Climbing robot with compliant pinion drive

Abstract

To provide a climbing robot with a compliance opinion drive device that allows a moving robot to make an endurable engagement with a rack when the moving robot is engaged with the rack for vertical climbing in an automatic order implementation (order fulfillment) system.SOLUTION: An automatic order implementation system and a moving robot (10) are disclosed. The moving robot (10) includes a compliant drive device (including a pinion 18) that moves a moving robot between the levels in the multi-level storage structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] Exemplary and non-limiting embodiments described herein relate generally to robotic movement within an automated retail supply chain storage and retrieval system, and more particularly to a compliant pinion drive on a mobile robot that enables resistant meshing with a gear rack when the mobile robot engages the gear rack for vertical climbing.

[0002] [Citation to Related Applications] This application claims priority to U.S. Provisional Patent Application No. 62 / 731,300, entitled "Climbing Robot with Compliant Pinion Drive," filed on September 14, 2018, and both applications are hereby incorporated by reference in their entirety. [Background technology]

[0003] Automated order fulfillment systems used in supply chains can fulfill orders for individual product items (also referred to herein as "each"). Traditional order fulfillment facilities store the each in containers within a multi-level storage structure with vertical and horizontal arrays of storage spaces. The automated order fulfillment system further includes a mobile robot that moves around the storage structure to transfer the containers or totes to and from the storage spaces within the storage structure. In one embodiment, the storage structure can have a horizontal floor or platform disposed around at least a portion of the storage structure that allows the mobile robot to move to and from the storage structure, a horizontal track that allows the mobile robot to move to and from the storage spaces horizontally at a given level, and a vertical tower that allows the mobile robot to move vertically between levels.

[0004] It is known to provide pinion gears on opposing sides of a mobile robot, which mesh with toothed racks on opposing sides of a vertical tower to enable vertical movement. In operation, the mobile robot may approach the vertical tower from a vertical floor, platform or rail. Once positioned within the vertical tower, motors within the mobile robot extend the opposing pinion gears of the mobile robot along their common axis of rotation until the pinion gears engage within the racks. Rotation of the pinion gears can then move the robot up and down within the vertical tower. Summary of the Invention [Problem to be solved by the invention]

[0005] With this method of engagement, it can happen that the pinion gear does not properly mesh with the rack teeth as it advances toward and into the rack, and in some cases may even get stuck against the side of the rail preventing meshing engagement. [Means for solving the problem]

[0006] Embodiments of the present technology relate to a compliant pinion drive on a mobile robot that allows for resistant meshing with a rack when the mobile robot engages the rack for vertical climbing.

[0007] In one embodiment, the technology relates to a mobile robot configured to move within a vertical or inclined aisle in an automated retrieval and storage system, the aisle having a rack with gear teeth, the mobile robot having a pinion gear configured to rotate on a shaft about an axis of rotation, the shaft configured to extend axially along the axis of rotation to position the pinion gear in meshing engagement with the rack when the mobile robot is to move within the aisle, the pinion gear having gear teeth with a chamfered lead-in configured to facilitate meshing engagement of the pinion gear and the rack without binding upon axial extension of the shaft.

[0008] In another embodiment, the present technology provides a mobile robot configured to travel within a vertical or inclined aisle in an automated retrieval and storage system, the aisle having a linear drive mount, the mobile robot having a compliant drive assembly for moving the mobile robot within the aisle, the compliant drive assembly including a motor disposed within the mobile robot, the motor having a first spline, the compliant drive assembly further including a shaft having a second spline, the shaft configured to be rotated by the motor about an axis of rotation by the first spline of the motor exerting a force on a second spline of the shaft, the shaft further comprising a compliant drive assembly configured to rotate the shaft about an axis of rotation by the first spline of the motor exerting a force on a second spline of the shaft, the shaft further comprising a compliant drive assembly configured to rotate the shaft about an axis of rotation by the first spline of the motor exerting a force on a second spline of the shaft, the compliant drive assembly further including ... the compliant drive assembly further includes a drive gear attached to one end of the shaft, the drive gear configured to move into engagement with the linear drive mount upon extension of the shaft, the first spline and the second spline configured to provide rotational play between the first spline and the second spline, the rotational play allowing some free rotation of the drive gear relative to the linear drive mount to prevent the drive gear from binding against the linear drive mount when the drive gear moves into engagement with the linear drive mount upon extension of the shaft.

[0009] In another embodiment, the technology provides an order fulfillment system including a multi-level storage structure having storage locations at different levels and vertical or inclined aisles extending between the different levels, the aisles having linear drive mounts along their lengths, the order fulfillment system including a mobile robot configured to move between the levels in the aisles, the mobile robot having a motor disposed within the mobile robot, the motor having a first spline, the mobile robot further having a shaft with a second spline, the shaft being rotated about an axis of rotation by the motor by the first spline of the motor exerting a force on the second spline of the shaft. and the shaft is further configured to be axially extended along the axis of rotation, the mobile robot further having a drive gear attached to one end of the shaft, the drive gear configured to move to engage the linear drive mount upon extension of the shaft, and the first and second splines are configured to provide rotational play between the first and second splines, the rotational play allowing some free rotation of the drive gear relative to the linear drive mount to prevent the drive gear from binding against the linear drive mount when the drive gear moves to engage the linear drive mount upon extension of the shaft.

[0010] In another embodiment, the technology relates to a method of transporting a mobile robot along a vertical or inclined aisle between storage levels in an order fulfillment facility, the aisle having a linear drive mount, the method including extending a drive gear of the mobile robot from a first position spaced from the linear drive mount to a second position where the drive engages the drive mount, the drive gear being attached to a shaft, the method further including rotating the shaft and the drive gear with a motor, the motor having a first spline, the shaft having a second spline, the shaft being rotated by a force exerted by the first spline on the second spline, the method further including preventing improper seating of the drive gear against the linear drive mount, at least in part, by providing some play between the first spline and the second spline, the play allowing some free rotation of the drive gear relative to the linear drive mount as the drive gear is extended from the first position to the second position.

[0011] This Summary is provided to introduce a collection of technical ideas in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed invention, nor is it intended to be used as an aid in determining the scope of the claimed invention. The claimed invention is not limited to embodiments that solve any or all of the disadvantages discussed in the Background of the Invention section.

[0012] Next, the present technology will be described with reference to the drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a side view of the climbing robot. [Diagram 2] FIG. 2 is an isometric view of a pinion. [Diagram 3] FIG. 2 is an isometric view of the rack structure. [Figure 4]FIG. [Diagram 5] FIG. 2 is a cross-sectional side view of the rack structure. [Figure 6] FIG. 2 is a partial cross-sectional view of the climbing robot. [Figure 7] FIG. 2 is a partial cross-sectional view of the climbing robot. [Figure 8] FIG. 2 is a partial cross-sectional view of the climbing robot. [Figure 9] FIG. 2 is a partial cross-sectional view of the climbing robot. [Figure 10] FIG. 2 is a partial cross-sectional view of the climbing robot. [Figure 11] FIG. 2 is an isometric view of the shaft. [Figure 12] FIG. 1 is an isometric view of the hub. [Figure 13] FIG. 2 is an isometric view of the shaft. [Figure 14] FIG. 1 is an isometric view of the hub. [Figure 15] FIG. 2 is an isometric view of the shaft. [Figure 16] FIG. 1 is an isometric view of the hub. [Figure 17] FIG. 2 is an isometric view of the shaft. [Figure 18] FIG. 1 is an isometric view of the hub. [Figure 19] FIG. 1 is an isometric view of the hub. [Figure 20] FIG. 2 is an isometric view of the shaft. [Figure 21] FIG. 2 is an isometric view of a pinion. [Figure 22] FIG. 2 is an isometric view of the shaft. [Diagram 23] FIG. 1 is a side view of an example order fulfillment system according to aspects of the disclosed embodiments. [Figure 24] FIG. 1 is a front view of an example order fulfillment system according to aspects of the disclosed embodiments. [Diagram 25] FIG. 1 is a partial isometric view of an example order fulfillment system according to aspects of the disclosed embodiments. [Figure 26A] 1 is a schematic diagram of a portion of a storage structure in accordance with aspects of the disclosed embodiments. [Figure 26B] FIG. 1 is an isometric view of a workstation according to aspects of the disclosed embodiments. [Figure 26C] FIG. 1 is an isometric view of a workstation according to aspects of the disclosed embodiments. [Figure 27A] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27B] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27C] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27D] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27E] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27F] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 27G] FIG. 1 illustrates a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. [Figure 28A] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28B] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28C] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28D] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28E] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28F]1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28G] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Fig. 28H] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28I] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28J] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 28K] 1 is a diagram of a vehicle illustrating a case or tote transport mechanism in accordance with aspects of the disclosed embodiments. [Figure 29] 1 is a flow diagram according to aspects of the disclosed embodiments. [Diagram 30] 1 is a schematic side view of a transmission according to aspects of the disclosed embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 1, there is shown a side view of a climbing robot 10. The climbing robot 10 is configured for use within an order fulfillment system, and may have features such as those described in U.S. Patent Application Publication No. 2017 / 0313514 A1, published November 2, 2017, entitled "Order Fulfillment System," which is hereby incorporated by reference in its entirety. The order fulfillment system includes a multi-level tote storage and retrieval structure, an autonomous robotic vehicle 10 configured to pick, transport, and place one or more totes within the order fulfillment system, a workstation configured to accept a picker (human, automated, or otherwise) that transports one or more of the totes, e.g., product totes containing multiple common ones to be picked, from one of the autonomous mobile robots to a put location, e.g., order totes having different combinations of ones reflecting fully or partially fulfilled orders and that may be located on another one of the autonomous mobile robots at the workstation, a transport deck configured to support, stage, and buffer the autonomous robot 10 between the storage and retrieval structure and the workstation, a dispensing station that ejects totes containing fulfilled orders from the order fulfillment device, and a decanting or input interface (not shown) configured to refill the order fulfillment device. The climbing robot 10 has a drive wheel 12, a support wheel 14, a guide roller 16, a pinion 18, a counter wheel 19, and a counter wheel 20. As will be described in more detail below, pinion 18, counter wheel 19 and counter wheel 20 selectively engage racks that allow robot 10 to climb or descend vertically. During climbing, counter wheel 19 and counter wheel 20 react against the cantilever weight of robot 10 with CG 22 having force 24 reacting with counter wheel 20 and force 26 reacting with counter wheel 19.The pinion 18 also supports the weight 28 of the robot 10 vertically while the counter wheel reacts the moment.

[0015] 2, there is shown an isometric view of pinion 18. Pinion 18, also referred to herein as the drive gear, has teeth 40 and keyways 42. Teeth 40 have chamfered lead-in portions 44 provided to prevent binding or failure to engage the rack.

[0016] Referring now to FIG. 3, an isometric view of the rack structure 80 is shown. Referring also to FIG. 4, a plan view of the rack structure 80 is shown. Referring also to FIG. 5, a partial cross-sectional side view of the rack structure 80 is shown. The rack structure 80 includes a rack 82 (also referred to herein as a linear drive mount), counter wheel support surfaces 84, 86, robot support rails 88, 90, and a frame 92. The teeth of the rack 82 have chamfered lead-ins 94 that are provided to prevent binding or mis-engagement when the pinion engages the rack 82. Notches 96, 98 are provided within which the counter wheel engages the rack structure. A backer bar surface 102 is provided so that the engaged pinion cannot jump or skip a rack tooth by hitting the backer bar 102 prior to disengagement of the rack teeth. The counter wheel support surfaces 84, 86 are provided as a V-wheel raceway used to center the V-wheel as will be described in detail, with surface 86 having a flat bottom portion 98 which engages with a mating surface provided on the counter wheel to set up pinion gear tooth engagement without bottoming out on the pinion gear and serves as a lead-in for the pinion gear into the rack / backer bar space. A V-shaped portion 100 is further provided to mate with a mating chamfer on the counter wheel for centering within the wheel groove 86.

[0017] Referring now to Figure 6, a partial cross-sectional view of the climbing robot 10 is shown. Racks 82, 82' are positioned on opposite sides of the robot 10. Similarly, support rails 90, 90' are positioned on opposite sides of the robot 10. In Figure 6, the robot is shown with drive wheels 12, 12' supported by support rails 90, 90'. As will be described with respect to Figures 6-10, the robot 10 engages the racks 82, 82' to climb vertically. The wheels 12, 12' are independently driven by motors 120, 120'. The independently driven motors 120, 120' are shown mounted on the frame of the robot 10, and transmit torque to shafts 122, 122' by splines or bushings 124, 124', and the pinions 18, 18' and counter wheels 19, 19' are coupled to the shafts 122, 122'. Similarly, the shafts 122, 122' transmit torque to the wheels 12, 12' via splines or bushings 126, 126'. The counter wheels 20, 20' are coupled to shafts 130, 130', respectively, and a trunnion 132 couples the shafts 122, 130 together, and a trunnion 132 prime couples the shafts 122', 130' together. A motor 136 is provided coupled to counter-rotating lead screws 138, 138' so that rotation of the motor 136 moves the shafts 122, 130 in opposition to the shafts 122', 130' to selectively engage and disengage the racks 82, 82'. As noted, the counter wheels 19, 20 have mating surfaces which engage the counter wheel support surfaces 84, 86 provided when a V-wheel track is used to center the V-wheel or counter wheels 19, 20.After engagement, the servo motor or motor 136 can be deactivated and the lead screw can drive back so that the mating surfaces of the counter wheels 19, 20 engage and follow the counter wheel support surfaces 84, 86, and by monitoring the encoder on the motor 136, the encoder position can be recorded during vertical or other movement, thereby measuring the separation of the counter wheel tracks (e.g. 86, 86') within the counter wheels in the storage system. In addition to the monitoring and measuring functions, limits can be set, e.g. if the separation of the counter wheels is less than a predetermined minimum value, the motor 136 can be re-engaged to push the counter wheels out. Similar features can be provided for the wheels 12, 12', e.g. to measure the width of the tracks or to set limits. In this case, motors may also be provided coupled to counter-rotating lead screws (not shown) so that rotation of the motors causes the trucks 140, 140' and thus the wheels 12, 12' to move in opposite directions to selectively engage and disengage the support rails 90, 90'. As will be explained in more detail, the shafts 122, 122' are characterized in that play is provided between the shafts 122 and the wheels 12 via the splines 126 so that the system does not bind excessively when the pinion 18 engages the rack 82. In one example, if play was not provided when the pinion moves out of alignment with the rack, friction between the wheels and the wheel supports would prevent smooth engagement. In the relative position of the splines 126 and the shaft 122 shown in FIG. 6, there is no rotational play between the splines 126 and the shaft 122.

[0018] 7, there is shown a partial cross-sectional view of the climbing robot 10, showing one side for clarity of the drawing. In the state shown in FIG. 7, the lead screw 138 is rotated so that the pinion 18 is about to engage the rack 82. In the relative position of the spline 126 and the shaft 122 shown in FIG. 7, there is rotational play between the spline 126 and the shaft 122, so that the pinion 18 can freely engage the rack 82.

[0019] Referring now to FIG. 8, a partial cross-sectional view of the climbing robot 10 is shown, showing one side for clarity. In the state shown in FIG. 8, the lead screw 138 is rotated so that the pinion 18 is fully engaged with the rack 82. In the relative position of the spline 126 and the shaft 122 shown in FIG. 8, there is rotational play between the spline 126 and the shaft 122, so that the pinion 18 can freely engage the rack 82. If the pinion 18 fails to engage the rack 82, a retry feature can be provided. Here, if there is interference / overlap of the pinion and rack gear tooth edges, the drive motor can be used to retract and rotate the pinion (while still located within the compliant portion of the shaft), and the pinion can be reinserted back into the rack. As an example, the pinion can be rotated slightly forward (up drive) and then reinserted to allow successful engagement of the pinion 18 with the rack 82. It should be noted that the sequence referred to with reference to Figures 6 to 10 may be reversed to disengage the pinion and activate the drive wheel, allowing subsequent horizontal movement by the drive wheel.

[0020] 9, there is shown a partial cross-sectional view of the climbing robot 10, showing one side for clarity. In the state shown in FIG. 9, the pinion 18 is fully engaged with the rack 82, and the motor 120 applies torque to the shaft 122 and the piston 18, thereby raising the climbing robot and separating the wheel 12 from the support rail 90. In the relative position of the spline 126 and the shaft 122 shown in FIG. 9, there is rotational play between the spline 126 and the shaft 122, such that the wheel 12 is free to separate from the rail 90.

[0021] Referring now to FIG. 10, a partial cross-sectional view of the climbing robot 10 is shown, showing one side for clarity. In the state shown in FIG. 10, the pinion 18 is fully engaged with the rack 82 and the motor 120 applies torque to the shaft 122 and the piston 18, so that the climbing robot is fully supported by the pinion 18 and the counter wheels 19, 20. The track 140 is retracted by a separate motor (not shown), so that the wheel 12 clears the support rail 90. In the relative position of the spline 126 and the shaft 122 shown in FIG. 10, there is no rotational play between the spline 126 and the shaft 122, so that there is no play when the wheel is stopped, so that the wheel remains centered on the compliance zone during descent.

[0022] 11, an isometric view of the shaft 122 is shown. Also, referring to FIG. 12, an isometric view of the splined hub 126 is shown. The splined hub 126 is attached to the wheel 12 and moves axially on the shaft 122. The shaft 122 has a pinion mounting portion 160 with a keyway 162 for transmitting torque to the pinion 18. The shaft 122 further has a counter wheel mounting portion 164 and a splined portion 166. The splined portion 166 has portions 168, 172 that mate with internal splines 174 of the hub 126, so that there is little or no play between the hub 126 and the shaft 122 when the hub 126 mates with the portions 168, 172. The splined portion 166 further includes a portion 170 that mates with an internal spline 174 of the hub 126 such that when the hub 126 mates with the portion 170, there is a predetermined amount of rotational play between the hub 126 and the shaft 122 and the width of the external splines is narrowed (176). Lead-ins 178, 180 are provided to allow a smooth transition between the hub 126 and the portions 168, 170, 172.

[0023] 13, an isometric view of an alternative embodiment of a shaft 122" is shown, and FIG. 14, an isometric view of an alternative embodiment of a ball spline hub 126" is shown. The ball spline hub 126" is attached to the wheel 12 and moves axially on the shaft 122". The ball spline hub 126" has recirculating balls 200, 202. The shaft 122" has a pinion mounting portion 160 with a keyway 162 for transmitting torque to the pinion 18. The shaft 122 further has a counter wheel mounting portion 164 and a grooved portion 204. The grooved portion 204 has race portions 206, 210 that mate with the recirculating balls 200, 202 of the hub 126", so that there is little or no rotational clearance between the hub 126" and the shaft 122" when the hub 126" is mated with the portions 200, 202. The grooved portion 204 further includes portions 208 that mate with the recirculating balls 200, 202 of the hub 126" so that when the hub 126" mates with the portions 208, there is a predetermined amount of rotational play between the hub 126" and the shaft 122" and the outer race is narrowed (212). Lead-ins 214, 216 are provided to allow a smooth transition between the hub 126" and the portions 206, 208, 210.

[0024] 15, an isometric view of an alternative embodiment of a shaft 122''' is shown. Also, referring to FIG. 16, an isometric view of an alternative embodiment of a square spline or hub 126''' is shown. The square hub 126''' is attached to the wheel 12 and moves axially on the shaft 122'''. The square hub 126''' has a mating square portion 240 with a lead-in chamfer 242. The shaft 122''' has a pinion mounting portion 160 with a keyway 162 for transmitting torque to the pinion 18. The shaft 122 further has a counter wheel mounting portion 164 and a spline or positive portion 246. Square portion 246 has portions 248, 252 that mate with mating square portion 240 of hub 126''' such that when hub 126''' is mated with portions 248, 252, there is little or no rotational play between hub 126''' and shaft 122'''. Square portion 246 further has portion 250 that mates with mating square portion 240 of hub 126''' such that when hub 126''' is mated with portion 250, there is a predetermined amount of rotational play between hub 126''' and shaft 122''', and outer square portion 250 has a narrower width (256). Lead-ins 258, 260 are provided to allow a smooth transition between hub 126''' and portions 248, 250, 252.

[0025] 17, an isometric view of an alternative embodiment of a shaft 300 is shown. 18, an isometric view of an alternative embodiment of a hub 320 is shown. The shaft 300 is shown mated with a hub 320 with a keyway 322. The shaft 300 is shown with a pinion 18 and a counter wheel 19. As noted, the motor drive splines or bushings and the wheel drive splines or bushings ride on the shaft and may have similar features as the hub 320 (or the hubs described above). The shaft 300 further includes a key 302 with key portions 304, 308 that mate with mating keyways in the keyed hub, so that when the keyed hub mates with the portions 304, 308, there is little or no rotational play between the hub and the shaft 300. The key is modified to have a necked down area used to provide compliance, the key 302 further has a portion 306 that mates with a keyway in the hub 320 so that when the hub 320 mates with the portion 306 there is a certain amount of rotational play between the hub and the shaft 300, the external key 302 narrows (310) at the portion 306. Lead-ins 312, 314 are provided to allow a smooth transition between the hub and the portions 304, 306, 308. The hub 320 has a linear bearing 324, a housing 326, and an insert 328 with a key 322. The linear bearing or bushing 324 may be a sleeved or recirculating ball bushing that provides the extension and retraction of the bearing on the shaft. The housing 326 holds the linear bearing 324 and further holds an insert 328 with a keyway 322 which may be bronze, a polymer, such as nylon, or the like. An insert 328 transfers torque to the shaft key 302, which has a secondary keyway 330 that transfers torque from the motor to the shaft or from the shaft to the hub. In this case, compliance is introduced when the bronze insert in the motor or hub bushing is moving over the necked down area of ​​the key.This embodiment has much the same behavior as the embodiment shown in FIG. 13 or others, but does not have rolling balls running on compliant regions.

[0026] 20, an isometric view of a shaft 340 is shown. The shaft 340 has raceways 342 adapted to mate with a recirculating ball spline hub. Alternatively, any suitable hub or spline may be used to transmit torque. The shaft 340 further includes a pinion 344 and a counter wheel 346. The shaft 340 further includes opposed keys 348, 350 which mate with keyways 352, 354, respectively, of the pinion 344. The keyways 532, 354 are cut with an additional clearance 356 to provide a predetermined amount of play between the shaft and the pinion. Features are provided to keep the key centered within the keyways when torque is not being transmitted. The pinion 344 includes a recessed rectangular area 360 which receives a torsion spring 362. The springs 362 are provided on opposite sides of the shaft and have legs 364 which engage the walls of the recesses 360 of the pinion 344. The torsion spring 362 further has a tongue 366 that engages a slot 368 in the shaft. Torque is transferred through the shaft via the slot to the tongue and then through the compliant legs 364 of the torsion spring 362 to the pinion, such that compliance is introduced between the shaft and the pinion until the key 348 engages the keyway 352.

[0027] 23-30 and the accompanying description describe the appearance of an automated retrieval and storage system that can use the compliant pinion robot 10. FIGS. 23, 24, 25, 26A, 26B, 26C, 27A-27G, 28A-28K, 29, and 30 correspond directly to FIGS. 15, 16A, 17, 54G, 54A, 54B, 60A-60G, 52A-52K, 55, and 40A of U.S. Patent Application Publication No. 2017 / 0313514(A1) (titled "Order Fulfillment System"), published on November 2, 2017, which is incorporated herein by reference in its entirety. Figures 23, 24, 25, 26A, 26B, 26C, 27A-27G, 28A-28K, 29, and 30 directly correspond to Figures 15, 16A, 17, 54G, 54A, 54B, 60A-60G, 52A-52K, 55, and 40A of U.S. Patent Application Publication No. 2017 / 0313514(A1).

[0028] 23-25, there are shown side, front and plan views, respectively, of an exemplary order fulfillment system configured in a vending configuration. Here, the order fulfillment system may be described as an order vending machine 420, i.e., "OVM" or otherwise. The order vending machine 420 represents a miniaturized version of, for example, a robotic vehicle and rack system that may be utilized in, for example, a vending store for delivered goods or any other suitable application. For example, vehicle technology may be used in e-commerce applied to the "last-mile" delivery problem. For example, "pure-play" e-commerce companies are forced to deliver the majority of orders to customers' homes, which may be costly. Retailers that both operate self-service stores and sell online may offer customers the option to pick up their orders at a store location, commonly referred to as "click-and-collect," but in practice, this model may impose additional and unpredictable workload on store personnel and result in long wait times for customers and the like. Here, the order vending machine 420 provides an automated solution that requires very little floor space (or land) while being able to safely hold large volumes of orders, and also provides convenient on-demand access and short operating hours to customers. Here, the order vending machine 420 may be a robotic vehicle-based "micro-warehouse," sometimes referred to as an order vending machine (OVM), which operates in conjunction with, for example, an e-commerce fulfillment center, for example, an e-commerce fulfillment center that includes a system that employs robotic vehicles. In one aspect, order totes ("O-totes") containing customer orders may be delivered to the OVM, stored within the OVM, and then provided to customers upon request, with the robotic vehicle performing all necessary tote storage and retrieval functions.

[0029] 26A, 26B, and 26C, an order fulfillment workstation 5500 is shown. Although one workstation 5500 is shown in FIG. 26A and 26B, it should be understood that the vault and structure 5563 (substantially similar to the vault structures described herein) can have any suitable number of workstations 5500. For example, FIG. 26A illustrates an exemplary configuration of workstations 5500 in which at least three workstations 5500 are disposed on each vault level, but in other aspects, any suitable number of workstations can be disposed on each vault level. The workstations 5500 at different levels can be vertically offset from each other, such as stacked on top of each other or stacked in a staggered arrangement. In one aspect, each workstation 5500 is communicatively connected to two transport decks 5550A, 5550B, while in other aspects, each workstation 5500 can be communicatively connected to any suitable number of transport decks. In one aspect, each transport deck 5550A, 5550B may correspond to a respective storage level, while in another aspect, the transport decks 5550A, 5550B may correspond to a common storage level (e.g., there is more than one transport deck associated with each storage / picking level). In another aspect, there may be a tower (substantially similar to the lift track 5190) located on or otherwise connected to (or disposed within) the transport deck (or aisle), the tower communicatively connecting one or more of the transport decks 5550A, 5550B (or aisles) of different storage levels with a travel loop to another tower such that the bot 5100 may travel between the stacked transport decks 5550A, 5550B (or aisles) to any desired / predetermined level of the storage structure. The workstation 5500 is configured to accommodate a picker 5520 that transports one or more each from one tote of the bot 5100 (e.g., the P tote) to a “put” location within another tote of the bot 5100 (e.g., the O tote).The workstations 5500 are arranged at multiple levels, and a human or robotic picker picks each from a product tote (P tote) and places them into either an order tote (O tote) or a mobile robot, depending on the system configuration and in a manner substantially the same as described above. In one aspect, the workstations 5500 include a picker platform 5510 disposed on transport lanes or aisles 5501, 5502, 5503, 5504, a lift tower 5190T, and a pick station 5530. A workstation 5500 is disposed on each transport deck level such that the bots 5100 on each transport deck have access to the workstation 5500. In the exemplary aspect illustrated in FIG. 26B, two transport deck levels 5550A, 5550B are shown connected to a common workstation 5500, but in other aspects, any suitable number of transport deck levels may be connected to the common workstation 5500.

[0030] Each of the transport lanes 5501, 5502, 5503, 5504 has a respective entrance and / or exit 5500E in communication with the respective transport deck 5550A, 5550B. As can be seen in FIG. 26B, the transport lanes 5501, 5504 have an entrance / exit 5500E in communication with the transport deck 5550B, while the transport lanes 5502, 5503 have an entrance / exit 5500E in communication with the transport deck 5550A. The transport lanes 5501-5504 include rails WRR that are substantially similar to the rails HRR described above with respect to the aisles that provide access to the tote storage / holding locations. As can also be seen in FIG. 26B, the lift towers 5190TWA-5190TWD connect the stacks of transport lanes together in a manner substantially similar to that described above with respect to the lift tower 5190T. The lifting towers 5190TWA to 5190TWD are substantially the same as the lifting tower 5190T described above. As an example, the lifting towers 5190TWA and 5190TWB connect the transport lanes 5503 and 5504 to each other so that the bot 5100 can cross between the transport lanes 5503 and 5504. The lifting towers 5190TWC and 5190TWD connect the transport lanes 5501 and 5502 to each other so that the bot 5100 can cross between the transport lanes 5501 and 5502.

[0031] In one aspect, one or more of the transport lanes 5501-5504 and towers 5190TWA-5190TWD may be angled (e.g., tilted or sloped) relative to the transport decks 5550A, 5550B and operator platform 5510 so that when the P totes and O totes are presented to the picker 5520 by their respective P bots and O bots, the P totes and O totes are angled so that the picker 5520 can see and approach the P totes and O totes to pick and place each from the pick / place locations defined by the towers 5190TWA, 5190TWC adjacent to the pick station 5530. In another aspect, the transport lanes 5501-5504 and towers 5190TWA-5190TWD may have any spatial relationship with the pick station 5530 and / or transport decks 5550A, 5550B to provide totes to the picker 5520 in any suitable spatial orientation.

[0032] In one aspect, the transport lanes 5501-5504, the lift towers 5190TWA-5190TWD, and the pick station 5530 have a symmetrical structure including the paths and locations of the independent product bots (P bots) and the order bots (O bots). In this aspect, there may be lateral symmetry (in the direction 5599) such that there is a left / right symmetrical arrangement. For example, the left / right symmetrical arrangement may be such that the P bot carrying the P tote is located on the right side of the workstation 5500, while the O bot carrying the O tote is located on the left side of the workstation 5500. In another aspect, the P bot and the P tote may be on the left side of the workstation 5500, while the O bot and the O tote may be on the right side of the workstation 5500.

[0033] In one aspect, there are dedicated bot flow inlet and outlet transport lanes for both P bots and O bots. For example, the flow of bots to the pick station 5530 may be such that the bots travel from a lower transport lane to an upper transport lane, or in another aspect, from an upper transport lane to a lower transport lane. For example, when a bot travels from a lower transport lane to an upper transport lane, a P bot carrying an "each" to be picked enters one or more lower / bottom transport lanes 5501 and crosses the tower 5190TWC to one or more upper transport lanes 5502 so that the "each" can be picked, where the P bot exits the workstation using one or more upper transport lanes 5502. Similarly, for example, an O bot carrying an "O" tote into which the "each" is to be placed enters one or more lower / bottom transport lanes 5504 and crosses the tower 5190TWC to one or more upper transport lanes 5503 so that the "each" can be placed, where the O bot exits the workstation using one or more upper transport lanes 5503. In another aspect, the entrance of the bots to the workstations is timed to allow the bots to enter and exit the upper transport lanes 5502, 5503 and the lower transport lanes 5501, 5504, and the towers 2190TWA-5190TWD are used to run the bots past each other, such as when the bots enter and exit the common transport lanes 5501-5504. In the above embodiment, the flow of P bots carrying P totes and the flow of O bots carrying O totes are both generally in a common direction, such as both in the direction of arrow 5598 from the lower transport lane to the upper transport lane, or both in the direction of arrow 5597 from the upper transport lane to the lower transport lane. However, in another aspect, the flow of one or more of the P bots and the O bots may be in the direction of arrow 5597 from the upper transport lane to the lower transport lane. For example, the flow of P Bot and P Tote may be in direction 5598, while the flow of O Bot and O Tote may be in direction 5597, and vice versa.

[0034] In one aspect, each side of the workstation 5500 (e.g., product side and order side) has a dedicated flow direction lift tower. For example, the lift tower 5190TWC on the product side of the workstation 5500 may be dedicated to the upward flow of bots, while the tower 5190TWD on the product side of the workstation 5500 may be dedicated to the downward flow of bots, and vice versa. Similarly, the lift tower 5190TWA on the order side of the station 5500 may be dedicated to the upward flow of bots, while the tower 5190TWB on the order side of the workstation 5500 may be dedicated to the downward flow of bots, and vice versa. The dedicated flow of bots to each tower 5190TWA-5190TWD on the respective order or product side of the workstation 5500 creates an up-down flow loop in one or more of the directions 5597, 5598 between the levels of the transport lanes 5501-5504 on the respective order and product side of the workstation 5500, for example in a manner substantially identical to that described above. As described above, only two transport lanes are shown stacked on top of each other on each side of the workstation, but in other respects (as shown in FIG. 54F), each side of the workstation may have any suitable number of transport lanes stacked on top of each other, such as more or less than two transport lanes. When three or more transport lanes are provided on the product and / or order side of the workstation 5500 stacked on top of each other, the towers 5190TWA-5190TWD may have intermediate inlets and outlets that allow bots to enter / exit the towers from intermediate transport lanes IL disposed between the topmost transport lane 5502 and the bottommost transport lane of the stack of transport lanes.

[0035] As discussed above, the towers 5190TWA, 5190TWC adjacent the pick station 5530 define pick / placement locations for bots (e.g., P totes and O totes). For example, the pick locations can be defined by the towers 5190TWA, 5190TWC such that the bots are substantially at the top of the towers 5190TWA, 5190TWC in a position along the tower that allows them to be transported between the towers 5190TWA, 5190TWC and the respective topmost transport lanes 5502, 5503. As discussed above, the towers 5190TWA, 5190TWC can be angled relative to the pick station 5530 to present the P totes and O totes to the picker 5520 in any suitable spatial orientation. In one aspect, the other towers 5190TWB, 5190TWD that form a lift loop with a respective one of the towers 5190TWA, 5190TWC (e.g., disposed along the transport lanes 5501-5504 on the opposite side of the towers 5190TWA, 5190TWC from the picker 5520 that defines the pick / place location) may be angled the same as the towers 5190TWA, 5190TWC, or may be angled at any suitable different angle relative to the pick station 5530. In one aspect, the towers 5190TWB, 5190TWD may be substantially upright (e.g., vertical). In one aspect, as described above, the transport lanes 5501-5504 may also be angled relative to the pick station to form a ramp between the transport decks 5550A, 5550B (and / or intermediate deck IL) and the operator platform 5510, the ramp allowing for substantially orthogonal alignment between the towers 5190TWA-5190TWD and one or more of the respective transport lanes 5501-5504 to facilitate easing of constraints and repeated engagement for transport of the bots 5100 from the towers 5190TWA-5190TWD to the transport lanes 5501-5504 and vice versa. In one aspect, the tower tilt / angle establishes or defines the ramp pitch.

[0036] In one aspect, the workstation 5500 includes any suitable machine-vision subsystem ("MVS") 5560, which may be substantially the same as the machine-vision subsystem described above. For example, the MVS 5560 may include any suitable visual indicator (e.g., a display and / or light source), any suitable audible indicator, any suitable motion sensor / camera, any suitable beam sensor / light curtain (e.g., break beam / curtain sensor), glove tracking system, or any other suitable device for indicating pick location, indicating place location, indicating quantity to be picked / placed, tracking hand motion of the picker 5520, verifying pick, and / or verifying place. In one aspect, a controller 5500C is provided for controlling aspects of the workstation 5500 described herein, the controller 5500C residing in the workstation 5500, a central control system CCS (such as those described above), a bot 5100 controller, or a combination thereof. The controller 5500C communicates with a machine vision system 5560 to effect each pick and place as described herein.

[0037] In one aspect, the controller 5500C is configured to identify and verify a valid pick, and the controller 5500C issues a confirmation to the P bot that the pick came from the P bot. The P bot is configured (e.g., the P bot controller is programmed) to automatically move from the pick station 5530 when the P bot receives a pick confirmation issued from the controller 5500C. In one aspect, the P bot controller can be programmed such that upon receipt of the pick confirmation, the P bot crosses to the exit of the respective transport lane 5502, or in other aspects, the P bot enters a tower, such as tower 5190TWD, and returns to the entrance transport lane 5501 to rejoin the pick line.

[0038] In one aspect, the controller 5550C is configured to identify and verify valid placements, and the controller 5500C issues a confirmation to the O-bot that the placement came from the O-bot. The O-bot is configured (e.g., the O-bot controller is programmed) to automatically move the O-bot out of the pick station 5530 when the O-bot receives the placement confirmation issued from the controller 5500C. In one aspect, the O-bot controller can be programmed such that upon receipt of the placement confirmation, the O-bot crosses to the exit of the respective transport lane 5503, or in another embodiment, the O-bot enters a tower, such as tower 5190TWB, and returns to the entrance transport lane 5504 to rejoin the placement queue. In one aspect, the O-bot can rejoin the placement queue until the O-bot exits the pick station 5530 to the transport deck, at which point the controller 5500C issues an order completion command to the O-bot.

[0039] 27A, 27B, 27C, 27D, 27E, 27F, and 27G depict a step-by-step progression of a vehicle transitioning from horizontal to vertical motion in accordance with aspects of the disclosed embodiments. Specifically, a vehicle in the form of a bot 5100 is shown, which, as indicated elsewhere herein, may be substantially identical to the bots described throughout this disclosure unless otherwise specified.

[0040] In Figures 27A-27C, the bot 5100 travels horizontally from right to left on the page. In Figures 27D and 27E, the drive gear 5140B (and the opposing drive gear 5140A, not shown) and guide bearing are extended laterally away from the body of the bot 5100, thereby engaging the lift tracks 5190. Each lift track 5190 has a drive surface 5190D and a guide surface 5190B disposed opposite the drive surface 5190D and separated by the thickness of the lift track 5190, the drive surface including a gear rack 5195 as described and shown elsewhere herein.

[0041] 27F-27G, bot 5100 travels vertically upward on lift track 5190.

[0042] 28A-28J, an exemplary operational principle of the transfer of a tote 5300 between a tote holding location 5350 and a bot 5100 is provided. In one aspect, the bot 5100 traverses a horizontal rail HRR to a given tote holding location 5350 (FIG. 29, block 5801). The bot 5100 may include any suitable sensor or odometry to facilitate determining the location of the bot 5100 relative to the tote holding location 5350. Once the tote 5300 is substantially aligned with the payload area 5180, the flippers 5230B, 5240B (and flippers 5230A, 5240A) are rotated in direction 5399 so that the flippers extend under and behind their respective catch surfaces 5300C1, 5300C2 to cam the tote 5300 into the payload area 5180 of the bot 5100 as described above with reference to FIG. 28K (FIG. 29, block 5803). The flippers 5230B, 5240B continue to move in direction 5399 to pull the tote laterally in direction 5999A from the tote holding location 5350 to the payload area 5180 of the bot 5100 until the tote 5300 is located at the predetermined payload position within the payload area 5180 as shown in FIG. 28D (FIG. 29, block 5804). In one aspect, the bot 5100 includes any suitable sensor that detects the position of the tote 5300 relative to the payload area 5180 to stop the movement of the recirculating bidirectional traversers 5230T, 5240T when the tote 5300 reaches a predetermined position within the payload area 5180. To transfer the tote 5300 from the bot to the tote holding location 5350 as viewed from the same side of the bot 5100 on which the tote was transferred onto the bot 5100, the flippers 5230B, 5240B (and flippers 5230A, 5240A) are moved in a direction 5398 so that the flippers 5230B, 5240B contact the respective catch surfaces 5300C3, 5300C4 of the tote 5300 (FIG. 29, block 5806).The flippers 5230B, 5240B continue to move in direction 5398 such that the flippers 5230B, 5240B push the tote 5300 laterally in direction 5999B until the flippers 5230B, 5240B disengage from their respective catch surfaces 5300C3, 5300C4 of the tote 5300, thereby partially pushing the tote 5300 out of the bot 5100 (Figure 29, block 5808). Flippers 5230A, 5230A (and flippers 5230B, 5240B) continue to move in direction 5398 so that flippers 5230A, 5240A engage their respective catch surfaces 5300C1, 5300C2, and further movement of flippers 5230A, 5240A in direction 5398 pushes the tote 5300 laterally out of the bot 5100 in direction 5999B, and the tote 5300 is ultimately positioned within the tote holding location 5350 when flippers 5230A, 5240A disengage from their respective catch surfaces 5300C1, 5300C2 as they move in direction 5398 (Figure 29, block 5811). The flippers 5230A, 5230B, 5240A, 5240B are moved in direction 5399 or direction 5398 to a start or home position of the flippers 5230A, 5230B, 5240A, 5240B, as shown in FIG. 28J, which may be located along the center line CL of the bot 5100, or may be at any other suitable location along the path of travel of the flippers 5230A, 5230B, 5240A, 5240B (FIG. 29, block 5812).

[0043] If the tote 5300 is pushed from the opposite side of the bot 5100 rather than the side on which the tote 5300 was pushed onto the bot 5100, referring to FIG. 28D, the flippers 5230B, 5240B (engaging with their respective catch surfaces 5300C1, 5300C2) move in direction 5399 to partially push the tote 5300 away from the bot in direction 5999A until the flippers 5230B, 5240B disengage from their respective catch surfaces 5300C1, 5300C2 (FIG. 29, block 5814). Flippers 5230A, 5240A (together with flippers 5230B, 5240B) continue to move in direction 5399 such that flippers 5230A, 5240A engage respective catch surfaces 5300C1, 5300C2 and push tote 5300 in direction 5999A until flippers 5230A, 5240A disengage from respective catch surfaces 5300C1, 5300C2 and finally position tote 5300 in a tote holding location in a manner substantially identical to that described above (Figure 29, block 5816), and flippers 5230A, 5240A, 5230B, 5240B are returned to their starting positions (Figure 29, block 5812).

[0044] In another aspect, the bot 5100 has a tote transport system including one or more flippers (also called catches or paddles) 5400 mounted to a recirculating bidirectional traverser 5400T (substantially similar to the recirculating bidirectional traversers 5230T, 5240T described above), but in this aspect, the recirculating bidirectional traverser 5400T is configured to engage one side of the tote 5300 (e.g., the bottom side 5300B or the front side / front surface 5300F, etc.). In this aspect, the recirculating bidirectional traverser 5400T includes a frame 5400TF that is movably mounted to the frame 5100F (e.g., a linear bearing or slide) of the bot 5100 for movement laterally in a direction 5999. For example, a linear drive 5410 (such as a solenoid or other linear actuator) may be mounted to the frame 5100F and coupled to the frame 5400TF by any suitable transmission such that the frame 5400TF moves in the direction 5999 as will be described below. The linear drive 5410 is a bidirectional drive (such as when the bot 5100 loads and unloads totes from both sides of the bot 5100), while in other respects, the linear drive 5410 is a unidirectional drive (such as when the bot 5100 payloads and unloads totes from a single side of the bot 5100). The recirculating bidirectional traverser 5400T also includes sprockets 5407, 5408 provided at opposite ends of the frame 5400TF, and a sprocket 5405 mounted to the frame 5400TF between the sprockets 5407, 5408. The sprockets 5405, 5407, 5408 are connected to one another by a chain 5406, and one or more flippers 5400 are attached to the chain to move in unison therewith in a manner substantially identical to that described above. The sprockets 5405, 5407, 5408 and the chain 5406 may be disposed in a common plane that is substantially parallel to the plane of the bot crossing surface (such as the deck or rail on which the bot travels). The sprockets 5405 are mounted on a common shaft with the sprocket 5404, the common shaft being supported by the frame 5400TF.Drive unit 5401 (also mounted on frame 5400TF) has a sprocket 5403 attached to the output of drive unit 5401, which is coupled to sprocket 5404 by chain 5402 such that operation of drive unit 5401 causes movement of one or more flippers 5400 in one or more of directions 5991, 5992.

[0045] 30, there is shown a schematic side view of a drive gear, e.g., a wheel with a sprocket 1080, engaged with a ramp. In this case, a counter bearing 1082 engages a counter rail 1084 while a chain 1086 (also referred to herein as a linear drive mount) engages a sprocket 1088. FIG. 30 shows the initial engagement condition, which may be provided with a rubber backing to allow chain meshing and limit wear due to engagement. It goes without saying that the sprocket 1088 may be mounted on the shaft 122 as shown in FIG. 8. As mentioned above, in the relative position of the spline 126 and the shaft 122 shown in FIG. 8, there is rotational play between the sprocket 126 and the shaft 122, so that the sprocket 1088 can freely engage the chain 1086. [Explanation of symbols]

[0046] 10. Climbing Robot 12 Drive Wheel 16 Guide roller 14 Support Wheel 18 Pinion 19,20 Counter wheel 5500 Order Fulfillment Workstation 5550A, 5550B Transport Deck 5563 Storage structure

Claims

1. 1. A mobile robot configured to travel within a vertical or inclined aisle in an automated retrieval and storage system, the aisle having a linear drive mount, the mobile robot comprising: a compliant drive assembly for moving the mobile robot through the passageway, the compliant drive assembly comprising: a hub supporting a wheel, the hub having a first spline; a shaft having a second spline, the shaft being configured to rotate about a rotational axis by a motor and configured to extend axially along the rotational axis; a drive gear attached to one end of the shaft, the drive gear configured to move into engagement with the linear drive mount upon extension of the shaft; the first spline and the second spline are configured to prevent the drive gear from binding against the linear drive mount when the drive gear moves into engagement with the linear drive mount upon extension of the shaft, and the first spline and the second spline are configured to prevent the drive gear from binding by providing rotational play between the first spline and the second spline, the rotational play allowing some free rotation of the drive gear relative to the linear drive mount.

2. 2. The mobile robot of claim 1, wherein the mobile robot is configured to move up and down the aisle by rotation of the drive gear relative to the linear drive mount.

3. 2. The mobile robot of claim 1, wherein the drive gear comprises a pinion gear and the linear drive mount comprises a rack with teeth configured to mesh with the pinion gear.

4. 4. The mobile robot of claim 3, wherein the pinion gear has gear teeth with chamfered lead-ins configured to facilitate meshing engagement of the pinion gear and the rack without binding upon axial extension of the shaft.

5. 2. The mobile robot of claim 1, wherein the drive gear comprises a sprocket and the linear drive mount comprises a chain, the teeth of the sprocket being configured to mesh with the links of the chain.

6. 2. The mobile robot of claim 1, wherein the linear drive mount is provided along a track within the passageway, the mobile robot further comprising a counter wheel attached to one end of the shaft adjacent to the drive gear, the counter wheel being configured to ride within a groove formed in the track to keep the mobile robot centered in a direction transverse to its direction of travel.

7. the linear drive mount includes a first linear drive mount mounted on a first side of the passageway, the passageway further having a second linear drive mount mounted on a second side of the passageway opposite the first side, the compliant drive assembly includes a first compliant drive assembly, the motor includes a first motor, the shaft includes a first shaft, the drive gear includes a first drive gear, and the mobile robot further includes: a second compliant drive assembly for moving the mobile robot through the passageway, the second compliant drive assembly comprising: a second motor disposed within the mobile robot, the second motor having a third spline; a second shaft having a fourth spline, the second shaft being configured to be rotated about a rotational axis by the second motor by the third spline of the second motor exerting a force on the fourth spline of the second shaft, the second shaft being further configured to be axially elongated along the rotational axis; a second drive gear attached to one end of the second shaft, the second drive gear configured to move into engagement with the second linear drive mount upon extension of the second shaft; 2. The mobile robot of claim 1, wherein the third spline and the fourth spline are configured to provide rotational play between the third spline and the fourth spline, the rotational play allowing some free rotation of the second drive gear relative to the second linear drive mount to prevent the second drive gear from binding against the second linear drive mount when the second drive gear moves into engagement with the second linear drive mount upon extension of the second shaft.

8. 8. The mobile robot of claim 7, wherein said first shaft and said second shaft share a common axis of rotation.

9. 9. The mobile robot of claim 8, wherein the first and second linear drive mounts are provided along first and second tracks in opposite sides of the passageway, the mobile robot further comprising first and second counter wheels attached to opposite ends of the first and second shafts, the first and second counter wheels configured to ride within first and second grooves formed in the first and second tracks to keep the mobile robot centered laterally relative to its direction of travel.

10. A third motor; and 10. The mobile robot of claim 9, further comprising first and second counter-rotating lead screws driven by the third motor, wherein rotation of the counter-rotating lead screws causes the first and second shafts to axially extend in opposite directions to position the first and second drive gears within the first and second linear drive mounts and to position the first and second counter wheels within the first and second grooves.

11. 11. The mobile robot of claim 10, further comprising an encoder on said third motor for measuring how far apart said first counter wheel and said second counter wheel move while riding in said first and second grooves.

12. 2. The mobile robot of claim 1, wherein the hub comprises a recirculating ball.

13. 13. The mobile robot of claim 12, wherein the shaft transmits torque to the wheel through the recirculating ball portion of the hub.

14. 14. The mobile robot of claim 13, wherein the shaft comprises a grooved portion including a first portion and a second portion that mate with the recirculating ball portion of the hub, the hub mating with the first portion and the second portion to limit rotational play between the hub and the shaft.

15. 15. The mobile robot of claim 14, wherein the grooved portion further comprises a third portion that mates with the recirculating ball portion of the hub, and when the hub mates with the third portion, the third portion expands to provide rotational play between the hub and the shaft.

16. 1. A mobile robot configured to move within a vertical or inclined aisle in an automated retrieval and storage system, comprising: the passageway includes a linear drive mount; the mobile robot having a compliant drive assembly for moving the mobile robot within the passage; The compliant drive assembly includes: A motor provided in the mobile robot; a shaft configured to be rotated by the motor about a rotational axis, the shaft further configured to extend axially along the rotational axis; a hub supporting a wheel, said hub having a recirculating ball portion; a drive gear attached to one end of the shaft, the drive gear configured to move into engagement with the linear drive mount upon extension of the shaft; the shaft transmits torque to the wheel through the recirculating ball portion of the hub; The hub is attached to the wheel and moves axially on the shaft; the shaft includes a grooved portion including a first portion and a second portion that mate with the recirculating ball portion of the hub, the hub mates with the first portion and the second portion to limit rotational play between the hub and the shaft; the grooved portion further comprises a third portion adapted to mate with the recirculating ball portion of the hub, such that when the hub mates with the third portion, the third portion expands to provide rotational play between the hub and the shaft; a lead-in portion is provided to allow a smooth transition between the hub 12 and the first, second and third portions, and the rotational play allows some free rotation of the drive gear relative to the linear drive mount and prevents the drive gear from binding against the linear drive mount when the drive gear moves into engagement with the linear drive mount upon extension of the shaft.

Images