Position measuring device, angle measuring device, and angle measuring method

Abstract

The present invention provides a position detection device, an angle measuring device, and an angle measuring method that offer good detection accuracy for position detection including rotation angle, while also allowing for a simplified configuration. [Solution] The position measuring device 1 includes a physical field forming means 4 attached to one of the fixed part and the movable part, which forms a physical field PF1 represented by a predetermined physical quantity; a plurality of fluctuation detection elements 5 attached to the other of the fixed part and the movable part, which output analog signals corresponding to fluctuations in physical quantities within the physical field PF1 when the movable part moves relative to the physical field PF1; and a position conversion unit 6 that converts the state of each analog signal output from the plurality of fluctuation detection elements 5 into a signal indicating the relative position of the movable part.

Description

[Technical Field]

[0001] The present invention relates to a position measuring device, an angle measuring device, and an angle measuring method. [Background technology]

[0002] One method for evaluating the running safety of railway vehicles involves measuring the force acting between the wheel and the rail using a wheelset (PQ wheelset) that has numerous strain gauges attached to it to create load cells. As one measurement method, for example, Non-Patent Literature 1 proposes a method in which the change in strain sensitivity to force in the circumferential direction of the wheel is corrected using a wheel rotation angle sensor and converted into information about continuous contact force. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Hiroaki Ishida, Masaki Matsuo, Kazuhiko Tezuka, and Kenji Ueki, "A New Continuous Measurement Method for Wheel Load, Lateral Pressure, and Derailment Coefficient of Railway Vehicles (Development of a Measurement Device)," Transactions of the Japan Society of Mechanical Engineers, Series C, Vol. 63, No. 614 (1997), pp. 3417-3423. [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, the rotary encoders currently used to measure the wheel rotation angle in continuous force measurement using PQ wheelsets are commercially available products attached to slip ring devices. On the other hand, the current slip ring devices have, for example, 20 poles (5 systems), and in order to increase the number of signals to be measured, a new slip ring device design is required.

[0005] When designing a new slip ring system, the currently used rotary encoder is selected to fit a 20-pole slip ring. However, if the number of poles in the slip ring increases, a new rotary encoder that fits the increased number of poles must be selected. If commercially available rotary encoders are incompatible, the design of the slip ring system must be significantly revised, which poses a major constraint to the design. This problem can be solved by designing a rotary encoder to match the slip ring, but manufacturing a rotary encoder requires precisely machining a device that generates minute pulse signals, and if it is not a mass-produced item, the manufacturing cost will increase. In addition, using a rotary encoder requires a pulse counter in addition to the AD converter normally used for data acquisition, making it difficult to simplify and standardize the measurement equipment.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a position detection device, an angle measuring device, and an angle measuring method that have good detection accuracy for position detection including rotation angle, while also being able to simplify the configuration. [Means for solving the problem]

[0007] [1] In order to solve the above problems, according to a first aspect of the present invention, a position measuring device is provided for measuring the relative position of a moving part with respect to a fixed part, comprising: a physical field forming means attached to one of the fixed part and the moving part and forming a physical field represented by a predetermined physical quantity; a plurality of fluctuation detection elements attached to the other of the fixed part and the moving part and outputting as an analog signal corresponding to the fluctuation of a physical quantity in the physical field when the moving part moves relative to the physical field; and an angle conversion unit that converts the state of each analog signal output from the plurality of fluctuation detection elements into a signal indicating the relative position of the moving part.

[0008] [2] In addition, to solve the above problems, according to a second aspect of the present invention, an angle measuring device for measuring the rotation angle of a rotating shaft with respect to a fixed part is provided, comprising: a physical field forming means attached to one of the fixed part and the rotating shaft and forming a physical field represented by a predetermined physical quantity; a plurality of fluctuation detection elements attached to the other of the fixed part and the rotating shaft and outputting an analog signal corresponding to the fluctuation of a physical quantity in the physical field when it moves relatively within the physical field; and an angle conversion unit that converts the state of each analog signal output from the plurality of fluctuation detection elements into a signal indicating the rotation angle of the rotating shaft.

[0009] [3] In addition, in order to solve the above problems, according to a second aspect of the present invention, there is an angle measurement method for measuring the rotation angle of a rotation axis with respect to a fixed part, comprising: a physical field forming means attached to one of the fixed part and the rotation axis and forming a physical field represented by a predetermined physical quantity; and a plurality of fluctuation detection elements attached to the other of the fixed part and the rotation axis and outputting as analog signals corresponding to fluctuations in physical quantities in the physical field when they rotate relatively within the physical field, and an angle conversion processing step of converting the state of each analog signal output from the plurality of fluctuation detection elements into the rotation angle of the rotation axis. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a position detection device, an angle measuring device, and an angle measuring method that offer good detection accuracy for position detection including rotation angle, while also being able to simplify the configuration. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a concept of a position measuring device according to one embodiment of the present invention. [Figure 2] This figure shows a schematic configuration of an angle measuring device corresponding to an example of a position measuring device shown in Figure 1. [Figure 3]It is a diagram showing a schematic configuration in which an angle measuring device shown in Fig. 2 is arranged in a slip ring device of a transverse pressure measuring device. [Figure 4] It is a diagram showing an attachment member for attaching the angle measuring device shown in Fig. 2 to a slip ring device. [Figure 5] It is a perspective view showing a magnet fixing member constituting the attachment member shown in Fig. 4. [Figure 6] It is a perspective view showing an element fixing member constituting the attachment member shown in Fig. 4. [Figure 7] It is a diagram showing the result of calculating the Hall element output characteristics when the Hall element unit rotates under the arrangement conditions in Table 1 using a predetermined magnetic dipole model. [Figure 8] It is a diagram showing the result of approximating the result shown in Fig. 7 with a Fourier series of the maximum order n = 15. [Figure 9] It is a diagram showing the result of constructing a vector s from the output of the Hall element as shown in Fig. 7 and calculating the first-order term of the approximate value ^ξ of the basis function vector. [Figure 10] It is a diagram showing the result of further calculating the approximate solution initial value and error using the arctangent from the result shown in Fig. 9. [Figure 11] It is a diagram showing the result of calculating an approximate solution by recurrence calculation with a stabilization coefficient λ = 2×10-4 and a recurrence number of 40 times from the result shown in Fig. 10. [Figure 12] It is a diagram showing the result of calculating the Hall element output characteristics when the Hall element unit rotates under the arrangement conditions in Table 2 using a predetermined magnetic dipole model. [Figure 13] It is a diagram showing the result of approximating the result shown in Fig. 12 with a Fourier series of the maximum order n = 20. [Figure 14] It is a diagram showing the result of constructing a vector s from the output of the Hall element as shown in Fig. 12 and calculating the first-order term of the approximate value ^ξ of the basis function vector. [Figure 15] It is a diagram showing the result of further calculating the approximate solution initial value using the arctangent from the result shown in Fig. 14. [Figure 16]This is a diagram showing the result of calculating an approximate solution by recurrence calculation with the stabilization coefficient of the iterative calculation being λ = 5×10-5 and the number of iterations being 60 times, based on the result shown in FIG. 15. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, a position measurement device 1, an angle measurement device 10, and an angle measurement method according to an embodiment of the present invention will be described based on the drawings.

[0013] [1. Regarding the concept of the position measurement device 1] FIG. 1 is a diagram showing the concept of the position measurement device 1. As shown in FIG. 1, the position measurement device 1 has a physical field forming means 4 attached to one of the mounting members 2 of the fixed part and the moving part. This physical field forming means 4 forms a physical field PF1, and various physical fields such as a magnetic field, an electric field, and an optical field correspond to the physical field PF1.

[0014] Also, the position measurement device 1 has a variation detection element 5 attached to the other mounting member 3 of the fixed part and the moving part. This variation detection element 5 is an element that outputs an analog signal corresponding to the variation of the physical quantity in the physical field PF1 when it moves relatively within the physical field PF1 formed by the above physical field forming means 4.

[0015] Also, the position measurement device 1 has a position conversion unit 6. The position conversion unit 6 is a part that converts the analog signal into position information while maintaining the state of the analog signal.

[0016] In the position measurement device 1 with the above concept, the common use of the measurement device can be achieved, and the degree of freedom in design can be increased. Hereinafter, the position measurement device 1 with a more specific concept will be described.

[0017] [2. Regarding the configuration of the angle measurement device 10 as the position measurement device 1] Figure 2 shows a schematic configuration of an angle measuring device 10 corresponding to an example of a position measuring device 1 according to this embodiment. The angle measuring device 10 is attached to the slip ring device 160 of the PQ wheelset 110 shown in Figure 3. However, the angle measuring device 10 is not limited to being attached to the slip ring device 160 of the PQ wheelset 110, and may be attached to other devices.

[0018] The angle measuring device 10 includes a fixed part 20, a rotating shaft 30, a magnet 40, a Hall element 50, and an angle conversion unit 60.

[0019] The fixed portion 20 is a part that does not rotate relative to the other part, and is the part to which the magnets 40 are attached. This fixed portion 20 can take any form as long as multiple magnets 40 are attached to it. In Figure 2, the fixed portion 20 is shown as a cylindrical inner surface 21, but this cylindrical inner surface 21 can be of any form.

[0020] Furthermore, the rotating shaft 30 corresponds to the moving part. This rotating shaft 30 is located in the radially central part of the fixed part 20, and this location is the central part of the area where multiple (two in Figure 2) magnets 40 face each other to form a physical field, which is a magnetic field GF1. When the rotating shaft 30 is attached to the slip ring device 160 as shown in Figure 2, the rotating shaft 30 is provided to rotate coaxially with the axle 140 in Figure 2 and in synchronous motion. However, the rotating shaft 30 may also be configured to rotate via, for example, a reduction mechanism.

[0021] In this embodiment, a permanent magnet is used for the magnet 40 attached to the fixed part 20 described above, but an electromagnet may also be used. The magnet 40 is the part that forms the magnetic field GF1, which is a physical field, and corresponds to the means for forming the physical field.

[0022] Multiple magnets 40 are arranged at predetermined intervals in the circumferential direction of the rotation axis 30. In the configuration shown in Figure 2, two magnets 40 are arranged circumferentially at 180-degree intervals. However, the number of magnets 40 can be any number, as long as the proximity of the magnets 40 does not significantly affect the detection signal of one Hall element 50.

[0023] Furthermore, in the configuration shown in Figure 2, the two magnets 40 are arranged at equal pitches, such as 180-degree intervals. However, a configuration in which multiple magnets 40 are arranged at unequal pitches may also be adopted.

[0024] The Hall element 50 is mounted on the outer circumference of the rotating shaft 30. This Hall element 50 is a sensor whose output value, such as voltage, changes in response to a change in position in the magnetic field GF1, which is a physical field, and corresponds to a fluctuation detection element. The Hall elements 50 are arranged at predetermined pitches in the circumferential direction of the rotating shaft 30. In Figure 2, four Hall elements 50 are arranged, but any number of elements is acceptable as long as the rotation angle of the rotating shaft 30 can be detected well.

[0025] The angle conversion unit 60 is a part that performs an angle conversion process (angle conversion process) that decodes the output of an analog signal, such as voltage, which changes smoothly in response to a change in rotation angle, based on a method described later, and converts it into a rotation angle.

[0026] [3. Regarding the mounting configuration of the angle measuring device 10] The angle measuring device 10 described above can be placed in the slip ring device 160 that constitutes the lateral pressure measuring device 100. The following describes a configuration in which the angle measuring device 10 is placed in the slip ring device 160 of the lateral pressure measuring device 100.

[0027] Figure 3 shows a schematic configuration in which the angle measuring device 10 is placed on the slip ring device 160 of the lateral pressure measuring device 100. As shown in Figure 3, the lateral pressure measuring device 100 comprises a PQ wheelset 110, a slip ring device 160, a strain signal processing unit 170, and a calculation unit 180.

[0028] The PQ wheelset 110 is a wheelset used to measure the wheel load, lateral pressure, and longitudinal tangential force acting between the wheel 130 and the rail using strain gauges 150 attached to the wheel 130, and the wheelset itself can be considered a load cell. This PQ wheelset 110 comprises a wheelset 120 and strain gauges 150.

[0029] Wheel load refers to the radial force on the wheel 130 from the rail, lateral force refers to the axial force on the axle 140 that the wheel 130 receives from the rail, and longitudinal tangential force refers to the force on the wheel 130 from the rail in the direction of the rail's extension.

[0030] As shown in Figure 3, the wheelset 120 is constructed by press-fitting the vicinity of both ends of the axle 140 into the pair of left and right wheels 130 and then fixing them in place.

[0031] Furthermore, the strain gauge 150 is a sensor that measures strain in a predetermined direction, and in this embodiment, a triaxial strain gauge and a single-axis strain gauge can be used. The triaxial strain gauge of the strain gauge 150 is placed inside a measuring hole drilled in the plate surface of the wheel 130 and / or on the plate portion of the wheel 130. The single-axis strain gauge is placed on the plate portion of the wheel 130. However, the arrangement of the strain gauge 150 is not limited to this.

[0032] The strain gauge 150 described above is placed in a predetermined bridge circuit, which is not shown in the figure. The output of this bridge circuit is input to the slip ring device 160 shown in Figure 3. The slip ring device 160 then outputs a signal to the strain signal processing unit 170.

[0033] The distortion signal processing unit 170 receives the output of the bridge circuit described above. The distortion signal processing unit 170 amplifies the input signal and performs signal processing such as AD conversion, and then transmits a predetermined signal to the calculation unit 180.

[0034] The calculation unit 180 calculates wheel load, lateral pressure, longitudinal tangential force, etc., by performing predetermined calculations.

[0035] [4. Specific mounting configuration of the angle measuring device 10]

[0036] Next, we will describe the mounting member 200, which is a specific mounting configuration for the angle measuring device 10 as shown in Figure 2. Figure 4 shows the mounting member 200 for attaching the angle measuring device 10 to the slip ring device 160. As shown in Figure 4, the mounting member 200 has a magnet fixing member 210 and an element fixing member 220.

[0037] Figure 5 is a perspective view showing the magnet fixing member 210 that constitutes the mounting member 200. As shown in Figures 4 and 5, the flange portion 30a of the rotating shaft 30, which is the rotation axis of the slip ring device 160, is fixed to the radial center of the magnet fixing member 210. The magnet fixing member 210 is also provided with a magnet fixing portion 212. The magnet fixing portion 212 is the part for fixing the magnet 40 described above and protrudes a predetermined amount from the surface 211 of the magnet fixing member 210. An insertion hole 213 is provided in this magnet fixing portion 212, into which the magnet 40 is inserted and fixed inside the insertion hole 213 by screws or other means.

[0038] In this embodiment, a pair of insertion holes 213 are provided, sandwiching the rotating shaft 30. However, the number of insertion holes 213 can be appropriately changed depending on the number of magnets 40 attached to the magnet fixing member 210.

[0039] Figure 6 is a perspective view showing the element fixing member 220 that constitutes the mounting member 200. The element fixing member 220 is fixed to the rotating shaft 30. A central hole 221 is provided at the radial center of the element fixing member 220, and the rotating shaft 30 is inserted into this central hole 221. A portion such as a keyway 222 is provided extending outward from the central hole 221 to synchronize the rotation of the slip ring device 160 and the element fixing member 220. A wiring recess 223 for passing wiring is also provided extending outward from the central hole 221.

[0040] Furthermore, the element fixing member 220 is provided with an element fixing groove 224. The element fixing groove 224 is a portion of the surface of the element fixing member 220 that is recessed for a predetermined length from the central hole 221 toward the outer diameter. The Hall element 50 is fitted into this element fixing groove 224, and a retaining member or the like (not shown) prevents the Hall element 50 from falling out.

[0041] In the configuration shown in Figure 6, for example, there are a total of seven element fixing grooves 224, spaced at 30-degree intervals. This allows for accurate detection of the rotation angle of the rotating shaft 30, as will be described later. However, the number of Hall elements 50 and magnets 40 are not limited to these and can be changed in various ways.

[0042] [5. Calculation method in angle measuring device 10] Next, the calculation algorithm for the angle measuring device 10 described above will be explained. In this angle measuring device 10, the pulse signals output from each Hall element 50 are decoded into angles. The calculation method for the angle measuring device 10 shown in Figure 2 will be explained below.

[0043] Assume that the output characteristic si(θ) of the i-th Hall element 50 with respect to the rotation angle θ when the rotation axis 30 in Figure 2 is rotated can be expressed as follows by a linear combination of basis functions {ξj(θ)}, j = 1, 2,..., n, as shown in equation (1).

number

[0044] However, C i j is the coefficient of the linear combination. Equation (1) is a vector ci = [ C ] obtained by arranging the linear combination coefficients. i 1C i 2···C i n ] T And the vector ξ(θ) = [ξ1 ξ2 ···ξn] formed by arranging the basis functions. T Using this, it can also be expressed as in equation (2) below.

number

[0045] When this equation is repeated for all m Hall elements, it becomes equation (3) below.

number

[0046] This equation is a system of equations that is generally nonlinear with respect to the angle θ. In measuring the rotation angle, it is necessary to convert (decode) the signal s obtained from the Hall element 50 into an angle θ, and to do so, it is necessary to solve this system of equations that is nonlinear. On the other hand, if we focus on the fact that the basis functions and coefficients are linearly separated, we can find an approximate solution of the basis function vector relatively easily. Focusing on this point, if we let the minimum norm solution of the basis function vector be ^ξ, we get the following equation (4).

number

[0047] However, C+ in the above formula (4) is the pseudo-inverse matrix of matrix C. Here, each element of ^ξ is ^ξ j Assuming that, for example, through operations such as those shown in the following formula (5), an approximate solution ^θ of the angle can be calculated.

Number

[0048] Regarding the specific calculation method of the inverse function ξ -1 1, it depends on what basis function system is adopted, and the suitable method varies. For example, in the case of the Fourier basis shown in the following formula (6), it can be approximated as in formula (7).

Number

Number

[0049] When obtaining the inverse function from the above formula (7), it becomes as follows in formula (8).

Number

[0050] In actual implementation, it is desirable to use the atan2 function from the perspective of singularity avoidance. If an approximate solution ^θ can be calculated, by using it as the initial value of the iterative solution method, a more accurate solution θ can be obtained. The problem of decoding in the angle measuring device 10 is basically a problem of calculating one piece of information from a large number of sensors, or in other words, a problem of solving an overdetermined system of equations. Therefore, considering minimizing the squared norm e2 of the residual of the equation shown in the following formula (9), it can be expressed as in the following formula (9).

Number

[0051] When differentiating the above formula (9), it becomes as follows in formula (10).

number

[0052] However, in equation (10) above, ξ′(θ) is a vector obtained by arranging the derivatives of the basis functions. Using this, the accuracy of the approximate solution can be recursively improved by equation (11) below.

number

[0053] However, in equation (11) above, k is the number of steps in the recurrence relation calculation, and λ is the coefficient for stabilization. The approximate solution of θ obtained when this recurrence relation is repeated a predetermined number of times is called the "final approximate solution".

[0054] [5. Examples of the angle measuring device 10 and the calculation results in the case of these examples] Next, Table 1 shows the specific placement positions and installation directions of each magnet 40 and each Hall element 50 when the angle measuring device 10 shown in Figure 2 is applied to the slip ring device 160. In Table 1, four Hall elements 50 are used, and each Hall element 50 is represented as Hall element 1 to 4. [Table 1]

[0055] Under the arrangement conditions shown in Table 1 above, the Hall element output characteristics when the Hall element unit 50 rotates were calculated using a predetermined magnetic dipole model, resulting in the graph shown in Figure 7. Furthermore, approximating this with a Fourier series of maximum order n = 15 yielded the result shown in Figure 8. At this time, the maximum output of the Hall element 50 is approximately 22.5 mT, while the approximation error by the Fourier series is approximately 4 × 10⁻¹⁰. -3 It was mT.

[0056] A matrix C was constructed from the approximation results using a Fourier series, and a vector s was constructed from the output of the Hall element 50 shown in Figure 7. The first-order term of the approximate value ^ξ of the basis function vector was calculated, resulting in Figure 9. Furthermore, the initial value and error of the approximate solution were calculated using the arctangent, resulting in Figure 10.

[0057] Initially, the maximum error was about 3.7 degrees, but λ = 2 × 10 -4 A more accurate approximate solution was obtained by performing 40 recurrence relation calculations, as shown in Figure 11, with a maximum error of 0.014 degrees. Here, the current slip ring device 160 uses a rotary encoder that provides 600 pulses per revolution of the wheel 130, and its resolution is 0.6 degrees, so at least in calculations, it can be seen that the accuracy is sufficient for practical use.

[0058] It should be noted that the angle measuring device 10 described above is not limited to the configuration shown in Table 1. For example, a configuration in which the direction of the magnetic flux of the permanent magnet 40 and the sensitivity axis of the Hall element 50 are arranged parallel to the rotation axis 30 is also conceivable. As a specific example of such a parallel arrangement with respect to the rotation axis 30, consider the configuration shown in Table 2. [Table 2]

[0059] Considering the configuration shown in Table 2, its characteristics are as shown in Figures 12 to 16. Figure 12 shows the Hall element output characteristics when the Hall element unit 50 rotates under the arrangement conditions in Table 2, calculated using a predetermined magnetic dipole model. Figure 13 shows the result of approximating the result shown in Figure 12 with a Fourier series of the highest order n = 20. Figure 14 shows the result of constructing a vector s from the output of the Hall element 50 as shown in Figure 12 and calculating the first-order term of the approximate value ^ξ of the basis function vector. Figure 15 shows the result of calculating the initial value of the approximate solution using the arctangent from the result shown in Figure 14. Figure 16 shows the result of calculating the approximate solution by recurrence relation from the state shown in Figure 15, with a stabilization coefficient of iterative calculation λ = 5 × 10⁻⁵ and 60 iterations.

[0060] The calculation results for the configuration shown in Table 2 demonstrate that, similar to the configuration shown in Table 1, the rotation angle can be measured with theoretically sufficient accuracy. Furthermore, the time required to calculate the final angle approximation was approximately 0.05 msec per sample using a typical desktop PC, which is a sufficient calculation speed for application to PQ measurements.

[0061] [6. Regarding variations] In the above embodiment, the magnet 40 is described as the physical field forming means 4. However, the physical field forming means 4 can be configured to form various physical fields, including a pair of parallel metal plates that form an electric field and a light source that forms an optical field. Furthermore, the fluctuation detection element 5 can be configured to detect various physical fields, including a voltmeter that detects voltage in the electric field and a photodetector that detects light intensity in the optical field.

[0062] [7. Addendum] The contents described in the above-mentioned embodiment can be understood as follows, for example, and can produce the following effects. [1] That is, the position measuring device 1 is A position measuring device 1 for measuring the relative position of a movable part (the other mounting member 3) with respect to a fixed part (one mounting member 2), A physical field forming means 4 is attached to one of the fixed part (one mounting member 2) and the movable part (the other mounting member 3) and forms a physical field PF1 represented by a predetermined physical quantity, Multiple fluctuation detection elements 5 are attached to the other of the fixed part (one mounting member 2) and the movable part (the other mounting member 3), and when the movable part moves relative to the physical field PF1, they output an analog signal corresponding to the fluctuation of physical quantities in the physical field PF1. A position conversion unit 6 converts the state of each analog signal output from multiple fluctuation detection elements 5 into a signal indicating the relative position of the moving part (the other mounting member 3), It is equipped with.

[0063] With this configuration, the analog signals corresponding to the fluctuations of physical quantities within the physical field PF1, output from multiple fluctuation detection elements 5, are converted into position-indicating signals by the position conversion unit 6 while maintaining the state of the analog signals. Therefore, the pulse counter required when using a rotary encoder is unnecessary, simplifying the configuration. Furthermore, the simple configuration of the angle measuring device allows for greater design flexibility.

[0064] Furthermore, the angle measuring device 10, which is an example of the position measuring device 1 described above, can be measured as follows, and can produce the following effects. [2] That is, An angle measuring device 10 for measuring the rotation angle of the rotation axis 30 relative to the fixed part 20, A physical field forming means 4 is attached to one of the fixed part 20 and the rotating shaft 30 and forms a physical field PF1 represented by a predetermined physical quantity, Multiple fluctuation detection elements 5 are attached to the other of the fixed part 20 and the rotating shaft 30, and when they move relatively within the physical field PF1, they output an analog signal corresponding to the fluctuation of physical quantities within the physical field PF1. An angle conversion unit 60 converts the state of each analog signal output from multiple fluctuation detection elements 5 into a signal indicating the rotation angle of the rotation axis 30, It is equipped with.

[0065] With this configuration, the analog signals corresponding to the fluctuations of physical quantities within the physical field PF1, output from multiple fluctuation detection elements 5, are converted into signals indicating the rotation angle by the angle conversion unit 60 while maintaining the state of the analog signals. Therefore, a pulse counter, which is necessary when using a rotary encoder, becomes unnecessary, and the configuration can be simplified. In addition, because the angle measuring device 10 has a simple configuration, it is possible to increase design flexibility.

[0066] [3] In the above embodiment, in item [2] above, The angle conversion unit 60 performs a functionization process that approximates the relationship between the output value of the analog signal and the angle as a function represented by a linear combination of a certain basis function system. Furthermore, it is preferable to calculate the rotation angle of the rotation axis 30 by performing an inverse operation using the pseudo-inverse matrix of the matrix obtained by approximation processing, which is a matrix of linear coupling coefficients.

[0067] In this way, it becomes possible to accurately calculate the rotation angle of the axis of rotation using relatively simple calculations.

[0068] [4] In addition, the above embodiments include, in addition to the contents described in either [2] or [3] above, or a combination thereof, In the angle conversion unit 60, it is preferable to perform an accuracy improvement process to improve the accuracy of the rotation angle by performing a recurrence process using a predetermined recurrence relation at least once on the initial rotation angle calculated by the inverse calculation.

[0069] By doing so, it becomes possible to further improve the accuracy of the calculated rotation angle.

[0070] [5] In addition, in this embodiment, the descriptions in any of [2] to [4] above, or a combination thereof, The physical field forming means 4 is a plurality of magnets 40 that form a static magnetic field. Preferably, the fluctuation detection element 5 is a plurality of Hall elements 50 that detect changes in the magnetic field due to the relative rotation of the magnet 40 in a static magnetic field.

[0071] In this configuration, the accuracy of rotation angle detection can be improved by detecting the change in the magnetic field formed by multiple magnets 40 with multiple Hall elements 50. Furthermore, by using small Hall elements 50, the angle measuring device 10 can be miniaturized, increasing design flexibility.

[0072] [5] Furthermore, the angle measurement method of this embodiment can be understood, for example, as follows, and can produce the following effects. In other words, an angle measurement method for measuring the rotation angle of the rotation axis 30 relative to the fixed part 20, A physical field forming means 4 is attached to one of the fixed part 20 and the rotating shaft 30 and forms a physical field PF1 represented by a predetermined physical quantity, Multiple fluctuation detection elements 5 are attached to the other of the fixed part 20 and the rotating shaft 30, and when they move relatively within the physical field PF1, they output an analog signal corresponding to the fluctuation of physical quantities within the physical field PF1. It has, The system includes a step of performing an angle conversion process that converts the state of each analog signal output from multiple fluctuation detection elements 5 into a signal indicating the rotation angle of the rotation axis 30.

[0073] In this way, the analog signals corresponding to the fluctuations of physical quantities within the physical field PF1, output from multiple fluctuation detection elements 5, are converted into signals indicating the rotation angle by the angle conversion unit 60 during the angle conversion process, while maintaining the state of the analog signals. Therefore, a pulse counter, which is necessary when using a rotary encoder, becomes unnecessary, and the configuration can be simplified. In addition, the angle measuring device 10 that performs the angle measurement method can have a simple configuration, increasing design flexibility. [Explanation of Symbols]

[0074] 1…Position measuring device, 2,3…Mounting member, 4…Physical field forming means, 5…Variation detection element, 6…Position conversion unit, 10…Angle measuring device, 20…Fixed part, 21…Inner cylinder surface, 30…Rotation shaft, 30a…Flange part, 40…Magnet, 50…Hall element, 60…Angle conversion unit, 100…Lateral pressure measuring device, 110…PQ wheelset, 120…Wheelset, 130…Wheel, 140…Axle, 150…Strain gauge, 160…Slip ring device, 170…Signal processing unit, 180…Calculation unit, 200…Mounting member, 210…Magnet fixing member, 211…Surface, 212…Magnet fixing part, 213…Insertion hole, 220…Element fixing member, 221…Center hole, 222…Keyway, 223…Wiring recess, 224…Element fixing groove, GF1…Magnetic field, PF1…Physical field

Claims

1. A position measuring device for measuring the relative position of a moving part with respect to a fixed part, A physical field forming means attached to one of the fixed portion and the movable portion, which forms a physical field represented by a predetermined physical quantity, Multiple fluctuation detection elements are attached to the other of the fixed portion and the movable portion, and when the movable portion moves relative to the physical field, they output an analog signal corresponding to the fluctuation of the physical quantity in the physical field. An angle conversion unit that converts the state of each analog signal output from the multiple fluctuation detection elements into a signal indicating the relative position of the moving part, A position measuring device characterized by comprising the following features.

2. An angle measuring device for measuring the rotation angle of a rotation axis relative to a fixed part, A physical field forming means attached to one of the fixed portion and the rotating shaft, which forms a physical field represented by a predetermined physical quantity, Multiple fluctuation detection elements are attached to the other of the fixed part and the rotating shaft, and when they move relatively within the physical field, they output an analog signal corresponding to the fluctuation of the physical quantity within the physical field. An angle conversion unit that converts the state of each analog signal output from the multiple fluctuation detection elements into a signal indicating the rotation angle of the rotation axis, An angle measuring device characterized by comprising the following features.

3. An angle measuring device according to claim 2, The angle conversion unit performs a functionization process that approximates the relationship between the output value of the analog signal and the angle to a function that can be represented by a linear combination of a certain basis function system. Furthermore, the rotation angle of the rotation axis is calculated by performing an inverse operation using the pseudo-inverse matrix of the matrix obtained by the approximation process, which is a matrix of linear coupling coefficients. An angle measuring device characterized by the following features.

4. An angle measuring device according to claim 3, The angle conversion unit performs an accuracy improvement process to improve the accuracy of the rotation angle by performing a recurrence process using a predetermined recurrence relation at least once on the initial rotation angle calculated by the inverse calculation. An angle measuring device characterized by the following features.

5. An angle measuring device according to claim 2, The physical field forming means is a plurality of magnets that form a static magnetic field, The fluctuation detection element is a plurality of Hall elements that detect changes in the magnetic field due to the relative rotation of the magnet within the static magnetic field. An angle measuring device characterized by the following features.

6. An angle measurement method for measuring the rotation angle of a rotation axis relative to a fixed part, A physical field forming means attached to one of the fixed portion and the rotating shaft, which forms a physical field represented by a predetermined physical quantity, Multiple fluctuation detection elements are attached to the other of the fixed part and the rotating shaft, and when they rotate relatively within the physical field, they output an analog signal corresponding to the fluctuation of the physical quantity within the physical field. It has, The process includes a step of performing an angle conversion operation that converts the state of each analog signal output from the multiple fluctuation detection elements into the rotation angle of the rotation axis, An angle measurement method characterized by the following features.

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