System and manufacturing method for track control of an automated material transportation system

Abstract

A system and method for track management of an overhead transport (OHT) system for an automated material handling system (AMHS) includes a controller in communication with the OHT system, including a vehicle traveling on the track of the OHT. The track management system also includes a turntable located on a portion of the OHT and equipped with a set of fixed tracks. Upon receiving a request to rotate the turntable from a first operating direction to a second operating direction, the controller engages at least one brake sensor located near the turntable. The controller then instructs the turntable to rotate from the first operating direction to the second operating direction. Upon completion, the controller releases at least one brake, allowing the vehicle to travel directly in the second operating direction.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a system and method for track control of an automated material transportation system. Background Art

[0002] The following describes automated material handling systems, manufacturing execution systems, and overhead transport systems. The manufacture of semiconductor components involves the use of a variety of high-tech production and metrology tools, performing a series of process steps in a specific sequence and often within a specific timeframe. In a wafer fabrication facility (or "fab"), the primary function of the wafer logistics system is to deliver wafers to each tool at the correct time and track the wafers' location and status throughout the manufacturing process. Automated material handling systems (AMHS) and / or manufacturing execution systems (MES) are used in fabs to perform automated functions more efficiently, consistently, and safely than through manual methods. Manufacturing processes often require the use of overhead transport (OHT) to move wafers to different processing stations within the fab. As wafer transport carriers move along the OHT's tracks, traffic can occur on the OHT, particularly at intersections. Summary of the Invention

[0003] According to some embodiments of the present disclosure, a method for track control of an AMHS is provided, comprising receiving, at a controller including a processor in communication with a memory, a request to rotate a turntable on an OHT of the AMHS from a first operating direction to a second operating direction. The method further comprises engaging at least one brake sensor located near the turntable and rotating the turntable from the first operating direction to the second operating direction. The method further comprises disengaging at least one brake in response to the turntable rotating from the first operating direction to the second operating direction.

[0004] According to some embodiments of the present disclosure, a track management system is provided, comprising an overhead transport (OHT) system associated with an automated material handling system (AMHS), the system having a plurality of fixed tracks within a semiconductor manufacturing facility and at least one vehicle configured to travel along the plurality of fixed tracks. The system also includes a controller having a processor in communication with a memory, the controller being in electronic communication with the OHT system. The track management system also includes a turntable having a set of fixed tracks positioned thereon, the turntable being positioned on a portion of the OHT. The memory in communication with the processor is configured to store instructions, executable by the processor, that cause the processor to receive a request to rotate the turntable from a first operating direction to a second operating direction and engage at least one brake sensor proximate to the turntable. The memory further stores instructions, executable by the processor, to rotate the turntable from the first operating direction to the second operating direction and to disengage at least one brake in response to the turntable rotating from the first operating direction to the second operating direction.

[0005] According to some embodiments of the present disclosure, a computer-implemented method is provided for transport management of a vehicle track on an automated material transport system including an overhead transport (OHT) system. The method includes receiving a request to rotate a turntable on the OHT of an AMHS from a first operating direction to a second operating direction. The method also includes clearing at least one vehicle traveling along the first operating direction to pass through the turntable and engaging at least one brake sensor proximate to the turntable. In addition, the method also includes communicating a stop message to each of a plurality of vehicles traveling toward the turntable and rotating the turntable from the first operating direction to the second operating direction. In addition, the method also includes receiving a transition completion signal from the turntable confirming the rotation from the first operating direction to the second operating direction based on the output of a plurality of alignment sensors. The method also includes disengaging at least one brake in response to rotating the turntable from the first operating direction to the second operating direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The various aspects of the present disclosure will be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of discussion.

[0007] Figure 1 is a block diagram illustrating an AMHS and an OHT according to some embodiments of the present disclosure.

[0008] Figure 2A A turntable in a first operating direction for use in an AMHS / OHT system according to some embodiments of the present disclosure is shown.

[0009] Figure 2B The turntable is shown in a second operating direction for use in an AMHS / OHT system according to some embodiments of the present disclosure.

[0010] Figure 3A A turntable is shown in a first operating direction for use in an AMHS / OHT system according to some embodiments of the present disclosure.

[0011] Figure 3B The turntable is shown in a second operating direction for use in an AMHS / OHT system according to some embodiments of the present disclosure.

[0012] Figure 3C The turntable is shown in a third operating direction for use in an AMHS / OHT system according to some embodiments of the present disclosure.

[0013] Figure 4 A block diagram of an AMHS / OHT controller according to some embodiments of the present disclosure is shown.

[0014] Figure 5 A flow chart of a method for AMHS / OHT track control is depicted according to some embodiments of the present disclosure.

[0015] Figure 6 A flow chart of a method for AMHS / OHT track control is depicted according to some embodiments of the present disclosure.

[0016] Figure 7 A flow chart of a method for AMHS / OHT track control is depicted according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0017] The following disclosure provides many different embodiments or examples for implementing the different features of the provided subject matter. Specific examples of components and arrangements are set forth below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first feature over or on a second feature may include embodiments in which the first and second features are formed to be in direct contact, and may also include embodiments in which additional features may be formed between the first and second features so that the first and second features are not in direct contact. In addition, the present disclosure may reuse reference numbers and / or letters in various examples. Such repetition is for the sake of brevity and clarity and does not, in itself, represent a relationship between the various embodiments and / or configurations discussed.

[0018] Furthermore, for ease of description, spatially relative terms, such as "beneath," "below," "lower," "above," and "upper," may be used herein to describe the relationship of one element or feature to another element or feature as depicted in the figures. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0019] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms defined in commonly used dictionaries, for example, should be interpreted as having a meaning consistent with their meanings in the relevant art and this disclosure, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0020] A semiconductor foundry may include multiple wafer fabs. During the manufacturing process, a batch of goods may be transferred between these multiple fabs for use at different steps in the manufacturing process. "Inter-fab transfer" involves the transfer of a batch of goods, such as a wafer carrier or a group of wafer carriers, from one fab to another. It should be noted that different fabs are distinct because they may occupy different physical spaces (e.g., different buildings or different floors or suites within the same building) and / or may constitute independent sub-production lines. Generally, different fabs may be located in the same building or in different buildings. "Inter-AMHS transfer" involves the transfer of a batch of goods from one AMHS to another, whether these AMHSs are distributed within a single fab or systems located in different fabs. Each fab may include multiple stages and / or multiple floors. In this regard, in some embodiments, a fab may be a so-called "Gigafab." "Inter-stage transfer" involves the transfer of a batch of goods from one stage to another.

[0021] Each stage of the wafer fab includes multiple tunnel-type process areas, which may include process tools or equipment. The equipment in each tunnel-type process area can be interconnected by a cross-area overhead transport (OHT) system. The tunnel-type process area can be interconnected with other tunnel-type process areas by a cross-area OHT system. As is familiar to those skilled in the art, the intra-area OHT system and the cross-area OHT system include overhead rails or general guide rails on which the OHT carriers transport the wafer carriers containing the wafer batches to be processed to the equipment in the tunnel-type process area, and are often transported out of the equipment in the tunnel-type process area by a stocker. In addition to or in place of the OHT system, each wafer fab may include an intra-area and / or cross-area overhead transport vehicle (OHS) system. Each wafer fab may also include a cross-floor transport system. The cross-floor transport system may include elevators and / or other mechanisms for achieving cross-floor transport of wafer carriers.

[0022] refer to Figure 1 , the figure shows a schematic diagram of a portion of the AMHS system 100 according to an embodiment of the present disclosure. Figure 1 As shown, the AMHS system 100 includes an overhead transport (OHT) system 102, which may include, but is not limited to, for example, automated vehicles, personnel-guided vehicles, rail-guided vehicles, overhead transport vehicles, overhead crane transport, etc. As used herein, the vehicle 112 may include Figure 1Any of the above mentioned with respect to the OHT 102. The OHT 102 of the AMHS system 100 includes a plurality of tracks or guide rails 104 located throughout the manufacturing location. These fixed tracks 104 may also utilize one or more cross track segments 122 disposed between parallel sections of the tracks 104 to enable the vehicle 112 to be transferred between these sections and change direction accordingly. Figure 1 As shown in FIG, the OHT 102 includes various track sections, represented by a main track section 124 that runs the length of the OHT 102, and one or more vertical sections 126, 128 extending from the main track section 124 to enable the use of additional process tools 116. The carrier 112 is suitably configured to move along the track 104 of the OHT 102 according to instructions, commands, pre-programmed programs, etc. provided by the AMHS / OHT controller 108, as will be discussed in more detail below.

[0023] like Figure 1 As shown, the AMHS system 100 also includes one or more wafer stockers 114 that can be used to receive and place wafer carriers for processing by one or more wafer processing or manufacturing components, generally represented as Figure 1 The AMHS system 100 further includes a process tool 116 for the OHT 102. Those skilled in the art will appreciate that the process tool 116 may include, for example, but not limited to, a dry or wet etch chamber, a CVD chamber, a sub-atmospheric chemical vapor deposition tool, a cleaning chamber, an EUV chamber, or other semiconductor manufacturing tools. In various embodiments, the process tool 116 and the wafer stocker 114 are located next to or near the track 104 of the OHT 102 so that the carrier 112 can transfer the wafer carrier between the process tool 116 or the stocker 114. The AMHS system 100 also includes a repair section 118 of the OHT 102, wherein a portion of the track 104 is positioned to receive a damaged carrier 112 or a carrier 112 that requires maintenance. It should be appreciated that such a section 118 enables a vehicle 112 to be removed from the normal transportation flow along the track 104 of the OHT 102 to provide a safe and remote location for maintenance and / or repair, while the remaining vehicles 112 on the OHT 102 can continue their respective operations in the AMHS system 100.

[0024] As will be appreciated by those skilled in the art, the wafer stocker 114 may include an internal box for temporarily placing and storing a plurality of wafer carriers in preparation for transport to the process tool 116. Thus, the wafer stocker 114 may provide a wafer carrier retention area. It will be appreciated by those skilled in the art that the wafer stocker 114 may include a port for loading and unloading wafer carriers from the wafer stocker 114. Additionally, the wafer stocker 114 may include automated components, such as a robotic arm, configured to grab, raise, lower, store, and / or retrieve wafer carriers from the stocker 114.

[0025] The OHT 102 of the AMHS system 100 further includes at least one turntable 106 located at an intersection of the tracks 104. The turntable 106 includes a section of fixed track 110 configured to align with any set of parallel tracks 104 located at the intersection based on rotation of the turntable 106. Figures 2A-3C Additional views of the turntable 106 are provided according to various embodiments of the present disclosure.

[0026] Now refer to Figure 2A , the figure shows that the turntable 106 is located at Figure 1 The first running direction corresponding to the position shown in FIG. 1 allows the carrier 112 to pass directly along the main track section 124. In this position, the fixed track section 110 is aligned with the track 104 of the main track section 124. To ensure alignment, the AMHS / OHT controller 108 uses a plurality of alignment sensors 200 to align the turntable 106 before transferring the carrier 112 to the turntable 106. Figure 2A In the exemplary embodiment depicted in FIG, a pair of alignment sensors 200 are located on the exterior components of the turntable mounting rail 110 and the OHT rail 104 .

[0027] According to some embodiments of the present disclosure, the alignment sensor 200 used can have a small form factor so as not to unduly obstruct the rails 104 of the OHT 102 and / or the rails 110 of the turntable 110 and / or obstruct the transport of the carrier 112 along the rails 104, 110. In some embodiments, the alignment sensor 200 can be implemented as a pair of optical sensors to ensure proper alignment of the fixed rail 110 with the rails 104 of the main rail section 124. It should be understood that other types of alignment sensors can be used, including, for example, but not limited to, electromechanical sensors (e.g., limit switches), image sensors (e.g., charge-coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors), or the like. Misalignment of these sensors 200 can be detected by the controller 108 to prevent damage or interference to the carrier 112, wafer carriers, personnel beneath the OHT 102, and the like during transport of the carrier 112, as discussed in more detail below.

[0028] Figure 2A Further shown are brake sensors 202 located on the track 104 of the main track section 124 and on the track 104 of the first vertical track section 126 and the second vertical track section 128. The brake sensors 202 may be implemented using electromechanical, optoelectronic, proximity, or other types of sensors. In some embodiments, optical or imaging sensors are used to detect when the vehicle 112 applies the brakes before passing the turntable 106, or, if traveling / moving in a direction perpendicular to the turntable track 110, stops when the vehicle 112 maintains a suitable distance from the turntable 106 on the track 114 of the first vertical section 126 or the second vertical section 128. In various embodiments, the suitable distance may be, for example, but not limited to, 1 to 3 meters from the turntable 106 to avoid any congestion during restart, allow for a suitable safety distance to stop the vehicle 112, and prevent any damage to the vehicle 112 during the rotation of the turntable 106. The rotation of the turntable 106 can be achieved by, for example, but not limited to, a stepper motor, a service motor, a gear-driven motor, hydraulic control, magnetic control, pneumatic operation, or any other suitable combination. It should be understood that the size of the turntable 106 can depend on the distance between the tracks 104 of the OHT, the size of the tracks 104 on the OHT 102, the distance between the cross tracks 122, etc.

[0029] Those skilled in the art will appreciate that the OHT 102 and the AMHS system 100 may utilize various other types of sensors (not shown) to collect data related to the operation of the OHT 102 and / or the AMHS system 100. Such sensors may include sensors for identifying incoming vehicles 112 (e.g., radio frequency identification (RFID) sensors) and other sensors for describing the performance of incoming vehicles 112 (e.g., acoustic sensors, vibration sensors, or imaging sensors). As another example, different sensors may be utilized in conjunction with other vehicles 112 on the OHT 102 to monitor the performance of incoming vehicles. For example, acoustic sensors may be used to determine the time it takes for a vehicle to approach from one point to another, and acoustic sensors may be used to determine the characteristics of the sound or vibration generated by incoming vehicles. This sensor data can be compared to better describe the performance of vehicles over time and cross-referenced to improve sensing accuracy. Furthermore, by cross-referencing sensor data, sensor anomalies can be detected and corrected (e.g., repaired or replaced) at or before sensor failure.

[0030] exist Figure 2B In FIG, the turntable 106 has been rotated from the first operating direction to the second operating direction, that is, the carrier 112 can now go directly from the first vertical track section 126 to the second vertical track section 128, thereby bisecting the main track section 124 of the OHT. Figure 2B , the second direction of travel is illustrated as being perpendicular to the main track segment 124, enabling the carrier 112 to move directly from the first track segment 126 to the second track segment 128. As shown, the fixed track 110 on the turntable 106 is aligned with the tracks 104 of the first vertical segment 126 and the second vertical segment 128 of the OHT 102 in the second direction of travel. Figure 2A Discussion, Figure 2B The turntable 106 shown in FIG utilizes the alignment sensor 200 and the brake sensor 202 in a similar manner. However, in FIG. Figure 2B In the example, the vehicles 112 transferred on the main track section 124 are directed to activate their respective brakes based on the output of the brake sensor 202 , thereby allowing the transfer of the vehicles directly to and from the first vertical section 126 and the second vertical section 128 .

[0031] Figure 3A 、 Figure 3B and Figure 3C Another embodiment of a turntable 300 according to the systems and methods described herein is shown. In particular, Figure 3A-3CA turntable 300 is depicted as being implemented at the intersection of three sets of tracks 104, with a first operating direction 302, a second operating direction 304, and a third operating direction 306 being shown. Those skilled in the art will appreciate that the depiction of three operating directions 302-306 is intended merely as an example, and that other operating directions, such as 2, 3, 4, 5, 6, etc., can also be implemented according to various embodiments of the present disclosure. That is, depending on the size of the AMHS system 100 and the OHT 102, the turntable 300 can be placed at the intersection of multiple operating directions to facilitate transport operation management of the vehicle 112.

[0032] exist Figure 3A , turntable 300 is shown as allowing vehicle 112 to pass in a first travel direction 302 , ie, a zero degree turn (home direction). Figure 3B The turntable is shown rotated 90 degrees, allowing the vehicle 112 to pass in the second traversing direction 304. Figure 3C The turntable is illustrated as rotating 45 degrees to allow the vehicle 112 to pass in the third traversing direction 306. The rotation of the turntable 300 varies depending on the orientation of the track 104 in the travel directions 302, 304, and 306, with 0° representing the first travel direction 302, 60° representing the second travel direction 304, and 180° representing the third travel direction 306. Those skilled in the art will appreciate that the rotation angle of the turntable 300 is determined not only by the positions of the various travel directions 302-306, but also by the number of travel directions, the size of the turntable, the size of the track 104, and the like.

[0033] It should be understood by those skilled in the art that Figure 3A-3C The turntable 300 shown in FIG can be used with a similar Figure 2A-2B In such an embodiment, the alignment sensor 200 and the brake sensor 202 may be positioned on each track 104 in the travel directions 302-306. Figure 3A-3C However, the skilled person will understand that Figure 3A-3C The position and function of the sensors 200, 202 in the Figure 2A-2B The situation in .

[0034] return Figure 1The AMHS system 100 also includes an AMHS / OHT controller 108 that communicates via communication lines 130 with the turntable 106, the carrier 112, the various sensors 200-202, the stocker 114, the process tool 116, and numerous other component devices (not shown) coupled to or forming part of the AMHS system and / or OHT 102. Those skilled in the art will appreciate that, although shown as a single device, the AMHS / OHT controller 108 may be implemented in a distributed manner, wherein multiple electronic data processing devices collaborate to perform the functions described herein. Figure 1 The communication lines 130 shown in FIG. 1 may be any suitable wired or wireless communication means, including, for example, but not limited to, a public switched telephone network, a proprietary communication network, infrared light, optical, or other suitable wired or wireless data communication. In some embodiments, the various components of the AMHS system 100 communicate with a distributed computing environment, such as a local area network, a wireless local area network, a virtual private network, a wide area network, or the like. According to various embodiments discussed herein, the functions and controls provided by the AMHS / OHT controller 108 are similar to those provided by the AMHS / OHT controller 108. Figure 4 Combining will provide better understanding.

[0035] Figure 4 An illustrative block diagram of a suitable AMHS / OHT controller 108 according to one embodiment of the present disclosure is shown. The various components in the AMHS / OHT controller 108 can be connected via a data / control bus 408. The processor 402 of the AMHS / OHT controller 108 communicates with an associated database 420 via a line 414. A suitable communication line 414 may include, for example, a public switched telephone network, a proprietary communication network, infrared light, optical, or other suitable wired or wireless data communication. The database 420 can be implemented on a component of the AMHS / OHT controller 108, for example, stored in a local memory 404, i.e., on a hard disk, a virtual disk, or the like, or in a remote memory accessible to the AMHS / OHT controller 108.

[0036] The associated database 420 represents any organized collection of data used for one or more purposes (e.g., batch information, shipping flow information, process tool information, vehicle status information, manufacturing information, material information, one or more lookup tables and translation information, etc.). Those skilled in the art will appreciate that such information can be updated via machine learning during operation of the primary AHMS system 100. The associated database 420 can be implemented on any mass storage device, such as a magnetic storage device, a hard drive, an optical storage device, a flash memory device, or a suitable combination thereof. The associated database 420 can be implemented as a component within the AMHS / OHT controller 108, such as in the permanent memory 404 or the like. In one embodiment, the associated database 420 may include data corresponding to production schedules, OHT information, vehicle information (e.g., speed, location, status, etc.), batch information, priority information, etc.

[0037] The AMHS / OHT controller 108 may include one or more input / output (I / O) interface components 422 and 424 for communicating with external components. The I / O interface component 424 may communicate with one or more of the display devices 416 via the communication line 412. This may be used to display information, such as an estimated destination; to input information to a user input device 418, such as a keyboard or a touch or writable screen; to input text and / or a cursor control component, such as a mouse, trackball, or the like, to convey user input information and command selections to the processor 402. The I / O interface component 422 may communicate with external components, such as the carrier 112, the turntable 106, the stocker 114, the process tool 116, the alignment sensor 200, and the brake sensor 202, via the communication line 130.

[0038] It should be understood that Figure 4 The AMHS / OHT controller 108 shown in FIG can be implemented using a distributed computing environment (e.g., a computer network), which is representative of any distributed communication system that enables data exchange between two or more electronic components. It will be further understood that such a computer network includes, for example, but not limited to, a virtual local area network, a wide area network, a personal area network, a local area network, the Internet, an intranet, or any other suitable combination. Thus, such a computer network includes a physical layer and a transport layer, as shown in various conventional data transmission mechanisms, such as, but not limited to, a token ring network, an Ethernet network, or other wireless or wired based data communication mechanisms. In addition, although in Figure 4 Although described herein as a set of networked components, the AMHS / OHT controller 108 can be implemented on a standalone device to interact with the AMHS system 100 and / or OHT 102 described herein.

[0039] The AMHS / OHT controller 108 may include one or more of a computer server, a workstation, a personal computer, a mobile phone, a tablet computer, a pager, combinations thereof, or other computing components capable of executing instructions to perform the exemplary method.

[0040] According to an exemplary embodiment, the AMHS / OHT controller 108 includes hardware, software, and / or any suitable combination thereof, configured to interact with an associated user, networked device, networked storage device, remote device, or other similar device.

[0041] exist Figure 4 The memory 404 as a component of the AMHS / OHT controller 108 can represent any type of non-transitory computer-readable media, such as random access memory (RAM), read-only memory (ROM), disk or tape, optical disk, flash memory or holographic memory. In one embodiment, the memory 404 comprises a combination of random access memory and read-only memory. In certain embodiments, the processor 402 and the memory 404 can be merged into a chip. Network interface components 422, 424 allow the computer to communicate with other devices through a computer network, and can include a modulator / demodulator (MODEM). The memory 404 can store data processed in the storage processing method and instructions for executing the illustrative method.

[0042] The digital processor 402 can be implemented in various ways, such as being composed of a single-core processor, a dual-core processor (or more generally a multi-core processor), a digital processor and an arithmetic coprocessor, a digital controller, etc. In addition to controlling the operation of the AMHS / OHT controller 108, the digital processor 402 executes instructions 406 stored in the memory 404 to perform the methods described below.

[0043] like Figure 4As shown, the instructions 406 stored in the memory 404 may include a sensor assembly 426 configured to receive and output from one or more sensors, such as the alignment sensors 200 and / or the brake sensors 202 from the OHT 102. In some embodiments, the sensor assembly 426 is configured to determine, based on the received output, whether each pair of alignment sensors 200 is properly aligned, thereby indicating that the turntable 106 is properly aligned to allow the vehicle 112 to traverse the track 110 of the turntable 106. When the output from the alignment sensors 200 indicates that one or more sensors 200 are misaligned, the sensor assembly 426 may generate feedback to the processor 402 to further rotate the turntable 106, activate the brake sensors 202 to stop the vehicle 112 at or near the turntable 106, generate a warning / alarm indicating misalignment, etc. The sensor assembly 426 may further be configured to receive output from the brake sensors 202 indicating a stall condition of the vehicle 112 approaching the turntable 106.

[0044] The instructions 406 stored in the memory 404 of the AMHS / OHT controller 108 may also include an orientation component 428 for determining the current orientation of the turntable 106 relative to the track 104 of the OHT 102. In other words, the orientation component 428 may be configured to sense whether the track 110 of the turntable 106 is in the first operating direction ( Figure 2A ) or the second direction of operation ( Figure 2B ) in the current location.

[0045] The memory 404 of the AMHS / OHT controller 108 may further store, within instructions 406, a timing component 430 configured to set and determine appropriate time sequences for activating the brakes on the vehicle 112 based on the brake sensor 202, setting the time to begin rotating the turntable 106 based on the determined direction of travel, and the like. In some embodiments, the timing component 430 may be configured to receive output from the sensor component 428 regarding the time required for the vehicle 112 to stop, move across the turntable 106, and the like. Those skilled in the art will appreciate that, according to other embodiments contemplated herein, other timing aspects of the operation of the AMHS system 100 and OHT 102 may also be collected, processed, and utilized via the timing component 430. The memory 404 further stores instructions 406 including a rotation component 432 operable to control the rotation of the turntable 106 based on the desired direction of travel. In various embodiments, the rotation assembly 432 can utilize a pre-programmed rotation sequence to rotate the turntable according to a schedule determined by the production schedule of the AMHS system 100, the availability of the process tool 116, the number of carriers 112 available or operable on the OHT 102, etc. Such a rotation sequence can be stored in an associated database 420 and called based on the output of a timing assembly, a sensor assembly, etc. In some embodiments, the rotation assembly 432 can cooperate with the orientation assembly 428 to ensure that the turntable 106 is correctly rotated to the required angle of rotation, such as 0°, 30°, 45°, 60°, 90°, 180°, 270°, etc., and the direction of such rotation, such as clockwise or counterclockwise, as required by the AMHS system 100.

[0046] The instructions 406 stored in the memory 404 also include a transport component 434, which is configured to detect transport conditions, i.e., the movement and congestion of the carrier 112 on the OHT102, the position of the carrier 112, speed, etc. In some embodiments, the transport component 434 and the sensor component 426 can communicate with each other to receive outputs related to the passage and position of the carrier 112. The transport component 434 can also communicate with the orientation component 428 to receive outputs from the component, which can indicate the direction of the turntable 106, i.e., the running direction of the turntable 106 currently positioned. In addition, the transport component 434 can communicate with the rotation timing component 430 and the rotation component 432 to receive timing information and send rotation information between them. In different embodiments contemplated herein, the transport component 434 can utilize machine learning to identify the appropriate time during production and carrier movement to realize the rotation of the turntable 106, to reduce carrier congestion and / or improve the production of the AMHS system 100.

[0047] The term "software" as used herein is intended to encompass any set or group of instructions executable by a computer or other digital system to configure the computer or other digital system to perform the tasks for which the software is intended. The term "software" as used herein is intended to encompass instructions stored in storage media (e.g., random access memory, hard disk, optical disk, etc.), and is also intended to include so-called "firmware" stored on storage media, i.e., software stored on ROM, etc. Such software may be organized in various ways and may include software components organized in libraries, Internet programs stored on remote servers, source code, interpreted program code, object code, and directly executable program code, etc. As intended, the software may call system-level program code or call other software resident on a server or other location to perform certain functions. In combination Figure 5 and Figure 6 The operation of the AMHS / OHT controller 108 will be better understood with reference to the exemplary methods set forth in FIG.

[0048] Figure 5 An exemplary method 500 for AMHS / OHT track control according to one embodiment of the present disclosure is shown. Method 500 begins at 502, where the AMHS / OHT controller 108 receives a request to change the direction of travel of the turntable 106 from a first direction of travel to a second direction of travel. In some embodiments, the request is received by the transport component 434 based on the current traffic flow conditions on the OHT 102. In other embodiments, the command is received based on a pre-planned change in traffic flow. In yet another embodiment, the request is received from an external source, such as a transportation control center (not shown) in communication with the AMHS / OHT controller 108. In such an embodiment, the request can be an automatic or manual input, that is, an operator monitoring the AMHS system 100 can request to change the direction of travel of the turntable 106.

[0049] At 504, the transport assembly 434 is coupled to the sensor assembly 426 to engage the brake sensor 202 near the turntable 106 to stop transport, i.e., to stop the movement of the vehicle 112 through the turntable 106. According to an embodiment, the vehicle 112 may receive a command from the AMHS / OHT controller 108 instructing the vehicle 112 to apply the brakes to stop operation before or at the location of the brake sensor 202. According to some embodiments contemplated herein, all vehicles 112 traveling in the first direction of operation are cleared prior to engaging the brake sensor 202, i.e., they are allowed to complete their operation across the turntable 106 prior to engaging the brake sensor 202. The turntable 106 then begins to rotate at 506 according to the desired setting, i.e., clockwise or counterclockwise and the degree of rotation, thereby moving the turntable 106 from the first operating position ( Figure 2A ) moves to the second operating position ( Figure 2B ).

[0050] At 508, orientation assembly 428 receives an indication that the transition from the first direction of travel to the second direction of travel has been completed. In some embodiments, this indication may be received directly from turntable 106, via sensor assembly 426 in conjunction with the output of alignment sensor 200, or other suitable combinations. Transport assembly 434 engages sensor assembly 426 and then signals brake sensor 202 at 510 to disengage. Thereafter, at 512, vehicle 112, which was stopped near turntable 106, is instructed to continue moving and can now pass directly in the second direction of travel.

[0051] refer to Figure 6 Another embodiment of a method 600 for AMHS track control according to the present disclosure is shown. Method 600 begins at 602, where the AMHS / OHT controller 108 receives a request to change the direction of travel of the turntable 106 from a first direction of travel to a second direction of travel. In some embodiments, the request is received by the transport component 434 based on the current traffic flow conditions on the OHT 102. In other embodiments, the command is received based on a pre-planned change in traffic flow. In yet another embodiment, the request is received from an external source, such as a transportation control center (not shown) that communicates with the AMHS / OHT controller 108. In this embodiment, the request can be an automatic or manual input, i.e., an operator monitoring the AMHS system 100 can request to change the direction of travel of the turntable 106.

[0052] At 604, any carrier 112 moving in the first operating direction is cleared, i.e., the carrier 112 passes the turntable 106. After clearing at 604, the operation proceeds to 606, at which time the transport assembly 434 is combined with the sensor assembly 426 to engage the brake sensor 202 near the turntable 106 to stop the transport through the turntable 106, i.e., the movement of the carrier 112. According to an embodiment, the carrier 112 can receive a command from the AMHS / OHT controller 108 instructing the carrier 112 to apply the brakes to stop the movement before or at the position of the brake sensor 202. The turntable 106 then begins to rotate at 608 according to the desired settings, i.e., clockwise or counterclockwise and the degree of rotation, thereby moving the turntable 106 from the first operating position ( Figure 2A ) moves to the second operating position ( Figure 2B ).

[0053] At 610, the orientation assembly 428 receives an indication that the conversion from the first operating direction to the second operating direction has been completed. According to one embodiment, the orientation assembly 428, which serves as a safety interlock device, confirms that the conversion / rotation from the first operating direction to the second operating direction has been completed by aligning the sensor 200. In some embodiments, the turntable 106 sends back a conversion completion signal to the AMHS / OHT controller 108, indicating that the turntable 106 has successfully changed its direction to the second operating direction. Thereafter, at 612, the transport assembly 434 cooperates with the sensor assembly 426 and transmits a disable signal to the brake sensor 202 to disengage it. At 614, the vehicle 112 parked near the turntable 106 is instructed to continue moving and can now pass directly in the second operating direction.

[0054] refer to Figure 7 Another embodiment of the method 700 of AMHS track control according to the present disclosure is shown. Method 700 starts at 702, wherein AMHS / OHT controller 108 receives the request that the running direction of turntable 106 is changed from the first running direction to the second running direction. In this embodiment, turntable 106 is equipped with a power supply, a power supply switch, a plurality of safety interlocks (alignment sensors 200) and a plurality of brake sensors 202 for OHT 102. Then, AMHS / OHT controller 108 sends a signal to turntable 106 at 704, causing it to change direction, changing direction from the first running direction to the second running direction. At 706, any carrier 112 moving in the first running direction is cleared, i.e., completing the transportation across turntable 106. At 708, brake sensor 202 is activated to prevent any carrier from crossing turntable 106. At 710, the power supply of OHT 102 is disabled. According to such an embodiment, the power supply of the carrier 112 that has been stopped on the OHT 102 is disabled by the AMHS / OHT controller 108. Any carrier 112 that is in proximity to the turntable 106 on the OHT 102 is therefore stopped at 712 by a command transmitted to the carrier 112 by the controller 108. At 714, the turntable 106 begins to rotate from the first operating direction to the second operating direction.

[0055] At 716, the AMHS / OHT controller 108 receives an output from the alignment sensor 200 (i.e., a safety interlock) regarding the alignment of the turntable 106 relative to the track 104 of the OHT 102. A determination is then made at 718 as to whether the turntable 106 has successfully rotated and aligned the turntable track 104 with the track 104 of the OHT 102 in the second operating direction. Following a negative determination at 718, the operation proceeds to 720, where an alarm is generated to indicate misalignment. Thereafter, at 722, based on the output of the alignment sensor 200, the turntable 106 makes a second alignment attempt to rotate to the target position. A determination is then made at 724 as to whether the second alignment attempt was successful. Following a negative determination at 724, the operation proceeds to 726, where a signal is transmitted to a technician or other appropriate personnel associated with the AMHS system 100.

[0056] When it is determined at 724 or 718 that the rotation and alignment have been confirmed, the operation proceeds to 728, where the OHT power supply is enabled. At 730, the brake sensor 202 is disabled by the AMHS / OHT controller 108. Thereafter, at 732, the carrier 112, which was previously stopped before passing through the turntable 106, is allowed to move through the turntable 106 in the second operating direction.

[0057] According to a first embodiment, a method for AMHS track control is provided, comprising receiving, at a controller including a processor in communication with a memory, a request for a turntable on an OHT of the AMHS to rotate from a first operating direction to a second operating direction. The method further comprises engaging at least one brake sensor located near the turntable and rotating the turntable from the first operating direction to the second operating direction. Furthermore, the method further comprises disengaging at least one brake in response to the turntable rotating from the first operating direction to the second operating direction. In some embodiments, the method further comprises stopping at least one vehicle located on the OHT near the turntable in response to engaging at least one of the brakes. In some embodiments, the method further comprises receiving a signal from at least one alignment sensor regarding alignment of the turntable with the OHT. In some embodiments, the step of disengaging at least one of the brakes is responsive to receiving a signal from an alignment sensor. In some embodiments, the step of engaging at least one of the brake sensors further comprises sending a command to at least one vehicle to stop operation. In some embodiments, the method further comprises receiving a signal from the turntable indicating that the rotation is complete, wherein the step of disengaging at least one of the brakes is responsive to receiving the signal indicating that the rotation is complete. In some embodiments, the method further comprises removing at least one vehicle from traveling in the first direction of travel before engaging at least one of the brake sensors. In some embodiments, stopping at least one of the vehicles further comprises disabling a power supply associated with the OHT. In some embodiments, the method further comprises activating the power supply associated with the OHT in response to an output of at least one alignment sensor. In some embodiments, the method further comprises generating an alarm in response to the output of at least one alignment sensor to indicate that the turntable is not aligned.

[0058] According to a second embodiment, a track management system is provided, comprising an overhead transport (OHT) system associated with an automated material handling system (AMHS), the system comprising a plurality of fixed tracks within a semiconductor manufacturing facility, and at least one vehicle configured to travel along the plurality of fixed tracks. The system further comprises a controller including a processor in communication with a memory, the controller being in electronic communication with the OHT system. The track management system further comprises a turntable having a set of fixed tracks disposed thereon, the turntable being located on a portion of the OHT. The memory in communication with the processor is configured to store instructions, executable by the processor, for causing the processor to receive a request to rotate the turntable from a first operating direction to a second operating direction and engage at least one brake sensor proximate to the turntable. The memory further stores instructions, executable by the processor, for rotating the turntable from the first operating direction to the second operating direction and disengaging at least one brake in response to the turntable rotating from the first operating direction to the second operating direction. In some embodiments, the track management system further comprises at least one alignment sensor aligned proximate to the turntable, the alignment sensor being configured to generate a signal associated with aligning the turntable with the OHT. In some embodiments, the memory further stores the instructions for stopping at least one of the vehicles located on the OHT and proximate to the turntable in response to engaging at least one of the brakes. In some embodiments, the OHT comprises a first vertical track segment, a second vertical track segment, and a main track segment, wherein the first vertical track segment and the second vertical track segment are located on opposite sides of the main track segment. In some embodiments, the first operating direction corresponds to the main track segment, and wherein a set of the fixed rails on the turntable are aligned with rails of the main track segment. In some embodiments, the turntable is aligned for a second operating direction to and from a first vertical track segment and a second vertical track segment, wherein the set of fixed rails on the turntable are aligned with the first vertical track segment and the second vertical track segment. In some embodiments, the turntable is configured to rotate from the first operating direction to the second operating direction, and from the second operating direction to a third operating direction.

[0059] According to a third embodiment, a computer-implemented method is provided for managing transport of a vehicle track on an automated material transport system including an overhead transport (OHT) system. The method includes receiving a request to rotate a turntable on an overhead transport (OHT) system of an automated material transport system (AMHS) from a first operating direction to a second operating direction. The method also includes clearing at least one vehicle traveling in the first operating direction from passing through the turntable and engaging at least one brake sensor proximate to the turntable. Furthermore, the method includes communicating a stop signal to each of a plurality of vehicles traveling toward the turntable and rotating the turntable from the first operating direction to the second operating direction. Furthermore, the method includes receiving a transition completion signal from the turntable confirming the rotation from the first operating direction to the second operating direction based on outputs from a plurality of alignment sensors. The method also includes disengaging at least one brake in response to the rotation of the turntable from the first operating direction to the second operating direction. In some embodiments, the computer-implemented method further includes communicating with each of the plurality of vehicles to stop the vehicle and disabling a power supply associated with the OHT. In some embodiments, the computer-implemented method further includes enabling the power supply associated with the OHT in response to the outputs of the plurality of alignment sensors.

[0060] Some portions of the detailed description herein are presented in terms of algorithms and symbolic representations of operations on data bits performed by conventional computer components, including a central processing unit (CPU), memory storage for the CPU, and an attached display device. These algorithmic descriptions and representations are the most effective means used by those skilled in the data processing arts to convey the substance of their work to others skilled in the art. Generally speaking, an algorithm is considered to be a self-consistent sequence of steps leading to a desired result. These steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It is evident that these signals are sometimes referred to, primarily for reasons of common usage, as bits, values, elements, symbols, characters, terms, numbers, or the like.

[0061] It should be understood, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels for applying to these quantities. Unless otherwise indicated, it will be apparent from the discussion herein that throughout this description, discussions using terms such as "process" or "compute" or "determine" or "display" refer to the actions and processes of a computer system or similar electronic computing component that operates on and transforms data represented as physical (electronic) quantities in the computer system's buffers and memories into other data similarly represented as physical quantities in the computer system's memory or buffers or other such information storage, transmission, or display devices.

[0062] Exemplary embodiments also relate to an apparatus for performing the operations discussed herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored on a computer-readable storage medium, such as, but not limited to, any type of storage disk, including floppy disks, optical disks, CD-ROMs and magnetic disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any other type of medium suitable for storing electronic instructions, and may be coupled to a computer system bus.

[0063] The algorithms and displays described herein are not inherently related to any particular computer or other device. Various general-purpose systems may be used with programs consistent with the teachings herein, or it may prove convenient to construct more specialized equipment to perform the methods described herein. The various structures in these systems are apparent from the above description. Furthermore, the exemplary embodiments are not described with reference to any particular programming language. It should be understood that the teachings of the exemplary embodiments described herein may be implemented using a variety of programming languages.

[0064] Machine-readable media includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, machine-readable media includes read-only memory ("ROM"); random-access memory ("RAM"); magnetic disk storage media; optical storage media; flash memory components; and electrical, optical, acoustical, or other propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), to name a few.

[0065] The methods described throughout this specification can be implemented in a computer program product, which can be executed on a computer. The computer program product can include a non-transitory computer-readable recording medium, such as a magnetic disk or hard disk, that records the control program. Common forms of non-transitory computer-readable media include, for example, magnetic disks, floppy disks, hard disks, magnetic tapes, or any other magnetic storage media, CD-ROMs, DVDs, or any other optical media, random access memory, PROMs, EPROMs, FLASH-EPROMs, or other memory chips or cartridges, or any other tangible media that can be read and used by a computer.

[0066] Alternatively, the method may be implemented in a transient medium, such as a transmissive carrier wave, wherein the control program is implemented using the transmission medium as a data signal, such as acoustic or light waves, such as those generated during data communications over radio waves and infrared, etc.

[0067] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the present disclosure. Those skilled in the art will understand that they can easily use this disclosure as a basis for designing or modifying other processes and structures to perform the same purposes and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also recognize that these equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and modifications thereto without departing from the spirit and scope of the present disclosure.

[0068] [Explanation of Symbols]

[0069] 100: AMHS system

[0070] 102: Overhead Transport (OHT) System

[0071] 104, 110, 122: Track

[0072] 106, 300: Turntable

[0073] 108: Controller

[0074] 112: Vehicle

[0075] 114: Wafer storage machine

[0076] 116: Tools

[0077] 118, 124, 126, 128: Segments

[0078] 130, 412, 414: Lines

[0079] 200, 202: Sensor

[0080] 302, 304, 306: Direction

[0081] 402: Processor

[0082] 404: Memory

[0083] 406: Instruction

[0084] 408: Bus

[0085] 416: Display device

[0086] 418: User input device

[0087] 420: Database

[0088] 422, 424: Interface components

[0089] 426: Sensor Components

[0090] 428: Directional Component

[0091] 430: Timing Components

[0092] 432: Rotating Component

[0093] 434: Transport components

[0094] 500, 600, 700: method.

Claims

1. A track control method for an automated material transportation system, characterized in that: include: receiving, at a controller including a processor in communication with a memory, a request to rotate a turntable on an overhead transport of the automated material handling system from a first operating direction to a second operating direction, the turntable including a set of fixed tracks, wherein when the turntable is in a first position, the fixed tracks are aligned with tracks of a first fixed track section located at an intersection aligned with the first operating direction, and when the turntable is in a second position, the fixed tracks are aligned with tracks of a second fixed track section located at the intersection aligned with the second operating direction; Before rotating the turntable, clearing at least one first vehicle traveling in the first direction of travel, allowing the at least one first vehicle to complete travel across the turntable; before rotating the turntable and after clearing the at least one first vehicle, engaging at least one first brake sensor located on a track of the first fixed track section and proximate the turntable so that a brake of each of at least one subsequent first vehicle located on the track of the first fixed track section is actuated in response to an output of the first brake sensor to stop the at least one subsequent first vehicle before passing the turntable; prior to rotating the turntable, engaging at least one second brake sensor located on the track of the second fixed track section and proximate the turntable so that a respective brake of at least one second vehicle located on the track of the second fixed track section is actuated in response to an output of the second brake sensor to stop the at least one second vehicle before the vehicle passes the turntable; rotating the turntable from the first operating direction to the second operating direction and receiving an alignment signal regarding the turntable relative to the track of the second fixed track section from at least one pair of alignment sensors located on the turntable and proximate to the turntable on the track of the second fixed track section; as well as In response to the alignment signal indicating that the turntable rotates from the first operating direction to the second operating direction, the at least one second brake sensor is disabled to disengage the brake to allow the stopped at least one second vehicle to continue to move along the track of the second fixed track section to pass the turntable in the second operating direction.

2. The method according to claim 1, characterized in that The step of engaging at least one of the brake sensors further includes sending a command to at least one vehicle to stop operation.

3. The method according to claim 1, characterized in that The method further includes receiving a shift complete signal from the rotary disk, wherein the step of disengaging the brake is responsive to receiving the shift complete signal.

4. The method according to claim 1, wherein Wherein stopping at least one of the vehicles further comprises disabling a power supply associated with the overhead transport.

5. The method according to claim 4, characterized in that The method further includes activating the power supply associated with the overhead transport in response to an output of at least one alignment sensor.

6. The method according to claim 1, characterized in that The method also includes generating an alarm in response to an output of at least one alignment sensor to indicate that the turntable is not aligned.

7. A track management system, characterized in that: include: An overhead transport system of a relational automated material transport system includes a plurality of fixed tracks and at least one vehicle configured to travel along the plurality of fixed tracks; a controller including a processor in communication with a memory, said controller being in electronic communication with said overhead transport system; a turntable, a set of fixed rails being provided above the turntable, the turntable being located on a portion of the elevated transport, the fixed rails being aligned with rails of a first fixed rail section located at an intersection aligned with a first running direction when the turntable is in a first position, and being aligned with rails of a second fixed rail section located at the intersection aligned with a second running direction when the turntable is in a second position; The memory further stores instructions, which, when executed by the processor, cause the processor to: receiving a request to rotate the turntable from the first operating direction to the second operating direction; Before rotating the turntable, clearing at least one first vehicle traveling in the first direction of travel, allowing the at least one first vehicle to complete travel across the turntable; before rotating the turntable and after clearing the at least one first vehicle, engaging at least one first brake sensor located on a track of the first fixed track section and proximate the turntable so that a brake of each of at least one subsequent first vehicle located on the track of the first fixed track section is actuated in response to an output of the first brake sensor to stop the at least one subsequent first vehicle before passing the turntable; Prior to rotating the turntable, engaging at least one second brake sensor located on the track of the second fixed track section and proximate the turntable so that a respective brake of at least one second vehicle on the track of the second fixed track section is actuated in response to an output of the second brake sensor to stop the at least one second vehicle before passing the turntable; rotating the turntable from the first operating direction to the second operating direction and receiving an alignment signal regarding the turntable relative to the track of the second fixed track section from at least one pair of alignment sensors located on the turntable and proximate to the turntable on the track of the second fixed track section; and In response to the alignment signal indicating that the turntable rotates from the first operating direction to the second operating direction, the at least one second brake sensor is disabled to disengage the brake to allow the stopped at least one second vehicle to continue to move along the track of the second fixed track section to pass the turntable in the second operating direction.

8. The track management system according to claim 7, characterized in that: The first fixed track section is perpendicular to the second fixed track section.

9. The track management system according to claim 8, characterized in that: Wherein the first running direction corresponds to a main track section, and wherein the fixed track on the turntable is aligned with a track of the main track section.

10. The track management system according to claim 7, characterized in that: The turntable is aligned in the second running direction so that the fixed track on the turntable is aligned with the track of the second fixed track section.

11. The track management system according to claim 7, characterized in that: The turntable is configured to rotate from the first running direction to the second running direction, and from the second running direction to a third running direction.

12. A computer-implemented method for managing vehicle track transport on an automated material transport system including an overhead transport system, characterized in that: The method comprises: receiving a request to rotate a turntable on the overhead transport of the automated material handling system from a first operating direction to a second operating direction, the turntable including a set of fixed tracks, the fixed tracks being aligned with tracks of a first fixed track section located at an intersection aligned with the first operating direction when the turntable is in a first position, and the fixed tracks being aligned with tracks of a second fixed track section located at the intersection aligned with the second operating direction when the turntable is in a second position; Before rotating the turntable, clearing at least one first vehicle traveling along the first running direction, allowing the at least one first vehicle to complete its travel across the turntable; before rotating the turntable and after clearing the at least one first vehicle, engaging at least one first brake sensor located on a track of the first fixed track section and proximate the turntable so that a brake of each of at least one subsequent first vehicle located on the track of the first fixed track section is actuated in response to an output of the first brake sensor to stop the at least one subsequent first vehicle before passing the turntable; prior to rotating the turntable, engaging at least one second brake sensor located on the track of the second fixed track section and proximate the turntable so that a respective brake of at least one second vehicle located on the track of the second fixed track section is actuated in response to an output of the second brake sensor to stop the at least one second vehicle before the vehicle passes the turntable; rotating the turntable from the first operating direction to the second operating direction and receiving an alignment signal regarding the turntable relative to the track of the second fixed track section from at least one pair of alignment sensors located on the turntable and proximate to the turntable on the track of the second fixed track section; receiving a completed transition signal from the turntable to confirm rotation from the first operating direction to the second operating direction based on the output of the at least one alignment sensor pair; and In response to the turntable rotating from the first operating direction to the second operating direction, the at least one second brake sensor is disabled and the at least one second vehicle that has stopped operating is instructed to continue moving along the track of the second fixed track section to pass the turntable in the second operating direction.

13. The computer-implemented method of claim 12, wherein: Stopping the at least one subsequent first carrier further includes disabling a power supply associated with the at least one subsequent first carrier.

14. The computer-implemented method of claim 12, wherein: The computer-implemented method further includes enabling a power supply associated with the subsequent at least one first carrier in response to an output of the at least one alignment sensor pair.

Images