Variable Reluctance Position Sensor

Abstract

The variable reluctance position sensor comprises a first element (101) having a magnetic sensor portion (102) and a second element (103) movable relative to the first element, the magnetic sensor portion having an excitation coil, a first detection coil and a second detection coil. The air gap surface of the second element is periodically tortuous. When an alternating signal is supplied to the excitation coil, the envelope of the alternating signal induced in the first and second detection coils depends on the position of the second element, so that the envelope has a phase offset relative to each other. The number of magnetic sensor portions is 1+nP2 / P1, where P1 is the spatial offset between successive magnetic sensor portions, P2 is the spatial tortuosity period of the air gap surface, and n is an integer. The magnetic sensor portions other than the nP2 / P1 magnetic sensor portions are suitable for compensating for undesirable effects caused by the ends of the first element.

Description

Technical Field

[0001] The present disclosure relates to a variable reluctance position sensor, which may or may not be a variable reluctance rotary transformer, for generating a signal indicating the rotation angle of a rotating object such as a rotor of a motor. For another example, the variable reluctance position sensor may be a sensor configured to measure the position of a moving object such as a mover of a linear motor. Background Art

[0002] The variable reluctance "VR" position sensor comprises an excitation coil and a detection coil in a first element, but no coil in a second element, which is movable relative to the first element and whose position relative to the first element is to be measured. Therefore, there is no need to conduct current to the moving second element. The variable reluctance position sensor may be, for example, a variable reluctance rotary transformer, in which the first element is a stator and the second element is a rotor, the rotation angle of the rotor relative to the stator to be measured. A significant advantage of the variable reluctance rotary transformer is that there is no need to conduct current to the rotor. The stator of the variable reluctance rotary transformer receives an alternating excitation signal for exciting the winding, and generates a first alternating output signal and a second alternating output signal by a first detection winding and a second detection winding, respectively, wherein the amplitudes of the first alternating output signal and the second alternating output signal depend on the rotational position of the rotary transformer, so that the envelope of the first alternating output signal and the envelope of the second alternating output signal (i.e., the curves outlining the extreme values ​​of the first alternating output signal and the second alternating output signal) have a mutual phase offset.

[0003] Publication US20130162243 describes a variable reluctance rotary transformer, which includes an annular stator, a rotor and a housing. The stator includes a stator core and a coil. The stator core is provided with a plurality of salient poles. The coil is wound to the salient poles of the stator. The housing accommodates the stator. The rotor includes an air gap surface having a profile formed with a plurality of arc-shaped protrusions, which deviate from a circle and are positioned at equal intervals in the circumferential direction. The number of arc-shaped protrusions is the ratio of 360 degrees (i.e., a complete circle) to the central angle of the measurement sector of the variable reluctance rotary transformer. In the case where the variable reluctance rotary transformer is used to measure the rotation angle of the rotor of the motor, the number of the above-mentioned arc-shaped protrusions can be, for example, the same as the number of pole pairs of the motor, and thereby the variable reluctance rotary transformer measures the rotation position of the rotor of the motor as electrical degrees. It is also feasible that the number of pole pairs of the motor is a multiple of the number of arc-shaped protrusions. In this exemplary case, the angle measured with the variable reluctance resolver will be multiplied by this factor to obtain the rotational position of the rotor of the motor as electrical degrees of the motor.

[0004] However, the above-described type of variable reluctance resolver is not without challenges. One of the challenges involves the use of a variable reluctance resolver to measure the rotation angle of the rotor of a motor having a very large number of pole pairs. In the exemplary case where the number of arc-shaped protrusions of the rotor of the variable reluctance resolver is the same as the number of pole pairs of the motor, the center angle of the measurement sector of the variable reluctance resolver is small in mechanical degrees, and therefore the pole pitch in the stator of the variable reluctance resolver must be small in mechanical degrees to achieve sufficient electrical degree measurement accuracy. This may result in a situation where the periphery of the stator of the variable reluctance resolver has a very large number of stator teeth, making the variable reluctance resolver complex and expensive. In another exemplary case where the number of pole pairs of the motor is a multiple of the number of arc-shaped protrusions, when the measured resolver angle is multiplied by the multiple to obtain the rotational position of the rotor of the motor as the electrical degree of the motor, the sensed position error increases. Summary of the invention

[0005] A simplified overview is given below to provide a basic understanding of some aspects of various invention embodiments. This overview is not an extensive overview of the present invention. It is neither intended to identify the key or decisive elements of the present invention nor to delineate the scope of the present invention. The following overview merely presents some concepts of the present invention in a simplified form as a prelude to a more detailed description of the exemplary embodiments.

[0006] In this document, the word "geometry" when used as a prefix refers to a geometric concept, not necessarily a part of any physical object. A geometric concept can be, for example, a geometric point, a straight or curved geometric line, a planar or non-planar geometric surface, a geometric space, or any other geometric entity of zero, one, two, or three dimensions.

[0007] According to the present invention, a new variable reluctance position sensor is provided, which may be a variable reluctance resolver for measuring the rotation angle of a rotating object. However, it is also possible that the variable reluctance position sensor according to an embodiment of the present invention is configured to measure the position of a linear moving object.

[0008] The variable reluctance position sensor according to the present invention comprises:

[0009] - a first element comprising a plurality of magnetic sensor portions equidistantly successive from one another; and

[0010] a second element, which is movable relative to the first element and comprises an air gap surface having a periodic meandering profile having at least two spatial meandering periods,

[0011] in:

[0012] - each of the magnetic sensor portions is configured to conduct magnetic flux to and from the second element via the air gap surface of the second element, and

[0013] -The magnetic sensor part includes an excitation coil, a first detection coil and a second detection coil, the first detection coil being configured to generate a first alternating output signal when an alternating excitation signal is supplied to the excitation coil, the second detection coil being configured to generate a second alternating output signal when the alternating excitation signal is supplied to the excitation coil, the amplitudes of the first alternating output signal and the second alternating output signal depending on the position of the second element relative to the first element, so that the envelope of the first alternating output signal and the envelope of the second alternating output signal (i.e., the curve outlining the extreme values ​​of the first alternating output signal and the second alternating output signal) have a phase offset relative to each other.

[0014] The number N of the magnetic sensor parts of the above-mentioned first element is:

[0015] N=1+nP2 / P1,

[0016] wherein P1 is the spatial offset between consecutive said magnetic sensor portions, P2 is said spatial meandering period of said profile of said air gap surface of said second element, P2 / P1 is an integer greater than 1, and n is a positive integer, advantageously one, i.e. n = 1. In principle, it is sufficient for the first element to cover exactly one spatial meandering period of the profile of the air gap surface (i.e. there are P2 / P1 magnetic sensor portions), since the functionality will be the same at other spatial meandering periods of the profile of the air gap surface, but magnetic sensor portions other than P2 / P1 magnetic sensor portions may be used to compensate for undesirable effects caused by the ends of the first element comprising said plurality of magnetic sensors.

[0017] In the exemplary case where the variable reluctance position sensor is a variable reluctance rotary transformer for measuring the rotation angle of a motor having many pole pairs, the stator of the variable reluctance rotary transformer does not cover 360 mechanical degrees, but only covers n×360 electrical degrees of the motor (e.g., 1×360 electrical degrees or 720 electrical degrees or other multiples of 360 electrical degrees) plus the above-mentioned P1, which is the spatial offset between consecutive magnetic sensor parts and is n×360 electrical degrees / (N-1), N being the number of magnetic sensor parts in the stator of the variable reluctance rotary transformer. The spatial offset P1 can be expressed in electrical degrees because the geometry is circular.

[0018] Various exemplifying and non-limiting embodiments are described in the accompanying dependent claims.

[0019] Exemplary and non-limiting embodiments, both as to construction and methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplary and non-limiting embodiments when read in connection with the accompanying drawings.

[0020] The verbs "comprise" and "include" are used in this document as open limitations, neither excluding nor requiring the presence of unrecited features. The features recited in the dependent claims may be freely combined with each other unless explicitly stated otherwise. Furthermore, it should be understood that the use of "a" or "an" in this document, i.e. the singular, does not exclude a plurality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Exemplary and non-limiting embodiments and their advantages are explained in more detail below by way of example and with reference to the accompanying drawings, in which:

[0022] Figure 1 A variable reluctance position sensor according to an exemplary and non-limiting embodiment is shown,

[0023] Figure 2a and Figure 2b A variable reluctance position sensor according to an exemplary and non-limiting embodiment is shown, and

[0024] Figure 3a and Figure 3b A variable reluctance position sensor is shown according to one exemplary and non-limiting embodiment. DETAILED DESCRIPTION

[0025] The specific examples provided in the following description should not be construed as limiting the scope and / or applicability of the appended claims.The lists and groups of examples provided in the description are not exhaustive unless expressly stated otherwise.

[0026] Figure 1 A variable reluctance position sensor according to an exemplary and non-limiting embodiment is shown. The variable reluctance position sensor comprises a first element 101 and a second element 103. In this exemplary case, the variable reluctance position sensor is a variable reluctance rotary transformer for measuring a rotation angle θ of the second element 103 relative to the first element 101. The first element 101, i.e., the stator, comprises a plurality of magnetic sensor portions equidistantly successive along an arc of a geometric circle. Figure 1 In the embodiment, one of the magnetic sensor parts is indicated by reference numeral 102. The second element 103, i.e. the rotor, comprises an air gap surface 104 having a periodic meandering profile having at least two spatial meandering periods. Figure 1 As shown in FIG. 1 , the profile of the air gap surface 104 is curved relative to the geometric circle 110, so that the radius r is the central angle The central angle is defined relative to a reference direction fixed to the second element 103. The radius r can be, for example where γ is a constant. The component 109 of the second element 103 may comprise electrically insulating ferromagnetic sheets stacked in the axial direction of the second element 103 (ie in the z direction of the coordinate system 199). It is also possible that the component 109 is made of, for example, ferrite or a soft magnetic composite material such as, for example The central part 108 of the second element 103 may be made of, for example, solid steel.

[0027] Each magnetic sensor portion of the first element 101 is configured to conduct magnetic flux to and from the second element 103 via the air gap surface 104 of the second element. The magnetic sensor portions include an excitation coil. Figure 1 In FIG. 1 , an excitation coil is denoted by reference numeral 105. The magnetic sensor parts include first detection coils configured to generate first alternating output signals when alternating excitation signals are supplied to the excitation coils. Figure 1 In FIG. 1 , a first detection coil is indicated by reference numeral 106. The magnetic sensor parts include second detection coils configured to generate second alternating output signals when alternating excitation signals are supplied to the excitation coils. Figure 1 , a first detection coil is denoted by reference numeral 107. The amplitudes of the first alternating output signal and the second alternating output signal depend on the rotation angle θ of the second element 103 relative to the first element 101, so that the envelope of the first alternating output signal and the envelope of the second alternating output signal (i.e., the curves outlining the extreme values ​​of the first alternating output signal and the second alternating output signal) have a phase offset relative to each other.

[0028] The number N of magnetic sensor portions of the first element 101 is:

[0029] N=1+nP2 / P1,

[0030] Where P1 is the spatial offset between successive magnetic sensor portions, P2 is the spatial meandering period of the profile of the air gap surface 104, P2 / P1 is an integer greater than 1, and n is a positive integer (advantageously 1). Figure 1 In the example variable reluctance rotary transformer shown in , the spatial offset P1 between successive magnetic sensor portions is 15 mechanical degrees, and the spatial meandering period of the profile of the air gap surface 104 is 180 mechanical degrees. The above spatial offset P1 and spatial meandering period can be expressed in mechanical degrees because of the circular geometry. Therefore, as Figure 1, the number of magnetic sensor portions 13 is N. In principle, it is sufficient for the first element 101 to cover exactly one spatial meandering period of the profile of the air gap surface 104 (i.e., there are 12 magnetic sensor portions), because the function will be the same at other spatial meandering periods of the profile of the air gap surface 104, but in addition to the 12 magnetic sensor portions, the 13th magnetic sensor portion can be used to compensate for the undesirable influence caused by the end of the first element 101.

[0031] In a variable reluctance position sensor according to an exemplary and non-limiting embodiment, the number of magnetic sensor portions of the first element is N=2M+1, where M is a positive integer, and thus N is an odd number. The first detection coil is in the 2nd, 4th, ..., and 2Mth magnetic sensor portions, the second detection coil is in the 1st, 3rd, ..., and 2M+1th magnetic sensor portions, and:

[0032] N s (2i) = N s0 sin[2π(2i–1) / (2M)], i=1,…,M, and

[0033] N c (2j+1)=N c0 cos[2π(2j) / (2M)]+N a (2j+1), j=0,…,M,

[0034] Where N s0 and N c0 is a predetermined integer, N s The absolute value of (2i) is the number of turns of the first detection coil in the 2i-th magnetic sensor section, N c The absolute value of (2j+1) is the number of turns of the second detection coil in the 2j+1th magnetic sensor section, N s The sign of Nc(2j+1) indicates the winding direction of the first detection coil in the 2i-th magnetic sensor section, and the sign of Nc(2j+1) indicates the winding direction of the second detection coil in the 2j+1-th magnetic sensor section. When j=0 or M, Na(2j+1) is a predetermined integer, otherwise N a (2j+1) is zero. The integer N a (1) and N a (2M+1) represents the adjustment of the number of turns of the second detection coils in the 1st and 2M+1th magnetic sensor sections to compensate for the undesirable influence caused by the end of the first element 101. Appropriate number of turns adjustment N a (1) and N a (2M+1) can be found, for example, by simulation and / or empirical experiment. In some cases, N a (1) and / or N a (2M+1) is zero.

[0035] For example, the excitation coil could look like this:

[0036] N e (k) = (-1) (k+1) N e0 , k=1,…,2M+1,

[0037] Where N e0 is a predetermined integer, N e The absolute value of (k) is the number of turns of the excitation coil in the kth magnetic sensor section, and N e The sign of (k) indicates the winding direction of the exciting coil in the k-th magnetic sensor section.

[0038] In the variable reluctance position sensor according to the above-mentioned exemplary and non-limiting embodiment, the envelope of the first alternating output signal generated by the first detection coil is proportional to the sine of the rotation angle θ, i.e. sin(θ), and the envelope of the second alternating output signal generated by the second detection coil is proportional to the cosine of the rotation angle θ, i.e. cos(θ).

[0039] exist Figure 1 In the exemplary variable reluctance rotary transformer shown in , the first detection coil is in the 2nd, 4th, ..., and 12th magnetic sensor parts, the second detection coil is in the 1st, 3rd, ..., and 13th magnetic sensor parts, and:

[0040] N s (2i) = N s0 sin[π(2i–1) / 6], i=1,…,6, and

[0041] N c (2j+1)=N c0 cos[π(2j) / 6]+N a (2j+1), j=0,…,6.

[0042] According to the simulation results, if only 12 magnetic sensor sections covering exactly one spatial meandering period of the profile of the air gap surface 104 are used, the second detection coil (i.e., the cosine signal winding) will not show a balanced signal output. More specifically, the signal amplitude varies at different time periods. The 13th magnetic sensor section is used to compensate for this undesirable phenomenon.

[0043] exist Figure 1 In the exemplary variable reluctance rotary transformer shown in , the air gap surface 104 of the second element 103 (ie, the rotor) faces the first element 101 (ie, the stator) in the radial direction. Figure 2a and Figure 2b A variable reluctance resolver according to another exemplary and non-limiting embodiment is shown. Figure 2a shows the variable reluctance resolver as viewed along the negative z-direction of coordinate system 299, and Figure 2b Shown along Figure 2a The variable reluctance rotary transformer includes a first element 201 as a stator of the variable reluctance rotary transformer and a second element 203 as a rotor of the variable reluctance rotary transformer. The stator includes a plurality of magnetic sensor parts that are equidistantly connected to each other along an arc of a geometric circle. Figure 2a and Figure 2b In the embodiment, one of the magnetic sensor parts is indicated by reference numeral 202. The rotor comprises an air gap surface 204 having a periodic meandering profile having at least two spatial meandering periods. In this exemplary case, the air gap surface 204 of the rotor faces the stator in the axial direction, and the rotor and the stator are axially consecutive. Figure 2b As shown in , the profile of the air gap surface 204 is meandering relative to a geometric plane 210, which is perpendicular to the z-axis of the coordinate system 299. The part 209 of the rotor may include a roll of electrically insulating ferromagnetic sheets, so that the geometric axis of the roll coincides with the geometric axis of rotation of the rotor. It is also possible that the part 209 is made of, for example, ferrite or a soft magnetic composite material such as, for example The central part 208 of the rotor may be made of, for example, solid steel.

[0044] Figure 3a and Figure 3b A variable reluctance position sensor according to an exemplary and non-limiting embodiment is shown. The variable reluctance position sensor comprises a first element 301 and a second element 303. In this exemplary case, the variable reluctance position sensor is a linear position sensor configured to measure the position of the second element 303 relative to the first element 301 in the x-direction of a coordinate system 399. Figure 3a shows a linear position sensor when looking along the negative z direction of coordinate system 399, and Figure 3b 399. The linear position sensor is shown as viewed in the positive y-direction of the coordinate system 399. The first element 301 comprises a plurality of magnetic sensor portions equidistantly successive along a geometric line. Figure 3a and Figure 3b In the embodiment, one of the magnetic sensor parts is indicated by reference numeral 302. The second element 303 includes an air gap surface 304 having a periodic meandering profile having at least two spatial meandering periods. Figure 3b As shown in , the profile of the air gap surface 304 is tortuous relative to a geometric plane 310 , which is perpendicular to the z-axis of the coordinate system 399 .

[0045] exist Figure 1 , Figure 2a , Figure 2b , Figure 3a and Figure 3b In the exemplary variable reluctance position sensor shown in , each magnetic sensor part has a core element that is separate from the core elements of the other magnetic sensor parts. Each core element includes a material with a relative magnetic permeability μ greater than 1. The material is advantageously a ferromagnetic material. Each core element may include, for example, a stack of electrically insulating steel sheets, ferrites or soft magnetic composite materials. However, it is also feasible that the magnetic sensor parts have a common core having teeth and a yoke connected to the teeth.

[0046] The specific examples provided in the description given above should not be construed as limiting the scope and / or applicability of the appended claims.The lists and groups of examples provided in the description given above are not exhaustive unless expressly stated otherwise.

Claims

1. A variable reluctance position sensor, comprising: - a first element (101, 201, 301) comprising a plurality of magnetic sensor portions (102, 202) equidistant from one another; and a second element (103, 203, 303), the second element (103, 203, 303) being movable relative to the first element, and the second element (103, 203, 303) comprising an air gap surface (104, 204, 304), the air gap surface (104, 204, 304) having a periodic meandering profile, the periodic meandering profile having at least two spatial meandering periods, in: - each of the magnetic sensor portions is configured to conduct magnetic flux to and from the second element via the air gap surface of the second element, and - the magnetic sensor part comprises an excitation coil (105), a first detection coil (106) and a second detection coil (107), the first detection coil (106) being configured to generate a first alternating output signal when an alternating excitation signal is supplied to the excitation coil, the second detection coil (107) being configured to generate a second alternating output signal when the alternating excitation signal is supplied to the excitation coil, the amplitudes of the first alternating output signal and the second alternating output signal being dependent on the position of the second element relative to the first element, so that the envelope of the first alternating output signal and the envelope of the second alternating output signal have a phase offset relative to each other, Characterized in that the number N of the magnetic sensor portions of the first element is: N=1+nP2 / P1, wherein P1 is the spatial offset between consecutive magnetic sensor portions, P2 is the spatial meandering period of the profile of the air gap surface of the second element, P2 / P1 is an integer greater than 1, and n is a positive integer.

2. The variable reluctance position sensor according to claim 1, wherein the variable reluctance position sensor is a variable reluctance rotary transformer, in which the first element (101, 102) is a stator, and the second element (103, 203) is a rotor capable of rotating relative to the stator, the magnetic sensor parts (102, 202) are equidistantly successive along an arc of a geometric circle, and the position of the second element relative to the first element is the rotation angle (θ) of the rotor relative to the stator.

3. The variable reluctance position sensor according to claim 2, wherein the air gap surface (104) of the rotor faces the stator in a radial direction, and the radius (r) of the rotor is a central angle relative to a reference direction fixed to the rotor. A periodic function of . 4 . The variable reluctance position sensor according to claim 3 , wherein the rotor includes electrically insulating ferromagnetic sheets stacked in an axial direction of the rotor.

5. The variable reluctance position sensor according to claim 2, wherein the air gap surface (204) of the rotor faces the stator in the axial direction, and the rotor and the stator are axially consecutive.

6. A variable reluctance position sensor as claimed in claim 5, wherein the rotor comprises a roll of electrically insulating ferromagnetic sheets, the geometric axis of the roll coinciding with the geometric axis of rotation of the rotor.

7. A variable reluctance position sensor according to claim 1, wherein the variable reluctance position sensor is a linear position sensor, which is configured to measure the position of the second element (303) relative to the first element (301) in the direction of linear movement of the first element relative to the second element. 8 . The variable reluctance position sensor of claim 1 , wherein the number N of the magnetic sensor portions of the first element is an odd number.

9. The variable reluctance position sensor according to claim 8, wherein the number of the magnetic sensor parts of the first element is N=2M+1, where M is a positive integer, the first detection coil is in the 2nd, 4th, ... and 2Mth magnetic sensor parts, the second detection coil is in the 1st, 3rd, ... and 2M+1th magnetic sensor parts, and: N s (2i) = N s0 sin[2π(2i – 1) / (2M)], i = 1, …, M, and <h2 style=";text-align:left;direction:ltr">N<h2 style=";text-align:left;direction:ltr"> c <h2 style=";text-align:left;direction:ltr"> (2j+1)=N<h2 style=";text-align:left;direction:ltr"> c0 <h2 style=";text-align:left;direction:ltr"> cos[2π(2j) / (2M)]+N<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> (2j+1),j=0,…,M, Where N s0 and N c0 is a predetermined integer, N s The absolute value of (2i) is the number of turns of the first detection coil in the 2i-th magnetic sensor section, N c The absolute value of (2j+1) is the number of turns of the second detection coil in the 2j+1th magnetic sensor section, N s The symbol (2i) represents the winding direction of the first detection coil in the 2i-th magnetic sensor section, N c The sign of (2j+1) indicates the winding direction of the second detection coil in the 2j+1th magnetic sensor section, and when j=0 or M, N a (2j+1) is a predetermined integer, otherwise N a (2j+1) is zero.

10. The variable reluctance position sensor according to claim 9, wherein: N e (k)=(-1) (k+1) N e0 ,k=1,…,2M+1, Where N e0 is a predetermined integer, N e The absolute value of (k) is the number of turns of the excitation coil in the kth magnetic sensor section, and N e The symbol (k) represents the winding direction of the exciting coil in the k-th magnetic sensor section.

11. The variable reluctance position sensor of claim 1, wherein each of said magnetic sensor portions (102, 202) has a magnetic core element separate from magnetic core elements of other said magnetic sensor portions.

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