Patent Description:
Trucks and trailers loaded with cargo, cartons and products move across the country to deliver products to commercial loading and unloading docks at stores, warehouses, and distribution centers. Trucks can have a trailer mounted on the truck, or can be of a tractorsemi trailer configuration. To lower overhead costs at retail stores, in-store product counts have been reduced, and products-in-transit now count as part of available store stock. Unloading trucks quickly at the unloading docks of warehouses and regional distribution centers has attained new prominence as a way to refill depleted stock.

Trucks are typically unloaded with forklifts if the loads are palletized and with manual labor if the products are stacked within the trucks. Unloading large truck shipments manually with human laborers can be physically difficult, and can be costly due to the time and labor involved. Consequently, a need exists for an improved unloading system that can unload bulk quantities of stacked cartons and cargo from truck trailers more quickly than human laborers and at a reduced cost.

Further, the unloaded cargos or cartons are proceeded to further steps of processing in the warehouses and distribution centers. Often, a conveyor may aid in receiving the unloaded cargos or cartons from the unloading system and move it into multiple stations in the warehouse or distribution center for further processing. Consequently, a need exists for an improved conveying system which could be used in conjunction with the unloading system for efficient unloading of cartons or cargos in an autonomous manner without any manual intervention. <CIT> discloses a robotic carton unloader having right and left lower arms of robotic arm assembly that are pivotally attached at lower end respectively to mobile body on opposing lateral sides of conveyor system passing there between. Upper arm assembly has rear end pivotally attached at upper end respectively of right and left lower arms to pivotally rotate about upper arm axis perpendicular to longitudinal axis of conveyor system and parallel to lower arm axis. Manipulator head attached to front end of upper arm assembly engages carton/s from carton pile resting on floor for movement to conveyor system. Upper arm axis is maintained at a height that enables carton/s to be conveyed by conveyor system without being impeded by robotic arm assembly as soon as manipulator head is clear. Lift attached between mobile body and front portion of conveyor system reduces spacing underneath carton/s during movement from carton pile to conveyor system. <CIT> discloses a system having a telescopic conveyor and at least one guiding element. The at least one guiding element may be fixed at a location by means of securing components. The telescopic conveyor can be moved in or counter to the conveying direction of the telescopic conveyor from a parking position into an operating position, with the telescopic conveyor being guided by the at least one guiding element, in order to allow operation of the telescopic conveyor. The telescopic conveyor can be moved in or counter to the conveying direction of the telescopic conveyor, with the telescopic conveyor being guided by the at least one guiding element, from an operating position into a parking position in order to clear a space which is occupied by the telescopic conveyor in the operating position. <CIT> discloses a nested conveyor module system with a sensor and a system to stop the conveyor when a person is detected near the system.

The following presents a simplified summary to provide a basic understanding of some aspects of the disclosed material handling system. This summary is not an extensive overview and is intended to neither identify key or critical elements nor delineate the scope of such elements. Its purpose is to present some concepts of the described features in a simplified form as a prelude to the more detailed description that is presented later.

The invention discloses a system comprising a measurement system and an extendable conveyor according to claim <NUM>.

Various example embodiments described herein relate to a measurement system, wherein the first distance is calculated based on a first time difference between transmission of the first light beam and reception of the first reflection and the second distance is calculated based on a second time difference between transmission of the second light beam and reception of the second reflection.

According to the invention, the movable portions comprise a reflector respectively, wherein the reflector reflects the first light beam and the second light beam respectively.

Various example embodiments described herein relate to a measurement system, wherein the first light beam and the second light beam have a same wavelength.

According to the invention, the conveyor is an extendable conveyor.

Various example embodiments described herein relate to a measurement system, wherein the first transceiver and the second transceiver use at least one of visible, infrared (IR) and ultraviolet (UV) light beams.

Various example embodiments described herein relate to a measurement system, wherein the conveyor is nested within the fixed portion and extendable along a same plane of the fixed portion in a horizontal axis.

Various example embodiments described herein relate to a measurement system, wherein the predefined threshold value is associated with a tolerable deviation in distances values obtained from the first sensor and the second sensor.

Various example embodiments described herein relate to a manipulation system for loading and unloading cartons from a trailer. The manipulation system of claim <NUM> comprises the system of claim <NUM>.

Various example embodiments described herein relate to a manipulation system, wherein the length of the robotic carton unloader is predefined.

Not according to the invention, an example relates to a manipulation system, wherein the safe zone is at a predefined distance from a rear end of the robotic carton unloader.

Various example embodiments described herein relate to a manipulation system, wherein the control unit is further configured to determine if the movable portion of the second conveyor is within the predefined distance.

Various example embodiments described herein relate to a manipulation system, wherein the first conveyor is a MDR conveyor and the second conveyor is an extendable conveyor.

Various examples s not according to the invention described herein relate to a method for controlling extension of an extendable conveyor. The method includes calculating a first distance between a first sensor and a reflector based on a first reflected light beam received by the first sensor and then calculating a second distance between a second sensor and the reflector based on a second reflected light beam received by the second sensor, wherein the first sensor and the second sensor are positioned on a fixed portion of the extendable conveyor and the reflector is positioned on an extendable portion of the extendable conveyor. The method further includes determining a difference value between the first distance and the second distance and stopping a movement of the extendable portion of the conveyor in response to determining that the difference value is above a predefined threshold value.

Various example embodiments not according to the invention described herein relate a method, wherein the predefined threshold value is associated with a maximum tolerable deviation in distance values obtained from the first sensor and the second sensor.

Various example embodiments not according to the invention described herein relate a method including stopping the movement of the extendable portion of the conveyor when the reflected light beams are not received by at least one of the first sensor or the second sensor.

Various example embodiments not according to the invention described herein relate a method including determining a position of the extendable portion of the extendable conveyor based on the first distance and the second distance during a movement of the extendable conveyor; determining whether the extendable portion of the conveyor is within a safe zone based on the position; and stopping a movement of the extendable portion of the conveyor in response to determining the extendable portion of the conveyor is not in the safe zone.

Various example embodiments not according to the invention described herein relate a method including periodically determining whether the extendable portion is within the safe zone and extending the extendable portion in response to determining that the difference value is below the predefined threshold value.

The above summary is provided merely for purposes of summarizing some example embodiments to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above-described embodiments are merely examples and should not be construed to narrow the scope of the disclosure which is defined in the appended claims. It will be appreciated that the scope of the disclosure encompasses many potential embodiments in addition to those here summarized, some of which will be further described below.

Some embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. Indeed, the concepts described here may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. The terms "or" and "optionally" are used herein in both the alternative and conjunctive sense, unless otherwise indicated. The terms "illustrative" and "exemplary" are used to be examples with no indication of quality level.

The components illustrated in the figures represent components that may or may not be present in various embodiments of the disclosure described herein such that embodiments may comprise fewer or more components than those shown in the figures while not departing from the scope of the disclosure.

The term "conveyor" or "conveyor zone" or "conveyor system" or "conveyor bed" may be used interchangeably throughout the specification. The term "conveyor" may refer to an "extendable conveyor" according to one or more embodiment of the present disclosure.

The term "truck unloader" or "robotic unloader" or "carton unloader" or "robotic truck unloader" may be used interchangeably throughout the specification. All these terms refer to an autonomous device capable of loading and unloading cartons, cargos, or products in a warehouse environment without manual intervention.

Turning now to the drawings, the detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description comprises specific details for the purpose of providing a thorough understanding of various concepts with like numerals denoting like components throughout the several views.

Generally, during loading and unloading operation, cartons or cargos are either directed towards a truck trailer from a warehouse or away from the truck trailer towards the warehouse. For example, during the loading operation cargos are conveyed towards the truck trailer from a particular station in the warehouse and during the unloading operation cargos are conveyed away the truck trailer towards the particular station in the warehouse for either storage or for further processing. In this regard, a conveyor, for example, an extendable conveyor may be used for conveying the cargos towards and away from the truck trailer. The extendable conveyor is often extendable up to a predefined distance based on a number of conveyor units nested within a support frame of the extendable conveyor. Generally, the extendable conveyor extends into the truck trailer either fully or partially to convey the cargos towards and away from the truck trailer based on a position of the truck trailer. In certain scenarios, the extendable conveyor extends to interface with another autonomous device inside the truck trailer. In certain scenarios, the extendable conveyor extends such that it can be operated by an operator personnel inside the truck trailer. Often, when the extendable conveyor extends, there exists a need to track an extent of the extension or distance travelled by the nested conveyor units of the extendable conveyor and a current position of the extendable conveyor to ensure that the extendable conveyor is within a safety limit. For example, if the extendable conveyor extends beyond the safety limit, there exists a possibility of collision with the truck trailer or autonomous device inside the truck trailer or with the operating personnel inside the truck trailer. Further, there also exits a need to ensure in real-time that each conveyor unit nested within the extendable conveyor is extending from the support frame without any glitch.

Various example embodiments described herein relate to a manipulation system including a measurement system which ensures that the extendable conveyor is operating within the safety limits without any glitch in the operation of the extendable conveyor. The measurement system is mounted on the extendable conveyor and includes at least two sensors with each sensor having a transceiver to transmit a first light beam and a second light beam. Both the light beams ae directed towards movable portions of the extendable conveyor. The movable portions are conveyor units nested within a fixed portion such as a support frame. The conveyor units are capable of extending towards the truck trailer. A control unit communicably coupled to the at least two sensors, wherein the control unit is configured to calculate a first distance and a second distance between the at least two sensors and the movable portions based on detecting a first reflection of the first light beam and a second reflection of the second light beam respectively. The first light beam and the second light beam are reflected from the movable portions. The control unit is further configured to determine a difference value between the first distance and the second distance and stop a movement of the unloader when the difference value is above a predefined threshold value.

According to an embodiment, the control unit is configured to calculate the first distance based on a first time-difference between transmission of the first light beam and reception of the first reflection and the second distance based on a second time-difference between transmission of the second light beam and reception of the second reflection.

According to another embodiment, the manipulation system includes a robotic carton unloader, a first conveyor, a second conveyor and a measurement system. The first conveyor configured to receive cartons thereon from the robotic carton unloader during an unloading process. The measurement system includes at least two sensors with transceivers mounted on the first conveyor. A control unit communicably coupled to the at least two sensors, wherein the control unit is configured to calculate a first distance and a second distance between the at least two sensors and the movable portions of the second conveyor.

According to yet another embodiment, the manipulation system includes a robotic carton unloader, a first conveyor, a second conveyor and a measurement system. The first conveyor configured to receive cartons thereon from the robotic carton unloader during an unloading process, wherein the first conveyor includes a senor with a transceiver and the second conveyor includes another sensor with a transceiver. Both the sensors are communicably coupled to the control unit and wherein the control unit is configured to calculate a first distance and a second distance between the at least two sensors and the movable portions of the second conveyor.

In the following detailed description of exemplary embodiments of the disclosure, specific representative embodiments in which the disclosure may be practiced are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments. For example, specific details such as specific method orders, structures, elements, and connections have been presented herein. However, it is to be understood that the specific details presented need not be utilized to practice embodiments of the present disclosure. It is also to be understood that other embodiments may be utilized and that logical, architectural, programmatic, mechanical, electrical and other changes may be made without departing from the general scope of the disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

<FIG> illustrates an embodiment of a manipulation system 100a including a robotic carton unloader 100b for unloading a container, truck trailer <NUM> and an extendable conveyor <NUM>. The robotic carton unloader may interface with a conveyor, for example, an extendable conveyor <NUM> mounted to a floor <NUM> of a warehouse. Extendable conveyor <NUM> is depicted in <FIG> as a fully powered telescopic conveyor mounted to the floor <NUM> of a loading dock, but is not limited thereto. Robotic carton unloader 100b can unload cartons <NUM> from within a store, distribution center, or warehouse, and from the container, truck, or semi-trailer. In the example as shown in <FIG>, the robotic carton unloader 100b can unload cartons <NUM> from the truck trailer <NUM>. The term "robotic" of the robotic carton unloader 100b may mean completely autonomous operation without human intervention. Robotic carton unloader 100b in embodiments may include robotic arms <NUM> (or robotic carton retrieval arms) that may be of a straddle design and include end effectors <NUM> (e.g., vacuum manipulators) for retrieving items (e.g., cartons from a carton pile), conveyor systems (e.g., a descrambling conveyor), and mobile (or vehicle) bodies. Such embodiment robotic carton unloaders 100b may be suitable for efficient and fast unloading of items (e.g., cartons, cardboard boxes, any kind of product container for conveying products, etc.) from unloading areas, such as a truck (or semi) trailer, refrigerated areas, loading docks, etc. For example, a robotic carton unloader 100b according to various embodiments may be configured to drive into a truck trailer <NUM> via its mobile body, to dislodge or remove cartons <NUM> from a carton wall or carton pile <NUM> stacked on a floor of the truck trailer <NUM> via its end effector <NUM> (e.g., manipulator head) coupled to the robotic arm <NUM>, and to transfer or unload the dislodged cartons <NUM> from the truck trailer <NUM> and into a store, warehouse, or distribution center unloading bay via its conveyor system <NUM> depicted in <FIG> that travels with the mobile body and outputs the cartons <NUM> to other conveyors, such as, the extendable conveyor <NUM>. Such embodiment robotic carton unloaders 100b may be capable of removing a substantial portion of a row of items (e.g., a carton row) that extends side-to-side across an unloading area (e.g., truck trailer <NUM>) with one removal action. For example, such robotic carton unloaders 100b may be configured to remove between about <NUM>% to about 100b% of a carton row in one movement. Designed to move within space-constrained unloading areas, such embodiment robotic carton unloaders 100b may minimize the time and effort required to efficiently unload and provide basic organization for items being moved for subsequent processing within facilities, such as distribution centers.

The robotic carton unloader 100b includes a control unit or (control and visualization system) including a processor and attached to the robotic carton unloader 100b for autonomous robotic control of robotic carton unloader 100b. The control unit <NUM> can control the unloading process without human intervention. The control unit <NUM> may visualize or sense the surroundings, may use the sensing to perform computations to identify and select cartons <NUM> for removal. The control unit <NUM> can constantly re-sense and re-compute all autonomous actions necessary to unload an entire truck trailer <NUM> from rear to front. The control unit <NUM> may include various visualization sensors (e.g., cameras, etc.), operator interfaces (e.g., joysticks, pendants, displays, keypads, etc.), and processors, and may be capable of controlling and automating the unloading process, and driving and steering the robotic carton unloader 100b into and out of unloading areas (e.g., truck trailers <NUM>) before, during, and after the unloading process. The control unit <NUM> can be used to compute the location of the wall of carton piles <NUM> relative to robotic carton unloader 100b and the end effector <NUM> and can autonomously control and move the robotic arm <NUM> to unload of cartons <NUM> from the carton pile <NUM> and place the unloaded cartons <NUM> onto the conveyor system <NUM> for conveyance onto the extendable conveyor <NUM>. The control unit <NUM> may also include a memory which stores predefined values such as, but not limited to, length of the robotic carton unloader 100b, length of the extendable conveyor <NUM> when fully extended or fully retracted, number of conveyor units nested within a support frame or a fixed portion of the extendable conveyor <NUM>, a position of the fixed portion or support frame of the extendable conveyor <NUM>, a safety zone defined relative to inner walls or outer walls of the truck trailer <NUM>, a safety zone defined relative to rear end of the robotic carton unloader 100b.

By way of example, the robotic carton unloader 100b may, under the control of the control unit <NUM>, operate without any human intervention as it moves from the warehouse, through a loading door, into the struck trailer <NUM>, unloads the cartons <NUM> within entire truck trailer <NUM> from rear to front, and then exit from the truck trailer <NUM> back into the warehouse to access another truck trailer at the same or a different location. The control unit <NUM> can at least visualize or sense the warehouse, the loading door, the interior of the truck trailer <NUM>, a carton wall or carton pile <NUM> stacked on floor of the truck trailer <NUM>, and individual cartons <NUM> of all sizes and shapes thereof, and can autonomously compute all movements necessary to move and steer the robotic carton unloader 100b during the unloading process.

The robotic carton unloader 100b and the extendable conveyor <NUM> may include measurement systems, for example, a first measurement system <NUM> and a second measurement system <NUM>. Each of the measurement systems <NUM>, <NUM> may include at least one sensor to detect, for example, a position information of the extendable conveyor <NUM>. The second measurement system <NUM> on the robotic carton unloader 100b may be communicably connected to the first measurement system <NUM> on the extendable conveyor <NUM>. As shown in <FIG>, the robotic carton unloader 100b includes a conveyor system <NUM> configured to receive the cartons <NUM> thereon from the robotic carton unloader 100b during an unloading process. The second measurement system <NUM> may be positioned on the conveyor system <NUM>. According to an embodiment, the manipulation system 100a may include only one measurement system, for example, a first measurement system <NUM> positioned on the extendable conveyor <NUM> to detect the position information of the extendable conveyor <NUM> as shown in <FIG>. Both the measurement systems <NUM>, <NUM> may be communicably coupled to the control unit <NUM>. Communication between the robotic carton unloader 100b and the extendable conveyor <NUM> can be through a communications link such as, but not limited to, a wireless system, laser, infrared, visible light, or an Ethernet cable. An example of a communications link can be seen in <FIG> with an unloader wireless unit <NUM> on robotic carton unloader and an extendable wireless link <NUM> on the extendable conveyor <NUM>, for example, a cable such as an Ethernet cable may link the control unit <NUM> to the extendable conveyor <NUM> to send extension and retraction commands thereto.

The control unit <NUM> may use the position information of the extendable conveyor <NUM> to extend or retract the extendable conveyor <NUM> and may calculate and control extension and retraction movements of the extendable conveyor <NUM> to move in unison with the forward and reverse movements of the robotic carton unloader 100b. The control unit <NUM> may interface the extendable conveyor <NUM> to the robotic carton unloader 100b to receive unloaded cartons onto the extendable conveyor <NUM>, and control unit <NUM> may continually maintain this carton receiving relationship to provide a continuous flow of cartons <NUM> from the robotic carton unloader 100b onto extendable conveyor <NUM> throughout the unloading of the truck trailer <NUM>. The control unit <NUM> can maintain this carton <NUM> receiving relationship relative to the robotic carton unloader 100b during the unloading process by calculating and communicating extension and retraction movements of the extendable conveyor <NUM>.

In embodiments, the electrical and software functions of the measurement systems <NUM>, <NUM> on the extendable conveyor <NUM> and the robotic carton unloader 100b may be included as part of the control unit <NUM> on the robotic carton unloader 100b of <FIG>and <FIG>. Control unit <NUM> can use the position information from the measurement systems <NUM>, <NUM> to either control forward and reverse motion of the robotic carton unloader 100b or communicate extension and retraction commands to the extendable conveyor <NUM>. If desired, portions of the control unit 111can be split to be partially on the robotic carton unloader 100b and the electrical hardware and software functions of the measurement systems <NUM>, <NUM> can be split between the control unit <NUM> and extendable conveyor <NUM>. Each portion can be slaved to the control unit <NUM> on the robotic carton unloader 100b. In embodiments, either or both of the robotic carton unloader 100b and the extendable conveyor <NUM> may be configured to be operated by a human operator, and then may be re-configured back to autonomous operation.

The automated features of the manipulation system 100a in unison with the robotic carton unloader 100b operate without human intervention, and can ensure that the extendable conveyor <NUM> and the robotic carton unloader 100b provide a continuous unbroken conveying path between the robotic carton unloader 100b and the extendable conveyor <NUM>.

Embodiments of robotic carton unloader 100b can include embodiments described in co-pending parent <CIT>. The measurement systems <NUM>, <NUM> described in detail below in conjunction with <FIG> is not limited to use with the robotic carton unloader <NUM> and could be adapted for use with other robotic carton unloaders.

<FIG> illustrates a top view of the conveyor of <FIG> with a measurement system, in accordance with an embodiment of the present disclosure. The measurement system <NUM> is mounted on the conveyor <NUM>. The conveyor <NUM> shown in <FIG> is an extendable conveyor <NUM> as shown in <FIG> with a fixed portion <NUM> and movable portions <NUM>. The fixed portion <NUM> and the movable portions <NUM> are conveyor units. In some examples, the fixed portion <NUM> may be a support frame. The conveyor units, for example, may be roller conveyor units or belt conveyor units. In <FIG>, three movable portions 114a, 114b, and 114c, for example, three nested conveyor units are shown in a fully extend position. The three movable portions 114a, 114b, and 114c may be supported by the fixed portion <NUM> in a cantilever manner. According to an embodiment, a length of each of the movable portions <NUM> may be same. According to another embodiment, the length of each of the movable portions <NUM> may be varying. According to an embodiment, the measurement system <NUM> is mounted on the fixed portion <NUM> or the support frame of the extendable conveyor <NUM>. In some examples, the measurement system <NUM> may be positioned at a known distance from either a rear end or a front end of the fixed portion <NUM>.

According to an embodiment, the measurement system <NUM> includes a first sensor <NUM> with a first transceiver and a second sensor <NUM> with a second transceiver mounted on a fixed portion <NUM> of the conveyor <NUM>. The first transceiver and the second transceiver respectively transmit a first light beam and a second light beam towards a movable portion <NUM> of the conveyor <NUM>. The first sensor <NUM> and the second sensor <NUM> may be optic sensors, for example, laser sensors. For example, the first light beam and the second light beam may be laser beams directed towards the movable portion <NUM>, for example, nested conveyor units. The laser beams are directed when the movable portions <NUM> (i.e. the nested conveyor units) of the extendable conveyor <NUM> are in motion. For example, the laser beams are directed when the movable portions <NUM> are extending from the fixed portion <NUM> towards a rear of the robotic carton unloader <NUM> to interface with the conveyor system <NUM>.

According to an embodiment, the first sensor <NUM> and the second sensor <NUM> are mounted on cross- member support beam <NUM> positioned on the fixed portion <NUM>. The cross-member support beam <NUM> includes two poles <NUM>, <NUM> positioned opposite to each other with the first sensor <NUM> attached to a first pole <NUM> and the second sensor <NUM> attached to a second pole <NUM>. According to an embodiment, the first sensor <NUM> and the second sensor <NUM> may be positioned at the same height in the first pole <NUM> and the second pole <NUM>. According to another embodiment, the first sensor <NUM> and the second sensor <NUM> may be attached to either the first pole <NUM> or the second pole <NUM> and positioned at either the same height or different height.

According to an embodiment, the first light beam and the second light beam directed from the first sensor <NUM> and the second sensor <NUM> are reflected back from the movable portions <NUM> of the conveyor <NUM> to the first sensor <NUM> and the second sensor <NUM>. The first sensor <NUM> and the second sensor <NUM> receives the first reflection and the second reflection from the movable portions <NUM> of the conveyor <NUM>.

According to an embodiment, the first light beam and the second light beam directed from the first sensor <NUM> and the second sensor <NUM> are reflected back from reflectors <NUM> positioned on the movable portions <NUM> of the conveyor <NUM>. In some examples, the reflectors <NUM> are positioned on each of the movable portions 114a, 114b, and 114c (i.e., each of the nested conveyor units). In some examples, only one reflector <NUM> is positioned on one of the nested unit, for example, a first nested conveyor unit 114a or a third nested conveyor unit 114c. In other embodiments, the reflectors <NUM> may be positioned at a front end of each of the nested conveyor units <NUM>. According to an embodiment, one or more reflectors <NUM> may be attached to each nested conveyor units <NUM>. In <FIG>, each of the nested conveyor units <NUM> may include at least two reflectors <NUM>. The first sensor <NUM> and the second sensor <NUM> receives the first reflection and the second reflection from the reflectors <NUM> mounted on the movable portions <NUM> of the conveyor <NUM>. In some examples, the reflector <NUM> may be a retroreflector. For example, the transceiver of the first sensor <NUM> and the second sensor <NUM> receives the first reflection and the second reflection from one of the reflectors <NUM> and uses the electric circuit arrangement which converts the reflections into an electric signal.

According to an embodiment, one of the reflector <NUM> reflects the light beams when the movable portions <NUM> of the conveyor <NUM> is in motion. For example, the sensors <NUM>, <NUM> on the fixed portion <NUM> emit the light beams and the reflector <NUM> of the first nested conveyor unit 114a may reflect the emitted light beams back to the sensors <NUM>, <NUM> while the nested conveyor units <NUM> extend in a direction "X" in a horizontal axis from the fixed portion <NUM> of the conveyor <NUM> along a same plane of the fixed portion <NUM>. The reflected light beams are converted into electric signals which is then processed by the control unit <NUM> to determine a distance between the movable portions <NUM> of the conveyor <NUM> and the sensors <NUM>, <NUM>. For example, the control unit <NUM> calculates a first distance between the first sensor <NUM> and the first nested conveyor unit 114a based on the first sensor <NUM> detecting a first reflection of the first light beam from the first nested conveyor unit 114a of the conveyor <NUM> while it is moving. Further, the control unit <NUM> calculates a second distance between the second sensor <NUM> and the first nested conveyor unit 114a based on the second sensor <NUM> detecting a second reflection of the second light beam from the first nested conveyor unit 114a of the conveyor <NUM> while it is moving. The first distance can be calculated based on a first time difference between transmission of the first light beam and reception of the first reflection and the second distance is calculated based on a second time difference between transmission of the second light beam and reception of the second reflection. According to an embodiment, the first distance is calculated based on the first time difference and velocity of the light beam; and the second distance is calculated based on the second time difference and the velocity of the light beam. In other embodiments, other determinations for the distances can be used. The total distance travelled by the nested conveyor units <NUM> is calculated by multiplying the distance of the first nested conveyor unit 114a from the fixed portion <NUM> with number of nested conveying units <NUM>, which in the example embodiment of <FIG> is three. In some examples, when the third nested conveyor unit 114c includes the reflector <NUM>, the total distance travelled by the extendable conveyor <NUM> is the actual distance of the third conveyor unit 114c from the fixed portion <NUM> calculated by the control unit <NUM>.

According to an embodiment, the first distance and the second distance may be calculated by use of both the first measurement system <NUM> and the second measurement system <NUM> as shown in <FIG>. For example, the second measurement system <NUM> positioned on the conveyor system <NUM> of the robotic unloader 100b may include a sensor with a first transceiver mounted to emit a light beam of a first wavelength and the first measurement system <NUM> positioned on the extendable conveyor <NUM> may include another sensor with a second transceiver to emit a light beam of a second wavelength. The light beams of the first wavelength and the second wavelength are reflected back by the reflectors <NUM> mounted on the movable portions <NUM> of the extendable conveyor <NUM>. In some examples, the sensors may direct the light beams to the reflector <NUM> on the third nested conveyor unit 114c. The control unit <NUM> which is communicably coupled to the first measurement system <NUM> and the second measurement system <NUM> receives the reflected light beams from the reflector <NUM> and calculates the first distance and the second distance.

According to an embodiment, the first distance and the second distance obtained from the first measurement system <NUM> and the second measurement system <NUM> may be used in identifying the position of the unloader 100b relative to the position of the fixed portion <NUM> of the extendable conveyor <NUM>. The first distance may be indicative of the extent of extension of the extendable conveyor <NUM> at any given point of time. The second distance may be indicative of the gap between the end of the extendable conveyor 202b and the unloader 100b. Using the first distance and the second distance, the control unit <NUM> calculates the position of the unloader 100b relative to the position of the fixed portion <NUM> of the extendable conveyor <NUM>. Using this distance and known length of the robotic carton unloader 100b predefined in the memory of the control unit <NUM>, the control unit <NUM> computes a position of the nose portion of the unloader 100b relative to the position of the fixed portion <NUM> of the extendable conveyor <NUM>. In some examples, the position is determined to ensure that the nose portion unloader 100b is within a safe zone. In some examples, the safe zone may be predefined and stored in the memory of the control unit <NUM>. In some examples, the safe zone may be defined in the memory using Cartesian coordinates. The position of the nose portion unloader 100b may be compared to the safe zone and movement of the unloader 100b or further extension of the nose portion 110b of the extendable conveyor <NUM> is stopped when the unloader 100b is not within the safe zone.

According to the invention, a difference value between the first distance and the second distance is calculated by the control unit <NUM>. The difference value is then compared to a predefined threshold value. If the difference value is greater than the predefined threshold value, then the movement of the extendable conveyor <NUM> is stopped. In some example, the predefined threshold value is associated with a maximum tolerable deviation in distance values obtained from the first sensor <NUM> and the second sensor <NUM>. This ensures that the extendable conveyor <NUM> is not extended beyond a certain threshold level in order to ensure safety when interfacing the extendable conveyor <NUM> with the conveyor system <NUM> of the robotic carton unloader 100b.

According to another embodiment, measured distance values are used to determine the location of the unloader. If position is outside of predetermined bounds the controller will stop the unloader. Stopping the unloader will subsequently stop the extendable. The distance data may not be used to directly control the extendable conveyor in some embodiments, but may control the extendable conveyor in other embodiments.

<FIG> illustrates a perspective view of a first measurement system mounted on the conveyor of <FIG>, in accordance with the invention. In <FIG>, the first measurement system <NUM> is mounted to one of the poles <NUM>, <NUM> of the cross-member support <NUM> of the extendable conveyor <NUM> shown in <FIG>. For example, the first measurement system <NUM> which includes the first sensor <NUM> and the second sensor <NUM> are positioned on one pole <NUM> of the cross-member support <NUM> in a sequential manner (i.e.,) the second sensor <NUM> is positioned below the first sensor <NUM>. According to another embodiment, the first sensor <NUM> and the second sensor <NUM> may be installed on one pole <NUM> in a parallel manner (i.e.,) a first sensor <NUM> on a first side 132a of the pole <NUM> and the second sensor <NUM> on a second side 132b (not shown) opposite to the first side 132a. Both these sensors <NUM>, <NUM> emit light beams of either a same wavelength or different wavelength. According to an embodiment, the construction and structure of the first sensor <NUM> and the second sensor <NUM> may not be identical. Both the sensors <NUM>, <NUM> are oriented in a manner to receive reflected light beams from the reflectors <NUM> mounted in each nested conveyor unit <NUM> of the extendable conveyor <NUM> According to the invention, the first sensor <NUM> may be oriented to receive reflections from the first reflector 202a positioned on a first nested conveyor unit 114a and the second sensor <NUM> may be oriented to receive reflections from the second reflector 202b positioned on a second nested conveyor unit 114b. The reflections are analyzed by the control unit <NUM> communicably coupled to the first sensor <NUM> and the second senor <NUM> to obtain a distance travelled by the movable portions <NUM> of the extendable conveyor <NUM>. For example, the distance travelled by the first nested conveyor unit 114a and the second nested conveyor unit 114b may be summed up to obtain a total distance traveled by the extendable conveyor <NUM>.

<FIG> illustrates a perspective view of a second measurement system mounted on the robotic unloader of <FIG>, in accordance with an embodiment of the present disclosure. In <FIG>, the second measurement system <NUM> is mounted to a cross-member support <NUM> on the conveyor system <NUM> of the robotic carton unloader 100b. The conveyor system <NUM> may be a gravity roller conveyor. The second measurement system <NUM> includes two sensors, for example, a third sensor <NUM> and a fourth sensor <NUM>. Both these sensors <NUM>, <NUM> emit light beams of either a same wavelength or different wavelength. Both the sensors <NUM>, <NUM> are oriented in a manner to receive reflected light beams from the reflectors <NUM> mounted on the nose portion 110a of the extendable conveyor <NUM>. The reflections from the reflector <NUM> on the nose portion 110a are analyzed by the control unit <NUM> communicably coupled to the third sensor <NUM> and the fourth sensor <NUM> measure a gap between the extendable conveyor and the robotic truck unloader. According to an embodiment, a position of the nose portion 110a of the extendable conveyor <NUM> is identified based on the distance travelled, a known position of the fixed portion <NUM> of the extendable conveyor <NUM>, and the known length of the robotic truck unloader 100b.

According to an embodiment, the construction and structure of the third sensor <NUM> and the fourth sensor <NUM> may not be identical. According to an embodiment, the construction and structure of the first sensor <NUM>, the second sensor <NUM>, the third sensor <NUM> and the fourth sensor <NUM> may be identical. According to another embodiment, the construction and structure of the first sensor <NUM> and the second sensor <NUM> may be identical; and the third sensor <NUM> and the fourth sensor <NUM> may be identical but different from the construction of the first sensor <NUM> and the second sensor <NUM>. According to an embodiment, the first measurement system <NUM> can determine a distance that of an extended extendable conveyor <NUM> and second measurement system <NUM> can measure a gap between the end of extendable conveyor 110b and the unloader 100b. According to an embodiment, the second measurement system <NUM> and the first measurement system <NUM> may be used in conjunction to accurately determine the position of the unloader 100b.

<FIG> illustrates a method of operating the conveyor using the measurement systems of <FIG> and <FIG>, in accordance with an embodiment of the present disclosure. The measurement system on both the extendable conveyor and the conveyor of the robotic truck unloader are communicably coupled to the control unit of the robotic ruck unloader. Using the input signals in the form of electric signals indicative of light reflections on the sensors, the control unit, at step <NUM> and <NUM>, calculates a first distance and a second distance between the sensors and reflectors. The first sensor and the second sensor are positioned on a fixed portion of the extendable conveyor and the reflector is positioned on an extendable portion of the extendable conveyor. At step <NUM>, the control unit determines a difference value between the first distance and the second distance; and at step <NUM>, the control unit stops a movement of the extendable portion of the extendable conveyor in response to determining that the difference value is above a predefined threshold value. The predefined threshold value is a maximum tolerable deviation in distance values obtained from the first sensor and the second sensor. In some examples, the control unit stops the movement of the unloader and extendable conveyor when either the first sensor or the second sensor does not receive the corresponding reflections from the reflector. Further, at step <NUM>, the control unit determines a position of the unloader based on the first distance and the second distance during a movement of the extendable conveyor. The position of the unloader may be derived based on the known length of the robotic truck unloader, a known position of the fixed portion of the extendable conveyor, and the distance the extendable conveyor is extended. Further, at step <NUM>, the control unit determines whether the unloader is within a safe zone based on the position. The safe zone, for example, may be defined in the form of Cartesian coordinates. Further, at step <NUM>, the control unit stops a movement of the unloader in response to determining that the unloader is not in the safe zone. When the position of the unloader is within the safe zone, then the control unit may move the unloader and extend the extendable portion. In this manner, the control unit periodically determines whether the unloader is within the safe zone and moves the unloader and extends the extendable portion in response to determining that the difference value in the calculated distance is below the predefined threshold value.

<FIG> illustrates an exemplary computing environment for an onboard unloading control unit of the robotic unloader of <FIG>, in accordance with an embodiment of the present disclosure. Depending on embodiments listed above, each of the control unit <NUM> of the robotic carton unloader 100b may comprise all or some of an external monitor <NUM>, a network interface module <NUM>, an HMImodule <NUM>, an input/output module (I/O module <NUM>), an actuators/distance sensors module <NUM>, a robotic arm <NUM> and a conveyor system <NUM> that includes a drives/safety module <NUM> and a motion module <NUM>, a programmable logic controller (or PLC <NUM>, and a vision system <NUM> (or visualization system) that may include one or more computing devices 616a (or "PCs") and sensor devices 616b. In some embodiments, vision system <NUM> of the robotic carton unloader 100b may include a PC 616a connected to each sensor device 616b. In embodiments in which more than one sensor device 616b is present on the robotic carton unloader 100b, the PCs 616a for each sensor device 616b may be networked together and one of the PC's 616a may operate as a master PC 616a receiving data from the other connected PC's 616a, may perform data processing on the received data and its own data (e.g., coordinate transformation, duplicate elimination, error checking, etc.), and may output the combined and processed data from all the PCs 616a to the PLC <NUM>. In some embodiments, the network Interface module <NUM> may not have a PLC inline between it and the PC 616a, and the PLC <NUM> may serve as the Vehicle Controller and/or Drives/Safety system.

The robotic carton unloader 100b may connect to remote locations or systems with a network interface module <NUM> (e.g., a Wi-Fi™ radio, etc.) via a network <NUM>, such as a local area Wi-Fi™ network. In particular, the network interface module <NUM> may enable the robotic carton unloader 100b to connect to an external monitor <NUM>. The external monitor <NUM> may be anyone of a remote warehouse or distribution center control room, a handheld controller, or a computer, and may provide passive remote viewing through the vision system <NUM> of the robotic carton unloader 100b. Programming for the robotic carton unloader 100b may also be communicated, operated and debugged through external systems, such as the external monitor <NUM>. Examples of an external monitor <NUM> that assumes command and control may include a remotely located human operator or a remote system, such as a warehouse or distribution server system (i.e., remote device as described above). Exemplary embodiments of using an external monitor <NUM> to assume command and control of the robotic carton unloader 100b may include human or computer intervention in moving the robotic carton unloader 100b, such as from one unloading bay to another, or having the external monitor <NUM> assume control of the robotic arm <NUM> to remove an item (e.g., box, carton, etc.) that is difficult to unload with autonomous routines. The external monitor <NUM> may include any of: a visual monitor, a keyboard, a joystick, an I/O port, a CD reader, a computer, a server, a handheld programming device, or any other device that may be used to perform any part of the above described embodiments.

The robotic carton unloader 100b may include a human machine interface module <NUM> (or HMI module <NUM>) that may be used to control and/or receive output information for the robot arm and conveyor system <NUM> and/or the base motion module <NUM>. The HMI module 612may be used to control (or may itself include) a display, and a keypad that may be used for, over-riding the autonomous control of the machine, and driving the robotic carton unloader 100b from point to point. The actuators <NUM> that may be actuated individually or in any combination by the vision system <NUM> and the distance sensors may be used to assist in guiding the robotic carton unloader 100b into an unloaded area (e.g., a trailer). The I/O module <NUM> may connect the actuators and distance sensors <NUM> to the PLC <NUM>. The robotic arm <NUM> and conveyor system <NUM> may include all components needed to move the arm and/or the conveyor, such as drives/engines and motion protocols or controls.

The PLC <NUM> that may control the overall electromechanical movements of the robotic carton unloader 100b or control exemplary functions, such as controlling the robotic arm <NUM> or a conveyor system <NUM>. For example, the PLC <NUM> may move the manipulator head of the robotic arm <NUM> into position for obtaining items (e.g., boxes, cartons, etc.) from a wall of items. As another example, the PLC <NUM> may control the activation, speed, and direction of rotation of kick rollers, and/or various adjustments of a support mechanism configured to move a front-end shelf conveyor (e.g., front-end shelf conveyor). The PLC <NUM> and other electronic elements of the vision system <NUM> may mount in an electronics box (not shown) located under a conveyor, adjacent to a conveyor, or elsewhere on the robotic carton unloader 100b. The PLC <NUM> may operate all or part of the robotic carton unloader 100bautonomously and may receive positional information from the distance sensors <NUM>. The I/O module <NUM> may connect the actuators and the distance sensors <NUM> to the PLC <NUM>.

The robotic carton unloader 100b may include a vision system <NUM> that comprises sensor devices 616b (e.g., cameras, 3D sensors, etc.) and one or more computing device 616a (referred to as a personal computer or "PC" 616a). The robotic carton unloader 100b may use the sensor devices 616b and the one or more PC 616a of the vision system <NUM> to scan in front of the robotic carton unloader 100b in real time or near real time. The forward scanning may be triggered by the PLC <NUM> in response to determining the robotic carton unloader 100b, such as a trigger sent in response to the robotic carton unloader 100b being in position to begin detecting cartons in an unloading area. The forward scanning capabilities may be used for collision avoidance, sizing unloaded area (e.g., the truck or trailer), and for scanning the floor of the unloaded area for loose items (e.g., cartons, boxes, etc.). The 3D capabilities of the vision system <NUM> may also provide depth perception, edge recognition, and may create a 3D image of a wall of items (or carton pile). The vision system <NUM> may operate alone or in concert with the PLC <NUM> to recognize edges, shapes, and the near/far distances of articles in front of the robotic carton unloader 100b. For example, the edges and distances of each separate carton in the wall of items may be measured and calculated relative to the robotic carton unloader 100b, and vision system <NUM> may operate alone or in concert with the PLC <NUM> to may select specific cartons for removal.

In some embodiments, the vision system <NUM> may provide the PLC with information such as: specific XYZ coordinate locations of cartons targeted for removal from the unloading area, and one or more movement paths for the robotic arm <NUM> or the mobile body of the robotic carton unloader 100b to travel. The PLC <NUM> and the vision system <NUM> may work independently or together such as an iterative move and visual check process for carton visualization, initial homing, and motion accuracy checks. The same process may be used during vehicle movement, or during carton removal as an accuracy check. Alternatively, the PLC <NUM> may use the move and visualize process as a check to see whether one or more cartons have fallen from the carton pile or repositioned since the last visual check. In alternate embodiments, the described computing devices and/or processors may be combined and the operations described herein performed by separate computing devices and/or processors may be performed by less computing devices and/or processors, such as a single computing device or processor with different modules performing the operations described herein. As examples, different processors combined on a single circuit board may perform the operations described herein attributed to different computing devices and/or processors, a single processor running multiple threads/modules may perform operations described herein attributed to different computing devices and/or processors, etc..

An extendable conveyor system <NUM> can convey articles from the robotic carton unloader 100b to other portions of a material handling system. As the robotic carton unloader 100b advances or retreats, any one of the measurement system <NUM> or <NUM> on the robotic carton unloader 100b or the extendable conveyor can potentially be used to locate the extendable conveyor <NUM>. Wireless interfaces <NUM> and <NUM> respectively of the robotic carton unloader 100b and the extendable conveyor <NUM> can convey angular, position and distance information or movement commands. For example, PLC <NUM> can command an extension motion actuator on the extendable conveyor <NUM> to correspond to movements of the robotic carton unloader 100b to keep the extendable conveyor system <NUM> and the robotic carton unloader 100b in alignment and in proper spacing. In one embodiment, the wireless interfaces <NUM> and <NUM> utilize a short range wireless communication protocol such as a.

As used herein, processors may be any programmable microprocessor, microcomputer or multiple processor chip or chips that can be configured by software instructions (applications) to perform a variety of functions, including the functions of the various embodiments described above. In the various devices, multiple processors may be provided, such as one processor dedicated to wireless communication functions and one processor dedicated to running other applications. Typically, software applications may be stored in the internal memory before they are accessed and loaded into the processors. The processors may include internal memory sufficient to store the application software instructions. In many devices the internal memory may be a volatile or nonvolatile memory, such as flash memory, or a mixture of both. For the purposes of this description, a general reference to memory refers to memory accessible by the processors including internal memory or removable memory plugged into the various devices and memory within the processors.

The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a non-transitory processor-readable, computer-readable, or server-readable medium or a non-transitory processor-readable storage medium. The steps of a method or algorithm disclosed herein may be embodied in a processor-executable software module or processor-executable software instructions which may reside on a non-transitory computer-readable storage medium, a non-transitory server-readable storage medium, and/or a non-transitory processor-readable storage medium. In various embodiments, such instructions may be stored processor-executable instructions or stored processor-executable software instructions. Tangible, non-transitory computer-readable storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such non-transitory computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray™ disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of non-transitory computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a tangible, non-transitory processor-readable storage medium and/or computer-readable medium, which may be incorporated into a computer program product.

While the disclosure 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 disclosure. In addition, many modifications may be made to adapt a particular system, device or component thereof to the teachings of the disclosure without departing from the scope which is defined in the appended claims.

Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

For clarity, the robotic carton unloader 100b (<FIG>) is described herein as unloading cartons, which can be corrugated boxes, wooden crates, polymer or resin totes, storage containers, etc. The manipulator head can further engage articles that are products that are shrink-wrapped together or a unitary product. In one or more embodiments, aspects of the present innovation can be extended to other types of manipulator heads that are particularly suited to certain types of containers or products. The manipulator head can employ mechanical gripping devices, electrostatic adhesive surfaces, electromagnetic attraction, etc. Aspects of the present innovation can also be employed on a single conventional articulated arm.

It will he 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 description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the disclosure. The described embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.

It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a "colorant agent" includes two or more such agents.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although a number of methods and materials similar or equivalent to those described herein can be used in the practice of the present invention, the preferred materials and methods are described herein.

References within the specification to "one embodiment," "an embodiment," "embodiments", or "one or more embodiments" are intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The appearance of such phrases in various places within the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

It is understood that the use of specific component, device and/or parameter names and/or corresponding acronyms thereof, such as those of the executing utility, logic, and/or firmware described herein, are for example only and not meant to imply any limitations on the described embodiments. The embodiments may thus be described with different nomenclature and/or terminology utilized to describe the components, devices, parameters, methods and/or functions herein, without limitation. References to any specific protocol or proprietary name in describing one or more elements, features or concepts of the embodiments are provided solely as examples of one implementation, and such references do not limit the extension of the claimed embodiments to embodiments in which different element, feature, protocol, or concept names are utilized. Thus, each term utilized herein is to be given its broadest interpretation given the context in which that terms is utilized.

As will be appreciated by one having ordinary skill in the art, the methods and compositions of the invention substantially reduce or eliminate the disadvantages and drawbacks associated with prior art methods and compositions.

It should be noted that, when employed in the present disclosure, the terms "comprises," "comprising," and other derivatives from the root term "comprise" are intended to be open-ended terms that specify the presence of any stated features, elements, integers, steps, or components, and are not intended to preclude the presence or addition of one or more other features, elements, integers, steps, components, or groups thereof.

Claim 1:
A system comprising an extendable conveyor (<NUM>) having a fixed portion (<NUM>) and movable portions (<NUM>), and a measurement system (<NUM>,<NUM>);
the measurement system (<NUM>, <NUM>) comprising a first sensor (<NUM>), a second sensor (<NUM>), and a control unit (<NUM>), the first sensor (<NUM>) and the second sensor (<NUM>) being mounted on the fixed portion (<NUM>);
the movable portions comprising a first nested movable portion (114a) and a second nested movable portion (114b);
characterised in that
the first sensor (<NUM>) comprising a first transceiver, wherein the first sensor (<NUM>) is configured to transmit a first light beam toward the first nested movable portion (114a) of the conveyor (<NUM>);
the second sensor (<NUM>) comprising a second transceiver, wherein the second sensor is configured to transmit a second light beam toward the second nested movable portion (114b) of the conveyor (<NUM>); and
the control unit (<NUM>) being communicably coupled with the first sensor (<NUM>) and the second sensor (<NUM>), wherein the control unit (<NUM>) is configured to:
calculate a first distance between the first sensor (<NUM>) and the first nested movable portion (114a) based on the first sensor (<NUM>) detecting a first reflection of the first light beam from a reflector (<NUM>) mounted in the first nested movable portion (114a) during a movement of the movable portions;
calculate a second distance between the second sensor (<NUM>) and the second nested movable portion (114b) based on the second sensor detecting a second reflection of the second light beam from a reflector (<NUM>) mounted in the second nested movable portion (114b) during the movement of the movable portions; and
calculate a difference value between the first distance and the second distance;
compare the difference value with a predefined threshold value;
halt the movement of the movable portions in an instance in which the difference value exceeds the predefined threshold value.