BOT BLOCKING SYSTEM Cross-Reference to Related Applications [0001] This application claims priority of United States Provisional Application No. 63/413,508 entitled BOT BLOCKING SYSTEM, filed October 5, 2022, which is incorporated herein by reference in its entirety for all purposes. Technical Field [0001] The exemplary and non-limiting embodiments relate generally to a blocking system and assembly, more particularly, to a blocking assembly configured to safely brake mobile robots in a multilevel structure. Background [0002] Automated Storage and Retrieval systems have earned a vital role in supply chain management. One example of their rising demand can be seen in the grocery industry where order fulfillment centers are operated to efficiently fulfill customer orders. These facilities typically comprise storage sections located in conjunction with access portions to allow retrieval and storage of items, as needed. These items may be stored in temperature-controlled areas within the storage section. Typically, totes or containers are used to store items at desired locations. An example order fulfillment center includes a multilevel structure with horizontal rows accessing various storage sections. Mobile robots can travel these horizontal rows to retrieve or store totes as required and assist fulfilling a customer order. Brief Description of the Drawings [0003] Embodiments of the present technology will be described with reference to the following figures. [0004] FIGURE 1 illustrates an isometric view of a multilevel structure incorporating a bot blocking system according to some embodiments. Attorney Docket No.: 8842-157800-WO_8213WO01 [0005] FIGURES 2A and 2B illustrate perspective views of an example mobile robot with emphasis on drive parts that interface with an exemplary bot blocking system according to some embodiments. [0006] FIGURES 3A and 3B illustrate perspective views of an example embodiment of a bot blocking assembly interfacing with a mobile robot according to some embodiments. [0007] FIGURE 3C illustrates a front view of an exemplary blocking assembly affixed to a rail platform and further representing acting forces in said interaction according to some embodiments. [0008] FIGURES 4A to 4D illustrate perspective views of an example embodiment of a bot blocking assembly. FIGURES 4A and 4B depict isometric views of said assembly while FIGURES 4C and 4D depict isometric views of said assembly in an exploded state according to some embodiments. [0009] FIGURES 5A to 5D illustrate perspective views of another example embodiment of a bot blocking assembly. FIGURE 5A illustrates an isometric view of another example embodiment of a bot blocking assembly interfacing with a mobile robot, while FIGURES 5B and 5C depict isometric views of said assembly, while FIGURE 5D depicts isometric views of said assembly in an exploded state according to some embodiments. [0010] FIGURES 6A to 6D illustrate perspective views of yet another example embodiment of a bot blocking assembly. FIGURE 6A illustrates an isometric view of another example embodiment of a bot blocking assembly interfacing with a mobile robot, whereas FIGURES 6B and 6C depict isometric views of said blocking assembly while FIGURE 6D depicts isometric views of said assembly in an exploded state according to some embodiments. [0011] FIGURES 7A to 7G illustrate views of yet another example embodiment of a bot blocking assembly. FIGURES 7A, 7E, 7F, and 7G illustrate isometric views of another example embodiment of a bot blocking assembly interfacing with a mobile robot in various states. FIGURES 6B and 6C depict isometric views of said blocking assembly. FIGURE 7D depicts isometric views of a connection aid for said blocking assembly according to some embodiments. [0012] FIGURE 8 illustrates method for blocking a robot to prevent boundary breach according to some embodiments. Attorney Docket No.: 8842-157800-WO_8213WO01 Detailed Description [0013] Embodiments of the present disclosure will now be described with reference to the figures, which in general relate to a blocking system and assembly, and more particularly, to a blocking assembly configured to safely brake mobile robots in a multilevel structure. [0014] It is understood that the present embodiments may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the invention to those skilled in the art. Indeed, the embodiments are intended to cover alternatives, modifications and equivalents of these embodiments, which are included within the scope and spirit of the invention as defined by the appended claims. Furthermore, in the following detailed description, specific details are set forth in order to provide an understanding of the present embodiments. [0015] The terms “top” and “bottom,” “upper” and “lower” and “vertical” and “horizontal” as may be used herein are by way of example and illustrative purposes only and are not meant to limit the description of the embodiments inasmuch as the referenced item can be exchanged in position and orientation. Also, as used herein, the terms "substantially" and/or "about" mean that the specified dimension or parameter may be varied within an acceptable manufacturing tolerance for a given application. In one non-limiting embodiment, the acceptable manufacturing tolerance is 0.15mm, or alternatively ± .25% of a given dimension. [0016] For purposes of this disclosure, a connection may be a direct connection or an indirect connection (e.g., via one or more other parts). In some cases, when a first element is referred to as being connected, affixed, mounted or coupled to a second element, the first and second elements may be directly connected, affixed, mounted or coupled to each other or indirectly connected, affixed, mounted or coupled to each other. When a first element is referred to as being directly connected, affixed, mounted or coupled to a second element, then there are no intervening elements between the first and second elements (other than possibly an adhesive or melted metal used to connect, affix, mount or couple the first and second elements). [0017] In accordance with one aspect, an example is provided in a blocking system for mobile robots in a multilevel structure comprising a plurality of horizontal aisles, the blocking system comprising: a plurality of rail platforms forming the horizontal aisles, the mobile robot configured Attorney Docket No.: 8842-157800-WO_8213WO01 to travel the horizontal aisles via the rail platforms, a blocking component configured to affix at least a part of the rail platforms, the blocking component further comprising a contact surface to mate the part of the rail platform and, a friction material positioned between the contact surface and the part of the rail platform, wherein the mobile robot decelerates on traveling the part of the rail platform affixed to the removable member. The blocking component further comprises a trapping member configured to engage a portion of the mobile robot when travelling the part of the rail platform affixed to the blocking component. The blocking component is formed of a first material that is frictionally biased against a second material that forms the rail platform. The blocking component is configured to absorb kinetic energy of the mobile robot and dissipates the kinetic energy. The blocking component jointly with the friction material absorbs kinetic energy of the mobile robot and dissipates the kinetic energy. The blocking component is affixed to the part of the rail platform to apply a force substantially normal to walls of the rail platform. The normal force is a function of one or more variables related to the blocking component. The blocking component is formed of a material with high tensile strength and high heat resistance. The blocking component is clamped onto the rail platform. [0018] In accordance with another aspect, an example is provided of a braking assembly for a transfer vehicle, the transfer vehicle being operational in a multi-rack structure having plurality of levels, multi rack structure further comprising workstation/s positioned adjacent thereto, the transfer vehicle configured to operate along levels of the multi-rack structure via a transfer platform, the braking assembly comprising: a blocking component affixed to the transfer platform via a contact surface on the blocking component and at least a part of the transfer platform; and, a friction material disposed between the contact surface and the part of the transfer platform, wherein the blocking component is configured to slide along length of the transfer platform, wherein the mobile robot decelerates on travelling the part of the transfer platform rail affixed to the blocking component. The braking assembly further comprises a trapping member configured to receive and retain at least a part of the mobile robot. The mobile robot interfaces the part of the transfer platform affixed to the blocking component without wear to the multi-rack structure. The blocking component is affixed to the part of the transfer platform to apply a force substantially normal to walls of the transfer platform. The normal force is a function of one or more variables related to the blocking component and/ or the friction material. Attorney Docket No.: 8842-157800-WO_8213WO01 [0019] In accordance with another aspect, an example is provided of a method of stopping a mobile robot in an automated storage and retrieval system comprising a plurality of horizontal aisles having rail platforms, the mobile robot configured to travel upon the rail platforms, the method comprising; assembling a braking assembly comprising a blocking component and/or a friction material; removably affixing the braking assembly to at least a part of the rail platforms such that the part of the rail platforms is accessible to the mobile robot; interfacing the mobile robot with the part of the rail platform affixed to the braking assembly when the mobile robot travels to breach a boundary of the automated storage and retrieval system; decelerating the mobile robot; and, dissipating kinetic energy from the mobile robot into heat energy. Decelerating the mobile robot further comprises trapping a portion of the mobile robot via a trapping member provided in the braking assembly. Further, decelerating the mobile robot comprises applying a braking force in a direction normal to walls of the rail platforms via the blocking component. The braking force applied to walls of the rail platform is a function of one or more variables related to the blocking component. Dissipating kinetic energy released from the mobile robot into heat energy prohibits wear to the automated storage and retrieval system. [0020] Various measures are implemented to maintain operator safety and control movement of mobile robots within the multilevel storage structure for order fulfillment. In addition to remotely controlled methods, mechanical safeguard systems may be provided to avoid the mobile robots from breaching boundary of the multilevel structure. These mechanical safeguards are expected to safely decelerate, and arrest motion of mobile robots in case of potential breach. Moreover, execution of the safeguards should inhibit damage to mobile robots and/or the multilevel structure. Another requirement may be to allow easy installation of these safeguards and capability to adapt to variations in the multilevel structure. [0021] Other similar systems targeted to block mobile vehicles within a multilevel structure typically rely on devices such as gas charged cylinder, crush materials or destructive collision that forbids reuse of impacted portion of multilevel structure and/or mobile vehicles. Moreover, rail mounted brakes that are presently used are complicated in terms of installation and reinstallation in case of impact. Most rail mounted brakes require complementing features on the mobile vehicles that jointly act as a blocking system. Such complementing blocking system decreases use in other variations of multilevel structure and/ or mobile vehicles that work in Attorney Docket No.: 8842-157800-WO_8213WO01 conjunction with the multilevel structure. Some examples may be found in the following patents and patent publications, which are hereby incorporated by reference in their entireties: U.S. Patent No. 5927444. discloses brake for a track operated vehicle using friction between two surfaces. One of the surfaces being a brake pad on the vehicle and other being a lateral side of the track. This is distinct from blocking system disclosed here that does not required modification or implementation on the vehicle or mobile robot. U.S. Patent No. 11,104,294 discloses an energy absorbing means provided on the mobile robot itself. The energy absorbing means include elastically deformable padding, crush material and spring-loaded devices. U.S. Publication No. 2013/0333987 discloses a two-part blocking system with a brake assembly having a pair of brake pads and a stop assembly with stopping surfaces to interface the brake pads. The brake assembly and the stop assembly can be interchangeably mounted on vehicle or rails that the vehicle travels on. This is distinct from the blocking system and assembly disclosed herein that may retroactively fit a multilevel structure and does not require any part of the blocking assembly to be located on mobile robot(s). U.S. Publication No. 2016/0304279 discloses emergency stop for a shuttle travelling along horizontal rails. The system provides frictional coupling between shuttle and rail along with a pressure biased locking mechanism with wheel. The locking mechanism and wheel together have an extension to be received in respective holes provided in web of rails. Blocking mechanism of the present disclosure refrains from providing any add-ons to the multilevel structure with horizontal rails. [0022] The disclosed embodiment may be described as a bot blocking system for use in an automation application such as with ASRS (Automated Storage and Retrieval System) used in supply chain, for example in retail supply chain. The embodiment disclosed herein is for absorbing kinetic energy and dissipating it as heat in ASRS application, more specifically in ASRS having mobile robots. The embodiment can be used in other applications, such as storage and retrieval of items in workflow. Another field of use is within an order fulfillment facility in retail a supply chain. [0023] The disclosed embodiment may contain features as disclosed in co-pending U.S. Publication No.2019/0176323 entitled "CONFIGURABLE SERVICE ISOLATION ZONES FOR SERVICE OF EQUIPMENT EMPLOYING MOBILE ROBOTS" published June 13, 2019, and U.S. Publication No. US2022/0281494 entitled “MECHANICAL GUARD BOT Attorney Docket No.: 8842-157800-WO_8213WO01 BLCOKING SYSTEM” published September 8, 2022. The disclosure of said patent applications are hereby incorporated by reference in their entirety. [0024] The disclosed embodiment may be integrated with automated storage and retrieval systems, picking systems or otherwise as disclosed in U.S. Patent No. 10,179,700 issued January 15, 2019 and entitled "Automated System for Transporting Payloads", U.S. Patent No. 10,435,241 issued October 8, 2019 and entitled "Storage and Retrieval System," U.S. Patent No. 11,142,398 issued October 12, 2021 and entitled "Order Fulfillment Center", the disclosure of all of said patent publications are hereby incorporated by reference in their entirely. [0025] The present disclosure relates to a blocking system for mobile robots that may operate in an automated storage and retrieval structure (ASRS). One example application of an ASRS may be in, but not limited to, an order fulfillment center. The ASRS may comprise one or more multilevel structures composed of plurality of horizontal aisles and vertical or inclined passages that may be travelled by mobile robots. Mobile robot(s) may access various locations within the multilevel structure to store, transfer or retrieve totes with required items to fulfill a customer order. The mobile robot(s) may be controlled by a robot control system for their operation within or in vicinity of the multilevel structure. The storage section may be arranged in numerous configurations. In between multiple storage locations may be a network of horizontal aisles and inclined or vertical passages that the mobile robot may travel to access the storage location and/ or workstations positioned adjacent to or remotely form the multilevel storage structure. ASRS may further comprise deck areas accessible to a fleet of mobile robots. An exemplary deck area may be strategically located within the ASRS to route mobile robot to pre-determined horizontal aisles belonging to pre-determined levels in the multilevel structure. The horizontal aisle may be composed of rails that terminate to form part of a boundary of the multilevel structure. The multilevel structure may provide one or more storage sections to store items in totes or containers. In a normal setting, mobile robots may be powered and programmed to operate in identified locations and may not breach a pre-set boundary in the multilevel structure. These boundaries may be represented by end of the structure, for example but not limited to, an end of a horizontal aisle, edge of a deck region, end of an inclined passage or end of a storage section. In another example, boundaries may be virtually defined within a Attorney Docket No.: 8842-157800-WO_8213WO01 program feed for respective mobile robots. Breach of said boundaries may lead to delay in processing customer orders, wear to the multilevel structure and/or the mobile robot(s) or injury to human operator(s) on site. The ASRS may provide a variety of measures to avoid boundary breach. These measures may be executed autonomously, remotely, or on-site. The mobile robots may be constructed with in-built protocols or mechanisms to avoid breach of a boundary of the multilevel structure. Additional remotely controlled protocols or instructions may be implemented for avoiding a “run-away” mobile robot. The disclosed embodiment includes mechanical implementations over horizontal rails to function as a bot blocking system and avoids potential boundary breach by the mobile robot(s). These mechanical implementations are expected to safely decelerate and arrest motion of a mobile robot. Moreover, execution of the blocking system should inhibit damage to mobile robots and/or the multilevel structure. The blocking system of the present disclosure further allows easy installation of mechanical implementation and capability to adapt to variations in the multilevel structure. [0026] Referring now to FIG.1 in conjunction with FIG.2A and 2B, there is shown a portion of multilevel structure 307 with an example mobile robot 303 approaching a boundary-breach situation. Multilevel structure 307 includes a plurality of rail platforms 318 that may form horizontal aisles for operation of mobile robot(s) 303. Further, there is installed a bot blocking assembly 501 to clamp on or capture at least a portion of rail platforms 318. In some embodiments, the bot blocking assembly 501 maybe clamped or bolted onto the rail platforms 318. Bot blocking assembly 501 may be configured to allow mobile robot 303 to travel thereupon. This may result in safely decelerating and arresting motion of mobile robot 303 by providing spring energized blocking component(s). The example bot blocking assembly 501 serves as a linear friction brake along with interfacing and/or trapping at least a part of mobile robot 303. In FIG 2A and 2B, there is shown an example mobile robot 303 with one or more drive mechanisms. Exemplary mobile robot 303 may be battery operated or may provide chargeable elements that may energize when the mobile robot 303 operates. Mobile robot 303 may further comprise a frame 303F to retain and couple plurality of drive mechanisms therewith. At least one of said drive mechanisms may be committed to horizontal motion of mobile robot 303. Horizontal drive mechanism may include guide wheel 303W coupled to frame 303F via a drive truck 303T portion. In case of a potential breach of boundary, mobile robot 303 may be configured to travel on the Attorney Docket No.: 8842-157800-WO_8213WO01 clamped portion of rail platforms 318 and consequently travel on blocking assembly 501 that may interface with and/or trap the mobile robot 303. In the present example, bot blocking assembly 501 may interface with horizontal guide wheel 303W and/or drive truck 303T. [0027] Referring now to FIG. 3A to FIG. 3B, there is shown an exemplary mobile robot 303 operatively positioned on a rail platform 318. Rail platforms 318 may form horizontal aisles, thereby providing travel pathways to allow operation of said mobile robots 303 thereupon. As discussed above, mobile robots 303 may further comprise drive mechanism committed to operate mobile robot(s) 303 along an axis parallel to length of horizontal aisles. Exemplary drive mechanism may include wheels constructed and positioned for horizontal movement of the mobile robots such that wheels may drive on the rail platforms 318 provided therewith. Wheels or another motion mechanism may be supported by a frame of mobile robot 303. In an exemplary ASRS setting, horizontal aisles may be substantially defined by a pair of rail platforms 318. In some embodiments, more than a single set of wheels or motion mechanism(s) may be employed for movement of mobile robots along travel pathways and within ASRS. In yet another embodiment, mobile robots 303 may comprise a body such as but not limited to a chassis or frame of the mobile robot. Chassis or frame 303F therein may engage the one or more drive mechanisms that assist in movement of the mobile robot 303 along horizontal aisles and/ or along inclined/vertical passages. In the present disclosure, drive truck(s) 305T may serve as an intermediate coupler to retain and engage the drive mechanisms with frame 303F of mobile robot 303. [0028] Continuing to refer to FIG. 3A and FIG. 3B, there is shown a mobile robot 303 disposed in a decelerated and subsequently halted position along exemplary rail platforms 318. Fig 3A illustrates a top-down isometric view of a blocking system in operation, for mobile robot(s) 303. In present embodiment, a blocking system may comprise one or more mechanical components configured to affix to a portion of the rail platforms 318. Exemplary blocking assembly 301 may include one or more blocking components 325 that may affix to rail platform(s) 318. Blocking component(s) 325 having more than one part may jointly affix to rail platform(s) 318. In other embodiments, blocking component 325 may be a single continuous part made to clamp and remain coupled to rail platforms 318. Blocking component(s) 325 maybe coupled to rail platform(s) 318 through different joining mechanisms such as, but not limited to, mechanical Attorney Docket No.: 8842-157800-WO_8213WO01 fastening via threaded, non-threaded or integral fasteners, riveting, using adhesive, etc. In some embodiments, a friction material may be positioned between joining surfaces of blocking component(s) 325 and rail platform(s) 318. Affixing of the mechanical component may be removably engaged with the rail platform and can be re-positioned if necessary. Repositioning or reinstallation of any components of blocking assembly 301 may not require alteration in the multilevel structure. In some instances, blocking components described herein may also be referred to as a removable component or a movable component. [0029] Continuing to refer to FIG. 3A and FIG.3B, blocking component(s) 325, as discussed above, serves to arrest, and decelerate one or more mobile robot(s) 303 to avoid breach of the multilevel structure. Frictional relationship between the material of rail platform(s) 318 and the material of blocking component 325 may achieve the above stated purpose. In some embodiments, materials having higher coefficient of friction therebetween may be employed for composing rail platform(s) 318 and blocking component(s) 325. Another factor in choosing material may be maintaining consistency in friction coefficient values in case of wear on surfaces. [0030] Referring now to FIG.3C, there is shown a perspective front view of exemplary blocking assembly 301 affixed to rail platform 318. Braking forces result from the interaction of rail platform 318 and blocking component(s) 325 when mobile robot travels on the clamped section of rail platform 318. Directional arrows adjoining Fn may represent a normal force acting on interfacing surfaces of blocking component 325 and rail platform portion or connector plate 319. Directional arrows adjoining Fr may represent static and/or dynamic frictional forces acting between interfacing surfaces. Rail platform 318 may be substantially composed of steel or carbon steel or material(s) with like properties. In some embodiments, exemplary rail platform 318 may be composed of steel with galvannealed coating. Exemplary blocking component(s) 325 may be composed of steel, mild steel, or aluminum. It should be noted that a variety of material sets may be used with a high value of coefficient of friction between. For example, the coefficient of friction (μ) between steel and aluminum may typically be ~0.6. [0031] Following equation represents coefficient of friction calculation, μ= Fr/ Fn Transposing above equations gives frictional force (Fr) = μ x normal force (Fn) Attorney Docket No.: 8842-157800-WO_8213WO01 [0032] Frictional force (Fr) in said example serves as braking force that may inhibit motion of mobile robot 303. Exemplary blocking assembly 301 and subsequent embodiments of blocking assembly discussed herein may be composed of parts to tune acting normal forces that may be generated to obtain desired level of friction force Fr. Necessary braking force may be calculated based on coefficient of friction (μ), known weight of mobile robot 303 and pre-determined velocity of the mobile robot 303 when said example robot travels on interfacing rail platform 318 and blocking component(s) 325. In some embodiments, the blocking component is formed of a material with high tensile strength and high heat resistance. [0033] Referring now to FIG.4A-D, there is shown an example blocking assembly 301 affixed to at least a pair of rail platforms 318. Combination of shown blocking assembly on each of rail platforms 318 of pair of rail platforms 318 may be composed and affixed to be mirror images of each other. Blocking assembly 301 may serve to operate on both side of drive mechanism(s) as may be provided on example mobile robot 303, shown in FIG. 3A and FIG. 3B. Blocking assembly 301 of FIG. 4A- FIG. 4D may comprise a plurality of blocking components 325 such as blocking component 325A and 325B. Blocking component(s) 325A, 325B may jointly affix to rail platform 318 at respective contact surfaces 327A and 327B. Coupling aid 326 may serve to engage blocking component(s) 325A, 325B and assist in operationally securing blocking component(s) 325A, 325B to at least a portion of rail platform 318. Blocking components 325A and 325B may further provide one or more coupling features to engage coupling aid 326. In present disclosure, coupling aid 326 may be a spring operationally engaging one or more complementing coupling features of blocking components 325A and 325B. Thus, the coupling aid 326 secures the blocking component(s) 325A, 325B to rail platforms 318 while pulling blocking component(s) 325A, 325B into tight engagement with portions of rail platform 318. The force with which coupling aid 326 pulls components 325A and 225B toward each other directly affects the frictional force between components 225A/B and portions of the rail platform 318. It should be noted that other mechanical components may be employed as coupling aid 326. Material and dimensions of coupling aid 326 may play a role in tuning braking force (Fr) applied by blocking assembly 301. [0034] Continuing to refer to FIG. 4A-D, friction material 329 may be positioned at contact surface(s) between blocking component 325 and rail platforms 318. In present embodiment, Attorney Docket No.: 8842-157800-WO_8213WO01 friction material 329 may be respectively positioned and secured at contact surfaces 327A and/or 327B of blocking component 325A and 325B that may interface with distinct surfaces of rail platform 318. Joining of blocking component(s) 325A and 325B may assist in capturing and retaining friction material 329 in a pre-determined position. A plurality of friction material(s) 329 may be employed to obtain a pre-determined contact interaction between blocking components 325 and rail platform 318. Some examples of friction materials may be, but not limited to, elastomeric material, acrylic, graphitic, sintered metals, glass, ceramic carbon and other natural or advanced fibers, etc. Selection of friction material 329 may be dependent on coefficient of friction and ability to maintain said coefficient of friction, speed of mobile robot(s) 303, heat tolerance, temperature in said section of multilevel structure, etc. [0035] Blocking of mobile robot 303 may be achieved by providing additional catch features to interface one or more parts of mobile robot 303. Trapping member 330 may serve as a catch to physically block further motion of the mobile robot 303. In particular, blocking components 325 of blocking assembly 301 may be placed on one or both rail platforms 318 on opposed sides of an aisle of the multilevel structure 307, for example 1 to 5 feet in advance of a hard stop location past which a robot cannot be allowed to travel. Upon the wheels 303W (or other portion of mobile robot) engaging trapping member 330, the mobile robot 303 will pull the blocking components 325 along the rail platforms 318. The frictional force between the blocking components 325 and the rail platforms 318 will decelerate movement of the blocking assembly 301 along rail platforms 318, and safely decelerate the mobile robot 303 to a stop before reaching the hard stop location. After the mobile robot 303 retreats from the hard stop location, the blocking components 325 may be manually or automatedly moved back to their original positions. In this embodiment, a horizontal guide wheel 303W belonging to one or many drive mechanisms on mobile robot 303 may interface with trapping member 330. In other embodiments, trapping member 330 may interface with parts in addition to horizontal guide wheel 303W. Drive truck 303T portion may also interface with trapping member 330. In should be noted that a single braking system or blocking assembly 301 may comprise one or more trapping members 330 to interface with multiple parts of mobile robot 303. In some embodiments, trapping member 330 may be shaped and dimensioned to appropriately contact and/or retain respective parts of mobile robot 303. Attorney Docket No.: 8842-157800-WO_8213WO01 [0036] Blocking assembly 301 may further provide capability to tune acting forces such as but not limited to, normal forces that may in turn impact frictional forces acting between contact surface of blocking components, friction material and interfacing surfaces of rail platform(s) such as a wall of the rail platform. In example blocking assembly of FIG.4A-D, tuning of acting forces may be dependent on parameters such as, but not limited to, thickness of blocking component(s) 325, type of friction material 329, material and dimension of coupling aid 326, etc. Other embodiments of blocking assembly 301 may provide distinct parameters that factor in tuning braking forces that act on an example mobile robot 303. [0037] Referring now to FIG. 5A-D, there is shown another blocking assembly 501 interfacing with mobile robot 303 to arrest and decelerate said mobile robot 303. Rail platform 318 may serve as a travel path for operation of mobile robot 303. Drive mechanism(s) with at least one horizontal guide wheel 303W may operate on rail platform 318. Horizontal guide wheel 303W may be engaged with a frame or chassis of mobile robot 303 via a drive truck 303T. Blocking assembly 501 may further comprise blocking component 525 to affix to at least a portion of example rail platform 318. In the present embodiment, blocking component 525 may clamp onto a joinable feature such as but not limited to connector plate 319 of example rail platform 318. Affixing may be achieved by sliding and fastening blocking component 525 over connector plate 319 such that connector plate 319 may be captured therebetween. Blocking component 525 may be constructed to serve as an elongated spring to slide and clamp on connector plate 319. Additional fastening features may be provided to ensure vigorous coupling of blocking component 525 and connector plate 319. In the present embodiment, blocking component 525 may be composed of a single continuous part and may be installed by a single operator. Fastening features such as coupling aid 526 may be employed to ensure robust joining of blocking component 525 with connector plate 319. [0038] Continuing to refer to FIG. 5A-D, blocking assembly 501 further comprises a trapping member 530 to interface with one or more parts of example mobile robot 303. Trapping member 530 may serve as a catch to physically contact and/or retain at least one part of mobile robot 303, thereby supplementing linear frictional force from blocking component 525 with a stopping element such as but not limited to trapping member 530. In present embodiment, trapping member 530 operationally interfaces with horizontal guide wheel 303W and drive truck 303T. Trapping Attorney Docket No.: 8842-157800-WO_8213WO01 member 530 may be composed to form a loop or cavity within which horizontal guide wheel 303W may be trapped and retained. In this example, a peripheral portion of trapping member 530 may contact drive truck 303T and serve as a stopping component therein. [0039] Referring to FIG.5D, there is shown an exploded view of example blocking assembly 501. Blocking component 525 may clamp and contact rail platform 318 at connector plate 319, in particular, contact surface 527 of blocking component 525 contacts connector plate 319. Material and/or thickness of blocking component 525 may be selected to tune a desired braking force acting between rail platform 318 and mobile robot 303 (shown in FIG.5A). Blocking component 525 may be composed to serve as an elongated spring biased to clamp and retain connector plate 319. In the present embodiment, friction material 529 may also be employed in blocking assembly 501 to further tune a braking force acting therewith. Friction material 529 may be positioned between contact surface 527 of blocking component 525 and connector plate 319. Presence of friction material 529 may enhance frictional force acting between interfacing surfaces i.e., contact surface 527 and plate 319. In other embodiments, friction material 529 may be located at multiple pre-determined locations between contact surface 527 and plate 319. As discussed above, a plurality of friction material(s) 529 may be employed to obtain a pre-determined contact interaction between blocking components 525 and rail platform 318. Some examples of friction materials may be, but not limited to, elastomeric material, acrylic, graphitic, sintered metals, glass, ceramic carbon and other natural or advanced fibers, etc. Selection of friction material 529 may be dependent on the coefficient of friction and ability to maintain said coefficient of friction, speed of mobile robot(s) 303, heat tolerance, temperature in said section of multilevel structure, etc. [0040] Referring now to FIG. 6A to FIG. 6D, there is shown yet another example of blocking assembly 701 operating on example mobile robot 303 to prevent breach of boundary of multilevel structure 307 (shown in FIG 1). Blocking assembly 701 may be composed of one or more blocking component(s) 725 that may affix to a portion of rail platform 318. In this embodiment, blocking component 725 may affix to connector plate 319 through at least one fastening element. In particular, connecting aid 726 may serve as a fastening element. Connecting aid 726 may further comprise a damper spring 726S (FIG.6D) affixed substantially perpendicular to a length of rail platform 318. Damper spring 726S may serve as a force absorbing component for when Attorney Docket No.: 8842-157800-WO_8213WO01 mobile robot 303 interfaces with blocking assembly 701. Further, damper spring 726S may operatively engage with blocking component 725 and rail platform 318, via a connecting pin 726P. [0041] Continuing to refer to FIGS. 6A-6D, blocking component 725 may be disposed along a length of rail platform 318 and further include a trapping member 730. In this embodiment, blocking component 725 and trapping member 730 may be composed of a single continuous material sheet. In positioning blocking component 725, trapping member 730 may be located to contact one or more parts of mobile robot 303. As depicted in FIG.6A, in said example blocking assembly 701, blocking component 725 may contact horizontal guide wheel 303W and/or drive truck 303T. In operation, horizontal guide wheel 303W may ride on section of rail platform 318 that is affixed to blocking assembly 701. Consequently, horizontal guide wheel 303W and/or drive truck 303T may jointly or distinctly interface trapping member 730 causing mobile robot 303 to encounter a hard stop. Impact from above discussed interface between mobile robot 303 and trapping member 730 may cause the blocking assembly to shift from its position prior to the interface. [0042] As discussed earlier, coupling aid 726, that serves as a fastening mechanism may experience impact from mobile robot 303. Shifting of blocking assembly 701 from prior position may cause connecting aid 726 to travel along longitudinal slot 724. Coupling pin 726P may be constructed to complement longitudinal slot 724, allowing coupling pin 726P to travel along longitudinal slot 724. Damper spring 726S, situated along coupling pin 726P may serve as a deceleration element. Spring 726S forces coupling pin 726P into frictional engagement with rail platform 318. This frictional engagement opposes motion of the trapping member 730 and decelerates the mobile robot when the mobile robot engages and moves the trapping member. Interface of mobile robot 303 with blocking assembly 701 may compress damper spring 726S resulting in added frictional force between blocking component 725 and rail platform 318. Subsequently, frictional forces acting between rail platform 318 and blocking component 725 may decelerate mobile robot 303. Subsequent interface of mobile robot 303 with trapping member 730 may provide a hard stop to mobile robot 303. Catching and arresting of mobile robot 303 may dislocate blocking assembly 701, in which case, guiding connecting pin 726P may travel Attorney Docket No.: 8842-157800-WO_8213WO01 along longitudinal slot 724 to support said dislocation without causing wear or reduce the wear to mobile robot 303 and/or multilevel structure 307 (shown in FIG.1). [0043] Referring now to FIG. 7A-7G, there is shown yet another example of blocking assembly 801 to prevent breach of the boundary of multilevel structure 307 (shown in FIG 1). Blocking assembly 801 may include one or more blocking component(s) 825 that may be affixed to a portion of the rail platform 318. In this embodiment, the blocking component 825 may be affixed to the top of the rail platform 318 via at least one fastening element such as a connecting aid 826. The connecting aid 826 is inserted through a longitudinal slot 824 of the removeable component 825 and affixed substantially perpendicularly to a length of the rail platform 318. As shown in FIG. 7D, the connecting aid 826 may comprise a bolt 826B, a nut 826N, a top washer 826W1, and a bottom washer 826W1 (FIG. 7D), wherein the rail platform 318 and the blocking component 825 would be positioned between the two washers 826W1 and 826 W2. [0044] As shown in FIG.7A, the component(s) 825 may be installed on both sides of a horizontal aisle on top of the rail platform 318. The compressive force of a connecting aid 826 provides the normal force to create friction. The top washer 826W1 and the bottom washer 826W2 distribute the force of the bolt 826B and the nut 826N over a larger area. The top washer 826W1 of the blocking component 825 distributes the load to both sides of the slot 824. [0045] The blocking component 825 includes a trapping member 830 extending towards the center of the aisle and configured to contact one or more parts of mobile robot 303 such as the drive truck 303T and horizontal guide wheel 303W. In operation, horizontal guide wheel 303W may ride on a section of rail platform 318 that is affixed to blocking assembly 801. Consequently, horizontal guide wheel 303W and/or drive truck 303T may jointly or separately interface the trapping member 830 to engage the blocking assembly 801. [0046] In some embodiments, as shown in more details in FIGS. 7B and 7C, the blocking component 825 has a pair of bends 840 on the top surface to provide added stiffness to the body of the blocking component 825. In some embodiments, the blocking component 825 further has a bent-down tab 850 that wraps around the back of the blocking component 825, which can serve as a guide during installation. For example, after placing the blocking component 825 on the rail platform 318 with the 824B bolt passing through the longitudinal slot 824 and the holes on the rail platform 318, the bent-down tab 850 can be pushed up against the back of the rail platform Attorney Docket No.: 8842-157800-WO_8213WO01 318, aligning the blocking component 825 in the correct orientation before the connecting aid 826 is further tightened. [0047] In some embodiments, a first friction interface is provided between the blocking component 825 and the rail platform 318 and a second friction interface is provided between the blocking component 825 and the top washer 826W1. In some embodiments, the underside contact surface 827 of the blocking component 825, the side of bent-down tab 850 contacting the rail platform 318, the top washer 826W1, and/or the bottom washer 826W2 may comprise or be formed of friction material 329. In some embodiments, When a mobile robot 303 crashes into a pair of blocking component 825, the kinetic force overcomes the static friction between the blocking component 825 and the connecting aid 26 and/or the rail platform 318, and the blocking component 825 slides along the connecting aid 826 via the longitudinal slot 824. The friction causes the mobile robot 303 to slow down to a stop in a controlled manner. This friction force can be fine-tuned by adjusting the torque applied by the bolt 826B and nut 826N of connecting aid 826 to control the stopping distance of the mobile robot 303. Since the stopping distance of the mobile robot 303 and the force imparted into the rest of the system via friction are inversely related, this mechanism allows the designer to calibrate the mechanism for a shorter stopping distance and higher force or a longer stopping distance that imparts less force into the rest of the system. Lower force may be desired to reduce damage to the mobile robot 303 and/or the storage structure, while a shorter stopping distance may be desired when there is limited space between the blocking assembly 801 and the protected region. [0048] FIG. 7A illustrates the blocking assembly 801 in a pre-crash state, prior to the mobile robot 303 engaging the blocking assembly 801. As shown in FIG.7A, the blocking assembly 801 is designed such that most of the blocking component 825 is positioned on top of the rail platform 318 in this initial position. This allows for the mobile robot 303 to travel into the area adjacent to trapping member 830 of the blocking component 825 without colliding with other parts of the blocking component 825. This is useful for traveling to adjacent locations, both horizontally and vertically. In the pre-crash state, the blocking component 825 is positioned such that the connecting aid 826 is at the far end of the longitudinal slot 824 relative to the mobile robot 303. [0049] FIG.7E illustrates the blocking assembly 801 in a crash-start state, when the mobile robot 303 makes contact with the trapping member 830 of the blocking component 825. The blocking Attorney Docket No.: 8842-157800-WO_8213WO01 component 825 is shaped such that when the mobile robot 303 impacts the blocking component 825 the collision is between a robust portion of the mobile robot 303 and the blocking component(s) 325, which limits the damage to the mobile robot 303. [0050] FIG. 7F illustrates the blocking assembly 801 in a soft stop state, where the blocking component 825 is partially extended via the longitudinal slot 824 and the connecting aid 826. In some embodiments, the blocking assembly 801, including the friction mechanism, is calibrated for to provide a soft stop for a worst-case scenario of robot mass and velocity. The connecting aid 826 may be tightened to a specific torque value to create the appropriate compressive force such that the mobile robot 303 comes to a complete stop before the blocking component 825 is fully extended. That is, the connecting aid 826 does not contact the near end of the longitudinal slot 824 in a soft stop. In some embodiments, the blocking component 825 is designed to support the weight of the mobile robot 303 hanging partially over the end of the rail platform 318 with minor deflection. The added stiffness provided by the bends 840 limits the deformation of the blocking component 825 when it is cantilevered past the end of the rail platform 318 supporting the weight of the mobile robot 303. The geometry of the blocking component 825 has features to interface with the shape of the mobile robot 303 such that it will hook around the mobile robot 303 to prevent the mobile robot 303 from driving over the blocking component 825 or falling out. In some embodiments, the bent-down tab 850 that wraps around the sides of the rail platform 318 serves to prevent the blocking component 825 from rotating too far in a collision, keeping it aligned in the down-aisle direction. [0051] FIG. 7G illustrates the blocking assembly 801 in a hard stop state, where the blocking component 825 is fully extended via the longitudinal slot 824 and connecting aid 826. In some embodiments, the longitudinal slot 824 of the blocking component 825 may be made longer than the expected stopping distance of the mobile robot 303 as a safety measure. If the friction mechanism is not sufficient, the blocking component 825 will slide until the end of the connecting aid 826 catches on the bolt 826B of the connecting aid 826. A hard stop will impart more force into the mobile robot 303 and the storage structure, but will stop the mobile robot 303 from travelling further. [0052] Above discussed blocking assemblies 301, 501, 701, 801 are aimed to provide a linear braking system based on spring energy and the frictional forces they generate. Components Attorney Docket No.: 8842-157800-WO_8213WO01 forming exemplary blocking assemblies 301, 501, 701, and 801 jointly serve to create friction with example mobile robot 303 and may further dissipate declaration energy of mobile robot 303 as heat. Multiple variations may be composed of above embodiments to provide spring energized linear brakes intended to bleed off declaration energy as heat and perform stopping action without wear to multilevel structure and /or mobile robot. Said variations fall within scope of the above- described embodiment and should be considered obvious to person skilled in the art. [0053] In addition to spring energy, above embodiments are designed to achieve a constant or substantially constant coefficient of friction between interfacing surfaces such as but not limited to, rail platform 318 and contact surfaces – 327, 527, 727, and 827 respectively depicted in above embodiments. Numerous dimensional and geometrical variations of above embodiments may achieve constant or substantial constant coefficient of friction between interfacing surfaces in a system, such as discussed above and should be considered obvious to person skilled in the art. [0054] Blocking assemblies 301, 501, 701, and 801 further aim to provide effective and simple installation thereof in a multilevel structure. Generally, above discussed blocking assemblies encompass other possibilities of providing sliding part(s) that may safely interface mobile robot without causing damage to mobile robot and/or multilevel structure. Moreover, majority of part(s) forming blocking assemblies such as, but not limited to, blocking assemblies – 301, 501 and 701, may be tunable to generate appropriate magnitude of braking force to stop mobile robot s from breaching boundary of the multilevel structure. [0055] Fig. 8 is a flowchart of an example method for stopping a mobile robot in an automated storage and retrieval system. In some embodiments, one or more steps of FIG. 8 may performed by the blocking assemblies 301, 501, 701, or 801 and/or a controls system of the mobile robot 303. [0056] At step 910 a blocking assembly comprising a blocking component is assembled. At step 920 the blocking assembly is removably affixed to at least a part of a rail platform of the automated storage and retrieval system such that the part of the rail platform is accessible to the mobile robot. At step 930, the mobile robot interfaces with the part of the rail platform affixed to the blocking assembly when the mobile robot travels to breach a boundary of the automated storage and retrieval system. At step 940, the mobile robot is decelerated by the blocking Attorney Docket No.: 8842-157800-WO_8213WO01 assembly. At step 950, the blocking assembly dissipates kinetic energy from the mobile robot into heat energy. [0057] The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the description to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the claimed system and its practical application to thereby enable others skilled in the art to best utilize the claimed system in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the method be defined by the claims appended hereto. Attorney Docket No.: 8842-157800-WO_8213WO01