Patent Description:
Many agricultural harvesters include a sensor configured to sense harvested grains levels within the grain tank. For example, the sensor may be configured to emit a sensor beam, such as an ultrasonic beam, into the grain tank for reflection off of a top surface of the harvested grain stored within the grain tank. The sensor may also be configured to receive the sensor beam after reflection off of the harvested grain. In this regard, a time period between when the sensor beam is emitted by the sensor and when the reflected sensor beam is received by the sensor may be indicative of the harvested grain level within the grain tank.

In certain instances, when the current grain level within the grain tank is below a certain vertical position (e.g., the grain tank is mostly empty), the geometry of the grain tank may prevent the sensor beam from contacting the top surface of the harvested grain. In such instances, a reflective target may be positioned within the grain tank so as to reflect the sensor beam when the harvested grain is unable to do so. However, conventional reflective targets must be mounted within the grain tank at a precise orientation to reflect the sensor beam in a direction that the sensor is able to receive. Such a precise mounting orientation requires the use of time-consuming alignment and adjustment procedures during installation of the reflective target. When the reflective target is not mounted in such a precise orientation, the sensor beam is reflected in such a manner that the sensor is unable to receive the reflected sensor beam. In the US patent application published as <CIT> a reflection panel with a convex shape is used to diffuse the sensor beam as the sensor beam reflects off of the reflection panel.

An embodiment includes system for sensing harvested grain levels within an agricultural harvester according to claim <NUM>.

Another embodiment includes an agricultural harvester according to claim <NUM>.

Another embodiment includes a method for sensing harvested grain levels within an agricultural harvester according to claim <NUM>.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the claimed invention.

In general, the present subject matter is directed to systems and methods for sensing harvested grain levels within an agricultural harvester (e.g. combine). Specifically, the system includes a grain tank of the combine that is configured to receive harvested grains. In general, a current grain level within the grain tank may be defined by a top surface of the harvested grains within the grain tank. The system includes a sensor configured to emit a sensor beam into the grain tank for reflection off of the top surface of the harvested grains. The sensor is configured to receive the reflected sensor beam, which may be indicative of the current grain level within the grain tank.

Furthermore, the system includes a reflective target positioned at a minimum detectable grain level within the grain tank, with the minimum detectable grain level being defined by a minimum grain level within the grain tank at which the top surface of the harvested grain is contacted by the sensor beam. As such, the reflective target is configured to reflect the sensor beam when the current grain level is vertically below the minimum detectable grain level. The reflective target has a convex shape, where the center of the reflective target may be positioned closer to the sensor than an outer edge of the reflective target such that the reflective target diffuses the sensor beam as it reflects off of the reflective target. The diffused sensor beam may be dispersed over a greater area than sensor beams reflected off of conventional reflective targets. In this regard, the sensor may be able to receive the diffused sensor beam as reflected off of the reflective target despite a variety of orientations relative to the sensor. Specifically, the dispersed nature of the diffused sensor beam may permit the sensor to receive at least a portion of the diffused sensor beam when the sensor is mounted in each of the variety of orientations. Accordingly, it is not necessary to have a precise orientation between the sensor and the reflective target. Further details of a reflective target having a three dimensional shape such as a convex shape are found in <CIT>.

The terms "grain" and "residue" are used principally throughout this specification for convenience but it is to be understood that these terms are not intended to be limiting. "Grain" refers to that part of the grain material which is threshed and separated from the discardable part of the grain material, which is referred to as non-grain grain material, material other than grain (MOG). "Residue" refers to MOG that is to be discarded from the combine. Also the terms "fore", "aft", "left," and "right", when used in connection with the agricultural harvester (e.g. combine) and/or components thereof are usually determined with reference to the direction of forward operative travel of the combine, but again, they should not be construed as limiting.

Referring now to the drawings, and more particularly to <FIG>, there is shown one embodiment of an agricultural harvester combine <NUM>, which generally includes a harvesting implement (e.g., a header <NUM>) and an associated feeder <NUM> may extend forward of the main frame <NUM> and may be pivotally secured thereto for generally vertical movement. In general, the feeder <NUM> may be configured to serve as support structure for the header <NUM>. As shown in <FIG>, the feeder <NUM> may extend between a front end <NUM> coupled to the header <NUM> and a rear end <NUM> positioned adjacent to the threshing and separating assembly <NUM>. As is generally understood, the rear end <NUM> of the feeder <NUM> may be pivotally coupled to a portion of the combine <NUM> to allow the front end <NUM> of the feeder <NUM> and, thus, the header <NUM> to be moved upwardly and downwardly relative to the ground <NUM> to set the desired harvesting or cutting height for the header <NUM>.

As the combine <NUM> is propelled forwardly over a field with standing grain, the grain material is severed from the stubble by a sickle bar <NUM> at the front of the header <NUM> and delivered by a header auger <NUM> to the front end <NUM> of the feeder <NUM>, which supplies the harvested grain to the threshing and separating assembly <NUM>. As is generally understood, the threshing and separating assembly <NUM> may include a cylindrical chamber <NUM> in which the rotor <NUM> is rotated to thresh and separate the harvested grain received therein. That is, the harvested grain is rubbed and beaten between the rotor <NUM> and the inner surfaces of the chamber <NUM>, whereby the grain, seed, or the like, is loosened and separated from the MOG.

The harvested grain which has been separated by the threshing and separating assembly <NUM> falls onto a series of pans <NUM> and associated sieves <NUM>, with the separated harvested grain being spread out via oscillation of the pans <NUM> and/or sieves <NUM> and eventually falling through apertures defined in the sieves <NUM>. Additionally, a cleaning fan <NUM> may be positioned adjacent to one or more of the sieves <NUM> to provide an air flow through the sieves <NUM> that removes chaff and other impurities from the harvested grain. For instance, the fan <NUM> may blow the impurities off of the harvested grain for discharge from the combine <NUM> through the outlet of a straw hood <NUM> positioned at the back end of the combine <NUM>.

The cleaned harvested grain passing through the sieves <NUM> may then fall into a trough of an auger <NUM>, which may be configured to transfer the harvested grain to an elevator <NUM> for delivery to the associated grain tank <NUM>. Additionally, in one embodiment, a pair of tank augers <NUM> at the bottom of the grain tank <NUM> may be used to urge the cleaned harvested grain sideways to an unloading tube <NUM> for discharge from the combine <NUM>.

A combine controller <NUM> is also included in the combine. The combine controller may be a programmable logic controller, micro-controller, etc. The combine controller is programmable by the operator of the combine through a user (e.g. operator) interface, or through a remote computer (not shown). The operator, for example, enters commands through the user interface. In response to these commands, the controller sends control signals to the various actuators of combine <NUM>. More details of combine controller <NUM> are described with reference to <FIG>.

It should be appreciated that the configuration of the combine <NUM> described above and shown in <FIG> is provided only to place the present subject matter in an exemplary field of use. Thus, it should be appreciated that the present subject matter may be readily adaptable to any manner of combine configuration.

Referring now to <FIG>, a schematic side view of a system <NUM> for sensing harvested grain levels within an agricultural harvester, the system includes the grain tank, combine controller, sensor and reflective targets for sensing harvested grain levels within combine <NUM> in accordance with aspects of the present subject matter. As shown in <FIG>, the grain tank <NUM> of the combine <NUM> may extend in a vertical direction between a bottom end <NUM> and a top end <NUM>. The grain tank <NUM> may also extend in a longitudinal direction between a forward end <NUM> and an aft end <NUM>, with the forward end <NUM> being positioned in front of the aft end <NUM> relative to the forward direction of travel of the combine <NUM>. In addition, the bottom surface of grain tank <NUM> may include one or more walls, such as floor panels 93A/93B and auger covers 94A/94B positioned at the bottom end <NUM> of tank <NUM>, and a side walls extending vertically upward from floor panel <NUM> to the top end <NUM> of the tank <NUM>. In one embodiment, the top end <NUM> of the grain tank <NUM> may be open. Furthermore, the walls may define a grain tank <NUM> in which harvested grain is stored. However, it should be appreciated that, in alternative embodiments, the grain tank <NUM> may have any suitable configuration.

In accordance with the claimed invention, the system <NUM> includes a sensor <NUM> configured to emit one or more sensor beams and receive one or more sensor return beams (e.g., as indicated by arrows 90A/90B in <FIG>) into the grain tank <NUM> of the grain tank <NUM> depending on the position of the reflective target. For example, when targeting reflective target 92A, line 90A in <FIG> and <FIG> represents the path of an emitted beam and a reflected return beam, whereas when targeting reflective target 92B, line 90B in <FIG> and <FIG> represents the path of an emitted beam and a reflected return beam. In general, the sensor beam(s) 90A/90B is configured to be reflected off of a top surface of the harvested grain (not shown) stored in the grain tank <NUM>. Furthermore, the sensor <NUM> may further be configured to receive the reflected sensor beam(s) 90A/90B. As shown in <FIG>, in one embodiment, the sensor <NUM> may be coupled to the top edge of the side wall of the grain tank <NUM>, such as at a location at or proximate to the aft end <NUM> of the grain tank <NUM>. However, it should be appreciated that the sensor <NUM> may be mounted and/or positioned at any other suitable location in which the sensor <NUM> may emit the sensor beam(s) 90A/90B into the grain tank <NUM>. For example, <FIG> a schematic side view of a system <NUM> for sensing harvested grain levels within an agricultural harvester, the system in this embodiment shows that the sensor <NUM> may be coupled to the top edge of the side wall of the grain tank <NUM>, such as at a location at or proximate to the forward end <NUM> of the grain tank <NUM>.

Additionally, it should be appreciated that the sensor <NUM> may generally correspond to any suitable sensing device suitable configured to function as described herein, such as by emitting one or more sensor beams into the grain tank <NUM> for reflection off of the top surface of the harvested grain and by receiving or sensing the reflected sensor beams. For example, in one embodiment, the sensor <NUM> may correspond to an ultrasonic sensor(s) configured to emit one or more ultrasonic beams for reflection off of the top surface of the harvested grain.

Controller <NUM> may be configured to determine or monitor the current grain level within the grain tank <NUM> based on the sensor data received from the sensor. Specifically, controller <NUM> may be communicatively coupled to the sensor <NUM> via a wired or wireless connection to allow measurement signals to be transmitted from the sensor <NUM> to the controller. For example, in one embodiment, the measurement signals may be indicative of a time duration defined between when the sensor beam 90A/90B is emitted by the sensor <NUM> and the reflected sensor beam is received by the sensor <NUM>. As such, the controller <NUM> may then be configured determine the current grain level based on the measurement signals received from the sensor <NUM>. For instance, the controller <NUM> may include a look-up table or suitable mathematical formula stored within its memory that correlates the sensor measurements to the current grain level of the harvested grain.

In general, the minimum detectable grain level may be defined by a minimum grain level within the grain tank <NUM> at which the top surface of the harvested grain is contacted by the emitted sensor beam(s). For example, in some embodiments, the geometry of the grain tank <NUM> may prevent the emitted sensor beam(s) from contacting the top surface of the harvested grain when the top surface of the harvested grain is positioned vertically below the minimum detectable grain level. When the current grain level of the harvested grain within the grain tank <NUM> is below a minimum detectable grain level, the system relies a reflective target 92A/92B to reflect the sensor beam.

As shown in <FIG>/<FIG>, the combine includes a reflective target(s) 92A/92B positioned at the minimum detectable grain level within the grain tank <NUM>. Specifically, reflective target(s) 92A/92B may be configured to reflect and diffuse the one or more emitted sensor beams <NUM> as one or more diffused sensor beams when the current grain level is positioned vertically below the minimum detectable grain level. As shown, in <FIG>, when the sensor <NUM> is mounted to the aft end of the grain tank, the reflective target(s) 92A/92B are positioned on a surface(s) that is angled towards the aft end of the grain tank (e.g. angled towards the sensor). These surfaces may include but are not limited to grain tank floor panel 93A and grain tank auger cover 94A. In contrast, as shown in <FIG>, when the sensor <NUM> is mounted to the forward end of the grain tank, the reflective target(s) 92A/92B are positioned on a surface(s) that is angled towards the forward end of the grain tank (e.g. angled towards the sensor). These surfaces may include but are not limited to grain tank floor panel 93B and grain tank auger cover 94B. It should be appreciated that reflective target(s) 92A/92B may be positioned at any suitable location within the grain tank <NUM> such that the reflective target(s) 92A/92B may reflect the emitted sensor beam(s) when the current grain level is below the minimum detectable grain level. A reflection from one of the reflective target(s) 92A/92B indicates to the controller that the grain tank is closer to empty that it is to full.

Referring now to <FIG>, convex reflective target <NUM> may include reflecting surface <NUM> configured to reflect the emitted sensor beam(s) 90A/90B and an opposed, non-reflecting surface <NUM>. Additionally, the reflective target <NUM> may include an outer or peripheral edge <NUM> positioned outward from a center as indicated by dot <NUM>. As such, the reflecting and non-reflecting surfaces <NUM>/<NUM> may intersect at the outer edge <NUM>. Although the outer edge <NUM> is illustrated in <FIG> as defining a circular shape, it should be appreciated that the outer edge <NUM> may define any suitable shape, such as a rectangular shape. Furthermore, in one embodiment, the center <NUM> of the reflecting surface <NUM> may be configured to be positioned closer to the sensor <NUM> than the outer edge <NUM> of the reflecting surface <NUM> such that the emitted sensor beam(s) <NUM> may be diffused upon reflection off of the reflecting surface <NUM> to form the diffused sensor beam(s) <NUM>. In this regard, as shown in the illustrated embodiment, the reflective target <NUM> may define a convex shape. However, it should be appreciated that the reflective target <NUM> may have any suitable shape and/or configuration such that the center <NUM> of the reflecting surface <NUM> is positioned closer to the sensor <NUM> than the outer edge <NUM> of the reflecting surface <NUM> so as to diffuse the emitted sensor beam(s) 90A/90B.

This convex shaped reflective target produces a wider return intensity distribution as compared to a flat shaped reflective target. A comparison between the return intensity distributions of a convex shaped reflective target and a flat convex shaped reflective target is illustrated in <FIG> which shows the relationship between beam axis and the target normal. For the convex target, there is lower at peak return, but a higher average return spread over a larger angle. Thus, the convex target less dependent upon the alignment of the sensor with the target, as opposed to the flat target which requires more precise alignment of the sensor with the target so that the reflected return beam will be incident on sensor.

As indicated above, the sensor <NUM> may be configured to emit the sensor beam(s) 90A/90B into the grain tank <NUM> for reflection off of the top surface of the harvested grain. However, when the top surface of the harvested grain within the grain tank <NUM> is positioned vertically below the minimum detectable grain level, the top surface of the harvested grain may be unable to reflect the emitted sensor beam(s) 90A/90B. In such instances, the reflective target <NUM> may be configured to reflect the emitted sensor beam(s) 90A/90B for reception by the sensor <NUM>. Specifically, the reflective target <NUM> may be configured to diffuse and reflect the beam(s) 90A/90B such that the reflected, diffused sensor beam(s) are dispersed over a greater area than the reflected sensor beam(s). Accordingly, due to the dispersal of the diffused sensor beam(s), the reflective target <NUM> may be positioned in a variety of different orientations relative to the sensor <NUM> while still allowing the sensor <NUM> to receive or detect the diffused sensor beam(s).

Reflective target(s) 92A/92B should be positioned in the grain tank in manner that does not require adjustment once installed, and is not susceptible to movement (e.g. due to vibration) that could cause misalignment with sensor <NUM> over time. <FIG>, <FIG> and <FIG> show such configurations.

For example, as shown in <FIG>, reflective target <NUM> is positioned on a panel (e.g. floor panel or auger cover) of the combine grain tank <NUM>. In this example, reflective target <NUM> is not a separate component (e.g. separate piece of metal), but rather a convex portion that is embossed into panel <NUM> of grain tank <NUM>. For example, during manufacturing, the chosen panel (e.g. floor panel, auger cover or the like) is inserted into a stamping machine having a convex male die and concave female die in the shape of the desired reflective target. When the convex male die and concave female die are mated, the panel is formed to the shape of the desired reflective target. A benefit to this configuration is that reflective target <NUM> is not a separate component, but rather an integral embossed portion of the panel itself. Since the panel is metal, the embossed portion is therefore reflective and may act as a convex target for sensor <NUM>. In general, reflective target <NUM> may be embossed into any portion of the panel determined to be in relative alignment with the placement of sensor <NUM>.

In another example, as shown in <FIG>, reflective target <NUM> is also positioned on a panel (e.g. floor panel or auger cover) of the combine grain tank. However, in this example, reflective target <NUM> is a separate component (e.g. separate piece of metal) from panel <NUM>. For example, a convex target may be manufactured (e.g. stamped and cut from a piece of metal) separate from panel <NUM>. Reflective target <NUM> may then be fixed (e.g. mounted) to reflective target <NUM> via fasteners <NUM> (e.g. screws, bolts, etc.) placed around the perimeter of reflective target <NUM>. A flange <NUM> around the perimeter of reflective target <NUM> that is flush with panel <NUM> may be used for mounting purposes.

In another example, as shown in <FIG>, reflective target <NUM> is also positioned on a panel (e.g. floor panel or auger cover) of the combine grain tank. As was the case in <FIG>, reflective target <NUM> is yet again a separate component (e.g. separate piece of metal) from panel <NUM>. For example, a convex target may be manufactured (e.g. stamped and cut from a piece of metal) separate from panel <NUM>. However, in this example, reflective target <NUM> may then be fixed (e.g. mounted) to reflective target <NUM> via a welding bead around the perimeter of reflective target <NUM>.

Although the Examples above describe reflective target <NUM> as being a piece of metal, it is noted that reflective target <NUM> can be any material that is reflective. In addition, in the examples of <FIG> and <FIG> where reflective target <NUM> is a piece of metal that is separate from panel <NUM>, it is noted that the portion (not shown) of panel <NUM> located behind reflective target <NUM> may be cut out of panel <NUM> to save weight. The cutout portion (not shown) would be similar in shape to reflective target <NUM> but slightly smaller in size (e.g. smaller diameter) so as to allow for fixing of reflective target <NUM>, and to be completely covered by reflective target <NUM>.

<FIG> shows an example of a system for controlling the combine. The system includes an interconnection between a control system of combine <NUM>, a remote PC <NUM> and a remote server <NUM> through network <NUM> (e.g. Internet). It should be noted that combine <NUM> does not have to be connected to other devices through a network. The controller of combine <NUM> can be a standalone system that receives operating instructions (e.g. tank level instructions such as alert levels, shifted operating ranges, etc.) through a user interface, or through a removable memory device (e.g. Flash Drive).

Controller <NUM> may be configured to electronically control the operation of one or more components of the combine <NUM>. In general, the controller <NUM> may comprise any suitable processor-based device known in the art, such as a computing device or any suitable combination of computing devices. Thus, in several embodiments, the controller <NUM> may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions. As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) of the controller <NUM> may generally comprise memory element(s) including, but not limited to, a computer readable medium (e.g., random access memory (RAM)), a computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) <NUM> may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the controller <NUM> to perform various computer-implemented functions, such as one or more aspects of the methods described below with reference to <FIG> and <FIG>. In addition, the controller <NUM> may also include various other suitable components, such as a communications circuit or module, one or more input/output channels, a data/control bus and/or the like.

Prior to operating combine <NUM>, an operator may designate grain information such as grain tank levels. In one example, the operator uses interface <NUM> of the combine control system or PC <NUM> located at remote location <NUM>. Interface <NUM> and PC <NUM> allow the operator to view locally stored parameters from memory device <NUM> and/or download parameters from server <NUM> through network <NUM>. The operator may select (via Interface <NUM> or PC <NUM>) appropriate grain loss alert levels based on various factors including, among others, the type of grain to be harvested by the combine, and the terrain. Once the grain loss alert levels are selected, the operator can begin harvesting. Combine controller <NUM> then controls actuators <NUM> (e.g. thresher, chopper, etc.) based on the instructions. For example, grain tank level sensor <NUM> may be used during harvesting to determine grain tank level which is output to the operator. Harvesting may also be tracked and aided by GPS receiver <NUM>.

For example, the combine may be configured to provide a notification of the grain tank level of the harvested grain within the grain tank <NUM> to the operator of the combine <NUM>. In such embodiment, the controller <NUM> may be communicatively coupled to the feedback device(s) <NUM> via a wired or wireless connection to allow feedback signals to be transmitted from the controller <NUM> to the feedback device(s) <NUM>. In this regard, the feedback device(s) <NUM> may be configured to provide a visual and/or audible notification of the grain tank level to the operator of the combine <NUM> based on the feedback signals received from the controller <NUM>.

<FIG> is a flowchart for installing a three dimensional (e.g. convex) reflective target on a panel of the combine grain tank. In step <NUM>, the panel (e.g. floor panel, auger cover, etc.) is cut to size according to the grain tank specifications. In step <NUM>, the manufacturer decides on whether to stamp the panel or use another method to install the convex reflective target. If the panel is to be stamped, the panel is inserted into the press in step <NUM>, and the convex reflective target is embossed into the panel at the desired location. Then, in step <NUM>, the stamped panel is installed into the combine as usual when assembling the grain tank. However, if the panel is not to be stamped, an optional step <NUM> is performed to cut out a portion of the panel at the desired location of the convex reflective target. As mentioned above, the cutout portion should be slightly smaller than the convex reflective target. Then, in step <NUM>, a preformed convex reflective target (e.g. separate piece of metal or other reflective material) is installed on the panel at the desired location (e.g. over the cutout portion if available) using a fixing technique such as welding, gluing, screwing, bolting or the like. Then, in step <NUM>, the stamped panel is installed into the combine as usual when assembling the grain tank.

<FIG> is a flowchart for detecting grain tank level using the convex reflective target. In step <NUM>, sensor <NUM> emits a beam in the general direction of the convex reflective target in the grain tank. In step <NUM>, when the grain is vertically above the minimum detectable grain level, the beam is reflected from the grain back to sensor <NUM>. The computed grain level in step <NUM> therefore indicates the actual level of harvested grain in the tank. However, in step <NUM>, when the grain is vertically below the minimum detectable grain level, the beam is reflected from the convex reflective target to sensor <NUM>. The computed grain level in step <NUM> therefore indicates that the actual level of harvested grain in the tank is below the minimum level and cannot be determined. This measurement process may be repeated when a predetermined amount of time has passed or a trigger is received (e.g. request by the operator) in step <NUM>.

The steps including cutting the panel to size, stamping the panel with the convex target or installing the preformed convex target shown in steps <NUM>-<NUM> of <FIG>, are performed by the manufacturer during the manufacturing of the combine, by the customer after manufacturing of the combine or a combination of both. The steps including emitting the beam, receiving the reflected beam and computing the grain level shown in steps <NUM>-<NUM> of <FIG> are performed by controller <NUM> upon loading and executing software code or instructions which are tangibly stored on a tangible computer readable medium <NUM>, such as on a magnetic medium, e.g., a computer hard drive, an optical medium, e.g., an optical disc, solid-state memory, e.g., flash memory, or other storage media known in the art. Thus, any of the functionality performed by the controller <NUM> described herein, such as the steps shown in of <FIG>, are implemented in software code or instructions which are tangibly stored on a tangible computer readable medium. Upon loading and executing such software code or instructions by the controller <NUM>, the controller <NUM> may perform any of the functionality of the controller <NUM> described herein, including the steps shown in of <FIG> described herein.

It is to be understood that the operational steps are performed by the controller <NUM> upon loading and executing software code or instructions which are tangibly stored on a tangible computer readable medium, such as on a magnetic medium, e.g., a computer hard drive, an optical medium, e.g., an optical disc, solid-state memory, e.g., flash memory, or other storage media known in the art. Thus, any of the functionality performed by the controller <NUM> described herein is implemented in software code or instructions which are tangibly stored on a tangible computer readable medium. Upon loading and executing such software code or instructions by the controller <NUM>, the controller <NUM> may perform any of the functionality of the controller <NUM> described herein, including any steps of the methods described herein.

Claim 1:
A system (<NUM>, <NUM>) for sensing harvested grain levels within an agricultural harvester (<NUM>), the system (<NUM>, <NUM>) comprising:
a grain tank (<NUM>) extending vertically between a top end (<NUM>) and a bottom end (<NUM>), the grain tank (<NUM>) being configured to receive harvested grain, a current grain level of the harvested grain being defined by a top surface of the harvested grain within the grain tank (<NUM>); and
a sensor (<NUM>, <NUM>) configured to emit a sensor beam (90A, 90B) into the grain tank (<NUM>) for reflection off of the top surface of the harvested grain; and
a reflective target (92A, 92B, <NUM>, <NUM>, <NUM>), integrated into a bottom surface (93A, 93B, 94A, 94B) of the grain tank (<NUM>) at a minimum detectable grain level within the grain tank (<NUM>), the bottom surface (93A, 93B, 94A, 94B) of the grain tank (<NUM>) being angled towards the sensor (<NUM>, <NUM>), the minimum detectable grain level being defined by a minimum grain level within the grain tank (<NUM>) at which the top surface of the harvested grain is contacted by the sensor beam (90A, 90B), and the reflective target (92A, 92B, <NUM>, <NUM>, <NUM>) being configured to reflect the sensor beam (90A, 90B) when the current grain level is vertically below the minimum detectable grain level, wherein the reflective target (92A, 92B, <NUM>, <NUM>, <NUM>) has a convex shape and is stamped into a panel that defines the bottom surface (93A, 93B, 94A, 94B) of the grain tank (<NUM>).