A system and a method for sorting products, wherein said system and method is directed to an efficient communication topology

Abstract

A system for sorting products comprising a plurality of controllers, wherein each controller is provided on at least a combination of an elongated carrying body and a pusher body, configured for carrying the products to be sorted. The plurality of controllers is arranged to control at least a displacing devices in turn moving the pusher body pushing the product off of the elongated carrying body. The system further comprises at least one stationary Access Point, AP, arranged to send and receive packets comprising commands for the displacing device to one or more of said plurality of controllers, wherein the plurality of controllers are each arranged to only send a packet to said AP triggered by receipt of a packet from said AP and wherein said AP is arranged to send at least two packets after one another, before await response packets.

Description

[0001] TITLE

[0002] A system and a method for sorting products, wherein said system and method is directed to an efficient communication topology.

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a system and a method for sorting products having an improved wireless communication topology between at least one stationary Access Point, AP, and a plurality of moving controllers.

[0005] BACKGROUND OF THE DISCLOSURE

[0006] The present disclosure relates generally to the conveying and diverting of articles and, more particularly, to a conveyor having individually motorized transport elements to transport conveyed articles across the conveyor, like a system as described in EP3826947B1.

[0007] Typical sorting or article-diverting conveyor systems include a conveyor, such as an endless chain comprising elongated carrying bodies, having pusher bodies for pushing articles across the conveyor. These elongated carrying bodies are provided with a displacing device for moving the pusher body in a sorting direction along the carrying body. These displacing devices are programmed with movement trajectories and speeds of which the pusher bodies are to be laterally moved at specific points along the conveying path to divert the overlying articles to the correct output ramp.

[0008] Such conveyor system used to be “programmed” with a wheel that would follow a guide track underneath the conveyor belt. This however has the limitation that the “movement program” is fixed for every cycle of the conveyor belt.

[0009] Therefore, electric motors and individual controllers have been equipped on the elongated carrying bodies for variable programming of the pusher bodies. Such system, however, has the drawback that communication between the individual controllers and the “static” world, for example access points, needs to be defined. The communication principle needs to be robust and may have different type of latency requirements, for example depending on a type of data packet that is to be exchanged. The present disclosure is directed to a communication principle that addresses these needs.

[0010] SUMMARY OF THE DISCLOSURE

[0011] The disclosure pertains to a system for sorting products.

[0012] The system for sorting products comprises a plurality of controllers arranged to move along a closed loop trajectory and arranged for controlling the sorting of the products.

[0013] The system for sorting products also comprises at least one stationary Access Point, AP, arranged to send and receive packets to one or more of said plurality of controllers. The packets comprise commands for one or more of said plurality of controllers to control the sorting of the products. Moreover, the plurality of controllers are each arranged to only send a packet to said at least one AP triggered by receipt of a packet from said AP.

[0014] The at least one AP, also referred to as the AP for readability purposes, is arranged to send packets during a send period, and to receive packets during a receive period, wherein said send period and said receive period follow one another in time. The AP is arranged to send at least two packets during said send period to any of said plurality of controllers, and is arranged to wait, during said receive period, for responses to said at least two packets sent during said send period, from said any of said plurality of controllers.

[0015] The inventors of the present disclosure have found a beneficial way of communication between the static access point and the plurality of moving controllers as is elucidated here below.

[0016] The inventors have found that it may be beneficial to assure that the plurality of controllers are arranged to only send a packet to the AP if it they are triggered by a receipt of a packet from the AP. The advantage hereof is that a more controllable situation is obtained. This would prevent multiple, or even all, controllers to uncontrollably sent packets at the same time leading to multiple collisions and time delays in the system. Collisions may occur, for example, when multiple packets arrive at the AP at a same time. This may lead to one or more of those packets being dropped at the AP. In order to implement the above provided insight, the inventors have found to introduce so-called send periods and receive periods. The AP is arranged to send packets during a send period and the AP is arranged to receive packets during a receive period. The send period and the receive period follow each other in time.

[0017] In other words, the AP may send a packet, or multiple packets, to two or more controllers during the so-called send period. In the subsequent receive period, the AP may await responses to the packets that were sent in a previous sent period, as during a receive period a controller may respond to a packet that it has received from the AP.

[0018] One of the advantages of the communication mechanism explained above is that the wireless communication between the AP and the plurality of controllers is much more robust. The chances to a collision between packets is greatly reduced as the AP can control the congestion of the communication.

[0019] By defining consecutive send and receive periods, it is clear for the AP when it is allowed to send packets and when it is allowed to receive packets. During the receive period, the AP knows which of the plurality of controllers may communicate as those controllers have been addressed in the sent period preceding the receive period.

[0020] In the context of this disclosure, the term “packets” may be understood as either being a part of command or response message, or may be understood to be as a complete command or response message.

[0021] In a specific example, the system for sorting products comprises a number of combinations of an elongated carrying body and a pusher body, which combinations are located one after another and are movable in a direction of movement following a path along which a number of sorting locations are provided, wherein the elongated carrying bodies extend parallel to each other and perpendicular to the direction of movement and wherein the elongated carrying bodies are configured for carrying the products to be sorted, wherein the pusher body is arranged for pushing a product carried by the elongated carrying body off of the elongated carrying body towards any of the sorting locations.

[0022] Here, each combination may further be provided with a displacing device for moving the pusher body in a sorting direction along the carrying body, the sorting direction extending substantially perpendicularly to the direction of movement, for pushing said product carried.

[0023] On top of the above, each controller may be provided on at least one combination of the elongated carrying body and the pusher body, wherein each one of the plurality of controllers is arranged to control at least one of the displacing devices of at least said combination and / or neighboring combinations of the elongated carrying body and the pusher body.

[0024] It is noted that, typically, the length of a system may range from tens of meters to even hundreds of meters. Each of the elongated carrying bodies may be coupled to one another, or may be situated next to one another, to form a closed circuit. The result is that thousands of elongated carrying bodies may be provided, given typical dimensions for the elongated carrying body in the direction of movement, for example 50 to 200 mm. For example, in one example discussed with respect to the figures it is assumed that a system comprises 3200 elongated carrying bodies. Other possibilities may also be applicable, for example a system having 1600 or 2000 elongated carrying bodies.

[0025] Products to be sorted may be pushed onto, or placed on top of, the elongated carrying bodies. The dimensions of the elongated carrying bodies may be such that a product may span multiple consecutively situated elongated carrying bodies.

[0026] An elongated carrying body is provided with a pusher body, wherein the pusher body is able to move, with respect to the carrying body, in the sorting direction. An electric motor, for example a Direct Current, DC, motor, may be provided for each combination of elongated carrying body with its pusher body for moving the pusher body in the sorting direction along the carrying body. In operation, the pusher body is pushed against the product to be sorted such that the product to be sorted is pushed from its corresponding elongated carrying body.

[0027] As mentioned above, a product may span multiple consecutively situated elongated carrying bodies such that at least two pusher bodies are to be controlled together for pushing the product off of the corresponding elongated carrying bodies. It is noted that each single controller may control one single combinations of elongated carrying bodies and pusher bodies but is not limited thereto. For example, a single controller may control multiple combinations of elongated carrying bodies and pusher bodies. In this way, the number of controllers for the AP to communicate with is reduced, herewith communication becomes less demanding on the system.

[0028] The specifics of the number of combinations of elongated carrying bodies and pusher bodies per controller, and the number of controllers per system may depend on the requirements set by the operator of the system. For example, a system having only two sorting locations takes up less space and could suffice with only a handful of controllers, whereas a 200m sorting system with multiple sorting locations requires many tens of controllers.

[0029] In another example of the system for sorting products comprises a central manager arranged for construing said packets comprising said command for said one or more of said plurality of controllers based on sorting locations where products to be sorted should be pushed off of the carrying body.

[0030] Having a centralized manager allows the system for sorting products to operate within existing infrastructure.

[0031] A centralized manager may, for instance, communicate with a detection system, which detection system is arranged to determine the orientation of the product on the elongated carrying bodies or may be able to determine the sorting location based on a barcode or the like positioned on the product. This information can then be used by the system to define the motion, absolute and relative, of the pusher bodies and the sorting location, which can then be communicated to a particular controller or a group of controllers.

[0032] Another example of the system for sorting products is defined by a fixed duration of the receive period. Moreover, the system for sorting products could also be defined by a fixed duration of the send period.

[0033] Having a fixed receive period and / or having a fixed send period allows the system to operate effectively, since the periods have clearly defined bounds, which are known by all communicators in the system (AP and controllers). A fixed time period may result in some packets getting lost in the communication process due to spill over. The trade-off is, however, that the communication becomes more robust. In another example, the duration of the receive period is predetermined based on the number of packets sent during a preceding send period.

[0034] In this configuration the send and / or receive period are adjusted based on the number or, as an alternative or in addition thereto based on the size of the packets, that are sent during the send period. This configuration allows for variable time slicing of the send and receive periods and may thereby reduce spillovers.

[0035] In yet another example according to the disclosure, in the system for sorting products a duration of the receive period of the at least one AP is dynamic and lasts until all responses to the sent packets, sent in a corresponding send period preceding said receive period, are received or a maximum predetermined time has lapsed.

[0036] Here, the receive period may be dynamically adjusted. Once the AP has established that all expected responses have been received, the AP may decide to end the corresponding receive period. There is no need to further await any response, as all responses have already been received. This may save valuable time, and may thus reduce latency in the communication.

[0037] On top of the above, the AP may also dynamically adjust the sent period. Once the AP has established that all required packets have been sent, during the sent period, the AP may decide to end the corresponding sent period. There is no need to further prolong the sent period, as all required packets have already been sent. This may also save valuable time, and may thus reduce latency in the communication.

[0038] To circumvent having to wait indefinitely for a packet that might be lost during communication or a broken down controller, a maximum duration could be set as a time-out limit, both for the send period as well as for the receive period.

[0039] In a further example, a type of packet to be sent by said at least one AP is any of: a pre-sorter packet for indicating a position, where a pusher body at a corresponding carrying body should move to before receiving a corresponding product to be sorted; a position packet for indicating a position, where a pusher body at a corresponding carrying body should move to after receiving a corresponding product to be sorted; a profile packet for indicating a push profile over time for pushing a particular product off of a corresponding carrying body, said push profile indicates how a particular product is to be pushed over time; a go / no-go packet for indicating whether or not to push a particular product off of a corresponding carrying body; a status packet for requesting a status of a controller of said plurality of controllers.

[0040] Defining types of packets allows the system to organize and structure the communication. It further allows for prioritization. A go / no-go packet may, for example, be associated with a small latency compared to a status packet. The go / no- go packet indicates whether or not to push a particular product off of a corresponding carrying body and should, therefore, be received before the corresponding sorting location. This imposes latency requirements on the go / no-go packets.

[0041] In the example provided above, the defined packets may indicate a position or a push profile. In practice, this may be accomplished in a variety of ways. For example, to indicate a position a packet may comprise a profile related to an acceleration over time. This will result in a particular position for the corresponding pusher body. Another option is that relative, or absolute, positions are provided. Yet another option is that predefined positions are programmed, and that the corresponding packet comprises a “flag” for indicating that the corresponding pusher body is to move to a predefined position.

[0042] When to actually send the packets may be based on the type of packets, i.e. the prioritization of the packets.

[0043] As another example, a go / no-go packet could have a smaller character size than a profile packet, since less information is needed to be transferred. Having categories pre-defined allows the system to work within limits it is already designed for.

[0044] In an example, each of the at least one APs in the system for sorting products comprises a single packet queue comprising the packets to be sent by said at least one AP to any of the controllers, wherein the single packet queue is based on an order in which the packets have entered the queue, such that a First In First Out, FIFO, order is maintained. In this arrangement is it assured that the packets are sent based on the time they appear in the queue. In this way, no packet may remain in the queue for too long, since eventually it would end up as the next packet to be sent due to its lifetime in the queue.

[0045] As mentioned above, in another example, the packets may be placed in the queue based on the type of packet as the type of packet may set constraint with respect to latency requirements for these types of packets.

[0046] In another example, each of the at least one APs in the system for sorting products comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, associated with an individual controller of the plurality of controllers.

[0047] What may occur in the previous example is that the at least one AP only has one packet to be sent to an individual controller. However, since there may be one centralized packet queue for the AP, it may be that this packet is so far back in the queue that multiple send and receive periods, also known as time slices, must lapse before that particular packet can be sent.

[0048] In such cases the one specific controller may wait for a long time before the corresponding packet to be received and thus communication may not be optimized. Therefore, the inventors have found a beneficial example in which multiple queues are employed. In this way, the communication per AP may be optimized.

[0049] In yet another example, each of the at least one APs of the system for sorting products comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, associated with an individual controller of the plurality of controllers, and wherein each of the at least one APs comprises at least one additional packet queue for profile packets.

[0050] The inventors have found that with the previous example, certain packet types, such as profile packets, may clog the communication system. Namely, these types of messages may be information heavy and therefore take more time than other packets to be transmitted. Therefore, the inventors have experimented with a system wherein each controller has its own associated queue, but the information heavy packet are combined in a separate queue of which the send periods are well controlled by the system, such that these packets do not clog the system. According to another example of the disclosure, each of the at least one APs of the system for sorting products comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, wherein the packets sent during a send period are associated with priorities based on a corresponding type of packet, wherein said system is arranged to determine an order of sending said packets based on said priorities, such that each of the plurality of packet queues is associated with a priority corresponding to the type of packet.

[0051] Alternatively to the previous example, the inventors have found that it may be beneficial to implement multiple packet queues based on the information load or priority of the type of packet. Since multiple packet types have been defined, each having predetermined own standards and character sizes, a priority may be associated to each type of packet. In this way, high-priority and / or, for example smaller packets, may be transmitted faster and more frequently, whereas low-priority and / or, for example larger packets, may be sent at times the communication lines are less occupied, or at moments when there is a low risk of congestion or when there is a low risk to any collision.

[0052] In particular, this communication structure allows to prepare the position of the pusher body on the carrying body on its way to the beginning section (i.e. the part where products enter) of the, for example, conveyor belt.

[0053] Next, after receipt of the product, the sorting location can be communicated to the controller without severe timing constraints, such that the controller and pusher body are ready to push the product off at said sorting location. In addition to the above, the controller may await a go / no-go message from the at least one AP to actually sort the product at the sorting location.

[0054] In another example, packets in the at least one packet queue are reorganized after each combined send and receive period.

[0055] Rearranging or reorganizing the packets in the packet queue can be beneficial for instance in case the system gets notified that a certain sorting location has been clogged. Then, the system may prioritize within said packet queue that one particular packet may need to shift to the front to be transmitted as soon as possible because of i.e., the location of the carrying body along the conveyor belt. If the system would not be allowed to rearrange and reorganize the packets in the packet queue, these commands could remain stuck in the queue and cause problems in the system for sorting products in times where quick reaction is needed.

[0056] In yet another preferred example, the at least one AP of the system for sorting products is arranged to communicate with said plurality of controllers using a plurality of packet identifiers equal to the number of the plurality of controllers, wherein each of the plurality of packet identifiers is associated with an individual controller of the plurality of controllers.

[0057] In this preferred example when one AP is communicating with a plurality of controllers some type of structure needs to be introduced to differentiate, which packet is meant for which controller and vice-versa. Therefore, a packet identifier can be used, which is associated with an individual controller. When packets include this identifier it becomes clear for each controller whether the packet was meant for them and similarly the AP understands to which controller the just received packet belongs.

[0058] In a preferred example, the at least one AP of the system for sorting products comprises a plurality of APs arranged to communicate with said plurality of controllers.

[0059] A system for sorting products comprises a plurality of APs, which allows for packets and associated controllers to be distributed over multiple communication channels. In this way, the communication load can be reduced. It is noted that a balance may be struck. For each added AP, the communication load can be reduced by 1 / n, wherein n is the number of APs. However, with an increased number of APs, interference may increase which may result in an increased packet loss. Therefore, employing the same number of APs as controllers in the system may result in a non- optimally working system. Moreover, having more APs would also results in more complex communication to manage by the central manager and more compact physical integration of all the different APs into the system for sorting products.

[0060] According to an example of the disclosure, successive controllers along the direction of movement of the combinations of elongated carrying bodies and pusher bodies are arranged to communicate with different APs of the plurality of APs, such that a largest distance is generated between controllers that are arranged to communicate with the same AP of the plurality of APs, wherein the number of APs is smaller than the number of controllers. As mentioned above, having multiple APs can be beneficial to reduce the communication load. Another way to distribute the communication load, which is found by the inventors, is by spreading the transmission of packets it in time. The inventors have found that it may be beneficial to employ multiple APs communicating with a plurality of controllers while ensuring that the same APs is not communicating with successive controllers.

[0061] More particularly, the system is arranged in such a way that the greatest physical distance is achieved between controllers which communicate with the same AP, over the same communication line. This configuration is beneficial since the communication load is not equally spread over the length of the system. Namely, many information heavy packets may be sent at the beginning section of the system (where the products enter), because the controllers may need to be informed where and how to push the products off of the carrying body. Therefore, little to almost no communication may occur at the end of the system, as all products may already have been pushed off.

[0062] In yet another example the system comprises at least one leaky coax cable, and wherein said at least one AP is arranged to communicate with said plurality of controller through said at least one leaky coax cable.

[0063] The full assembly of all combinations of carrying bodies and pusher bodies comprised by the system might extend several hundreds of meters. In addition to that, the controllers associated with the carrying bodies and pusher bodies may be known to follow a certain path and may remain within a predefined space. Therefore, communicating through leaky coax cables allows the inventors to reach the far end of the system (in some cases with a repeater along the coaxial cable) without needing strong and expensive emitters. They basically confine the emission efforts to the region where the communication is expected to occur. Moreover, the use of leaky coax cables in the proximity of the controllers reduces the interference and offers a uniform signal coverage.

[0064] Another aspect that the disclosure pertains to is a method of operating a system for sorting products, wherein said method comprises the steps of: sending, by the AP, at least two packets to any of said plurality of controllers during said send period; receiving, by the AP, during said receive period, responds to said at least two packets sent during said send period to said at least two packets during said receive period.

[0065] In another example of a method, a duration of said receive period is fixed.

[0066] Lastly, as pertained in yet another example of a method of this disclosure, a duration of the receive period of the at least one AP is dynamic and lasts until all responses to the sent packets, in a corresponding send period directly preceding said receive period, are received or a maximum predetermined time has lapsed.

[0067] The last three examples of the disclosure may be beneficial since they employ the speak-when-spoken-to principle as disclosed earlier, wherein the AP has an executive role. Moreover, a non-traditional communication method is employed wherein more than one packets are transmitted before awaiting response. This way the AP can more effectively communicate with its submissive communicators and the communication load is reduced significantly. In the second example, having a fixed receive period allows the AP to listen at predetermined intervals and organizes the communication between the AP and its submissive communicators, such that communication moments are clear for both parties. As to the last example, a more beneficial use of the communication times would be to dynamically adjust the duration of the send and receive periods and await answers to all sent packets with having a time-out escape for i.e., lost packets. This way it is circumvented that both parties have silent moments in order to spread communication load timewise.

[0068] SHORT DESCRIPTION OF THE FIGURES

[0069] Fig 1A-D show different views of a system for sorting products

[0070] Fig 2 shows an illustration on a component level of the communication configuration for a system for sorting products

[0071] Fig 3A-B-C show different ways of communication between at least one Access Point and a plurality of controllers. DETAILED DESCRIPTION

[0072] For a proper understanding of the disclosure, in the detailed description below, corresponding elements or parts of the disclosure will be denoted with identical reference numerals as in the drawings.

[0073] Figures 1A - 1 D show a system 10 for sorting products.

[0074] The system 10 may comprise a number of combinations of an elongated carrying body 110 and a pusher body 120, which combinations are located one after another and are movable in a direction of movement following a path along which a number of sorting locations are provided.

[0075] The elongated carrying bodies extend parallel to each other and perpendicular to the direction of movement. The elongated carrying bodies are configured for carrying the products to be sorted 30, wherein the pusher body is arranged for pushing a product carried by the elongated carrying body off of the elongated carrying body towards any of the sorting locations 11.

[0076] A plurality of controllers 140 (fig. 2) are provided, which are arranged to move along a closed loop trajectory and may be arranged for controlling the sorting of the products.

[0077] For example, each controller 140 may be provided on at least one combination of the elongated carrying body and the pusher body, wherein each one of the plurality of controllers is arranged to control at least one of the displacing devices of at least the combination and / or neighboring combinations of the elongated carrying body and the pusher body.

[0078] The system may further comprise at least one stationary Access Point, AP, 200 arranged to send and receive packets to one or more of said plurality of controllers.

[0079] These packets may comprise commands for one or more of said plurality of controllers to control the sorting of the products. More specifically, these packets may comprise commands for one or more of the plurality of controllers to control at least one of the displacing devices.

[0080] The inventors have found that it may be beneficial when the plurality of controllers are each arranged to only send a packet to said AP triggered by receipt of a packet from said AP. This means that the controllers may only send when spoken to. In other words, a controller may only be allowed to send a packet when that specific controller is addressed, by the AP, during a previous sent period.

[0081] The AP may be arranged to send packets during a send period, and to receive packets during a receive period, wherein said send period and said receive period follow one another in time, wherein said AP is arranged to send at least two packets during said send period to any of said plurality of controllers, and is arranged to wait, during said receive period, for responses to said at least two packets sent during said send period, from said any of said plurality of controllers.

[0082] Referring to figures 1A-1 D, products 30 are placed on top of the elongated carrying bodies 110. A product may span one, or multiple, elongated carrying bodies. Figure 1A discloses products that are associated with five elongated carrying bodies. This may require five pusher bodies to push a received product off of the corresponding elongated carrying bodies.

[0083] The dimensions of the products 30 may thus be such that a product 30 may span multiple consecutively situated elongated carrying bodies 110. In those particular cases multiple pusher bodies 120, corresponding to the multiple elongated carrying bodies 110 onto which the product 30 is placed, are needed to push off the product 30 towards the sorting location 11.

[0084] The pusher bodies may be aligned with a product 30, once a product 30 has been received on top of the elongated carrying bodies 110. In an example, the product 30 may be rotated slightly by the corresponding pusher bodies such that the corresponding product 30 may be efficiently pushed off at a location direction 11 . This is shown in Figure 1A, wherein the product indicated with reference numeral 30 is “straightened” before it is actually pushed off of the corresponding elongated carrying bodies.

[0085] The displacing devices 130 are, for example, electronic motors, stepper motors, brushless motors, brushed motors, servomotors, etc. The displacing devices 130 may thus actuate the pusher bodies 120.

[0086] Each of the controllers is thus associated with one or more combinations of elongated carrying bodies and pusher bodies. Each controller is thus arranged to control the pusher bodies with which it is associated. A controller may receive information from the AP related to a received product 30 on its associated one or more combinations of elongated carrying bodies and pusher bodies. The information may comprise destination information, i.e. information with respect to the specific sorting location 11 at which the product should be pushed off. Further, the information may comprise details with respect to push profiles. A push profile comprises, for example, the acceleration over time that has to be followed by the corresponding pusher bodies for pushing the product 30 off of the corresponding elongated carrying bodies. Other types of push profiles may exist as well as a skilled person would readily understand.

[0087] The inventors have found that the communication between the at least one AP and the plurality of controllers may become a bottleneck, especially for large systems 10 having many combinations of elongated carrying bodies and pusher bodies.

[0088] The bottleneck may relate to the throughput as well as to the latency of packets being communicated from the at least one AP to the controller, or the other way around.

[0089] The present disclosure is thus aimed at an efficient communication topology between the at least one AP and the plurality of controllers.

[0090] One of the aspects of the present disclosure is that the controllers will only be allowed to send a packet once they are spoken to by the at least one AP. If a particular controller is not spoken to, i.e. addressed by the at least one AP, that particular controller is not allowed to send any packet.

[0091] The above means that the at least one AP is able to “control” the communication between the at least one AP and the controllers. The rate of congestion of the communication between the at least one AP and the controllers can be controlled by the at least one AP.

[0092] This entails that the at least one AP has more control over the latency and the throughput of the packets that are being communicated.

[0093] The above described precondition is required for enabling an efficient communication method as is explained now further below.

[0094] The actual communication between the at least one AP and the plurality of controllers is divided in time slices, i.e. in send periods and receive periods. The at least one AP is arranged, i.e. allowed, to send packets during a send period. The at least one AP is arranged, i.e. allowed, to receive packets during a receive period. For example, the at least one AP may decide to send five packets during a send period to five specific controllers. During the subsequent receive period, the at least one AP is arranged to "listen”, i.e. receive, five responses from those five specific controller that have been addressed.

[0095] This method is made possible by the precondition that the controllers are only allowed to send when spoken to. As this precondition will make sure that the controllers that have not been addressed by the at least one AP will not respond.

[0096] It is noted that the communication protocol that is used by the AP 200 and the plurality of controllers 140 may be understood to be any of the IEEE 802 communication standards, but more specifically could be any of the, Wireless LAN, Wi-Fi, Bluetooth, Zigbee, or UWB. Of importance is that packets of information can be send and received in short-range communication between the AP 200 and the plurality of controllers 140.

[0097] In Figure 1A-D, the at least one stationary AP 200 may be arranged to communicate with the moving controllers 140 through a leaky coax cable 20 positioned in between the conveyor system formed by the combinations of elongated carrying bodies 110 and pusher bodies 120. This is best shown in Figure 1 D. The leaky coax cables 20 are positioned between the top and bottom part of the system 1 , i.e. more specifically between carries 110. Each cable is connected to AP 200 at one end of the sorting assembly and then runs in a straight line to other end of the sorting assembly. In this way a controller 140 can communicate with the AP 200 through the same coax cable, independently of whether the controller 140 is in the top or the lower part of the sorting assembly.

[0098] To achieve that, the position of the cables must obey the limitations imposed by the technology that is used. These are that not continuous metal shielding should be present between the leaky coax cable 20 and the controllers 140 with their antennas 135 in the top and bottom half and that the distance between the leaky coax cable 20 and the controllers 140 may be in the range prescribed by the technology specifications. The distance should be not too close because one cable’s signal may overwhelm the others and not too far because then the signal to the controllers 140 will become too weak. The pushing body 120 may be controlled to move with differents speeds and accellerations while moving from one end of the carrying body 110. The value for speed and / or accelleration over time may be called a profile. Each controller may have a profile for each movement of the pushing body. These profiles may be generated by the central controler 210.

[0099] For generating the profiles, third-order position profiles may be derived with values for position, velocity, acceleration, and jerk. For each displacement seven phases can be identified:

[0100] 1. Acceleration build-up (to— >ti),

[0101] 2. Constant acceleration (ti— >t2),

[0102] 3. Acceleration ramp-down (t2^t3),

[0103] 4. Constant velocity (t3^t4),

[0104] 5. Deceleration build-up (t4— ts),

[0105] 6. Constant deceleration (ts— >te),

[0106] 7. Deceleration ramp-down (te— >t?).

[0107] The profiles can have maximum values for acceleration, deceleration, velocity, acceleration jerk and deceleration jerk.

[0108] The generated profile may need to be communicated to the controller 140, in order to know which position the pushing body 120 may follow over time.

[0109] A profile does not always exist of exactly one third-order profile. A pushing body can perform multiple separate movements while moving from one end of the carrying body to the other. Each movement may have a profile but are called “profile steps” when combined into a multiple step movement.

[0110] Transmitting the profile steps from the central controller 210 through the AP 200 to the controller 140 can be done in several ways. A straightforward way of communicating a profile step is sending all the values for time, position, speed, acceleration and jerk that define a third-order profile. The advantages of this way of working are that all relevant information is included in the message, that almost no calculations are needed in the controller 140 and that the resulting profile will be very accurate because there will be no calculation deviations. The disadvantage is the large size of the profile messages.

[0111] Another method is to only send the boundary values of each part of the profile, where the other values are calculated by the controller. Values needed in this option include maximum values for acceleration and deceleration jerk, acceleration, deceleration and speed. The values for the durations of the phases where acceleration is constant and the end values of the acceleration are also needed. This method has the advantage that still all relevant data is encoded, but the messages can be significantly shorter. The disadvantage is that some rounding of error may occur in the calculations in the controller 140.

[0112] A third method is to not send a message for the whole profile, so for a movement from one resting position to another, in one go, but to split the message for speed change sections. Data in the message will describe the required jerk, maximum acceleration, final acceleration, final velocity and delay. This has the advantage that the messages will be even shorter and that this message are better suitable for combined profiles where the pushing body 120 may not come to a full stop between parts of the profile.

[0113] In figure 2D a cross section of the sorter is shown. This shows the carriers 110 in the top part, the carriers 110 in the lower part and the pusher bodies 120, in the respective top and lower parts. The frame of the system is built from side frames 105 that carry runways for the wheels of the carriers, an outside cover and a bottom cover. These side frames are connected in regularly spaced locations by cross beams 106. These cross beams support the holders for the leaky coax cable 20.

[0114] The reliability of the wireless connection between the leaky coax cable and the controllers may be of importance for the correct functioning of the system. It may therefore be of importance to keep external disturbances to a minimum. This may be done by an embodiment of the side and bottom covers as metal plates, which are electrically connected to each other. Together with the metal in the carrier bodies, this may make the inside of the system resemble a Faraday’s cage. In that way, radio signals coming from outside have a smaller chance of disrupting the controls signals of the sorter. At the same time, this cage also prevents the wireless signals used in the system from propagating outside the system and possibly disturbing other processes near the system.

[0115] Figure 2D shows four coax cables 20, 21 even when only three may be needed for the operation of the sorter. The fourth cable 21 may be utilized for redundancy purposes. If for any reason communication over one of the coax cable 20 is interrupted, the network switch 220 may detect an absence of responses 300’ to any message 300.

[0116] The system may then detect which coax cable 20 is affected and switch the communication of that cable to the redundant fourth cable 21. The benefit of this redundancy is that the system can keep operating with all carriers, even when a communication channel fails. Repair can be undertaken when the sorting shift has ended and the disruption to the operation is minimal.

[0117] Additionally, the leaky coax cable 20 may be connected to one or more repeaters, or amplifiers, along the cable to strengthen the signal from the AP 200.

[0118] Repeaters may only be used when the length of the system 10 is longer than a simple application of a leaky coax cable allows. This maximum length is usually about 100 meters. When a repeater is needed, each coax cable 20 will be associated with its own repeater, which only repeats and strengthens the signal in that cable 20.

[0119] Whether these repeaters and how many are needed, depend on the length of the system 10 for sorting products

[0120] In the following figures the communication scheme will be elaborated, and different examples thereof are discussed. The general communication network is shown in Figure 2 and ways of communicating between the AP 200 and the controllers 140 are discussed in Figure 3A-B-C. In the present disclosure, three APs will be used as an example, but the expert in the field may understand that this is an arbitrary number and more or less APs could be used.

[0121] The system for sorting products 10 may comprise a central packet manager 210 arranged for construing packets comprising commands for one or more of the plurality of controllers 140. The commands may comprise instructions for the controller to control corresponding pusher bodies 120 based on the product to be sorted 30 and its sorting location, i.e. the location where the product 30 should be pushed off of the corresponding carrying body 110.

[0122] Any packet communicated between the central packet manager 210 and the at least one Access Point, AP, 200 may traverse a network switch 220. The network switch 220 is arranged to route such traffic.

[0123] The central packet manager 210 may, for example, may communicate with a detection system, which detection system is arranged to determine an orientation of a product 300 received on one or more carrying bodies. Further, the detection system may determine the corresponding sorting location 11 based on a barcode or another product identifier positioned on the product 30. This information can then be used by the system 10 to determine when the pusher bodies 110 should start pushing the product towards that sorting location 11.

[0124] In Figure 3A a traditional communication scheme between an AP 200 and a controller 140 is shown as an example. The AP 200 sends one packet 300 to a specific controller 140 and awaits response from said specific controller 140, before continuing communication.

[0125] The time required for a packet to be communication from the AP 200 to the controller 140, and vice versa, is indicated with the horizontal arrows.

[0126] As mentioned above, in prior art communication schemes the precondition that the controllers may only send when spoken to was not implemented. That means that the controllers may actively initiate a transmission without a “trigger” message received from the at least one AP. This may cause chaos and congestion in the communication medium between the at least one AP and the controllers.

[0127] The inventors have found that it may be beneficial to introduce such a precondition to better regulate, or control, the traffic of the packets between the at least one AP and the controllers.

[0128] On top of that, the communication scheme is improved, as is now elucidated in more detail with reference to figures 3B and 3C.

[0129] Both figures 3B and 3C illustrate so-called time slices. A time slice comprises a send period and a receive period. During a send period, the at least one AP is allowed to transmit packets to the controllers. During a receive period, the controllers are allowed to respond to packets received from the at least one AP.

[0130] In accordance with the present disclosure, the at least one AP may transmit at least two packets during one single send period. Figure 3B and figure 3C illustrate the situation wherein three packets are sent by the at least one AP during the send period. Packets sent and responses received are indicated with reference numerals 301 and 302.

[0131] The difference between figure 3B and 3C relates to the length of the time slice, for example the length of the receive period. This is explained as follows.

[0132] In figures 3B it is illustrated that the length of the time slices may be fixed, or predetermined. This means that both the send period as the receive period may be of fixed length. The advantage of this particular example is that it is not needed to wait indefinitely before a particular response is received. See for example the indication of the “Spillover”. Such a response would be received after the receive period has lapsed. The at least one AP may determine that responses that not have been received during the receive period are considered to be “timed out”. This may result in packets to be retransmitted but, on the other hand, save time as it is not needed to wait indefinitely on the receipt of such a response. This is a tradeoff.

[0133] The opposite scheme is shown in figure 3C, wherein the length of the time slices are variable. This may, especially, be the case for the receive period. The receive period may end once all responses have been received, as indicated in figure 3C. The advantage hereof is that there are no, or much less, timeouts.

[0134] The design and these wireless communication implementations for the system for sorting products 10, as described above, ensures effective communication between an at least one AP 200 and the plurality of controllers 140 through which variable controlling of push-offs of products 30 towards a plurality of sorting locations 11 can be achieved. Thereby existing problems of known systems for sorting products 10 with mechanical implementation through a wheel and guide track are mitigated and sorting times, speed can be improved, and costs can be reduced.

[0135] REFERENCE LIST

[0136] 10 system for sorting products

[0137] 11 sorting locations

[0138] 20 leaky coax cable 30 product

[0139] 110 elongated carrying body

[0140] 120 pusher body

[0141] 130 displacing device

[0142] 140 a plurality of controllers 200 at least one stationary Access Point, AP

[0143] 210 central packet manager

[0144] 220 network switch

Claims

CLAIMS1. System for sorting products comprising: a plurality of controllers arranged to move along a closed loop trajectory and arranged for controlling the sorting of the products, at least one stationary Access Point, AP, arranged to send and receive packets to one or more of said plurality of controllers, wherein said packets comprise commands for one or more of said plurality of controllers to control the sorting of the products; said plurality of controllers are each arranged to only send a packet to said AP triggered by receipt of a packet from said AP; said AP is arranged to send packets during a send period, and to receive packets during a receive period, wherein said send period and said receive period follow one another in time, wherein said AP is arranged to send at least two packets during said send period to any of said plurality of controllers, and is arranged to wait, during said receive period, for responses to said at least two packets sent during said send period, from said any of said plurality of controllers.

2. The system for sorting products according to claim 1 , wherein the system further comprises: a number of combinations of an elongated carrying body and a pusher body, which combinations are located one after another and are movable in a direction of movement following a path along which a number of sorting locations are provided, wherein the elongated carrying bodies extend parallel to each other and perpendicular to the direction of movement and wherein the elongated carrying bodies are configured for carrying the products to be sorted, wherein the pusher body is arranged for pushing a product carried by the elongated carrying body off of the elongated carrying body towards any of the sorting locations; wherein each combination is further provided with a displacing device for moving the pusher body in a sorting direction along the carrying body, the sorting direction extending substantially perpendicularly to the direction of movement, for pushing said product carried.

3. The system for sorting products according to any of the previous claims, wherein each controller is provided on at least one combination of the elongated carrying body and the pusher body, and wherein each one of the plurality of controllers is arranged to control at least one of the displacing devices of at least said combination and / or neighboring combinations of the elongated carrying body and the pusher body, and wherein the packets comprise commands for one or more of the plurality of controllers to control at least one of the displacing devices.

4. The system for sorting products according to any of the previous claims, wherein the system further comprises: a central manager arranged for construing said packets comprising said command for said one or more of said plurality of controllers based on sorting locations where products to be sorted should be pushed off of the carrying body.

5. The system for sorting products according to any of the previous claims, wherein a duration of the receive period is fixed.

6. The system for sorting products according to claim 5, wherein the duration of the receive period is predetermined based on the number of packets sent during said send period.

7. The system for sorting products according to any of the claims 1 - 4, wherein a duration of the receive period of the at least one AP is dynamic and lasts until all responses to the sent packets, sent in a corresponding send period directly preceding said receive period, are received or a maximum predetermined time has lapsed.

8. The system for sorting products according to any of the previous claims, wherein a type of packet to be sent by said at least one AP is any of:a pre-sorter packet for indicating a position, where a pusher body at a corresponding carrying body should move to before receiving a corresponding product to be sorted; a position packet for indicating a position .where a pusher body at a corresponding carrying body should move to after receiving a corresponding product to be sorted; a profile packet for indicating a push profile over time for pushing a particular product off of a corresponding carrying body, said push profile indicates how a particular product is to be pushed over time; a go / no-go packet for indicating whether or not to push a particular product off of a corresponding carrying body; a status packet for requesting a status of a controller of said plurality of controllers.

9. The system for sorting products according to any of the preceding claims, wherein each of the at least one APs comprises a single packet queue comprising the packets to be sent by said at least one AP to any of the controllers, wherein the single packet queue is based on an order in which the packets have entered the queue, such that a First In First Out, FIFO, order is maintained.

10. The system for sorting products according to any of the claims 1-8, wherein each of the at least one APs comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, associated with an individual controller of the plurality of controllers.

11. The system for sorting products according to claim 8, wherein each of the at least one APs comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, associated with an individual controller of the plurality of controllers, and wherein each of the at least one APs comprises at least one additional packet queue for profile packets.

12. The system for sorting products according to claim 8, wherein each of the at least one APs comprises a plurality of packet queues, wherein each of the plurality of packet queues comprises packets to be sent by said at least one AP to any of the controllers, wherein the packets sent during a send period are associated with priorities based on a corresponding type of packet, wherein an order of sending said packets is determined based on said priorities, such that each of the plurality of packet queues is associated with the priorities corresponding to the type of packet.

13. The system for sorting products according to any of the claim 9-12, wherein packets in the at least one packet queue are reorganized after each combined send and receive period.

14. The system according to any of the previous claims, wherein the at least one AP is arranged to communicate with said plurality of controllers using a plurality of packet identifiers equal to the number of the plurality of controllers, wherein each of the plurality of packet identifiers is associated with an individual controller of the plurality of controllers.

15. The system according to any of the previous claims, wherein successive controllers along the direction of movement of the combinations of elongated carrying bodies and pusher bodies are arranged to communicate with different APs of the plurality of APs, such that a largest distance is generated between controllers that are arranged to communicate with the same AP of the plurality of APs, wherein the number of APs is smaller than the number of controllers.

16. A method of operating a system for sorting products in accordance with any of the previous claims, wherein said method comprises the steps of: sending, by said AP, at least two packets to any of said plurality of controllers during said send period; receiving, by said AP, during said receive period, responds to said at least two packets sent during said send period to said at least two packets during said receive period.

17. A method in accordance with claim 17, wherein a duration of said receive period is fixed.

18. A method in accordance with claim 16, wherein a duration of the receive period of the at least one AP is dynamic and lasts until all responses to the sent packets, in a corresponding send period directly preceding said receive period, are received or a maximum predetermined time has lapsed.

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