Distance measurement system and method employing physically offset transducers

Abstract

A system and method for measuring distance using a physically offset transducer. The system includes first and second transducers physically offset by a preset offset distance for generating a time-of-flight value of an acoustic pulse from the transducers to an object. The processor determines a sound velocity in the medium from the time-of-flight value and the offset distance, and determines a distance of the at least one transducer from the object using the sound velocity and the corresponding time-of-flight value. The controller generates a control signal to control movement of the mobile device according to the determined distance. A method implements the system.

Description

Technical Field

[0001] This disclosure generally relates to distance measurement, and more specifically, to systems and methods configured to measure distance using transducers employing physical offset. Background Technology

[0002] Acoustic navigation and ranging, or sonar navigation and ranging (SONAR), is a technique used to measure distances, such as in underwater environments. To calculate the distance to an object, the time difference between emitting a sound pulse and receiving its echo is measured, and then converted into a distance value based on the known speed of sound. However, the speed of sound can vary significantly depending on the medium through which the sound pulse propagates. Therefore, the reliability of sonar technology can be affected when mobile devices (such as submarines) navigate through various media with different or unknown sound speed characteristics.

[0003] For example, in the field of oil and gas exploration, mobile wellhead equipment or autonomous robots may transition from above-ground air environments to underground gaseous or liquid environments. Such gaseous environments could be underground natural gas pockets or natural gas flowing through the wellbore. Liquid environments could be oil flowing through the wellbore. Therefore, for accurate ranging in such diverse environments, it is crucial to determine the propagation speed of sound waves in the environment through which the mobile device traverses. Summary of the Invention

[0004] According to embodiments consistent with this disclosure, a system and method use a physically offset transducer to measure distance.

[0005] In one embodiment, a system includes a first transducer, a second transducer, a processor, and a controller. The first transducer is configured to emit a first acoustic pulse toward an object in a first direction, receive a first echo of the first acoustic pulse from the object, and generate a first time-of-flight value A for the first acoustic pulse. The second transducer is configured to emit a second acoustic pulse toward the object in the first direction, receive a second echo of the second acoustic pulse from the object, and generate a second time-of-flight value B for the second acoustic pulse. The second transducer is physically offset from the first transducer along the first direction by an offset distance Δd. The processor includes code that executes therein, configured to receive the first time-of-flight value A and the second time-of-flight value B, generate a sound speed value S, and determine a distance value D between the object and at least one of the first and second transducers using the sound speed value S and at least one of the first and second time-of-flight values ​​A and B, respectively. The controller is configured to receive the distance value D and, in response to the distance value D, generate a control signal to control movement of a mobile device.

[0006] The mobile device may include a controller. Alternatively, the controller may be external to the mobile device. The speed of sound value S may correspond to the speed of sound of a medium in the environment of the mobile device. The processor may be configured to determine the speed of sound value S according to S = Δd / |AB|, where the value |AB| is the absolute value of the difference between the first time-of-flight value A and the second time-of-flight value B. The processor may be configured to determine the distance D according to D = S × A when A > B. Alternatively, the processor may be configured to determine the distance D according to D = S × B when B > A. The first transducer and the second transducer may be spaced apart by a length L in a second direction perpendicular to the first direction.

[0007] In another embodiment, a mobile device includes a frame, a propulsion system, a first transducer, a second transducer, and a processor. The propulsion subsystem has an end section and is configured to propel the frame in a first direction in response to a control signal. The first transducer is disposed in the end section and configured to emit a first acoustic pulse toward an object in the first direction, receive a first echo of the first acoustic pulse from the object, and generate a first time-of-flight value A for the first acoustic pulse. The second transducer is disposed in the end section and configured to emit a second acoustic pulse toward the object in the first direction, receive a second echo of the second acoustic pulse from the object, and generate a second time-of-flight value B for the second acoustic pulse. The second transducer is physically offset from the first transducer along the first direction by an offset distance Δd. The processor includes code that executes therein, configured to receive the first time-of-flight value A and the second time-of-flight value B, generate a sound speed value S, and use the sound speed value S and at least one of the first and second time-of-flight values ​​A and B, respectively, to determine a distance value D between the object and at least one of the first and second transducers. The controller is configured to receive a distance value D and generate a control signal in response to the distance value D to control the movement of the mobile device via the propulsion subsystem.

[0008] The rack may include a controller. Alternatively, the controller may be external to the rack. The speed of sound value S may correspond to the speed of sound of the medium in the mobile device environment. The processor may be configured to determine the speed of sound value S according to S = Δd / |AB|, where the value |AB| is the absolute value of the difference between the first time-of-flight value A and the second time-of-flight value B. The processor may be configured to determine the distance D according to D = S × A, where A > B. Alternatively, the processor may be configured to determine the distance D according to D = S × B, where B > A. The first transducer and the second transducer may be spaced apart by a length L in a second direction perpendicular to the first direction in the end section.

[0009] In another embodiment, a method includes providing a processor, a first transducer, and a second transducer, the second transducer being physically offset from the first transducer along a first direction by an offset distance Δd. The method further includes emitting a first acoustic pulse toward an object in the first direction using the first transducer, receiving a first echo of the first acoustic pulse from the object at the first transducer, generating a first time-of-flight value A for the first acoustic pulse using the first transducer, transmitting the first time-of-flight value A to the processor, emitting a second acoustic pulse toward the object in the first direction using the second transducer, receiving a second echo of the second acoustic pulse from the object at the second transducer, generating a second time-of-flight value B for the second acoustic pulse using the second transducer, transmitting the second time-of-flight value B to the processor, receiving the first time-of-flight value A and the second time-of-flight value B at the processor, and generating a sound speed value S based on the first time-of-flight value A, the second time-of-flight value B, and the offset distance Δd. The method further includes determining a distance value D of the object from at least one of the first transducer and the second transducer using the sound speed value S and at least one of the first time-of-flight value A and the second time-of-flight value B. The method further includes transmitting the distance value D and receiving the distance value D at a controller. The method also includes generating a control signal using the controller in response to the distance value D, and controlling the movement of the mobile device in response to the control signal.

[0010] The speed of sound S can correspond to the speed of sound of the medium in the mobile device's environment. Determining the distance D of an object also includes determining the distance D according to S = Δd / |AB|, where the value |AB| is the absolute value of the difference between the first time-of-flight value A and the second time-of-flight value B. The mobile device may include a processor, a first transducer, and a second transducer.

[0011] Any combination of the various embodiments and implementations disclosed herein can be used in another embodiment consistent with this disclosure. These and other aspects and features can be understood from the following description of certain embodiments presented herein, based on this disclosure, the accompanying drawings, and the claims. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a mobile device with a transducer having a physical offset according to an embodiment.

[0013] Figure 2 yes Figure 1 A schematic diagram of an alternative embodiment of a mobile device.

[0014] Figure 3 This is a top front view of an autonomous mobile platform with a sensor module featuring an offset transducer.

[0015] Figure 4 yes Figure 3 A magnified view of the sensor module along line 4-4.

[0016] Figure 5 This is a top front view of an unmanned aerial vehicle (UAV) with an offset transducer.

[0017] Figure 6 yes Figure 5 A bottom view of the base of the UAV.

[0018] Figure 7 This is a top front view of a submarine with a physically offset transducer.

[0019] Figures 8A-8B yes Figure 1-2 A flowchart of how to operate a mobile device.

[0020] It should be noted that the accompanying drawings are illustrative and not necessarily drawn to scale. Detailed Implementation

[0021] Example embodiments consistent with the teachings included in this disclosure relate to a system and method configured to use a transducer with physical offset to measure distance.

[0022] refer to Figure 1 The mobile device 10 includes a processor 12, a memory 14, a mobile device controller 16, a first transducer 18, and a second transducer 20. The processor 12 includes code that executes therein. The mobile device 10 is located near the object 22. The mobile device 10 can be any known type of device capable of moving in space relative to an object such as object 22. In one embodiment, such as Figure 1 As shown, mobile device 10 includes a mobile device controller 16 configured to control movement of mobile device 10. As described herein, for example, mobile device 10 may be... Figure 3-4 The autonomous downhole robot 100 shown in the figure Figure 5-6 The unmanned aerial vehicle (UAV) 200 shown Figure 7 The submarine 300 shown. In alternative embodiments, such as Figure 2 As shown, the mobile device 50 is operatively connected to an external controller 52. For example, the mobile device 50 may be a semi-autonomous downhole robot connected to a tether, which in turn is connected to an external controller 52 located on the Earth's surface.

[0023] Transducers 18 and 20 are disposed within mobile device 10. For example, mobile device 10 may have a housing or frame 28 with openings. Transducers 18 and 20 are exposed to the external environment through the openings. A first transducer 18, labeled A, has a distance D1 from its emitter 24 to object 22. A second transducer 20, labeled B, has a distance D2 from its emitter 26 to object 22. The emitter 26 of the second transducer 20 is physically offset from the emitter 24 in a first direction by a predetermined offset distance Δd > 0. The first direction may be the direction of movement of mobile device 10. Alternatively, the first direction may be a direction parallel to the longitudinal axis of mobile device 10. The offset distance Δd = |D1 - D2|, which is the absolute value of the difference between distances D1 and D2. In an example embodiment, Δd = 10 mm. Figure 1 As shown, for example, D1>D2. However, in an alternative embodiment, without loss of generality, transducers 18, 20 may be disposed in the mobile device 10, wherein transducers 18, 20 are positioned relative to each other along a first direction, wherein D2>D1.

[0024] refer to Figure 3-4 In one embodiment of the mobile devices 10 and 50, the autonomous downhole robot 100 has a plurality of modules 112, 114, 116, and 118 configured to move in a first direction 120. Module 112 may be equipped with... Figure 1-2 The sensor or navigation module of transducers 18, 20, which are physically offset as shown. Modules 114, 118 may be drive modules with treads 128. Treads 128 can extend from or retract into the respective drive modules 114, 118. Module 116 may be a sensor or navigation module with... Figure 1-2 The processor 12, memory 14, and controller 16 shown are computing modules. The autonomous downhole robot 100 can be a robot-actuated two-degree-of-freedom (2-DOF) downhole tool that can operate in highly variable flowing wellbore environments to scan and generate three-dimensional point cloud data of the wellbore's internal geometry.

[0025] refer to Figure 4 The front end of the navigation module 112 is shown. End sections 24 and 26 of transducers 18 and 20 are exposed to transmit and receive sound, respectively. End sections 24 and 26 are laterally spaced apart by a lateral length L, which extends in a second direction perpendicular to a first direction 120. The first direction 120 may be the longitudinal axis of the autonomous downhole robot 100. The length L may be relatively small, for example, between 5 mm and 10 mm, to measure distances within the wellbore.

[0026] refer to Figure 5-6In alternative embodiments of mobile devices 10 and 50, UAV 200 has a frame 202 from which multiple rotors 204, 206, 208, 210 and multiple outriggers 212, 214, 216, 218 extend. UAV 200 is configured to fly to, hover over, perch on, and take off from surface 220 of structure 222. A first pair of physically offset transducers 224, 226 may be disposed in frame 202, wherein transducers 224, 226 are configured to detect objects in the XY plane in which UAV 200 travels. Figure 5-6 As shown, the UAV 200 may also have a base 228, which has feet 230 at the ends of the legs 212, 214, 216, and 218. The UAV 200 also includes a second pair of physically offset transducers 232 and 234 configured to detect objects, such as surface 220, in the Z direction. As described above, the lateral length L between transducers 232 and 234 may be 10 mm. (Reference) Figure 7 In an additional alternative embodiment, the mobile devices 10, 50 may be a submarine 300 with at least one pair of physically offset transducers 302, 304, wherein the transducers 302, 304 have a lateral length L between them. Typically, submarines encounter relatively large objects underwater, so the lateral length L of the submarine 300 can be on the order of meters, for example, 1 m. It should be understood that the lateral length L between the transducers of any mobile device can be determined by the overall size of the mobile device and the approximate size of the objects the mobile device may encounter during its movement.

[0027] like Figure 1-2 As indicated by the arrows between transducers 18 and 20 and object 22, transducers 18 and 20 transmit and receive sound. In one embodiment, transducers 18 and 20 transmit and receive ultrasound. In an alternative embodiment, transducers 18 and 20 can transmit and receive sound of any wavelength or frequency. For example, the first transducer 18 can transmit sound with a center frequency of 1 MHz, and the second transducer 20 can transmit sound with a center frequency of 4 MHz. One advantage of using different center frequencies transmitted by transducers 18 and 20 is that different center frequencies reduce or eliminate crosstalk or acoustic interference involving such transducers 18 and 20. Transducers 18 and 20 can transmit at different center frequencies. In an alternative embodiment, transducers 18 and 20 can transmit at the same center frequency.

[0028] Refer again Figure 1-2Under the control of processor 12, first transducer 18 can emit a first acoustic pulse toward object 22 in a first direction. First transducer 18 can receive a first echo of the first acoustic pulse from object 22. First transducer 18 can generate a first time-of-flight value A for the first acoustic pulse. First transducer 18 can transmit the first time-of-flight value A to processor 12. Similarly, under the control of processor 12, second transducer 20 emits a second acoustic pulse toward object 22 in a first direction. Second transducer 20 can receive a second echo of the second acoustic pulse from object 22. Second transducer 20 can generate a second time-of-flight value B for the second acoustic pulse and transmit the second time-of-flight value B to processor 12.

[0029] Processor 12 receives a first time-of-flight value A and a second time-of-flight value B, and generates a sound speed value S from the first time-of-flight value A, the second time-of-flight value B, and the offset distance Δd according to the formula S=Δd / |AB|. The sound speed value S corresponds to the speed of sound in the medium of the environment through which the mobile device 10 is positioned or moving. Processor 12 uses the sound speed value S and at least one of the first time-of-flight value A and the second time-of-flight value B to determine a distance value D between the object 22 and at least one of the first transducer 18 and the second transducer 20. For example, when A>B, the distance D is determined by processor 12 according to D=S × A. When A>B, the distance D=D1=D2+Δd. Alternatively, when B>A, the distance D is determined by processor 12 according to D=S × B. When B>A, the distance D=D2=D1+Δd. Memory 14 is configured to store values ​​including the first time-of-flight value A, the second time-of-flight value B, the offset distance Δd, the sound speed value S, and the distance D.

[0030] Processor 12 can send the distance value D to... Figure 1-2 The mobile device controller 16 or external controller 52 shown is configured to respond to a distance value D. The mobile device controller 16 or external controller 52 can generate a control signal based on the distance value D, representing the distance from the mobile device 10 to the object 22. In response to the control signal, the mobile device controller 16 or external controller 52 can control the movement of the mobile device 10. For example, the mobile device 10 may include a propulsion subsystem 30. In response to the control signal, the propulsion subsystem 30 can cause the mobile device 10 to move toward the object 22, move away from the object 22, move around the object 22, or maintain a fixed distance from the object 22, depending on the situation of the mobile device and the object 22. For example, using a defined distance D, Figure 3-4The autonomous downhole robot 100 can detect an object 22 in its path. The robot 100 can then approach the object 22 in a first direction, retreat from the object 22, go around the object 22, or stop at a fixed distance from the object 22. Since the autonomous downhole robot 100 can move through the wellbore using natural gas, oil, or other gaseous or liquid media, the moving device 10 of the robot 100 is capable of determining the local speed of sound and then accurately determining the distance D to perform such manipulation.

[0031] Similarly, using the determined distance D, Figures 5 to 6 The UAV 200 can approach the surface 220 of the structure 222, perch or land on the surface 220, hover at a fixed distance from the surface 220, or fly away from the surface 220. Since the UAV 200 can move in the air or in other gaseous media near the surface 220 of the structure 222, the mobile device 10 embodying the UAV 200 is able to determine the local speed of sound and then accurately determine the distance D to perform such manipulation. In another embodiment, using the determined distance D, Figure 7 The submarine 300 shown can move underwater in any direction, depending on the orientation of the transducers 302 and 304 toward the selected direction. Since the submarine can travel in seawater or freshwater, the local speed of sound can vary. Therefore, the mobile device 10, embodied in the submarine 300, can determine the local speed of sound and then accurately determine the distance D to perform such maneuvers.

[0032] like Figures 8A-8B As shown, the operating method 500 of the system using a physically offset transducer involves providing such a physically offset transducer in step 502, wherein the transducer is physically offset towards the object 22 in a first direction by a predetermined offset distance Δd, such as... Figure 1-2 As shown. In step 504, the first transducer 18, under the control of the processor 12, emits a first acoustic pulse toward the object 22 in a first direction. In step 506, the first transducer 18 can receive a first echo of the first acoustic pulse from the object 22. In step 508, the first transducer 18 can generate a first time-of-flight value A of the first acoustic pulse. In step 510, the first transducer 18 can transmit the first time-of-flight value A to the processor 12. Similarly, in step 512, the second transducer 20, under the control of the processor 12, emits a second acoustic pulse toward the object 22 in a first direction. In step 514, the second transducer 20 can receive a second echo of the second acoustic pulse from the object 22. The second transducer 20 can generate a second time-of-flight value B of the second acoustic pulse in step 516, and the second transducer 20 transmits the second time-of-flight value B to the processor 12 in step 518.

[0033] In step 520, processor 12 receives a first time-of-flight value A and a second time-of-flight value B, and in step 522, generates a sound speed value S from the first time-of-flight value A, the second time-of-flight value B, and the offset distance Δd. The sound speed value S is determined according to S = Δd / |AB|. The sound speed value S corresponds to the speed of sound in the medium of the environment in which the mobile device 10 is positioned or moving. In step 524, processor 12 uses the sound speed value S and at least one of the first time-of-flight value A and the second time-of-flight value B to determine a distance value D between the object 22 and at least one of the first transducer 18 and the second transducer 20. For example, when A > B, the distance D is determined by processor 12 according to D = S × A. When A > B, the distance D = D1 = D2 + Δd. Alternatively, when B > A, the distance D is determined by processor 12 according to D = S × B. When B > A, the distance D = D2 = D1 + Δd. The memory 14 is configured to store values ​​including a first flight time value A, a second flight time value B, an offset distance Δd, a sound speed value S, and a distance D.

[0034] Processor 12 may send distance value D to mobile device controller 16 in step 526, and mobile device controller 16 may receive distance value D in step 528. In response to distance value D, in step 530, mobile device controller 16 may generate a control signal representing the distance from mobile device 10 to object 22 based on distance value D. In response to the control signal, mobile device controller 16 may use the control signal to control mobile device 10 in step 532. Controlling mobile device 10 may include controlling the movement of mobile device 10.

[0035] In alternative embodiments, multiple physically offset transducers, such as three or more transducers emitting sound in a common first direction, can be used to improve the accuracy of determining the local sound velocity, and consequently, the accuracy of determining the distance of the transducer to an object. In further embodiments, multiple physically offset transducers can be used in any known device that is mobile, semi-mobile, fixed to the ground or structure, or fixed to the ground, wherein the device is configured to determine distances. For example, ground surveying equipment can use such physically offset transducers to determine the distance to an object (e.g., a marker or landmark). Therefore, as... Figure 4 and Figure 6-7 As shown, the original method of triangulation, which required multiple sensors located at different positions, can be replaced by only two transducers with physical offsets. These two transducers are separated by a relatively small lateral length L, and their physical offset direction extends along a first direction toward the object. There is a preset offset distance Δd between them.

[0036] Some steps of the methods described herein can be executed in a machine-readable form by software or firmware stored on a tangible (e.g., non-transitory) storage medium. For example, the software or firmware can exist as a computer program containing computer program code; when the program is run on a computer or suitable hardware device, this code enables the system to perform the various operations described herein, and the computer program can be specifically implemented on a computer-readable medium. Examples of tangible storage media include computer storage devices with computer-readable media such as disks, USB flash drives, and flash memory, which do not contain propagating signals. Propagating signals can exist in the tangible storage medium. The software can be adapted to execute on a parallel or serial processor, thereby enabling the various operations described herein to be performed in any suitable order or simultaneously.

[0037] It should also be understood that the same or similar reference numerals in the drawings denote the same or similar elements in several drawings, and not all embodiments or arrangements require reference to all parts or steps described and shown in the drawings.

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that, when used in this specification, the terms “comprising,” “including,” “including,” “comprise,” “including,” and / or “including,” and variations thereof, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0039] Orientation terms used herein are for convention and reference purposes only and should not be construed as restrictive. However, it should be recognized that these terms may be used by reference to an operator or user. Therefore, no limitation is implied or inferred. Furthermore, ordinal numbers (e.g., first, second, third) are used for distinction rather than counting. For example, the use of “third” does not imply the existence of a corresponding “first” or “second.” Moreover, the wording and terminology used herein are for descriptive purposes and should not be considered limiting. The use of “including,” “contains,” “has,” “involves,” and variations thereof in this document is intended to cover the items listed thereafter and their equivalents, as well as additional items.

[0040] While several exemplary embodiments have been described in this disclosure, those skilled in the art will understand that various changes can be made and elements can be substituted with equivalents without departing from the spirit and scope of the invention. Furthermore, those skilled in the art will understand that many modifications will be made to adapt particular instruments, situations, or materials to embodiments of this disclosure without departing from the basic scope of this disclosure. Therefore, it is intended that the invention be limited to the specific embodiments disclosed, or the best mode contemplated for carrying out the invention, but rather that the invention will encompass all embodiments falling within the scope of the appended claims.

[0041] The foregoing subject matter is provided by way of illustration only and should not be construed as limiting. Various modifications and changes may be made to the subject matter described herein without following the illustrated and described exemplary embodiments and applications, and without departing from the true spirit and scope of the invention as defined by a set of the following claims and equivalent structures, functions or steps.

Claims

1. A system comprising: a first transducer configured to emit a first acoustic pulse in a first direction toward an object, receive a first echo of the first acoustic pulse from the object, and generate a first time-of-flight value A of the first acoustic pulse; a second transducer configured to emit a second acoustic pulse in the first direction toward the object, receive a second echo of the second acoustic pulse from the object, and generate a second time-of-flight value B of the second acoustic pulse, wherein the second transducer is physically offset from the first transducer by an offset distance Ad in the first direction; a processor including code executing therein, the code configured to receive the first time-of-flight value A and the second time-of-flight value B, generate a speed-of-sound value S, and determine a distance value D of the object from at least one of the first transducer and the second transducer using the speed-of-sound value S and at least one of the first time-of-flight value A and the second time-of-flight value B, respectively; and a controller configured to receive the distance value D and generate a control signal to control movement of a mobile device in response to the distance value D.

2. The system of claim 1, wherein, the mobile device includes the controller.

3. The system of claim 1, wherein, the controller is external to the mobile device.

4. The system of claim 1, wherein, the speed-of-sound value S corresponds to a speed of sound of a medium in an environment of the mobile device.

5. The system of claim 1, wherein, the processor is configured to determine the speed-of-sound value S according to S = Ad / |A - B|, where the value |A - B| is an absolute value of a difference between the first time-of-flight value A and the second time-of-flight value B.

6. The system of claim 1, wherein, the processor is configured to determine the distance D according to D = S x A, where A > B.

7. The system of claim 1, wherein, the processor is configured to determine the distance D according to D = S x B, where B > A.

8. The system of claim 1, wherein, the first transducer and the second transducer are spaced apart by a length L in a second direction perpendicular to the first direction.

9. A mobile device comprising: a chassis; a propulsion subsystem having an end segment and configured to propel the chassis in a first direction in response to a control signal; a first transducer disposed in the end segment configured to emit a first acoustic pulse in the first direction toward an object, receive a first echo of the first acoustic pulse from the object, and generate a first time-of-flight value A of the first acoustic pulse; a second transducer disposed in the end segment configured to emit a second acoustic pulse in the first direction toward the object, receive a second echo of the second acoustic pulse from the object, and generate a second time-of-flight value B of the second acoustic pulse, wherein the second transducer is physically offset from the first transducer by an offset distance Ad in the first direction; and a processor including code executing therein, the code configured to receive the first time-of-flight value A and the second time-of-flight value B, generate a speed-of-sound value S, and determine a distance value D of the object from at least one of the first transducer and the second transducer using the speed-of-sound value S and at least one of the first time-of-flight value A and the second time-of-flight value B, respectively, wherein the controller is configured to receive the distance value D and generate the control signal to control movement of a mobile device by the propulsion subsystem in response to the distance value D.

10. The mobile device of claim 9, wherein, The rack includes the controller.

11. The mobile device of claim 9, wherein, The controller is external to the rack.

12. The mobile device of claim 9, wherein, The speed of sound value S corresponds to a speed of sound of a medium in an environment of the mobile device.

13. The mobile device of claim 9, wherein, The processor is configured to determine the speed of sound value S according to S = Ad / |A-B|, wherein the value |A-B| is an absolute value of a difference between the first time of flight value A and the second time of flight value B.

14. The mobile device of claim 9, wherein, The processor is configured to determine the distance D according to D = S x A, wherein A > B.

15. The mobile device of claim 9, wherein, The processor is configured to determine the distance D according to D = S x B, wherein B > A.

16. The mobile device of claim 9, wherein, The first transducer and the second transducer are spaced apart in a second direction perpendicular to the first direction by a length L in the end section.

17. A method comprising: providing a processor, a first transducer, and a second transducer, the second transducer being physically offset from the first transducer by an offset distance Ad in a first direction; emitting a first acoustic pulse toward an object in the first direction using the first transducer; receiving a first echo of the first acoustic pulse from the object at the first transducer; generating a first time of flight value A of the first acoustic pulse using the first transducer; transmitting the first time of flight value A to the processor; emitting a second acoustic pulse toward the object in the first direction using the second transducer; receiving a second echo of the second acoustic pulse from the object at the second transducer; generating a second time of flight value B of the second acoustic pulse using the second transducer; transmitting the second time of flight value B to the processor; receiving the first time of flight value A and the second time of flight value B at the processor; generating a speed of sound value S from the first time of flight value A, the second time of flight value B, and the offset distance Ad; determining a distance value D of the object from at least one of the first transducer and the second transducer using the speed of sound value S and at least one of the first time of flight value A and the second time of flight value B, respectively; receiving the distance value D at a controller; generating a control signal using the controller in response to the distance value D; and controlling movement of a mobile device in response to the control signal.

18. The method of claim 17, wherein, The speed of sound value S corresponds to a speed of sound of a medium in an environment of the mobile device.

19. The method of claim 17, wherein, Determining the distance value D of the object further includes determining the distance value D according to S = Ad / |A-B|, wherein the value |A-B| is an absolute value of a difference between the first time of flight value A and the second time of flight value B.

20. The method of claim 17, wherein, The mobile device includes the processor, the first transducer, and the second transducer.

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