JP2010033402A - Time management system and method for conveyance system, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a time difference between a main control means and a plurality of sub-control means in a time management system for managing the time in respective sections of a conveyance system for conveying a conveyed matter, such as various kinds of substrates for semiconductor manufacture, and perform normal conveyance in accordance with a conveyance schedule. <P>SOLUTION: A time management system (100) includes: a reference time distribution means (12), provided on the side of a main control means (11), for setting and distributing a reference time available as a reference for the time management system; a self time setting means (3), provided in each of a plurality of sub-control means (2), for setting the self time to be referred to for conveyance control by each of the plurality of sub-control means; a time difference acquisition means (3), provided in each of the plurality of sub-control means, for acquiring a time difference between the distributed reference time and the set self time; and an update means (3), provided in each of the plurality of sub-control means, for updating the set self time stepwise according to the obtained time difference. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of a time management system and method for managing time in each part of a transport system for transporting a transported object such as various substrates for manufacturing semiconductor elements. The present invention further relates to the technical field of computer programs that cause a computer to function as such a time management system.

  As this type of time management system, for example, the time of a plurality of devices that can be connected to the network and connected to the same network is obtained, the unified time is determined, and the self time is adjusted to the unified time. (See Patent Document 1).

JP 2005-228010 A

  However, according to the time management system of Patent Document 1 described above, the self time of all devices connected to the network can be adjusted to a unified time, but there is no disclosure regarding the timing and period for performing the adjustment. In this regard, the problems found by the inventor in particular are as follows.

  That is, for example, a self time used as a control parameter by a control unit such as a controller is a time indicated by an OS (Operating System) such as Windows (registered trademark) installed in a host computer (ie, OS time). It is adjusted according to the time difference. However, the OS time may be changed by an operator, automatic change by daylight saving time, or automatic adjustment by RTC (Real Time Clock), for example. In this case, while the time series of processes are executed, the self time may be reversed, or the self time may be skipped during the process performed for a certain period of time.

  Specifically, due to the backward movement of the self time, for example, the time “10:00:00” when the carriage starts to enter the delivery position of the load and the time “9:59:00” when the entry ends are timed. There is a technical problem that it is considered that an error has occurred in the transfer system timer that measures the entry time of the carriage, and the transfer system may be stopped. In addition, due to the skipping of the self time, for example, the monitoring process by the transfer system timer is performed for 15 seconds at normal time, but the monitoring process times out before 15 seconds elapses, and an illegal process is executed. There is a technical problem that may occur.

  In addition, there is a technical problem that the information specifying the control parameters such as log data and statistical data cannot be validated due to the above-described reversal and jump of the self time.

  The present invention has been made in view of the above-described problems, for example, eliminates the time difference between the main control means included in the transport system and the plurality of sub-control means managed by the transport system, and transports according to the transport schedule. It is an object of the present invention to provide a time management system and method that enable normal execution of a computer program, and a computer program that causes a computer to function as such a time management system.

  In order to solve the above-described problem, the time management system of the transport system according to the present invention transports the plurality of transport means by at least one of the main control means and each of the plurality of sub-control means managed by the main control means. A time management system for managing time in a transport system that sets a transport schedule at the time and controls transport of the plurality of transport means along the transport schedule that is established, and is provided on the main control means side. A reference time serving as a reference in the time management system, and provided in each of the plurality of sub-control means, a reference time distribution unit that distributes the set reference time every predetermined period, A self-time setting means for setting a self-time to be referred to when each of the sub-control means performs the transport control; and a plurality of sub-control means Provided in each of the plurality of sub-control means, and a time difference acquisition unit that acquires a time difference between the distributed reference time and the set self time, and the acquired time difference In response, update means for updating the set self time stepwise.

  According to the time management system of the transport system of the present invention, the time management system is applied to a transport system including, for example, an OHT (Overhead Hoist Transport). In the transport system, for example, a transport schedule when the transported object is transported is set by the main control means. Then, the main control means instructs the sub control means to convey the object to be conveyed along the conveyance schedule. Then, according to the instruction | indication, a some conveyance means is conveyed by the some sub control means. Here, “transport control” is control related to, for example, loading and transfer of a transported object to be transported, traveling to a transport source and a transport destination, and the like.

  In the present invention, for example, while the conveyance control is performed, the reference time is set by the reference time distribution unit, and the set reference time is distributed to the plurality of sub-control units, for example, every few seconds. Here, the “reference time” is, for example, the OS time of Windows installed in the host computer, or a time specified based on the OS time. Such a reference time is read directly from the host computer by the main control means connected to the host computer, or is set based on the read OS time and a tick count value difference described later. Subsequently, when the reference time from the reference time distribution unit is received by each of the plurality of sub control units, a time difference between the reference time and the self time set by the self time setting unit is acquired. The Here, the “self time” is a time unique to each sub-control unit, and is a time read when carrying control is performed.

  Subsequently, the self-time by the self-time setting means is updated stepwise by the updating means according to the time difference by the time difference obtaining means. Here, “update in stages” means that the own time is advanced by the minimum unit time (for example, 1.0 second) of the parameter, for example. It also means that the self time is advanced a plurality of times at a fixed time or an indefinite time. Here, the “minimum unit time” is preferably a time at which, for example, when the self time is advanced, the conveyance control is not determined to be an error or is not processed illegally. By such stepwise update, the time difference between the reference time and the self time becomes zero.

  As described above, the self-time set in each of the plurality of sub-control means is adjusted to the reference time set in the main control means, so that in the time management system, between the main control means and the plurality of sub-control means. It becomes possible to eliminate the time difference between. In particular, when the self time is adjusted to the reference time, the self time is advanced stepwise toward the reference time, thereby minimizing the influence on the transport control of a plurality of transport means and following the transport schedule. It becomes possible to carry out the transfer normally.

  The system to which the present invention is applied includes, for example, a semiconductor element manufacturing process instructed by a manufacturing instruction means such as MCS (Material Control System) in a factory for manufacturing a semiconductor element, for example, in addition to the transport system described above. For example, a FOUP (Front Opening Unified Pod) that accommodates various substrates for manufacturing a semiconductor element is transported between, for example, a plurality of areas, and various processes are performed on the transported FOUP to manufacture a semiconductor element. A manufacturing system is included.

  In one aspect of the time management system of the transfer system of the present invention, the main control means sets at least a part of the transfer schedule, and the reference time becomes a reference when setting at least a part of the transfer schedule.

  According to this aspect, at least a part of the transport schedule is established by the main control means with reference to the reference time. Therefore, by matching the self time set in each sub-control unit with the reference time, it is possible to normally carry the transfer according to the transfer schedule.

  In another aspect of the time management system of the transport system of the present invention, the plurality of sub-control means sets at least a part of the transport schedule, and the self time is a reference for setting at least a part of the transport schedule. It becomes.

  According to this aspect, for example, at least a part of the transport schedule is set based on the self time by the plurality of sub-control units. Therefore, by adjusting the self time to the reference time, the self time is unified among the plurality of sub-control means, and it is possible to normally execute the conveyance according to the conveyance schedule.

  In another aspect of the time management system of the present invention, when the acquired time difference is larger than a predetermined threshold, the updating unit advances the acquired self time by the predetermined threshold and acquires the acquired When the time difference is greater than zero and less than the predetermined threshold, the acquired self time is matched with the distributed reference time, and the self time is stopped when the acquired time difference is less than zero. Let

  According to this aspect, first, for example, when the time difference is acquired by the time difference acquisition means, it is determined whether the time difference is larger than a predetermined threshold, larger than zero and smaller than the predetermined threshold, or smaller than zero. Is done. Here, the “predetermined threshold value” is a threshold value that serves as a reference for determining whether or not to update the self time step by step. The “predetermined threshold value” is obtained as a time that does not affect the transport control even if a time jump occurs due to the self time being advanced toward the reference time, for example, experimentally, empirically, or by simulation. And set in advance in a built-in memory or the like. The “predetermined threshold value” may be, for example, the minimum unit time (for example, 1.0 second) of the parameter.

  Then, when the time difference is larger than the predetermined threshold, the self time is advanced by the predetermined threshold by the updating means. That is, the reference time is approximated by a predetermined threshold value. On the other hand, if the time difference is greater than zero and less than a predetermined threshold, the self time is matched with the reference time. That is, the self time is adjusted to the reference time. On the other hand, when the time difference is smaller than zero, the self time is stopped. That is, it is in a state of waiting for the reference time to catch up with the stopped self time. The “when larger than the predetermined threshold” may be “when it is equal to or greater than a predetermined time” or may be “when it is later than the predetermined time”.

  As described above, when the time difference is larger than the predetermined threshold value, the self time is advanced by the predetermined threshold value toward the reference time, so that the self time flies by the time corresponding to the predetermined threshold value. This makes it possible to minimize the influence on the transport control of the plurality of transport means, which is extremely advantageous in practice.

  In this aspect, when the acquired time difference is smaller than zero, the update unit may stop the self time until the distributed reference time catches up with the acquired self time.

  If comprised in this way, if it determines with a time difference being smaller than zero by an update means, self time will be stopped once. Thereafter, when the reference time catches up with the self time, the stop of the self time is released. Thus, by not reversing the self time, it is possible to minimize the influence on the transport control of the plurality of transport means.

  In another aspect of the time management system of the present invention, the plurality of sub-control units are set in a plurality of computers, respectively, and each of the plurality of sub-control units is started after each of the plurality of computers is activated. A current tick count value indicating a count value until the distributed reference time is received, and a reference tick count value indicating a count value from when each of the plurality of computers is started until the self time is updated last time Tic count value difference acquisition means for acquiring a tick count value difference obtained by subtracting the reference tick count value from the specified current tick count value, and the set self time is obtained Includes tick count value difference.

  According to this aspect, when each of the plurality of sub-control units sets the self time, the tick count value difference between the current tick count value and the reference tick count value is acquired by the tick count value difference acquisition unit. . Here, the “count value” is, for example, a value counted from the time when each of a plurality of computers (in other words, Windows installed in each computer) is activated. By including such a difference in count values (that is, a tick count value difference) in the self time, it becomes possible to set the self time in each of the plurality of sub-control means more accurately.

  In order to solve the above problems, the time management method for a transport system according to the present invention transports a plurality of transport means by at least one of a main control control means and a plurality of sub-control means managed by the main control means. A time management method for managing a time in a transport system that sets a transport schedule at the time of carrying out and controls the transport of the plurality of transport means along the established transport schedule, and is provided on the main control means side A reference time distribution step for setting a reference time as a reference in the time management system and distributing the set reference time every predetermined period; and each of the plurality of sub-control means, A self-time setting step for setting a self-time to be referred to when each of the sub-control means performs the conveyance control, and each of the plurality of sub-control means A time difference acquisition step of acquiring a time difference between the distributed reference time and the set self time, and each of the plurality of sub-control means, and according to the acquired time difference And an update process for updating the set self time step by step.

  According to the time management method of the transport system of the present invention, it is possible to eliminate the time difference between the main control means and the plurality of sub-control means as in the case of the time management system according to the present invention described above. In addition, it is possible to minimize the influence on the transport control of the plurality of transport means, and to normally perform transport according to the transport schedule.

  Note that the time management method of the present invention can also adopt various aspects similar to the various aspects of the time management system of the present invention described above.

  In order to solve the above problems, the computer program according to the present invention is configured so that at least one of the main control means and the plurality of sub-control means managed by the main control means transports the plurality of transport means. In the transfer system that sets a schedule and controls transfer of the plurality of transfer means along the set transfer schedule, a computer provided in a time management system that manages time is provided on the main control means side, A reference time serving as a reference in the time management system is set, and a reference time distribution unit that distributes the set reference time every predetermined period, and each of the plurality of sub-control units, Self-time setting means for setting a self-time to be referred to when each of the control means performs the conveyance control; Provided in each of the control means, and provided in each of the plurality of sub-control means, the time difference acquisition means for acquiring a time difference between the distributed reference time and the set self time, and the acquired According to the time difference, it functions as update means for updating the set self time stepwise.

  According to the computer program of the present invention, if the computer program is read from a recording medium such as a CD-ROM or DVD-ROM storing the computer program and then executed by a computer provided in the time management system, or If the computer program is executed after being downloaded through the communication means, the time management system according to the present invention described above can be constructed relatively easily. As a result, as in the case of the time management system according to the present invention described above, it is possible to eliminate the time difference between the main control means and the plurality of sub-control means. In addition, it is possible to minimize the influence on the transport control of the plurality of transport means, and to normally perform transport according to the transport schedule.

  It should be noted that the computer program of the present invention can also adopt various aspects similar to the various aspects of the time management system of the present invention described above.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of the time management system according to the embodiment will be described. FIG. 1 functionally shows the configuration of the time management system according to the embodiment.

  In FIG. 1, a manufacturing system 200 to which a time management system 100 according to the present embodiment is applied includes a plurality of transfer controllers 2 (2a, 2b... 2x), a transfer instruction unit 10, and a manufacture instruction unit 20. The manufacturing system 200 transports a FOUP (not shown) to a stocker (or stacker) that is a working device (not shown) and a manufacturing apparatus according to a semiconductor element manufacturing process, and performs various processes on the transported FOUP.

  The manufacturing instruction unit 20 is an MCS, and transmits a signal indicating a transfer process related to the transfer of FOUP in the semiconductor element manufacturing process to the transfer instruction unit 10. The manufacturing instruction unit 20 includes a host computer 21, and an OS is installed in the host computer 21.

  The conveyance instruction unit 10 is an OHVC (Overhead Hoist Vehicle Control), and is connected to the manufacturing instruction unit 20 and the plurality of conveyance controllers 2 by wires. The conveyance instruction unit 10 includes a master controller 11.

  As an example of the “main control unit” according to the present invention, the master controller 11 sets a transport schedule based on a reference master time, which will be described later, according to a transport process from the manufacturing instruction unit 20. The master controller 11 transmits a signal indicating the identification number of the FOUP to be transported and the transport source and transport destination to the plurality of transport controllers 2 in accordance with the transport schedule. The master controller 11 includes a master time management unit 12 that incorporates a clock.

  As an example of the “reference time distribution unit” according to the present invention, the master time management unit 12 reads a time (ie, OS time) T0 indicated by the OS of the host computer 21 at a predetermined time, and at the read OS time T0. Based on this, the reference master time Tm (that is, an example of “reference time” according to the present invention) is set. The clocking (that is, counting) of the reference master time Tm is started, for example, when the conveyance instruction unit 10 or the master controller 11 is turned on, that is, at startup.

  Next, a method for setting the reference master time Tm will be described with reference to FIG. FIG. 2 shows a table used when setting the reference time according to the embodiment.

  The master time management unit 12 includes a memory (not shown). In FIG. 2, a table 41 for setting the reference master time Tm is stored in the memory.

The table 41 has three items of “parameter name”, “parameter (variable)”, and “calculation formula”. In the table 41, “OS time” is a parameter “T 0” indicating the time possessed by the OS of the host computer 21. The “reference master time difference” is a parameter “Tm” indicating the time difference between the OS time T0 and the reference master time Tm (that is, indicated by a calculation formula “T0−Tm”). The “current tick count value” is a parameter “Tc” indicating the current tick count value counted from the time of activation by the master time management unit 12. The “reference tick count value” is a parameter “Tr” indicating a tick count value from the time of startup until the previous reference master time Tm is updated. The “tick count value difference” is a parameter “Tcr” (in other words, expressed by a calculation formula “Tc−Tr”) indicating a difference in tick count value between the current tick count Tc and the reference tick count value Tr. The “reference master time” is a parameter “Tm” indicating the time of delivery to each of the plurality of transport controllers 2 (2a, 2b... 2x), and is represented by Expression (1) for the first time.
Tm = T0 + Ts (1)

The reference master time Tm is expressed by Expression (2) after the second time.
Tm = previous Tm + Tcr (2)

  The master time management unit 12 records or updates the above-described parameters in the table 41, and sets the reference master time Tm set by the formula (1) or the formula (2) for every fixed period (for example, 4 seconds). For each of the plurality of transport controllers 2.

  In FIG. 1, a plurality of transfer controllers 2 correspond to a plurality of areas A (A1, A2,... Ax) each including one or a plurality of work devices. Each transport controller 2 functions as a part of the OHT as an example of the “sub control unit” according to the present invention, and controls the vehicle 1 existing inside the corresponding area A. Specifically, based on a signal from the transport instruction unit 20, the transport controller 2a loads the FOUP to be transported at the transport source and then transports the stacked FOUP to the vehicle 1a so as to transport to the transport destination. (In other words, transport control of the vehicle 1a is performed). Each transport controller 2 includes a time management unit 3 (3a, 3b... 3x).

  The time management unit 3 sets its own master time Tmx as an example of “self time setting means”, “time difference acquisition means”, and “update means” according to the present invention.

  Next, a method for setting the self master time Tmx will be described with reference to FIG. FIG. 3 shows a table used when setting the self time according to the embodiment.

  The time management unit 3 includes a memory (not shown). In FIG. 3, a table 42 for setting the self master time Tmx is stored in the memory.

Similar to the table 41 in FIG. 2, the table 42 includes three items “parameter name”, “parameter (variable)”, and “calculation formula”. Regarding the table 42, “reference master time” is a parameter “Tm” indicating the reference master time set by the master time management unit 12. The “current tick count value” is a parameter “Tcx” indicating the current tick count value counted by the time management unit 3 from the time of activation. The “reference tick count value” is a parameter “Trx” indicating a tick count value from the time of startup until the previous self-master time Tmx is updated. The “tick count value difference” is a parameter “Tcrx” (that is, expressed by a calculation formula “Tcx−Trx”) indicating a difference in tick count value between the current tick count Tcx and the reference tick count value Trx. The “self master time” is a parameter “Tmx” indicating the time that the self has, and is represented by Expression (3).
Tmx = previous Tmx + Tcrx (3)

  The time management unit 3 records or updates the above-described parameters in the table 42 when receiving the reference master time Tm from the master time management unit 12. Each transport controller 2 controls each part of the vehicle 1 based on the self-master time Tmx set by the equation (3).

  Each transport controller 2 compares the reference master time Tm from the master time management unit 12 with the self master time Tmx, and indicates a difference between these binary times (hereinafter referred to as “binary time difference”). The parameter “Tdef” (that is, indicated by the calculation formula “Tm−Tmx”) is calculated. In the present embodiment, each transport controller 2 performs various time adjustment processes for making the self master time coincide with the reference master time according to the calculated binary time difference Tdef.

Next, the time adjustment process will be described. Each transport controller 2 performs time adjustment processing when the binary time difference Tdef is greater than 1 second (ie, the reference master time Tm is 1 second earlier than the self-master time Tmx), as shown in Expression (4). As shown in the equation (5), the self master time Tmx is advanced by 1 second.
Tm−Tmx ≧ 1 (4)
Tmx = previous Tmx + 1 (5)

Further, as shown in the equation (6), when the binary time difference Tdef is larger than zero and smaller than one second (that is, the reference master time Tm is zero to one second earlier than the self master time Tmx), the time adjustment is performed. As a process, as shown in Expression (7), the self master time Tmx is matched with the reference master time Tm.
0>Tm−Tmx> 1 (6)
Tmx = Tm (7)

Further, as shown in Expression (8), when the binary time difference Tdef is smaller than zero (that is, the reference master time Tm is later than the self master time Tmx), the time adjustment process is not performed. Instead, the self master time Tmx is temporarily stopped, and the stop is released when the reference master time Tm catches up with the self master time Tmx.
Tm−Tmx <0 (8)

(Time management processing)
Next, time management processing in the time management system according to the embodiment will be described with reference to FIG. FIG. 4 is a flowchart illustrating the time management process according to the embodiment. The time management process includes the time adjustment process described above, and is executed at regular intervals while the conveyance control of the vehicle 1 is performed according to the conveyance schedule.

  In FIG. 4, first, the master controller 11 sets a reference master time Tm and distributes it to each transport controller 2 (step S51). Then, each transport controller 2 determines whether or not the reference master time Tm has been received (step S52). As a result of this determination, when the reference master time Tm is not received (step S52: NO), the process waits until it is received.

  On the other hand, when the reference master time Tm is received by the determination in step S51 (step S52: YES), a time difference Tdef between the received reference master time Tm and the self master time Tmx is calculated (step S53). ). Then, it is determined whether or not the calculated time difference Tdef is 1 second or longer (step S54). If it is determined that the time is 1 second or longer (step S54: YES), “1” is added to the self master time Tmx, and the self master time Tmx is advanced by 1 second (step S55). Thereby, a series of time management processing is completed.

  On the other hand, if it is determined in step S54 that the time difference Tdef is not 1 second or more (step S54: NO), it is determined whether the time difference Tdef is greater than zero and less than 1 second (step S56). If it is determined that the time is greater than zero and less than 1 second (step S56: YES), the self master time Tmx is matched with the reference master time Tm (step S57), and a series of time management processes are terminated.

  On the other hand, if it is determined in step S56 that the time difference Tdef is smaller than zero, the self master time Tmx is stopped until the time difference Tdef becomes zero (step S58). Thereby, a series of time management processing is completed.

  As described above, according to the time management process of the present embodiment, the self-master time Tmx set in each of the plurality of transport controllers 2 is matched with the reference master time Tm set in the master controller 11, thereby In the time management system 100, the time difference between the master controller 11 and the plurality of transport controllers 2 can be eliminated. Further, when the self master time Tmx is adjusted to the reference master time Tm, the self master time Tmx is advanced stepwise toward the reference master time Tm, thereby minimizing the influence on the transport control of the plurality of transport controllers 2. Therefore, it is possible to normally carry along the carrying schedule.

  Therefore, especially when the reference master time Tm, which is the OS time, is changed by an operator, automatically changed by daylight saving time, or automatically adjusted by RTC (Real Time Clock), there is almost no trouble in a practical sense. The normal operation can be resumed or the normal operation can be continued. That is, even in such a case, it is possible to prevent the conveyance system from being stopped, and it is possible to ensure the validity of information specifying control parameters such as log data and statistical data.

  In the present embodiment, the transport controller 2 is set for each region A as a controller for controlling the transport of the vehicle 1. However, the transport controller including the time management unit 3 is set without setting the transport controller 2 at all. The controller of the vehicle 1 may have two functions. In this case, the reference master time Tm is directly distributed from the master time management unit 12 to the vehicle 1. Then, according to the time difference between the reference master time Tm and the self-master time Tmx on the vehicle 1 side, the self-master time Tmx on the vehicle 1 side is adjusted stepwise to the reference master time Tm, so that the conveyance instruction unit The time difference between 10 and the vehicle 1 is eliminated.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. A management system and method, and a computer program are also included in the technical scope of the present invention.

It is a block diagram which shows the structure of the manufacturing system to which the time management system which concerns on embodiment is applied. It is a table used for the setting of the reference time which concerns on embodiment. It is a table used for the setting of the self time which concerns on embodiment. It is a flowchart which shows the time management process which concerns on embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Conveyance controller, 3 ... Time management part, 11 ... Master controller, 12 ... Master time management part, 100 ... Time management system

Claims (8)

At least one of each of the main control means and the plurality of sub-control means managed by the main control means establishes a transport schedule when transporting the plurality of transport means, and along the established transport schedule, In a transport system that controls transport of a plurality of transport means, a time management system that manages time,
A reference time distribution unit that is provided on the main control unit side, sets a reference time as a reference in the time management system, and distributes the set reference time every predetermined period;
A self-time setting unit that is provided in each of the plurality of sub-control units, and sets a self-time that is referred to when each of the plurality of sub-control units performs the transport control;
A time difference acquisition means provided in each of the plurality of sub-control means, for acquiring a time difference between the distributed reference time and the set self time;
A time management system for a transport system, comprising: an update unit provided in each of the plurality of sub-control units, and updating the set self time stepwise according to the acquired time difference . The main control means sets at least a part of the transport schedule,
The time management system for a transfer system according to claim 1, wherein the reference time is a reference for setting at least a part of the transfer schedule. The plurality of sub-control means establish at least a part of the transport schedule,
The time management system for a transport system according to claim 1 or 2, wherein the self time is a reference for setting at least a part of the transport schedule. The updating means advances the acquired self time by the predetermined threshold when the acquired time difference is greater than a predetermined threshold, and the acquired time difference is greater than zero and greater than the predetermined threshold. The acquired self time is matched with the distributed reference time when the time is smaller, and the self time is stopped when the acquired time difference is smaller than zero. The time management system of the conveyance system as described in any one. The said update means stops the said self time until the said distributed reference time catches up with the said acquired self time, when the said acquired time difference is smaller than zero. Time management system for the transport system of The plurality of sub-control means includes
It is set for each of multiple computers.
A current tick count value indicating a count value from when each of the plurality of computers is activated until each of the plurality of sub-control means receives the distributed reference time, and each of the plurality of computers is activated A tick count is obtained by specifying a reference tick count value indicating a count value until the self time is updated last time and subtracting the reference tick count value from the specified current tick count value. Each has a value difference acquisition means,
The time management system for a transport system according to any one of claims 1 to 5, wherein the set self time includes the acquired tick count value difference. At least one of the main control means and each of the plurality of sub-control means managed by the main control means establishes a transport schedule when transporting the plurality of transport means and follows the established transport schedule. In a transport system that controls transport of the plurality of transport means, a time management method for managing time,
A reference time distribution step that is provided on the main control means side, sets a reference time as a reference in the time management system, and distributes the set reference time every predetermined period;
A self-time setting step that is provided in each of the plurality of sub-control units and sets a self-time that is referred to when each of the plurality of sub-control units performs the transport control;
A time difference acquisition step provided in each of the plurality of sub-control means to acquire a time difference between the distributed reference time and the set self time;
A time management method for a transport system, comprising: an update step that is provided in each of the plurality of sub-control means and updates the set self time stepwise according to the acquired time difference. . At least one of the main control means and each of the plurality of sub-control means managed by the main control means establishes a transport schedule when transporting the plurality of transport means and follows the established transport schedule. In a transport system that performs transport control of the plurality of transport means, a computer provided in a time management system that manages time,
A reference time distribution unit that is provided on the main control unit side, sets a reference time as a reference in the time management system, and distributes the set reference time every predetermined period;
A self-time setting unit that is provided in each of the plurality of sub-control units, and sets a self-time that is referred to when each of the plurality of sub-control units performs the transport control;
A time difference acquisition means provided in each of the plurality of sub-control means, for acquiring a time difference between the distributed reference time and the set self time;
A computer program that is provided in each of the plurality of sub-control means and functions as update means that updates the set self time stepwise according to the acquired time difference.

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