System and method for synchronizing motion of multiple vehicles in an independent cart system

Abstract

Systems and methods are provided for synchronizing the motion of multiple vehicles in an independent cart system. Synchronizing multiple vehicles in an independent cart system to reduce spacing and increase throughput designates one of the movers as a leader and at least one additional mover as a follower to define a chain of vehicles. Motion commands for the chain are provided to the controller of the leader and the controller generates a motion trajectory. The controller communicates the motion trajectory to the controller of each of the follower movers. If a follower is unable to maintain the motion trajectory of the leader, the controller of the follower generates a message to the controller of the leader indicating that the motion trajectory needs to be modified. The controller of the leader modifies the motion trajectory and forwards the modified motion trajectory to the controller of each follower. If all movers are following the modified trajectory, the controller of the leader can return to the original motion trajectory.

Description

TECHNICAL FIELD

[0001] The subject matter disclosed herein relates to motion control for independent cart systems. More specifically, an improved system for controlling a plurality of vehicles configured to travel in concert along a track of an independent cart system, including bidirectional communication between controllers for each of the vehicles, where a follower vehicle updates a leader vehicle with the ability of the follower to execute a leader's motion trajectory. BACKGROUND

[0002] Motion control systems that utilize movers and linear drives can be used in a wide variety of processes (e.g., packaging, manufacturing, and processing) and can provide advantages over conventional conveyor systems, with enhanced flexibility, extremely high speed motion, and mechanical simplicity. The motion control system includes a set of independently controlled "movers," each of which is supported on a track to move along the track. The track is composed of a plurality of track segments, which in turn hold individually controllable electric coils. Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the movers to travel along the track.

[0003] Each of the movers can move and position independently along the track in response to the moving electromagnetic field generated by the coils. In a typical system, the track forms a closed path, and each mover repeatedly travels on the closed path. At certain locations along the track, other actuators can interact with each mover. For example, the mover can stop at a loading station where a first actuator places a product on the mover. The mover can then move along a processing segment of the track, where various other actuators can fill, process, position, or otherwise interact with the product on the mover. The mover can be programmed to stop at each of the various locations or to move past each of the other actuators at a controlled speed. After the various processes are performed, the mover can pass through or stop at an unloading station where the product is removed from the mover. The mover then completes a cycle along the closed path by returning to the loading station to receive another product unit.

[0004] In certain applications, it is desirable to cooperatively control the motion of multiple movers to form a "chain" of movers that sequentially travel along a track. Adjacent movers can be physically linked via coupling members or via a load that spans multiple movers. Alternatively, adjacent movers can be virtually linked by sharing a motion trajectory. When the movers are independently controlled, they are unaware of the motion trajectory of the adjacent mover that travels ahead. Each mover operates under the assumption that the mover immediately ahead can stop at its current position at any time, and therefore, the minimum spacing between movers needs to be a sufficient distance so that one mover can stop before reaching the current position of the mover immediately ahead. However, when the movers are cooperatively operated due to physical or virtual linking, it is possible to have adjacent movers travel closer together than they would otherwise be allowed to, because they follow a common motion trajectory.

[0005] Although two adjacent movers with nominally identical structures can receive the same motion trajectory command, in practice, the movers do not typically follow the same motion trajectory. For example, due to manufacturing tolerances or wear, each mover has some physical differences. Similarly, due to manufacturing tolerances or wear, the track has variations along its length. The strength of the electromagnetic field generated along the track can vary due to variations in the coils embedded in the track. Additionally, the performance of the mover varies on curved sections compared to straight sections due to the centrifugal forces experienced by the mover. The performance of the mover on curved sections is different than the performance of the mover on straight sections when the two movers transition from a straight section to a curved section or from a curved section to a straight section. Other variations in performance can occur due to damage to the mover or track section or due to debris present along the track. Due to any of these variations, two adjacent movers with nominally identical structures and receiving the same motion trajectory command will typically not follow the same motion trajectory as they travel along the track.

[0006] When the movers are cooperatively operated, the spacing is reduced to a great extent based on the assumption that they will follow the same motion trajectory. However, if one mover is unable to follow the motion trajectory, the reduced spacing increases the potential for collision between adjacent movers. Therefore, to reduce the potential for collision, the spacing between adjacent movers needs to have a minimum spacing of sufficient distance to account for variations between the movers and / or variations in the track to prevent collision.

[0007] Therefore, it is desirable to provide an improved system and method for synchronizing the cooperative motion of multiple vehicles to reduce the spacing between the vehicles and increase the throughput of an independent cart system. SUMMARY

[0008] According to one embodiment of the present application, a system for synchronizing motion of a plurality of movers in an independent cart system includes a first mover for leading a chain of movers, at least one additional mover following the first mover within the chain of movers, a first controller configured to control operation of the first mover, and at least one additional controller configured to control operation of the at least one additional mover. The first controller is configured to obtain a desired motion trajectory for the first mover and transmit the desired motion trajectory to the at least one additional controller. The at least one additional controller is configured to determine a desired dampening for the at least one additional mover and transmit the desired dampening to the first controller. The first controller is configured to modify the desired motion trajectory according to the desired dampening received from the at least one additional controller.

[0009] According to another embodiment of the present application, a method for synchronizing motion of a plurality of movers in an independent cart system obtains a desired motion trajectory for a first mover with a first controller and transmits the desired motion trajectory from the first controller to at least one additional controller. A desired dampening for the at least one additional mover is determined with the at least one additional controller. The dampening is transmitted from the at least one additional controller to the first controller and the desired motion trajectory is modified in the first controller according to the desired dampening.

[0010] These and other advantages and features of the application will become apparent to those skilled in the art from the detailed description and accompanying drawings. However, it is to be understood that no limitation of the scope of the application is intended by the details of the description or illustration. The summary of the application and the abstract are not intended to be limiting in any way. Various modifications and changes can be made therein and by those skilled in the art without departing from the true spirit and scope of the application, which is defined by the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] Various exemplary embodiments of the subject matter disclosed herein are shown in the drawings, which are appended hereto, and wherein the same reference numerals are used throughout the various figures and drawings to designate similar or equivalent parts, and wherein:

[0012] Figure 1 is a schematic diagram of an exemplary control system for a linear drive system according to one embodiment of the present application;

[0013] Figure 2 is a cross-sectional view of one embodiment of a mover and track segment included in a linear drive system taken along 2-2 of Figure 1

[0014] Figure 3 is a bottom plan view of an exemplary mover of Figure 2

[0015] Figure 4 is​​Figure 2 A partial side sectional view of the mover and track segment;

[0016] Figure 5 It is along Figure 1 A cross-sectional view of another embodiment of the linear drive system including the mover and track segment, taken from section 2-2;

[0017] Figure 6 yes Figure 5 A partial side sectional view of the mover and track segment;

[0018] Figure 7 yes Figure 2 A partial top sectional view of the mover and track segment;

[0019] Figure 8 yes Figure 1 A block diagram representation of one embodiment of an exemplary control system;

[0020] Figure 9 yes Figure 1 A block diagram representation of another embodiment of the exemplary control system;

[0021] Figure 10 It is a block diagram representation of an independent trolley system with a single track and multiple movers;

[0022] Figure 11 It is a block diagram representation of an independent trolley system with multiple tracks and multiple movers; and

[0023] Figure 12 This is a schematic diagram of an exemplary control system for a linear drive system according to another embodiment of the present invention.

[0024] In describing the various embodiments of the invention illustrated in the accompanying drawings, specific terminology will be used for clarity. However, the invention is not intended to be limited to the specific terminology chosen so far, and it should be understood that each specific term includes all technical equivalents that operate in a similar manner to achieve a similar purpose. For example, the terms "connected," "attached," or similar terms are frequently used. They are not limited to direct connections but include connections via other elements, wherein such connections are considered equivalent by those skilled in the art. Detailed Implementation

[0025] Various features and advantageous details of the subject matter disclosed herein will be more fully described with reference to the non-limiting embodiments described in detail below.

[0026] The subject matter disclosed herein describes an improved system and method for synchronizing the coordinated motion of a plurality of vehicles to reduce the spacing between the vehicles and increase the throughput in an independent cart system. One mover in the independent cart system is designated as a leader and at least one additional mover in the independent cart system is designated as a follower. The leader and one or more followers define a chain or train of vehicles configured to travel together along a track of the independent cart system. Motion commands for the chain of movers are provided to a controller of the leader. The controller generates a motion trajectory for the leader. The controller communicates the motion trajectory to a controller of each of the other movers in the chain. Depending on the current position along the track, the same controller can be responsible for controlling the leader and one or more followers. Alternatively, separate controllers can be responsible for controlling the leader and controlling one or more followers. The controller of each of the followers commands the mover to follow the motion trajectory of the leader and monitors the performance of the follower for which it is responsible. If the follower is unable to maintain the motion trajectory of the leader, the controller of the follower generates a message to the controller of the leader indicating that the motion trajectory needs to be modified so that the follower maintains the desired motion trajectory. The message also includes data quantifying the modification needed, such as the amount of positional error currently observed by the controller of the follower. The controller of the leader modifies the motion trajectory and forwards the modified motion trajectory to the controller of each of the followers. If the leader follows the modified motion trajectory and the one or more followers are able to maintain the modified motion trajectory, the controller of the leader can return to the original motion trajectory and forward the new trajectory to the controller of each of the followers. Thus, if a follower is temporarily unable to maintain the desired motion trajectory of the chain of movers, the controller of the leader can adjust the motion trajectory, allowing the follower to catch up and then return to the original motion trajectory.

[0027] First turning to Figures 1 to 4 An exemplary independent cart system 5 (or simply "system 5") for moving articles or products includes a track 10 made up of a plurality of segments 15. According to the illustrated system 5, two segments 15 are connected end-to-end to define the illustrated track configuration. The illustrated segments 15 are all straight segments of substantially the same length. It should be appreciated that track segments of various sizes, lengths, and shapes can be connected together to form the track 10 without departing from the scope of the present disclosure. The track segments 15 can be connected to form a generally closed loop that supports a set of movers 20 that are movable along the track 10. The track 10 is illustrated in a horizontal plane. For convenience, reference will be made herein to Figure 1The discussion herein is directed to the horizontal orientation of the track 10 shown. Terms such as upper, lower, inner and outer are used with respect to the track orientation shown. These terms are relative to the track shown and are not intended to be limiting. It should be understood that the track can be installed in different orientations, such as tilted or vertical, and that the track includes different shaped segments, including but not limited to straight segments, inwardly curved, outwardly curved, upwardly tilted, downwardly tilted and various combinations thereof. The width of the track 10 can be greater in the horizontal or vertical direction depending on the application requirements. The mover 20 will travel along the track and assume various orientations depending on the configuration of the track 10 and the relationships discussed herein can change accordingly.

[0028] According to the system 5 shown, each track segment 15 includes an upper portion 25 and a lower portion 30. The upper portion 25 is configured to carry the mover 20 and the lower portion 30 is configured to house control elements. As shown, the upper portion 25 includes a generally U-shaped channel 33 extending longitudinally along the upper portion 25 of each segment. The channel 33 includes a bottom surface 35 and a pair of sidewalls 40, with each sidewall 40 including a rail 45 extending along the upper edge of the sidewall 40. The bottom surface 35, sidewalls 40 and rails 45 extend longitudinally along the track segment 15 and define a guideway along which the mover 20 travels. According to one embodiment, the surfaces of the channel 33 (i.e., the bottom surface 35, sidewalls 40 and rails 45) are flat surfaces made of a low-friction material along which the mover 20 can slide. The contact surfaces of the mover 20 can also be flat and made of a low-friction material. It is contemplated that the surfaces can be, for example, nylon, Aluminum, stainless steel, etc. Optionally, the hardness of the surfaces on the track segment 15 is greater than the contact surfaces of the mover 20 such that the contact surfaces of the mover 20 wear out faster than the surfaces of the track segment 15. It is also contemplated that the contact surfaces of the mover 20 can be removably mounted to the housing of the mover 20 such that they can be replaced if they wear out beyond a predetermined amount. According to other embodiments, the mover 20 can include low-friction rollers to engage the surfaces of the track segment 15. Optionally, the surfaces of the channel 33 can include different cross-sectional shapes and the mover 20 includes complementary cross-sectional shapes. Various other combinations of shapes and structures of the track segment 15 and mover 20 can be used without departing from the scope of the present invention.

[0029] According to the illustrated system 5, each mover 20 is configured to slide along the channel 33 as it is propelled by the linear drive system. The mover 20 includes a body 55 configured to fit within the channel 33. The body 55 includes a lower surface 60 configured to engage the bottom surface 35 of the channel 33, and side surfaces 65 configured to engage the sidewalls 40 of the channel 33. The mover 20 also includes a shoulder 70 extending inwardly from each of the side surfaces 65. The width of the shoulder 70 is equal to or greater than the width of the rail 45 that projects into the channel 33. A neck of the mover then extends upwardly to a top surface 75 of the body 55. The neck extends the thickness of the rail 45 such that the top surface 75 of the body 55 is generally parallel to the upper surface of each rail 45. The mover 20 also includes a platform 80 secured to the top surface 75 of the body 55. According to the illustrated embodiment, the platform 80 is generally square, and the width of the platform 80 is greater than the width between the rails 45. The lower surface of the platform 80, the outer surface of the neck, and the upper surface of the shoulder 70 define a channel 85 in which the rail 45 runs. The channel 85 acts as a guide to direct the mover 20 along the rail. It is contemplated that various shaped platforms or attachments can be secured to the top surface 75 of the body 55. Furthermore, various work pieces, clamps, fixtures, or the like can be mounted on top of each platform 80 for engagement with a product to be carried along the rail by the mover 20. The platform 80 and any work pieces, clamps, fixtures, or other attachments present on the platform can at least partially define a load present on the mover 20.

[0030] The mover 20 is carried along the rail 10 by a linear drive system 90 Figure 2 ). The linear drive system is partially incorporated on each mover 20 and partially incorporated within each rail segment 15. Reference is also made to Figure 7 The drive coils 115 are positioned along the length of each rail segment, and one or more drive members 100 are mounted to each mover 20. It is contemplated that the drive members can be drive magnets 118, steel back iron and teeth, conductors, or any other suitable member that will interact with the electromagnetic field generated by the coils 115 to propel each mover 20 along the rail 10. For convenience, each drive member 100 is discussed herein as a drive magnet 118. Alternatively, it is contemplated that the drive members 100 can be mounted along the length of each rail segment, and one or more drive coils 115 can be mounted to each mover 20, with the associated controller that regulates the current in each drive coil also mounted to each mover.

[0031] Reference is also made to Figure 3A drive magnet 118 is arranged in a block on the lower surface of each mover. The drive magnet 118 includes a positive magnet segment 105 and a negative magnet segment 110, the positive magnet segment 105 having a north pole (N) facing outwards from the mover, and the negative magnet segment 110 having a south pole (S) facing outwards from the mover. According to the illustrated system 5, two positive magnet segments 105 are located outside the magnet group, and two negative magnet segments 110 are located between the two positive magnet segments 105. Optionally, the positive and negative motor segments can be arranged in an alternating configuration. In other configurations, a single negative magnet segment 110 can be located between the positive magnet segments 105. According to yet another embodiment, the drive magnet 118 can utilize a Halbach magnet array. The Halbach array inserts a magnet rotated 90 degrees, such that the north and south poles of the rotated magnet appear "east" or "west" relative to other magnets. The effect of rotation is to increase the magnetic field strength along one side of the magnet array (i.e., the side facing the drive coil) and decrease the magnetic field strength along the other side of the magnet array (i.e., the side away from the drive coil). Various other configurations of the drive magnet 118 may be used without departing from the scope of the invention.

[0032] The linear drive system 90 also includes a series of coils 115 spaced apart along the length of the track segment 15. See also... Figure 5 and Figure 7 The coil 115 can be positioned within the housing 50 for the track segment 15 and below the bottom surface 35 of the channel 33. The coil 115 is sequentially energized according to the configuration of the drive magnets 118 present on the movers 20. The sequential energization of the coil 115 generates a moving electromagnetic field that interacts with the magnetic field of the drive magnets 118 to propel each mover 20 along the track segment 15.

[0033] Each track segment 15 is equipped with a segment controller 120 to control the linear drive system and achieve the desired movement of each mover 20 along the track segment 15. Although in Figure 1 The block shown is outside track segment 15, but this arrangement is for illustrative purposes only, to show the interconnections between controllers. Figure 2As shown, it is contemplated that each segment controller 120 can be installed in the lower portion 30 of a track segment 15. Each segment controller 120 is in communication with a central controller 125, which in turn is in communication with an industrial controller 130. The industrial controller 130, for example, can be a programmable logic controller (PLC) configured to control elements of a production line disposed along the track 10. The production line can be configured to, for example, fill boxes, bottles, or other containers loaded onto or held by the movers 20 and label those boxes, bottles, or other containers as the movers 20 travel along the production line. In other implementations, robotic assembly stations can perform various assembly and / or machining tasks on workpieces carried by the movers 20. An exemplary industrial controller 130 includes a power supply 135 with a cable 140 connected to a utility power source, for example, a communication module 145 connected to the central controller 125 through a network medium 150, a processor module 155, an input module 160 that receives input signals 165 from sensors or other devices along the production line, and an output module 170 that transmits control signals 175 along the production line to controlled devices, actuators, etc. The processor module 155 can identify when a mover 20 is needed at a particular location and can monitor sensors, such as proximity sensors, position switches, etc., to verify that the mover 20 is at the desired location. The processor module 155 transmits the desired location of each mover 20 to the central controller 125, where the central controller 125 operates to generate commands for each segment controller 120.

[0034] Referring also to Figure 8The central controller 125 includes a processor 180 and a memory 185. It is contemplated that the processor 180 and the memory 185 can each be a single electronic device or formed of multiple devices. The processor 180 can be a microprocessor. Optionally, the processor 180 and / or the memory 185 can be integrated on a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The memory 185 can include volatile memory, non-volatile memory, or a combination thereof. An optional user interface 190 can be provided for an operator to configure the central controller 125 and load or configure desired motion trajectories for the movers 20 on the central controller 125. Optionally, the configuration can be performed via a remote device connected to the central controller 125 via a network and a communication interface 195. It is contemplated that the central controller 125 and the user interface 190 can be a single device, such as a laptop computer, notebook computer, tablet computer, or other mobile computing device. Optionally, the user interface 190 can include one or more separate devices for receiving information from and displaying information to a user, such as a keyboard, mouse, display, touch screen, interface port, removable storage media or media reader, etc. Optionally, the central controller 125 and the user interface can be an industrial computer mounted within a control cabinet and configured to withstand harsh operating environments. It is contemplated that other combinations of computing devices and peripherals as can be appreciated in the art can be utilized or incorporated into the central controller 125 and the user interface 190 without departing from the scope of the present invention.

[0035] In one aspect of the present invention, the central controller 125 can be configured to operate in a configuration referred to as "centralized control." The central controller 125 includes one or more programs stored in the memory 185 for execution by the processor 180. The central controller 125 receives the desired positions from the industrial controller 130 and determines one or more motion trajectories for each of the movers 20 to follow along the track 10. The programs executing on the processor 180 communicate with each of the segment controllers 120 on each track segment via the network medium 150. The central controller 125 can communicate the desired motion trajectories to each of the segment controllers 120.

[0036] In another aspect of the application, the central controller 125 can be configured to operate in a configuration referred to as "distributed control." The central controller 125 can be configured to communicate information from the industrial controller 130 that identifies one or more desired movers 20 to be positioned at or moved along the track segment 15, and each segment controller 120 can determine an appropriate trajectory of motion of the movers 20 present on the corresponding segment controller. It is contemplated that in distributed control a separate central controller 125 can not be needed, and instead the functionality performed by the central controller 125 for communication between the industrial controller 130 and each segment controller 120 can be incorporated into the industrial controller 130.

[0037] A position feedback system provides the segment controller 120 with position information for each mover 20 along the length of the track segment 15. According to Figure 2 and Figure 4 The system 5 shown in FIG. 1 1, the position feedback system includes one or more position magnets 205 mounted to the mover 20 and an array of sensors 210 spaced along the sidewall 40 of the track segment 15. The sensors 210 are positioned so that as the mover 20 passes each sensor 210, each of the position magnets 205 is in close proximity to the sensor. The sensors 210 are suitable magnetic field detectors, including, for example, Hall effect sensors, magnetic diodes, anisotropic magnetoresistive (AMR) devices, giant magnetoresistive (GMR) devices, tunneling magnetoresistive (TMR) devices, fluxgate sensors, or other microelectromechanical (MEMS) devices configured to generate an electrical signal corresponding to the presence of a magnetic field. The magnetic field sensors 210 output a feedback signal to the segment controller 120 for the corresponding track segment 15 on which the sensors 210 are mounted. The feedback signal can be an analog signal provided to a feedback circuit 215, which in turn provides a signal to a processor 220 corresponding to the magnets 205 passing the sensors 210.

[0038] According to Figure 5 and Figure 6 Another arrangement, shown in FIG. 12, the position feedback system utilizes the drive magnets 1 18 as position magnets. Position sensors 210 are positioned along the track segment 15 at locations suitable to detect the magnetic field generated by the drive magnets 1 18. According to the embodiment shown, the position sensors 210 are located below the coils 1 15. Alternatively, the position sensors 210 can be interspersed in the coils 1 15, and for example, located in the center of the coils or between adjacent coils. According to yet another embodiment, the position sensors 210 can be positioned within the upper portion 25 of the track segment 15 and proximate to the bottom surface 35 of the channel 33 to align with the drive magnets 1 18 as each mover 20 travels along the track segment 15.

[0039] Referring again toFigure 8 The segment controller 120 also includes a communication interface 225 that receives communications from the central controller 125 and / or from neighboring segment controllers 120. The communication interface 225 extracts data from message packets on the industrial network and passes the data to a processor 230 running in the segment controller 120. The processor can be a microprocessor. Alternatively, the processor 230 and / or memory 235 within the segment controller 120 can be integrated on a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). It is contemplated that the processor 230 and memory 235 can each be a single electronic device or formed of multiple devices. The memory 235 can include volatile memory, non-volatile memory, or a combination thereof. The segment controller 120 receives a motion trajectory or desired motion of the mover 20 and controls the mover 20 along the track segment 15 controlled by the segment controller 120 with motion commands.

[0040] Each segment controller 120 generates switching signals to generate a desired current and / or voltage at each coil 115 in the track segment 15 to achieve the desired motion of the mover 20. The switching signals 240 control the operation of switching devices 245 for the segment controller 120. According to the illustrated system 5, the segment controller 120 includes a dedicated gate driver module 250 that receives command signals from the processor 220, such as the desired voltage and / or current to be generated in each coil 115, and generates the switching signals 240. Alternatively, the processor 220 can incorporate the functionality of the gate driver module 250 and directly generate the switching signals 240. The switching devices 245 can be solid state devices activated by the switching signals, including but not limited to transistors, thyristors, or silicon controlled rectifiers.

[0041] According to the illustrated system 5, the track 10 receives power from a distributed DC voltage. A DC bus 255 receives a DC voltage VDC from a DC power source and conducts the DC voltage to each track segment 15. The illustrated DC bus 255 includes two voltage rails 260, 265 between which the DC voltage exists. The DC power source can include, for example, a rectifier front end configured to receive a single or multi-phase AC voltage at an input and convert the AC voltage to a DC voltage. It is contemplated that the rectifier portion can be passive, including a diode bridge, or active, including, for example, transistors, thyristors, silicon controlled rectifiers, or other controllable solid state devices. Although illustrated as being external to the track segments 15, it is contemplated that the DC bus 255 will extend within the lower portion 30 of the track segments. Each track segment 15 includes a connector to which a DC power source or another track segment can be connected so that the DC bus 255 can extend the length of the track 10. Alternatively, each track segment 15 can be configured to include a rectifier portion (not shown) and receive an AC voltage input. The rectifier portion in each track segment 15 can convert the AC voltage to a DC voltage utilized by the corresponding track segment.

[0042] The DC voltage from the DC bus 255 is provided to the power portion of the segment controller at input terminals 270, 275. A first voltage potential exists at the first input terminal 270 and a second voltage potential exists at the second input terminal 275. The DC bus 255 extends into the power portion of the segment controller 120 defining the positive rail 260 and the negative rail 265. The terms "positive" and "negative" are used herein for reference and are not meant to be limiting. It is contemplated that the polarity of the DC voltage existing between the input terminals 270, 275 can be negative such that the potential on the negative rail 265 is greater than the potential on the positive rail 260. Each of the voltage rails 260, 265 is configured to conduct a DC voltage having a desired potential according to the application requirements. According to one arrangement, the positive rail 260 can have a DC voltage at a positive potential and the negative rail 265 can have a DC voltage at a ground potential. Alternatively, the positive rail 260 can have a DC voltage at a ground potential and the negative rail 265 can have a DC voltage at a negative potential. According to yet another arrangement, the positive rail 260 can have a first DC voltage at a positive potential relative to a ground potential and the negative rail 265 can have a second DC voltage at a negative potential relative to the ground potential. The DC voltage potential created between the two rails 260, 265 is the difference between the potential existing on the positive rail 260 and the negative rail 265.

[0043] It is also contemplated that the DC power supply can include a third voltage rail having a third voltage potential. According to one implementation, the positive rail 260 has a positive voltage potential with respect to ground, the negative rail 265 has a negative voltage potential with respect to ground, and the third voltage rail is held at ground potential. Alternatively, the negative voltage rail 265 can be at ground potential, the positive voltage rail 260 can be at a first positive voltage potential with respect to ground, and the third voltage rail can be at a second positive voltage potential with respect to ground, where the second positive voltage potential is approximately half the magnitude of the first positive voltage potential. Using such a split DC bus, two of the switching devices 245 can be used in pairs to control the operation of one coil 115 by alternately providing positive or negative voltage to the one coil 115.

[0044] The power portion in each segment controller 120 can include a plurality of branches, where each branch is connected in parallel between the positive rail 260 and the negative rail 265. According to one implementation, the power portion includes three branches, each of which is connected in parallel between the positive rail 260 and the negative rail 265. Figure 8 The illustrated system shows three branches arranged in a half-bridge configuration. However, the number of branches can vary and will correspond to the number of coils 115 extending along the track segment 15. Each branch includes a first switching device 245a and a second switching device 245b connected in series between the positive rail 260 and the negative rail 265, with a common connection 243 between the first switching device 245a and the second switching device 245b. The first switching device 245a in each branch 221 can also be referred to herein as an upper switch, and the second switching device 245b in each branch 221 can also be referred to herein as a lower switch. The terms “upper” and “lower” are related only to the schematic representation and are not intended to indicate any particular physical relationship between the first switching device 245a and the second switching device 245b. The switching devices 245 include, for example, power semiconductor devices such as transistors, thyristors, and silicon controlled rectifiers, which receive a switching signal 240 to turn on and / or off. Each of the switching devices can also include a diode connected in anti-parallel between the common connection 243 and either the positive rail 260 or the negative rail 265.

[0045] According to one implementation, the switching signal 240 is a pulse width modulated signal having a first state and a second state. The first state of the switching signal 240 is a high state, and the second state of the switching signal 240 is a low state. The first state of the switching signal 240 is associated with the first switching device 245a being on and the second switching device 245b being off, and the second state of the switching signal 240 is associated with the first switching device 245a being off and the second switching device 245b being on. Figure 9The illustrated embodiment shows three branches arranged in a full-bridge configuration. Again, the number of branches can vary and will correspond to the number of coils 115 extending along the track segment 15. Each branch includes a first switching device 245a and a second switching device 245b connected in series on one side of the coil 115. The first and second switching devices 245a, 245b are connected between the positive rail 260 and the negative rail 265 with a first common connection between the first and second switching devices 245a, 245b. The first common connection is connected to the first side of the coil 115. Each branch also includes a third switching device 246a and a fourth switching device 246b connected in series on the other side of the coil 115. The third and fourth switching devices 246a, 246b are connected between the positive rail 260 and the negative rail 265 with a second common connection between the third and fourth switching devices 246a, 246b. The second common connection is connected to the second side of the coil 115. The first and third switching devices 245a, 246a in each branch can also be referred to herein as upper switches, and the second and fourth switching devices 245b, 246b in each branch can also be referred to herein as lower switches. The terms "upper" and "lower" are related only to the schematic representation and are not intended to indicate any particular physical relationship between the switching devices. The switching devices 245, 246 include, for example, power semiconductor devices such as transistors, thyristors, and silicon controlled rectifiers, which receive a switching signal 240 to turn on and / or off. Each of the switching devices 245, 246 can also include a diode connected in anti-parallel between the first or second common connection and the positive or negative rail 260, 265.

[0046] Referring again to Figure 8The processor 220 also receives feedback signals from sensors that provide an indication of operating conditions within the power segment or operating conditions of the coils 115 connected to the power segment. According to the illustrated system 5, the power segment includes a voltage sensor 285 and a current sensor 290 at the input of the power segment. The voltage sensor 285 generates a voltage feedback signal and the current sensor 290 generates a current feedback signal, each of which corresponds to operating conditions on the positive rail 260. The segment controller 120 also receives feedback signals corresponding to the operation of the coils 115 connected to the power segment. Voltage sensors 300 and current sensors 305 are connected in series with the coils 115 at each output of the power segment. The voltage sensors 300 generate voltage feedback signals and the current sensors 305 generate current feedback signals, each of which corresponds to operating conditions of the corresponding coil 115. The processor 230 executes programs stored on the memory device 235 to regulate the current and / or voltage supplied to each coil and the processor 230 and / or gate driver module 250 generate switching signals 240 that selectively enable / disable each of the switching devices 245 to achieve the desired current and / or voltage in each coil 115. Reference is also made to Figure 9 It is contemplated that the feedback signals from the current sensors 305 and / or voltage sensors 300 corresponding to the operation of the coils 115 can be provided to a dedicated current regulator device. As Figure 9 illustrated, the feedback signals are provided directly to the gate driver 250, which in turn regulates the current output to each coil and generates the switching signals 240 accordingly. The energized coils 115 generate electromagnetic fields that interact with the drive magnets 118 on each mover 20 to control the motion of the mover 20 along the rail segment 15.

[0047] As Figure 8 and Figure 9Further shown, the control system can also include a synchronization controller 350. The synchronization controller 350 includes a processor 352 in communication with a memory device 354. The memory device 354 is configured to store instructions for execution by the processor. It is contemplated that the processor 352 and memory 354 can each be a single electronic device or formed of multiple devices. The processor 352 can be a microprocessor. Optionally, the processor 352 and / or memory 354 can be integrated on a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The processor 352 can include a single core or multiple cores. The memory 354 can include volatile memory, non-volatile memory, or a combination thereof. An optional user interface 358 can be provided for an operator to configure the synchronization controller 350 and load or configure desired motion trajectories for movers 20 operating in coordination as a queue or chain of movers. Alternatively, the configuration can be performed via a remote device connected via a network and a communication interface 356 on the synchronization controller 350. The communication interface 356 is also configured to connect with the network medium 150 for communication with the central controller 125, industrial controller 130, and / or segment controller 120. In certain applications, it is contemplated that the functionality of the synchronization controller 350 can be performed in whole or in part in the central controller 125, industrial controller 130, segment controller 120, or a combination thereof.

[0048] In operation, it is contemplated that the independent cart system 5 operates under distributed control, and each segment controller 120 is responsible for controlling the operation of movers 20 present on the corresponding track segment 15. Referring next to Figure 10 each mover 20 is configured to operate independently of other movers 20 or in a chain 380 of movers. According to the illustrated embodiment, each mover 20 configured to operate independently of other movers 20 is labeled “S”. Each mover 20 configured to operate in a chain 380 of movers is labeled “L” or “F”, where a mover 20 labeled “L” is a leader in the chain 380 and a mover 20 labeled “F” is a follower in the chain. The chain 380 of movers includes a single leader L and one or more followers F. As Figure 10 shown, the first chain 380A of movers includes seventeen (17) followers and the second chain 380B of movers includes seven (7) followers.

[0049] According to one embodiment of the application, a chain 380 is defined by the synchronization controller 350. It is contemplated that the chain can be defined statically or dynamically during operation of the independent cart system. A statically defined chain 380 includes one leader L and a defined number of followers F. The number of followers remains constant and the chain remains the same length as it travels along the track. A statically defined chain can be used, for example, to pair two or three movers 20 together to transport a single object along the length of the track 10. The chain 380 can pass through a loading area and an unloading area of multiple instances of objects being loaded and unloaded, but the chain 380 remains constant as it returns from the unloading area to the loading area to receive a new object. Alternatively, the chain 380 can be dynamically defined. It is contemplated that, for example, the loading area can receive objects of different sizes. A different number of movers 20 can be required to transport each object. The synchronization controller 350 receives an identifier of the next object in the defined queue and defines a chain 380 of movers having a length sufficient to transport the object. Multiple movers 20 can be waiting in a queue area and the synchronization controller 350 defines the next mover 20 available in the queue as the leader L and defines an appropriate number of movers 20 as followers F so that the chain 380 can transport the object. The chain 380 travels from the queue to the loading station to receive the object. Between the loading area and the unloading area, the movers 20 travel in the chain 380. Once the object is unloaded, the synchronization controller 350 defines each mover 20 as an independent mover and the movers 20 return to the queue as individual movers for subsequent assignment. According to another application, it is contemplated that the movers 20 can travel in a chain along a certain segment of the track and as independent movers 20 along the remainder of the track. For example, when an external actuator interacts with the mover 20 or a load on the mover 20, it is desirable for the mover 20 to travel in the chain 380. Throughout the work area, the movers 20 travel in the chain 380. Outside the work area, the movers 20 travel independently from the end of the work area back to the beginning of the work area. As each mover 20 exits the work area, the synchronization controller 350 continually redefines the chain 380 with a new leader and also adds additional movers 20 to the end of the chain as followers as each mover 20 enters the work area.

[0050] Reference is also made to Figure 11It is contemplated that the chain 380 can include followers configured in a form other than sequential. According to the illustrated embodiment, the application includes two tracks. A portion of the first track 10A and a portion of the second track 10B are shown. The first chain 380A is shown with a leader L assigned to the first track 10A. The first chain 380A includes two followers F on the first track 10A and three followers on the second track 10B. The second chain 380B is shown with a leader L assigned to the second track 10B and a single follower F present on the first track 10A. For each chain, the movers 20 on each track 10A, 10B operate in coordination with the controller of the leader L that receives the desired motion trajectory. The controller of the leader transmits the motion trajectory to the controller of each follower, and the movers 20 operate in coordination to follow the desired motion trajectory.

[0051] Motion commands are generated for each mover 20 in the system 5 to define the desired operation of the mover. According to one aspect of the application, the industrial controller 130 is configured to execute a control program to achieve the desired operation of the system. The control program receives input signals 165 corresponding to the current state of the devices in the system and generates output signals 175 in accordance with the current state of the devices in the system to control actuators or other devices in the system. The control program can include motion commands for one or more movers 20, where the motion commands can be, for example, commands to move to a desired position along a track with track coordinates, or to move to a desired position with a station number or other such identifier that defines a position along a track.

[0052] The motion commands are converted from desired positions or locations along the track to desired motion trajectories for the movers 20. The desired motion trajectories can include a series of positions that the mover 20 is to be located at, and also include, for example, acceleration or deceleration rates and velocities of the mover at each position. Alternatively, the motion trajectories can be a series of positions in time generated according to desired acceleration or deceleration rates and velocities that the mover is to travel. The acceleration or deceleration rates and velocities can be configured for each mover 20 and can vary according to the load present on the mover 20, the position of the mover as it interacts with actuators located outside of the mover, and the like. The motion commands can be generated by the processor module 155 or by a dedicated motion control module located in the industrial controller 130. Alternatively, the industrial controller 130 can deliver the motion commands to the central controller 125 or to the segment controllers 120 on which the movers 20 are located, and the central controller 125 or the corresponding segment controllers 120 can be configured to generate the desired motion trajectories for each mover. Each segment controller 120 uses the motion trajectories of the movers 20 located on the corresponding track segment 15 to regulate the current to the coils 115 and obtain the desired motion of the movers 20 in response to the motion trajectories.

[0053] When multiple movers 20 are grouped together to travel in a chain 380, a single motion trajectory is generated for the chain. The motion trajectory is provided to the segment controller 120 on which the mover 20 that will be the leader L of the chain is located. As previously described, the chain 380 can be static or dynamic in the number of movers 20 and can have leaders L that are dynamically assigned as the chain 380 moves along the track. In some applications, it is advantageous to use a synchronization controller 350 to maintain the organization of the chain 380. The synchronization controller 350 can identify each mover 20 to be included in a static chain 380. Similarly, the synchronization controller 350 can maintain a record of the movers 20 in a dynamic chain and coordinate the dynamic assignment of movers 20 in a dynamic chain.

[0054] In addition to maintaining a record of which movers 20 are included in each chain 380, the synchronization controller 350 can also manage the generation and / or transmission of motion trajectories to the segment controllers 120. The synchronization controller 350 receives motion commands from the industrial controller 130 and generates a motion trajectory for the chain 380. The synchronization controller transmits the motion trajectory to the segment controllers 120 of the movers 20 that are identified as leaders. This motion trajectory of the movers 20 identified as leaders of the chain is the reference trajectory for the chain. The synchronization controller 350 can also be configured to transmit the reference trajectory to each segment controller 120 that controls one of the movers 20 in the chain 380. Optionally, the synchronization controller 350 transmits the reference trajectory only to the segment controllers 120 corresponding to the leaders and also transmits the length of the chain or the number of followers F to be included in the chain 380. The synchronization controller 350 can be configured to receive feedback from the segment controllers 120 corresponding to the position of the leader. As the leader L travels along the track, the synchronization controller 350 can transmit the motion trajectory to successive segment controllers 120. Alternatively, and in a fully distributed system, the synchronization controller 350 transmits the motion commands, desired positions, or motion trajectories to the segment controller 120 on which the leader L at the beginning of the commanded mover is located and the segment controllers 120 communicate with adjacent segment controllers as the mover 20 transitions between track segments 15 in order to transmit the motion commands, desired positions, or motion trajectories to the adjacent segment controllers.

[0055] It is contemplated that the chain 380 of movers can be configured to follow the reference motion trajectory according to two different options. In a first aspect of the invention, the segment controller 120 on which the leader L is located obtains the motion trajectory of the chain 380. The chain 380 is configured to operate as a single group of movers 20, and the segment controller 120 transmits the motion trajectory to each additional segment controller 120 on which a mover 20 in the chain 380 is located. The additional segment controllers determine the motion trajectory of the movers 20 in the chain 380 that exist on the corresponding track segment 15. Each mover 20 has a desired following distance L from the leader, and the new motion trajectory corresponds to the reference trajectory minus the following distance. For example, if each mover 20 in the chain is spaced 10 millimeters apart, the following distance for the first follower is 10 millimeters, the following distance for the second follower is 20 millimeters plus the width of the first follower, and so on. Each segment controller then generates switching signals 240 according to its respective motion trajectory to adjust the current through the coils 115 on the corresponding track segment 15 to achieve the desired operation of the movers 20 in the chain.

[0056] In a second aspect of the invention, the segment controller 120 on which the leader L is located obtains the motion trajectory of the chain 380. The chain 380 is configured to operate as a series of linked movers 20, and the segment controller 120 transmits the motion trajectory one hop to the adjacent segment controller 120 on which the next mover 20 in the chain 380 is located. The adjacent segment controller determines the motion trajectory of the movers 20 in the chain 380 that exist on the corresponding track segment 15. Each mover 20 has a desired following distance in the chain 380 to the mover one hop in front of it. The new motion trajectory corresponds to the motion trajectory received from the adjacent segment controller 120 minus the following distance. After determining the new motion trajectory of the mover 20 on the second track segment, the segment controller 120 of the second track segment passes the new motion trajectory one hop to the next adjacent segment controller 120. The next adjacent segment controller determines another new motion trajectory for the next mover 20 in the chain. This process is repeated until all of the movers 20 in the chain 380 have a motion trajectory determined according to the original reference motion trajectory of the chain. Each segment controller then generates switching signals 240 according to its respective motion trajectory to adjust the current through the coils 115 on the corresponding track segment 15 to achieve the desired operation of the movers 20 in the chain.

[0057] It is also contemplated that each segment controller 120 maintains a motion profile for each mover present on the segment controller. For example, if a segment controller 120 has two movers 20 present on the track segment 15 operated by the segment controller 120, the segment controller 120 will maintain two separate motion profiles. Similarly, if a segment controller 120 has three movers 20 present on the track segment 15 operated by the segment controller 120, the segment controller 120 will maintain three separate motion profiles, and so on for any number of movers present on a track segment. For ease of description, the operation of the chain 380 will be discussed assuming one mover 20 is present on each track segment 15 and each mover 20 is controlled by a separate segment controller 120. However, similar operations will occur when the chain 380 includes multiple followers F on a single track segment 15. The segment controller 120 maintains a separate motion profile for each mover 20, and rather than transmitting data between adjacent segment controllers 120, the segment controllers pass information between the motion profiles of each mover on the segment internally at the segment controller.

[0058] After the motion profile for each mover 20 in the chain 380 has been determined, each segment controller 120 attempts to maintain the desired profile for each mover present on the corresponding track segment 15. As previously discussed, many factors affect the ability of a mover 20 to maintain a desired motion profile. Variations in manufacturing, whether on a straight track segment or a curved track segment, and wear on the mover or track segment affect performance. One segment controller 120 for a follower F mover can not be able to maintain the desired motion profile of a leader L within the chain 380. Each segment controller 120 monitors the performance of each mover 20 it controls to determine whether the mover 20 is able to follow the desired motion profile.

[0059] When the mover 20 begins to deviate from the desired trajectory of motion, the segment controller 120 controlling the mover 20 determines a dampening of the corresponding mover. The dampening is some value that can be used to make the desired trajectory of motion less aggressive and thus make the mover 20 easier to follow. For example, the dampening can be a desired reduction in velocity, acceleration rate, or position value. The dampening can be determined according to the trajectory of motion and the application requirements. According to one aspect of the present application, the dampening can be a position value corresponding to the amount of tracking error observed by the segment controller 120. The tracking error is the difference between the desired position of the mover 20, which is defined in the trajectory of motion of the mover, and the actual position of the mover, which is observed via the position sensors 210 spaced along each track segment 15. If the segment controller 120 is unable to maintain the desired trajectory of motion, the tracking error will increase. Although a small amount of tracking error is acceptable, if the tracking error value exceeds a predetermined amount, the segment controller 120 will set the dampening value equal to the tracking error. In other applications, the segment controller 120 can predictively determine the dampening value. The segment controller 120 can maintain a record of past performance of the mover 20 and limit the performance of the commanded trajectory of motion based on the past performance. According to other options, the segment controller 120 can compare the trajectory of motion to limits established for operating zones along the track. A first portion of the chain 380 can exist in one operating zone and a second portion of the chain 380 can exist in a second operating zone. The trajectory of motion of the guide L can be set according to the first zone, but the mover 20 within the second operating zone can have limits imposed according to being located within the second zone. The segment controller 120 can determine an appropriate dampening value based on the past performance or position of the mover 20 prior to controlling the mover 20 to minimize the tracking error that occurs.

[0060] After the suppression value is determined, the segment controller 120 transmits the suppression value to the segment controller 120 responsible for controlling the leader L. When the chain 380 is configured to operate as a single group of movers 20, and the segment controller 120 transmits the motion trajectory to each additional segment controller 120 on which a mover 20 in the chain 380 is located, each additional segment controller is configured to transmit the suppression value to the segment controller 120 responsible for controlling the leader L. The segment controller 120 responsible for controlling the leader L then knows any performance limitations experienced by each mover 20 in the chain 380. The segment controller of the leader modifies the motion trajectory according to the suppression value of the maximum suppression as needed so that each mover 20 in the chain 380 will be able to follow the motion trajectory. The segment controller 120 of the leader then transmits the modified motion trajectory to each additional segment controller 120. The additional segment controllers 120 again determine the motion trajectory of the mover located on the corresponding track segment by subtracting the desired following distance from the modified motion trajectory of the leader as previously discussed. The segment controllers 120 of the leader and each follower now follow the modified motion trajectory that each mover 20 in the chain 380 should be able to track.

[0061] When the chain 380 is configured to operate as a series of linked movers 20 and the segment controller 120 transmits the motion trajectory to the adjacent segment controller 120 on which the next mover 20 in the chain 380 is located, each additional segment controller 120 transmits the suppression value to the adjacent segment controller from which it originally received the motion trajectory. As the suppression values are transmitted along the series of linked controllers, the controllers can be configured to compare their determined suppression value, if any, with the suppression value, if any, received from the adjacent segment controller. The segment controller 120 can then transmit the greater of the two suppression values to the next adjacent controller. Alternatively, each segment controller can create a data packet containing the suppression value determined for the mover corresponding to the controller as well as any suppression values received from adjacent controllers. As the suppression values are transmitted to adjacent controllers, each segment controller with a suppression value can add its own suppression value to the data packet. The segment controller 120 of the lead then receives all of the suppression values and knows any performance limitations experienced by each mover 20 in the chain 380. According to either option, the segment controller of the lead modifies the motion trajectory as necessary with the greatest suppression suppression value so that each mover 20 in the chain 380 will be able to follow the motion trajectory. The modified motion trajectory is transmitted back along the linked segment controllers in the manner discussed previously, and each additional segment controller 120 again determines the motion trajectory for the mover located on the corresponding track segment by subtracting the desired follow distance from the motion trajectory received from the adjacent segment controller. The segment controller 120 of the lead and each follower now follow the modified motion trajectory that each mover 20 in the chain 380 should be able to track. As the chain 380 travels along the track, the process of determining the suppression values and modifying the motion trajectory is repeated so that any mover 20 that is unable to maintain the desired motion trajectory at any point during movement causes the corresponding segment controller 120 responsible for controlling the operation of that mover to modify the motion trajectory to enable the mover 20 to follow the motion trajectory.

[0062] In addition to reducing the aggressiveness of the motion trajectory, it is contemplated that communication between the segment controllers 120 can be used to restore the motion trajectory to follow the original command. After a segment controller 120 determines a suppression value and transmits that suppression value to the lead controller L in the chain 380, each segment controller 120 continues to monitor the performance of the movers 20 for which it is responsible. If the mover 20 has previously experienced tracking errors, but is now following the modified motion trajectory, no suppression value is transmitted to the segment controller 120 responsible for controlling the lead in the chain 380. The segment controller 120 responsible for controlling the lead can restore following the original motion trajectory if it no longer receives a suppression value. According to one aspect of the present application, the segment controller 120 can immediately restore the original motion trajectory. If any of the movers 20 in the chain 380 are still unable to follow the original motion trajectory, a new suppression value will be determined and transmitted back to the segment controller of the lead. According to another aspect of the present application, the segment controller 120 of the lead L can be configured to incrementally return to the original motion trajectory. At each increment, the segment controller 120 of the lead L can allow the chain 380 to travel for a short duration with an incrementally more aggressive motion trajectory, and monitor the suppression values from each of the additional segment controllers 120. If each mover 20 is able to follow the incrementally more aggressive motion trajectory, the segment controller 120 of the lead L continues to incrementally return to the original motion trajectory until the original motion trajectory is achieved, or one of the additional segment controllers indicates that the mover 20 for which it is responsible is no longer able to track the motion trajectory, and a new suppression value is transmitted to the segment controller 120 of the lead L. In this manner, if a mover 20 is unable to follow the motion trajectory at a particular location, the segment controller 120 can temporarily modify the motion trajectory, and then return to the original motion trajectory when each mover 20 is again able to follow the original motion trajectory.

[0063] It is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the above description. The application is capable of other embodiments and of being practiced or being carried out in various ways. Variations and modifications of the foregoing are within the scope of the present application. Also, it is to be understood that the application

[0064] In the foregoing specification, various implementations have been described with reference to the accompanying drawings. However, it will be apparent that various modifications and changes can be made thereto without departing from the broader scope of the application as set forth in the attached claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. A system for synchronizing motion of a plurality of movers in an independent cart system, the independent cart system comprising a track and the plurality of movers configured to travel along the track, wherein, The track comprises a plurality of track segments, the system comprises: a first mover for guiding a chain of movers, wherein the first mover is selected from the plurality of movers in the independent cart system; at least one additional mover, wherein the at least one additional mover is selected from the plurality of movers in the independent cart system, and each of the first mover and the at least one additional mover is comprised within the chain of movers; a first segment controller, wherein the first segment controller is located in a first track segment, the first track segment is selected from the plurality of track segments, and the first segment controller is configured to control operation of the first mover when the first mover is present in the first track segment; and at least one additional segment controller, wherein the at least one additional segment controller is located in an additional track segment, the additional track segment is selected from the plurality of track segments, and the at least one additional segment controller is configured to control operation of the at least one additional mover when the at least one additional mover is present in the additional track segment, wherein: the first segment controller is configured to obtain a desired motion trajectory for the first mover, the first segment controller is configured to transmit the desired motion trajectory to the at least one additional segment controller, the at least one additional segment controller is configured to detect that the at least one additional mover is unable to follow the desired motion trajectory, the at least one additional segment controller is configured to determine a desired suppression for the at least one additional mover, wherein the suppression is a value for modifying the desired motion trajectory into a modified motion trajectory such that the at least one additional mover is able to follow the modified motion trajectory, the at least one additional segment controller is configured to transmit the desired suppression to the first segment controller, and the first segment controller is configured to modify the desired motion trajectory for the first mover into the modified motion trajectory according to the desired suppression received from the at least one additional segment controller.

2. The system according to claim 1, wherein: the at least one additional mover comprises a plurality of additional movers, the at least one additional segment controller comprises a plurality of additional segment controllers, the first segment controller is configured to transmit the desired motion trajectory to each of the plurality of additional segment controllers, each of the plurality of additional segment controllers is configured to transmit a desired suppression determined in the corresponding segment controller to the first segment controller, and the first segment controller is configured to modify the desired motion trajectory according to the desired suppression having the largest magnitude.

3. The system according to claim 1, wherein: the at least one additional mover comprises a plurality of additional movers, the at least one additional segment controller comprises a plurality of additional segment controllers, the first segment controller is configured to transmit the desired motion trajectory to an additional segment controller of the plurality of additional segment controllers that is adjacent to the first segment controller, the first segment controller is configured to modify the desired motion trajectory according to the desired suppression determined in the additional segment controller adjacent to the first segment controller. The additional segment controller located adjacent to the first segment controller is configured to determine a new desired motion trajectory from the desired motion trajectory and a desired following distance, The additional segment controller located adjacent to the first segment controller is configured to transmit the new desired motion trajectory to another additional segment controller located one hop distance away, and Each of the additional segment controllers is configured to determine a further new desired motion trajectory from the new desired motion trajectory from the immediately adjacent additional segment controller and the desired following distance.

4. The system of claim 3, wherein, Each of the additional segment controllers is further configured to determine a desired suppression from the new desired motion trajectory of the corresponding additional segment controller and transmit the desired suppression to the first segment controller via each additional segment controller located between the corresponding additional segment controller and the first segment controller.

5. The system of claim 1, further comprising a synchronization controller configured to determine the first mover and the at least one additional mover to define a chain of movers and transmit a motion command to the first segment controller of the first mover.

6. The system of claim 5, wherein, The first segment controller is configured to obtain the desired motion trajectory from the motion command.

7. The system of claim 5, wherein, The motion command transmitted from the synchronization controller to the first segment controller is the desired motion trajectory.

8. The system of claim 1, wherein, The at least one additional segment controller is further configured to: determine a following error from a current position of the at least one additional mover and the desired motion trajectory, and determine the desired suppression from the following error.

9. The system of claim 1, wherein, The first mover and the at least one additional mover are located on one track segment and the first segment controller and the at least one additional segment controller are the same controller.

10. The system of claim 1, wherein: the independent cart system comprises a first track and a second track, the second track is oriented parallel to the first track, the first mover and the first segment controller are located on the first track, and the at least one additional mover and the at least one additional segment controller are located on the second track.

11. A method for synchronizing motion of a plurality of movers in an independent cart system, the independent cart system comprising a track and the plurality of movers configured to travel along the track, wherein, The track comprises a plurality of track segments, the method comprising the steps of: obtaining a desired motion trajectory for a first mover with a first segment controller, wherein the first segment controller is located in a first track segment, the first track segment being selected from the plurality of track segments; transmitting the desired motion trajectory from the first segment controller to at least one additional segment controller, wherein the at least one additional segment controller is located in an additional track segment, the additional track segment being selected from the plurality of track segments, the additional track segment having at least one additional mover located on the additional track segment, and the first mover and the at least one additional mover are configured to travel along the track as a chain of movers; detecting, with the at least one additional segment controller, that the at least one additional mover is unable to follow the desired motion trajectory; determining, with the at least one additional segment controller, a desired suppression of the at least one additional mover, wherein the suppression is a value that is used to modify the desired motion trajectory to a modified motion trajectory such that the at least one additional mover can follow the modified motion trajectory; transmitting the desired suppression from the at least one additional segment controller to the first segment controller; and modifying the desired motion trajectory in the first segment controller according to the desired suppression.

12. The method according to claim 11, wherein: the at least one additional mover comprises a plurality of additional movers, the at least one additional segment controller comprises a plurality of additional segment controllers, the first segment controller is configured to transmit the desired motion trajectory to each of the plurality of additional segment controllers, each of the plurality of additional segment controllers is configured to transmit a desired suppression determined in the corresponding segment controller to the first segment controller, and the first segment controller is configured to modify the desired motion trajectory according to the desired suppression having the largest magnitude.

13. The method according to claim 11, wherein: the at least one additional mover comprises a plurality of additional movers, the at least one additional segment controller comprises a plurality of additional segment controllers, the first segment controller is configured to transmit the desired motion trajectory to an additional segment controller of the plurality of additional segment controllers that is adjacent to the first segment controller, the method further comprising the steps of: determining, with the additional segment controller that is adjacent to the first segment controller, a new desired motion trajectory according to the desired motion trajectory and a desired following distance; transmitting the new desired motion trajectory from the additional segment controller that is adjacent to the first segment controller to another additional segment controller that is one hop distance away; and determining, with each of the additional segment controllers, another new desired motion trajectory according to the new desired motion trajectory from the immediately adjacent additional segment controller and the desired following distance.

14. The method according to claim 13, further comprising the steps of: determining, with each of the additional segment controllers, a desired suppression according to the new desired motion trajectory of the corresponding additional segment controller; and transmitting the desired suppression from the corresponding additional segment controller to the first segment controller via each additional segment controller that is between the corresponding additional segment controller and the first segment controller.

15. The method according to claim 11, further comprising the steps of: defining a chain of movers with a synchronization controller; and transmitting a motion command from the synchronization controller to the first segment controller for the first mover. the first segment controller is configured to obtain the desired motion trajectory according to the motion command.

16. The method of claim 15, wherein, the motion command transmitted from the synchronization controller to the first segment controller is the desired motion trajectory.

17. The method of claim 15, wherein, 18. The method according to claim 11, further comprising the steps of: ​ determining a following error from the current position of the at least one additional mover and the desired motion trajectory using the at least one additional segment controller, and determining the desired suppression from the following error.

19. The method of claim 11, wherein, The first mover and the at least one additional mover are located on one track segment, and the first segment controller and the at least one additional segment controller are the same controller.

20. The method of claim 11, wherein: The independent cart system includes a first track and a second track, The second track is oriented parallel to the first track, The first mover and the first segment controller are located on the first track, and The at least one additional mover and the at least one additional segment controller are located on the second track.

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