Dual-coil magnetostrictive sensor waveguide assembly

Abstract

We provide a dual-coil magnetostrictive sensor waveguide assembly. [Solution] The waveguide assembly includes a waveguide having a longitudinal axis and a magnetostrictive response pickup. The pickup includes a first coil oriented within a first plane substantially parallel to the longitudinal axis and a second coil connected in series with the first coil, which is oriented within a second plane substantially parallel to the longitudinal axis. The central axis of the first coil is displaced along the longitudinal axis by a coil separation distance from the central axis of the second coil.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to magnetostrictive position measurement, and more specifically, to magnetostrictive position measurement systems and methods that utilize both longitudinal and torsional waves of magnetostrictive responses.

Background Art

[0002] Magnetostrictive position measurement systems or linear position transducers are robust and high-resolution devices that have proven useful in many measurement and control applications. Magnetostrictive linear position systems generally include a wire waveguide and a target magnet having a position that can vary with respect to the waveguide. The position of the target magnet along the waveguide corresponds to the measured position.

[0003] The excitation generator of a magnetostrictive position measurement system generates an electrical excitation signal, such as a current pulse, which is conducted through the waveguide. This generates a magnetic field around the waveguide that interacts with the magnetic field of the target magnet, causing a magnetostrictive response at the position of the target magnet in the waveguide. The magnetostrictive response takes the form of an acoustic wave having a mechanical pulse component that includes a longitudinal wave corresponding to compression of the waveguide along its longitudinal axis and a torsional wave corresponding to torsional strain on the surface of the waveguide with respect to the longitudinal axis.

[0004] The transducer or detection element of a magnetostrictive position measurement system located at the end of the waveguide is used to detect longitudinal or torsional waves by converting the waves into an electrical response signal. The electrical response signal is processed to determine the position of the target magnet based on a propagation time measurement between the excitation signal and the detection of the longitudinal or torsional wave.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] This disclosure provides a dual-coil magnetostrictive sensor waveguide assembly. [Means for solving the problem]

[0007] Embodiments of the present disclosure relate to a magnetostrictive position measurement system utilizing a waveguide assembly having a dual-coil pickup, a magnetostrictive position measurement system including a waveguide assembly, and a method.

[0008] One embodiment of a waveguide assembly includes a waveguide having a longitudinal axis and a magnetostrictive response pickup. The pickup includes a first coil oriented within a first plane substantially parallel to the longitudinal axis, and a second coil connected in series with the first coil and oriented within a second plane substantially parallel to the longitudinal axis. The central axis of the first coil is displaced along the longitudinal axis by a coil separation distance from the central axis of the second coil.

[0009] In one embodiment, the coil isolation distance is approximately half the wavelength of the acoustic pulse magnetostrictive response transmitted through the waveguide.

[0010] In one embodiment, the acoustic pulse includes a torsional wave.

[0011] In one embodiment, the acoustic pulse includes a longitudinal wave.

[0012] In one embodiment, the first and second planes are substantially parallel.

[0013] In one embodiment, each of the first and second coils is a helical coil.

[0014] In one embodiment, the waveguide assembly includes a first coil assembly and a second coil assembly. The first coil assembly comprises a plurality of first stacked coils connected in series with one another. Each first stacked coil is oriented within a plane that is substantially parallel to the longitudinal axis and substantially coaxial with respect to other first stacked coils. Multiple first stacked coils include the first coil, The second coil assembly comprises a plurality of second stacked coils connected in series with one another. Each second stacked coil is oriented within a plane that is nearly parallel to the vertical axis and is nearly coaxial with respect to other second stacked coils. Multiple second stacked coils include a second coil.

[0015] In one embodiment, each of the first and second coils has a diameter of approximately 3 to 10 mm.

[0016] In one embodiment, the first and second coils are located on the same side of the waveguide.

[0017] In one embodiment, the waveguide assembly includes an electromagnetic reflector. The waveguide is placed between the reflector and the first and second coils.

[0018] In one embodiment, the electromagnetic reflector is electrically grounded.

[0019] In one embodiment, the waveguide assembly includes at least one magnetic shielding member. Each magnetic shielding member contains a ferromagnetic material. A plane extending perpendicular to the vertical axis and through one of the first and second coils extends through at least one magnetic shielding member.

[0020] In one embodiment, at least one magnetic shielding member includes a lower magnetic shielding member. The first and second coils are positioned between the lower magnetic shielding member and the waveguide.

[0021] In one embodiment, at least one magnetic shielding member includes an upper magnetic shielding member. The waveguide is positioned between the first and second coils and the upper magnetic shield member.

[0022] In one embodiment, the first and second coils are disposed closer to the proximal end of the waveguide than to the distal end of the waveguide. Each of the upper and lower magnetic shield members includes a proximal end corresponding to the proximal end of the waveguide and a distal end corresponding to the distal end of the waveguide. The position of the distal end of the lower magnetic shield member along the longitudinal axis is offset toward the distal end of the waveguide with respect to the position of the distal end of the upper magnetic shield member along the longitudinal axis.

[0023] An example of a magnetostrictive position measurement system includes a waveguide having a longitudinal axis, an excitation generator configured to generate an excitation signal transmitted through the waveguide, a target magnet, a magnetostrictive response pickup, and a signal conditioner. The target magnet is a target magnet movable along the longitudinal axis with respect to the waveguide and is configured to generate an acoustic pulse transmitted by the waveguide in response to the excitation signal. The magnetostrictive response pickup includes a first coil oriented within a first plane substantially parallel to the longitudinal axis and a second coil connected in series with the first coil and oriented within a second plane substantially parallel to the longitudinal axis. The central axis of the first coil is displaced along the longitudinal axis by a coil separation distance from the central axis of the second coil. The signal conditioner is configured to amplify the signal transmitted through the first and second coils in response to the acoustic pulse and output a conditioned response signal.

[0024] In one embodiment, each of the first and second coils is a helical coil.

[0025] In one embodiment, the coil separation distance is approximately one-half of the wavelength of the acoustic pulse transmitted by the waveguide.

[0026] In one embodiment, the acoustic pulse includes a torsional wave.

[0027] In one embodiment, the acoustic pulse includes a longitudinal wave.

[0028] In one embodiment, the first and second planes are substantially parallel.

[0029] In one embodiment, each of the first and second coils is formed in a layer of the printed circuit board.

[0030] In one embodiment, the system includes a first coil assembly and a second coil assembly. The first coil assembly comprises a plurality of first stacked coils connected in series with one another. Each first stacked coil is oriented within a plane that is substantially parallel to the longitudinal axis and substantially coaxial with respect to other first stacked coils. Multiple first stacked coils include the first coil, The second coil assembly comprises a plurality of second stacked coils connected in series with one another. Each second stacked coil is oriented within a plane that is nearly parallel to the vertical axis and is nearly coaxial with respect to other second stacked coils. Multiple second stacked coils include a second coil.

[0031] In one embodiment, each coil has a diameter of approximately 3 to 10 mm.

[0032] In one embodiment, the first and second coils are located on the same side of the waveguide.

[0033] In one embodiment, the system includes an electromagnetic reflector. Each coil is positioned between the reflector and the waveguide.

[0034] In one embodiment, the electromagnetic reflector is electrically grounded.

[0035] In one embodiment, the system includes at least one magnetic shielding member, each containing a ferromagnetic material. A plane extending perpendicular to the vertical axis and through one of the first and second coils extends through at least one magnetic shielding member.

[0036] In one embodiment, at least one magnetic shielding member includes a lower magnetic shielding member. The first and second coils are positioned between the lower magnetic shielding member and the waveguide.

[0037] In one embodiment, at least one magnetic shielding member includes an upper magnetic shielding member. The waveguide is located between the first and second coils and the upper magnetic shielding member.

[0038] In one embodiment, the first and second coils are positioned closer to the proximal end of the waveguide than to the distal end of the waveguide. Each of the upper and lower magnetic shielding members includes a proximal end corresponding to the proximal end of the waveguide and a distal end corresponding to the distal end of the waveguide. The distal end of the lower magnetic shielding member along the vertical axis is offset toward the distal end of the waveguide with respect to the distal end of the upper magnetic shielding member along the vertical axis.

[0039] In one embodiment, the first and second coils have a predetermined impedance (for example, about 1 to 3 ohms), The signal conditioner is, A first-stage amplifier having an impedance that substantially matches the impedance of a coil, configured to amplify signals transmitted through first and second coils and output a corresponding first-stage signal, It includes a second stage amplifier having high impedance, configured to amplify the first stage signal and output a corresponding second stage signal.

[0040] In one embodiment, the output section of the first-stage amplifier has a predetermined impedance (for example, about 24 to 50 kΩ), The input section of the second-stage amplifier has an impedance that is approximately the same as the impedance of the output section of the first-stage amplifier.

[0041] In one embodiment, the first stage amplifier has a first gain (for example, about 800 to 1200), The second stage amplifier has a second gain (e.g., about 8-12) which is 1 / 100th of the first gain.

[0042] In one embodiment, the signal conditioner is A rectifier circuit configured to rectify the second stage signal, It includes a demodulator configured to demodulate the rectified second-stage signal.

[0043] In one embodiment, the system includes a controller configured to determine the position of a target magnet along a waveguide using a conditioned response signal. One embodiment of this method includes forming a waveguide assembly, Forming a waveguide assembly is To provide a waveguide having a vertical axis, This includes forming a magnetostrictive response pickup. Forming a magnetostrictive response pickup is To form a first coil oriented within a first plane that is approximately parallel to the vertical axis, This includes forming a second coil connected in series with a first coil, which is oriented within a second plane that is substantially parallel to the vertical axis, The central axis of the first coil is displaced along the vertical axis by a distance equal to the coil separation distance from the central axis of the second coil.

[0044] In further embodiments, the coil isolation distance may be about half the wavelength of the acoustic pulse magnetostrictive response transmitted by the waveguide, and / or The first and second planes are approximately parallel, and / or Each of the first and second coils is a helical coil, and / or Each of the first and second coils has a diameter of approximately 3 to 10 mm, and / or The first and second coils are located on the same side of the waveguide.

[0045] If desired, forming the first coil includes forming the first coil using conductor traces on a printed circuit board, and / or Forming a second coil includes forming a second coil using conductor traces on a printed circuit board, and / or Forming a first coil involves forming a first coil assembly comprising a plurality of first stacked coils connected in series with one another. Each first stacked coil is oriented within a plane that is substantially parallel to the longitudinal axis and substantially coaxial with respect to other first stacked coils. Multiple first stacked coils include and / or Forming a second coil involves forming a second coil assembly comprising a plurality of second stacked coils connected in series with one another. Each second stacked coil is oriented within a plane that is nearly parallel to the vertical axis and is nearly coaxial with respect to other second stacked coils. Multiple second stacked coils include a second coil.

[0046] In yet another embodiment, the method may also include forming an electromagnetic reflector. The waveguide is placed between the reflector and the first and second coils. If desired, this method may also include electrically grounding the electromagnetic reflector.

[0047] If desired, this method may also include forming a magnetic shielding member. For example, this method may include forming at least one magnetic shielding member. Each magnetic shielding member contains a ferromagnetic material. A plane extending perpendicular to the vertical axis and through one of the first and second coils extends through at least one magnetic shielding member, Forming at least one magnetic shielding member may include forming a lower magnetic shielding member. The first and second coils are positioned between the lower magnetic shielding member and the waveguide, and / or Forming at least one magnetic shielding member may include forming an upper magnetic shielding member. The waveguide is located between the first and second coils and the upper magnetic shielding member, and / or The first and second coils are positioned closer to the proximal end of the waveguide than to the distal end of the waveguide. Each of the upper and lower magnetic shielding members includes a proximal end corresponding to the proximal end of the waveguide and a distal end corresponding to the distal end of the waveguide. The distal end of the lower magnetic shielding member along the vertical axis is offset toward the distal end of the waveguide with respect to the distal end of the upper magnetic shielding member along the vertical axis.

[0048] This summary is provided in a simplified form to introduce the selection of concepts, which are further described in embodiments for carrying out the inventions described below. This summary is not intended to identify any key or essential features of the subject matter, nor is it intended to be used to help determine the scope of the subject matter. The subject matter described in the claims is not limited to embodiments that solve any or all of the defects described in the background. [Brief explanation of the drawing]

[0049] [Figure 1] This is a schematic diagram of one embodiment of a magnetostrictive position measurement system according to the present disclosure. [Figure 2] This is a simplified circuit diagram of one embodiment of the magnetostrictive position measurement system according to the present disclosure. [Figure 3] This is a simplified top view of one embodiment of a magnetostrictive response pickup according to the present disclosure. [Figure 4] This is a simplified cross-sectional view of one embodiment of a magnetostrictive response pickup according to the present disclosure. [Figure 5] This is a simplified cross-sectional view of an exemplary magnetostrictive response pickup according to an embodiment of the present disclosure. [Figure 6] This is a front isometric view of one embodiment of a coil stack according to the present disclosure. [Figure 7] This is a simplified block diagram of one embodiment of a signal conditioner according to the present disclosure. [Figure 8] This is a circuit diagram of one embodiment of a signal conditioner according to the present disclosure. [Modes for carrying out the invention]

[0050] Embodiments of the present disclosure are described more thoroughly below with reference to the accompanying drawings. Components identified by the same or similar reference numerals indicate the same or similar components. However, various embodiments of the present disclosure may be carried out in numerous different forms and should not be construed as being limited to the specific embodiments described herein. Rather, the embodiments are described in a manner that makes the present disclosure detailed and complete and that fully conveys the scope of the embodiments to those skilled in the art.

[0051] Figures 1 and 2 are schematic and simplified circuit diagrams, respectively, of an embodiment of a magnetostrictive position measurement system 100 according to the present disclosure. The system 100 includes a wire having magnetoelastic properties called a waveguide 102, and one or more target magnets 104 (one of which is shown in Figure 1) arranged adjacent to the waveguide 102 (e.g., a bar magnet) and / or surrounding the waveguide 104 (e.g., a ring magnet).

[0052] Each target magnet 104 is movable relative to the waveguide 102 along the longitudinal axis 106, as indicated by the arrow 107, and has a position 110 along the axis 106 from a reference position 114, which is detected by the system 100. Each target magnet 104 is independently movable along the waveguide 102 and may consist of one or more magnets (e.g., permanent magnets or electromagnets), such as a single magnet or a stack of magnets.

[0053] The controller 120 (Figure 2) of system 100 includes an excitation generator 122. As shown in Figure 1, a closed electrical circuit may be formed by the generator 122, the waveguide 102, and a return wire 124 connecting the distal end 126 of the waveguide 102 to the excitation generator 122. The generator 122 may be in the form of an electrical pulse generator that generates an electrical excitation signal in the form of a current pulse 127. The electrical excitation signal is sent to the proximal end 128 of the waveguide 102. An amplifier 129 (Figure 2) may be used to amplify the electrical pulse 127 before applying it to the waveguide 102.

[0054] The transmission of electrical pulses 127 through waveguide 102 generates a magnetic field 130, which interacts with the magnetic field 132 of magnet 104 to generate a mechanical magnetostrictive response (e.g., sound wave) 134 in waveguide 102. This includes longitudinal waves 134A (e.g., longitudinal compression) and torsional waves 134B (e.g., torsional strain) in waveguide 104, as shown in Figure 1.

[0055] The magnetostrictive response 134 propagates along the waveguide 102 from both sides of the magnet 104. For example, portions of the magnetostrictive response 134 may propagate along the waveguide 102 from the position 110 of the magnet 104 toward the end 126 of the waveguide 102, and possibly to a damper (not shown) that reduces or eliminates back propagation of acoustic waves through the waveguide 102. Furthermore, portions of the magnetostrictive response 134 propagate from the position 110 of the magnet 104 toward the end 128 of the waveguide, where a magnetostrictive response pickup 140 is used to detect the response 134.

[0056] The pickup 140 includes one or more sensing elements 142 configured to detect the magnetostrictive response 134 and generate at least one electrical response signal 143 based on the magnetostrictive response 134. That is, the electrical response signal or signal 143 includes an index for the longitudinal wave 134A and / or an index for the torsional wave 134B. One or more indices may include transient changes or pulses in the magnitude of the signal 143, which may be detected by the controller 120 to determine the position 110 of the target magnet using prior art.

[0057] The signal conditioner 146 of the pickup 140 may be used to amplify (or otherwise condition, e.g., rectify, filter, etc.) the signal 143 before sending the conditioned response signal 148 to the controller 120, as shown in Figure 2. Thus, in some embodiments, the response signal 148 may be the original signal 143 generated by one or more detection elements 142, as in the case where the pickup 140 does not include a signal conditioner 146, or the response signal 148 may be a conditioned or processed form of the signal 143 generated by one or more detection elements 142.

[0058] The controller 120 may process one or more response signals 148 using any suitable technique. In one embodiment, the controller 120 includes an analog-to-digital converter (ADC) 160 that converts each of the one or more analog electrical response signals 148 into a corresponding digital sample 148'. For example, the ADC 160 may sample each of the one or more analog response signals 148 at a predetermined frequency, which allows the response signals 148 to be further processed by the controller 120. The digital sample 148' of each response signal 148 may be stored, for example, in the memory 162 of the system 100 or in a buffer of the controller 120.

[0059] The controller 120 may include a clock generator 164, which initiates a timing routine for when magnetostrictive excitations are generated by the excitation generator 122, for example, when a current pulse 127 is generated. The clock generator 164 may be used to determine the time of each digital sample 148' related to the generation of the magnetostrictive excitation 127. The digital samples 148' may be analyzed to detect the corresponding propagation time of an index of the magnetostrictive response 148, thereby determining the position 110 of the target magnet 104 based on the known velocity of the corresponding longitudinal acoustic wave 134A or torsional acoustic wave 134B through the waveguide 102, according to the prior art. The controller 120 may output a position estimate 165 indicating the position 110.

[0060] The controller 120 may comprise one or more processors 166 that control components of the system 100 and / or perform one or more functions described herein in response to the execution of instructions. Instructions may be stored locally in the system 100's non-temporary memory 162 or in a computer-readable medium (e.g., flash memory, optical data storage device, magnetic data storage device, etc.). In some embodiments, each processor 166 of the controller 120 may comprise, for example, one or more computer-based systems, control circuits, microprocessor-based engine control systems, and / or programmable hardware components (e.g., field-programmable gate arrays).

[0061] In some embodiments, at least one processor 166 is configured to detect indices for longitudinal waves 134A and / or torsional waves 134B by analyzing digital samples 148' of the response signal 148, and to establish propagation times for the indices. In some embodiments, a controller 120 is configured to calculate candidate positions 110 for the target magnet 104 along the axis 106 of the waveguide 102 based on the propagation times of the detected indices.

[0062] Figures 3 and 4 are a simplified top view and a simplified cross-sectional view of an embodiment of a pickup 140 according to the present disclosure, respectively. The pickup includes two or more coils 142, such as coils 142A and 142B. Each of the coils 142 acts as an antenna, where a response signal 143 having the form of a current is generated in response to a magnetostrictive response or acoustic wave 134 propagating in a waveguide 102 passing near the coil 142 due to electromagnetic induction.

[0063] Coils 142A and 142B are connected in series with each other and may have any suitable form. In one embodiment, each coil 142 may have a diameter 170 of about 3 to 10 millimeters and / or may have the form of a spiral coil, such as an Archimedean spiral as shown in Figure 3, or any other suitable form. Coils 142 may take the form of a pancake coil, in which case coils 142A and 142B are located or oriented in planes 172A and 172B that are substantially or approximately parallel (e.g., + / - 10 degrees) to the longitudinal axis 106 of the waveguide 102. In some embodiments, planes 172A and 172B are substantially parallel to each other (e.g., + / - 10 degrees) and they may be aligned such that coils 142A and 142B are formed substantially or approximately on one or more of the same plane. Each coil 142 has a corresponding central axis 174. The central axis 174 may be substantially or approximately perpendicular (e.g., + / - 10 degrees) to the vertical axis 106 of the waveguide 102, or substantially or approximately parallel to each other (e.g., + / - 10 degrees).

[0064] The coil 142 may be configured such that the indices in the current signal 143 generated in the coil 142 in response to the magnetostrictive acoustic wave or pulse 134 interfere with each other in a constructive manner, thereby boosting the amplitude of the indices in the response signal 143. In one embodiment, the central axes 174 are separated from each other by a separation distance 176 equal to about half the wavelength of the acoustic wave 134 targeted by the pickup 140, thereby promoting constructive interference of the current signals 143 generated in the coil 142 while boosting common-mode noise suppression.

[0065] The magnetostrictive longitudinal acoustic wave or pulse 134A may propagate at approximately 1600 m / s through a conventional waveguide 102, for example, and may have a frequency of approximately 150-175 kHz and a wavelength of approximately 11 mm. Therefore, when the longitudinal wave 134B in such a waveguide is targeted by the pickup 140, the separation distance 176 is set to approximately 5-6 mm, thereby causing constructive interference in the indicator of the signal 143 generated in the coil 142 in response to the longitudinal wave 134A in waveguide 102.

[0066] The magnetostrictive torsional acoustic wave or pulse 134B may propagate, for example, through a conventional waveguide 102 at approximately 2800 meters per second (m / s), and may have a frequency of approximately 250-300 kHz and a wavelength of approximately 1.1 cm. Therefore, if such a torsional wave 134B is targeted by the pickup 140, the separation distance 176 between the coils 142 is set to half the wavelength of the torsional wave, and thus approximately 5.5 millimeters (mm).

[0067] Furthermore, coil 142 may be wound in opposite directions, as shown in Figure 3, to promote constructive interference of the current response signals 143 generated in response to the magnetostrictive wave or pulse 134. Therefore, for example, as shown in Figure 3, coil 142A may be wound in a clockwise direction, and coil 142B may be wound in a counterclockwise direction.

[0068] In other embodiments, the pickup 140 may comprise two or more stacks 180 of coils 142, as shown in Figure 5, a simplified cross cross section of a portion of the pickup 140 according to an embodiment of the present disclosure. The exemplary pickup 140 in Figure 5 includes a stack 180A of coils 142A-1, 142A-2, and 142A-3 connected in series, and a stack 180B of coils 142B-1, 142B-2, and 142B-3 connected in series. Figure 6 is a front isometric view of one embodiment of a stack 180 comprising four coils 142-1, 142-2, 142-3, and 142-4 connected in series, according to an embodiment of the present disclosure. Each stack 180 of the multiple coils 142 operates to increase the amplitude of the response signal 143 generated in the coil in response to the passage of magnetostrictive acoustic pulses 134 through the waveguide 102, compared to that generated by a single coil 142.

[0069] Multiple coils 142 in each stack 180 may share a common central axis 174. Furthermore, each coil 142 may be oriented in a corresponding plane, such as planes 172A-1, 172A-2, and 172A-3 for coils 142A-1, 142A-2, and 142A-3, and planes 172B-1, 172B-2, and 172B-3 for coils 142B-1, 142B-2, and 142B-3. All of these are substantially parallel to the longitudinal axis 106 (not shown) of the waveguide 102. Furthermore, as schematically shown in Figure 5, the plane 172A of each coil 142A in stack 180A may be aligned with the plane 172B of the corresponding coil 142B in stack 180B. Therefore, for example, the plane 172A-1 containing coil 142A-1 may be aligned with the plane 172B-1 containing coil 142B-1.

[0070] The coils 142 may be formed using any suitable technique. In one embodiment, the coils 142 are formed by traces on the printed circuit board 182. Thus, each coil 142 may be formed by a conductor trace on a single layer 184 of the printed circuit board 182, as shown in Figure 4. When multiple coils 142 are formed as a stack 180, the coils 142 may be formed by conductor traces on multiple layers 184, such as layers 184A to C, of ​​the printed circuit board 182, as shown in Figure 5. Each of the coils 142 may be connected to coils on the upper and / or lower layers 184 via connections between the layers 184.

[0071] The pickup 140 may also include a function to boost the amplitude of the magnetostrictive pulse 134 index in the response signal 143 to improve the signal-to-noise ratio of the response signal 143. In one embodiment, as shown in Figure 4, the pickup 140 includes an electromagnetic reflector 190, and the waveguide 102 is located between the reflector 190 and the coil 142. The reflector 190 may be formed by a layer or sheet of a suitable conductive material (e.g., copper) covering the waveguide 102.

[0072] The reflective layer 190 generally operates to reflect electromagnetic energy corresponding to the magnetostrictive response 134, which propagates radially and outward from the waveguide 102 toward the coil 142. This boosts the magnitude of the electromagnetic energy in the coil 142, and therefore the magnitude of the current signal 143 generated in the coil 142 in response to the electromagnetic energy.

[0073] In one embodiment, the pickup 140 includes one or more electromagnetic interference (EMI) shields 192 provided outside the waveguide 102 and / or coil 142. The one or more EMI shields 192 operate to reduce interference from electromagnetic signals from sources outside the waveguide 102, thereby improving the signal-to-noise ratio of the response signal 143. Each EMI shield 192 generally comprises a layer 194 of conductive material connected to an electrical ground 196.

[0074] For example, the pickup may include an upper EMI shield 192A located outside the waveguide 102 and / or a lower EMI shield 192B located outside the coil 142, such that the waveguide 102 and coil 142 are positioned between the shields 192A and 192B, as shown in Figure 4. The pickup 142 may also include a side EMI shield that extends along the waveguide 102 and coil 142 to fill the gap between the EMI shields 192A and 192B. The shields 192A and 192B may be portions of a single shield 192 that generally extends around the waveguide 102 and coil 142. In one embodiment, a reflector 190 is connected to an electrical ground 196 to form an EMI shield, possibly replacing the upper EMI shield 192A.

[0075] In some embodiments, the pickup 140 includes a magnetic shield 198 located near the coil 142. The magnetic shield 198 helps reduce the potential influence that the magnetic field 132 of the target magnet 104 may have on the response signal 143 as it approaches the coil 142. This reduces the "null region" of the system 100, which is the area near the coil 142 where the position 110 of the target magnet 104 becomes undeterminable due to magnetic interference. Thus, the magnetic shield 198 extends the operating range of the target magnet 104 along the waveguide 102 by reducing the null region in the coil 142 to, for example, about 1 inch.

[0076] The magnetic shield 198 may take various forms. In one embodiment, the magnetic shield 198 includes an upper magnetic shielding member 200A and / or a lower magnetic shielding member 200B. Each of the magnetic shielding members 200 may be formed from iron, low-carbon steel, nickel-iron ferromagnetic alloy (a suitable ferromagnetic material such as mu-metal, for example), or another suitable ferromagnetic material.

[0077] Each magnetic shielding member 200 extends over at least one of the coils 142. In the embodiment shown in Figure 4, each of the magnetic shielding members 200 (solid lines) covers coil 142B from above or below, but the magnetic shielding members 200 may extend toward the end 128 of the waveguide 102 so as to cover both coils 142A and 142B from above or below, as shown in the line of sight. As a result, a plane extending perpendicular to the longitudinal axis 106 of the waveguide 102, such as one aligned with the central axis 174 of coil 142B, may extend through each of the at least one magnetic shielding member 200 and at least one coil 142 (e.g., coil 142B).

[0078] The upper and lower magnetic shielding members 200A and 200B each have a proximal end 202 corresponding to end 128 of the waveguide 102 and a distal end 204 corresponding to end 126 of the waveguide 102. The proximal end 202 and distal end 204 of each magnetic shielding member 200 may be aligned with each other. In one embodiment, as shown in Figure 4, the distal end 204 of the lower magnetic shielding member 200B is offset by a predetermined distance 206, for example 1 to 5 mm, along the vertical axis 106 toward the distal end 126 of the waveguide 102, with respect to the distal end 204 of the upper magnetic shielding member 200A. This configuration can provide additional shielding against magnetic interference on the bottom side of the coil 142 while reducing the null region of the system 100, such as when the target magnet 104 (e.g., a bar magnet) is located above the upper magnetic shield 202A.

[0079] In some embodiments, the coil 142 is a low-impedance coil with an impedance of about 1 ohm or less that generates a signal 143 that may be too weak (e.g., about 40-60 microvolts) to be processed by the controller 120. As a result, in some embodiments, the pickup 140 includes a signal conditioner 146 that operates to amplify the signal 143 to generate a corresponding conditioned response signal 148. The conditioned response signal 148 may be used by the controller 120 to determine the position 110 of the magnet 104 by detecting an index of the magnetostrictive response 134 detected by the coil 142.

[0080] Figure 7 is a simplified block diagram of one embodiment of a signal conditioner 146 according to the present disclosure. In some embodiments, the signal conditioner 146 includes a low-impedance first-stage amplifier 210 that receives a signal 143 from a coil 142 and amplifies the signal 143 to produce an amplified signal 148A. The input impedance of the first-stage amplifier 210 is generally matched to the low output impedance of the coil 142 (e.g., about 1 ohm) for efficient energy transfer. The first-stage amplifier 210 may have a gain of about 800 to 1200, such as about 1000 (e.g., + / -100).

[0081] In some embodiments, the signal conditioner 146 includes a second-stage amplifier 212 having a relatively high input impedance to match the relatively high output impedance (e.g., about 24–50 kΩ) of the first-stage amplifier 210. The second-stage amplifier 212 receives a signal 148A from the first-stage amplifier 210 and amplifies the signal 148A to produce an amplified signal 148B. The second-stage amplifier 212 may have a gain of about 8–12, such as about 10 (e.g., + / -2).

[0082] The signal conditioner 146 may also include a rectifier circuit 214 that operates to generate a rectified signal 148C by rectifying the oscillation signal 148B received from the second-stage amplifier 212. The rectifier circuit 214 may provide passive rectification using a suitable diode bridge, active rectification using bipolar transistors, or other suitable circuitry.

[0083] A demodulation circuit 216 may be used to generate a demodulated signal 148D by demodulating the signal 148C. Here, an index of the magnetostrictive response 134 is clarified for detection by the controller 120. In some embodiments, the demodulation circuit 216 may be equipped with a suitable low-pass filter.

[0084] The controller 120 may detect an indicator and determine the position 110 (Figure 1) of the target magnet 104 along the vertical axis 106 of the waveguide 102 by processing a conditioned response signal 148 received from the signal conditioner 146.

[0085] Figure 8 is a circuit diagram of one embodiment of the signal conditioner 146 according to the present disclosure. Those skilled in the art will understand that the exemplary circuit of the signal controller 146 may take other forms different from those shown in Figure 8, while performing similar functions.

[0086] In the exemplary circuit of the signal controller 146, coils 142A and 142B are represented by inductors 220A and 220B connected in series. Capacitors 222 and resistors 224 operate to increase the intrinsic inductance, capacitance, and resistance of coils 142A and 142B, thereby producing a bandpass transfer function with upper and lower cutoff frequencies tuned to the target frequency of the index in the response signal 143. For example, capacitor 222 (e.g., about 0.27 microfarads) and resistor 224 (about 3.9 ohms) may produce a bandpass transfer function with a lower cutoff at about 50 kHz and an upper cutoff at about 600 kHz, along with a rolloff of -40 dB / decade on both sides.

[0087] An exemplary first-stage amplifier 210 generally includes a current-mode amplifier formed by a transistor 226 (e.g., a PNP bipolar junction transistor), an inductor 228, and a resistor 230 (e.g., about 0 to 10 ohms). The emitter of the bipolar junction transistor 226 is biased with a supply voltage Vs (e.g., about 9VDC), and the base is biased by a voltage across the resistor 230 from a current signal 143 generated by an inductor 142. The larger the amplitude of the current signal 143, the larger the amplitude of the current signal 148A sent through the transistor 226.

[0088] Inductor 228 is provided in parallel with resistor 232 (e.g., about 24 kΩ) between the collector of transistor 226 and electrical common or ground 234. The inductance of inductor 228 is generally matched to the inductance of coil 142.

[0089] Capacitor 236 (e.g., about 0.1 microfarads) and resistor 238 (e.g., about 825 ohms) may be used to apply a forward bias to the base and emitter of transistor 226 in response to signal 143, thereby allowing current to flow through transistor 226.

[0090] Resistors 235 (e.g., approximately 240 ohms) and 237 (e.g., approximately 470 ohms), and capacitor 239 (e.g., approximately 0.22 μFarads) operate to set the gain in the second-stage amplifier 212.

[0091] The gain of the first-stage amplifier 210 may be around 800 to 1200, such as about 1000 (e.g., + / -100), which basically corresponds to the ratio of the inductance of inductor 228 to the inductance of coil 142. The output signal 148A from the first-stage amplifier 210 may have a voltage of about 40 to 60mV, such as 50mV.

[0092] An exemplary second-stage amplifier 212 includes a pair of field-effect transistors (FETs) 240 and 242 having a cascode transistor configuration, which is useful for minimizing regenerative feedback energy and preventing uncontrollable oscillation of the amplified signal. FET 240 may have a high impedance (e.g., about 1 gigaohm) and is connected to a voltage across inductor 228. When FET 240 conducts, FET 242 is driven to conduct, thereby causing a current signal 148B to flow through the resistor 244 and transformer 246 of the second-stage amplifier, providing a gain of about 8-12, such as about 10 (e.g., + / -1). The current signal 148B may have a voltage of, for example, about 500mV. An indicator of the magnetostrictive response in signal 148B has a sinusoidal oscillation pattern that appears as pulses.

[0093] The rectifier circuit 214 may take any suitable form and is connected to the output signal 148B of the second-stage amplifier via the transformer 246. In the exemplary rectifier circuit 214 shown in Figure 8, the oscillation signal 148B output from the transformer 246 is rectified by an active rectifier configuration formed by Schottky diodes 248 and 250, transistors 252 and 254, resistor 256 (e.g., about 100 kΩ), and capacitors 258 (e.g., about 0.1 microfarads) and 260 (e.g., about 33 microfarads) to form the output signal 148C.

[0094] The output signal 148C from the rectifier circuit 214 is sent through the low-pass filter 262 of the demodulation circuit 216, which is formed by a capacitor 264 (e.g., 180 picofarads), a resistor 266 (e.g., 11k ohms), and a diode 268, and which can block frequencies higher than, for example, about 100kHz. The filtered output signal 148D may have a voltage of about 4V.

[0095] The controller 120 processes the filtered output signal 148D to detect, using prior art, pulses that form an index of the magnetostrictive response 134 and the position 110 of the target magnet 104. In some embodiments, the index pulse in signal 148D is processed as a carrier wave, and the envelope of the pulse is detected by the controller 120 and used to determine the position 110 of the target magnet 104 using processing described in Patent Document 1, which is incorporated herein by reference.

[0096] An additional embodiment relates to a method for detecting the position 110 of a target magnet using the coil 142 described above.

[0097] While embodiments of this disclosure have been described with reference to preferred embodiments, those skilled in the art will recognize that the form and details may be modified without departing from the spirit and scope of this disclosure.

[0098] The functions described herein may be performed by a single controller or processor, multiple controllers or processors, or at least one controller or processor. Where, as used herein, one or more functions are described as being performed by one controller (e.g., a specific controller), one or more controllers, at least one controller, one processor (e.g., a specific processor), one or more processors, or at least one processor, embodiments include the execution of one or more functions by a single controller or processor or by multiple controllers or processors, unless otherwise specified herein. Furthermore, where, as used herein, multiple functions are performed by at least one controller or processor, all of the functions may be performed by a single controller or processor, or some functions may be performed by one controller or one processor, and other functions may be performed by another controller or processor. Thus, the execution of one or more functions by at least one controller or processor does not require that all of the functions be performed by each of the multiple controllers or multiple processors.

Claims

1. A waveguide assembly for a magnetostrictive position measurement system, The above waveguide assembly comprises a waveguide having a vertical axis and a magnetostrictive response pickup, The above magnetostrictive response pickup is A first coil oriented within a first plane that is substantially parallel to the vertical axis mentioned above, The first coil is connected in series with the second coil, and the second coil is oriented within a second plane that is substantially parallel to the vertical axis. The central axis of the first coil is displaced along the vertical axis by a distance equal to the coil separation distance from the central axis of the second coil. Waveguide assembly.

2. The above coil isolation distance is approximately half the wavelength of the acoustic pulse magnetostrictive response transmitted through the waveguide. Waveguide assembly according to claim 1.

3. Acoustic pulses include torsional waves or longitudinal waves. Waveguide assembly according to claim 1 or 2.

4. The first and second planes described above are approximately parallel. Waveguide assembly according to any one of claims 1 to 3.

5. Each of the first and second coils described above is a helical coil. Waveguide assembly according to any one of claims 1 to 4.

6. The waveguide assembly further comprises a first coil assembly and a second coil assembly, The first coil assembly described above comprises a plurality of first stacked coils connected in series with each other, Each first stacked coil is oriented within a plane substantially parallel to the vertical axis and substantially coaxial with respect to other first stacked coils. The above-mentioned plurality of first stacked coils include the above-mentioned first coil, The second coil assembly described above comprises a plurality of second stacked coils connected in series with each other. Each second stacked coil is oriented within a plane substantially parallel to the vertical axis and substantially coaxial with respect to other second stacked coils. The above-mentioned plurality of second stacked coils include the above-mentioned second coils, Waveguide assembly according to any one of claims 1 to 5.

7. Each of the first and second coils has a diameter of approximately 3 to 10 mm, and the first and second coils are located on the same side of the waveguide. Waveguide assembly according to any one of claims 1 to 6.

8. The system further comprises an electromagnetic reflector that is electrically grounded and positioned between the reflector and the first and second coils. Waveguide assembly according to any one of claims 1 to 7.

9. The waveguide assembly further includes at least one magnetic shielding member, Each magnetic shielding member contains a ferromagnetic material. A plane extending perpendicular to the vertical axis and through one of the first and second coils extends through at least one magnetic shielding member. In further embodiments, The above-mentioned at least one magnetic shielding member includes a lower magnetic shielding member, The first and second coils described above are arranged between the lower magnetic shielding member and the waveguide. In further embodiments, The above-mentioned at least one magnetic shielding member includes an upper magnetic shielding member, The waveguide is located between the first and second coils and the upper magnetic shielding member. In further embodiments, The first and second coils described above are positioned closer to the proximal end of the waveguide than to the distal end of the waveguide. Each of the above-mentioned upper and lower magnetic shielding members includes a proximal end corresponding to the proximal end of the waveguide and a distal end corresponding to the distal end of the waveguide. The position of the distal end of the lower magnetic shielding member along the vertical axis is offset toward the distal end of the waveguide with respect to the position of the distal end of the upper magnetic shielding member along the vertical axis. Waveguide assembly according to any one of claims 1 to 8.

10. A waveguide having a vertical axis, An excitation generator configured to generate an excitation signal transmitted via the waveguide described above, A target magnet that is movable along the vertical axis with respect to the waveguide, and is configured to generate acoustic pulses transmitted through the waveguide in response to the excitation signal, Magnetostrictive response pickup and Equipped with a signal conditioner, The above magnetostrictive response pickup is A first coil oriented within a first plane that is substantially parallel to the vertical axis mentioned above, The first coil is connected in series with the second coil, and the second coil is oriented within a second plane that is substantially parallel to the vertical axis. The central axis of the first coil is displaced along the vertical axis by a distance equal to the coil separation distance from the central axis of the second coil. The above-mentioned signal conditioner is configured to amplify the signal transmitted through the first and second coils in response to the acoustic pulse and to output a conditioned response signal. Magnetostrictive position measurement system.

11. The first and second coils described above have a predetermined impedance, The above signal conditioner is, A first-stage amplifier having an impedance that substantially matches the impedance of a coil, configured to amplify signals transmitted through the first and second coils and output a corresponding first-stage signal, The system comprises a second stage amplifier having high impedance, configured to amplify the first stage signal and output a corresponding second stage signal, In further embodiments, The output section of the first stage amplifier described above has a predetermined impedance. The input section of the second-stage amplifier has an impedance that is approximately the same as the impedance of the output section of the first-stage amplifier. In further embodiments, The above-mentioned first-stage amplifier has a first gain, The above-mentioned second-stage amplifier has a second gain that is 1 / 100th of the first gain. The system according to claim 10.

12. The above signal conditioner is, A rectifier circuit configured to rectify the above second stage signal, The system further comprises a demodulator configured to demodulate the rectified second-stage signal described above. The system according to claim 11.

13. The system further includes a controller configured to determine the position of the target magnet along the waveguide using the above-described conditioned response signal. The system according to any one of claims 10 to 12.

14. A method comprising forming a waveguide assembly for a magnetostrictive position measurement system, wherein the method is To provide a waveguide having a vertical axis, This includes forming a magnetostrictive response pickup, Forming the above magnetostrictive response pickup means To form a first coil oriented within a first plane that is substantially parallel to the vertical axis, This includes forming a second coil connected in series with the first coil described above, which is oriented within a second plane that is substantially parallel to the vertical axis, The central axis of the first coil is displaced along the vertical axis by a distance equal to the coil separation distance from the central axis of the second coil. method.

15. The above coil isolation distance is approximately half the wavelength of the acoustic pulse magnetostrictive response transmitted by the above waveguide. The first and second planes described above are approximately parallel. Each of the first and second coils described above is a helical coil, Each of the first and second coils described above has a diameter of approximately 3 to 10 mm. Each of the first and second coils described above is located on the same side of the waveguide. Forming the first coil as described above includes forming the first coil using conductor traces on a printed circuit board. Forming the second coil as described above includes forming the second coil using the conductor traces on the printed circuit board, Forming the first coil described above involves forming a first coil assembly comprising a plurality of first stacked coils connected in series with each other. Each first stacked coil is oriented within a plane substantially parallel to the vertical axis and substantially coaxial with respect to other first stacked coils. The above-mentioned plurality of first stacked coils include the above-mentioned first coil, Forming the second coil includes forming a second coil assembly comprising a plurality of second stacked coils connected in series with each other. Each second stacked coil is oriented within a plane substantially parallel to the vertical axis and substantially coaxial with respect to other second stacked coils. The above-mentioned plurality of second stacked coils include the above-mentioned second coil, The above method includes forming an electromagnetic reflector, The waveguide described above is placed between the reflector and the first and second coils. The above method includes electrically grounding the electromagnetic reflector. The above method includes forming at least one magnetic shielding member, Each magnetic shielding member contains a ferromagnetic material. A plane extending perpendicular to the vertical axis and through one of the first and second coils extends through at least one magnetic shielding member. Forming the above-mentioned at least one magnetic shielding member includes forming the lower magnetic shielding member, The first and second coils described above are arranged between the lower magnetic shielding member and the waveguide. Forming the above-mentioned at least one magnetic shielding member includes forming the upper magnetic shielding member, The waveguide is located between the first and second coils and the upper magnetic shielding member. The first and second coils described above are positioned closer to the proximal end of the waveguide than to the distal end of the waveguide. Each of the above-mentioned upper and lower magnetic shielding members includes a proximal end corresponding to the proximal end of the waveguide and a distal end corresponding to the distal end of the waveguide, and / or The position of the distal end of the lower magnetic shielding member along the vertical axis is offset toward the distal end of the waveguide with respect to the position of the distal end of the upper magnetic shielding member along the vertical axis. The method according to claim 14.

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