Patent Description:
Automatic guided vehicles, often referred to as AGVs, are usually driverless vehicles that are often used for material handling purposes. AGVs are capable of carrying or towing material or articles from one point to another without the need for a driver on the vehicle. AGVs are typically capable of driving themselves from a first location to a second location, such as by using navigational sensors to determine their position and heading. This position and heading information may be used by the vehicle in order for it to automatically steer itself along a desired path or toward a desired destination. The navigational sensors may include gyroscopes, sensors for detecting magnets embedded in the floor, laser reflectors, wheel encoders, transponder sensors, and a variety of other types of sensors. It is relatively common for these AGVs to be used in warehouses and material handling centers, where workers are commonly walking between stations or areas in the vicinity or alongside the AGVs.

<CIT> discloses an AGV in which a common processing system performs first detection processing in which an automatic guided vehicle provided with a grating-shaped bumper having elasticity and an LRF having a light-emitting unit and a light-receiving unit detects the presence of an obstruction on the basis of light emitted from the light-emitting unit and reflected by a light irradiation target in the surrounding area, and second detection processing in which contact of the obstruction to the automatic guided vehicle is detected by determining whether there is deformation of the grating-shaped bumper on the basis of light emitted from the light-emitting unit and reflected by the grating-shaped bumper.

The invention is defined by the subject-matter of the independent claim <NUM>.

Further embodiments of the invention form the subject-matter of the dependent claims <NUM>-<NUM>.

The objects, advantages, purposes, and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.

Referring now to the drawings and the illustrative embodiments depicted therein, an automated guided vehicle (AGV) <NUM>, <NUM> is shown that has a self-propulsion system that may operate with a navigation and guidance system, such as to follow a desired path and/or reach a desired destination in a material handling environment without and physical restraints, such as wires or tracks or the like. The AGV <NUM> is shown with a base frame structure <NUM> having an upper portion or surface <NUM> that is configured to support a material handling apparatus, such as a powered roller conveyor <NUM> (<FIG>), a robotic arm <NUM> (<FIG>), a lift unit, or other conceivable device or attachment or combinations thereof. The AGV may also have a peripheral sensory system that is utilized to monitor the peripheral area or sensory field <NUM> (<FIG>) surrounding the AGV for positional and locational control of the AGV and/or for object detection. Thus, the AGV may establish a preferred guide-path and control the propulsion system to travel along the preferred guide-path, and may also detect an obstacle on the guide-path, so to avoid the obstacle and determine a detour path around the obstacle that returns the AGV to the preferred guide-path. The peripheral sensory system may also or alternatively operate in cooperation with the material handling apparatus supported by the AGV, such as to prevent a robotic arm from undesirably contacting an object detected in the peripheral area surrounding the AGV.

To support the loads carried by the AGV <NUM> and the frame structure <NUM> of the AGV itself, freely rotating support members may be attached at peripheral portions of the base frame structure <NUM>. The freely rotating support members may be support wheel assemblies, such as shown with four casters 18a, 18b, 18c, 18d attached at the corner portions of the base frame structure <NUM>. The casters are configured to movably support the base frame structure <NUM> away from a ground surface and generally support the weight of the AGV <NUM> and any loaded material or item or the like. Also, the casters may generally support the base structure <NUM> in a generally level orientation. As shown in <FIG>, the casters 18a, 18b, 18c, 18d may each have an upper bracket <NUM> that is fixedly attaches directly to the base frame structure <NUM> and a lower bracket <NUM> that freely swivels or pivots about a generally vertical axis, where a wheel <NUM> of each caster is rotatably attached to the lower bracket <NUM> so as to permit the wheel <NUM> to freely rotate about a generally horizontal axis. Thus, the casters may generally support the entire weight of the AGV and its contents, such that it is contemplated that more or fewer casters may be used on the AGV to accommodate the size and desired load capacity of the specific AGV. It is also contemplated that the casters may optionally include encoders to monitor movement of the AGV, also known as odometry.

To move or otherwise propel the AGV <NUM> relative to the ground surface, a propulsion system may be provided that has at least one drive wheel assembly disposed between at least two of the freely rotating support members. As shown in <FIG>, the propulsion system includes two drive wheel assemblies 20a, 20b that are disposed at the lateral sides of the AGV <NUM> and are generally centered between the two front casters 18a, 18b and the two rear casters 18c, 18d. As such, the drive wheel assemblies 20a, 20b space the respective drive wheels <NUM> of the drive wheel assemblies 20a, 20b laterally apart from each other at or near the peripheral edges of the base frame structure. The drive wheels <NUM> rotate about substantially parallel axes, and it is contemplated that such rotational axes may be substantially aligned with each other. By generally centering the drive wheel assemblies 20a, 20b longitudinally along the AGV and laterally spacing the drive wheels <NUM> generally equally from the longitudinal center line CL (<FIG>) of the AGV, the drive wheels may be driven by a differential drive system to both propel and steer the AGV of over the ground surface, such as to be capable to spinning or turning with a generally zero-turn radius. The illustrated drive wheel assemblies 20a, 20b each have a separate electric drive motor <NUM> and corresponding encoder that is supported at the corresponding swing arm to directly attach to the supported drive wheel <NUM>.

The AGV <NUM> may have a suspension system <NUM> for the drive wheel assemblies 20a, 20b so as to bias the drive wheel assemblies 20a, 20b against the ground surface to maintain friction of the drive wheels <NUM> against the ground surface, such as for creating the necessary friction to move heavy loads and to allow the drive wheels <NUM> to maintain contact with the ground surface when the AGV traverses uneven ground surfaces, such as transitions to or from sloped surfaces with upward or downward inclines. As shown in <FIG>, the suspension system <NUM> is provided with intersecting swing arms 24a, 24b that pivotally mount at the base frame structure <NUM> and independently attach at each of the drive wheel assemblies 20a, 20b. The intersecting swing arms 24a, 24b each include a pivotal end <NUM> that pivotally attaches at the base frame structure <NUM>, such as about a pivot bracket <NUM> that supports a shaft <NUM> extending through the pivot end <NUM> of the swing arms to effectuate the pivotal movement of the swing arms. Thus, the shaft <NUM> may define a pivot axis PA, such as shown in <FIG>. The pivotal ends <NUM> are attached on opposing sides of the base frame structure <NUM> from the drive wheel assembly supported at the respective swing arm, such that intermediate sections of the swing arms overlap and/or intersect at an offset or spaced distance from each other. Thus, the swing arms may be intersecting when viewed from a front or rear end of the AGV, such as shown in <FIG>, and/or may be overlapping when viewed from a top or bottom of the AGV, such as shown in <FIG>. To provide the overlapping and intersecting arrangement, the illustrated swing arms 24a, 24b have a recessed area <NUM> at the intermediate sections of the swing arms between the pivotal ends and the supported wheel assemblies, as shown in <FIG>. By overlapping and intersecting the swing arms 24a, 24b, the drive wheels are nearly or substantially aligned axially and the length and corresponding moment arm of each swing arm is longer than half of the lateral width of the AGV, which has the effect of reducing the lateral tipping of the drive wheels and thus preventing uneven wear of the drive wheels.

The suspension system also includes a spring component <NUM> disposed between each of intersecting swing arms 24a, 24b and the base frame structure <NUM> at or near the respective drive wheel <NUM> for providing a downward biasing force. As illustrated, the spring component <NUM> is a gas spring that is configured for loads expected for operating the material handling apparatus. It is also contemplated that the spring component may be a mechanical spring, such as a helical spring that is designed to provide compressive forces to the wheel assemblies. In cooperation with the pivotal connection of the swing arms, the spring components are configured to provide a vertical travel for the pair of drive wheels <NUM> that extends below the casters a distance that maintains the pair of drive wheels in contact with the ground surface when the ground surface that the AGV is traveling over is uneven, such as to accommodate at least about a <NUM>% change in include or otherwise a change in slope of about <NUM> degrees. It is understood that the preferred vertical travel for the drive wheels in additional embodiments may be increased or decreased to accommodate the desired potential terrain conditions.

Referring again to <FIG>, the peripheral sensory system of the AGV is integrated into the structural frame <NUM> so as to be able to utilize two sensors <NUM> to monitor the peripheral area or sensory field <NUM> surrounding the AGV, without interfering with or protruding above the upper portion or surface <NUM> of the AGV. The base frame structure <NUM> includes intermediate horizontal slots <NUM> at each opposing longitudinal end of the base frame structure <NUM>. The intermediate horizontal slots <NUM> are each disposed at the vertical support members <NUM> between upper and lower portions or surfaces <NUM>, <NUM> of the base frame structure <NUM> for permitting two horizontally directed sensor fields 46a, 46b of the navigation and guidance system to substantially surround the AGV <NUM>. The illustrated sensors <NUM> each include a directional sensor, such as a LIDAR sensor, that scans its respective sensor field 46a, 46b and each preferably have a coverage greater than <NUM> degrees in a substantially horizontal plane, and more preferably a coverable of greater than about <NUM> degrees in a substantially horizontal plane, and yet more preferably a coverable of about <NUM> degrees in a substantially horizontal plane. The directional sensors may also or alternatively comprise optical sensors, proximity sensors, positional sensors, and the like. The sensors <NUM> are attached at support posts <NUM> (<FIG>) disposed at each opposing longitudinal end of the base frame structure <NUM> for each to emit its sensor field 46a, 46b though the intermediate horizontal slot <NUM>, such that the sensor fields overlap to form overlapping sensor fields 46c at the lateral peripheral areas of the AGV near the drive wheel assemblies 20a, 20b. The overlapping sensor fields 46c near the drive wheels, such that there may be at most a relatively small triangular area that is not part of the peripheral sensory field <NUM> that is located immediately adjacent the drive wheels, such as preferably extending laterally less than about twice the diameter of the drive wheel <NUM>.

As further shown in <FIG>, the horizontal slots <NUM> are at least partially disposed in internal structural members of the base frame structure <NUM>, such as in the vertical or upright support walls <NUM> that extend between upper and lower plates <NUM>, <NUM> of the base frame <NUM>. The lower plate <NUM> includes caster housings <NUM> that receive the casters 18a, 18b, 18c, 18d that support the AGV. The vertical wall members <NUM> and other support structures may extend upward from the lower plate <NUM> within the area not affected by the horizontal slots <NUM> with sufficient stability to support the upper plate <NUM> so that it may support the desired material handling apparatus. The upper plate <NUM> may have a standard bolt pattern or other connection feature that allows multiple different material handling apparatuses to be separately attached to the AGV, so as to allow for a desired material handling apparatus to be selected and modularly attached to the AGV for the desired operation to be performed by the AGV.

Thus, the AGV <NUM> has a body structure <NUM> with a flat top surface <NUM> that is free from obstructions to accommodate a loaded object or an interchangeable material handling device or apparatus at the central attachment area, such as a conveyor platform or a robotic arm. The interchangeable material handling devices or apparatus may be interchangeable due to the common bolt pattern at the central attachment area. To keep the top surface <NUM> free from obstruction, the vision system or laser scanners <NUM> that are used for detecting obstacles and/or navigating the AGV are located on the vehicle structure below the top surface <NUM>. It is desirable to use fewer scanners, as the use of more scanners increases the processing demands for the vision system and overall cost. As illustrated, the body structure <NUM> of the AGV <NUM> is designed with a horizontal cutout or slot <NUM> at each end of the AGV. A scanner <NUM> is positioned at a central location in each slot <NUM> at the front and rear ends of the vehicle <NUM>. With each scanner <NUM> as a center point, the slots <NUM> each extends about <NUM> degrees to a point that aligns with or near the edges of the drive wheels <NUM>. Thus, the two scanners <NUM> have overlapping fields that together provide a <NUM> degree field surrounding the AGV <NUM>, with the only blind spots being at a relatively small area outside the drive wheels <NUM>.

In general, the AGV may have at least three caster wheels that are provided to support the body structure of the AGV away from the floor, where at least one drive wheel is biased against the floor to propel the AGV. The illustrated caster wheels 18a, 18b, 18c, 18d are each mounted in a wheel housing <NUM> that attaches at a floor panel or lower plate <NUM> of the frame structure <NUM>. At least one of the caster wheels is positioned on opposing sides of the central drive wheels <NUM>, such that the weight provided by the AGV and any attachment or loaded object is entirely or at least primarily supported by the caster wheels. The central drive wheels <NUM> are each attached at an overlapping swing arm 24a, 24b that biases the drive wheels <NUM> downward against the floor to provide adequate friction for propelling the AGV. The suspension system also maintains the drive wheels <NUM> in contact with the floor surface when driving over ramped inclines or declines, thereby accommodating for changes in the slope of the floor surface. The amount of downward force provided at each drive wheel <NUM> can be adjusted by provided more or fewer or differently rated spring components, which can be accessed at top panel caps <NUM> (<FIG>). The overlapping swing arm suspension is configured to allow for increased overall length of each swing arm 24a, 24b, which reduces the amount of potential lateral wheel tilt. Wheel tilt is generally undesirable, as tilting the drive wheels <NUM> can cause them to wear unevenly and provide inconsistent wheel rotation measurements when attempting to precisely maneuver the AGV.

Referring now to the AGV <NUM> shown in <FIG>, a robotic arm <NUM> is mounted or otherwise integrated with an upper portion <NUM> of the base structure <NUM> of the AGV <NUM>. While the robotic picking apparatus <NUM> is capable of various applications, it is particularly useful in carrying out the various techniques disclosed in commonly assigned International Patent Application Publication No. <CIT> entitled AUTONOMOUS MOBILE PICKING. The AGV <NUM> has a propulsion system to propel and steer the AGV. An AGV control <NUM> includes a navigation and guidance system <NUM>, which is capable of determining precisely the position and orientation of AGV <NUM> and controlling the position and orientation of the AGV <NUM> to follow a preferred trajectory, also known as a guide-path. The control <NUM> includes forward-facing and rearward-facing light imaging, detection and ranging (LIDAR) systems <NUM> in order to detect features around AGV <NUM> and direction and distance to the features. The LIDARs <NUM> are used both to establish a guide-path and to navigate the AGV <NUM> with respect to the guide-path so that the AGV control <NUM> can guide movement of the vehicle. As will be set forth in more detail below, LIDARs <NUM> are capable of detecting the presence of obstacles and humans and responding to both. LIDARs <NUM> are commercially available from various sources, such as Navatec. Mapping software, which is commercially available, is responsive to the LIDARs in order to establish a topographical map of objects around AGV <NUM>.

The robotic arm <NUM> is supported from the base <NUM> and is controlled by a robotic control <NUM>. The robotic arm <NUM> has an end of arm tool <NUM> that may be used to grasp and manipulate articles and is interchangeable with other tools at a tool changing station <NUM> that is supported by base deck or plate <NUM> of the base structure <NUM>. The robotic control <NUM> includes a vison system, such as a camera <NUM>, that detects objects to allow end of arm tool <NUM> to grasp and manipulate the objects. The robotic control <NUM> is substantially autonomous with respect to the AGV control <NUM>. Both the AGV <NUM> and the robotic arm <NUM> can be operated autonomously or in response to instructions received from a central off-vehicle control (not shown), such as by RF or other forms of communication. By having the robotic control <NUM> be autonomous from the AGV control <NUM>, the process of picking and placing an article is separated from the process of positioning the robotic arm at a location where the picking and placing can occur.

An exemplary picking method <NUM> is illustrated in <FIG>. Inventory or donor receptacles, such as totes I, are stored on supports, such as pallets, racks, or the like. The robotic arm <NUM> picks a tote I having an inventory item needed for a customer order and places the tote on the base deck <NUM>. The robotic arm <NUM> then picks one or more inventory items from the tote and places the item(s) in order receptacles, such as tote O, which may include one or more orders for a customer and are also carried by base deck <NUM>. If necessary, the end of arm tool <NUM> may be changed at the tool changing station <NUM> in order to have a tool that is most useful for a particular operation, such as manipulating a tote I, picking up an inventory item, or the like. When the customer orders are picked, the AGV <NUM> can transport the order totes O to a pick wall or pack station for completion of the orders. Alternatively, the inventory items may be collected in order receptacles on towed vehicles or separate AGVs as disclosed in the WO `<NUM> publication referred to above.

An alternative picking method <NUM> is illustrated in <FIG>. Full cases of articles, referring to as A are picked from a support, such as a pallet, rack, or the like, by the robotic arm <NUM> after the AGV <NUM> has positioned the robotic arm adjacent to the full cases. The robotic arm <NUM> then places the article A on a conveyor <NUM> where the case is transported to a palletizer or other packing process. Alternatively, the cases may be conveyed by being collected on towed vehicles or separate AGVs as disclosed in the WO `<NUM> publication referred to above.

The AGV <NUM> is capable of carrying out a controlled obstacle avoidance technique <NUM>, such as shown in <FIG>. In response to a system mission command <NUM> issued by a central control that is either stationary, such as a warehouse management system, or an autonomous feature of AGV control <NUM>, a preferred trajectory, such as a guide path, <NUM> is generated, such as with navigation and guidance system <NUM>. The guide-path is travelled by performance of a trajectory execution loop <NUM> until an obstacle <NUM> is detected. When the obstacle is detected, navigation and guidance system <NUM> generates a detour trajectory at <NUM> which will return to the preferred trajectory, or guide path, such as by measuring clearance on both sides of the obstacle using LIDARs <NUM> and determines at <NUM> if the AGV fits the alternative trajectory. If it is determined at <NUM> that that the geometry of vehicle <NUM> fits the detour trajectory, such as by clearance on one of the sides being sufficient to guide AGV <NUM>, then a detour path is followed at <NUM>. Since the detour guide-path is calculated to return to the preferred trajectory, such as the original guide-path, the detour guide-path is followed at <NUM> which will return vehicle <NUM> to the original trajectory which will result in the original trajectory again being followed at <NUM> until it is completed at <NUM> and the vehicle stops at <NUM>. If it is determined at <NUM> that a detour trajectory cannot be calculated that avoids all obstacles and returns the vehicle to the preferred trajectory, a new mission trajectory, or alternate route, is requested at <NUM> from the central control and the method returns to following the alternate route at <NUM>.

The AGV <NUM> may also or alternatively be capable of carrying out a human detection and following technique <NUM> illustrated in <FIG>. Technique <NUM> may begin with AGV control <NUM> being in an autonomous mode at <NUM> from which it determines whether a vehicle human detection (VHD) mode <NUM> is selected. If not, then a standard mission controlled mode is carried out at <NUM> in which the AGV control follows a preferred trajectory. If it is determined at <NUM> that the VHD mode is selected, then AGV control <NUM> begins at <NUM> to verify whether an object detected is a human using known detection algorithms and, if it is determined at <NUM> that a human was verified, then the AGV control begins to follow and/or interact with the human at <NUM>. If the technique is intended to follow the human at <NUM>, then a segment path trajectory is generated at <NUM> that follows the human and the path is followed at <NUM>. If it is determined at <NUM> that the technique is not intended to follow the human, then it is determined at <NUM> whether it was intended to interact with the human. If so, the system interact mode is carried out at <NUM> and the AGV is made to be still or motionless. The interact mode is useful for the robotic arm to pick an item pointed to by the human, put away an item to a location designated by the human or to dispose of an item picked by the human. Other examples with be apparent to the skilled artisan.

Claim 1:
An automated guided vehicle (AGV, <NUM>) comprising:
a base frame (<NUM>) having an upper portion (<NUM>) configured to support a material handling apparatus (<NUM>);
a propulsion system (<NUM>) adapted to propel the base frame (<NUM>);
first and second directional sensors (<NUM>) disposed at opposing ends of the base frame and at least one operable to emit a sensor field (46a, b) within at least one slot (<NUM>) disposed between the upper portion (<NUM>) and a lower portion (<NUM>) of the base frame (<NUM>); and
wherein the sensor fields (46a, b) of the first and second directional sensors (<NUM>) each comprise coverage of at least <NUM> degrees in a substantially horizontal plane and are arranged to provide a combined sensor field (<NUM>) substantially surrounding the AGV (<NUM>),
wherein the base frame (<NUM>) includes a plurality of support members (<NUM>) extending between the upper and lower portions (<NUM>, <NUM>) of the base frame (<NUM>), and wherein the at least one slot (<NUM>) is disposed in the plurality of support members,
characterized in that the support members (<NUM>) extend upward from the lower portion (<NUM>) within the area not affected by the at least one slot (<NUM>).