body 8.

  FIG. 3 shows the arrangement of the primary coil 18 and the displacement sensor 22 and the like. The primary coil 18 is disposed along the track 15 of the control center, and the displacement sensor 22 is disposed along the track 16 of the magnet to be detected. The outputs of the plurality of displacement sensors 22 in the curve section are input to the selector 28 in the integrated unit 27, and the selector 28 reads the position of the control center from the LUT 30 (reference table) by the output of the sensor having the maximum amplitude. The LUT 30 stores the position of the control center in the curve section as the heading of the position of the displacement sensor 22 used in the curve section 6 and the output from the displacement sensor used, and the position of the read control center Is output from the integrated unit 27 to the controller 32. In the embodiment, one LUT 30 is used, but each displacement sensor 22 is provided with an individual LUT, and the position of the control center and the amplitude of the sensor output in the curve section 6 are output from each displacement sensor 22. You may make it select. When a pair of adjacent displacement sensors 22 output the same amplitude, the positions of the control centers are obtained from the outputs of the two sensors, for example, averaged, or controlled by the output of one of the two sensors. The center position may be obtained.

  As shown in FIG. 4, the input to the integrated unit 27 is the number of the displacement sensor and the output of the displacement sensor in the curve section. As described above, the selector 28 selects the displacement sensor, and the LUT 30 positions the control center. Convert to Note that an integrated unit that integrates outputs of a plurality of displacement sensors and converts them into a control center position may be provided not only in the curve section but also in the straight section.

  In the straight line section 5, the displacement sensor 22 is arranged with a gap from the displacement sensor 22. For example, the coordinates of the control center obtained by the displacement sensor 22 are directly output to the controller 32. As a result, the coordinates of the control center of the moving body 8 are obtained in the straight section 5 and the curve section 6, and the controller 32 feedback-controls the primary side coil 18 via the coil drive unit 20 based on these coordinates, and the moving body Run 8.

  FIG. 5 shows the structure of the displacement sensor 22. In the permanent magnet row 14, N-pole magnets 34 and S-pole magnets 35 are alternately arranged, and the displacement sensor 22 includes at least two coil rows 40 and 42. The black dots in the following figures indicate the start of winding of the coils, each coil in FIG. 5 is wound clockwise, and the coils 44 and 45 in the row 40 are wound in the direction from left to right in the drawing, and the row 42 The coils 46 and 47 are wound in the direction from right to left in the figure. In the row 40 and the row 42, the coils are wound clockwise and the winding start position is reversed, which is an example in which the winding method of the coils is reversed. Even if one coil is wound clockwise and the other coil is wound counterclockwise, and the winding start position is the same, the winding method is reversed.

  The coils in the rows 40 and 42 face each other, the positions in the displacement detection direction are the same, and the beginning and end of the rows 40 and 42 of coils are at the same position. The coil rows 40 and 42 each have six coils, the coils 45 and 47 at both ends are dummy coils for impedance adjustment, and the four coils 44 and 46 at the center are detection coils, and the coils 45 and 47 are coils. The coils 44 and 46 are connected in a Japanese-style manner, and current flows in the same direction.

  Reference numeral 48 denotes an AC power supply using a DA converter. The type of power supply is arbitrary, and the output is V0sinωt. 50 is a complementary buffer, which supplies two outputs of + 1 / 2V0sinωt and -1 / 2V0sinωt to the coil arrays 40 and 42, and four detection coils 44 and 46 each detect the displacement of the magnets 34 and 35. It arrange | positions so that it may become one length along a direction. When the displacement sensor 22 moves by one permanent magnet with respect to the magnet row 14, the phase of the output of the sensor 22 changes by 2π. Assuming that the phase with respect to the permanent magnet is θ, the outputs of the coils 44 and 46 are four types of sin θ sin ωt and cos θ sin ωt and −sin θ sin ωt and −cos θ sin ωt in order from the left to the right in the figure.

  When the relative speed of the displacement sensor 22 with respect to the magnet row 14 changes, the magnetic field in the coils 44 and 46 received from the magnets 34 and 35 fluctuates, thereby generating an induced electromotive force. Here, as shown in FIG. 5, when the winding start position is reversed between the opposed coils 44 and 46 and the summing connection is made, the induced electromotive force is reversed between the opposed coils 44 and 46. As a result, the induced electromotive force is reversed. The power can be canceled.

  If the dummy coils 45 and 47 are provided at both ends, both the detection coils 44 and 46 have other coils on the left and right sides, so that the mutual inductance between the coils becomes common, and the impedance of the detection coils 44 and 46 is uniform. Can be.

  The outputs of sinθsinωt and cosθsinωt are obtained from the circuit of FIG. The subsequent signal processing is shown in FIG. 6, and since the value of ωt is known on the AC power supply 48 side, the converter 52 converts sinθsinωt to sinθcosωt. Next, sin (θ + ωt) is obtained by adding sinθcosωt and cosθsinωt by the adding unit 54. Then, for example, a time when θ + ωt = nπ (n is an integer) is obtained by the 0 crossing detector 56, and the phase θ is detected.

  FIG. 7 shows a modified displacement sensor, which is the same as the displacement sensor 22 except for the points specifically pointed out. 60 is a new coil array, 61 is a detection coil, 62 is a dummy coil, and the coils 61 and 62 are wound in the same way as the coils 44 and 45 so that current flows in the opposite direction by differential connection. is there. The coils 44 and 61 are arranged at the same position along the displacement detection direction. Similarly, the coils 45 and 62 are arranged at the same position along the displacement detection direction. Due to the differential connection, the direction of current is reversed between the coils 44 and 45 and the coils 61 and 62, so that the induced electromotive force due to the relative speed is canceled between the coils 44 and 61.

  FIG. 8 shows a second modification, showing only a pair of coils 80 and 81 facing each other in a magnetic displacement sensor. For example, six pairs of coils 80 and 81 are arranged in series, and as shown in FIG. Operates with dynamic connection. The coils 80 and 81 have the same winding start position, the coil 80 is wound clockwise, the coil 81 is wound counterclockwise, and when an electric current is applied as shown in the figure, the induced electromotive force is generated between the coil 80 and the coil 81. Reversed and canceled.

  In the magnetic displacement sensor of the embodiment, if a part of the detection coils 44, 46 faces the permanent magnets 34, 35, for example, if two or more coils face each other along the displacement detection direction, the displacement Can be detected. This situation is shown in FIG. 9, and the detection coils 44 and 46 at the right end protrude from the magnet 34r at the right end, but the displacement can be detected because they receive the magnetic field from the magnet 34r. This is because the induced electromotive force due to the relative speed is canceled between the coils 44 and 46.

  The magnetic displacement sensor of a comparative example is shown in FIG. In the comparative example, since the induced electromotive force is canceled between the coil 44a and the coil 44b, it is necessary to face the two magnets 34 and 35, and a long magnet row is required. In addition, when some of the detection coils 44b protrude from the magnet 34 as shown in FIG. 10, the induced electromotive force cannot be canceled.

In the embodiment, the following effects can be obtained.
1) The relative speed between the permanent magnets 34 and 35 and the coils 44 and 46 hardly affects the detection result of the displacement.
2) Even if the permanent magnet row 14 is short, the displacement can be detected. Further, even if a part of the detection coils 44 and 46 protrudes from the permanent magnets 34 and 35, the displacement can be detected.
3) It is difficult to make permanent magnets and coils face each other over a long range, and displacement can be easily detected even in curved sections where the vehicle often travels at a reduced speed relative to a straight section.

2 Moving body system 4 Track 5 Straight section 6 Curve section 8 Moving body 9, 10 Wheel 11 Guide roller 12 Row of permanent magnets (mover)
14 Detected magnet array 15 Control center trajectory 16 Detected magnet central trajectory 18 Primary coil 20 Coil drive unit 22 Magnetic displacement sensor 24 Litz wire 25 Coil 26 Strut 27 Integrated unit 28 Selector 30 LUT
32 Controller 34 N-pole magnet 35 S-pole magnet 40, 42 Coil array 44, 46 Detection coil 45, 47 Dummy coil 48 AC power supply 50 Complementary buffer 52 Conversion section 54 Addition section 56 0 Crossing detection section 60 Coil array 61 Coil for detection 62 Dummy coil 80, 81 Coil

G Control center
C1, C2, C3 Center of curvature

Claims (4)

A magnetic displacement sensor for detecting a displacement between a row of permanent magnets to be detected and a row of coils,
Along the detection direction of displacement, there are provided at least two rows of coils consisting of the same number of coils and having the same start and end position of the row along the detection direction of displacement, and a row of permanent magnets,
At least a pair of coils facing each other in the at least two rows of coils are connected in parallel to each other;
A power source for applying a voltage that changes according to sinωt is provided to the at least one pair of coils,
The current flowing through the at least one pair of coils is taken out as an output,
An influence on the output of the displacement sensor due to the relative speed between the row of permanent magnets and the row of coils and the magnetic field from the row of permanent magnets is canceled between the rows of the at least two rows of coils. A magnetic displacement sensor.   The at least two coils are arranged such that the facing coils are wound in the same direction and the current direction is reversed, or the facing coils are wound in the opposite direction and the current direction is the same. The magnetic displacement sensor according to claim 1. The at least two coil rows are each composed of four coils, and are arranged in the order of a first coil, a second coil, a third coil, and a fourth coil,
  The first to fourth coils are arranged in the length of one permanent magnet in the row of permanent magnets,
  In the at least two coil rows, dummy coils are provided at both front and rear ends of each row, and when viewed from the first coil, the first dummy coil is on the opposite side of the second coil.
A second dummy coil is disposed on the side opposite to the third coil as seen from the fourth coil,
  A voltage that varies according to + sinωt is applied to the first coil, the second coil, and the second dummy coil,
  A voltage that varies according to −sinωt is applied to the third coil, the fourth coil, and the first dummy coil,
  The output of sinθsinωt is extracted from the first coil, the output of cosθsinωt from the second coil, the output of −sinθsinωt from the third coil, and the output of −cosθsinωt from the fourth coil,
  The output of the magnetic displacement sensor is configured so that the phase θ changes by 2π when the at least two coil arrays move by one permanent magnet in the permanent magnet array. Item 3. A magnetic displacement sensor according to Item 1 or 2. A displacement method for detecting displacement between a row of permanent magnets to be detected and a row of coils by a magnetic displacement sensor,
In the magnetic displacement sensor, there are at least two coil rows that have the same number of coils along the displacement detection direction and that have the same start and end positions along the displacement detection direction, and the permanent magnets. A column is provided,
At least a pair of coils facing each other in the at least two rows of coils are connected in parallel to each other;
A voltage that varies according to sinωt from a power source is applied to the at least one pair of coils,
Taking out the current flowing through the at least one pair of coils as an output,
The influence on the output of the displacement sensor due to the relative speed between the row of permanent magnets and the row of coils and the magnetic field from the row of permanent magnets is canceled between the rows of the at least two coils, Displacement detection method.

Images