Patent Publication Number: US-2023141642-A1

Title: Work assignment device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a work assignment device. 
     BACKGROUND ART 
     In many cases, a large-scale plant such as a plant belonging to an electric power field or the like is monitored and controlled by a supervisory control device. 
     In recent years, in the supervisory control device, a software-type digital supervisory control panel has been introduced, instead of a conventional hardware-type analog supervisory control panel. The software-type digital supervisory control panel is also referred to as a digital panel. 
     In a case where the digital panel is introduced into the supervisory control device, a work is performed by using a graphical operator interface (GUI) which integrates functions of the supervisory control panel. By introducing the digital panel into the supervisory control device, the size of the supervisory control device can be reduced, and an operation load to be imposed on an operator (operating person) in operating the supervisory control panel can be thereby reduced. 
     In operating the plant, a work procedure to be performed when an event occurs and a work assignment designating an operator in charge who (which) performs a work which is a constituent of the work procedure are determined in advance. In some cases, the operator in charge is an operating person, and in other cases, the operator in charge is an automated system. In recent years, however, due to higher functionality of a supervisory control system and reduction in the number of operators which is accordingly caused, assumed is management in which in a normal operation, a minimum number of operators monitors a plurality of plants at the same time, and in occurrence of an event, the number of operators and a work system should be changed. 
     Further, when an operator hands over a work to another operator or the automated system hands over a work to an operator, the operator who takes over the work should correctly recognize an implementation status of the work so far and a work assignment from then. For this reason, it is important that the work assignment of the operator should be presented in consideration of conditions of the operator such as a workload imposed on the operator, condition recognition by the operator, and the like. 
     In the technique disclosed in Patent Document 1, when detection notification of abnormality is received, an operator who is to deal with this abnormality is determined. Further, a new assignment of works is made for an operator who was engaged in an impossible work which became impossible to proceed, due to occurrence of the abnormality. 
     In the technique disclosed in Patent Document 2, fatigue of a user is detected by using biometric information of the user and information on the work of the user. Further, support measures required to reduce the fatigue is selected in accordance with the detected fatigue state of the user. The support measures are user interface controls including enlarged display and/or enhancement of a contrast in a screen of a display device, an increase in the volume of voice and sound, an increase in the input sensitivity of an input device such as a mouse, a pen tablet, or the like, and so on. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         [Patent Document 1] WO 2017/163629 
         [Patent Document 2] Japanese Patent Application Laid Open Gazette No. 2001-184139 
       
    
     SUMMARY 
     Problem to be Solved by the Invention 
     As described above, in the case where the work assignment designating the work procedure and the operator in charge is determined in advance and an operator is assigned to a work in accordance with the work assignment determined in advance, a rule for assigning the work has to be prepared in advance. Further, when an unexpected combination of events occur, there are some cases where it is impossible to deal with the occurring events at the right time by using the work assignment determined in advance and this causes a severe accident. For this reason, it is required to dynamically perform the work assignment. 
     The present disclosure is intended to solve this problem. It is an object of the present disclosure to provide a work assignment device capable of dynamically performing an assignment of an operator in accordance with a plant condition. 
     Means to Solve the Problem 
     The present disclosure is intended for a work assignment device. 
     The work assignment device includes a work procedure derivation unit, a scheduling unit, a work assignment evaluation unit, and a work assignment determination unit. 
     The work procedure derivation unit derives a work procedure on the basis of plant information on a plant. 
     The scheduling unit selects a plurality of work assignment candidates each indicating an assignment of an operator to a procedure which is a constituent of the work procedure. 
     The work assignment evaluation unit performs evaluation on each of the plurality of work assignment candidates. 
     The work assignment determination unit determines a work assignment from the plurality of work assignment candidates on the basis of a result of the evaluation. 
     Effects of the Invention 
     According to the present disclosure, a work procedure is derived on the basis of plant information on a plant, and an assignment of an operator to a procedure which is a constituent of the derived work procedure is determined. It is thereby possible to dynamically perform an assignment of an operator in accordance with a plant condition. 
     These and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram schematically showing a hardware configuration of a supervisory control system on which a work assignment device in accordance with a first preferred embodiment is mounted; 
         FIG.  2    is a block diagram schematically showing a functional configuration of the work assignment device in accordance with the first preferred embodiment; 
         FIG.  3    is a view showing an example of event information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  4    is a view showing an example of work procedure information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  5    is a view showing another example of work procedure information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  6    is a view showing an example of operator information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  7    is a view showing an example of evaluation information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  8    is a view showing an example of presentation information stored in the work assignment device in accordance with the first preferred embodiment; 
         FIG.  9    is a flowchart showing a processing performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  10    is a view showing an exemplary selection of a plurality of work assignment candidates, which is performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  11    is a view showing a result of the selection of the plurality of work assignment candidates, which is performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  12    is a view showing an exemplary judgment of a degree of fatigue of an operator on the basis of a required operation time, which is performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  13    is a flowchart showing an exemplary process for evaluation, which is performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  14    is a view showing exemplary evaluation performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  15    is a flowchart showing an exemplary process of determining a presentation method, which is performed by the work assignment device in accordance with the first preferred embodiment; 
         FIG.  16    is a view showing exemplary determination of the presentation method, which is performed by the work assignment device in accordance with the first preferred embodiment; and 
         FIG.  17    is a view showing a work content that should be performed next by the operator, which is displayed on an operation screen of a plant operated by the operator, by the work assignment device in accordance with the first preferred embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT(S) 
     1 the First Preferred Embodiment 
       FIG.  1    is a block diagram schematically showing a hardware configuration of a supervisory control system on which a work assignment device in accordance with a first preferred embodiment is mounted. 
     The supervisory control system  1  shown in  FIG.  1    monitors and controls a plant. The supervisory control system  1  is formed of a computer. 
     As shown in  FIG.  1   , the supervisory control system  1  includes a processor  11 , a memory  12 , a hard disk drive  13 , an input device  14 , an output device  15 , and a system bus  16 . 
     The processor  11  is a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), or the like. The memory  12  is a random access memory (RAM), a read Only memory (ROM), or the like. The hard disk drive  13  may be replaced with an auxiliary storage other than the hard disk drive  13 . For example, the hard disk drive  13  may be replaced with a solid state drive (SSD), a RAM disk, or the like. The input device  14  is a keyboard, a pointing device, a microphone, a scanner, a camera, a communication interface, a sensor, or the like. The output device  15  is a display, a lamp, a speaker, a communication interface, or the like. 
     The system bus  16  communicably connects the processor  11 , the memory  12 , the hard disk drive  13 , the input device  14 , and the output device  15  to one another. 
     2 Work Assignment Device 
       FIG.  2    is a block diagram schematically showing a functional configuration of the work assignment device in accordance with the first preferred embodiment. 
     As shown in  FIG.  2   , the work assignment device  2  of the first preferred embodiment includes a plant information storage unit  21 , an event information storage unit  22 , a work procedure information storage unit  23 , an operation information storage unit  24 , an operator information storage unit  25 , a biometric information storage unit  26 , an evaluation information storage unit  27 , and a presentation information storage unit  28 . These constituent elements are each formed of at least one of the memory  12  and the hard disk drive  13 . 
     Further, as shown in  FIG.  2   , the work assignment device  2  includes a plant condition diagnostic unit  31 , a work procedure determination unit  32 , a scheduling unit  33 , an operator condition judgment unit  34 , a work assignment evaluation unit  35 , a work assignment determination unit  36 , a work assignment presentation method determination unit  37 , and a work assignment presentation unit  38 . Respective functions of these constituent elements are each implemented by executing a program stored in at least one of the memory  12  and the hard disk drive  13 . There may be a configuration where the supervisory control system  1  includes a plurality of processors  11 , a plurality of memories  12 , and a plurality of hard disk drives  13  and the plurality of processors  11 , the plurality of memories  12 , and the plurality of hard disk drives  13  cooperate to implement the respective functions of these constituent elements. 
     3 Information to be Stored 
     3.1 Plant Information 
     The plant information storage unit  21  stores therein plant information  51 . The plant information  51  to be stored there is information on a plant. The plant information  51  is time series information. The plant information  51  is acquired by a plant equipment which is a constituent of the plant. The plant information  51  includes at least one kind of information selected from a group consisting of alarm information on an alarm to be set off by the plant equipment and a plant value outputted from the plant equipment. Hereinafter, it is assumed that the plant information  51  includes both the alarm information and the plant value. The plant information  51  may include any information other than the alarm information or the plant value. The plant information  51  may include, for example, information on an operation state of the plant other than the alarm information, instead of the alarm information or in addition to the alarm information. The plant equipment is an equipment in accordance with the kind of plant, such as a motor, a pump, a valve, or the like. 
     3.2 Event Information 
     The event information storage unit  22  stores therein event information  52 . The event information  52  to be stored there is information on an event that occurs in the plant. 
     The event information  52  indicates a work procedure to be performed when each event occurs and a degree of influence of the event. The event information  52  may indicate information other than these kinds of information. For example, the event information  52  may indicate work priority or the like of the work procedure to be performed when each event occurs. 
       FIG.  3    is a view showing an example of the event information stored in the work assignment device in accordance with the first preferred embodiment. 
     The event information  52  shown in  FIG.  3    includes an event ID  521 , and a work procedure ID  522  and a degree of influence  523  which are corresponding to the event ID  521 . The event ID  521  specifies an event. The work procedure ID  522  corresponding to the event ID  521  specifies a work procedure to be performed when the event specified by the event ID  521  occurs. The degree of influence  523  corresponding to the event ID  521  specifies a degree of influence of the event specified by the event ID  521 . The event information  52  shown in  FIG.  3    thereby indicates the work procedure to be performed when each event occurs and the degree of influence of the event. The degree of influence  523  is represented as “big”, “medium”, or “small”. To the degree of influence  523  of “big”, “medium”, or “small”, given is a coefficient of “3”, “2”, or “1”, respectively, by which an error rate described later is multiplied. 
     Hereinafter, for simple description, events specified by the event IDs  521  of “event 1”, “event 2”, and “event 3” will be abbreviated as “event 1”, “event 2”, and “event 3”, respectively. Further, work procedures specified by the work procedure IDs  522  of “procedure 1”, “procedure 2”, and “procedure 3” will be abbreviated as “procedure 1”, “procedure 2”, and “procedure 3”, respectively. 
     3.3 Work Procedure Information 
     The work procedure information storage unit  23  stores therein work procedure information  53  and work procedure information  54 . The work procedure information  53  and the work procedure information  54  to be stored there are each information on each procedure. 
     The work procedure information  53  indicates a procedure which is a constituent of each work procedure. The work procedure information  53  indicates whether or not each of a human and a system can perform each procedure and whether or not each procedure needs a performance qualification. Further, the work procedure information  53  indicates a standard error rate of an error occurring when each procedure is performed and an allowed time which is time allowed to spend until each procedure is performed. The work procedure information  53  may indicate information other than these kinds of information. For example, the work procedure information  53  may indicate a standard work time which is standardly spent when each procedure is performed, a workload to be imposed on an operator performing each procedure when the procedure is performed, a cost incurred when each procedure is performed, or the like. 
     The work procedure information  54  indicates a work which is a constituent of each procedure. Further, the work procedure information  54  indicates a workload to be imposed on an operator performing each work when the work is performed and an error rate of an error occurring when each work is performed. 
       FIGS.  4  and  5    are views showing examples of the work procedure information stored in the work assignment device in accordance with the first preferred embodiment. 
     The work procedure information  53  shown in  FIG.  4    includes a procedure ID  531 , and a name  532 , a next procedure ID  533 , an operator in charge  534 , the necessity of performance qualification  535 , a standard error rate  536 , and an allowed time  537  which are corresponding to the procedure ID  531 . The procedure ID  531  specifies a procedure. The name  532  corresponding to the procedure ID  531  specifies a name of the procedure specified by the procedure ID  531 . The next procedure ID  533  corresponding to the procedure ID  531  specifies a next procedure to be performed next to the procedure specified by the procedure ID  531 . The operator in charge  534  corresponding to the procedure ID  531  specifies an operator in charge who (which) can perform the procedure specified by the procedure ID  531 . The operator in charge is at least one of a human and a system. The necessity of performance qualification corresponding to the procedure ID  531  specifies whether or not the procedure specified by the procedure ID  531  needs a performance qualification. The necessity of performance qualification  535  corresponding to procedure ID  531  is set when the operator in charge  534  corresponding to the procedure ID  531  is a human. The standard error rate  536  corresponding to the procedure ID  531  specifies a standard error rate of an error occurring when the procedure specified by the procedure ID  531  is performed. The standard error rate  536  corresponding to the procedure ID  531  is set for each of the cases where the operator in charge  534  corresponding to the procedure ID  531  is a human and where the operator in charge  534  corresponding to the procedure ID  531  is a system. The allowed time  537  corresponding to the procedure ID  531  specifies an allowed time which is time allowed to spend until the procedure specified by the procedure ID  531  is performed. The allowed time  537  corresponding to the procedure ID  531  is set as the need arises. The work procedure information  53  shown in  FIG.  4    thereby indicates a procedure which is a constituent of each work procedure. Further, the work procedure information  53  indicates an execution sequence of the plurality of procedures. Furthermore, the work procedure information  53  shown in  FIG.  4    indicates whether or not each of the human and the system can perform each procedure and whether or not each procedure needs a performance qualification. Further, the work procedure information  53  shown in  FIG.  4    indicates a name of each procedure, a standard error rate of an error occurring when each procedure is performed, and an allowed time which is time allowed to spend until each procedure is performed. 
     Hereinafter, for simple description, procedures specified by the procedure IDs  531  of “procedure 1-1”, “procedure 1-2”, “procedure 1-3”, “procedure 1-4”, “procedure 2-1”, “procedure 2-2”, and “procedure 2-3” will be abbreviated as “procedure 1-1”, “procedure 1-2”, “procedure 1-3”, “procedure 1-4”, “procedure 2-1”, “procedure 2-2”, and “procedure 2-3”, respectively. 
     The work procedure information  54  shown in  FIG.  5    includes a procedure ID  541 , a name  542  and a work  543  which are corresponding to the procedure ID  541 , and a workload  544  and an error rate  545  which are corresponding to the work  543 . The name  542  corresponding to the procedure ID  541  specifies a name of the procedure specified by the procedure ID  541 . The work  543  corresponding to the procedure ID  541  specifies a work which is a constituent of the procedure specified by the procedure ID  541 . The workload  544  corresponding to the work  543  specifies a workload to be imposed on the operator who performs the work when the work specified by the work  543  is performed. The error rate  545  corresponding to the work  543  specifies an error rate of an error occurring when the work specified by the work  543  is performed. The work procedure information  54  shown in  FIG.  5    thereby indicates a work which is a constituent of each procedure. Further, the work procedure information  54  shown in  FIG.  5    indicates a workload to be imposed on the operator who performs each work when the work is performed and an error rate of an error occurring when each work is performed. The workload  544  is represented as “big”, “medium”, or “small”. The error rate  545  is represented as “high”, “medium”, or “low”. 
     3.4 Operation Information 
     The operation information storage unit  24  stores therein operation information  55 . The operation information  55  to be stored there is information on an operation of a plant performed by each operator. The operation information  55  is time series information. The operation information  55  is information in accordance with a state of the plant and an event occurring in the plant. The operation information  55  includes at least one kind of information selected from a group consisting of an operation content, the number of operations, a required operation time, and an operation frequency. The operation information  55  may include any information other than these kinds of information. The operation content includes start/stop of the motor, start/stop of the pump, open/close of the valve, check of the plant information, or the like. 
     3.5 Operator Information 
     The operator information storage unit  25  stores therein operator information  56 . The operator information  56  to be stored there is information on each operator. The operator information  56  indicates whether or not each operator is handling an operation of the plant, whether or not each operator can handle the operation of the plant when the operator is not handling the operation of the plant, and whether or not each operator has a performance qualification. The operator information  56  may indicate any information other than these kinds of information. For example, the operator information  56  may indicate a qualification, a business title, a character, an experience, or the like which each operator has. 
       FIG.  6    is a view showing an example of operator information stored in the work assignment device in accordance with the first preferred embodiment. 
     The operator information  56  shown in  FIG.  6    includes an operator ID  561 , and a handling state  562  and presence or absence of performance qualification  563  which are corresponding to the operator ID  561 . The operator ID  561  specifies an operator. The handling state  562  corresponding to the operator ID  561  indicates whether or not the operator specified by the operator ID  561  is handling the operation of the plant and whether or not the operator can handle the operation of the plant when the operator is not handling the operation of the plant. The presence or absence of performance qualification  563  corresponding to the operator ID  561  indicates whether or not the operator specified by the operator ID  561  has the performance qualification. The operator information  56  shown in  FIG.  6    thereby indicates whether or not each operator is handling the operation of the plant, whether or not each operator can handle the operation of the plant when the operator is not handling the operation of the plant, and whether or not each operator has the performance qualification. The handling state  562  is represented as “during handling”, “possible to handle”, or “impossible to handle”. 
     3.6 Biometric Information 
     The biometric information storage unit  26  stores therein biometric information  57 . The biometric information  57  to be stored there is biometric information of each operator. The biometric information  57  is time series information. The biometric information  57  is acquired by a contact-type or non-contact-type sensor or the like. The biometric information  57  includes at least one kind of information selected from a group consisting of a body temperature, a blood pressure, a heart rate, a respiratory rate, an electrocardiogram waveform, emotion, a stress, a line of sight, an eye movement, a blink, and an electroencephalogram (brain wave). 
     3.7 Evaluation Information 
     The evaluation information storage unit  27  stores therein evaluation information  58 . The evaluation information  58  to be stored there is information required to perform evaluation on each of a plurality of work assignment candidates  73  described later. In the first preferred embodiment, the evaluation information  58  indicates correction corresponding to each condition of an operator. In the first preferred embodiment, each condition of the operator refers to each degree of fatigue of the operator. Further, the correction refers to an error rate correction of the standard error rate. For this reason, the evaluation information  58  indicates the error rate correction of the standard error rate corresponding to each degree of fatigue of the operator. 
       FIG.  7    is a view showing an example of evaluation information stored in the work assignment device in accordance with the first preferred embodiment. 
     The evaluation information  58  shown in  FIG.  7    includes a degree of fatigue  581 , and an error rate correction  582  corresponding to the degree of fatigue  581 . The degree of fatigue  581  specifies the degree of fatigue of an operator. The error rate correction  582  corresponding to the degree of fatigue  581  specifies an error rate correction of the standard error rate corresponding to the degree of fatigue of the operator specified by the degree of fatigue  581 . The evaluation information  58  shown in  FIG.  7    thereby indicates an error rate correction of the standard error rate corresponding to each degree of fatigue of an operator. The error rate correction of the standard error rate includes a correction value applied to the standard error rate. By the correction value applied to the standard error rate, the standard error rate is multiplied. The degree of fatigue  581  is represented as “high”, “medium”, or “low”. 
     3.8 Presentation Information 
     The presentation information storage unit  28  stores therein presentation information  59 . The presentation information  59  to be stored there is information used for determining a presentation method for presenting a work assignment in accordance with the operator condition. The presentation information  59  indicates an operator condition corresponding to each pair of a workload and an error rate, for which presentation is possible. In the first preferred embodiment, the operator condition for which the presentation is possible refers to a degree of arousal of the operator for which the presentation is possible. For this reason, the presentation information  59  indicates the degree of arousal of the operator corresponding to each pair of the workload and the error rate, for which the presentation is possible. 
       FIG.  8    is a view showing an example of presentation information stored in the work assignment device in accordance with the first preferred embodiment. 
     The presentation information  59  shown in  FIG.  8    includes a workload  591 , an error rate  592 , and a degree of arousal  593  corresponding to a pair of the workload  591  and the error rate  592 , for which the presentation is possible. The degree of arousal  593  for which the presentation is possible specifies a degree of arousal of an operator for which the presentation is possible. The presentation information  59  shown in  FIG.  8    thereby indicates a degree of arousal of an operator corresponding to each pair of the workload and the error rate, for which the presentation is possible. The workload  591  is represented as “big”, “medium”, or “small”. The error rate  592  is represented as “high”, “medium”, or “low”. 
     4 Processing to be Performed 
     4.1 Outline 
     The work assignment device  2  dynamically assigns an operator and a system to a work on the basis of the plant condition and the operator condition. Further, the work assignment device  2  determines a presentation method for presenting the assignment of the operator to the work, to the operator, and presents the assignment of the operator to the work, to the operator, in accordance with the determined presentation method. Presentation of the assignment of the operator to the work is performed by outputting a result of the assignment of the operator to the work, to an external output device such as a display, a speaker, or the like. 
     Hereinafter, it is assumed that the plants are a “plant 1” and a “plant 2”, and the operators are an “operator 1”, an “operator 2”, and an “operator 3”. 
     4.2 Diagnosis of Plant Condition 
       FIG.  9    is a flowchart showing a processing performed by the work assignment device in accordance with the first preferred embodiment. 
     The work assignment device  2  executes Steps S 101  to S 108  shown in  FIG.  9   . 
     In Step S 101 , the plant condition diagnostic unit  31  diagnoses a condition of the plant. At that time, the plant condition diagnostic unit  31  acquires the plant information  51  from the plant information storage unit  21  and estimates an occurring event  71  which is occurring in the plant on the basis of the acquired plant information  51 . The acquired plant information  51  includes the alarm information and the plant value. The occurring event  71  which is estimated is at least one occurring event. Preferably, the plant condition diagnostic unit  31  estimates the occurring event  71  by using a knowledge base. In the knowledge base to be used, stored are data required to estimate the occurring event  71 . The stored data include a relation between a cause of a trouble and a range over which the event ripples. The data may include information other than the relation between the cause of the trouble and the range over which the event ripples. 
     Hereinafter, it is assumed that the estimated occurring events  71  are an “event 1” and an “event 2” occurring in the “plant 1” and the “plant 2”, respectively. 
     4.3 Determination of Work Procedure 
     In subsequent Step S 102 , the work procedure determination unit  32  determines a work procedure  72 . At that time, the work procedure determination unit  32  determines the work procedure  72  on the basis of the occurring event  71  which is estimated. At that time, the work procedure determination unit  32  acquires the event information  52  from the event information storage unit  22  and determines a work procedure to be performed when the estimated occurring event  71  occurs, which is indicated by the acquired event information  52 , as the work procedure  72  to be determined. 
     In a case where the estimated occurring events  71  are the “event 1” and the “event 2” and the acquired event information  52  is the event information shown in  FIG.  3   , the work procedure determination unit  32  determines the “procedure 1” and the “procedure 2” to be performed when the “event 1” and the “event 2” indicated by the event information  52  occur, respectively, as the work procedure  72  to be determined. 
     4.4 Constitution of Work Procedure Derivation Unit 
     By performing Steps S 101  and S 102 , the plant condition diagnostic unit  31  and the work procedure determination unit  32  constitute a work procedure derivation unit  41  for deriving the work procedure  72  on the basis of the plant information  51 . 
     4.5 Scheduling 
     In subsequent Step S 103 , the scheduling unit  33  performs scheduling. At that time, the scheduling unit  33  selects a plurality of work assignment candidates  73 . Each of the plurality of work assignment candidates  73  indicates an assignment of the operator or the system to a procedure which is a constituent of the determined work procedure  72 . The assignment is a feasible assignment. 
     The scheduling unit  33  acquires the work procedure information  53  from the work procedure information storage unit  23  and acquires the operator information  56  from the operator information storage unit  25 , and selects the plurality of work assignment candidates  73  on the basis of the work procedure information  53  and the operator information  56  which are acquired. 
     At that time, when the work procedure information  53  indicates that a human and a system can each perform the procedure which is a constituent of the work procedure  72 , the scheduling unit  33  assigns the human or the system to the procedure. Further, when the work procedure information  53  indicates that a human can perform the procedure but a system cannot perform the procedure, the scheduling unit  33  assigns the human to the procedure. Furthermore; when the work procedure information  53  indicates that a system can perform the procedure but a human cannot perform the procedure, the scheduling unit  33  assigns the system to the procedure. 
     Further, when the work procedure information  53  indicates that the procedure which is a constituent of the work procedure  72  needs a performance qualification, the scheduling unit  33  assigns an operator who has the performance qualification, which is indicated by the operator information  56 , to the procedure and does not assign an operator who does not have the performance qualification, which is indicated by the operator information  56 , to the procedure. 
     Furthermore, the scheduling unit  33  assigns an operator who is handling the operation of the plant or can handle the operation of the plant, which is indicated by the operator information  56 , to the procedure which is a constituent of the work procedure  72  and does not assign an operator who cannot handle the operation of the plant, which is indicated by the operator information  56 , to the procedure. 
       FIG.  10    is a view showing an exemplary selection of the plurality of work assignment candidates, which is performed by the work assignment device in accordance with the first preferred embodiment.  FIG.  11    is a view showing an exemplary result of the selection of the plurality of work assignment candidates, which is performed by the work assignment device in accordance with the first preferred embodiment. 
     Hereinafter, it is assumed that time required to perform each procedure is equally five minutes. 
     In a case where the determined work procedure  72  includes the “procedure 1” and the “procedure 2”, the acquired work procedure information  53  is the work procedure information shown in  FIG.  4   , and the acquired operator information  56  is the operator information shown in  FIG.  6   , a work assignment candidate  81  shown in  FIG.  10 ( a )  is selected for the “event 1” occurring in the “plant 1”. Further, a work assignment candidate  82  shown in  FIG.  10 ( b )  is selected for the “event 2” occurring in the “plant 2”. Furthermore, after the work assignment candidate  81  and the work assignment candidate  82  are selected, the plurality of work assignment candidates  73  shown in  FIG.  11    are selected for the whole of the “event 1” and the “event 2”. 
     In the case where the work assignment candidate  81  is selected for the “event 1”, it can be seen from the work procedure information  53  that an operator in charge who can perform the “procedure 1-1” having a name of “check of occurrence of event 1”, the “procedure 1-3” having a name of “control operation of equipment B”, and the “procedure 1-4” having a name of “check of end of event 1” is a human having the performance qualification. On the other hand, it can be seen from the operator information  56  that the human who is handling the operation of the plant or can handle the operation of the plant and has the performance qualification is the “operator 1”. For this reason, the “operator 1” is assigned to the “procedure 1-1”, the “procedure 1-3”, and the “procedure 1-4”. Further, it can be seen from the work procedure information  53  that an operator in charge who can perform the “procedure 1-2” having a name of “control operation of equipment A” is a human having the performance qualification and a system. On the other hand, it can be seen from the operator information  56  that the human who is handling the operation of the plant or can handle the operation of the plant and has the performance qualification is the “operator 1”. For this reason, the “operator 1” or a “system” is assigned to the “procedure 1-2”. Therefore, as shown in  FIG.  10 ( a ) , a “pattern A” in which the “operator 1” is assigned to the “procedure 1-1”, the “procedure 1-2”, the “procedure 1-3”, and the “procedure 1-4” and a “pattern B” in which the “operator 1” is assigned to the “procedure 1-1”, the “procedure 1-3”, and the “procedure 1-4” and the “system” is assigned to the “procedure 1-2” are selected as the work assignment candidate  81 . 
     In the case where the work assignment candidate  82  is selected for the “event 2”, it can be seen from the work procedure information  53  that an operator in charge who can perform the “procedure 2-1” having a name of “check of occurrence of event 2” is a system. For this reason, the “system” is assigned to the “procedure 2-1”. Further, it can be seen from the work procedure information  53  that an operator in charge who can perform the “event 2-2” having a name of “control operation of equipment C” and the “event 2-3” having a name of “check of end of event 2” is a human. On the other hand, it can be seen from the operator information  56  shown in  FIG.  6    that the human who is handling the operation of the plant or can handle the operation of the plant includes the “operator 1”, the “operator 2”, and the “operator 3”. For this reason, the “operator 1”, the “operator 2”, or the “operator 3” is assigned to the “event 2-2” and the “event 2-3”. Therefore, as shown in  FIG.  10 ( b ) , a “pattern C” in which the “system” is assigned to the “procedure 2-1” and the “operator 1” is assigned to the “procedure 2-2” and the “procedure 2-3”, a “pattern D” in which the “system” is assigned to the “procedure 2-1”, the “operator 2” or the “operator 3” is assigned to the “procedure 2-2”, and the “operator 1” is assigned to the “procedure 2-3”, a “pattern E” in which the “system” is assigned to the “procedure 2-1”, the “operator 1” is assigned to the “procedure 2-2”, and the “operator 2” or the “operator 3” is assigned to the “procedure 2-3”, and a “pattern F” in which the “system” is assigned to the “procedure 2-1” and the “operator 2” or the “operator 3” is assigned to the “procedure 2-2” and the “procedure 2-3” are selected as the work assignment candidate  82 . 
     In the case where the plurality of work assignment candidates  73  are selected for the whole of the “event 1” and the “event 2”, combinations of the “pattern A” or the “pattern B” and the “pattern C”, the “pattern D”, the “pattern E”, or the “pattern F” are the plurality of work assignment candidates  73 . At that time, an unfeasible combination is excluded. The unfeasible combination is any combination in which the same operator performs two or more procedures at the same time. The reason why the combination in which the same operator performs two or more procedures at the same time is an unfeasible combination is that one operator cannot perform two or more procedures at the same time. For example, the combination of the “pattern A” and the “pattern C” is excluded since this combination is a combination in which the “operator 1” performs the “procedure 1-2” and the “procedure 2-2” at the same time and performs the “procedure 1-3” and the “procedure 2-3” at the same time. Similarly, the combination of the “pattern A” and the “pattern D”, the combination of the “pattern A” and the “pattern E”, the combination of the “pattern B” and the “pattern C”, and the combination of the “pattern B” and the “pattern D” are also excluded. Therefore, as shown in  FIG.  11   , the combination of the “pattern A” and the “pattern F”, the combination of the “pattern B” and the “pattern E”, and the combination of the “pattern B” and the “pattern F” are selected as the plurality of work assignment candidates  73 . 
     4.6 Judgment of Operator Condition 
     In subsequent Step S 104 , the operator condition judgment unit  34  judges the operator condition  74 . At that time, the operator condition judgment unit  34  acquires the operation information  55  from the operation information storage unit  24  and acquires the biometric information  57  from the biometric information storage unit  26 , and judges the operator condition  74  on the basis of the operation information  55  and the biometric information  57  which are acquired. The operator condition judgment unit  34  may acquire only one of the operation information  55  and the biometric information  57  and judge the operator condition  74  on the basis of only the one of the operation information  55  and the biometric information  57 . The operator condition  74  to be judged includes at least one kind of information selected from a group consisting of a load status, a condition recognition power, a degree of fatigue, a degree of arousal, and a concentration power of the operator. The operator condition judgment unit  34  judges the load status of the operator on the basis of, for example, a body temperature, a blood pressure, a heart rate, a respiratory rate, a stress, the number of operations, a required operation time, an operation frequency, or the like. Alternatively, the operator condition judgment unit  34  judges the condition recognition power of the operator on the basis of a heart rate, a respiratory rate, an eye movement, an electroencephalogram (brain wave), or the like. More alternatively, the operator condition judgment unit  34  judges the degree of fatigue of the operator on the basis of the number of operations, an operation speed, an operation frequency, or the like. Alternatively, the operator condition judgment unit  34  judges the degree of arousal of the operator on the basis of a heart rate, a respiratory rate, an electroencephalogram (brain wave), a blink, or the like. More alternatively, the operator condition judgment unit  34  judges the concentration power of the operator on the basis of a heart rate, heart rate variability, respiration, or the like. Alternatively, the operator condition judgment unit  34  judges the degree of fatigue of the operator on the basis of a required operation time. Hereinafter, it is assumed that the operator condition judgment unit  34  judges the degree of fatigue of the operator on the basis of a required operation time. 
       FIG.  12    is a view showing an exemplary judgment of the degree of fatigue of the operator on the basis of the required operation time, which is performed by the work assignment device in accordance with the first preferred embodiment. 
     The operator condition judgment unit  34  judges the degree of fatigue to be higher as the required operation time becomes longer. For example, as shown in  FIG.  12   , when the difference t between the required operation time and a standard required time, which is obtained by subtracting the standard required time from the required operation time, is not shorter than 30 seconds, the operator condition judgment unit  34  judges the degree of fatigue to be “high”. Further, when the difference t between the required operation time and the standard required time is not longer than −30 seconds, the operator condition judgment unit  34  judges the degree of fatigue to be “low”. Furthermore, when the difference t between the required operation time and the standard required time is shorter than 30 seconds and longer than −30 seconds, the operator condition judgment unit  34  judges the degree of fatigue to be “medium”. 
     Hereinafter, it is assumed that the degree of fatigue of the “operator 1” is judged to be “high” on the basis of the required operation time of the “operator 1”, the degree of fatigue of the “operator 2” is judged to be “low” on the basis of the required operation time of the “operator 2”, and the degree of fatigue of the “operator 3” is judged to be “medium” on the basis of the required operation time of the “operator 3”. 
     4.7 Evaluation of Work Assignment Candidate 
     In subsequent Step S 105 , the work assignment evaluation unit  35  performs evaluation on each of the plurality of work assignment candidates  73 . At that time, the work assignment evaluation unit  35  acquires the work procedure information  53  from the work procedure information storage unit  23  and acquires the evaluation information  58  from the evaluation information storage unit  27 , and performs evaluation on the basis of the work procedure information  53  and the evaluation information  58  which are acquired and the judged operator condition  74 . Specifically, the work assignment evaluation unit  35  performs evaluation on the basis of the standard error rate of the error occurring when the procedure which is a constituent of the work procedure  72  and indicated by the work procedure information  53  is performed. Further, the work assignment evaluation unit  35  applies the error rate correction corresponding to the degree of fatigue of the operator, which is indicated by the evaluation information  58 , to the evaluation. It is thereby possible to perform the evaluation in accordance with the operator condition  74 . In the first preferred embodiment, performing the evaluation is calculating an evaluation value. The evaluation value to be calculated indicates a magnitude of risk. The evaluation value becomes larger as the risk increases. 
       FIG.  13    is a flowchart showing an exemplary process for evaluation, which is performed by the work assignment device in accordance with the first preferred embodiment.  FIG.  14    is a view showing exemplary evaluation performed by the work assignment device in accordance with the first preferred embodiment. 
     The work assignment evaluation unit  35  executes Steps S 111  to S 115  shown in  FIG.  13   . 
     In Step S 111 , the work assignment evaluation unit  35  acquires the standard error rate from the work procedure information  53 . 
     In a case where the evaluation is performed on the combination of the “pattern A” and the “pattern F”, the work assignment evaluation unit  35  acquires the standard error rates of “0.001”, “0.001”, “0.001”, “0.001”, “0.0001”, “0.001”, and “0.001” of the errors occurring when the “procedure 1-1”, the “procedure 1-2”, the “procedure 1-3”, the “procedure 1-4”, the “procedure 2-1”, the “procedure 2-2”, and the “procedure 2-3” which are included in the combination are performed, respectively, from the work procedure information  53 . 
     In subsequent Step S 112 , the work assignment evaluation unit  35  performs the error rate correction on the acquired standard error rate on the basis of the degree of fatigue of the operator. 
     In the case where the evaluation is performed on the combination of the “pattern A” and the “pattern F”, the work assignment evaluation unit  35  acquires the fatigue degrees of “high”, “low”, and “medium” of the “operator 1”, the “operator 2”, and the “operator 3” which are included in the combination, from the operator condition judgment unit  34 . Further, the work assignment evaluation unit  35  acquires the error rate corrections corresponding to “high”, “low”, and “medium” which are acquired, i.e., “(the standard error rate)×10.0”, “(the standard error rate)×1.0”, and “(the standard error rate)×5.0”, respectively, from the evaluation information  58 . Furthermore, as shown in  FIG.  14   , the work assignment evaluation unit  35  acquires an error rate, i.e., “0.01”, of the “procedure 1-1”, the “procedure 1-2”, the “procedure 1-3”, and the “procedure 1-4” by performing the error rate correction, i.e., “(the standard error rate)×10.0”, corresponding to “high” which is the degree of fatigue of the “operator 1” on the standard error rate, i.e., “0.001”, of the error occurring in the case of performing the “procedure 1-1”, the “procedure 1-2”, the “procedure 1-3”, and the “procedure 1-4” to which the “operator 1” is assigned. Further, the work assignment evaluation unit  35  acquires an error rate, i.e., “0.001”, of the “procedure 2-2” and the “procedure 2-3” by performing the error rate correction, i.e., “(the standard error rate)×1.0”, corresponding to “low” which is the degree of fatigue of the “operator 2” on the standard error rate, i.e., “0.001”, of the error occurring in the case of performing the “procedure 2-2” and the “procedure 2-3” to which the “operator 2” is assigned. Furthermore, the work assignment evaluation unit  35  acquires an error rate, i.e., “0.005”, of the “procedure 2-2” and the “procedure 2-3” by performing the error rate correction, i.e., “(the standard error rate)×5.0”, corresponding to “medium” which is the degree of fatigue of the “operator 3” on the standard error rate, i.e., “0.001”, of the error occurring in the case of performing the “procedure 2-2” and the “procedure 2-3” to which the “operator 3” is assigned. 
     In subsequent Step S 113 , the work assignment evaluation unit  35  calculates a total error rate of each pattern. 
     In the case where the evaluation is performed on the combination of the “pattern A” and the “pattern F”, the work assignment evaluation unit  35  calculates the total error rate of the “pattern A”, i.e., “1.0×E-8”, by multiplying the error rates, i.e., “0.01”, “0.01”, “0.01”, and “0.01”, of the “procedure 1-1”, the “procedure 1-2”, the “procedure 1-3”, and the “procedure 1-4”, respectively, included in the “pattern A” by one another. Herein, “E-8” means the minus eighth power of 10. As to the total error rate of the “pattern F”, there is a difference between the total error rate calculated from the error rate acquired by performing the error rate correction of “(the standard error rate)×1.0” corresponding to “low” which is the degree of fatigue of the “operator 2” and that calculated from the error rate acquired by performing the error rate correction of “(the standard error rate)×5.0” corresponding to “medium” which is the degree of fatigue of the “operator 3”. The total error rate of the “pattern F” calculated from the former error rate is, however, lower than the total error rate of the “pattern F” calculated from the latter error rate. For this reason, the work assignment evaluation unit  35  adopts the total error rate of the “pattern F” calculated from the former error rate. Therefore, the work assignment evaluation unit  35  calculates the total error rate of the “pattern F”, i.e., “1.0×E-10”, by multiplying the error rates, i.e., “0.0001”, “0.001”, and “0.001”, of the “procedure 2-1”, the “procedure 2-2”, and the “procedure 2-3”, respectively, included in the “pattern F” by one another. 
     In subsequent Step S 114 , the work assignment evaluation unit  35  calculates an evaluation value of the combination of the patterns. 
     In the case where the evaluation is performed on the combination of the “pattern A” and the “pattern F”, as shown in  FIG.  14   , the work assignment evaluation unit  35  calculates an evaluation value of the “pattern A”, i.e., “3.0×E-8” by multiplying the total error rate of the “pattern A”, i.e., “1.0×E-8” by a coefficient of “3” which is given to the degree of influence of the “event 1”, i.e., “big”. Further, the work assignment evaluation unit  35  calculates an evaluation value of the “pattern F”, i.e., “2.0×E-10” by multiplying the total error rate of the “pattern F”, i.e., “1.0×E-10” by a coefficient of “2” which is given to the degree of influence of the “event 2”, i.e., “medium”. Furthermore, the work assignment evaluation unit  35  calculates an evaluation value of the combination of the “pattern A” and the “pattern F”, i.e., “3.0×E-8+2.0×E-10” by adding the evaluation value of the “pattern A”, i.e., “3.0×E-8”, to the evaluation value of the “pattern F”, i.e., “2.0×E-10”. In the case where the evaluation is performed on the combination of the “pattern B” and the “pattern E”, the work assignment evaluation unit  35  similarly calculates an evaluation value of the combination, i.e., “3.0×E-10+2.0×E-9”. Further, in the case where the evaluation is performed on the combination of the “pattern B” and the “pattern F”, the work assignment evaluation unit  35  similarly calculates an evaluation value of the combination, i.e., “3.0×E-10+2.0×E-10”. 
     In Step S 115 , the work assignment evaluation unit  35  judges whether or not calculation of the respective evaluation values of all the combinations is completed. When the calculation of the respective evaluation values of all the combinations is not completed, the work assignment evaluation unit  35  executes Steps S 111  to S 115  again. When the calculation of the respective evaluation values of all the combinations is completed, the work assignment evaluation unit  35  finishes the process for evaluation. 
     4.8 Determination of Work Assignment 
     With reference back to  FIG.  9   , the description continues. 
     In subsequent Step S 106 , the work assignment determination unit  36  determines the work assignment. At that time, the work assignment determination unit  36  determines the work assignment  76  from the plurality of selected work assignment candidates  73  on the basis of the result  75  of the evaluation which is performed. The work assignment determination unit  36  determines the work assignment candidate having the highest evaluation result as the work assignment  76 . In the first preferred embodiment, determining the work assignment  76  on the basis of the evaluation result  75  is determining the work assignment  76  on the basis of whether the evaluation value is large or small. Further, determining the work assignment  76  on the basis of whether the evaluation value is large or small is determining the work assignment candidate having an evaluation value indicating the magnitude of the lowest risk, as the work assignment  76 . In a case where the evaluation value becomes larger as the risk increases, the evaluation value indicating the magnitude of the lowest risk is the smallest evaluation value. 
     In the case where the evaluation value of the combination of the “pattern A” and the “pattern F” is “3.0×E-8+2.0×E-10”, the evaluation value of the combination of the “pattern B” and the “pattern E” is “3.0×E-10+2.0×E-9”, and the evaluation value of the combination of the “pattern B” and the “pattern F” is “3.0×E-10+2.0×E-10”, the work assignment determination unit  36  determines the combination of the “pattern B” and the “pattern F” having the smallest evaluation value, i.e., “3.0×E-10+2.0×E-10”, as the work assignment  76 . 
     4.9 Determination of Presentation Method 
     In subsequent Step S 107 , the work assignment presentation method determination unit  37  determines a presentation method  77  for presenting the determined work assignment  76  to the operator. At that time, the work assignment presentation method determination unit  37  acquires the work procedure information  53  and the work procedure information  54  from the work procedure information storage unit  23 , and determines the presentation method  77  on the basis of the work procedure information  53  and the work procedure information  54  which are acquired, the judged operator condition  74 , and the determined work assignment  76 . It is thereby possible to dynamically determine the presentation method  77  in accordance with the operator condition  74 . The presentation method  77  includes at least one kind of information selected from a group consisting of a presentation content, a presentation means, and a presentation timing. Hereinafter, it is assumed that the presentation method  77  includes the presentation content, the presentation means, and the presentation timing. The work assignment presentation method determination unit  37  specifies the workload imposed on the operator performing the work when the work is performed and the error rate of the error occurring when the work is performed, which are indicated by the work procedure information  54 . Further, the work assignment presentation method determination unit  37  specifies the operator condition corresponding to the pair of the workload and the error rate which are specified, for which the presentation is possible, which is indicated by the presentation information  59 . Furthermore, the work assignment presentation method determination unit  37  determines a timing when the operator condition  74  is the specified operator condition, for which the presentation is possible, as the presentation timing. 
       FIG.  15    is a flowchart showing an exemplary process of determining the presentation method, which is performed by the work assignment device in accordance with the first preferred embodiment.  FIG.  16    is a view showing exemplary determination of the presentation method, which is performed by the work assignment device in accordance with the first preferred embodiment. 
     The work assignment presentation method determination unit  37  executes Steps S 121  to S 125  shown in  FIG.  15   . 
     In Step S 121 , the work assignment presentation method determination unit  37  acquires work information from the work procedure information storage unit  23  and the work assignment determination unit  36 . The acquired work information includes a work content performed before or to be performed after, a time until the next work, a plant to be operated, or the like. 
     In subsequent Step S 122 , the work assignment presentation method determination unit  37  determines a presentation content to be presented to the operator, from the acquired work information and the operator condition  74 . 
     In a case of determining a presentation method for presenting the assignment of the “operator 1” to the “procedure 1-4” which is included in the combination of the “pattern A” and the “pattern F”, to the “operator 1”, the work assignment presentation method determination unit  37  determines to present a work content which should be performed in the “procedure 1-4” to the “operator 1”. 
     In subsequent Step S 123 , the work assignment presentation method determination unit  37  determines a presentation means from the acquired work information and the operator condition  74 . 
     In the case of determining the presentation method for presenting the assignment of the “operator 1” to the “procedure 1-4” which is included in the combination of the “pattern A” and the “pattern F”, to the “operator 1”, the work assignment presentation method determination unit  37  determines to present the work content to the “operator 1” by displaying the work content that should be performed, for example, on a terminal which the “operator 1” operates. 
     In subsequent Step S 124 , the work assignment presentation method determination unit  37  acquires the operator condition  74  in real time. Hereinafter, it is assumed that the operator condition  74  which is acquired in real time includes a degree of arousal of the operator. For example, the degree of arousal of the operator is high when a line of sight moves quickly and frequently and a blink cycle is stable, and is low when the line of sight moves slowly and blinking is slow. 
     In subsequent Step S 125 , the work assignment presentation method determination unit  37  determines an optimum presentation timing from the work information and the operator condition  74  which are acquired. 
     In the case of determining the presentation method for presenting the assignment of the “operator 1” to the “procedure 1-4” which is included in the combination of the “pattern A” and the “pattern F”, to the “operator 1”, the work assignment presentation method determination unit  37  can grasp that the “procedure 1-3” performed before the “procedure 1-4” consists of an “operation A”, an “operation B”, a “check work C”, and an “operation D”, from the work procedure information  53  and the work procedure information  54 . Further, the work assignment presentation method determination unit  37  can grasp the workload and the error rate corresponding to each work of the “operation A”, the “operation B”, the “check work C”, and the “operation D”, from the work procedure information  54 . Furthermore, from the presentation information  59 , the work assignment presentation method determination unit  37  can grasp the degree of arousal corresponding to the pair of the workload and the error rate, for which the presentation is possible. From the first line of the presentation information  59 , for example, the work assignment presentation method determination unit  37  can grasp the degree of arousal of “excellent” corresponding to the workload of “big” and the error rate of “high”, for which the presentation is possible. For this reason, as shown in  FIG.  16   , from the work procedure information  53 , the work procedure information  54 , and the presentation information  59 , the work assignment presentation method determination unit  37  can grasp the degree of arousal corresponding to each work of the “operation A”, the “operation B”, the “check work C”, and the “operation D”, for which the presentation is possible. In  FIG.  16   , the degree of arousal corresponding to each work of the “operation A”, the “operation B”, the “check work C”, and the “operation D”, for which the presentation is possible, is represented by being filled with gray. Further, in  FIG.  16   , the degree of arousal of the operator which is acquired in real time is represented by a curve  91 . In  FIG.  16   , at the point in time represented by a point  92 , the workload becomes “small”, the error rate becomes “low”, and the degree of arousal of the operator represented by the curve  91  becomes “fair” which is a degree of arousal represented by being filled with gray, for which the presentation is possible. For this reason, the point in time represented by the point  92  is determined as the optimum presentation timing. 
     4.10 Presentation of Work Assignment 
     With reference back to  FIG.  9   , the description continues. 
     In subsequent Step S 108 , the work assignment presentation unit  38  presents the determined work assignment  76  to the operator by using the determined presentation method  77 . 
     The work assignment presentation unit  38  presents the work assignment  76  to the operator by outputting the content of the work assignment  76  on the output device. The output device is a display, a speaker, or the like. 
       FIG.  17    is a view showing a work content that should be performed next by the operator, which is displayed on an operation screen of the plant operated by the operator, by the work assignment device in accordance with the first preferred embodiment. 
       FIG.  17    shows the work content that should be performed next by the “operator 1”, which is displayed on an operation screen  93  of the “plant 1” operated by the “operator 1”. 
     5 Variations 
     In the first preferred embodiment, the operator condition  74  includes the degree of fatigue of the operator, and on the basis of the degree of fatigue of the operator, the error rate correction is performed on the standard error rate. The operator condition  74 , however, may include an operator condition other than the degree of fatigue of the operator, and the error rate correction may be performed on the standard error rate on the basis of the operator condition. For example, the operator condition  74  may include the load status, the condition recognition power, the degree of arousal, the concentration power, or the like, and the error rate correction may be performed on the standard error rate on the basis of the load status, the condition recognition power, the degree of arousal, or the concentration power. The operator condition  74  may include a plurality of operator conditions, and in comprehensive consideration of the plurality of operator conditions, the error rate correction may be performed on the standard error rate on the basis of the plurality of operator conditions. For example, the error rate correction may be performed on the standard error rate on the basis of a simple sum or a weighted sum of a plurality of values representing the plurality of operator conditions, respectively. In a case where the error rate correction is performed on the standard error rate on the basis of the weighted sum, weighting may be dynamically changed. Correction may be performed by any method other than the error rate correction on the standard error rate. 
     In the first preferred embodiment, the operator condition  74  judged by the operator condition judgment unit  34  is a current operator condition. The operator condition  74  judged by the operator condition judgment unit  34 , however, may be a future operator condition. In the case where the operator condition  74  judged by the operator condition judgment unit  34  is a future operator condition, the operator condition judgment unit  34  predicts the future operator condition in order to judge the future operator condition. 
     In the first preferred embodiment, the work assignment evaluation unit  35  calculates the evaluation value without consideration of an error caused by taking over the work. The work assignment evaluation unit  35 , however, may calculate the evaluation value in consideration of an error caused by taking over the work. In a case where a new work is performed, a case where the plant on which a work is performed is changed, or the like case, the work assignment evaluation unit  35  may calculate the evaluation value by adding an error rate of an error caused by taking over the work to a basic error rate. 
     In the first preferred embodiment, the evaluation value indicates the magnitude of the risk. The evaluation value, however, may indicate the degree of any item other than the magnitude of the risk. For example, the evaluation value may indicate the level of cost, the length of required time, the priority level, or the like. The evaluation value may comprehensively indicate the degrees of the plurality of items. For example, the evaluation value may be a simple sum or a weighted sum of a plurality of values representing the degrees of the plurality of items, respectively. In a case where the evaluation value is the weighted sum of a plurality of values, weighting may be dynamically changed. 
     In the first preferred embodiment, it is assumed that the procedures each have the same required time to perform and immediately after one procedure is finished, the next procedure is started. More complicated procedure, however, may be performed. For example, the procedures may have different required times to perform. Further, only if the procedure is performed within the allowed time, with a time interval after one procedure is finished, the next procedure may be started. 
     6 Effects 
     According to the first preferred embodiment, the work procedure  72  is derived on the basis of the plant information  51  on the plant, and the assignment of the operator to the procedure which is a constituent of the derived work procedure  72  is determined. It is thereby possible to dynamically perform the assignment of the operator in accordance with the plant condition. 
     Further, according to the first preferred embodiment, the operator condition  74  is judged on the basis of the operation information  55  on the operation of the plant by each operator and the biometric information  57  of each operator, the evaluation is performed on each of the plurality of work assignment candidates  73  on the basis of the judged operator condition  74 , and the work assignment  76  is determined on the basis of the evaluation result  75 . It is thereby possible to dynamically perform the assignment of the operator in accordance with the operator condition  74 . 
     With these processes, it is possible to correctly deal with the event occurring in the plant in a short time. 
     Further, according to the first preferred embodiment, the operator condition  74  is judged on the basis of the operation information  55  on the operation of the plant by each operator and the biometric information  57  of each operator, and the presentation method  77  for presenting the work assignment to the operator on the basis of the judged operator condition  74 . For this reason, the presentation in accordance with the operator condition  74  can be performed. It is thereby possible to perform handling of the occurring event  71  occurring in the plant, suitable for the operator condition  74 . 
     In the background art, there have been cases where the condition of a human, such as the degree of fatigue or the like, is used for the user interface control. There has not been a case, however, where the operator condition such as the workload, the condition recognition, or the like of the operator is acquired and the acquired operator condition is used for dynamic assignment of the operator. Further, in the background art, since the assignment is not presented to the operator in sufficient consideration of the condition of the operator taking over the work in assigning the work to the operator, the operator cannot correctly recognize the situation and cannot smoothly take over the work. According to the first preferred embodiment, it is possible to suppress occurrence of such problems. 
     Further, in the present disclosure, the preferred embodiment may be changed or omitted as appropriate, without departing from the scope of the disclosure. 
     While the present disclosure has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised. 
     Explanation of Reference Signs 
       2  work assignment device,  31  plant condition diagnostic unit,  32  work procedure determination unit,  33  scheduling unit,  34  operator condition judgment unit,  35  work assignment evaluation unit,  36  work assignment determination unit,  37  work assignment presentation method determination unit,  38  work assignment presentation unit,  41  work procedure derivation unit,  51  plant information,  52  event information,  53  work procedure information,  54  work procedure information,  55  operation information,  56  operator information,  57  biometric information,  58  evaluation information,  59  presentation information