Abstract:
An autonomous and decentralized production control system comprising a plurality of production cells for performing the assembly and machining work. Each production cell proceeds with the production procedure by performing jobs in accordance with the works charged thereinto. A first embodiment comprises working cells each including a device for determining the working cell for executing an intended job. A second embodiment comprises a pallet for carrying an object of a job, and a device for determining the order of job priority in order to meet the product delivery time. Each working cell decides on the advisability and time of performing the job on the object, thereby autonomously implementing the production control.

Description:
This application is a continuation-in-part of Ser. No. 07/977,249, filed Nov. 16, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a production control system, or more in particular to an apparatus, equipment and a control system required for constructing a flexible production system. 
     2. Description of the Prior Art 
     In conventional production control systems, an operating schedule is formed on the basis of a product specification for each piece of production equipment, equipment control data for implementing a job for each piece of equipment is prepared and stored in the related equipment, and the job is performed according to the operating schedule. These conventional systems require a system shutdown to correct equipment control units and the operating schedule to alter the product specification or the production equipment. A similar system shutdown and repair work is also required when fault of an equipment part occurs. 
     A solution to these problems has been suggested by “Production Control System of Process-Led Operation Selection Type” disclosed in JP-A-1-321503 and “Information Processing System for Processing Cells of Autonomous and Decentralized Type” in JP-A-2-236604, in which the equipment is not assigned with any job but autonomously selects and proceeds with a job for the work to thereby construct a flexible production control system. 
     According to the prior art disclosed in JP-A2-236604 primarily intended for a processing job, for example, each working cell making up a production control system conducts the job on its own as required on the basis of the processing information, etc. added to the work charged thereto. Also, a plurality of working cells having substantially the same specification are arranged to provide system flexibility, and makes possible the operation of a replacement cell when a cell malfunctions while at the same time assuring load equalization among different cells. 
     In the prior art systems described above, the equipment simply receives an incoming work and decides whether or not it is capable of performing the next job on the particular work. More specifically, if a job is capable of being performed, the equipment never fails to implement the next job. This system necessitates information exchange only with a single work in selecting a job, and therefore the algorithm for job selection is simple and causes no interference with the remaining equipment. In view of the fact that the equipment concentrates on a single work for job selection, however, the information regarding the remaining works is not taken into consideration in job selection. As a result, the delivery time of a particular product is disregarded. This not only makes it difficult to predict the completion time of a product, but also no priority is given even to a work of urgent necessity. 
     Where there are a plurality of works intended for a given job, the job is conventionally performed on first-come-first-served basis but no consideration is given to the order of priority based on delivery time or the like. As a consequence, a work with a short lead time, or especially, a work whose processing is of urgent necessity is unavoidably placed in the hands of the operator. Further, since works are controlled by work type, an urgent work which may occur cannot be processed until completion of a job on all the works of a particular work type in the process of operation. 
     In conventional systems, the processing operations required for works are similar to each other, and therefore flexibility could be simply obtained by a parallel arrangement of a plurality of cells of the same specification. In such production control systems, the workability including the possibility of a given job in other cells and the time required for the job are known in advance and need not be confirmed. 
     Nevertheless, in the assembly work which unlike the processing work has a smaller similarity between the jobs performed on different works, a system is difficult to construct only with cells of substantially the same specification. A production control system including the assembly work, therefore, requires an arrangement of cells having different functions. This requirement is not fully met by conventional production control systems which fail to confirm the workability of other cells as described above. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a highly flexible autonomous and decentralized production control system for performing a job in accordance with the order of work priority in order to meet the delivery time of a particular product. 
     Another object of the present invention is to provide a highly flexible autonomous and decentralized production control system which easily meets a change in product specification or equipment configuration or an equipment malfunction without sacrificing production efficiency. 
     Still another object of the present invention is to provide an autonomous and decentralized production control system which meets a job requirement involving a number of dissimilar jobs as in an assembly work. 
     According to the present invention which has been made in order to achieve the above-mentioned objects, there is provided a work administration system comprising a storage unit for storing a work intended for job performance and the information for a job to be performed on the work, transport unit for delivering the work out of or into the storage unit, and work administration unit having the administration information on the works in the storage unit, deciding the order of priority of the works in accordance with the work administration information and causing the transport unit to deliver the top-priority work and/or the job information on the particular work. 
     The work administration information preferably contains at least one of the information including the time of delivering the work into the storage unit and the required completion time of the job. 
     The work administration system further comprises communication unit for transmitting information with a working cell performing the job on a work. The work administration unit preferably decides the order of priority when a “work demand” is received from the working cell through the communication unit and outputs the job information of the top-priority work through the communication unit. Further, the work administration unit preferably causes the work and/or the job information on the work to be delivered through the communication unit at the time work output instruction is received from the working cell. 
     The work and/or the job information is preferably delivered out for a demanding working cell at a demanded time in accordance with the output instruction. 
     According to another aspect of the present invention, there is provided a working cell for performing the job of an intended work, comprising an input unit for inputting the job information including information of at least one job, a job execution unit for actually carrying out the job, an inter-cell communication unit for exchanging information with other working cells, a job extraction unit for extracting a job to be performed first at the time point, job workability decision unit for deciding whether or not a job can be implemented by the job execution unit and answering an inquirer, and working cell determining unit for making inquiry as to the workability of a job extracted from the job extracting unit, through the inter-cell communication unit from the workability decision unit for other working cells and directly from the job workability decision unit for its own working cell to thereby determine a working cell for executing the job on the basis of the answer to the inquiry. 
     The input unit may be communication unit for transmitting and receiving information to and from the work administration system for managing works, and the working cell determination unit may have the function of demanding the job information for a new work from the work administration system through the communication unit. 
     The workability decision unit, when a particular job under inquiry is executable, may cause the answer to contain at least one of the information including not only the workability of the particular job but also the time when the job can be started, the scheduled time of job completion and the type of job executable by the working cell. In such a case, the system may comprise a self-monitoring unit for monitoring the progress of job execution by the job execution unit and deciding that a particular cell is out of order when the job cannot be completed before the scheduled job completion time. 
     According to a further aspect of the present invention, there is provided an autonomous and decentralized production control system comprising a plurality of working cells for executing a job, a work administration system for managing the works to be processed, network unit for connecting the working cells to each other and the working cells to the work administration system for exchanging information. The working cells include a job extraction unit for actually executing a job; a job extracting unit for extracting a job to be executed first of all at the time point from the job information input from the work administration system through the network unit; a workability decision unit for receiving an inquiry as to whether a job is executable or not, deciding on whether the job is executable by the job execution unit and giving an answer to the inquirer; a working cell determining unit having the function of outputting a “work demand” to the work administration system through the network unit; and making an inquiry to the workability decision unit for other cells through the network unit and directly to its own workability decision unit to determine a working cell for executing the job on the basis of the answer to the inquiry. The work administration system includes a storage unit for storing job information indicating the work intended for a job and the job to be performed on the work, a transport unit for delivering the work out of or into the storage unit, and a work administration unit for deciding the order of priority of works on the basis of the work administration information upon receipt of a “work demand” from the working cell determining unit and outputting the job information on the top-priority work on the one hand while at the same time causing the transport unit to deliver the top-priority work and/or the job information in accordance with an output instruction from the working cell determining unit. 
     As second unit for solving the above-mentioned problems of the conventional systems, according to the present invention, there is provided an autonmous and decentralized production control system in which a pallet with a work placed thereon has the functions of selecting the equipment, determining the order of work priority and requesting a job. This system is called a “work driven production control system”. 
     According to the present invention, each time a work on a pallet is newly charged, the priority of its own work is transmitted through an inter-pallet communication unit to a work priority storage unit. A job request right effectuation unit reads information out of the work priority storage unit, and assigns the job request right to the pallets carrying the particular work in the descending order of priority. The equipment selection unit for a pallet that has acquired the job request right issues the next job for the work to the equipment. The job work workability decision unit of the equipment determines whether the job is executable or not, and replies to the equipment. If executable, the equipment selection unit request the job of the equipment. The equipment in turn issues a job request completion report to the job request effectuation unit. If the job is impossible to execute, on the other hand, the pallet transmits the decision to the job request right effectuation unit as a non-selectability notice. Thus the pallet waits for the next chance of job selection. The job request right effectuation unit, upon receipt of a non-selectability notice from a pallet, grants the job request right to the pallet ranking next in the order of priority. 
     Upon job completion, the work information after job completion is transmitted from the equipment to the pallet carrying a work and an equipment job completion report to the work priority determining unit. The work priority determining unit recalculates the order of priority from the work conditions at the time of job completion, updates the information of the work priority storage unit, and updates and transmits the information in the work priority storage unit to thereby transmit a work job completion notice to the job request right effectuation unit. 
     The above-mentioned procedure is repeated until every work exercises the job request properly. Negotiations are thus made with the equipment always in the descending order of work priority, and therefore the Product delivery time is taken into consideration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a general configuration of a production control system according to an embodiment of the present invention. 
         FIG. 2  is a diagram showing an example of job information relating to a job conducted on a work. 
         FIGS. 3A  to  3 C are side views of the shapes of works. 
         FIG. 4  is a diagram showing an example of work administration table. 
         FIG. 5  is a diagram showing an example of a work output table. 
         FIG. 6  is a diagram showing an example of a work input table. 
         FIG. 7  is a flowchart of Procedures in cells. 
         FIG. 8  is a flowchart of procedure for delivering works out into cells. 
         FIG. 9  is a flowchart of procedure for receiving works from cells. 
         FIG. 10  is a diagram schematically showing the procedure conducted on a work. 
         FIG. 11  is a diagram showing a configuration of a production control system of work driven type according to an embodiment of the present invention. 
         FIG. 12  is a diagram showing a configuration according to an embodiment of the present invention in a processing job. 
         FIG. 13  is a diagram showing an example of job information used in an embodiment of the present invention. 
         FIG. 14  is a diagram showing an example of work information used in an embodiment of the present invention. 
         FIG. 15  is a diagram showing an example of information stored in work priority storage unit. 
         FIG. 16  is a diagram showing an example of information stored in equipment information storage unit. 
         FIG. 17  is a flowchart of pallet operation. 
         FIG. 18  is a flowchart of operation of the job request right effectuation unit. 
         FIG. 19  is a flowchart of equipment operation. 
         FIG. 20  is a flowchart of operation of the job request right effectuation unit placed in a pallet. 
         FIG. 21  is a diagram showing a configuration of an embodiment of the present invention for assembly work. 
         FIG. 22  is a diagram showing an example of assembly information used in an embodiment of the present invention. 
         FIG. 23  is a diagram showing an example of work information used in an embodiment of the present invention. 
         FIG. 24  is a diagram showing an example of information stored in the equipment information storage unit. 
         FIG. 25  is a flowchart of pallet operation. 
         FIG. 26  is a flowchart of equipment operation. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described with reference to  FIGS. 1  to  10 . 
     First, a product, a product in process, a part and a material are defined collectively as a “work”, and a group of working machines is defined as “cells”. 
       FIG. 1  shows a general configuration of an autonomous and decentralized production control system. 
     This production control system comprises a work storage section  1  for administering a plurality of works intended for job performance and controlling the work transport to cells, a plurality of cells  2  for conducting the required job on the works, and a work transport section  3  for transporting the works between the work storage section  1  and the cells  2 . 
     First, the work storage section  1  will be described. 
     The work storage section  1  includes a cell communication section  4 , a work administration section  5 , a work storage  7 , a job information storage  8 , a work transport control section  9 , and a work input section  10 . 
     The work input section  10  serves as a gate for the work  12  charged and stores the work  12  in the work storage  7  or the job information  13  relating to the job required for the work  12  in the job information storage  8 . 
     The work storage  7  is for storing the work  12  ready for job performance charged into the system through the work input section  10 . 
     The job information storage  8  is for storing the information on the job required for each work charged into the system, i.e., the job information  13  input through the work input section  10 . The job information  13  will be described in more detail later. 
     The work administration section  5  has the functions to uniformly administer the work  12  stored in the work storage and the job information  13  (which is stored in the job information storage  8 ) relating to the job required for the work  12  in accordance with the work administration table  6  contained therein and to control the order of charging the works into the cells  2 . More specifically, in response to a demand from the cell  2 , a work  12  high in priority is selected, and a copy of the job information  13  for the particular work  12  is transmitted through the cell communication section  4  to the cell  2  acting “chairman” as described later. The work administration section  5  has also the function to order the work transport control section  9  to transport the work  12  and the job information  13  to the cell  2  (which acts as a “person in charge” as described later) actually executing the job on the work  12 . The work administration table  6  will be explained in detail later. 
     The function of the cell communication section  4  is to exchange information on the works with each of a plurality of cells  2 . 
     The work transport control section  9  is for transporting units of the work and the job information  11  the work transportation section  3  between the work storage section  1  and the cell  2 . The work input-output control is effected on the basis of the work output table  14  and the work input table  15  contained in the work transport control section  9 . These tables will be described more in detail later. Now, the cell  2  will be explained. 
     Different cells  2  according to the present embodiment have different jobs executable thereby. 
     Upon completion of a job taken charge of by itself, the cell  2  receives a new job information from the work storage section  1 . The cell  2  does not execute the job in its direct form, but decides whether the job can be executed by other cells  2 . The feature of the cell  2  is that it has the function to determine a cell  2  most suitable for executing the particular job, i.e., a cell  2  which may be called “a person in charge”. In other words, after completion of a job before finding a job considered most suitable for its own direct execution, the cell  2  acts as “chairman” for determining a “person in charge”. 
     Specifically, the cell  2  mainly includes a communication section  16 , a job progress section  19 , a job workability decision section  22  and a job execution section  23 . 
     The communication section  16  is further divided into a work communication section  17  and an inter-cell communication section  18 , which communicate with the work storage section  1  and other cells  2 , respectively. The communication section  16  is connected to the cell communication section  4  and the communication cell  16  of other cells  2  by cable or the like. 
     The job progress section  19  outputs a “work demand” for demanding a new work from the work storage section  1  upon completion of a job that has thus far been executed by the job execution section  23 . A copy of the job information  13  is sent from the work storage section  1  through the cell communication section  4  in response to the demand. The job progress section  19  extracts a job yet to be executed from the copy and makes inquiry to other cells through the inter-cell communication section  18  as to whether the particular job is executable or not. Another function of the job progress section  19  is to determine an actual cell  2  which executes the job thus extracted, on the basis of the answer from other cells  2 . The job progress section  19  has a job cell determination section  21  and a job extraction section  20 * A job yet to be executed is extracted by the latter. The functions including output of a “work demand”, inquiry to other cells  2  and determination of an actual cell  2  executing the job are effected by the job cell determination section  21 . 
     The job workability decision section  22  has the function to decide whether a job to be performed on a work is executable or not as compared with the specification of the particular cell  2  upon receiving an inquiry on job executability. The job workability decision section  22  has therein a specification or the like data on the cell  2  required for decision. Other data not contained therein such as the time of job completion is confirmed by making inquiry to the job execution section  23 . 
     The job execution section  23  is for actually executing a job. The job execution section  23  is further divided into a control data preparation section  24 , an equipment control section  25  and a job result updating section  26 . 
     The control data preparation section  24  is for preparing data and a program for a cell controller and various equipment making up the cell  2  as required for the cell  2  to perform a requested job. 
     The equipment control section  25  controls the equipment making up the cell  2  by use of the data and the program prepared at the control data preparation section  24  and conducts the job on the work  12 . 
     The job result updating section  26  writes the job result such as job completion into the job information  13  at the end of job execution on the work  12 . 
     Each cell  2  is assigned with a cell number for identification. 
     Now, the work transport section  3  will be described. 
     The work transport section  3  transports the work stored in the work storage  7  and the job information stored in the job information storage  8  to the cell  2 , i.e., the “person in charge” for performing an actual job, under an instruction from the work transport control section  9 . More specifically, the work transport section  3  transports not only a work but also a storage medium storing the job information  13 . The work and the job information  11  transported by the work transport section  3  are processed by the job execution section  23  of the cell  2 . 
     Now, the various tables described above will be summarized below. 
     First, reference is made to the job information  13 , which represents the contents of one or more jobs conducted on a work  12  and the corresponding job procedure. 
       FIG. 2  shows an example of the job information  13 . 
     The work number  201  is the number of the work intended for job performance described in the job information  13 . 
     A job completion  202  indicates whether or not the jobs designated in the job information  13  are all complete. 
     A work shape  203  is data indicating the shape of the work before job initiation. In the case where the work has a shape as shown by the side view (showing only the upper part from center) in  FIG. 3A , for example, data required for recognition of the same by the cell  2 , such as (length: 1000 mm, radius: 100 mm, round steel bar) is described. 
     The number of jobs  204  is that of jobs required to be conducted on the work  12 , which is naturally followed by the job contents  205  which number as many as indicated by the number of jobs  204 . According to the present example, two jobs including “job 1” and “job 2” in job identification number are performed. 
     The job contents  205  includes a job name  205   a  at the head thereof. The job name  205   a  has described therein the job name representing a job type. The job name is defined in advance with the cell  2 , etc., which is adapted to discriminate the job type in accordance with the job name. A parameter corresponding to the job is described as the succeeding information. 
     Since “job 1” in this example has a job name “rough machining”, for instance, the accuracy  205   b  and the processing shape  205  are provided as parameters. In this example, therefore, the cell  2  decides according to these parameters that the work should be roughly machined to the shape shown in  FIG. 3B , i.e., 600 mm in the length of the large-diameter portion, 80 mm in radius and 400 mm in the length of a small-diameter portion (55 mm in radius). 
     In the “job 2” of this example, the job name is “finish machining”, and therefore the accuracy  205   b  and the processing shape  205   c  are provided as parameters. On the basis of these parameters, the cell  2  decides in this example that the work should be finish machined up to a shape as shown in  FIG. 3C  (a two-stage shaft 75 mm in the radius of a large-diameter portion and 50 mm in the radius of a small-diameter portion). 
     Further, the number of preceding jobs  205   d  and the preceding job  205   e  are Provided after the Parameters representing the job contents. 
     The number of preceding jobs  205   d  is the number of jobs required to have been completed before starting a particular job. The preceding jobs  205   e , on the other hand, include all the identification numbers of the jobs required to have been completed before starting a particular job. 
     In the case of conducting a plurality of jobs on the work  12 , a partial order of priority holds in view of the fact that there is an order of priority for jobs of some types. Such jobs have an identification number of a job that is required to have been completed in order of priority, indicated as the preceding job  205   e.    
     In the example under consideration, the job 2 (finish machining) is required to be conducted after the job 1 (rough machining). The number of jobs  205   d  preceding to the job 2 is indicated as “1”, and the preceding job  205   e  as “job 1”. In the absence of the job to be previously conducted in order of priority, the number of preceding jobs  205   d  is indicated as “0” as shown in the job 1. No column of the preceding job  205   e  is provided. 
     The job completion  205   f  at the end of the job contents  205  is indicative of whether the particular job has been completed or not. It is necessary before starting with a given job that the job completion  205   f  of every job indicated in the preceding job  205   e  is required to indicate completion. In this example, the indication is “NO” for both jobs 1 and 2, showing that neither of the jobs is complete. 
     Although  FIG. 2  represents an example of job information for the machining job, a substantially similar format is also used for the assembly work. 
     The job information  13  described above is an example and is not limited to the construction described. 
     Now, the work administration table  6  will be explained. 
     The work administration table  6  according to the present embodiment is comprised of a work number  210 , a work condition  211 , an order of charging  212 , a delivery time  213  and an order of priority  214 , as shown in FIG.  4 . 
     The work number  210  is the number of the work charged into the system, and is almost the same value as the work number  201  of the job information  13 . 
     The work condition  211  represents the condition of a work in the system, and includes “ready for job performance” in the work storage  7  of the work storage section  1  and “under job performance” indicating that the job is being conducted at the cell  2 . The work condition  211  is indicated as “ready for job performance” at the time point when the work  12  is charged into the system. Upon determination of the work  2  on which the job is to be performed, the work condition  211  is changed to “job in process”. Even when a particular job is complete, the work is restored in the work storage  7  with the work condition  211  of the corresponding record indicated as “ready for job performance”, if there remains any job yet to be completed. 
     The order of charging  212  is the order in which works are charged into the system. 
     The delivery time  213  is the dead line by which a work is required to be delivered out of the system. 
     The order of priority  214  indicates the order in which works are required to be delivered out to the cell  2 , the works with a smaller number being given a higher priority. According to this example, three items including the order of charging  212 , the delivery time  213  and the order of priority  214  are used as indexes for determining the order of priority of a job. 
     Each work  12  is registered with the work administration table  6  at the time of being charged into the system. When the job at the cell  2  is ended with all the required jobs for the work complete, the work is delivered out of the system and the corresponding record in the work administration table  6  deleted. 
     Now, explanation will be made about the work output table  14  and the work input table  15 . 
     The work output table  14  according to the present embodiment is shown in FIG.  5 . 
     This work output table  14  is configured of a work number  220 , an inward delivery cell number  221  and an inward delivery time  222 . 
     The work number  220  corresponds to the work number  210 , etc. in the work administration table  6  and the like. The received cell number  221 , on the other hand, is described by use of a cell number for identifying the cell  2  described above. 
     In the example shown, the work of the work number  120  is shown to be received at 10 o&#39;clock into the cell  2  of the cell number  05 . It is also shown that the work of the work number  101  is received into the cell  2  of the cell number  03  at 15 minutes past 10 o&#39;clock. 
     The work input table  15  according to the present embodiment is shown in FIG.  6 . 
     This work input table  15  includes a work number  230 , an output cell number  231  and a destination for output  232 . 
     The work number  230  is the number of the work on which the job has been completed. 
     The outward delivery cell number  231  is the number of the cell  2  that issues a message “job completion” and demands output of the work  12 . 
     The output destination  232  is the destination to which the work  12  is delivered out. The items “out of system” and “work storage section” are included in the destination. 
     Now, explanation will be made about the operation of each section performed from delivery of the work  12  into the production control system to output out of the same system. 
     Main processes in the work storage section  1  include the output of the work into the cell  2  and the reception of the work from the cell  2 . The determination of a cell  2  for executing a process and an actual job execution process at the cell  2  are also included in the main processes. These processes will be described one by one below. 
     First, the flow of processing operations in the cell  2  will be described with reference to FIG.  7 . (Step S 121 ) When the cell  2  has completed all the jobs taken charge of and is not yet assigned with other jobs, the job cell determination section  21  transmits a “work demand” message from the work communication section  17  to the work storage section  1  to demand a work. The cell  2  thus subsequently accomplishes the function as “chairman”. 
     (Step S 122 ) In response to the above-mentioned process, the work storage section  1  sends back a copy of the job information  13  representing the top-priority works determined according to a certain index from among the works  12  ready for job performance in the work storage  7 . The wording “a certain index” indicates the order or priority determined by the order of charging  212 , the delivery time  213 , etc., described in the work administration table  6 , as will be explained in detail later. 
     In the case where the work storage section  1  is processing the message “work demand” transmitted from other cells  2 , the message “other work being processed” is sent back. Therefore, the message “work demand” is transmitted again. 
     (Step S 123 ) The job cell determination section  21  extracts the job contents  205  not yet complete as indicated in the job completion  205   f , i.e., the jobs not yet executed, from among the jobs described in the copy of the job information  13  sent from the work storage section  1  (on condition that the jobs  205   e  preceding the particular job are all complete as indicated in the job completion  205   f ). 
     Then the job workability decision section  22  of each cell  2  is referred to as to whether the particular job is executable or not. This inquiry is made direct to the job workability decision section  22  of other cells  22  from the cell  2  by use of the intercell communication section  18 . The inquiry is made not by sending all the job information shown in  FIG. 2  as an example, but by transferring only the job contents  205  about the job extracted by the job extraction section  20 . 
     (Step S 124 ) The job workability decision section  22  of each cell  2 , by comparing the specification of the cell  2  associated therewith and the job condition with the contents of the requested job, gives an answer to the request from the “chairman” in the form of “the job is unexecutable” or “the job is executable” (with such information as the possible starting time, scheduled completion time, possible number of jobs, and the rate of operation). The result of decision at the job workability decision section  22  of each cell  2  is returned through the inter-cell communication section  18  or directly from other cells  2  acting as “chairman”. 
     Upon returning of the answer from all the job workability decision sections  22 , the job cell determination section  21  of the “chairman” determines the cell  2  to perform the job. As an index for this determination, a cell having the earliest scheduled time of completion is determined among the workable cells  2 . Also, a cell with a minimum number of executable job types (Note: The types of executable jobs are different among cells having different specifications) or the lowest rate of operation may be selected from among the immediately workable cells. 
     (Step S 125 ) The job cell determination section  21  reports a cell  2  for executing a particular job, i.e., a “person in charge” to each cell  2  through the inter-cell communication section  18 . The “person in charge” tries to proceed with the job in compliance with the starting time and the scheduled completion time reported with the job executability. The job cell determination section  21  also reports the starting time and the “person in charge” to the work storage section  1 , and issues a “work output instruction” through the work communication section  17  in such a manner as to deliver the intended work  12  to the “person in charge” by the starting time. 
     (Step S 126 ) In the case where another cell  2  is determined as a cell  2  to conduct the job, i.e., where the “chairman” fails to become a “person in charge”, the process is returned to step S 121  for transmitting the message “work demand” to the work storage section  1  again. When the “chairman” becomes a “person in charge”, on the other hand, the process proceeds to step S 127 . 
     (Step S 127 ) The “chairman” who has become the “person in charge” performs the job by way of the job execution section  23  as soon as the intended work and the job information  11  are transported by the work transport section  3 . Also, the cell  2  that has thus been the “chairman” ceases to be so at this time point. 
     (Step S 128 ) Upon completion of the job by the job execution section  23 , the job result is recorded in the job information  13  in the job execution section  23  and the job extraction section  20  checks to see whether all the jobs for the work are complete by way of the job information  13 . The result of this check, together with the job information  13  and the message “job completion” as well as the work  12 , is returned to the work storage section  1  (which is delivered outside of the system if all the jobs are complete), and, in parallel to this, the job completion message and the like are transmitted through the cell communication section  4 . 
     The cell  2  then executes other jobs upon arrival of the work for the particular jobs if in charge of such other jobs. In the case where the cell  2  is not in charge of other cells at all, on the other hand, the process is returned to step S 121  and the office of “chairman” is assumed to repeat similar processes. 
     In the case where other jobs remain for the work on which a given job has been completed, the work is stored again in the work storage section  1  and waits for the next job. In the case where all the jobs for the work  12  are complete, by contrast, the work is delivered out of the system to end the processes for the work  12 . 
     A flow of the process of outward work delivery to the cell  2  will be explained with reference to FIG.  8 . 
     (Step S 110 ) The cell communication section  4  for communicating with each cell  2  waits for the arrival of the message “work demand” from any of the cells  2 . The message “work demand” is for the cell  2  to demand the receipt of one of the works ready for job performance and is issued at the step S 121  in FIG.  7 . With the arrival of a message, it is interpreted appropriately. When the message is “work demand”, the process  1 S passed to step S 111 . If the message is not “work demand”, by contrast, the message “work demand” continues to be waited for. 
     (Step S 111 ) The cell communication section  4  demands that the work administration section  5  determine a work to perform a job in top priority from among the works ready for job performance (the work itself is stored in the work storage  7  and the related job information in the job information storage  8 ). 
     The work administration section  5  then determines a top-priority work. This determination is made in the work administration table  6  shown in  FIG. 4  in accordance with a predetermined index from among the works in the work condition  211  ready for job performance. 
     When the order of charging is used as an index, top priority is placed on the work of the work number  102 . When the ascending order of lead time is referred to, on the other hand, the work of the work number  105  is selected in top priority. In similar fashion, when the order of priority  214  in some other category is used, the work of the work number  103  is given top priority. 
     Apart from the order of charging, lead time and the order of priority in some other category used as an index for determining the order of job priority above, other items may be cited in the work administration table  6  as an alternative index for determining the order of job priority. Also, an index for determining the order of job priority may be programmed or expressed as a rule. 
     (Step S 112 ) The work administration section  5  takes out a copy of the job information relating to top priority works from the work job information storage  8 , and notifies the “chairman” through the cell communication section  4 . The job information  13  has already been described with reference to FIG.  2 . 
     (Step S 113 ) The cell communication section  4  waits for the arrival of information such as “chairman” and the message “work output instruction” from the cell  2 . With the arrival of such information, the process is passed to step S 114 . 
     (Step S 114 ) The cell communication section  4  registers the reception cell number and the receiving time in the message with the work output table  14  in FIG.  5 . The work transport control section  9  transports a designated work and job information  11  to a designated cell, i.e., the “person in charge” by use of the work transport section  3  at a designated time in accordance with the work output table  14 . Upon completion of the transport, a corresponding record is deleted from the work output table  14 . 
     During the period from receipt of the message “work demand” from a given cell  2  to the determination of a cell  2  as a work destination, the cell communication  4  rejects any message “work demand” from other cells  2  by returning the message “other works in processing” indicative of unacceptability. Only upon completion of a series of processes shown in  FIG. 8 , is the next message “work demand” accepted. 
     Now, the flow of the process of work reception from the cell  2  will be explained with reference to FIG.  9 . 
     (Step S 115 ) The cell communication section  4  waits for the arrival of the message “job completion” from the cell  2 . With the arrival of this message, the process proceeds to step S 116 . 
     [Step S 116 ] The cell communication section  4  interprets the message “job completion” from the cell  2 , which is of two types: one associated with the completion of all jobs required of the work  12 , and the other concerning the case in which a job remains incomplete. The process is passed to step S 117  in the former case and to step S 118  in the latter. 
     (Step S 117 ) The work  12  is output out of the system. 
     (Step S 118 ) The work and the job information  11  are stored again in the work storage  7  of the work storage section  1  and the job information storage  8 , with the process returning to step S 115 . 
     The delivery of the work  12 , etc. out of the system and the storage thereof into the work storage section  1  are effected by use of the work input table  15 . This operation will be briefly explained. 
     The cell communication section  4  interprets the message “job completion”, and adds a record to the work input table  15 . The work transport control section  9 , on the other hand, keeps the work input table  15  monitored, and upon addition of a record, causes the work transport section  3  to transport a work in accordance with the record. Upon completion of the transport, the record is deleted from the work input table  15 . 
     Now, the operation performed for the work  12  will be explained from the viewpoint of the work  12 .  FIG. 10  is a flowchart showing an outline of such operation. 
     (Step S 101 ) The work intended for a job is stored in the work storage  7 . At the same time, the job information  13  relating to the job to be performed on the work  12  is stored in the job information storage  8 . 
     (Step S 102 ) A copy of the job information  13  for the top-priority work is sent to the “chairman” in response to the “work demand” from the cell  2  to assume “chairmanship”. 
     The “chairman” then determines the job required for the work  12  from the copy of the job information  13 . By extracting incomplete jobs from the copy with reference to the job completion column  205   f  or otherwise, a “person in charge” is determined. Information including the “person in charge” is transmitted to the work storage section  1 . 
     (Step S 103 ) The work  12  and the job information  13 , as a work and job information  11 , are transported by the work transport section  3  to the cell  2  executing the job determined and extracted by the cell  2 , i.e., the “person in charge”. 
     (Step S 104 ) The “person in charge” executes the job on the work  12 . Upon completion of the job, the job completion  205   f  of the job information  13  for the particular job is changed to “complete”. 
     (Step S 105 ) The job information  13  is referred to for checking whether the job required for the work  12  is completed or not from the job completion  205   f  of each job. 
     When there remain incomplete jobs, the process proceeds to step S 101  for storing them again in the work storage  7  and the job information storage  8 . When all the jobs are complete, on the other hand, the process is passed to Step S 106 . 
     (Step S 106 ) The work is delivered out of the system. 
     In this way, the process of performing the job in the cell  2  and, upon completion of the job, returning it to the work storage section  1  is repeated for each job. In other words, the work continues to reciprocate between the work storage section  1  and the cell  2  until all jobs are completed. 
     According to the present embodiment, the work storage section  1  may be used to control the order of charging the work  12  into the cell in accordance with a certain rule, and therefore the requirement for performing a job of urgent necessity can be met while at the same time improving the effect of meeting the delivery time. 
     Each job is performed in the cell  2  by checking the workability of the particular job by all the cells. For example, a job is assigned to the cell  2  capable of performing the job at the earliest time, resulting in an improved work efficiency. Also, in view of the fact that the job workability decision section  2  for deciding the workability of a job and the job progress section  19  are provided in each cell  2  and a “person in charge” is determined by the cell  2 , an addition or malfunction of a cell  2  is met easily without any action taken on the work storage section  1 . Further, an arrangement, if necessary, of cells having different functions as in the assembly work can be met. 
     According to the present embodiment, a work and the information relating to a job required for a work are divided into the work storage  7  and the job information storage  8  and collectively controlled by the work administration section  5 . As an alternative, the required job information may be added directly to the work to combine the work storage  7  and the job information storage  8 . 
     Also, the job information  13  may be exchanged through the cell communication section  4  without using the work transport section  3 . 
     Further, a monitor section for detecting a fault of the cell by monitoring the job execution at the cell may be added. In the case where a job is not yet complete even after the lapse of a scheduled job completion time, for example, the cell  2  is judged as being faulty. Such a monitor section may be inserted either in each cell  2  or the work storage section. 
     A second embodiment of the present invention will be described. 
       FIG. 11  is a diagram showing a configuration of a production control system of work driven type according to an embodiment of the present invention. The production control system comprises a pallet  1001  for controlling the transport of a work, etc. in the system, a production equipment  1002  (hereinafter referred merely as “the equipment”) for receiving a job from the pallet  1001  and actually performing the job, a job progress control unit  1003  for controlling the progress of a job on the work, a flexible transport unit  1004  for delivering a given pallet  1001  to one given equipment  1002  in compliance with an instruction from the pallet  1001 , a part supply unit  1005  for supplying a work to the pallet  1001 , an automatic warehouse  1006  for housing a work placed on the pallet  1001  from which a given work is deliverable at a given time, and a design information write unit  1007  for writing the contents of a job for the work in the pallet  1001 . 
     The pallet  1001  is configured of a communication unit  1008  for exchanging information with the pallet  1001 , a plurality of equipment  1002  and the job progress control unit  1003 , a work priority determination unit  1009  for recalculating the order of priority of a work held at the end of a job, an equipment selection unit  1010  for determining the equipment which performs the next job of a work held thereby in negotiation with the equipment, a design information storage unit  1011  for storing the design information of a work, and a work information storage unit for storing the job history and the work condition. The communication unit  1008  affects communications by way of a communication medium (such as radio communications) capable of broadcast communication. The communication unit  1008 , on the other hand, is comprised of a work communication section  1013 , an equipment communication section  1014  and an inter-pallet communication section  1015  depending on the other party of the information exchange. 
     The equipment  1002  includes a communication unit  1016  for exchanging information with the pallet  1001  and the job progress control unit  1003 , an equipment information storage unit  1017  having a relative performance for accuracy, speed, etc., a job workability decision unit  1028  for determining whether a job is executable or not on the equipment, an equipment control data generation unit  1018  for preparing an NC data from the work design information, a job execution unit  1020  for executing a job by applying the NC data obtained from the equipment control data generation unit  1018  to the actual equipment  1019 , and actual equipment  1019  for executing the actual job and acting on a work. 
     The job progress control unit  1003  includes a communication unit  1023  for communicating with the pallet  1001 , a job request right effectuation unit  1024  for granting a job request right to the pallet  1001  and a work priority storage unit  1025  for storing the order of priority of all the works. 
     According to the present embodiment, it is suggested that the flexible transport unit  1004  uses an automatic transporter and a stripe of lines. To the extent that a given pallet  1001  is capable of being carried to a given equipment  1002 , however, any type of transporter may be used with equal effect. A doubleloop construction with the capability to outrun other pallets  1001  is an example. Also, a pallet  1001  equipped with a drive unit is expected to have the same effect as an automatic transporter. 
     The design information write unit  1007  includes a job time calculation unit  1026  for calculating and predicting the maximum time of a job on a work and a design information write unit  1027  for writing the design information and the above-mentioned predicted job performance time in the pallet  1001 . 
     The system according to the present invention is configured of the parts described above. 
     Take the machining work as an example.  FIG. 12  shows a configuration for machining work according to an embodiment of the present invention. This machining system includes machining contents  1204   a  to  1204   c  for performing actual machining work, NC lathes  1205   a  to  1205   c , works  1203   a  to  1203   f  providing workpieces, pallets  1201   a  to  1201   f  for controlling the transport of the work  1203  placed thereon, automatic transporters  1202   a  to  1202   f  for carrying the work  1203  to given equipment in compliance with an instruction from the pallet  1201 , an automatic warehouse  1206  from which a given work  103  is deliverable at a given time in accordance with an instruction from the pallet  1201 , a parts supply unit  1207  for placing a work  1203  on the pallet  1201 , a design information write unit  1208  for writing the design information for the work  1203  into the pallet  1201 , and a job progress control unit  1209  for controlling the progress of the job on the work  1203 . 
       FIG. 13  shows an example of design information stored in the design information storage unit  1011 . This information is a description of the contents of individual jobs and the order of a plurality of jobs performed on a work. The work number  1301  is an identifier for discriminating individual works in the present system and is specific to each work. The job completion flag  1302  is for indicating whether all the jobs on a work are complete or not. The work shape  1303  is information representing the shape of a work before job performance. For example, the work is a round steel bar 1000 mm long and 100 mm in radius as shown in (A) of the side view of  FIG. 3  (only the upper portion from the center shown). The number of jobs  1304  indicates the number of all the jobs performed on a work. The predicted maximum job time  1305  is information used for determining the order of priority of a work, and the time required for using the equipment slowest in the speed of operation is calculated in advance by the job time calculation unit  1026  and stored. The delivery time  1306  is the lead time of the work. 
     The initial information on a work is mentioned above and is followed by the numerical job information on the number of jobs  1304 . The job number  1307  provides an identifier for discriminating the jobs on a work. This identifier is unique to a job, but is not necessarily indicative of the order of job performance. The job completion flag  1306  is indicative of whether a particular job is completed or not. The preceding job number  1309  represents a job required to have been completed before a particular job, and is used for indicating the order of performance of all the jobs. The accuracy  1310  indicates the demanded accuracy of a job, by use of which the job execution equipment can be reduced. The machining shape  1311  indicates a shape of a work after job performance. In this example, as seen from the preceding job  1309 , the job 1 performs the rough machining as shown in  FIG. 3B , followed by the job 2 for finish machining as shown in FIG.  3 C. 
     An example of the work information stored in the work information storage unit  1021  is shown in FIG.  14 . This is information representing the work condition at the time of completion up to a given job. The work number  1401  is the same as the work number  1301  and is unique to the work in the present system. The work shape  1402  represents the shape of a work at the above-mentioned time point, and the shape after completion of the job in this example. The residual number of jobs  1403  is the number of jobs remaining at the above-mentioned time point. The predicted maximum residual job time  1404  is a predicted maximum job time required to perform the remaining jobs at the above-mentioned time point. This is obtained by subtracting the actual job time from the predicted maximum job time. The work information is configured of information described above. In the example under consideration, the condition after completion of the job 1 is indicated. 
       FIG. 15  shows an example of the information stored in the order of work priority storage unit  1009 . The work number  1501  corresponds to the work number  1301  and the work number  1401 . The order of priority  1502  represents the order of priority of each work as of a certain time point. The job-in-process flag  1503  indicates whether the work is being processed or not. 
       FIG. 16  shows an example of information stored in the equipment information storage unit  1017 . The position  1601  is that of the equipment. This position represents an absolute one in the present system, by reference to which the automatic transporter carries the pallet  1201 . The job type  1602  is the type of job specialized in by the equipment under consideration. The present example represents the NC lathe  1205   a , which specializes in the axial machining. The accuracy  1205   a  indicates the accuracy of the equipment. In this example, the finish accuracy, i.e., the surface roughness is used as a unit. In addition, the minimum feed rate of the cutting tool may be considered the accuracy of the equipment involved. The speed  1604  indicates a relative speed resulting from comparison of the speed with that of the other equipment. The maximum size  1605  and the minimum size  1606  are indicative of the size limit of a work on which the equipment can operate. The procedure for the system to perform the jobs will be described below with reference to  FIGS. 17  to  19  on the basis of the above-mentioned information. 
     According to this embodiment, the pallet  1201 , the machining center  1204 , the NC lathe  1205  and the job progress control unit  1209  proceeds with a job as a whole system under individual decisions while exchanging information therebetween. Therefore, the flow of operation is divided into three categories. 
       FIG. 17  is a diagram showing the flow of operation of the pallet  1201 . Step S 1101 : The pallet  1201  receives the work  1203  at the parts supply unit  1207  and then is leaded in the automatic warehouse  1206 . The work priority determination unit  1009  calculates a priority by using the predicted maximum job time  1305  and the delivery time  1306  of  FIG. 13  stored in the design information storage unit  1011 . 
     Step S 1102 : The new work charging message is sent to the job progress control unit  1209  by way of the work communication section  1013 . Upon receipt of this message, the job progress control unit  1209  grants the job request right to an appropriate pallet such as the pallet  1201   a , as will be explained later more in detail with reference to the job progress control unit  1209  in FIG.  18 . 
     Step S 1103 : This step awaits the arrival of the job request right from the job progress control unit  1209 . 
     Step S 1104 : The accuracy  1310  and the machining shape  1311  of the next job to be conducted are broadcast to all the machining centers  1204  and the NC lathes  1204 . Upon receipt of this message, each machining center  1204  and the NC lathe  1205  decides on the workability of the job and gives an answer to the pallet  1201   a , as will be explained more in detail later with reference to FIG.  19 . 
     Step S 1105 : The answers from the machining center  1204  and the NC lathe  1205  are collected. There may be a plurality of answers, and therefore the dead line is set for collecting the answers, so that the answers collected within the deadline are studied at the same time. 
     Step S 1106 : This step is for checking to see whether answers are received from the machining center  1204  and the NC lathe  1205 . In the absence of an answer, it is decided that the machining center  1204  or the NC lathe  1205  capable of executing the next job on the work  1201   a  is absent at this time point, and a job request end notice is sent to the job progress control unit  1209 . 
     Step S 1107 : Watching the speed  1604  in the answer from the machining center  1204  and the NC lathe  1205  collected at step S 1105 , the equipment which conducts the job at the fastest rate such as the NC lathe  1205  is selected, and a job request is sent thereto. An unemployment notice is sent to the machining centers  1204  and the NC lathes  1205  not selected. A job request end notice is sent to the job progress control unit  1209  in order to notify that the job request is ended. The job progress control unit  1209  that has received the notice sets the job-in-process flag  1503  in “job-in-process”, as will be explained more in detail later with reference to FIG.  18 . The NC lathe  1205   a  that has received a job request, on the other hand, notifies its own position as an answer to the pallet  1201   a  from which a job request was received, as will be explained later more in detail with reference to the machining center  1204  and the NC lathe  1205   a  in FIG.  19 . 
     Step S 1108 : With the position determined of the NC lathe  1205   a  to which a job was requested, this step instructs the automatic transporter  1202   a  with the pallet  1201   a  placed thereon to carry the pallet to the NC lathe  1205   a.    
     Step S 1109 : This step waits for a job end notice from the NC lathe  1205   a.    
     Step S 1110 : The work shape  1402 , the number of remaining jobs  1403  and the predicted maximum residual job time  1404  in the work information storage unit  1012  shown in  FIG. 14  are updated. When the work shown in  FIG. 13  is newly charged, the job 1 is performed first of all. Once the job is executed correctly, the work shape  1402  assumes a machining shape  1311  of the job 1 as shown in  FIG. 3B , with the result that the number of remaining jobs  1403  is decreased and the time actually taken for the job is subtracted from the predicted maximum residual job time  1404  and stored. The order of priority of the work is calculated again from the predicted maximum residual job time  1404  and the delivery time  1306  of the work after being updated. 
     Step S 1111 : The job completion flags  1308  of the work is checked, and if all of the flags  1308  are in “job completion” state, the process is passed to step S 1113 . 
     Step S 1112 : The job completion message is sent to the job progress control unit  1209 . 
     Step S 1113 : The job completion flag  1302  is set in “job completion” state, and the automatic transporter  1202   a  is instructed for delivery out of the system. 
     The procedure from steps S 1101  to S 1113  is repeated. 
     Now, the flow of operation of the job request right effectuation unit  1024  shown in  FIG. 18  will be explained. 
     Step S 1201 : This step waits for a message from the pallet  1201 . The message sent out at step S 1102  or S 1113  for the operation of the pallet  1201  described above is also waited for. 
     Step S 1202 : It is decided whether the message received is from the newly-charged pallet  1201  to thereby change the flow of operation. 
     Step S 1203 : A region for a new work is secured in the work priority storage unit  1025 , and information is written into the work number  1501  and the order of priority  1502  from the message received, thereby setting the job-in-process flag  1503  in ready state. 
     Step S 1204 : The order of priority  1502  of the work number  1501  corresponding to the work number in the message is rewritten into the order of priority in the message thereby to set the job-in-process flag  1503  in ready state. 
     Step S 1205 : The information in the work priority storage unit  1025  is rearranged in the descending order of priority  1502 .  FIG. 15  shows an example after completion of this step. 
     Step S 1206 : The job request right is granted to the pallets  1201  in the descending order of priority from the information of the work priority storage unit  1025 . 
     Step S 1207 : This steps checks to see whether all the works in the ready state in the work priority storage unit  1025  are granted the job request right or not, and if there is any work not granted the job request right, the checking is continued until no such work exists. 
     The procedure from steps S 1201  to S 1207  is repeated. 
     Finally, the flow of operation of the equipment  1002  will be explained with reference to the NC lathe  1205   a  shown in  FIG. 19  as an example. Although this example refers to the flow of operation of the machining center  1204  and the NC lathe  1205 , a similar flow may be studied also for other equipment as far as it has the function of the equipment  1002 . 
     Step S 1301 : This step waits for the job broadcast from the pallet  1201  at step S 1104 , i.e., the accuracy  1310  and the machining shape  1311 . 
     Step S 1302 : The job workability decision unit  1028  checks the information received at step  1301  with the accuracy  1603 , the maximum size  1605  and minimum size  1606  stored in the equipment information storage unit  1010  to decide the workability of job. If the job is possible to execute, the speed  1604  of the NC lathe  1205   a  is given as an answer to the pallet  1201  which has issued the job at step S 1104 . If the job is impossible to execute, on the other hand, the process is returned to step S 1301 . 
     Step S 1303 : This step waits for the arrival of a job request from step S 1107 . 
     Step S 1304 : If the contents of the request received at step S 1303  is an unemployment notice, the process is returned to step S 1301 . If the job is requested, on the other hand, the following procedure is taken. 
     Step S 1305 : The position  1601  of the NC lathe  1205   a  is given as an answer to the pallet  1201  that has issued a job request. 
     Step S 1306 : A job request end notice is sent to the job progress control unit  1209 . 
     Step S 1307 : This step waits for the arrival of a work. If no work arrives after the lapse of a predetermined length of time, the process is returned to step S 1301 . 
     Step S 1308 : operation is for controlling the machining operation is generated from the machining shape  1311  by the job execution unit  1020  by use of the equipment control data generation unit  1018 . 
     Step S 1309 : The job execution unit  1020  controls the NC lathe  1205   a  and continues the job on the basis of the NC data generated at step S 1308 . 
     Step S 1310 : On the basis of the job result, a new work shape and the time required for the job are transmitted to the pallet  1201 . 
     Step S 1311 : A job end notice is sent to the pallet  1201 . 
     The procedure from steps S 1301  to S 1311  is repeated. 
     If the functions of the job request right effectuation unit  1024  and the work priority storage unit  1025  are added to the pallet  1201  without using the job progress control unit  1209 , the same effect as the above-mentioned embodiments is obtained, although the load on the pallet  1201  is increased. An example is described below. 
     The configuration of this example is substantially the same as that shown in FIG.  12 . The difference lies in that the job request right effectuation unit  1024  and the work priority storage unit  1025  are mounted on the pallet  1201 . 
       FIG. 20  shows the flow of operation with the job request right effectuation unit  1024  mounted on the pallet  1201 . 
     Step S 1401 : The job request right effectuation unit  1024  waits for the charging of new work or the completion of a job. In this example, the job request right effectuation unit  1024  on the pallet  1201  is not energized until this condition is met. 
     Step S 1402 : The job request right effectuation unit  1024  broadcasts a priority return demand to all the pallets  1201  and collects the order of priority of all the works. The order of priority thus collected is stored in the work priority storage unit  1025 . 
     Step S 1403 : The information in the work priority storage unit  1025  are rearranged in the descending order of priority. 
     Step S 1404 : The job request right is granted to the works from the work priority storage unit  1025  in the descending order of priority. 
     Step S 1405 : This step waits for the arrival of a job request end notice from the pallet  1201 . 
     Step S 1406 : This step checks to see whether all the works waiting in the work priority storage unit  1025  are granted the job request right, and if there is any work not granted the job request right, the checking is continued until there all the works are granted the job request right. 
     The procedure from steps S 1401  to S 1406  is repeated. The machining center  1204  and the NC lathe  1205  that have been granted the job request right may operate the same way as in the above-mentioned embodiments. In this way, even when the job request right effectuation unit  1024  is mounted on the pallet  1201 , the same effect as in the above-mentioned embodiments is obtained. 
     Now, an embodiment of the present invention as applied to the assembly work will be explained with reference to the case in which parts are mounted on a printed wiring board. A configuration of such an embodiment is shown in FIG.  21 . This assembly system includes pallets  2101   a  to  2101   d  with all the parts placed thereon, parts supply unit  2104  for supplying all the parts to the pallet  2101 , an automatic warehouse  2103  capable of delivering a given pallet  2101  at a given time, parts mounting unit  2102   a  to  2102   d , and a flexible transport line  2105  for transporting a given pallet to a given part mounting unit  2102 . In this embodiment, the parts supply unit  2104  includes a parts supply unit for supplying parts to the pallet  2101  and a design information write unit for writing assembly information in the pallet  2101 . 
       FIG. 22  shows an example of assembly information stored in the design information storage unit  1011 . This includes the description of the parts assembled on a printed wiring board and the positions of assembly thereof. The work number  2201  is an identifier for discriminating the individual printed wiring boards in this system and is unique to the printed wiring board. The job completion flag  2202  is for indicating whether all the jobs on a printed wiring board are complete or not. The work size  2203  is indicative of the size of a printed wiring board. The number of jobs  2204  represents the number of assembly jobs conducted on a printed wiring board. The predicted maximum job time  2205  is information used for determining the order of priority of a work. This information is calculated and written by the job time calculation unit  1026  in advance in terms of the time taken when only the slowest equipment is used. The delivery time  2206  indicates the delivery time of the printed wiring board. 
     The initial information on the printed wiring board are described above, and are followed by the assembly information which is as many as the number of jobs  2204 . The number of jobs  2207  provides information for discriminating the assembly work on the printed wiring board. Although unique to a job, this identifier does not necessarily represent the order of job execution. The job completion flag  2208  indicates whether a particular job is complete or not. The preceding job number  2209  indicates the job required to have been executed before the present job, and is used for indicating the order of execution of all jobs. The part type  2210  indicates the parts assembled on the printed wiring board. The parts assembly unit  2102  obtains information on the grip and the shape of parts from a parts database on the basis of the information on the part type  2210 . The part position  2211  indicates the position of an unassembled part placed on the pallet  2101 . The assembly position  2212  is the position of assembly on the printed wiring board. A control data for the parts supply unit  2104  is prepared on the basis of the part position  2211  and the assembly position  2212 . 
     An example of the work information stored in the work information storage unit  1012  is shown in FIG.  23 . This is the information representing the work condition at the time point of completion of a job. The work number  2301  is the same as the work number  2201  and is unique to the printed wiring board in this system. The number of remaining jobs  2302  indicates the number of jobs remaining at the above-mentioned time point. The predicted maximum residual job time  2303  is the maximum time predicted for the jobs remaining incomplete at the above-mentioned time point. This is obtained by subtracting the actual job time from the predicted maximum job time. The work information is comprised of these information, and indicates the condition after completion of the job  50  in the example under consideration. 
     The contents of the work priority storage unit  1025  used in this example are similar to those for the embodiment shown in FIG.  15 . 
       FIG. 24  is a diagram showing an example of information stored in the equipment information storage unit  1017 . The position  2401  indicates the position of the particular equipment. This position represents an absolute position in this system, depending on which the pallet  2101  is transported by the flexible transport line  2105 . The job type  2402  is the type of job specialized in by the equipment. In this example, a mounter is used specializing in the surface mounting. The accuracy  2404  is the speed of the equipment as relative to that of other equipment. The procedure for performing the jobs in this system on the basis of the above-mentioned information will be described with reference to  FIGS. 18 ,  25  and  26 . 
     According to the present embodiment, as in the above-mentioned machining system, the operation of the system as a whole is performed on the basis of individual judgements while information is exchanged between the pallet  2101 , the parts assembly unit  2102  and the job progress control unit  1003 . The job progress control unit  1003  which operates in a way similar to the one in the aforementioned embodiments will not be explained again. 
     According to the present embodiment, the flow of operation will be described in three parts in view of the fact that the whole system is operated according to the individual judgements while information is exchanged between the pallet  2101 , the parts assembly unit  2102  and the job progress control unit  1003 . 
       FIG. 25  is a diagram showing the flow of operation of the pallet  2101 . 
     Step S 1501 : The pallet  2101  receives the work  1203  at the parts supply unit  1207 , which parts are stored in the automatic warehouse  2103 . The work priority determination unit  1009  calculates the order of priority by use of the predicted maximum job time  2205  and the delivery time  2206  in the design information storage unit  1011 . 
     Step S 1502 : A new work charge message is sent to the job progress control unit  1003  by way of the work communication section  1013 . Upon receipt of this message, the job progress control unit  1003  grants the job request right to an appropriate pallet  2101 , as will be described more in detail later with reference to the job progress control unit  1003  shown in FIG.  18 . 
     Step S 1503 : This step waits for the arrival of the job request right from the job progress control unit  1003 . 
     Step S 1504 : First, a chain of job types  2402  to be conducted in the next process is formed and is broadcast to all the parts assembly unit  2102 . Upon receipt of this message, the parts assembly unit  2102  decides on the workability of a job and gives an answer to the pallet  2101 , as will be described in more detail later with reference to the parts assembly unit  2102  shown in FIG.  19 . 
     Step S 1505 : Wait for answers from the parts assembly unit  2102 . In order to collect answers from a plurality of the parts assembly units  2102 , a time limit is provided so that answers collected within the time limit are regarded as effective ones. 
     Step S 1506 : This step checks to see whether any answer is given from the parts assembly unit  2102 . In the absence of an answer, a job request end notice is sent to the job progress control unit  1003  judging that there is not any parts assembly unit  2102  capable of executing the next job on the printed wiring board. 
     Step S 1507 : In consideration of the position  2401  and the speed  2404  in the answers from the parts assembly unit  2102  collected at step S 1505 , the parts assembly unit  210 ? capable of executing the transport and the job in the fastest way is selected, and a job request is sent thereto. On the other hand, a job request end notice is sent to the job progress control unit  1003  in order to notify that a job request has ended. Upon receipt of this notice, the job progress control unit  1003  sets the job-in-process flag  1503  in “job-in-process” state, as will be described more in detail later with reference to the job progress control unit  1003  shown in FIG.  18 . The parts assembly unit that has received a job request, on the other hand, notifies the position of the parts assembly unit  2102  to the pallet  2101  from which the job request has come, as will be described more in detail later with reference to the parts assembly unit  2102  shown in FIG.  19 . 
     Step S 1508 : The position of the parts assembly unit is determined from the answers of the parts assembly unit  2102 , and the flexible transport line  2105  is instructed to transport the pallet  2101  to the particular parts assembly unit. 
     Step S 1509 : This step waits for a job end notice from the parts assembly unit. 
     Step S 1510 : The number of remaining jobs  2302  and the predicted maximum residual time  2303  in the work information storage unit  1021  shown in  FIG. 23  are updated. In the case under consideration, fifty parts are completely assembled on the printed wiring board  101  (work number  101 ), indicating that 1.5 hours has passed. 
     Step S 1511 : This step checks the job completion flag  2208 , and if this flag is in “job completion” state, the process is passed to step S 1513 . 
     Step S 1512 : The job completion message is sent to the job progress control unit  1003 . 
     Step S 1513 : The job completion flag  2202  is set in “job completion” state, and the flexible transport line  2105  is instructed for delivery out of the system. 
     The procedure from steps S 1501  to S 1513  is repeated. 
     The flow of operation of the job request right effectuation unit  1024  which is not much different from that of the machining system mentioned above will not be explained any more. 
     Finally, description will be made of the flow of operation of the parts assembly unit  1202  shown in FIG.  26 . 
     Step S 1601  This step waits for a job broadcast from the pallet  2101  at step S 1504 , i.e., the job type  2402 . 
     Step S 1602 : The job workability decision unit  1028  checks the information received at step S 1601  with the accuracy  2403  stored in the equipment information storage unit  1010  to thereby decide the workability of the job. If the job is executable, the position  2401  and the speed  2404  of the parts assembly unit  2102  are given as an answer to the pallet  2101  that has transmitted the job at step S 1504 . If the job is not executable, by contrast, the process returns to step S 1601 . 
     Step S 1603 : This step waits for a job request from step S 1507 . 
     Step S 1604  When an unemployment notice is received from step S 1603 , the process is returned to step S 1601 . If the notice is a job request, the following procedure is taken. 
     Step S 1605 : A job request end notice is sent to the job progress control unit  1003 . 
     Step S 1606  This step waits for the arrival of the pallet  2101 . When the pallet  2101  fails to arrive after the lapse of a predetermined time, the process is returned to step S 1601 . 
     Step S 1607 : An NC data for controlling the assembly of parts of a series of types is generated by the job execution unit  1020  from the equipment control data generation unit  1018  from the assembly information shown in FIG.  22 . 
     Step S 1608 : The job execution unit  1020  executes a job by controlling the parts assembly unit  2102  from the data obtained at step S 1607 . 
     Step S 1609 : The number of jobs actually performed and the time required for the jobs are transmitted to the pallet  2101  from the job result. 
     Step S 1610 : A job end notice is sent to the pallet  2101 . 
     The procedure from steps S 1601  to S 1610  is repeated. 
     The foregoing is an explanation of embodiments of machining and assembly work according to the present invention. In a production control system of autonomous and decentralized type of the present invention, the job request right effectuation unit  1024  controls the order of job requests thereby to make possible the progress of jobs taking the delivery time into account. 
     According to the production control system of autonomous and decentralized type of the present invention, the job progress is controlled in accordance with the product delivery time while maintaining the system flexibility at the same time. 
     Many different embodiments of the present invention may be constructed without departing from the spirit and scope of the invention. It should be understood that the present invention is not limited to the specific embodiments described in this specification. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims.