Ratio metric position sensor and control system

Abstract

The invention relates to a position sensor system comprising: a sensor housing defining a first cavity having a first face; a fluid effector includes: an actuator housing having an inner surface defining a second cavity; and a movable body having a second face and configured for reciprocating movement within the second cavity; an acoustic transmitter system configured to transmit a first transmit acoustic waveform to the first face and a second transmit acoustic waveform to the second face; and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first face based on the first transmitted acoustic waveform and a second reflected acoustic waveform based on a second reflection of the second face based on the second transmitted acoustic waveform.

Description

Priority declaration

[0001] This application claims priority to U.S. Patent Application No. 17 / 656,596, filed on March 25, 2022, which is a continuation-in-part of U.S. Patent Application No. 16 / 987,828, filed on August 7, 2020, and claims the benefit of priority, the contents of which are incorporated herein by reference. Technical Field

[0002] This present specification relates to ultrasonic position sensors. Background Art

[0003] Position measurement devices are used in the characterization and operation of fluid control systems. Traditionally, effector (e.g., valve body, piston head) position tracking is accomplished through the use of a linear variable differential transformer (LVDT). LVDTs drive system sizing and introduce accuracy and sizing constraints. Specifically, the actuator generally requires the LVDT to be mounted via the piston rod, which drives the actuator sizing.

[0004] Ultrasonic position sensors are a proven industrial technology that can be used for position detection. Existing time-of-flight ultrasonic position sensors transmit an acoustic sound pulse (ping) and measure the amount of time before the reflected echo of the sound pulse returns. The amount of time between the transmission and return of the sound pulse depends on the distance between the transceiver and the object being measured, as well as the speed of sound in the medium through which the sound pulse is transmitted. The speed of sound depends on the characteristics of the medium, such as its density, temperature and / or acoustic impedance. Existing time-of-flight ultrasonic position sensors rely on predetermined knowledge or determination of the speed of sound through the medium through which the sound pulse is transmitted in order to function. In applications such as fuel valves and pressure regulators, the temperature and type of fuel used may vary, which can cause the speed of sound to change dynamically during operation. The speed of sound of the medium can be sensed, but the inclusion of these additional sensors increases the complexity, size, cost and weight of such a system. Summary of the invention

[0005] Generally speaking, this document describes ultrasonic position sensors.

[0006] In a first example, a position sensor system includes: a sensor housing defining a first cavity having a first surface; a fluid effector including: an actuator housing having an inner surface defining a second cavity; and a movable body having a second surface and configured to reciprocate within the second cavity; an acoustic transmitter system configured to transmit a first transmitted acoustic waveform to the first surface and to transmit a second transmitted acoustic waveform to the second surface; and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first transmitted acoustic waveform by the first surface, and to detect a second reflected acoustic waveform based on a second reflection of the second transmitted acoustic waveform by the second surface.

[0007] In a second example, according to Example 1, the position sensor system further includes a timer configured to determine a first time of flight of the first transmitted acoustic waveform and the first reflected acoustic waveform, and to determine a second time of flight of the second transmitted acoustic waveform and the second reflected acoustic waveform.

[0008] In a third example, according to Example 2, the position sensor system further includes a processor system configured to determine a position of the movable body within the second cavity based on the first time of flight and the second time of flight.

[0009] In a fourth example, according to any one of Examples 1 to 3, the acoustic transmitter system is configured to transmit one or both of a first transmitted acoustic waveform and a second transmitted acoustic waveform through a fluid in one or both of the first cavity and the second cavity, and the acoustic receiver system is configured to receive one or both of a first reflected acoustic waveform and a second reflected acoustic waveform from the fluid in one or both of the first cavity and the second cavity.

[0010] In a fifth example, according to any of Examples 1 to 4, the acoustic transmitter system is configured to transmit the second transmitted acoustic waveform at a predetermined transmit frequency, and the acoustic receiver system is configured to determine a reflection frequency of the second reflected acoustic waveform.

[0011] In a sixth example, according to Example 5, the position sensor system further includes a processor system configured to determine a velocity of the movable body based on the predetermined transmission frequency and the reflection frequency.

[0012] In a seventh example, according to any one of Examples 1 to 5, the fluid effector is a linear piston effector, the first cavity is a first tubular cavity having a first longitudinal end and a second longitudinal end opposite to the first longitudinal end, the second cavity is a second tubular cavity having a third longitudinal end and a fourth longitudinal end opposite to the third longitudinal end, the movable body is a piston head configured for longitudinal movement in the second tubular cavity, the acoustic transmitter system includes a first acoustic transmitter arranged at the first longitudinal end and a second acoustic transmitter arranged at the third longitudinal end, and the acoustic receiver system includes a first acoustic receiver arranged at the first longitudinal end and a second acoustic receiver arranged at the third longitudinal end.

[0013] In an eighth example, according to any of Examples 1 to 7, the position sensor system further includes a unified cavity including the first cavity and the second cavity.

[0014] In a ninth example, according to Example 8, the first face is at least partially defined by a shoulder extending between the first cavity and the second cavity.

[0015] In a tenth example, according to any one of Examples 1 to 9, the acoustic transmitter system includes: a first acoustic transmitter, wherein the first acoustic transmitter is configured to transmit a first transmitted acoustic waveform to a first surface; and a second acoustic transmitter, wherein the second acoustic transmitter is configured to transmit a second transmitted acoustic waveform to a second surface.

[0016] In an eleventh example, according to Example 10, the second acoustic transmitter at least partially concentrically surrounds the first acoustic transmitter.

[0017] In a twelfth example, according to any one of Examples 1 to 11, the position sensor system also includes a phase detector, which is configured to determine the difference between at least one of: (1) a first transmission phase of a first transmitted acoustic waveform and a first reflection phase of a first reflected acoustic waveform, and (2) a second transmission phase of a second transmitted acoustic waveform and a second reflection phase of a second reflected acoustic waveform.

[0018] In a thirteenth example, according to any one of Examples 1 to 12, the position sensor system also includes another movable body, the movable body having a third surface and configured to reciprocate in a third cavity, wherein the acoustic transmitter system is configured to transmit a third transmitted acoustic waveform to the third surface, and the acoustic receiver system is configured to detect a third reflected acoustic waveform based on a third reflection of the third surface based on the third transmitted acoustic waveform.

[0019] In a fourteenth example, a position sensing method includes: transmitting a first transmitted acoustic waveform to a first acoustic interface through a fluid having a first acoustic impedance; transmitting a second transmitted acoustic waveform to a second acoustic interface through the fluid; reflecting a first reflected acoustic waveform based on the first transmitted acoustic waveform by the first acoustic interface; reflecting a second reflected acoustic waveform based on the second transmitted acoustic waveform by the second acoustic interface; and determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

[0020] In a fifteenth example, according to Example 14, the method also includes: determining a first flight time based on a first transmitted acoustic waveform and a first reflected acoustic waveform; and determining a second flight time based on a second transmitted acoustic waveform and a second reflected acoustic waveform; wherein determining the first position of the second acoustic interface is also based on the first flight time and the second flight time.

[0021] In a sixteenth example, according to Example 15, the first position of the second acoustic interface determined based on the first flight time (t1) and the second flight time (t2) is given by the following equation: (t1-t2) / (t1+t2).

[0022] In a seventeenth example, according to any one of Examples 14 to 16, the method further includes: determining a second position of the second acoustic interface; and determining a velocity of the second acoustic interface based on the first position and the second position.

[0023] In an eighteenth example, according to any one of Examples 14 to 17, the method further includes: determining a reflected acoustic frequency based on one or both of the first reflected acoustic waveform and the second reflected acoustic waveform; and determining a velocity of the second acoustic interface based on the determined reflected acoustic frequency and a predetermined transmitted acoustic frequency of the second transmitted acoustic waveform.

[0024] In a nineteenth example, according to any one of Examples 14 to 18, the first acoustic interface is defined by a first surface of a fluid cavity having a second acoustic impedance different from the first acoustic impedance; the second acoustic interface is defined by a second surface of a movable body within a fluid effector and having a third acoustic impedance different from the first acoustic impedance; a first emitted acoustic waveform is emitted through the fluid toward the first surface; a second emitted acoustic waveform is emitted through the fluid toward the second surface; a first reflected acoustic waveform is based on a first reflection of the first emitted acoustic waveform by the first surface; and a second reflected acoustic waveform is based on a second reflection of the second emitted acoustic waveform by the second surface.

[0025] In a twentieth example, according to any one of Examples 14 to 19, the method further includes determining a phase difference between a second transmitted phase of a second transmitted acoustic waveform and a second reflected phase of a second reflected acoustic waveform, wherein determining the first position of the second acoustic interface is also based on the determined phase difference.

[0026] In a twenty-first example, according to any one of Examples 14 to 20, a first emitted acoustic waveform is emitted through a first fluid cavity toward a surface of the first fluid cavity defining a first acoustic interface, and a second emitted acoustic waveform is emitted through a second fluid cavity toward a second surface of the movable member defining a second acoustic interface.

[0027] In a twenty-second example, according to any one of Examples 14 to 21, a first emitted acoustic waveform is emitted through a first portion of the fluid cavity toward a surface of the fluid cavity defining a first acoustic interface, and a second emitted acoustic waveform is emitted through a second portion of the fluid cavity toward a second surface of the movable member defining a second acoustic interface.

[0028] In a twenty-third example, according to any one of Examples 14 to 22, the method also includes: emitting a third transmitted acoustic waveform to a third acoustic interface through the fluid; reflecting a third reflected acoustic waveform by the third acoustic interface based on the third transmitted acoustic waveform; and determining a second position of the third acoustic interface based on the first reflected acoustic waveform and the third reflected acoustic waveform.

[0029] In a twenty-fourth example, a non-transitory computer storage medium is encoded with a computer program, which includes instructions, which when executed by a data processing device, cause the data processing device to perform operations including: transmitting a first transmitted acoustic waveform to a first acoustic interface through a fluid having a first acoustic impedance; transmitting a second transmitted acoustic waveform to a second acoustic interface through the fluid; reflecting a first reflected acoustic waveform by the first acoustic interface based on the first transmitted acoustic waveform; reflecting a second reflected acoustic waveform by the second acoustic interface based on the second transmitted acoustic waveform; and determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

[0030] In a general example, a position sensor system includes a sensor housing defining a first cavity having a first surface, a fluid effector including an actuator housing having an inner surface defining a second cavity, and a movable body having a second surface and configured for reciprocating movement within the second cavity, an acoustic transmitter system configured to transmit a first transmitted acoustic waveform to the first surface and to transmit a second transmitted acoustic waveform to the second surface, and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first transmitted acoustic waveform by the first surface and to detect a second reflected acoustic waveform based on a second reflection of the second transmitted acoustic waveform by the second surface.

[0031] Various embodiments may include some, all, or none of the following features. The position sensor system may include a timer configured to determine a first flight time of the first transmitted acoustic waveform and the first reflected acoustic waveform, and to determine a second flight time of the second transmitted acoustic waveform and the second reflected acoustic waveform. The position sensor system may include a processor system configured to determine the position of the movable body within the second cavity based on the first flight time and the second flight time. The acoustic transmitter system may be configured to transmit one or both of the first transmitted acoustic waveform and the second transmitted acoustic waveform through a fluid in one or both of the first cavity and the second cavity, and the acoustic receiver system may be configured to receive one or both of the first reflected acoustic waveform and the second reflected acoustic waveform from the fluid in one or both of the first cavity and the second cavity. The acoustic transmitter system may be configured to transmit the second transmitted acoustic waveform at a predetermined transmission frequency, and the acoustic receiver system may be configured to determine the reflection frequency of the second reflected acoustic waveform. The position sensor system may include a processor system configured to determine the velocity of the movable body based on the predetermined transmission frequency and the reflection frequency. The fluid effector may be a linear piston effector, the first cavity may be a first tubular cavity having a first longitudinal end and a second longitudinal end opposite to the first longitudinal end defining a first face, the second cavity may be a second tubular cavity having a third longitudinal end and a fourth longitudinal end opposite to the third longitudinal end, the movable body may be a piston head configured to move longitudinally in the second tubular cavity, the acoustic transmitter system may include a first acoustic transmitter arranged at the first longitudinal end and a second acoustic transmitter arranged at the third longitudinal end, and the acoustic receiver system may include a first acoustic receiver arranged at the first longitudinal end and a second acoustic receiver arranged at the third longitudinal end. The position sensor system may include a unified cavity having a first cavity and a second cavity. The first face may be at least partially defined by a shoulder extending between the first cavity and the second cavity. The acoustic transmitter system may include a first acoustic transmitter configured to emit a first emission acoustic waveform to the first face, and a second acoustic transmitter configured to emit a second emission acoustic waveform to the second face. The second acoustic transmitter at least partially concentrically surrounds the first acoustic transmitter. The position sensor system may include a phase detector configured to determine a difference between at least one of: (1) a first transmit phase of a first transmitted acoustic waveform and a first reflection phase of a first reflected acoustic waveform, and (2) a second transmit phase of a second transmitted acoustic waveform and a second reflection phase of a second reflected acoustic waveform.The position sensor system may include another movable body having a third surface and configured to reciprocate within a third cavity, wherein the acoustic transmitter system is configured to transmit a third transmitted acoustic waveform to the third surface, and the acoustic receiver system is configured to detect a third reflected acoustic waveform based on a third reflection of the third surface based on the third transmitted acoustic waveform.

[0032] In another general example, a position sensing method includes transmitting a first transmitted acoustic waveform to a first acoustic interface through a fluid having a first acoustic impedance, transmitting a second transmitted acoustic waveform to a second acoustic interface through the fluid, reflecting a first reflected acoustic waveform by the first acoustic interface based on the first transmitted acoustic waveform, reflecting a second reflected acoustic waveform by the second acoustic interface based on the second transmitted acoustic waveform, and determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

[0033] Various implementations may include some, all, or none of the following features. The method may include determining a first flight time based on a first transmitted acoustic waveform and a first reflected acoustic waveform, and determining a second flight time based on a second transmitted acoustic waveform and a second reflected acoustic waveform, wherein determining a first position of a second acoustic interface is also based on the first flight time and the second flight time. Determining the first position of the second acoustic interface based on the first flight time (t1) and the second flight time (t2) may be given by the following equation: (t1-t2) / (t1+t2). The method may include determining a second position of the second acoustic interface, and determining a velocity of the second acoustic interface based on the first position and the second position. The method may include determining a reflected acoustic frequency based on one or both of the first reflected acoustic waveform and the second reflected acoustic waveform, and determining the velocity of the second acoustic interface based on the determined reflected acoustic frequency and a predetermined transmitted acoustic frequency of the second transmitted acoustic waveform. The first acoustic interface can be defined by a first face of a fluid cavity having a second acoustic impedance different from the first acoustic impedance, the second acoustic interface can be defined by a second face of a movable body within a fluid effector and having a third acoustic impedance different from the first acoustic impedance, a first transmitted acoustic waveform can be transmitted through the fluid toward the first face, a second transmitted acoustic waveform can be transmitted through the fluid toward the second face, a first reflected acoustic waveform can be based on a first reflection of the first transmitted acoustic waveform by the first face, and a second reflected acoustic waveform can be based on a second reflection of the second transmitted acoustic waveform by the second face. The method can include determining a phase difference between a second transmitted phase of the second transmitted acoustic waveform and a second reflected phase of the second reflected acoustic waveform, wherein determining the first position of the second acoustic interface can also be based on the determined phase difference. The first transmitted acoustic waveform can be transmitted through the first fluid cavity toward a face of the first fluid cavity defining the first acoustic interface, and the second transmitted acoustic waveform can be transmitted through the second fluid cavity toward a second face of the movable member defining the second acoustic interface. The first transmitted acoustic waveform may be transmitted through the first portion of the fluid cavity toward a face of the fluid cavity defining a first acoustic interface, and the second transmitted acoustic waveform may be transmitted through the second portion of the fluid cavity toward a second face of the movable member defining a second acoustic interface. The method may include transmitting a third transmitted acoustic waveform through the fluid toward a third acoustic interface, reflecting a third reflected acoustic waveform by the third acoustic interface based on the third transmitted acoustic waveform, and determining a second position of the third acoustic interface based on the first reflected acoustic waveform and the third reflected acoustic waveform.

[0034] In another general example, a non-transitory computer storage medium is encoded with a computer program having instructions that, when executed by a data processing device, cause the data processing device to perform operations, including transmitting a first transmitted acoustic waveform to a first acoustic interface through a fluid having a first acoustic impedance, transmitting a second transmitted acoustic waveform to a second acoustic interface through the fluid, reflecting a first reflected acoustic waveform by the first acoustic interface based on the first transmitted acoustic waveform, reflecting a second reflected acoustic waveform by the second acoustic interface based on the second transmitted acoustic waveform, and determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

[0035] The systems and techniques described herein can provide one or more of the following advantages. First, the system can determine the position and / or velocity of a target object through an acoustic transmission medium. Second, the system can operate without determining the acoustic properties of the transmission medium. Third, the system can have a more efficient and / or more economical mechanical design compared to existing mechanical position measurement solutions such as variable differential transformers (VDTs). Fourth, the system can have a more efficient and / or more economical electronic design compared to existing ultrasonic position measurement solutions. Fifth, the system can provide a more space-efficient option for system sizing. Sixth, the system can improve weight, pump requirements, heat load, and measurement accuracy.

[0036] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram illustrating an example of a system for ultrasonic position measurement.

[0038] Figure 2 is an interior view of an example of a linear fluid effector.

[0039] Figure 3 is an interior view of another example of a linear fluid effector.

[0040] Figure 4 is a cross-sectional view of an example of an acoustic interface.

[0041] Figure 5 is a cross-sectional view of an example of a rotating fluid effector.

[0042] Figure 6 This is a conceptual diagram of the transmitted acoustic waveform.

[0043] Figure 7 is a diagram showing an example of a phase shift in an acoustic waveform.

[0044] Figure 8 is a flow chart of an example process for ultrasonic position sensing.

[0045] Fig. 9 Another example of a system for ultrasonic position measurement is shown.

[0046] Fig.10 Another example of a system for ultrasonic position measurement is shown.

[0047] Fig.11 is a conceptual cross-section diagram of another example linear fluid effector.

[0048] Fig.12 is a conceptual cross-section diagram of another example linear fluid effector.

[0049] Fig.13 is an end view of an example transceiver.

[0050] Fig.14 is an end view of another example transceiver.

[0051] Fig.15 is a schematic diagram of an example fluid effector system.

[0052] Fig.16 is a block diagram of an example transducer controller.

[0053] Fig.17 is a block diagram of another example transducer controller.

[0054] Fig.18 is a block diagram of the time-of-flight and rate measurement functional blocks.

[0055] Fig.19 is a plot of an example log10 to linear transformation.

[0056] Fig. 20 is a block diagram of an example simulated cross-correlation module.

[0057] Fig.21 is a block diagram of an example cross-correlation receiver module.

[0058] Fig. 22 is a schematic diagram of an example clock circuit.

[0059] Fig.23 is a schematic diagram of an example template generator circuit.

[0060] Fig.24 is a diagram of an example of signal timing.

[0061] Fig.25 is a block diagram of an example closed-loop control system.

[0062] Fig.26 is a flow chart of another example process for ultrasonic position sensing.

[0063] Fig. 27 is a schematic diagram of an example of a general purpose computer system. DETAILED DESCRIPTION

[0064] This document describes systems and techniques for ultrasonic position sensing, and more particularly, for sensing the position of movable components in a fluid environment, such as valve bodies and piston heads. In general, the ultrasonic position sensing systems and techniques described in this document measure the distance from the movable object to each end of its travel length to determine a ratiometric position value that can be determined without knowing or otherwise determining the speed of sound in the medium in which the ultrasonic signal is transmitted.

[0065] Figure 1 1 is a schematic diagram showing an example of a system 100 for ultrasonic position measurement (e.g., a position sensor system). The system 100 includes a fluid effector 110. The fluid effector 110 includes a housing 112 having an inner surface 114 defining a cavity 116 (e.g., a cylindrical cavity) and a movable body 118. The movable body 118 has a face 120 and a face 122 opposite to the face 120, and is configured to reciprocate within the housing 112. The movable body 118 is configured to contact the inner surface 114 and subdivide the cavity 116 to define a fluid chamber 124 at the face 120 and a fluid chamber 126 at the face 122, and is configured to move longitudinally within the cavity 116.

[0066] The fluid effector 110 includes an acoustic transceiver 130a. The acoustic transceiver 130a includes an acoustic transmitter system configured to transmit a transmit acoustic waveform 132a toward the surface 120 in a first direction. The acoustic transceiver 130a also includes an acoustic receiver system configured to detect a reflected acoustic waveform 133a based on a first reflection of the movable body 118 based on the transmit acoustic waveform 132a. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both the acoustic transmitter and the acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0067] The fluid effector 110 also includes an acoustic transceiver 130b. The acoustic transceiver 130b includes an acoustic transmitter system configured to transmit a transmitted acoustic waveform 132b to the surface 122 in a second direction opposite to the first direction. The acoustic transceiver 130a also includes an acoustic receiver system configured to detect a reflected acoustic waveform 133b based on a second reflection of the movable body 118 based on the transmitted acoustic waveform 132b. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0068] The signal processor 150 is configured to process signals from the acoustic transceiver 130a and the acoustic transceiver 130b to determine the position of the movable body 118 within the cavity 116. The controller 160 (e.g., a computer) is configured to receive the position information from the signal processor 150 and perform functions based on the position information (e.g., control a process, present information to a user, transmit information to another system, record a log). In some embodiments, the signal processor 150 may include a timer (e.g., for measuring the flight time of the transmitted and reflected signals). In some embodiments, the signal processor 150 may include a phase detector (e.g., for determining the phase and / or Doppler shift in the reflected signal).

[0069] In general, the fluid effector 110 is configured as a ratiometric position sensing device. Transmit-receive transducers are located at either end of the effector. Both transmitters can send a pulse echo and receive the echo when it is reflected from the effector piston. When the speed of sound is known, the time measurements of the two transducers can independently determine the position of the movable body. However, when two transducers are coupled into the system, the speed of sound is cancelled and a ratiometric ultrasonic position sensor is obtained. In some implementations, redundancy can be obtained by approximating or measuring the speed of sound if either transducer fails. Techniques for processing signals and several embodiments of the fluid effector 110 will be described in detail below. Figure 2-8 is discussed in the description.

[0070] Figure 2 is an internal view of an example of a linear fluid effector 200. In some implementations, the linear fluid effector 200 may be Figure 1 An example fluid effector 110 is shown.

[0071] The fluid effector 200 includes a housing 212 having an inner surface 214 defining a cavity 216 (e.g., a tubular cavity) and a movable body 218. The housing 212 is generally tubular, having a first longitudinal end 213a and a second longitudinal end 213b opposite the first longitudinal end 213a, and a length indicated by arrow 270.

[0072] The movable body 218 has a face 220a and a face 220b opposite to the face 220a. The movable body 218 is configured to reciprocate within the housing 212. The movable body 218 is configured to contact the inner surface 214 and subdivide the cavity 216 to define a fluid chamber 224a on the side of the face 220a and a fluid chamber 224b on the side of the face 220b.

[0073] In some embodiments, the fluid effector 200 can be configured as a valve. For example, the housing 212 can be a valve housing, and the movable body 218 can be a valve body configured to slide longitudinally within the valve housing to control fluid flow. In some embodiments, the fluid effector 200 can be configured as a pressure regulator or sensor, wherein the fluid pressure in one or both of the fluid chambers 224a-224b can push the movable body 218 to move within the housing. In some embodiments, the fluid effector 200 can be configured as a fluid actuator. For example, the housing 212 can be a hydraulic cylinder, and the movable body 218 can be a piston head that can move within the cavity 216 to promote fluid flow, or a piston head that can be moved within the cavity 216 by the fluid pressure within the fluid chambers 224a-224b. In some embodiments, the fluid effector 200 can be configured as any suitable form of device, wherein the movable body moves linearly within a fluid-filled cavity.

[0074] The fluid effector 200 includes an acoustic transceiver 230a. The acoustic transceiver 230a includes an acoustic transmitter system configured to transmit a transmitted acoustic waveform 232a to the surface 220a through a medium (e.g., fluid) filling the fluid chamber 224a. The acoustic transceiver 230a also includes an acoustic receiver system configured to detect a reflected acoustic waveform 233a based on reflection of the transmitted acoustic waveform 232a off the movable body 218.

[0075] The fluid effector 200 includes an acoustic transceiver 230b. The acoustic transceiver 230b includes an acoustic transmitter system configured to transmit a transmission acoustic waveform 232b to the first face 220b through the medium of the filled fluid chamber 224b. The acoustic transceiver 230b also includes an acoustic receiver system configured to detect a reflected acoustic waveform 233b based on the reflection of the transmitted acoustic waveform 232b off the movable body 218. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0076] The acoustic transceivers 230a-230b are configured to be connected by a Figure 1The example signal processor 150 is activated by an external system of the example signal processor 150, and provides a signal to the external system for processing based on the reflected acoustic waveforms 233a-233b. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0077] The medium through which the acoustic waveforms 232a and 233a propagate has a speed of sound (C1). In the illustrated example, the measured time (t1) (e.g., the first time of flight) combined with the speed of sound (C1) defines a distance L1 (indicated by arrow 260a) from the acoustic transceiver 230a to the face 220a of the movable body 218: 2L1=t1*C1 (Equation 1)

[0078] The medium through which the acoustic waveforms 232b and 233b propagate has a speed of sound (C2). In the illustrated example, the measured time (t2) (e.g., the second time of flight) combined with the speed of sound (C2) defines a distance L2 (indicated by arrow 260b) from the acoustic transceiver 230b to the face 220b of the movable body 218: 2L2=t2*C2 (Equation 2)

[0079] Acoustic transceivers 230a and 230b and movable body 218 may be configured such that the signals are used to determine a ratiometric measure of the position of movable body 218 within its range of motion (e.g., distance L1+L2, or length 270 minus the longitudinal thickness of movable body 218):

[0080] In use, the speed of sound in the fluid filling the cavity 216 does not need to be known or determined. Since both sides of the cavity 216 are filled with the same type of fluid under substantially the same conditions (e.g., temperature), the speed of sound in the fluid will be the same on both sides of the cavity 216, and the speed of sound becomes canceled from equation 3. Moreover, since the speed of sound is not in equation 3, the relative position of the movable body 218 within the cavity 216 becomes a unitless ratio measurement. If desired, the absolute position of the movable body 218 can be determined based on the ratio measurement and a predetermined value of the range of motion (e.g., L1+L2). For example, if the range of motion is known to be 10 cm, and the position is determined to be 0.63 (e.g., based on t1 and t2), the absolute position of the movable body 218 within the cavity 216 can be determined.

[0081] For example, the transducer can be flush with the bore of the cylinder at both ends (e.g., if the piston head is sitting on the wall, the time on the face is zero). In this example, if the piston is exactly in the middle, then t1=t2, which is 50% of the stroke. However, Equation 3 is Position~(t1-t2) / (t1+t2)→(t1=t2) (e.g., the numerator becomes zero). As the piston strokes in one direction, t1 decreases and t2 increases, making the ratio negative. Conversely, as the piston strokes in the opposite direction, the ratio increases. Therefore, in this example, at one stop, the position output is -1, and at the opposite stop, the position output is +1. In another example, for an Equation 3 measurement of 0.63, this will fall between -1 (e.g., retracted) and +1 (e.g., extended). Here the percentage of total stroke becomes (0.63-(-1)) / (1-(-1))→1.63 / 2→81.5% of the total stroke. For a piston configuration with a total stroke of 10 cm, the actual position from the housing dead center would be (L1+L2)*81.5%=10 cm*81.5%=8.15 cm, and the distance from the opposite dead center would be 10 cm-8.15 cm=-1.85 cm.

[0082] Because the ratio metric is based on the distance between the acoustic transceivers 230a and 230b and the faces 220a and 220b, the thickness of the movable body 218 (e.g., the distance between the faces 220a and 220b) does not directly affect the ratio metric. In some implementations, the absolute positions of the faces 220a and 220b can be determined based on the determined absolute position of the movable body 218 and a predetermined thickness of the movable body 218 (e.g., the absolute positions of the faces 220a-220b can be offset from the absolute position of the center of the movable body 218 by half the distance between the positive or negative faces 220a and 220b or another predetermined offset distance).

[0083] The described techniques can be extended to perform additional functions. For example, by checking both sides of the movable body 218, the position of the movable body 218 can be determined. By checking both sides of the movable body 218 again to determine the second position of the movable body, the difference between the two positions and the amount of time between the two measurements can be used to determine the speed of the movable body 218. The determined speed of the movable body 218 and the predetermined knowledge of the mechanical configuration of the fluid effector 200 can be used to determine the linear speed of the movable body 218 (e.g., the speed can be determined and it is known that the movable body 218 moves linearly). In another example, multiple positions and / or speeds can be measured and / or determined, and such information can be used to determine the acceleration of the movable body 218.

[0084] In the example fluid effector 200, acoustic waveforms 232a and 232b are reflected from faces 220a and 220b. The reason the acoustic waveforms 232a and 232b are reflected is because the movable body 218 defines acoustic interfaces at faces 220a and 220b. The fluids in the fluid chambers 224a and 224b have acoustic impedances, and the movable body 218 has different acoustic impedances. As in many types of signal transmission systems, impedance mismatches may cause transmitted signals to be reflected. In the illustrated example in which ultrasonic signals are transmitted, the locations of these impedance mismatches define the locations of the acoustic interfaces. In the illustrated example, faces 220a and faces 220b define the locations of acoustic impedance mismatches and their corresponding acoustic interfaces. Figure 3-5 Other examples of using acoustic interfaces to determine the position of a movable body are discussed in more detail in the description of .

[0085] Figure 3 is an internal view of another example of a linear fluid effector 300 (e.g., a linear piston effector). In some implementations, the linear fluid effector 300 may be Figure 1 An example fluid effector 110. In general, this embodiment also relies on time of flight, but uses shear waves propagating within the cylinder walls of the actuator rather than a hydraulic working fluid.

[0086] The linear fluid effector 300 includes a housing 312 having an inner surface 314 defining a cavity 316. A movable body 318 (e.g., a piston head in the illustrated example) is configured to move longitudinally within the cavity 316 to drive a piston rod 319. The housing 312 is generally tubular having a first longitudinal end 313a and a second longitudinal end 313b opposite the first longitudinal end 313a.

[0087] The movable body 318 has a face 320a and a face 320b opposite to the face 320a. The movable body 318 is configured to reciprocate within the housing 312 with a total stroke (indicated by arrow 370). The movable body 318 is configured to contact the inner surface 314 and subdivide the cavity 316 to define a fluid chamber 324a on the side of the face 320a and a fluid chamber 324b on the side of the face 320b.

[0088] The linear fluid effector 300 includes an acoustic transceiver 330a. The acoustic transceiver 330a includes an acoustic transmitter system configured to transmit a transmitted acoustic waveform 332a to a first side 320a of an acoustic interface 321 through the housing 312. The acoustic transceiver 330a also includes an acoustic receiver system configured to detect a reflected acoustic waveform 333a based on reflection of the transmitted acoustic waveform 332a off the acoustic interface 321.

[0089] The linear fluid effector 300 includes an acoustic transceiver 330b. The acoustic transceiver 330b includes an acoustic transmitter system configured to transmit a transmitted acoustic waveform 332b to a second side 320b of the acoustic interface 321 through the housing 312. The acoustic transceiver 330b also includes an acoustic receiver system configured to detect a reflected acoustic waveform 333b based on reflection of the transmitted acoustic waveform 332b off the acoustic interface 321.

[0090] The acoustic transceivers 330a-330b are configured to be connected by a Figure 1 The example signal processor 150 is activated by an external system of the example signal processor 150, and provides a signal to the external system for processing based on the reflected acoustic waveforms 333a-333b. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0091] Shear waves and / or surface acoustic waves are generated by acoustic transceivers 330a-330b located on opposite ends of the cylinder wall in close acoustic contact with the housing 312. In some embodiments, the acoustic transceivers 330a-330b may be formed of a bonded bulk ceramic, a bulk single crystal or a deposited piezoelectric layer, a film of material, or any other suitable material that may form an integral part of the housing 312. The acoustic transceivers 330a-330b are configured to generate hoop stress in the housing 312 that propagates in an axial direction along the housing 312. Shear waves and surface acoustic waves cannot propagate within the fluid mass, substantially removing the effects of reverberation and cross-coupling within the fluid that may otherwise interfere with measurement accuracy. The waves are reflected when they reach the movable body 318 in close contact with the housing 312, producing a sudden acoustic impedance change in the propagation path.

[0092] In some implementations, this embodiment can be used in applications that cannot accommodate a transducer in contact with the hydraulic fluid medium, cannot accommodate the required pressure port in the hydraulic cylinder, would otherwise benefit from the reduced size and location of the transducer, or require higher measurement accuracy than previous position indicators. In some implementations, sensor accuracy may not be significantly affected compared to echoes in the fluid. The acoustic transceivers 330a-330b can also be located within the inner diameter of the housing 312 in contact with the fluid, or externally on the outside of the housing 312. In some embodiments, the acoustic transceivers 330a-330b can be made as removable transducers. For example, the use of a removable transducer can enable the technology described in this document to be applied or retrofitted to a hydraulic or pneumatic fluid actuator that was not originally designed or conceived to have position sensing functionality when manufactured.

[0093] The process of determining the position of the movable member 318 is similar to that described with respect to Figure 2 The process described for the example fluid effector 200 of the embodiment of the present invention is similar to that described for the example fluid effector 200, except that instead of transmitting and receiving the acoustic waveforms 232a, 232b, 233a, and 233b through the fluid in the fluid chambers 224a and 224b as in the example fluid effector 200, the acoustic waveforms 332a, 332b, 333a, and 333b are transmitted through the housing 312. The transmitted acoustic waveforms 332a and 332b are reflected by the acoustic interface 321 as reflected acoustic waveforms 333a and 333b.

[0094] In use, the flight times of the transmitted acoustic waveforms 332a and 332b and their return as reflected acoustic waveforms 333a and 333b can be measured (e.g., flight times) and used to determine the ratiometric position (and by extension, absolute position) of the movable member 318 and piston rod 319. For example, equations 1-3 discussed above can also be used with the flight times determined from the linear fluid effector 300.

[0095] Figure 4 is a cross-sectional view of an example of an acoustic interface 400. In some examples, the acoustic interface 400 may be Figure 3 424a and 424b. The example acoustic interface 321 of FIG. 421 is shown. In the illustrated example, the housing 412 includes an inner surface 414 defining a cavity 416. The seal 419 is configured to contact the inner surface 414 and the movable body 418 to subdivide the cavity 416 into a fluid chamber 424a and a fluid chamber 424b. The seal 419 contacts the housing 412 at a contact area 420.

[0096] Acoustic impedance is defined as Z = ρ B V P , where ρ B is the bulk density of the medium, and is the longitudinal velocity of the wave in the medium. For example, housing 412 is made of a material having a natural acoustic impedance due to the temperature, density, and other properties of the material from which housing 412 is formed. In the illustrated example, areas of housing 412 having a natural acoustic impedance are represented by the optical dither pattern and identifier 450. For example, the acoustic impedance of aluminum is approximately 17.10 g / cm 2 -sec x10 5 , and the acoustic impedance of 347 stainless steel is about 45.40g / cm 2 -sec x10 5 These are just two examples of the acoustic impedance of two different materials. The techniques described in this document make it unnecessary to know, determine or estimate the acoustic impedance of a material.

[0097] The housing 412 also includes an area of ​​modified acoustic impedance represented by a denser jitter pattern and identifier 460. In some embodiments, the effective acoustic impedance of the material may be affected by mechanical contact or proximity with another object at or around a contact point or proximity point. For example, the mechanical contact between the seal 419 and the housing 412 can acoustically damp the housing 412 at or around the contact area 420 and increase the acoustic density of the housing 412 at or near the contact area 420. In such an example, the area 460 can have a relatively higher acoustic impedance than the area 450. In another example, the seal 419 can have a lower acoustic impedance than the housing 412, and the mechanical contact between the seal 419 and the housing 412 can provide a path with less acoustic impedance for acoustic vibrations propagating along the housing 412 at or near the contact area 420, effectively reducing the acoustic impedance of the acoustic transmission path in the area 460 relative to the area 450.

[0098] In general, when two sections of a transmission medium have different impedances, an impedance mismatch is present. The boundary between the different acoustic impedances defines the location of the acoustic impedance mismatch, which is also referred to as an acoustic interface. In the illustrated example, an acoustic wave traverses at the interface of the fluid and the housing (e.g., along the inner surface 414). When the fluid becomes sealed, an impedance mismatch occurs. The junction where the inner surface 414, the fluid, and the seal 419 coincide with each other defines an acoustic interface 470a and an acoustic interface 470b.

[0099] As in many types of signal transmission processes, a signal that propagates along a transmission path and then encounters an impedance mismatch may cause at least a portion of the signal to be reflected back along the transmission path. Similarly, acoustic signals (e.g., transmitted acoustic waveforms 332a and 332b) may be reflected back toward their sources through acoustic interfaces.

[0100] In the illustrated example, the positions of acoustic interfaces 470a and 470b within housing 412 are defined by the position of movable body 418 within cavity 416 (e.g., movable body 418 defines the position of seal 419, which defines the position of region 460, which defines the position of acoustic interfaces 470a and 470b). Movement of movable body 418 causes acoustic interfaces 470a and 470b to also move.

[0101] Return briefly Figure 3, movement of the movable body 318 results in corresponding movement of acoustic interfaces (e.g., acoustic interfaces 470a and 470b) within the housing 312. As the movable body 318 moves, the distance between the acoustic transceivers 330a and 330b and their respective acoustic interfaces also changes, which causes the flight time of the transmitted acoustic waveforms 332a and 332b and the reflected acoustic waveforms 333a and 333b to change proportionally. As discussed above, the flight time can be used to determine the ratiometric position of the acoustic interface along the housing 312, and therefore determine the position of the movable member 318 within the cavity 316. Also as discussed above, these positions can be determined without knowing or determining the acoustic properties of the housing (e.g., the acoustic impedance of the housing or the acoustic impedance of the region that modifies the acoustic impedance, which can change dynamically with temperature).

[0102] Figure 5 is a cross-sectional view of an example of a rotational fluid effector 500. In some implementations, the rotational fluid effector 500 may be Figure 1 The example fluid effector 110 of the present invention. The rotational fluid effector 500 includes a housing 512 having an inner surface 514 that defines a generally cylindrical cavity 516. A movable body 518 (e.g., a rotating blade in the illustrated example) is configured to move (e.g., rotate, pivot) semi-elliptically within the cavity 516 about a central axis 511 of a shaft 519. In some embodiments, the movable body 518 can be configured to promote rotation of the shaft 519.

[0103] The movable body 518 is configured to contact the inner surface 514 (e.g., directly or through a seal) along a contact region 520 at or along an axial position of the generally cylindrical housing 512. The material used to form the housing 512 has an acoustic impedance, and the contact between the movable body 518 and the housing 512 modifies the acoustic impedance of the housing 512 at or around the contact region 520 to define a region 560 having a modified acoustic impedance. The region 560 presents an acoustic impedance mismatch within the housing 512, having an acoustic interface 570a and an acoustic interface 570b.

[0104] The rotational fluid effector 500 includes an acoustic transceiver 530. The acoustic transceiver 530 includes an acoustic transmitter system configured to transmit a transmitted acoustic waveform 532a to an acoustic interface 570a through the housing 512. The acoustic transceiver 530 also includes an acoustic receiver system configured to detect a reflected acoustic waveform 533a based on reflection of the transmitted acoustic waveform 532a off the acoustic interface 570a.

[0105] The acoustic transceiver 530 is also configured to transmit a transmit acoustic waveform 532b through the housing 512 toward the acoustic interface 570b of the region 560. The acoustic transceiver 530 also includes an acoustic receiver system configured to detect a reflected acoustic waveform 533b based on reflection of the transmit acoustic waveform 532b off the acoustic interface 570b. In the illustrated example, the acoustic transceiver 530 is configured to perform transmission and reception of the acoustic waveforms 532a, 532b, 533a, and 533b (e.g., by "ringing" the housing 512 at a single location and causing the transmit waveforms 532a-532b to propagate away from both sides), but in some embodiments, separate acoustic transceivers may be used (e.g., one configured to ring the periphery of the housing 512 in a clockwise direction, while the other is configured to ring the periphery in a counterclockwise direction).

[0106] The acoustic transceiver 530 is configured to be received by an external system such as Figure 1 The example signal processor 150 of is activated and provides a signal to an external system for processing based on the reflected acoustic waveforms 533a-533b. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be discrete components.

[0107] The process of determining the position of the movable body 518 is similar to that described with respect to Figure 3 The process described for the example linear fluid effector 300 of the embodiment of the present invention is similar to that described for the example linear fluid effector 300, except that instead of transmitting and receiving acoustic waveforms 332a, 332b, 333a, and 333b along the longitudinal length of the housing 312 as in the example linear fluid effector 300, the acoustic waveforms 532a, 532b, 533a, and 533b are transmitted circumferentially (e.g., along a track) around the housing 512. The transmitted acoustic waveforms 532a and 532b are reflected by the acoustic interface 521 as reflected acoustic waveforms 533a and 533b.

[0108] In use, the flight times of the transmitted acoustic waveforms 532a and 532b and their return as reflected acoustic waveforms 533a and 533b can be measured (e.g., time of flight) and used to determine the ratiometric position (and by extension, the absolute position) of the movable body 518 and the shaft 519. For example, equations 1-3 discussed above can also be used with the flight times determined from the rotational fluid effector 500.

[0109] In some embodiments, the rotary fluid effector 500 can be a rotary vane actuator (RVA) or a rotary valve. In some embodiments, the rotary fluid actuator can be modified as a rotary piston actuator (RPA). For example, the emitted waveform can be transmitted circumferentially around a tubular housing toward the end of a rotary piston, the rotary piston being configured to move around the axis of the housing and defining an acoustic interface within a portion of the housing, and the acoustic interface can reflect a portion of the waveform for use in determining the rotational position of the rotary piston.

[0110] Figure 6 is a conceptual diagram 600 of a transmitted acoustic waveform 610 . Figure 7 7 is a graph 700 showing an example of a phase shift in an acoustic waveform. In addition to time-based measurements (e.g., as discussed above), time and phase are related to each other as a function of frequency and wavelength. In the illustrated example, a transmit acoustic waveform 610 is transmitted by an acoustic transceiver 620 as a continuous wave of a single frequency f. The transmit acoustic waveform 610 propagates toward a movable reflector 630 located at a distance D from the reflector. The transmit acoustic waveform 610 is reflected back toward the acoustic transceiver 620 and arrives at the acoustic transceiver 620 after making a round trip of length L=2D.

[0111] The acoustic transceiver 620 propagates some integer n wavelengths plus a fraction, where the wavelength is given by: λ = c / f, where c = speed of sound and f = wave frequency (Equation 4)

[0112] Using Equation 4, the round trip distance to the target can be written as:

[0113] where the term φ / 2π is equivalent to time as shown in Equations 7 and 9. If n1 = 0, Equation 2 is unambiguous, and since the frequency f and the fluid sound velocity are known a priori, D can be determined by direct measurement of the phase of the received signal relative to the transmitted signal.

[0114] When n1>1, D is ambiguous because the measured phase values ​​are repeated at intervals of 2πf. The value n1 can be extracted from the measured data based on the idea that the differential phase shift of two simultaneously propagating waves of different frequencies will generate a gradually increasing phase shift; the increasing value is constant as the propagation time increases. This is Figure 7If two signals are detected at some distance D, and it is known that they started propagating at the same time, the measured phase can be divided by to extract the number of complete wave cycles that occur to generate the measured phase difference. Mathematically:

[0115] The phase difference embodiment modifies the time difference embodiment by applying a fixed frequency f1 to the phase measurement in one of the fluid chambers and another fixed frequency f2 to the other fluid chamber. The exact frequency values ​​of f1 and f2 are not important to the function of the invention, however it is important to select the frequencies to ensure that n1=n2 or n1=n2+1. This relationship ensures The value remains constant over the entire measuring range.

[0116] Rewrite Equation 3 using Equations 7 and 9:

[0117] The phase embodiment retains the same ratiometric benefits of mechanical length and acoustic velocity insensitivity as the time-of-flight embodiment. Frequency f1 is related to f2 at a fixed ratio. This condition ensures that the relative phase difference remains constant as the circuit ages and changes in temperature. Other embodiments may remove this constraint, resulting in reduced aging performance and temperature compensation without substantially changing the method.

[0118] As specified for position measurement, ultrasonic pulses are transmitted periodically. After each transmission, the returning echo signal is sampled at a fixed delay after the transmission. According to equations 13 and 14, this delay defines the depth.

[0119] When the actuator moves between successive firings, at time T s The sampled values ​​acquired will vary with time. Since velocity information can only be obtained periodically, this technique is limited by the Nyquist theorem. This means that for each pulse repetition frequency (F prf ) have a maximum speed:

[0120] The maximum measurable depth is also defined by the pulse repetition frequency:

[0121] Therefore, P max and V max The product of is a constant and is given by:

[0122] Figure 8is a flow chart of an example process 800 for ultrasonic position sensing. In some implementations, process 800 may be performed by Figure 1 Example system 100, example fluid effector 110, Figure 2 An example linear fluid effector 200, Figure 3 An example of a linear fluid effector 300 or Figure 5 The example rotational fluid effector 500 may be performed in whole or in part.

[0123] At 810, a first transmit acoustic waveform is transmitted in a first direction toward a first side of an acoustic interface through an acoustic medium having a first acoustic impedance. For example, the acoustic transceiver 130a may transmit the transmit acoustic waveform 132a toward the face 120 of the movable body 118 through the fluid in the cavity 116. In another example, the acoustic transceiver 530 may transmit the transmit acoustic waveform 532a toward the acoustic interface 570a of the movable body 518 through the housing 512.

[0124] At 820, a second transmit acoustic waveform is transmitted through the acoustic medium in a second direction opposite to the first direction toward a second side of the acoustic interface opposite to the first side. For example, the acoustic transceiver 130b may transmit the transmit acoustic waveform 132b toward the face 122 of the movable body 118 through the fluid in the cavity 116. In another example, the acoustic transceiver 530 may transmit the transmit acoustic waveform 532b toward the acoustic interface 570b through the housing 512.

[0125] At 830, based on the first transmitted acoustic waveform, a first reflected acoustic waveform is reflected by the acoustic interface in a second direction. For example, the surface 120 may reflect the reflected acoustic waveform 133a back toward the acoustic transceiver 130a. In another example, the acoustic interface 570a may reflect the reflected acoustic waveform 533a back toward the acoustic transceiver 530.

[0126] At 840, the second reflected acoustic waveform is reflected by the acoustic interface in the first direction based on the second transmitted acoustic waveform. For example, the surface 122 can reflect the reflected acoustic waveform 133b back toward the acoustic transceiver 130b. In another example, the acoustic interface 570b can reflect the reflected acoustic waveform 533b back toward the acoustic transceiver 530.

[0127] At 850, a first position of the acoustic interface is determined based on the first reflected acoustic waveform and the second acoustic waveform. For example, measurements based on the transmitted acoustic waveforms 132a, 132b, 133a, and 133b or the acoustic waveforms 532a, 532b, 533a, and 533b can be used with equations 1-14 to determine the position of the movable body 118 or 518.

[0128] In some implementations, process 800 may also include determining a first time of flight based on the first transmitted acoustic waveform and the first reflected acoustic waveform, and determining a second time of flight based on the second transmitted acoustic waveform and the second reflected acoustic waveform, wherein determining the first position of the acoustic interface is also based on the first time of flight and the second time of flight. In some implementations, determining the first position of the acoustic interface based on the first time of flight (t1) and the second time of flight (t2) is given by the following equation: (t1-t2) / (t1+t2). For example, Equation 3 shows an example of how the time of flight of a reflected acoustic waveform can be used to determine a ratiometric position of an acoustic interface that causes a reflection.

[0129] In some implementations, process 800 may also include determining a second position of the acoustic interface, and determining a velocity of the acoustic interface based on the first position and the second position. For example, by determining a first position of movable body 118, a second position of movable body 118, and an amount of time between the two positions, a velocity at which movable body 118 is moving may be determined.

[0130] In some implementations, process 800 may include determining a reflected acoustic frequency based on one or both of the first reflected acoustic waveform and the second acoustic waveform, and determining a velocity of the acoustic interface based on the determined reflected acoustic frequency and a predetermined transmit acoustic frequency of one or both of the first transmit acoustic waveform and the second transmit acoustic waveform. For example, transmit acoustic waveforms 132a and 132b may be transmitted at a predetermined transmit frequency, and movement of example movable body 118 may result in a Doppler shift of reflected acoustic waveforms 133a and 113b. The degree of the Doppler shift may be measured to determine a velocity of movable body 118 relative to acoustic transceivers 130a and 130b.

[0131] In some implementations, the acoustic medium can be a fluid having a first acoustic impedance, the acoustic interface can be defined by a movable body within the fluid effector and having a second acoustic impedance different from the first acoustic impedance, a first transmitted acoustic waveform can be transmitted through the fluid toward a first face of the movable body, a second transmitted acoustic waveform can be transmitted through the fluid toward a second face of the movable body disposed opposite the first face, a first reflected acoustic waveform can be based on a first reflection of the first transmitted acoustic waveform by the first face, and a second reflected acoustic waveform can be based on a second reflection of the second transmitted acoustic waveform by the second face. For example, the transmitted acoustic waveforms 132a and 132b can propagate through the fluid in the cavity 116 to the faces 120 and 122, and be reflected back to the acoustic transceivers 130a and 130b by the fluid.

[0132] In some implementations, the acoustic medium can be a housing of a fluid effector having a first acoustic impedance and defining a cavity, and further comprising contacting a portion of the housing with a movable body configured to move within the cavity, and modifying the first acoustic impedance of the contacted portion of the housing based on the contact to define a portion of the housing having a second acoustic impedance different from the first acoustic impedance, wherein the contacted portion of the housing defines an acoustic interface. For example, the contact between the example seal 419 and the example housing 412 can form a region 460 of modified acoustic impedance.

[0133] In some implementations, process 800 may also include determining a phase difference between at least one of: (1) a first transmit phase of the first transmitted acoustic waveform and a first reflection phase of the first reflected acoustic waveform, and (2) a second transmit phase of the second transmitted acoustic waveform and a second reflection phase of the second reflected acoustic waveform, wherein determining the first position of the acoustic interface is also based on the determined phase difference. For example, the phase difference between the transmitted acoustic waveform 132a and the reflected acoustic waveform 133a can be used (e.g., in example equations 4-14) to determine the position of the movable body 118.

[0134] In addition to position, all of the described embodiments can also provide a direct measurement of actuator velocity by incorporating signal processing to extract Doppler shift information (e.g., reflection frequency) from the transducer(s) signal. Although only one of the multiple transducers needs to be processed, Doppler processing of two transducers can provide approximately 1.4 times the accuracy of using a single channel.

[0135] Fig. 9 An example of a system 900 for ultrasonic position measurement (e.g., a position sensor system) is shown. System 900 includes a fluid effector 910. Fluid effector 910 includes a sensor housing 912 defining a cavity 920 having a face 922. Fluid effector 910 also includes an actuator housing 914 having an inner surface 931 defining a cavity 930. Cavities 920 and 930 are fluidly connected by a channel 980. A movable body 938 is configured to reciprocate within cavity 930. Movable body 938 has a face 932.

[0136] In the illustrated example, sensor housing 912 and actuator housing 914 are a unified housing that includes both cavities 920 and 930. As will be described in detail in Fig.15 As discussed in the description of , the sensor housing and the actuator housing may be separate housings.

[0137] The system 900 includes an acoustic transceiver 940a configured as an acoustic transmitter or acoustic transmitter to transmit a transmitted acoustic waveform 942a to the surface 922. The acoustic transceiver 940a is also configured as an acoustic receiver, which is configured to detect a reflected acoustic waveform 944a based on the reflection of the transmitted acoustic waveform 942a off the surface 922. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both the acoustic transmitter and the acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be separate components.

[0138] The system 900 includes an acoustic transceiver 940b configured as an acoustic transmitter or acoustic transmitter to transmit a transmit acoustic waveform 942b to the surface 932. The acoustic transceiver 940b is also configured as an acoustic receiver, which is configured to detect a reflected acoustic waveform 944b based on the reflection of the transmit acoustic waveform 942b off the surface 932. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be separate components.

[0139] The signal processor 960 is configured to process signals from the acoustic transceiver 940a and the acoustic transceiver 940b to determine the position of the movable body 938 within the cavity 930. The controller 970 (e.g., a computer) is configured to receive the position information from the signal processor 960 and perform functions based on the position information (e.g., control a process, present information to a user, transmit information to another system, record a log). In some embodiments, the signal processor 960 may include a timer (e.g., for measuring the flight time of the transmitted and reflected signals). In some embodiments, the signal processor 960 may include a phase detector (e.g., for determining the phase and / or Doppler shift in the reflected signal).

[0140] In general, the fluid effector 910 is configured as a ratiometric position sensing device. The acoustic transceiver 940a is configured to detect a known fixed distance 950a to the face 922, while the acoustic transceiver 940b is configured to detect a variable distance 950b to the face 932 of the movable body 938. When the speed of sound is known, the time measurements of the two acoustic transceivers 940a, 940b can be used to determine the position of the movable body 938. However, when two transducers are coupled into the system, the speed of sound is cancelled out and a ratiometric ultrasonic position sensor is obtained. A channel 980 is provided to improve the equalization of the fluid temperature in the cavities 920, 930, thereby improving the equalization of the speed of sound in the fluid occupying the cavities 920, 930. In some implementations, redundancy can be obtained by approximating or measuring the speed of sound if either transducer fails. Techniques for processing signals and several embodiments of the fluid effector 910 will be described in detail below. Figure 16-26 is discussed in the description.

[0141] exist Fig. 9 In the illustrated example shown in , the fluid effector is configured as a linear (eg, piston) actuator. Fig.10 Another example of a system 1000 for ultrasonic position measurement is shown. The system 1000 is substantially similar to the example system 900, except that the system 1000 includes a fluid effector 1010 configured as a valve.

[0142] The fluid effector 1010 includes a sensor housing 1012 defining a cavity 1020 having a face 1022. The fluid effector 1010 also includes an actuator housing 1014 having an inner surface 1031 defining a cavity 1030. A movable body 1038 is configured for reciprocating movement within the cavity 1030. The movable body 1038 has a face 1032. In the illustrated example, the movable body 1038 is configured as a valve body.

[0143] In the illustrated example, the sensor housing 1012 and the actuator housing 1014 are a unified housing that includes both cavities 1020 and 1030. As will be described in detail in Fig.15 As discussed in the description of , the sensor housing and the actuator housing may be separate housings.

[0144] The system 1000 includes an acoustic transceiver 1040a configured as an acoustic transmitter or acoustic transmitter to transmit a transmit acoustic waveform 1042a toward the surface 1022. The acoustic transceiver 1040a is also configured as an acoustic receiver configured to detect a reflected acoustic waveform 1044a based on the reflection of the transmit acoustic waveform 1042a off the surface 1022. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be separate components.

[0145] The system 1000 includes an acoustic transceiver 1040b configured as an acoustic transmitter or acoustic transmitter to transmit a transmit acoustic waveform 1042b toward the surface 1032. The acoustic transceiver 1040b is also configured as an acoustic receiver configured to detect a reflected acoustic waveform 1044b based on the reflection of the transmit acoustic waveform 1042b off the surface 1032. In some embodiments, a single transducer (e.g., a piezoelectric element) can perform the functions of both an acoustic transmitter and an acoustic receiver. In some embodiments, the acoustic transmitter and the acoustic receiver can be separate components.

[0146] The signal processor 1060 is configured to process signals from the acoustic transceiver 1040a and the acoustic transceiver 1040b to determine the position of the movable body 1038 within the cavity 1030. The controller 1070 (e.g., a computer) is configured to receive the position information from the signal processor 1060 and perform functions based on the position information (e.g., control a process, present information to a user, transmit information to another system, record a log). In some embodiments, the signal processor 1060 may include a timer (e.g., for measuring the flight time of the transmitted and reflected signals). In some embodiments, the signal processor 1060 may include a phase detector (e.g., for determining the phase and / or Doppler shift in the reflected signal).

[0147] Fig.11 1100 is a conceptual cross-sectional view of an example linear fluid effector 1100. In the illustrated example, the effector 1100 is defined by a housing 1102 having an inner surface 1104 defining a cavity 1106.

[0148] The movable member 1110 is configured to move axially within a portion 1120 of the cavity 1106. The portion 1120 is sized to contact the movable body 1110 and partially define a fluid chamber having a cross-sectional area 1121 and can be pressurized to promote linear movement of the movable body 1110.

[0149] Portion 1122 of cavity 1106 is disposed axially adjacent portion 1120 and has an axial cross-sectional area 1123 that is greater than cross-sectional area 1121 of portion 1120. Face portion 1130 is defined by an axial shoulder transition between cross-sectional areas 1121 and 1123.

[0150] Portions 1120 and 1122 together define a unified cavity in which a fluid (e.g., fuel) is free to move between portions 1120, 1122 and maintain a substantially uniform temperature distribution throughout cavity 1106. In the illustrated example, portion 1122 is coaxially larger in cross-section than portion 1120. In some embodiments, portion 1122 may be asymmetrically axially offset from portion 1120. In some embodiments, portion 1122 may be at least partially discontinuous with portion 1120.

[0151] The acoustic transceiver 1140 is arranged at an axial end of the housing 1102. The acoustic transceiver 1140 is configured to transmit a transmission acoustic signal 1150 to the movable body 1110 and the face portion 1130. The face portion 1130 reflects a portion of the transmission acoustic signal 1150 back to the acoustic transceiver 1140 as a reflection acoustic signal 1152. The face portion 1112 of the movable body 1110 reflects another portion of the transmission acoustic signal 1150 back to the acoustic transceiver 1140 as a reflection acoustic signal 1154.

[0152] In operation, a signal processor (e.g. Fig. 9 The example signal processor 960 of the embodiment of the present invention can activate the acoustic transceiver 1140 to transmit the transmitted acoustic signal 1150, and use the acoustic transceiver 1140 to sense the reflected acoustic signals 1152 and 1154. The signal processor can determine the flight time of both the reflected acoustic signals 1152 and 1154 to determine the position of the movable body 1110 within the cavity 1106. The technique for processing the signal will be described in detail below. Figure 16-26 is discussed in the description.

[0153] Fig.12 is a conceptual cross-sectional view of another exemplary linear fluid effector 1200. In general, the linear fluid effector 1200 is Fig.11 A modification of the example linear fluid effector 1100 in which the acoustic transceiver 1140 has been replaced by the acoustic transceiver 1240 .

[0154] Fig.13 yes Fig.1212 is an end view of an example acoustic transceiver 1240. The acoustic transceiver 1240 includes an acoustic transceiver portion 1242 at least partially coaxially surrounding an acoustic transceiver portion 1244. The acoustic transceiver portion 1242 is sized based on the cross-sectional area 1123, and the acoustic transceiver portion 1244 is sized based on the cross-sectional area 1121. The acoustic transceiver portion 1244 is configured to transmit a transmit acoustic signal 1250 toward the movable body 1110, and the acoustic transceiver portion 1242 is configured to transmit a transmit acoustic signal 1251 toward the face portion 1130. The face portion 1130 reflects a portion of the transmit acoustic signal 1251 back toward the acoustic transceiver portion 1242 as a reflected acoustic signal 1252. The face portion 1112 of the movable body 1110 reflects a portion of the transmitted acoustic signal 1250 back toward the acoustic transceiver portion 1244 as a reflected acoustic signal 1254 .

[0155] The acoustic transceiver portions 1242, 1244 may be controlled by a signal processor (e.g., Fig. 9 The signal processor 960 of the example of the embodiment of the present invention is operated and read separately. The signal processor can determine the flight time of both the reflected acoustic signals 1252 and 1254 to determine the position of the movable body 1110 within the cavity 1106. The technology used to process the signal will be described in detail in Figure 16-26 is discussed in the description.

[0156] Fig.14 is an end view of another example acoustic transceiver 1400. In some embodiments, the acoustic transceiver 1400 may be used instead of Figure 12-13 An example acoustic transceiver 1240 is provided.

[0157] The acoustic transceiver 1400 includes an acoustic transceiver portion 1442 radially offset from an acoustic transceiver portion 1444. The acoustic transceiver portion 1442 is sized based on the cross-sectional area 1121, and the acoustic transceiver portion 1444 is sized based on the cross-sectional area 1123. The acoustic transceiver portion 1444 is configured to transmit a transmit acoustic signal to the example movable body 1110, and the acoustic transceiver portion 1442 is configured to transmit a transmit acoustic signal to the example face portion 1130. The face portion 1130 reflects a portion of the acoustic signal transmitted by the acoustic transceiver portion 1442 back to the acoustic transceiver portion 1442 as a reflected acoustic signal. The face portion 1112 of the movable body 1110 reflects a portion of the acoustic signal transmitted by the acoustic transceiver portion 1444 back to the acoustic transceiver portion 1444 as a reflected acoustic signal.

[0158] The acoustic transceiver portions 1442, 1444 may be controlled by a signal processor (e.g., Fig. 9The signal processor 960 of the example of the embodiment of the present invention is operated and read separately. The signal processor can determine the flight time of the two reflected acoustic signals to determine the position of the movable body 1110 within the cavity 1106. The technology used to process the signal will be described in detail in Figure 16-26 is discussed in the description.

[0159] The acoustic transceiver 1440 also includes an acoustic transceiver portion 1446 radially offset from the acoustic transceiver portion 1444. The acoustic transceiver portion 1444 is sized based on the cross-sectional area 1123. The acoustic transceiver portion 1446 is configured to transmit a transmitted acoustic signal to the example face portion 1130. The face portion 1130 reflects a portion of the acoustic signal transmitted by the acoustic transceiver portion 1446 back to the acoustic transceiver portion 1446 as a reflected acoustic signal. In some embodiments, the acoustic transceiver portions 1442 and 1146 are part of a single acoustic transceiver device that can be operated and measured separately from the acoustic transceiver portion 1444. In some embodiments, the acoustic transceiver portion 1446 can be operated and measured separately from the acoustic transceiver portions 1442 and 1144. For example, the acoustic transceiver portion 1446 can be used redundantly in cooperation with the acoustic transceiver portion 1442.

[0160] Fig.15 1500 is a schematic diagram of an example fluid effector system 1500. The system 1500 includes an acoustic fluid measurement module 1502a and an acoustic fluid measurement module 1502b. Each of the acoustic fluid measurement modules 1502a, 1502b includes a sensor housing 1504 defining a cavity 1505 having a predetermined length and a face 1507, and an acoustic transceiver 1506 configured to perform a time-of-flight measurement of the length of the cavity 1505. The acoustic fluid measurement modules 1502a, 1502b can be operated and read by a signal processor 1560 and a controller 1570 to determine the time-of-flight of an acoustic signal within the acoustic fluid measurement modules 1502a, 1502b. In some embodiments, the acoustic fluid measurement modules 1502a, 1502b can provide a time-of-flight measurement similar to Fig. 9 and Fig.10 The functionality of example acoustic transceivers 940a and / or 1040a.

[0161] The system 1500 also includes a collection of fluid effectors 1510a-1510c, each having an actuator housing 1512 defining a cavity 1516, and a movable body 1514 having a face 1517 configured to move axially in the cavity 1516. In various embodiments, each of the fluid effectors 1510a-1510c can be any suitable form of fluid effector, such as a linear fluid actuator or a fluid actuated valve. Each of the fluid effectors 1510a-1510c also includes an acoustic transceiver 1518, which is configured to perform a time-of-flight measurement of the length of the cavity 1516. The acoustic transceiver 1518 can be operated and read by the signal processor 1560 and the controller 1570 to determine the flight time of an acoustic signal within the fluid effector 1510a-1510c. In some embodiments, the acoustic transceiver 1518 can provide a time-of-flight measurement similar to that of a conventional fluid effector. Fig. 9 and Fig.10 Example functionality of acoustic transceivers 940b and / or 1040b.

[0162] In the illustrated example, system 1500 is shown with two acoustic fluid measurement modules and three fluid effectors, although any suitable number of one or more acoustic fluid measurement modules and any suitable number of one or more fluid effectors may be used. For example, a single acoustic fluid measurement module may be used to provide a baseline measurement, or multiple acoustic fluid measurement modules may be used to provide redundancy. In another example, one or more baseline measurements from one or a set of acoustic measurement modules may be used with one, two, three, five, ten, twenty, or any other suitable number of fluid effectors.

[0163] In very general terms, the acoustic fluid measurement modules 1502a, 1502b can be used to provide (e.g., redundant) baseline measurements to which measurements made by the acoustic transceiver 1518 can be compared to determine the position of the movable body 1514. In operation, an operating fluid (e.g., fuel) flows along the supply channel 1540, through the acoustic fluid measurement modules 1502a, 1502b to the fluid effectors 1510a-1510c, and out through the return channel 1542. The signal processor 1560 can activate the acoustic transceiver 1506 to transmit a transmitted acoustic signal, and use the acoustic transceiver 1506 to sense a reflected acoustic signal. The signal processor can determine the flight time of the reflected acoustic signal within the cavity 1505 of known length. The signal processor 1560 can activate the acoustic transceiver 1518 to transmit the transmitted acoustic signal and use the acoustic transceiver 1518 to sense the reflected acoustic signal to determine the flight time of the signal due to the position of the movable body 1514 within the cavity 1516. The signal processor 1560 can compare the flight time from the acoustic fluid measurement modules 1502a, 1502b with the flight time from the fluid effectors 1510a-1510c to determine the position of the movable body 1514 within the cavity 1516. Techniques for processing the signal will be described in detail below. Figure 16-26 is discussed in the description.

[0164] Figure 16-26 Examples of various systems are shown that may be used to perform position measurement and control using devices such as the examples shown and described above.

[0165] To improve the system sizing, two ultrasonic sensors are implemented on either chamber of the fluid effector. The ultrasonic sensor transmits a signal that reflects off the effector and is received by the transducer. The measured time together with the speed of sound defines the distance to the effector (see equation 1). When coupling the two transducers together, the other chamber follows the same form (see equation 2).

[0166] The transducer and effector may be configured so that the signal is used as a ratiometric device, but:

[0167] Due to C1-C2, as a ratiometric device, the effect of the acoustic velocity characteristic is cancelled and is not required for the assessment of position. In addition to time-based measurements, time and phase are related to each other as functions of frequency and wavelength. A continuous wave of a single frequency f propagates toward a movable reflector located at some distance D from the reflector. The wave is reflected back toward the transducer and arrives at the transducer after a round trip of length L = 2D. The wave propagates for some integer n wavelengths plus a fraction, where the wavelength is given by:

[0168] Where c = speed of sound, and f = wave frequency. Using Equation 16, the round trip distance to the target can be written as:

[0169] where the term φ / 2π is equivalent to time according to (19) and (21). If n1 = 0, then (15) is unambiguous, and since the frequency f and the fluid sound velocity are known, the a priori D can be determined by directly measuring the phase of the received signal relative to the transmitted signal.

[0170] When n1>1, D is ambiguous because the measured phase values ​​are repeated at intervals of 2π. The value n1 can be extracted from the measured data based on the idea that the differential phase shift of two simultaneously propagating waves of different frequencies will generate a gradually increasing phase shift; the increasing value is constant as the propagation time increases. If two signals are detected at some distance D, and it is known that they started propagating at the same time, the measured phase can be divided by to extract the number of complete wave cycles that occur to generate the measured phase difference.

[0171] In mathematics,

[0172] The phase difference embodiment modifies the time difference embodiment by applying a fixed frequency f1 to the phase measurement in one of the fluid chambers and another fixed frequency f2 to the other fluid chamber. The exact frequency values ​​of f1 and f2 are not important to the function of the invention, however it is important to select the frequencies to ensure that n1=n2 or n1=n2+1. This relationship ensures The value remains constant over the entire measuring range.

[0173] Rewrite (15) using (19) and (21):

[0174] The phase embodiment retains the same ratiometric benefits of mechanical length and acoustic velocity insensitivity as the time-of-flight embodiment. Frequency f1 is related to f2 at a fixed ratio. This condition ensures that the relative phase difference remains constant as the circuit ages and changes in temperature. Other embodiments may remove this constraint, resulting in reduced aging performance and temperature compensation without substantially changing the method.

[0175] As Figure 1-8 An extension of the linearized ratiometric position sensor that can be modified to place the transceiver elements in a more preferred location. Figure 9-15 In the example of , this is achieved by positioning a transceiver element (XDCR1) in communication with the effector reflection, and a second transceiver element (XDCR2) in a static chamber, sharing a common fluid (e.g., fuel) and therefore similar physical properties with the first transceiver element (XDCR1). The result of the static reference is a logarithmic difference / sum output, which will be outlined below. The transceiver element XDCR1 transmits the signal that is reflected off the effector and received by the transceiver. The measured time together with the speed of sound defines the distance to the effector: L1 = t1 × C1 (Equation 24)

[0176] The transceiver element of the static chamber, XDCR2, follows a similar form: L2 = t2 × C2 (Equation 25)

[0177] The fuel for the second transceiver element XDCR2 in the static chamber is supplied from a source shared with the first transceiver element XDCR1. The transducer and effector may be configured so that the signal is used as a ratiometric device, but:

[0178] Since C1-C2 are ratiometric devices, the effects of the acoustic velocity characteristics are cancelled and are not required for position assessment. XDCR1 monitors the dynamic position of the effector, while XDCR2 acts as a constant distance reference. In some configurations, XDCR1 and XDCR2 can be the same transceiver element, with the output energy divided between the appropriate surfaces. Therefore, the output of Equation 26 is logarithmic. Fig.19 Sample logarithmic output is provided in .

[0179] In addition to position, all of the described embodiments may also provide direct measurement of actuator velocity and / or actuator acceleration by using a combination of signal processing of multiple position samples and / or by extracting Doppler shift information from the transducer signal(s). However, only one of the multiple transducers need be processed. Doppler processing of two transducers provides 1.4 times the accuracy of a single channel.

[0180] As specified for position measurement, ultrasonic pulses are transmitted periodically. After each transmission, the returning echo signal is sampled at a fixed delay after the transmission. According to equations (25) and (26), this delay defines the depth.

[0181] When the actuator moves between successive firings, at time T sThe sample values ​​acquired will vary with time. Unfortunately, this technique is limited by the Nyquist theorem, since velocity information can only be obtained periodically. This means that for each pulse repetition frequency (Fprf) there is a maximum velocity:

[0182] The maximum measurable depth is also defined by the pulse repetition frequency:

[0183] Therefore, P max and V max The product of is a constant and is given by:

[0184] Fig.16 1600 is a block diagram of an example transducer controller. The illustrated example outlines a digital solution for realizing time flight (transmit) and signal processing. In the sample provided, a digital core 1610 (e.g., DSP) outputs a signal RX burst signal and a TX enable signal. An RF amplifier 1612 is stimulated and amplifies the RX burst signal to a suitable voltage for a corresponding sensing system. The amplified signal then passes through a directional coupler 1614 and stimulates a pair of transceiver elements 1620a, 1620b. In some implementations, a directional coupler or some other blocking circuits may be placed in the transmission line to block or limit the feedback of the echo signal from each transducer back to the relative transducer or to the pulse generator. The desired signal returned from a pair of reflecting surfaces 1622a, 1622b is passed through a directional coupler 1614, through a T / R switch 1630 and amplified to an available voltage level by a preamplifier 1632 before receiving at the digital core 1610. Within the digital core 1610, digital signal processing is performed to determine the time transitions and ultimately the ratiometric position of the effector, either linear or logarithmic. With access to the digital core 1610, complex DSP tasks can be performed, enabling determination of effector parameters such as velocity, acceleration, and health monitoring predictions.

[0185] However, in certain aerospace and other high temperature harsh environment applications, ambient temperatures may exceed the capabilities of silicon-based semiconductors. In some embodiments, the DSP-based correlation processors, memories, ADC / DACs, and other standard components required to support such systems may not currently exist in a form that can withstand such harsh environmental conditions. The advantage of an analog correlator is that it can process signals in real time and provide a continuous voltage output at a low frequency, and can reduce or eliminate the need for ADCs, sampled data processing, memory, and / or discrete arithmetic methods. Therefore, analog correlators can be well suited for high temperature implementations in wide bandgap (WBG) semiconductor processes. This provides the possibility of implementing a complete time-of-flight correlation system using WBG semiconductors that can support the required device integration with existing IC process technologies.

[0186] Fig.17 1700 is a block diagram of another example transducer controller 1700. The illustrated example shows an embodiment of a transducer control circuit using an analog approach in the time domain. This circuit excites transducers 1701a, 1701b simultaneously and then measures the time difference between the echoes from the two transducers. The output from the circuit is a difference in voltage as a ratiometric proportional to the relative position of the two targets. A detailed description of the functional blocks follows.

[0187] The pulse generator 1710 is triggered by a pulse repetition rate (PRR) signal that is synchronized with the behavior of the time of flight (TOF) difference on the summing block 1712 and is controlled by the TOF physics of the mechanical system. The generated electrical pulses are sent simultaneously to the two transducers 1701a, 1701b through a bifurcated transmission line. A pair of directional couplers 1714a, 1714b or some other blocking circuit is placed in the transmission line to block or limit the echo signal from each transducer 1701a, 1701b from being fed back to the opposite transducer or to the pulse generator 1710. The pulses are converted into ultrasonic incident waves I1 and I2 respectively by each transducer. The reflected waves from each sensor (R1 and R2) are converted back into small voltage signals respectively.

[0188] The remainder of the description will focus on Fig.17 The two paths behave essentially the same.

[0189] A low noise RF amplifier (LNA) 1720 amplifies the weak signal before passing it to a bandpass filter 1722 which is designed to allow only the frequencies of interest to be forwarded to the remaining circuitry.

[0190] The envelope detector 1724 is an amplitude demodulator configured to extract the baseband envelope pulse from the high frequency AC signal. The envelope is then passed to the timer 1740 through a constant fraction discriminator 1730 (CFD) circuit to obtain a zero-crossing timestamp for the return echo signal with constant amplitude.

[0191] The signals from both paths will now be used again for the remainder of this description.

[0192] Fig.18 FIG. 18 is a block diagram of a time-of-flight and ratiometric functional block. The circuit in the illustrated example is Fig.17 The description of the example timer 1740 and TOF difference / summation block 1712 provides a basis.

[0193] The self-excited oscillator 1810 provides both a time-based trigger to the pulse generator 1812 and a reset signal to the two ramp generators 1814a, 1814b. The linear voltage ramp is fed to the sample and hold (SH) functions 1816a, 1816b to start the sampling timer running. When the CFD output signal 1820a from transducer 1 crosses zero, the comparator 1822a output activates the hold on the SH 1816a, thereby stopping the timer and latching the echo return time t1 as a specific voltage level on its output. Similarly, based on the CFD output signal 1820b from transducer 2 and the comparator 1822b output, the echo return time t2 voltage equivalent value is processed and latched on the output of the SH function 1816b.

[0194] These voltages (times) are continuously updated with each successive pulse-echo cycle at a rate set by the PRR frequency. In doing so, changes in target position are recorded as a continuous sequence of t1 and t2 times.

[0195] These two voltage values ​​t1 and t2 are then fed simultaneously to a differential amplifier 1830 to obtain the differential time t1-t2 and to a summing amplifier 1832 to obtain t1+t2. These differential and summed voltages are then input to an amplifier 1834 which performs the division and produces a differential / summed ratiometric output (t1-t2) / (t1+t2).

[0196] If two opposing transducers are used on either side of a moving target, the output 1840 will be a linear relationship of seconds / second versus position. If one of the two transducers is fixed, the resulting difference / sum relationship will be a logarithmic (log10) curve rather than a linear curve. To make subsequent use of this output easier to use, the logarithmic signal can be linearized by an anti-logarithmic circuit 1844. The inverse exponential or anti-logarithm can be obtained by the equation The exponential amplifier can be implemented with analog circuits. By setting the logarithmic differential / sum voltage from the fixed target setting = x, the three-step process can achieve a linear ramp on output 1842 that is substantially equal in range to the natural linear ramp on output 1840 that occurs for the opposite transducer setting. x is first multiplied by 2.3 and then passed through the exponential amplifier to achieve Finally, the linear scaling and offset function y=mx+b can fit the linear ramp to the desired range. Fig.19 is a graph of an example log10 to linear transformation. In some implementations, a notional circuit can be used to perform this function. The log10 and resulting linear signal are Fig.19 Shown in.

[0197] In yet another embodiment, the ToF sensor may consist of a transmitter and an associated matched filter receiver and a voltage to frequency converter that produces a continuous frequency output proportional to the measured ToF. The transmitter may be a simple pulse generator that periodically charges and dumps the accumulated charge onto a piezoelectric transducer, exciting a crystal step response. Fig. 20 A system functional block diagram of an example analog cross-correlation module 2000 is shown in FIG.

[0198] In this illustrated embodiment, the previously described CFD and ramp timer can be replaced with a frequency domain correlator or matched filter in the receiver. The correlated time-of-flight receiver will consist of a correlator 2010, a low noise amplifier (LNA) 2012, a comparator 2014, a ramp or sawtooth generator 2016, a zero-order sample and hold 2018, and a voltage controlled oscillator. The received signal is amplified by the LNA 2012 and correlated with a local template pulse during a pulse repetition period (PRP), and its output is sampled and held to detect whether a signal is present in the PRP observation window. The analog correlator 2010 includes a standard Gilbert cell (GC), load capacitors, and other supporting circuits. An example implementation of such an analog correlator is as follows: Fig.21 Presentation.

[0199] After a fixed post-TX dead-band interval, the standard GC multiplies the received signal with the template and the product is integrated by the load capacitor. To evaluate the performance and describe the operation of the correlator, a two-tone signal model is also described.

[0200] The correlator 2010 is used to detect the presence of a signal with a known waveform in a noise background. If only noise is present, the output is almost zero; otherwise, the energy of the received signal is integrated with the local template waveform over a fixed time interval to obtain a voltage output above a predetermined threshold. The cross-correlation function can be described by the following equation:

[0201] Where LO(t) is the local template signal, RF(t) is the input F frequency signal of the correlator, and T is the integration period.

[0202] The correlation process can be divided into two steps. The first step involves multiplying the received signal and the reference waveform (local template signal) using the GC. The second step involves integrating the output current via the capacitor.

[0203] Fig.21 An example of a correlator 2100 is depicted in FIG. GC multiplier 2110, which is a current mode element, outputs a differential current 2120. The typical resistive or inductive load of a standard Gilbert mixer is replaced by two current sources 2130a, 2130b and a capacitor 2132 across the differential output node. Because the common mode portion of the output current is absorbed by the current source load, the differential output current is fed directly into the load capacitor. As a result, the capacitor integrates the current and outputs a step-like voltage. Switch 2134, controlled by an internal clock, is used to determine the integration interval and clear the charge in capacitor 2132 at the end of each interval.

[0204] The timing is implemented using a ramp generator and a comparator configured to trigger at a voltage set point along the ramp waveform. An example of such a circuit 2200 is shown in FIG. Fig. 22 2204. A fixed voltage divider with a constant current source bias is used to ratiometrically maintain relative timing between clock events. Ramp 2202 is generated by charging timing capacitor 2204 using a mirror image 2212 of shunt current source 2210. In some implementations, the use of a mirror image can at least partially offset the relative drift between the voltage set point and the PRP ramp voltage, thereby minimizing timing drift over circuit element and IC process variations.

[0205] The sequence of control gates in Fig. 22 . The PRP ramp 2202 is a self-excited oscillator. The cycle begins when the timing capacitor 2204 is reset and the PRP ramp voltage is zero. As the capacitor 2204 charges, the ramp voltage increases, triggering the TX gate comparator 2220 and firing the transducer drive circuit. The timing has a dead band interval built in to disable the receiver during short blanking intervals. This dead band prevents reverberation and other erroneous signals from returning to trigger the correlator prematurely. After the dead band delay, the Xcorr gate comparator 2222 fires, allowing the integration switch on the GC to open and charge the load capacitor. The integrated load capacitor voltage represents the time cross-correlation of the template signal and the receiver signal.

[0206] The measurement interval time point at which the correlator output voltage switches is determined by the ToF of the receiver input signal. Once the correlator switches, the voltage on the load capacitor will begin to decay as soon as the received echo passes, which will reduce the accuracy. To prevent this, the PRP ramp and the correlator output are compared by the SH gate comparator 2224 to generate the SH gate. The SH gate activates the zero-order (sample) hold, which captures the load capacitor voltage when the correlator is excited. The SH gate can be activated at any time after the correlator is enabled by the Xcorr gate, but not before, because the PRP ramp voltage ensures a monotonic sequence of the gates. When the end of the ToF interval is reached, the final PRP end gate is triggered by the PRP end gate comparator 2226, resetting the timing capacitor 2204 and starting the cycle again.

[0207] Reference again Fig. 20 The output of the sensor uses a voltage to frequency (VCO) converter 2020 to map the output of the sample-and-hold output voltage to a scaled frequency proportional to time. The VCO scaling can be adjusted as needed for a specific application to produce the appropriate range.

[0208] VCO drift with temperature is a common problem that has an adverse effect on accuracy in aerospace and other harsh environment applications. Those familiar with the art will recognize that there are several methods for managing temperature-induced VCO frequency and gain scaling drift, but none of them fundamentally changes the operating principles of the system described herein. One example method involves using a combination of components with complementary temperature coefficients in a manner that offsets overall frequency drift, gain scaling, or both. Another example method employs a pair of VCOs with close but different gain scaling functions. Because the frequencies drift apart with temperature, the measured gains and two output frequencies can be combined into a system of two equations and two unknowns, allowing compensation for drift. In addition to the methods described, many other methods are known in the art and will not be listed here.

[0209] Phase noise is generally not a significant error term of interest due to the integration applied to TOF by correlation. When phase noise is significant in this embodiment, it is a product of the specific VCO implementation, not a correlation. Presented above is a method for determining the position of a dynamic effector that produces or is capable of generating a ratiometric position by a linear or logarithmic method. In addition to the physical implementation, also outlined are digital and analog solutions for determining the ratiometric output of the device. This output signal can then be used to communicate with a PID controller and a command source. The ratiometric output signal can be used as a feedback variable for a PID controller and for reporting the position of the effector at a higher level system command source.

[0210] Fig.23is a schematic diagram of an example template generator circuit 2300. In some implementations, the template generator circuit 2300 can be used to generate a matched step response to a transducer by using a matching piezoelectric material as a resonant element.

[0211] Fig.24 Is Fig. 22 An example diagram of signal timing 2400 is provided by example circuit 2200. In general, PRP ramp-based timing can provide ratiometric delay from a single timing capacitor and current source, while adding hysteresis on the PRP timing capacitor reset can reduce supply and temperature induced timing jitter.

[0212] Fig.25 25 is a block diagram of an example closed-loop control system 2500. System 2500 includes a command source 2510, an end effector 2520, and an electronic closed-loop controller 2530. In some embodiments, command source 2510 may be an engine controller. Command source 2510 provides position requests to electronic controller 2530, and electronic controller 2530 is configured to move end effector 2520 via an actuation device.

[0213] End effector 2520 includes a linear feedback sensor 2522. Examples of linear feedback sensors may include a ratiometric ultrasonic position sensor presented herein, a linear variable differential transformer, a linear Hall sensor, an optical sensor, or any other suitable linear feedback sensor.

[0214] Example actuation devices may include, but are not limited to, direct drive valves, pumping systems, electro-hydraulic servovalves, solenoids, solid-state actuators, solid-state pumps, or any suitable actuation device.

[0215] End effectors used for position monitoring may include, but are not limited to, metering valves, regulating valves, equal area actuators, dual area actuators, and any other suitable translation devices.

[0216] The higher level system controller 2530 is in communication with a PID controller (not shown). The PID controller is configured to activate the actuator and cause a translation of the end effector 2520. In some implementations, the PID controller can be configured to adjust the command to the actuator based on a comparison of the current position and the commanded position.

[0217] The electronic controller 2530 receives the feedback signal 2524 from the end effector 2520. The position of the end effector 2520 can then be determined by the feedback regulator 2532 and the feedback controller 2534. In some implementations, the regulator 2532 and the controller 2534 can be in Figure 16-23 The description is discussed in the digital or analog system.

[0218] The determined position is passed to the outer loop feedback module 2536 as a position state for health monitoring and outer loop feedback to the command source 2510. The determined position is also passed to the summing junction 2538, where the current position is compared to the command position defined by the command source 2510 and the signal conditioner 2540. The difference between the requested position and the current position is provided to the controller 2550 (such as a PID controller) and drives the actuator 2552 (such as a brushless DC motor) to move the position of the end effector 2520. The PID controller (not shown) actively adjusts the actuator based on the current position compared to the command position.

[0219] Fig.25 Provided in is an example configuration of a control system. Figure 1-24 The ratiometric position sensing solution and corresponding circuitry may be used in any number of control systems. The ratiometric sensor and digital or analog controller may be applied to many system solutions, including other solutions not specifically described in this document.

[0220] Fig.26 is a flow chart of another example process 2600 for ultrasonic position sensing. In some implementations, process 2600 can be performed by Figure 9-25 The invention may be implemented in whole or in part by the systems and circuits discussed in the description.

[0221] At 2610, a first transmitted acoustic waveform is transmitted through a fluid having a first acoustic impedance toward a first acoustic interface. For example, Fig. 9 The example acoustic transceiver 940a can transmit an acoustic waveform 942a toward the surface 922.

[0222] At 2620 , a second transmit acoustic waveform is transmitted through the fluid toward the second acoustic interface. For example, acoustic transceiver 940 b may transmit transmit acoustic waveform 942 b toward surface 932 .

[0223] At 2630, the first acoustic interface reflects a first reflected acoustic waveform based on the first transmitted acoustic waveform. For example, the surface 922 may reflect the transmitted acoustic waveform 942a as a reflected acoustic waveform 944a.

[0224] At 2640, the second acoustic interface reflects a second reflected acoustic waveform based on the second transmitted acoustic waveform. For example, the surface 932 may reflect the transmitted acoustic waveform 942b as a reflected acoustic waveform 944b.

[0225] At 2650 , a first position of the second acoustic interface is determined based on the first reflected acoustic waveform and the second reflected acoustic waveform. For example, the example signal processor 960 can process signals from the acoustic transceiver 940 a and the acoustic transceiver 940 b to determine the position of the movable body 938 within the cavity 930 .

[0226] In some implementations, a first time of flight may be determined based on a first transmitted acoustic waveform and a first reflected acoustic waveform, and a second time of flight may be determined based on a second transmitted acoustic waveform and a second reflected acoustic waveform, wherein determining the first position of the acoustic interface is also based on the first time of flight and the second time of flight. For example, signal processor 960 may be configured to perform processing based on example equations 15-30 above.

[0227] In some implementations, process 2600 can include determining a first position of the acoustic interface based on the first flight time (t1), and the second flight time (t2) can be given by the equation (t1-t2) / (t1+t2) (e.g., Equation 15).

[0228] In some implementations, process 2600 can also include determining a second position of the second acoustic interface, and determining a velocity of the second acoustic interface based on the first position and the second position. For example, two consecutive position measurements of movable body 938 are used to determine the velocity of movable body 938.

[0229] In some implementations, process 2600 may include determining a reflected acoustic frequency based on one or both of the first reflected acoustic waveform and the second reflected acoustic waveform, and determining a velocity of the second acoustic interface based on the determined reflected acoustic frequency and a predetermined transmit acoustic frequency of the second transmit acoustic waveform. For example, signal processor 960 may include a phase detector (e.g., for determining a phase and / or Doppler shift in a reflected signal).

[0230] In some implementations, the first acoustic interface can be defined by a face of a fluid cavity having a second acoustic impedance different from the first acoustic impedance, the second acoustic interface can be defined by a second face of a movable body within the fluid effector and having a third acoustic impedance different from the first acoustic impedance, the first transmitted acoustic waveform can be transmitted by the fluid toward the first face, the second transmitted acoustic waveform can be transmitted by the fluid toward the second face, the first reflected acoustic waveform can be based on a first reflection of the first transmitted acoustic waveform by the first face, and the second reflected acoustic waveform can be based on a second reflection of the second transmitted acoustic waveform by the second face. For example, the sensor housing and movable body 938 can be made of a material having an acoustic impedance different from the acoustic impedance of the fluid in cavities 920 and 930. The mismatch in acoustic impedance can result in reflections of the transmitted acoustic signals 942a and 942b off faces 922 and 932.

[0231] In some implementations, process 2600 can include determining a phase difference between a second transmit phase of the second transmitted acoustic waveform and a second reflected phase of the second reflected acoustic waveform, wherein determining the first position of the acoustic interface can also be based on the determined phase difference. For example, the distance can be determined based on example Equation 23.

[0232] In some implementations, the first transmit waveform can be transmitted through the first fluid cavity toward a face of the first fluid cavity defining a first acoustic interface, and the second transmit waveform can be transmitted through the second fluid cavity toward a second face of the movable member defining a second acoustic interface. For example, example transmit acoustic waveform 942a can be transmitted through cavity 920, and example transmit acoustic waveform 942b can be transmitted through cavity 930.

[0233] In some implementations, a first transmit waveform can be transmitted through a first portion of the fluid cavity toward a face of the fluid cavity defining a first acoustic interface, and a second transmit waveform can be transmitted through a second portion of the fluid cavity toward a second face of the movable member defining a second acoustic interface. Fig.11 Example transmitted acoustic signal 1150 may be transmitted toward face portion 1130 and face portion 1112 .

[0234] In some implementations, process 2600 may include transmitting a third transmitted acoustic waveform through the fluid toward a third acoustic interface, reflecting a third reflected acoustic waveform by the third acoustic interface based on the third transmitted acoustic waveform, and determining a second position of the third acoustic interface based on the first reflected acoustic waveform and the third reflected acoustic waveform. For example, in example system 1500, a first acoustic signal may be transmitted by one of acoustic transceivers 1506 toward surface 1507, a second acoustic signal may be transmitted by one of acoustic transceivers 1518 toward a corresponding surface 1517, and a third acoustic signal may be transmitted by another of acoustic transceivers 1518 toward another corresponding surface of surfaces 1517.

[0235] Fig. 27 800 is a schematic diagram of an example of a general purpose computer system 2700. According to one implementation, system 2700 may be a data processing device (e.g., a processor system) for the operations described in conjunction with process 800. For example, system 2700 may be included in any or all of signal processors 150, 960, 1060, 1560 or controllers 160, 970, 1070, or 1570.

[0236] The system 2700 includes a processor 2710, a memory 2720, a storage device 2730, and an input / output device 2740. A system bus 2750 is used to interconnect each of the components 2710, 2720, 2730, and 2740. The processor 2710 is capable of processing instructions for execution within the system 2700. In one implementation, the processor 2710 is a single-threaded processor. In another implementation, the processor 2710 is a multi-threaded processor. The processor 2710 is capable of processing instructions stored in the memory 2720 or on the storage device 2730 to display graphical information for a user interface on the input / output device 2740.

[0237] Memory 2720 stores information within system 2700. In one implementation, memory 2720 is a computer readable medium. In one implementation, memory 2720 is a volatile memory unit. In another implementation, memory 2720 is a non-volatile memory unit.

[0238] The storage device 2730 can provide mass storage for the system 2700. In one implementation, the storage device 2730 is a computer-readable medium. In various implementations, the storage device 2730 can be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

[0239] The input / output device 2740 provides input / output operations for the system 2700. In one implementation, the input / output device 2740 includes a keyboard and / or a pointing device. In another implementation, the input / output device 2740 includes a display unit for displaying a graphical user interface. In another implementation, the input / output device 2740 includes a serial link (e.g., Ethernet, CAN, RS232, RS485, optical fiber), for example, which is used to either use a command / response protocol or to connect to a remote host and / or send measurement results through an interface at a periodic update rate after a short initialization period (e.g., <1 second). In another implementation, the input / output device 2740 includes a data bus connection to a second computer system or processor.

[0240] The features described may be implemented in digital electronic circuitry or in computer hardware, firmware, software, or a combination thereof. The apparatus may be implemented in a computer program product tangibly embodied in an information carrier, such as in a machine-readable storage device, for execution by a programmable processor; and the method steps may be performed by a programmable processor executing a program of instructions to perform the functions of the described implementation by operating on input data and generating output. The features described may advantageously be implemented in one or more computer programs executable on a programmable system comprising at least one programmable processor coupled to receive data and instructions from and to transmit data and instructions to a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used directly or indirectly in a computer to perform an activity or produce a result. A computer program may be written in any form of programming language, including compiled or interpreted languages, and it may be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0241] As examples, suitable processors for executing instruction programs include both general and special purpose microprocessors, as well as a single processor or one of multiple processors of any kind of computer. In general, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more memories for storing instructions and data. In general, a computer will also include one or more mass storage devices for storing data files, or operatively coupled to communicate with it; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, as examples, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks and DVD-ROM disks. The processor and memory may be supplemented by or incorporated into an ASIC (Application Specific Integrated Circuit).

[0242] To provide interaction with a user, the features may be implemented on a computer having: a display device, such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user; and a keyboard and pointing device, such as a mouse or trackball, through which the user can provide input to the computer.

[0243] The features may be implemented in a computer system that includes a back-end component, such as a data server; or includes a middleware component, such as an application server or an Internet server; or includes a front-end component, such as a client computer with a graphical user interface or an Internet browser; or any combination thereof. The components of the system may be connected by any form or medium of digital data communication, such as a communication network. Examples of communication networks include, for example, a LAN, a WAN, and the computers and networks that form the Internet.

[0244] A computer system may include clients and servers. Clients and servers are generally remote from each other and typically interact through a network such as the one described. The relationship of client and server arises due to computer programs running on the respective computers and having a client-server relationship to each other.

[0245] Although some implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the accompanying drawings do not require the particular order or sequential order shown to achieve the desired results. In addition, other steps can be provided, or steps can be removed from the described flows, and other components can be added to the described systems, or other components can be removed from the described systems. Therefore, other implementations are within the scope of the appended claims.

Claims

1. A position sensor system, comprising: a sensor housing defining a first cavity having a first face; A fluid effector, the fluid effector comprising: an actuator housing having an inner surface defining a second cavity; and a movable body having a second face and configured to reciprocate within the second cavity; an acoustic transmitter system configured to transmit a first transmitted acoustic waveform toward the first surface and a second transmitted acoustic waveform toward the second surface; and An acoustic receiver system is configured to detect a first reflected acoustic waveform based on a first reflection of the first surface based on the first transmitted acoustic waveform, and to detect a second reflected acoustic waveform based on a second reflection of the second surface based on the second transmitted acoustic waveform.

2. The position sensor system of claim 1 , further comprising a timer configured to determine a first flight time of the first transmitted acoustic waveform and the first reflected acoustic waveform, and to determine a second flight time of the second transmitted acoustic waveform and the second reflected acoustic waveform. 3 . The position sensor system of claim 2 , further comprising a processor system configured to determine a position of the movable body within the second cavity based on the first flight time and the second flight time.

4. The position sensor system according to any one of claims 1 to 3, wherein: The acoustic transmitter system is configured to transmit one or both of the first transmitted acoustic waveform and the second transmitted acoustic waveform through a fluid in one or both of the first cavity and the second cavity, and the acoustic receiver system is configured to receive one or both of the first reflected acoustic waveform and the second reflected acoustic waveform from the fluid in one or both of the first cavity and the second cavity.

5. The position sensor system according to any one of claims 1 to 4, wherein: The acoustic transmitter system is configured to transmit the second transmitted acoustic waveform at a predetermined transmit frequency, and the acoustic receiver system is configured to determine a reflection frequency of the second reflected acoustic waveform.

6. The position sensor system of claim 5, further comprising a processor system configured to determine a velocity of the movable body based on the predetermined transmit frequency and the reflection frequency.

7. The position sensor system according to any one of claims 1 to 5, wherein: The fluid effector is a linear piston effector; The first lumen is a first tubular lumen having a first longitudinal end and a second longitudinal end defining the first face opposite the first longitudinal end; The second lumen is a second tubular lumen having a third longitudinal end and a fourth longitudinal end opposite the third longitudinal end; The movable body is a piston head configured to move longitudinally within the second tubular cavity; The acoustic transmitter system includes a first acoustic transmitter disposed at the first longitudinal end and a second acoustic transmitter disposed at the third longitudinal end; as well as The acoustic receiver system includes a first acoustic receiver disposed at the first longitudinal end and a second acoustic receiver disposed at the third longitudinal end.

8. The position sensor system according to any one of claims 1 to 7, further comprising a unified cavity including the first cavity and the second cavity.

9. The position sensor system according to claim 8, wherein: The first face is defined at least in part by a shoulder extending between the first cavity and the second cavity.

10. The position sensor system according to any one of claims 1 to 9, wherein: The acoustic transmitter system comprises: a first acoustic transmitter configured to transmit the first transmit acoustic waveform toward the first surface; and A second acoustic transmitter is configured to transmit the second transmit acoustic waveform toward the second surface.

11. The position sensor system according to claim 10, wherein: The second acoustic transmitter at least partially concentrically surrounds the first acoustic transmitter.

12. The position sensor system according to any one of claims 1 to 11, further comprising a phase detector configured to determine a difference between at least one of: (1) a first transmission phase of the first transmitted acoustic waveform and a first reflection phase of the first reflected acoustic waveform, and (2) a second transmission phase of the second transmitted acoustic waveform and a second reflection phase of the second reflected acoustic waveform.

13. The position sensor system according to any one of claims 1 to 12, further comprising another movable body having a third surface and configured to reciprocate in a third cavity, wherein the acoustic transmitter system is configured to transmit a third transmitted acoustic waveform to the third surface, and the acoustic receiver system is configured to detect a third reflected acoustic waveform based on a third reflection of the third surface based on the third transmitted acoustic waveform.

14. A position sensing method, comprising: emitting a first emitted acoustic waveform toward a first acoustic interface through a fluid having a first acoustic impedance; transmitting a second transmitted acoustic waveform through the fluid toward a second acoustic interface; reflecting a first reflected acoustic waveform by the first acoustic interface based on the first transmitted acoustic waveform; reflecting a second reflected acoustic waveform based on the second transmitted acoustic waveform by the second acoustic interface; as well as A first position of the second acoustic interface is determined based on the first reflected acoustic waveform and the second reflected acoustic waveform.

15. The method according to claim 14, further comprising: determining a first time of flight based on the first transmitted acoustic waveform and the first reflected acoustic waveform; as well as determining a second time of flight based on the second transmitted acoustic waveform and the second reflected acoustic waveform; Determining the first position of the second acoustic interface is also based on the first flight time and the second flight time.

16. The method according to claim 15, wherein: Determining the first position of the second acoustic interface based on the first flight time (t1) and the second flight time (t2) is given by the following equation: (t1-t2) / (t1+t2).

17. The method according to any one of claims 14 to 16, further comprising: determining a second position of the second acoustic interface; as well as A velocity of the second acoustic interface is determined based on the first position and the second position.

18. The method according to any one of claims 14 to 17, further comprising: determining a reflected acoustic frequency based on one or both of the first reflected acoustic waveform and the second reflected acoustic waveform; as well as A velocity of the second acoustic interface is determined based on the determined reflected acoustic frequency and a predetermined transmitted acoustic frequency of the second transmitted acoustic waveform.

19. A method according to any one of claims 14 to 18, wherein: The first acoustic interface is defined by a first side of the fluid cavity having a second acoustic impedance different from the first acoustic impedance; The second acoustic interface is defined by a second face of the movable body within the fluid effector and having a third acoustic impedance different from the first acoustic impedance; The first transmitted acoustic waveform is transmitted through the fluid toward the first surface; The second transmitted acoustic waveform is transmitted through the fluid toward the second surface; the first reflected acoustic waveform being based on a first reflection of the first transmitted acoustic waveform by the first face; as well as The second reflected acoustic waveform is based on a second reflection of the second transmitted acoustic waveform by the second surface.

20. The method of any one of claims 14 to 19, further comprising determining a phase difference between a second transmitted phase of the second transmitted acoustic waveform and a second reflected phase of the second reflected acoustic waveform, wherein determining the first position of the second acoustic interface is also based on the determined phase difference.

21. The method according to any one of claims 14 to 20, wherein: The first transmitted acoustic waveform is transmitted through the first fluid cavity toward a face of the first fluid cavity defining the first acoustic interface, and the second transmitted acoustic waveform is transmitted through the second fluid cavity toward a second face of the movable member defining the second acoustic interface.

22. The method according to any one of claims 14 to 21, wherein: The first transmitted acoustic waveform is transmitted through a first portion of the fluid cavity toward a face of the fluid cavity defining the first acoustic interface, and the second transmitted acoustic waveform is transmitted through a second portion of the fluid cavity toward a second face of the moveable member defining the second acoustic interface.

23. The method according to any one of claims 14 to 22, further comprising: emitting a third emitted acoustic waveform through the fluid toward a third acoustic interface; reflecting a third reflected acoustic waveform based on the third transmitted acoustic waveform by the third acoustic interface; as well as A second position of the third acoustic interface is determined based on the first reflected acoustic waveform and the third reflected acoustic waveform.

24. A non-transitory computer storage medium encoded with a computer program, the computer program comprising instructions that, when executed by a data processing device, cause the data processing device to perform operations comprising: emitting a first emitted acoustic waveform toward a first acoustic interface through a fluid having a first acoustic impedance; transmitting a second transmitted acoustic waveform through the fluid toward a second acoustic interface; reflecting a first reflected acoustic waveform by the first acoustic interface based on the first transmitted acoustic waveform; reflecting a second reflected acoustic waveform based on the second transmitted acoustic waveform by the second acoustic interface; as well as A first position of the second acoustic interface is determined based on the first reflected acoustic waveform and the second reflected acoustic waveform.

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