Displacement measurement system, and method for controlling the displacement measurement system

Abstract

When measuring displacement using the amplitude level of standing waves on a transmission line, the amplitude level of the standing waves follows a curve, and the slope differs depending on the location on the transmission line, resulting in different detection accuracy depending on the location. [Solution] A displacement measurement system characterized by comprising: a first coupler having one end terminated and receiving a first signal from the other end; a second coupler moving in the direction of extension of the first coupler while maintaining a constant distance from the first coupler; a transmitting unit receiving a second signal having the same frequency as the first signal; a receiving unit receiving the signal output from the transmitting unit; a first phase difference detection unit detecting the phase difference between the first signal and the signal output from the second coupler via the first coupler, and the signal output from the receiving unit via the transmitting unit; and a calculation unit calculating the position based on the phase difference information output from the first phase difference detection unit.

Description

Technical Field

[0001] The present invention relates to a displacement measurement system for measuring the displacement of a detector moving on a transmission line, and a control method for the displacement measurement system.

Background Art

[0002] In recent years, systems for measuring the displacement of a detector moving on a transmission line have been studied and developed. For example, in Non-Patent Document 1, a system has been proposed in which a standing wave is generated on a transmission line, the amplitude level and phase of the standing wave are acquired by a detector, and the displacement of the detector on the transmission line is measured.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the displacement measurement system described in Non-Patent Document 1, the amplitude level of the standing wave on the transmission line varies depending on the position. When a graph with the position on the horizontal axis and the amplitude level on the vertical axis is drawn, the graph forms a curve and the slope varies depending on the position on the transmission line. In particular, near the peak of the curve, the slope is gentle and the change in the amplitude level is small. Therefore, there is a problem that the detection accuracy becomes rough. In view of the above problems, an object of the present invention is to provide a displacement measurement system that can maintain a constant detection accuracy regardless of the position of the detector on the transmission line.

Means for Solving the Problems

[0005] One aspect of the present invention is characterized by comprising: a first coupler having one end terminated and receiving a first signal from the other end; a second coupler moving in the direction of extension of the first coupler while maintaining a constant distance from the first coupler; a transmitting unit receiving a second signal having the same frequency as the first signal; a receiving unit receiving a signal output from the transmitting unit; a first phase difference detection unit detecting the phase difference between the first signal and the signal output from the second coupler via the first coupler, and the signal output from the receiving unit via the transmitting unit; and a calculation unit calculating a position based on the phase difference information output from the first phase difference detection unit. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a system that can maintain a constant detection accuracy regardless of the position of the detector on the transmission line. [Brief explanation of the drawing]

[0007] [Figure 1] Configuration of the displacement measurement system according to Embodiment 1 [Figure 2] Configuration of the phase difference detection unit according to Embodiment 1 [Figure 3] Relationship between displacement and phase difference of transmission line coupler according to Embodiment 1 [Figure 4] Configuration of the displacement measurement system according to Embodiment 2 [Figure 5] Relationship between displacement and phase difference of transmission line coupler according to Embodiment 2 [Figure 6] Configuration of the displacement measurement system according to Embodiment 3 [Figure 7] Relationship between transmitted and received data waveforms and time according to Embodiment 3 [Figure 8] Configuration of the displacement measurement system according to Embodiment 4 [Figure 9] Relationship between displacement and phase difference of transmission line coupler according to Embodiment 4 [Figure 10] Configuration of the displacement measurement system according to Embodiment 5 [Figure 11] Relationship between displacement and phase difference of transmission line coupler according to Embodiment 5 [Figure 12] Configuration of the displacement measurement system according to Embodiment 6 [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings.

[0009] [Embodiment 1] Figure 1 shows the configuration of the displacement measurement system according to this embodiment. The displacement measurement system 100 consists of a first AC signal source 101, a first cable 102, a second cable 103, a first transmission line coupler 104, a first coupler 105, a transmitting unit 106, a propagation path 107, a receiving unit 108, a first phase difference detection unit 109, a counting unit 110, and a displacement calculation unit 111.

[0010] The first coupler 105, the receiving unit 108, the first phase difference detection unit 109, the counting unit 110, and the displacement calculation unit 111 move together in the direction in which the transmission line coupler 104 extends, that is, parallel to the signal transmission direction, due to the power of a motor or the like, which is not shown in the figure.

[0011] The first AC signal source 101 outputs a sine wave signal of an arbitrary frequency. The first transmission line coupler 104 is a linear transmission line. The first signal of the first AC signal source 101 is input from one end of the line via the first cable 102, and the other end is terminated with a resistor equal to the characteristic impedance of the transmission line. The first transmission line coupler 104 has a GND (not shown) as an element that determines the characteristic impedance of the transmission line. The transmission line couplers described hereinafter shall also have a GND (not shown). The first coupler 105 is a linear transmission line, which is shorter than the first transmission line coupler 104 and is assumed to move while maintaining a certain distance from the first transmission line coupler 104. The moving direction is parallel to the signal transmission direction of the transmission line coupler 104 and is in the forward or reverse direction of the signal transmission direction. Although both ends of the first coupler 105 are not terminated, it may be a transmission line coupler with a matched termination. The first coupler 105 is electromagnetically coupled to the first transmission line coupler 104, and the signal input to the first transmission line coupler 104 is received by the first coupler 105 via the electromagnetic coupling. The first transmission line coupler 104 is, for example, a transmission line in which signal lines and GND are arranged on a printed circuit board.

[0012] The transmitter 106 transmits the signal of the first AC signal source 101 input via the second cable 103 to the propagation path 107. The signal transmitted from the transmitter 106 is received by the receiver 108 through the transmission path 107. In this embodiment, it is assumed that the transmitter 106 is composed of a light-emitting element and the receiver 108 is composed of a light-receiving element, and the propagation path 107 is assumed to be air. Also, the light-emitting element and the light-receiving element are optically coupled, so that the signal transmitted from the transmitter 106 is received by the receiver 108. Light whose intensity changes at the frequency of the first AC signal source 101 propagates in the air as the propagation path 107.

[0013] The first phase difference detection unit 109 detects and outputs the phase difference between the signals received by the first coupler 105 and the receiving unit 108 respectively. When the phase difference output from the first phase difference detection unit 109 is 180 degrees or more, or -180 degrees or less, the counting unit 110 counts the number of times and changes the value of the stored counter. It may be counted up when the phase difference is 180 degrees or more and counted down when it is -180 degrees or less. Also, the first count may be incremented when the phase difference is 180 degrees or more, the second count may be incremented when the phase difference is -180 degrees or more, and calculations may be performed using the first count and the second count.

[0014] The moving unit 120 includes the first coupler 105, the receiving unit 108, the first phase difference detection unit 109, the counting unit 110, and the displacement calculation unit 111. It moves integrally in the direction in which the transmission line coupler 104 extends, that is, in the signal transmission direction or the reverse direction, by the power of a motor not shown in the figure. The displacement measurement system 100 of the present embodiment aims to measure this moving distance as displacement.

[0015] As described above, the moving unit 120 moves horizontally while maintaining a certain distance from the first transmission line coupler 104. By this movement, the first coupler 105 that receives a signal from the first transmission line coupler 104 and the receiving unit 108 that receives a signal from the transmitting unit 106 move horizontally in the same manner as the moving unit 120. Since the positions of the first coupler 105 and the receiving unit 108 are fixed within the same moving unit 120, they always change by the same distance. That is, when a certain position of the first coupler 105 and the receiving unit 108 is set as the initial position, the moving distances of the first coupler 105 and the receiving unit 108 from the initial position to the position after movement are the same due to this horizontal movement.

[0016] Displacement measurement by phase difference detection will be explained. When the moving part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the first cable 102, the first transmission line coupler 104, and the first coupler 105 is defined as φ1. Also, when the moving part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the second cable 103, the transmitter 106, the propagation path 107, and the receiver 108 is defined as φ2.

[0017] Let f be the frequency of the signal from the first AC signal source 101, v1 be the propagation speed of the signal from the first AC signal source 101 as it propagates through the first transmission line coupler 104, and v2 be the propagation speed as it propagates through the propagation path 107.

[0018] When the movable part 120 is displaced by a distance L from its initial position, the amount of phase change θ1 of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the first cable 102, the first transmission line coupler 104, and the first coupler 105 is expressed as follows.

[0019]

number

[0020] Similarly, the amount of phase change θ2 of the signal generated by propagation from the first AC signal source 101 through the second cable 103, the transmitting unit 106, the propagation path 107, and the receiving unit 108 to the first phase difference detection unit 109 is expressed as follows.

[0021]

number

[0022] When the movable part 120 is displaced by a distance L from its initial position, the phase difference Δθ detected by the first phase difference detection unit 109 is expressed as follows, based on the difference between the aforementioned equations 1 and 2.

[0023]

number

[0024] Rearranging equation 3 in terms of distance L from the initial position,

[0025]

number

[0026] Therefore, if there is a difference between the propagation speed v1 of the first transmission line coupler 104 and the propagation speed v2 of the propagation path 107, the distance L can be determined from the phase difference Δθ detected by the first phase difference detection unit 109, and thus displacement measurement becomes possible by detecting the phase difference.

[0027] The counting unit 110 sets the initial value of its internal counter to 0, and uses the output of the first phase difference detection unit 109 when the moving unit 120 is in its initial position as the initial phase difference. At that time, if the phase difference output from the first phase difference detection unit 109 exceeds 180 degrees as the moving unit 120 moves, it outputs a value obtained by adding 1 to the internal counter and subtracting 360 degrees, i.e., -180 degrees. Similarly, if the phase difference falls below -180 degrees, it outputs a value obtained by subtracting 1 to the internal counter and adding 360 degrees, i.e., 180 degrees. Therefore, Δθ can be calculated from the output of the counting unit 110 and the output of the first phase difference detection unit. In equation 4, the initial phases φ1 and φ2, the frequency f, and the signal transmission speeds v1 and v2 in each transmission path are all known values, so the displacement can be calculated from Δθ in the displacement calculation unit 111.

[0028] Figure 2 shows an example of the configuration of the phase difference detection unit according to this embodiment. The first phase difference detection unit 109 consists of a 90-degree phase shifter 201, multipliers 202 and 203, low-pass filters 204 and 205, and a polar coordinate transformation unit 206.

[0029] The 90-degree phase shifter 201, multipliers 202 and 203, and low-pass filters 204 and 205 are collectively referred to as the quadrature demodulation section.

[0030] The signal S0 of the first AC signal source 101 is S0=A0sin(2πft+θ0) (Equation 5) Let A0 be the amplitude of the signal S0 from the first AC signal source 101, t be time, and θ0 be the initial phase of the signal S0 from the first AC signal source 101 at t=0. If S1 is the signal that has propagated from the first AC signal source 101 to the first phase difference detection unit 109 via the first cable 102, the first transmission line coupler 104, and the first coupler 105 at position L of the moving unit 120, then S1 is expressed as follows. S1=A0A1sin(2πft+θ0-θ1) (Formula 6)

[0031] A1 represents the percentage of amplitude change generated by propagation from the first AC signal source 101 through the first cable 102, the first transmission line coupler 104, and the first coupler 105 to the first phase difference detection unit 109. If S2 is the signal that has propagated from the first AC signal source 101 through the second cable 103, the transmitter 106, the propagation path 107, and the receiver 108 to the first phase difference detection unit 109 at position L of the moving unit 120, then S2 is expressed as follows. S2=A0A2sin(2πft+θ0-θ2) (Formula 7)

[0032] A0 represents the rate of amplitude change generated by propagation from the first AC signal source 101 through the second cable 103, the transmitter 106, the propagation path 107, and the receiver 108 to the first phase difference detection unit 109. The multiplier 202 multiplies signal S1 and signal S2, and the result is

[0033]

number

[0034] It is represented as follows. When the output of the multiplier 202 is input to the low-pass filter 204, only the first term, which is the harmonic component of equation 8, passes through, and the signal S3 represented by equation 9 is obtained.

[0035]

number

[0036] The 90-degree phase shifter 201 delays the phase of signal S1 by 90 degrees. The resulting signal S4 is expressed by Equation 8.

[0037]

number

[0038] The multiplier 203 multiplies signal S2 and signal S4, and the result is:

[0039]

number

[0040] It is represented as follows. When the output of the multiplier 203 is input to the low-pass filter 205, only the second term, which is the harmonic component of equation 11, passes through, and the signal S5 represented by equation 12 is obtained.

[0041]

number

[0042] The polar coordinate transformation unit 206 transforms the orthogonal coordinates obtained by the orthogonal demodulation unit using equations 9 and 12 into polar coordinates and outputs the phase difference shown in equation 3.

[0043] Figure 3 shows the relationship between the displacement L of the movable part 120 and the phase difference Δθ according to this embodiment. The horizontal axis represents the displacement L of the movable part 120 relative to the initial position L=0mm, and the vertical axis represents the phase difference Δθ output by the first phase difference detection unit 109. The frequency f of the signal from the first AC signal source 101 is 10 GHz, and the phase difference φ2-φ1 at the initial position L=0mm is 133.2 degrees. The first transmission line coupler 104 is made of a glass epoxy substrate (FR4), and the propagation speed v1 when the signal from the first AC signal source 101 propagates through the first transmission line coupler 104 is 1.62 × 10⁻¹⁴. 8Let the speed be m / s. The propagation path 107 is the path from the light emitted from the light-emitting element of the transmitting unit 106 to the input of the receiving unit 108, and the propagation speed v2 when the signal from the first AC signal source 101 propagates through the propagation path 107 is 3.00 × 10⁻¹⁰. 8 Let's assume the speed is m / s.

[0044] As shown in Figure 3, the phase difference Δθ changes according to the displacement L, as expressed in Equation 3, because the propagation speed of the signal from the first AC signal source 101 differs depending on whether it propagates through the first transmission line coupler 104 or through the propagation path 107. Therefore, the displacement L of the moving part 120 can be obtained by measuring the phase difference Δθ with the first phase difference detection unit 109.

[0045] Furthermore, for example, there are two coupler positions that indicate a phase difference of 0, located around -22mm and 13mm. If the counting unit 110 adds 1 for every 180 degrees and subtracts 1 for every -180 degrees, then for example, it will output 0 at 13mm and -1 at -22mm. Therefore, even with the same phase difference, it is possible to identify the position of the first coupler 105 from the output value of the counting unit 110.

[0046] In this embodiment, the case in which the transmitting unit 106, propagation path 107, and receiving unit 108 are configured by optical propagation has been described. However, other configurations are also acceptable as long as the propagation time of the signal from the first AC signal source 101 in the propagation path 107 is different from that of the first transmission line coupler 104. For example, radio waves, sound waves, or other methods may be used. Cables, fibers, waveguides, transmission line couplers made of different substrates, slip rings, etc., may also be used. Similarly, the first transmission line coupler 104 and the first coupler 105 may also be made of cables, fibers, waveguides, slip rings, etc., as long as their propagation times are different from those of the propagation path 107.

[0047] [Embodiment 2] Figure 4 shows the configuration of the displacement measurement system according to this embodiment, where the propagation path 107 of Embodiment 1 is replaced with a second transmission line coupler 301 and a second coupler 302. The displacement measurement system 100 consists of a first AC signal source 101, a first cable 102, a second cable 103, a first transmission line coupler 104, a first coupler 105, a second transmission line coupler 301, a second coupler 302, a first phase difference detection unit 109, a counting unit 110, and a displacement calculation unit 111. Only the differences from Embodiment 1 will be explained.

[0048] The second transmission line coupler 301 is a linear transmission line, to which the signal from the first AC signal source 101 is input from one end of the line via the second cable 103, and the other end is matched and terminated with a resistance equal to the characteristic impedance of the transmission line. The second coupler 302 is a linear transmission line, shorter than the second transmission line coupler 301, and moves horizontally while maintaining a constant distance from the second transmission line coupler 301. The second coupler 302 is not terminated at both ends of the transmission line, but it may be a matched and terminated transmission line coupler. The second coupler 302 is electromagnetically coupled to the second transmission line coupler 301, and the signal input to the second transmission line coupler 301 is received by the second coupler 302 via electromagnetic coupling. The second transmission line coupler 301 is, for example, a transmission line on a printed circuit board with signal lines and GND arranged on it. The second coupler 302, like the first coupler 105, moves horizontally while maintaining a constant distance from the second transmission line coupler 301. This movement changes the position of the second coupler 302, which receives signals from the second transmission line coupler 301. The positions of the first coupler 105 and the second coupler 302 always change by the same distance due to this horizontal movement. That is, if the initial position is defined as the position where the movement distance of the first coupler 105 and the second coupler 302 is 0, then the distance from the initial position to the position after this horizontal movement is the same.

[0049] Displacement measurement by phase difference detection in this embodiment will now be described. When the movable part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the first cable 102, the first transmission line coupler 104, and the first coupler 105 is defined as φ1. Also, when the movable part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the second cable 103, the second transmission line coupler 301, and the second coupler 302 is defined as φ2. The phase difference Δθ is expressed by Equation 3, as in Embodiment 1.

[0050] Figure 5 shows the relationship between the displacement L of the movable part 120 and the phase difference Δθ according to this embodiment. The horizontal axis represents the displacement L of the movable part 120 relative to the initial position L=0mm, and the vertical axis represents the phase difference Δθ output by the first phase difference detection unit 109. The frequency f of the signal from the first AC signal source 101 is 10 GHz, and the phase difference φ2-φ1 at the initial position L=0mm is 56.8 degrees. The first transmission line coupler 104 is made of a glass epoxy substrate (FR4), while the second transmission line coupler 301 is made of a fluororesin substrate (Teflon®). The propagation speed v1 when the signal from the first AC signal source 101 propagates through the second transmission line coupler 301 is 2.22 × 10⁻¹⁰. 8 The propagation speed is assumed to be m / s. The difference in propagation speed is due to the difference in dielectric constant between glass epoxy and fluororesin. Note that glass epoxy and fluororesin are just examples; any resin material with a different dielectric constant or relative dielectric constant can be selected.

[0051] As shown in Figure 5, the phase difference Δθ changes according to the displacement L, as expressed in Equation 3, because the propagation speed of the signal from the first AC signal source 101 differs depending on whether it propagates through the first transmission line coupler 104 or through the propagation path 107. Therefore, the displacement L of the moving part 120 can be obtained by measuring the phase difference Δθ with the first phase difference detection unit 109.

[0052] Furthermore, for example, there are two coupler positions indicating a phase difference of -90 degrees, located around -37mm and -25mm, but the output values ​​of the counting unit 110 are different. Therefore, even with the same phase difference, the position of the first transmission line coupler 105 can be identified from the output value of the counting unit 110.

[0053] As described above, with this embodiment, the position of the first coupler 105 relative to the first transmission line coupler 104 can be calculated by the displacement calculation unit 111 based on the output of the first phase difference detection unit 109 and the output of the counting unit 110.

[0054] [Embodiment 3] Figure 6 shows the configuration of the displacement measurement system according to this embodiment. It shows a configuration that realizes data transmission and displacement measurement simultaneously. In addition to the system configuration of Embodiment 1, it consists of a data signal source 401, an adder 402, a third cable 403, a low-pass filter 404, a comparator 405, and a constant voltage source 406. The data signal source 401 represents an arbitrary digital data signal to be transmitted. The adder 402 adds the first AC signal source 101 and the arbitrary digital data signal represented by the data signal source 401 and outputs the result.

[0055] Displacement measurement by phase difference detection in this embodiment will now be described. When the moving unit 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 is defined as φ1. This propagation occurs via the first cable 102, adder 402, third cable 403, first transmission line coupler 104, and first coupler 105. Furthermore, when the moving unit 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 via the second cable 103, transmitter 106, propagation path 107, and receiver 108 is defined as φ2. The phase difference Δθ is expressed by Equation 3, as in Embodiment 1. The relationship between the displacement L of the moving unit 120 and the phase difference Δθ in this embodiment is shown in Figure 3, the same as in Embodiment 1.

[0056] Data transmission will now be described. In this embodiment, in addition to measuring the displacement L of the moving part 120, any digital data signal represented by the data signal source 401 can be transmitted to the moving part 120 without contact. The digital data signal added to the signal of the first AC signal source 101 is input to the first transmission line coupler 104 in the same way as the signal of the first AC signal source 101, and is received by the first coupler 105 via electromagnetic coupling. If the digital data signal is sufficiently slower than the frequency f of the signal of the first AC signal source 101, the low-pass filter 404 separates the digital data signal from the signal of the first AC signal source 101. That is, the signal of the first AC signal source 101 is cut off by the low-pass filter, and only the digital data signal is input to the comparator 405.

[0057] The comparator 405 outputs a signal corresponding to a logical value of 1 if the signal input through the low-pass filter 404 is higher than the voltage level output by the constant voltage source 406, and outputs a signal corresponding to a logical value of 0 if the signal is lower than the voltage level output by the constant voltage source 406. This comparator 405 shapes the waveform of the signal received by the first coupler 105 via electromagnetic coupling and reconstructs the original digital data signal represented by the data signal source 401. Note that the means for reconstructing the digital data signal is not limited to the comparator, and waveform shaping may be performed by other means.

[0058] Figure 7 shows the relationship between the transmitted and received data waveforms and time according to this embodiment. In Figure 7(a), the horizontal axis represents time and the vertical axis represents the output voltage of the data signal source 401. In Figure 7(b), the horizontal axis represents time and the vertical axis represents the output voltage of the low-pass filter 404. In Figure 7(c), the horizontal axis represents time and the vertical axis represents the output voltage of the comparator 405. The digital data signal from the data signal source 401 is a square wave, and when transmitted to the first coupler 105 via electromagnetic field coupling, it becomes a differential waveform, which is then regenerated into a square wave by the comparator 405. From the above, by adding the signal from the first AC signal source 101 and the digital data signal from the data signal source 401 and transmitting them to the first coupler 105, the digital data signal can be transmitted to the mobile unit 120 while obtaining the displacement L of the mobile unit 120.

[0059] In this embodiment, a low-pass filter was used to separate the signal from the first AC signal source 101 from the digital data signal from the data signal source 401, but this is not the only option. For example, if the signal from the first AC signal source 101 has a lower frequency than the digital data signal, a high-pass filter may be used instead.

[0060] As described above, with this embodiment, the position of the first coupler 105 relative to the first transmission line coupler 104 can be calculated by the displacement calculation unit 111 based on the output of the first phase difference detection unit 109 and the output of the counting unit 110. Furthermore, the digital data signal of the data signal source 401 can be output from the comparator 405 located on the moving unit 120. In other words, data can be transmitted to the moving unit 120 without contact while detecting the position of the moving unit 120, eliminating the risk of wear and breakage due to cable movement compared to data transmission using cable connections, etc. Moreover, since the position information of the first coupler 105 is obtained at the same time, it is possible to add control to change the amplification amount of the signal strength amplifier according to the position, for example, when the signal-to-noise ratio of data transmission changes depending on the position.

[0061] [Embodiment 4] Figure 8 shows the configuration of the displacement measurement system according to this embodiment. In addition to the system configuration of Embodiment 1, it consists of a second AC signal source 501, a fourth cable 502, a fifth cable 503, bandpass filters 504, 505, 506, 507, and a second phase difference detection unit 508. Note that the counting unit 110 is not required and is therefore not included in the configuration. The second AC signal source 501 generates a sine wave signal with a different frequency from the first AC signal source 101.

[0062] The first transmission line coupler 104 receives signals from the first AC signal source 101 and the second AC signal source 501, respectively, via the first cable 102 and the fourth cable 502. The two signals with different frequencies that are input to the first transmission line coupler 104 are transmitted to the first coupler 105 via electromagnetic field coupling and input to the bandpass filters 504 and 506. The bandpass filters 504 and 506 have different frequencies that they can pass through, allowing the signals from the first AC signal source 101 and the second AC signal source 501 to pass through, respectively. That is, the first phase difference detection unit 109 receives the signal from the first AC signal source 101, and the second phase difference detection unit 508 receives the signal from the second AC signal source 501.

[0063] The transmitter 106 receives signals from the first AC signal source 101 and the second AC signal source 501, respectively, via the second cable 103 and the fifth cable 503. The two signals with different frequencies input to the transmitter 106 are transmitted to the receiver 108 via optical propagation in the propagation path 107 and input to the bandpass filters 505 and 507. The bandpass filters 505 and 507 have different frequencies that they can pass through, allowing the signals from the first AC signal source 101 and the second AC signal source 501 to pass through, respectively. That is, the first phase difference detection unit 109 receives the signal from the first AC signal source 101, and the second phase difference detection unit 508 receives the signal from the second AC signal source 501.

[0064] Therefore, the first phase difference detection unit 109 detects the phase difference between the signal propagated from the first AC signal source 101 via the first transmission line coupler 104 and the signal propagated from the first AC signal source 101 via the propagation path 107. The second phase difference detection unit 508 detects the phase difference between the signal propagated from the second AC signal source 501 via the first transmission line coupler 104 and the signal propagated from the second AC signal source 501 via the propagation path 107. The signal propagation paths from the first AC signal source 101 to the first phase difference detection unit 109 and from the second AC signal source 501 to the second phase difference detection unit 508 are the same. However, since the frequencies of the first AC signal source 101 and the second AC signal source 501 are different, the phase differences detected by the first phase difference detection unit 109 and the phase difference detection unit 508 are different, and each detects an individual phase difference with respect to the position of the moving part 120. The position of the moving part 120 is determined from the two phase difference information obtained from the first phase difference detection unit 109 and the second phase difference detection unit 508. This makes it possible to detect the position of the moving part 120 without using the internal counter information of the counting unit 110.

[0065] Displacement measurement by phase difference detection in this embodiment will now be described. When the moving part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 is defined as φ1. This propagation occurs via the first cable 102, the first transmission line coupler 104, the first coupler 105, and the bandbus filter 504. Furthermore, when the moving part 120 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 is defined as φ2. This propagation occurs via the second cable 103, the transmitter 106, the propagation path 107, the receiver 108, and the bandbus filter 505. The phase difference Δθ is expressed by Equation 3, as in Embodiment 1. The relationship between the displacement L of the moving part 120 and the phase difference Δθ in this embodiment is shown in Figure 3, the same as in Embodiment 1.

[0066] Similarly, φ1' is the amount of phase change in the signal generated by propagation from the second AC signal source 501 to the second phase difference detection unit 508 via the fourth cable 502, the first transmission line coupler 104, the first coupler 105, and the bandbus filter 506. Also, when the mobile unit 120 is in its initial position, φ2' is the amount of phase change in the signal generated by propagation from the second AC signal source 501 to the second phase difference detection unit 508. This propagation occurs via the fifth cable 503, the transmitter 106, the propagation path 107, the receiver 108, and the bandbus filter 507. If the frequency of the second AC signal source 501 is f' and the phase difference detected by the second phase difference detection unit 508 is Δθ', then the equation takes the same form as equation 3 in Embodiment 1.

[0067]

number

[0068] This is represented by the following. The relationship between the displacement L of the movable part 120 and the phase difference Δθ' in this embodiment is shown in a different graph than in Figure 3 of Embodiment 1 because the frequency of the second AC signal source 501 is different.

[0069] Figure 9 shows the relationship between the displacement L of the transmission line coupler and the phase differences Δθ and Δθ' according to this embodiment. Similar to Embodiment 1, the frequency f of the signal from the first AC signal source 101 is 10 GHz, and the phase difference φ2-φ1 output by the first phase difference detection unit 109 at the initial position L=0 mm is 133.2 degrees. Also, the propagation speed v1 is 1.62 × 10⁻⁶ 8 m / s, propagation speed v2 = 3.00 × 10⁻¹⁰ 8 Let the speed be m / s. The frequency f' of the signal from the second AC signal source 501 is 11 GHz, and the phase difference φ2'-φ1' output by the second phase difference detection unit 508 at the initial position L=0 mm is 71.0 deg.

[0070] Figure 9(a) shows the displacement L of the moving part 120 relative to its initial position L=0mm on the horizontal axis, and the phase difference Δθ output by the first phase difference detection unit 109 and the phase difference Δθ' output by the second phase difference detection unit 508 on the vertical axis. Since the frequency f of the first AC signal source 101 and the frequency f' of the second AC signal source 501 are different, the phase difference Δθ output by the first phase difference detection unit 109 and the phase difference Δθ' output by the second phase difference detection unit 508 are different. Figure 9(b) shows the displacement L of the moving part 120 relative to its initial position L=0mm on the horizontal axis, and the difference between the phase differences output by the two phase difference detection units 109 and 508 on the vertical axis. From Figure 9(b), it can be seen that the difference between the phase differences output by the two phase difference detection units 106 and 508 with respect to the displacement L of the moving part 120 is an eigenvalue. Therefore, the position of the moving part 120 is uniquely determined from the difference between the two phase differences. In other words, by detecting the phase difference using two frequencies, the absolute position of the moving unit 120 can be determined without using the counting unit 110.

[0071] As described above, with this embodiment, the absolute position of the moving part 120 can be calculated by the difference between the outputs of the two phase difference detection units 109 and 508. Although an example in which the two frequencies f and f' are separated by a bandpass filter is shown, the wavelengths of the light propagated in the transmitting unit 106, propagation path 107, and receiving unit 108 may be used to separate and propagate the signals to the phase difference detection units 109 and 508 without using the bandpass filters 505 and 507. Also, as with Embodiment 1, the transmitting unit 106, propagation path 107, and receiving unit 108 may use radio waves, sound waves, or other means, as long as the propagation speeds in the first transmission line coupler 104 and the propagation path 107 are different. In addition, cables, fibers, waveguides, transmission line couplers, slip rings, and other means with different substrates may be used. Similarly, the first transmission line coupler 104 and the first coupler 105 may also be made of cables, fibers, waveguides, slip rings, or other materials, as long as they have different propagation times from the propagation path 107.

[0072] Alternatively, the first AC signal source 101 and the second AC signal source 501 may be combined into a single variable frequency AC signal source, and the first phase difference detection unit 109 and the second phase difference detection unit 508 may be combined into a single phase difference detection unit, with the signal propagated to the phase difference detection units 109 and 508 in a time-division manner. In this case, the bandpass filters 504, 505, 506, and 507 become unnecessary.

[0073] [Embodiment 5] Figure 10 shows the configuration of the displacement measurement system according to this embodiment. In Figure 10(a), the displacement measurement system 600 consists of a fixed part 601 and a rotating part 602. In Figure 10(b), the fixed part 601 consists of a first AC signal source 101, a first cable 102, a second cable 103, a first transmission line coupler 104, and a second transmission line coupler 301. The first transmission line coupler 104 and the second transmission line coupler 301 are concentric circles with different radii, one end of which is connected to the first AC signal source 101 via the first cable 102, and the other end of which is terminated with a resistor.

[0074] In Figure 10(c), the rotating section 602 consists of a first coupler 105, a second coupler 302, and a first phase difference detection unit 109. The first coupler 105 and the second coupler 302 are concentric arcs with different diameters, one end of which is connected to the first phase detection unit 109, and the other end is terminated with a resistor. The rotating section 602 is rotatable around the center of the circle of the fixed section 601 as its axis of rotation, and the first coupler 105 and the second coupler 302 are arcs with the same radius as the first transmission line coupler 104 and the second transmission line coupler 301 in Figure 10(b). As a result, the first coupler 105 can rotate on the first transmission line coupler 104, and the second coupler 302 can rotate on the second transmission line coupler 301, while maintaining a constant distance. The signal from the first AC signal source 101, input to the first transmission line coupler 104, propagates to the first coupler 105 via electromagnetic field coupling. Similarly, the signal from the second AC signal source 101, input to the second transmission line coupler 301, propagates to the second coupler 302 via electromagnetic field coupling.

[0075] In the above configuration, the displacement measurement system according to this embodiment can detect the displacement of the rotation angle of the rotating part 602 from the phase difference output from the first phase difference detection unit 109. Because the radii of the first transmission line coupler 104 and the second transmission line coupler 301 are different, the amount of change in the propagation distance between the first transmission line coupler 104 and the second transmission line coupler 301 with respect to the displacement of the rotation angle is different. This generates a phase difference, and the displacement of the rotation angle can be determined.

[0076] Displacement measurement by phase difference detection in this embodiment will be described. When the rotating part 602 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 through the first cable 102, the first transmission line coupler 104, and the first coupler 105 to the first phase difference detection unit 109 is defined as φ1. Also, when the rotating part 602 is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 through the second cable 103, the second transmission line coupler 301, and the second coupler 302 to the first phase difference detection unit 109 is defined as φ2. The frequency of the signal from the first AC signal source 101 is defined as f, and the propagation speed when the signal from the first AC signal source 101 propagates through the first transmission line coupler 104 and the second transmission line coupler 301 is defined as v1.

[0077] Let α be the rotational angle displacement of the rotating part 602 from its initial position, r1 be the radius of the first transmission line coupler 104, and r2 be the radius of the second transmission line coupler 301. When the rotating part 602 is displaced by a rotational angle α from its initial position, the phase change amount θ1 of the signal generated by propagation from the first AC signal source 101 through the first cable 102, the first transmission line coupler 104, and the first coupler 105 to the first phase difference detection unit 109 is:

[0078]

number

[0079] It is expressed as follows. Similarly, the amount of phase change θ2 of the signal generated by propagation from the first AC signal source 101 through the second cable 103, the second transmission line coupler 301, and the second coupler 302 to the first phase difference detection unit 109 is,

[0080]

number

[0081] It is expressed as follows. Therefore, the phase difference Δθ output by the first phase difference detection unit 109 is

[0082]

number

[0083] This is represented as follows. Therefore, because the radii of the first transmission line coupler 104 and the second transmission line coupler 301 are different, the displacement amount α of the rotation angle can be determined from the phase difference Δθ detected by the first phase difference detection unit 109, and thus the displacement angle can be measured by detecting the phase difference.

[0084] Figure 11(a) shows the relationship between the rotational displacement α and the phase difference Δθ of the rotating part 602 according to this embodiment. The horizontal axis represents the displacement α of the rotating part 602 with respect to the initial position α = 0 deg., and the vertical axis represents the phase difference Δθ output by the first phase difference detection unit 109. The frequency f of the signal from the first AC signal source 101 is 8.6 GHz, and the phase difference φ2 - φ1 at the initial position α = 0 deg. is -76.3 deg. The first transmission line coupler 104 is made of a glass epoxy substrate (FR4), and the propagation speed v1 is 1.68 × 10⁻⁶. 8 The speed is set to m / s. The radius of the first transmission line coupler 104 is set to 16.25 mm, and the radius of the second transmission line coupler 301 is set to 19.35 mm.

[0085] The propagation distance for rotational displacement α differs depending on whether the signal from the first AC signal source 101 propagates through the first transmission line coupler 104 or through the second transmission line coupler 301. Therefore, as shown in equation 14, the phase difference Δθ changes according to the rotational displacement α, as illustrated in Figure 11. Thus, the rotational displacement α of the rotating part 602 can be obtained by measuring the phase difference Δθ with the first phase difference detection unit 109.

[0086] Furthermore, if the transmission line lengths of the first transmission line coupler 104 and the second transmission line coupler 301 are natural multiples of the wavelength at the frequency of the first AC signal source 101, the phase difference Δθ will be the same when the rotational displacement α is 0 degrees and when it is 360 degrees. If the transmission line length of the first transmission line coupler 104 is a natural multiple of the wavelength, the amount of phase change of the signal from the first AC signal source 101 will be the same at the end of the first transmission line coupler 104 connected to the first cable 102 and at the other end terminated by the resistor. Therefore, when the rotational displacement α increases from 0 degrees and reaches 360 degrees, the phase of the signal input from the first coupler 105 to the first phase difference detection unit 109 will be the same as the phase at 0 degrees. Similarly, if the transmission line length of the second transmission line coupler 301 is a natural number multiple of the wavelength, the amount of phase change of the signal from the first AC signal source 101 will be equal at the end of the second transmission line coupler 301 connected to the second cable 103 and at the other end terminated by the resistor. Therefore, when the rotational displacement α increases from 0 degrees and reaches 360 degrees, the phase of the signal input from the second coupler 302 to the first phase difference detection unit 109 will be equal to the phase at 0 degrees.

[0087] As a result, the phase difference Δθ is the same value when the rotational displacement α is 0 degrees and when it is 360 degrees. Figure 11(b) shows the relationship between the phases θ1 and θ2 with respect to the rotational displacement α of the rotating part 602. The transmission line length and the frequency of the signal from the first AC signal source 101 are adjusted so that the phase θ1 of the signal propagating through the shorter first transmission line coupler 104 is 5 wavelengths per revolution, and the phase of the signal propagating through the longer second transmission line coupler 301 is 6 wavelengths per revolution. As a result, the phase difference Δθ is the same value for both phases θ1 and θ2 when the rotational displacement α is 0 degrees and when it is 360 degrees. Compared to the case where the phase difference Δθ is different when the rotational displacement α is 0 degrees and when it is 360 degrees, the value of the phase difference detector 109 near 0 degrees is eliminated, so the phase difference can be detected stably and accurately, and the rotational displacement α can be obtained with high precision.

[0088] Furthermore, because the difference in transmission line length between the first transmission line coupler 104 and the second transmission line coupler 301 is one wavelength, the phase difference Δθ with respect to the rotational displacement α shown in Figure 11(a) is uniquely determined. Therefore, the absolute position of the rotation angle of the rotating part 602 can be determined without using the counting unit 110.

[0089] As described above, with this embodiment, the rotation angle of the rotating part 602 can be calculated by the output of the first phase difference detection unit 109. In this embodiment, data transmission may be performed simultaneously, as in Embodiment 3. Two channels of contactless data transmission are possible from the first transmission line coupler 104 to the first coupler 105, and from the second transmission line coupler 301 to the second coupler 302. The two channels may consist of two single-ended transmission channels or one differential transmission pair. The data transmission direction may also be reversed, from the first coupler 105 to the first transmission line coupler 104, and from the second coupler 302 to the second transmission line coupler 301. Alternatively, one side may be reversed to perform bidirectional data transmission. The number of data transmission channels can also be increased concentrically. In addition, termination resistors are connected to the first coupler 105 and the second coupler 302, but termination resistors may not be necessary if the signal frequency of the first AC signal source 101 or the data rate for data transmission is low. In that case, the connection point with the first phase difference detection unit 109 does not have to be at the end; for example, it may be at the center.

[0090] [Embodiment 6] Figure 12 shows the configuration of the displacement measurement system according to this embodiment. Similar to Embodiment 5, it has a rotating part, but it is arranged in a concentric cylindrical shape. The first transmission line coupler 104 and the second coupler 302 are on the fixed side, and the first coupler 105 and the second transmission line coupler 301 are arranged inside them as the rotating side. All four elements are arranged in a concentric circle, and the first coupler 105 and the second transmission line coupler 301 on the rotating side rotate around the same axis. Since the first transmission line coupler 105 is on the outer fixed side and the second transmission line coupler 301 is on the inner rotating side, the radii of the concentric circles at the positions in which each is arranged are different.

[0091] The signal from the first AC signal source 101 is input to the first transmission line coupler 104 via the first cable 102. The first coupler 105 is capable of circulating while maintaining a constant distance from the first transmission line coupler 104. The signal from the first AC signal source 101 input to the first transmission line coupler 104 propagates to the first coupler 105 via electromagnetic field coupling and is input to the first phase difference detection unit 109. The first transmission line coupler 104 has ends (not shown), one end of which is connected to the first cable 102, and the other end is terminated with a resistor. The first transmission line coupler 104 may be divided into multiple elements in the circumferential direction. In that case, the first cable 102 is connected to one end of each element, and the signal from the first AC signal source 101 is input to all elements. The other end of each element of the first transmission line coupler 104 is terminated with a resistor. With the above configuration, at any rotation angle of the first coupler 105, the signal from the first AC signal source 101 propagates from the first transmission line coupler 104 to the first coupler 105 and is input to the first phase difference detection unit 109.

[0092] Furthermore, the signal from the first AC signal source 101 is input to the second coupler 302 via the second cable 103. The second transmission line coupler 301 is capable of circulating while maintaining a constant distance from the second coupler 302. The signal from the first AC signal source 101 input to the second coupler 302 propagates to the second transmission line coupler 301 via electromagnetic field coupling and is input to the first phase difference detection unit 109. The second transmission line coupler 301 has ends (not shown), one end of which is connected to the first phase difference detection unit 109, and the other end is terminated with a resistor. The second transmission line coupler 301 may be divided into multiple elements in the circumferential direction. In this case, the first phase difference detection unit 109 is connected to one end of each element, and the signal from the first AC signal source 101 is input to the first phase difference detection unit 109 regardless of which element of the second transmission line coupler 301 the signal from the second coupler 302 propagates to. The other end of each element of the second transmission line coupler 301 is terminated with a resistor. With this configuration, at any rotation angle of the second transmission line coupler 301, the signal from the first AC signal source 101 propagates from the second coupler 302 to the second transmission line coupler 301 and is input to the first phase difference detection unit 109.

[0093] In the above configuration, the displacement measurement system according to this embodiment can detect the displacement of the rotation angle of the first coupler 105 and the second transmission line coupler 301, which are located on the rotating side, from the phase difference output from the first phase difference detection unit 109. Because the radii of the first transmission line coupler 104 and the second transmission line coupler 301 are different, the amount of change in the propagation distance of the first transmission line coupler 104 and the second transmission line coupler 301 with respect to the displacement of the rotation angle is different. This generates a phase difference, and the displacement of the rotation angle can be determined.

[0094] Displacement measurement by phase difference detection in this embodiment will be described. When the rotating side is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 through the first cable 102, the first transmission line coupler 104, and the first coupler 105 to the first phase difference detection unit 109 is defined as φ1. Also, when the rotating side is in its initial position, the phase change amount of the signal generated by propagation from the first AC signal source 101 through the second cable 103, the second coupler 302, and the second transmission line coupler 301 to the first phase difference detection unit 109 is defined as φ2. The frequency of the signal from the first AC signal source 101 is defined as f, and the propagation speed when the signal from the first AC signal source 101 propagates through the first transmission line coupler 104 and the second transmission line coupler 301 is defined as v1.

[0095] Let α be the displacement of the rotation angle from the initial position of the rotating side, r1 be the radius of the first transmission line coupler 104, and r2 be the radius of the second transmission line coupler 301. The phase change θ1 of the signal generated by propagation from the first AC signal source 101 to the first phase difference detection unit 109 when the rotating side is displaced by a rotation angle α from the initial position is expressed by equation 14. The signal is propagated via the first cable 102, the first transmission line coupler 104, and the first coupler 105.

[0096] Similarly, the amount of phase change θ2 of the signal generated by propagation from the first AC signal source 101 through the second cable 103, the second coupler 302, and the second transmission line coupler 301 to the first phase difference detection unit 109 is expressed by Equation 15. Therefore, the phase difference Δθ output by the first phase difference detection unit 109 is expressed by Equation 16, similar to Embodiment 5. As a result, because the radii of the first transmission line coupler 104 and the second transmission line coupler 301 are different, the amount of rotational angle displacement α can be determined from the phase difference Δθ detected by the first phase difference detection unit 109, thus enabling displacement measurement by detecting the phase difference.

[0097] As described above, in this embodiment, the rotation angles of the first coupler 105 and the second transmission line coupler 301, which are located on the rotating side, can be calculated by the output of the first phase difference detection unit 109. In this embodiment, data transmission may be performed simultaneously, as in embodiments 3 and 5. Bidirectional data transmission is possible between the fixed side and the rotating side without contact, from the first transmission line coupler 104 on the fixed side to the first coupler 105 on the rotating side, and from the second transmission line coupler 301 on the rotating side to the second coupler 302 on the fixed side. The direction of data transmission may also be reversed, from the first coupler 105 to the first transmission line coupler 104, and from the second coupler 302 to the second transmission line coupler 301. Alternatively, only one direction may be reversed. The number of data transmission channels can also be increased by arranging them side by side on the cylindrical axis.

[0098] Furthermore, the first coupler 105 may be connected to the first phase difference detection unit 109 at its end or at its center. The second coupler 302 may be connected to the second cable 103 at its end or at its center. In addition, termination resistors may be connected to the ends of the first coupler 105 and the second coupler 302.

[0099] Alternatively, the first AC signal source 101 may be placed on the rotating side and connected to the first coupler 105 and the second transmission line coupler 301. In that case, the first phase difference detection unit 109 may be placed on the stationary side and connected to the first transmission line coupler 104 and the second coupler 302. [Explanation of Symbols]

[0100] 100 Displacement Measurement System 101 First AC signal source 102 First Cable 103 Second cable 104 First transmission line coupler 105 The first coupler 106 Transmitter 107 Propagation Path 108 Receiving Unit 109 First phase difference detection unit 110 Counting Unit 111 Displacement Calculation Unit 120 Move

Claims

1. A first coupler, one end of which is terminated and the other end of which a first signal is input, A second coupler moves in the direction of extension of the first coupler while maintaining a certain distance from the first coupler, A second signal having the same frequency as the first signal is input, and a transmitting unit transmits the signal. A receiving unit that receives the signal output from the transmitting unit, A first phase difference detection unit detects the phase difference between the first signal being output from the second coupler via the first coupler and the second signal being output from the receiving unit via the transmitting unit. Calculation unit that calculates position based on phase difference information output from the first phase difference detection unit A displacement measurement system characterized by having the following features.

2. The displacement measuring system according to claim 1, further comprising a counting unit that changes the value of a counter each time the phase difference exceeds 180 degrees.

3. The displacement measuring system according to claim 2, characterized in that the calculation unit calculates the position of the second coupler relative to the first coupler based on the phase difference and the value of the counter output from the counting unit.

4. The first phase difference detection unit is, The displacement measurement system according to claim 1, characterized in that it outputs a phase difference by orthogonally demodulating two signals, the signal output from the second coupler and the signal output from the receiving unit, and converting them to polar coordinates.

5. The displacement measuring system according to claim 2, characterized in that when the second coupler moves toward the end of the first coupler to which a signal is input, and the phase difference becomes 180 degrees, the counting unit subtracts 1 from the value of the counter.

6. The displacement measuring system according to claim 2, characterized in that when the second coupler moves in the direction in which the termination resistor is positioned in the first coupler, and the phase difference becomes 180 degrees, the counting unit increments the value of the counter by 1.

7. The transmitting unit includes a light-emitting element. The displacement measurement system according to claim 1, characterized in that the receiving unit is equipped with a light-receiving element, and the second signal is input to the first phase difference detection unit via optical coupling.

8. A first coupler, one end of which is terminated and the other end of which a first signal is input, A second coupler moves in the direction of extension of the first coupler while maintaining a certain distance from the first coupler, A third coupler, one end of which is terminated and the other end of which a second signal is input, A fourth coupler moves in the direction of extension of the third coupler while maintaining a certain distance from the third coupler, A first phase difference detection unit detects the phase difference between the first signal output from the second coupler via the first coupler and the second signal output from the fourth coupler via the third coupler. Calculation unit that calculates position based on phase difference information output from the first phase difference detection unit A displacement measurement system characterized by having the following features.

9. The first coupler is configured on the first circuit board, and the third coupler is configured on the second circuit board. The displacement measurement system according to claim 8, characterized in that the dielectric constants of the first substrate and the second substrate are different.

10. The displacement measuring system according to claim 8, further comprising a counting unit that changes the value of a counter each time the phase difference exceeds 180 degrees.

11. The displacement measuring system according to claim 10, characterized in that the calculation unit calculates the position of the second coupler relative to the first coupler based on the phase difference and the value of the counter output from the counting unit.

12. A first coupler, one end of which is terminated and the other end of which a first signal is input, A control method controlled by a displacement measuring system having a second coupler that moves in the direction of extension of the first coupler while maintaining a constant distance from the first coupler, A second signal having the same frequency as the first signal is input, and a transmission step is performed to transmit the signal. A receiving step which receives the signal transmitted in the transmission step, A phase difference detection step for detecting the phase difference between the signal output from the second coupler and the signal received and output in the receiving step, A control method characterized by having a calculation step that calculates the position based on the phase difference information detected in the phase difference detection step.

Images