阅读说明：本技术 用于距离偏移量测量的传感器装置 (Sensor device for measuring distance offset ) 是由 B.帕罗特 S.帕特尔 F.阿卜杜拉蒂夫 P.卡拉斯科扎尼尼 A.艾默 A.奥塔 A.阿 于 2019-02-06 设计创作，主要内容包括：一种用于测量沿着纵向轴线的偏移量的感测装置包括：壳体,其包含多个狭槽；沿着所述纵向轴线对准的光学传感器的两个或更多个阵列,所述阵列中的至少一个相对于其它阵列沿着所述纵向轴线偏移；以及微控制器,其耦合到光学传感器的所述两个或更多个阵列且被配置成确定沿着所述纵向轴线的位置偏移,光学传感器的阵列中的至少一个在所述位置偏移处检测到光。在一些实施例中,所述阵列的光学传感器中的每一个定位于所述壳体内在所述多个狭槽中的一个下方以减少所接收辐射的入射角。(A sensing device for measuring an amount of deflection along a longitudinal axis comprising: a housing comprising a plurality of slots; two or more arrays of optical sensors aligned along the longitudinal axis, at least one of the arrays being offset along the longitudinal axis relative to the other arrays; and a microcontroller coupled to the two or more arrays of optical sensors and configured to determine a positional offset along the longitudinal axis at which at least one of the arrays of optical sensors detects light. In some embodiments, each of the optical sensors of the array is positioned within the housing below one of the plurality of slots to reduce an angle of incidence of the received radiation.)

1. A sensing device for measuring an amount of deflection along a longitudinal axis, comprising:

a housing including a front surface having a plurality of slots;

two or more arrays of optical sensors linearly aligned along the longitudinal axis, at least one of the two or more arrays being offset along the longitudinal axis relative to the other of the at least two arrays;

a microcontroller coupled to the two or more arrays of optical sensors and configured to determine a positional offset along the longitudinal axis at which at least one of the two or more arrays of optical sensors detects light;

wherein each of the optical sensors of the two or more arrays is positioned within the housing below one of the plurality of slots so as to reduce an angle of incidence of radiation received by the optical sensors.

2. The sensing device of claim 1, wherein at least some of the plurality of slots are inclined toward a center to further reduce the angle of incidence of radiation received by the optical sensor.

3. The sensing device of claim 1, wherein the two or more arrays of optical sensors together cover all locations along a distance span along the longitudinal axis.

4. The sensing device of claim 1, further comprising at least one filter element positioned within the housing and at least partially covering the two or more arrays of the optical sensors so as to block wavelengths other than a wavelength of a laser reference beam from reaching the optical sensors.

5. The sensing device of claim 1, further comprising:

an additional array of optical sensors arranged linearly with respect to a transverse axis perpendicular to the longitudinal axis,

wherein the microcontroller is coupled to the additional array of optical sensors and configured to determine a positional offset along the transverse axis at which the additional array of optical sensors detect light.

6. The sensing device of claim 1, wherein at least one of the two or more arrays of optical sensors is positioned at a different depth below the plurality of slots than the other of the two or more arrays.

7. The sensing device of claim 1, wherein the two or more arrays of optical sensors include photodiodes sensitive to the wavelength of a laser reference beam.

8. The sensing device of claim 1, further comprising an accelerometer adapted to measure the tilt of the device relative to a gravity vector.

9. The sensing device of claim 1, wherein at least one of the two or more arrays of optical sensors comprises a single continuous optical sensor.

10. The sensing device of claim 1, wherein the two or more arrays of optical sensors comprise:

a first array of optical sensors linearly aligned along the longitudinal axis;

a second array of optical sensors linearly aligned along the longitudinal axis, the second array being adjacent to the first array and offset along the longitudinal axis relative to the first array; and

a third array of optical sensors arranged in linear alignment along the longitudinal axis, the third array being positioned adjacent to the second array and offset along the longitudinal axis relative to the second array opposite the first array.

11. A sensing device for measuring an amount of deflection along a longitudinal axis, comprising:

a housing having a front surface;

two or more arrays of optical sensors arranged in linear alignment along the longitudinal axis within the housing, at least one of the two or more arrays being offset along the longitudinal axis relative to the other of the at least two arrays;

a microcontroller coupled to the two or more arrays of optical sensors and configured to determine a positional offset along the longitudinal axis at which at least one of the two or more arrays of optical sensors detects light;

wherein one of the two or more arrays is positioned at a different depth below the front surface of the housing than the other arrays.

12. The sensing device of claim 11, wherein each of the two or more arrays of the optical sensors is positioned within the housing below one of a plurality of slots so as to reduce an angle of incidence of radiation received by the two or more arrays of the optical sensors.

13. The sensing device of claim 12, wherein at least some of the plurality of slots are inclined toward a center to further reduce the angle of incidence of radiation received by the optical sensor.

14. The sensing device of claim 11, wherein the two or more arrays cover all locations along a distance span along the longitudinal axis of the device.

15. The sensing device of claim 11, further comprising:

an additional array of optical sensors arranged linearly with respect to a transverse axis perpendicular to the longitudinal axis,

wherein the microcontroller is coupled to the additional array of optical sensors and configured to determine a positional offset along the transverse axis at which the additional array of optical sensors detect light.

16. The sensing device of claim 12, wherein at least one of the two or more arrays is positioned at a different depth below the plurality of slots than the other of the two or more arrays.

17. The sensing device of claim 11, wherein the two or more arrays of optical sensors include photodiodes sensitive to the wavelength of a laser reference beam.

18. The sensing device of claim 11, further comprising an accelerometer adapted to measure the tilt of the device relative to a gravity vector.

19. The sensing device of claim 11, wherein at least one of the two or more arrays comprises a single continuous optical sensor.

20. The sensing device of claim 11, wherein the two or more arrays of optical sensors comprise:

a first array of optical sensors linearly aligned along the longitudinal axis;

a second array of optical sensors linearly aligned along the longitudinal axis, the second array being adjacent to the first array and offset along the longitudinal axis relative to the first array; and

a third array of optical sensors arranged in linear alignment along the longitudinal axis, the third array being positioned adjacent to the second array and offset along the longitudinal axis relative to the second array opposite the first array.

Technical Field

The present invention relates to the measurement of structural changes including deformations of an object, and in particular to a device for measuring an offset for storage tank calibration.

Background

In the oil and gas industry, storage tanks are periodically calibrated so that their fuel capacity can be accurately determined. This is an important task because some storage tanks are extremely large and can store 2,000,000 barrels or more. A relatively small percentage of volume error for such canisters translates into a substantial error in the volume of the oil drum.

A conventional method of determining the volume of a tank is to fill the tank with fluid and then, after reaching capacity, meter it as it is emptied. This method is time consuming and expensive and the tank cannot be used when making the capacity measurement. Recently, optical sensing based measurement techniques have been applied which overcome the limitations of conventional filling and emptying methods. Commonly owned and assigned U.S. patent No. 9,188,472 ('472 patent), which is incorporated herein by reference in its entirety, describes an optical measurement system and method that is particularly suited for fuel tank calibration. However, this prior patent does not disclose details regarding the configuration of the sensor to efficiently accomplish this task, but relies on the development of this sensor by those skilled in the art. The present disclosure represents a significant improvement over the concept of the simplest sensor system that would be required by previous systems. Fig. 1 is a schematic side view of a tank calibration system according to the' 472 patent. The system 100 includes: a storage tank; a robotic device 104, such as a trolley or drone, that can be remotely controlled to move up, down, and around the circumference of the storage tank; a laser reference device 106 positioned at a known distance from the center of the storage tank; and an optical sensor 108 coupled to the robotic device. The reference point on the reservoir has a "reference circumference" with respect to which the deviation of the surface of the reservoir is determined.

In operation, the laser reference device 106 emits a vertical reference laser line 110 (the beam has a linear width in the horizontal direction) oriented parallel to the wall of the tank. As the robotic device 104 moves up and down the circumference of the tank, light from the laser reference device 106 is continuously detected by an optical sensor 108 coupled to the robotic device. Any bumps, valleys and non-uniformities on the surface of the tank will shift the position at which the optical sensor 108 captures and detects the laser radiation emitted by the laser reference device 106. The measured offset can be used to calculate the magnitude of the deformation of the surface from the reference circumference.

Since the calculation depends on an accurate reading of the position where the optical sensor 108 detects the laser light, this method depends to a considerable extent on the design of the optical sensor. While tank calibration techniques have been developed rapidly, optical sensors have not been optimized for this procedure.

There is therefore a need for an optical sensor that is particularly well suited for accurately measuring offset with respect to a longitudinal axis (e.g., a vertical line).

The disclosure herein is presented with respect to these and other considerations.

Disclosure of Invention

Embodiments of the present invention provide a sensing device for measuring an amount of deflection along a longitudinal axis. The sensing device includes: a housing including a front surface having a plurality of slots; two or more arrays of optical sensors linearly aligned along a longitudinal axis, at least one of the arrays being offset along the longitudinal axis relative to the other arrays; and a microcontroller coupled to the two or more arrays of optical sensors and configured to determine a positional offset along the longitudinal axis at which at least one of the two or more arrays of optical sensors detects light. In some embodiments, each of the two or more arrays of optical sensors is positioned within the housing below one of the plurality of slots so as to reduce an angle of incidence of radiation received by the two or more arrays of optical sensors.

In certain embodiments, at least some of the plurality of slots are angled toward the center to further reduce the angle of incidence of radiation received by the optical sensor. It is preferred that the two or more arrays of optical sensors together cover all positions along the distance span along the longitudinal axis.

In certain embodiments, the sensing device further comprises at least one filter element positioned within the housing and at least partially covering the two or more arrays of optical sensors so as to block wavelengths other than the wavelength of the laser reference beam from reaching the optical sensors.

In certain implementations, the sensing device includes an additional array of optical sensors arranged linearly with respect to a transverse axis perpendicular to the longitudinal axis, wherein the microcontroller is coupled to the additional array of optical sensors and configured to determine a positional offset along the transverse axis at which the additional array of optical sensors detect light.

At least one of the two or more arrays may be positioned at a different depth below the plurality of slots than the other of the two or more arrays. The two or more arrays of optical sensors may include photodiodes sensitive to the wavelength of the laser reference beam. In some embodiments, the sensing device further comprises an accelerometer adapted to measure the tilt of the device relative to the gravity vector. In certain embodiments, at least one of the first, second, and third arrays comprises a single continuous optical sensor.

In one embodiment, the two or more sensors include first, second and third optical arrays, wherein the second optical array is linearly offset relative to the first and third optical arrays.

Further embodiments of the present invention provide sensing devices for measuring offset along a longitudinal axis. The sensing device includes: a housing having a front surface; two or more arrays of optical sensors arranged in linear alignment along a longitudinal axis within the housing, at least one of the two or more arrays being offset along the longitudinal axis relative to the other arrays; and a microcontroller coupled to the two or more arrays of optical sensors and configured to determine a positional offset along the longitudinal axis at which at least one of the two or more arrays of optical sensors detects light.

In certain embodiments, each of the two or more arrays of optical sensors is positioned within the housing below one of the plurality of slots so as to reduce an angle of incidence of radiation received by the two or more arrays of optical sensors. At least some of the plurality of slots may be angled toward the center to further reduce an angle of incidence of radiation received by the optical sensor. It is preferred that the two or more arrays together cover all locations along the distance span along the longitudinal axis.

Some embodiments of the sensing device of the present invention include additional arrays of optical sensors arranged linearly with respect to a transverse axis perpendicular to the longitudinal axis. The microcontroller may be coupled to the additional array of optical sensors and configured to determine a positional offset along the transverse axis at which the additional array of optical sensors detects light.

In some implementations, at least one of the two or more arrays is positioned at a different depth below the plurality of slots than the other of the arrays. The two or more arrays of optical sensors may include photodiodes sensitive to the wavelength of the laser reference beam. To assist in determining orientation, the sensing device may further comprise an accelerometer adapted to measure the tilt of the device relative to the gravity vector. In further embodiments, at least one of the two or more arrays comprises a single continuous optical sensor.

In some embodiments, the two or more sensors include first, second, and third optical arrays arranged linearly along the longitudinal axis, wherein the second optical array is linearly offset relative to the first and third optical arrays.

These and other aspects, features and advantages may be understood from the following description of certain embodiments of the invention and the accompanying drawings and claims.

Drawings

Fig. 1 is a schematic side view of a tank calibration system disclosed in the prior art.

FIG. 2 is a plan view of an embodiment of a sensing device for measuring offset along a longitudinal axis according to an embodiment of the present invention.

FIG. 3 is a plan view of another embodiment of a sensing device according to an embodiment of the invention.

FIG. 4 is a longitudinal cross-sectional view of an embodiment of a sensing device according to the invention.

FIG. 5 is a longitudinal cross-sectional view of another embodiment of a sensing device according to the invention.

FIG. 6 is a plan view of an embodiment of a sensing device for measuring offset along a longitudinal axis and a lateral axis according to an embodiment of the present invention.

FIG. 7 is an engineered view illustrating an embodiment of a sensing device according to the present invention, the sensing device shown coupled to a robotic device for navigating around a structure.

FIG. 8 is a schematic block diagram of a system for measuring an offset along a longitudinal axis according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention provide a sensing device including a linear array of optical sensors adjacent to one another and offset relative to one another along a longitudinal axis. In certain embodiments, the optical sensor comprises a plurality of linear photodiode arrays or similar high resolution optical sensors. Due to the offset between adjacent linear arrays, any gaps that occur individually within a linear array are located at different levels along the longitudinal axis. Thus, there are optical sensors positioned to capture light at all longitudinal locations within the span of the sensing device (i.e., covering all gaps). The sensing device may be positioned at a fixed distance relative to the surface and travel along the surface to provide a proxy measurement of the offset of the surface relative to other measurements and/or the mechanical offset of the laser and sensing device.

Fig. 2 is a plan view of a sensing device for measuring offset along a longitudinal axis (L) according to an embodiment of the invention. The sensing device 200 comprises a substantially rectangular housing 201 in which a linear array of optical sensors 202, 204, 206 is embedded. Although three linear arrays are shown, the number of linear arrays that may be included in the sensing device is not limited to this number, and may generally include two or more linear arrays. Linear array 202 is positioned toward the left edge of the housing, linear array 204 is positioned adjacent to linear array 204 on the right, and linear array 206 is positioned adjacent to linear array 204 on the right toward the right edge of the housing. In the depicted embodiment, each of the linear arrays 202, 204, 206 includes three individual optical sensor elements arranged in series along the longitudinal axis. Thus, the linear arrays are arranged parallel to each other. The linear array 202 includes: an optical sensor element 212 initiating a first longitudinal position towards a first end of the device; an optical sensor element 214 separated from the optical sensor element along the longitudinal axis by a gap distance 215; and another optical sensor element 216, located towards the opposite end of the sensing device, separated from the sensor element 214 by a gap. Fig. 3 shows an alternative embodiment of a sensing device 300 according to the invention. This embodiment also includes three linear arrays 302, 304, 306 of optical elements. However, each linear array 302, 304, 306 includes a single continuous optical element 312, 322, 332, respectively, rather than a separate element, such as the three separate elements shown in FIG. 2. While smaller optical elements are more readily available and less expensive, longer continuous optical elements have no gaps, which may be a factor that certain embodiments may consider, as described immediately below.

The linear array 204 also includes three optical sensor elements 222, 224, 226. However, the longitudinal position of the sensor elements 222, 224, 226 is longitudinally offset relative to the sensor elements 212, 214, and 216 of the linear array 202. More specifically, optical sensor element 222 is located at an offset distance (D) relative to the edge of sensor element 212 toward the housing (higher, as depicted), sensor element 224 is located at the same offset distance (D) above sensor element 214, and sensor element 226 is located at the same offset distance above sensor element 216. It can be discerned in fig. 1 that the longitudinal span of the gap 215 between the sensor elements 212 and 214 of the linear array 202 is covered by the optical sensor 224 of the linear array 204. By offsetting the array in the manner shown, gaps between the optical sensor elements may be covered by other sensor elements of the device. It should be noted that when using continuous sensors (no gap), it is possible to use a single linear array, or two perpendicular linear arrays. However, reliance on a single array (in one or both axial directions) reduces the amount of data available (e.g., tilt and rotation data).

The linear array 206 includes optical sensor elements 232, 234, 236 positioned at the same locations longitudinally as the sensor elements 212, 214, 216. In this configuration, the linear array 206 is also offset relative to the linear array 204, and thus all adjacent linear arrays are longitudinally offset relative to each other. Any or all of the optical sensor elements may be implemented using high resolution photodiodes as known in the art. The optical sensor is preferably chosen to be sensitive to the wavelength of the laser used in the calibration system to respond preferentially to that wavelength. The multiple linear arrays provide redundancy and also provide rotational information, since rotation of the sensing device around the tank (via the robotic device) is detectable due to the lateral offset between the arrays that will result in differential readings.

Turning briefly to FIG. 7, one manner in which the sensing device 200 according to the embodiment shown in FIG. 2 may be mounted is illustrated as being mounted on a robotic vehicle 280 that may be used to make offset measurements for structure (e.g., tank) calibration. When the robotic vehicle rolls over the surface of the structure, the optical sensor elements of the sensing device detect the laser reference line at a particular pixel, which can then be converted into an offset from the reference circumference of the structure. If multiple pixels are illuminated, an averaging algorithm may be used to determine the center of the beam. This may include correction for gaps in illumination. The readings may also be mapped to a particular offset by calibration.

One or more of the optical sensor elements may be positioned in a recess that minimizes the angle of incidence of the incident radiation. In other words, the housing surface of the sensing device may contain an opening (slot), and the optical sensor element may be positioned below the surface of the device below the slot. By setting the sensor element below the surface of the device, the angle of incidence is minimized, ensuring that substantially most of the detected radiation is incident normal to the surface of the sensing device and from the laser reference device. In certain embodiments, to further reduce the likelihood of detecting stray radiation, the slot may be angled toward the center to remain narrow while still allowing detection of laser radiation. This inclination may take into account various angles of incidence of the laser light when the laser light impinges on the sensor element. For example, the tilt may be asymmetric on both sides of the slot to efficiently minimize slot size and angle of incidence, while still ensuring that the laser light can reach the sensor element at each location.

Fig. 4 is a cross-sectional view of the sensing device 200, showing a linear array 202 containing optical sensor elements 212, 214, 216 mounted within or otherwise in registration with respective slots 242, 244, 246 below the surface of the housing. The respective filter elements 252, 254, 256 are positioned above the sensor elements 212, 214, 216 so as to provide respective filtering of wavelengths that would otherwise impinge on the respective sensor elements. The filter elements 252, 254, 256 may be single-use filters, such as band gap filters that pass only a narrow band matching the wavelength of the laser light, or polarizing filters that reduce the detection of reflected and scattered light. More preferably, the filter element may combine functionality with multiple components. The optical sensor element is also preferably selected to be particularly sensitive to the wavelength of the laser light. In certain embodiments, the optical sensor elements output analog measurements of each pixel reading in order to accurately find the centroid of the array that light is illuminating. In other embodiments, the sensor element may output a digital (on/off) signal for each pixel, which still enables determination of the centroid, but with less accuracy. Additionally, the centroid reading or the reading of each pixel may be transmitted digitally.

In another embodiment of the sensing device 400 shown in fig. 5, the depth of the linear array of optical elements is non-uniform. As can be seen in this end cross-sectional view, linear array 402 is located at a depth D1 below slot 412, linear array 404 is located at a depth D2 below slot 414 that is greater than D1, and linear array 406 is located at a depth D1 below slot 416. Conventional mechanical spacers or other fixings known in the art may be used to establish the height difference between the linear arrays. The non-uniform depth of the linear array may provide information about potential misalignment between the sensing device and the laser reference device.

Other embodiments of sensing devices according to the invention include vertical and horizontal arrays of optical sensing elements. In fig. 6, which is a plan view of this embodiment, the sensing device 500 includes three vertical arrays adapted to detect an offset relative to the longitudinal axis: a first vertical array comprising optical sensor elements 502, 504, and 506, a second (middle) vertical array comprising optical sensor elements 512, 514, and 516, and a third vertical array comprising optical sensor elements 522, 524, and 526. As shown, the middle vertical array containing sensor elements 512, 514, and 516 is offset relative to the other vertical arrays. However, the vertical arrays are arranged such that adjacent arrays cover any gaps (i.e. no gaps are present in the sensing device as a whole). In addition, there is a horizontal array adapted to detect an offset relative to the lateral axis. The first horizontal array includes optical sensor elements 532, 534, and 536, and the second horizontal array includes optical sensor elements 542, 544, and 546. In addition to the vertical offset, the horizontal array also enables detection of the horizontal offset. In alternative embodiments, a two-dimensional array of optical sensing elements may be used rather than distinct and separate vertical and horizontal sensor elements.

The laser reference device 106 (fig. 1) may be adapted to utilize embodiments of sensing devices that include vertical and horizontal linear arrays of optical sensor elements. For example, rather than projecting a line-shaped beam, the laser reference device may project a cross-shaped beam (via a suitable aperture), or alternatively, may emit two laser beams together to form a T or cross. In certain embodiments where the arrays of sensor elements are closely spaced, the laser may direct a beam of light having a large diameter that can be detected simultaneously by all or several arrays, allowing the determination of an accurate centroid. The beam may in this case have a radial pattern of variable intensity to help determine the center more accurately.

Fig. 8 is a schematic diagram of a system for measuring offset in accordance with the present invention. A linear array of sensors (e.g., 202, 204, 206) detects the optical input and outputs an analog detection signal. The analog signal may be converted to a digital signal by an ADC conversion component collocated with the sensor in the sensor module, or may be transmitted directly to microcontroller 820 in analog form via a wired connection. The microcontroller 820 can drive readings of the linear arrays 202, 204, 206 of sensors. Microcontroller 820 may be implemented using one or more processors, such as a microprocessor or digital signal processor. In some embodiments, microcontroller 820 may include one or more ADC components for converting analog signals received on one or more communication ports to digital signals for further processing. 810 may also be part of a microcontroller assembly. In the depicted embodiment, the microcontroller 820 is collocated with the linear arrays 202, 204, 206 and the ADC 810 within the sensing device. However, in other embodiments, the ADC 810 is communicatively coupled to the microcontroller 820 through a wired or wireless connection based on known protocols. The microcontroller 820 is communicatively coupled to a plurality of transceivers 824a, 824b, 824c, 824d via which the microcontroller can transmit sensor data to other microcontrollers that control the robotic vehicle and communicate with the end user. In certain embodiments, the sensing device includes an accelerometer or inertial measurement unit 830 that provides additional orientation data about the sensing device to the microcontroller 820.

In operation, the microcontroller 820 receives light detection data from the linear array and determines from this data, using code executed therein, the location at which a laser beam emitted by the laser reference device is illuminating the sensing device. Since the position of the laser reference device is known, the offset to the position of the sensing device can be derived from this information. In a preferred embodiment, the microcontroller fixes the position of the laser beam using multiple measurements. This procedure provides a highly accurate relative measurement between two positions of the sensing device. The data received from the accelerometer may be used by the microcontroller 820 to again correct for movement or tilt relative to the normal direction of the surface traversed by the sensing device via the robotic vehicle, but using code executed in the processor of the microcontroller 820. Similarly, readings across multiple linear arrays may be compared by the microcontroller 820 to determine tilt or horizontal drift around a curved surface, such as a tank wall, to allow for correction of position or the data itself. Data fusion between the linear array and the accelerometer can be used to better estimate the position and orientation of the sensor elements. In some embodiments, the readings may be based on digital readings (a pulsed process) rather than absolute analog readings.

Using a calibrated device at a known distance, the alignment of the sensing device relative to the base station can be verified by measuring the width of the laser beam as it impinges on the sensing device. If it is larger than it should be, this means that there is an angular misalignment between the plane normal of the surface of the sensing device and the direction in which light is being emitted. This may be due to errors in base station alignment or by the sensing device surface being angled relative to the ground (i.e., normal to the gravity vector). The orientation of the robotic vehicle on which the sensing device is placed can be stabilized to ensure that the thinnest lines can be maintained via rotation of the sensing device relative to the structure surface, overcoming potential misalignment due to the sensing device. In other embodiments, the sensing device may be positioned on a rotating arm or shaft on the robotic device such that the orientation of the sensor relative to the robotic device may be changed by actuation. In this way, the sensing device may rotate in two degrees of freedom (roll, pitch) with respect to the vertical direction defined by the gravity vector. As mentioned, the alignment correction may be assisted by an on-board accelerometer 830. Alternatively, if the error is a misalignment from a base station, the base station may utilize this information to attempt to align itself, possibly using multiple sensors to select an alignment setting that minimizes the error proportional to the accuracy and reliability of the available inputs. The information may be communication between the sensing device and the base station through the respective on-board transceiver.

In further embodiments, two or more parallel laser beams are emitted from one or more laser reference devices. In such embodiments, offset measurements may be obtained using microcontroller 820 without having to worry about gaps in the sensor assembly. The alignment of two or more reference devices with respect to the base station can be verified by ensuring that the spread between each laser remains constant. Additionally, the distance between parallel laser lines may be used to determine the tilt of the sensor assembly, possibly in conjunction with accelerometer data. Additionally, the robotic vehicle carrying the sensing device may have a distance measuring sensor (e.g., lidar, ultrasonic, etc.) that measures the distance between the base station and the sensing device or the distance to the ground or other reference.

It is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the system and method, but are instead provided as representative embodiments and/or arrangements for teaching one skilled in the art one or more ways to practice the method.

It should be further understood that throughout the several drawings, like numerals indicate like elements, and that not all of the components and/or steps described and illustrated with reference to the drawings are required for all embodiments or arrangements.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of 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 the terms "comprises" and/or "comprising," when used in this specification, 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.

The directional terminology used herein is for the purpose of convention and reference only and is not to be construed as limiting. However, it should be recognized that these terms may be used with reference to a viewer. Therefore, no limitation is implied or inferred.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.