Abstract:
A distributed control system and a control method for the distributed control system are provided that reduce adjustment and setup steps required when the system are applied to a control using sensors and actuators. The distributed control system includes a central communication unit and terminal communication units, the central communication unit and the terminal communication units connected to each other through a network. Communication control setup is automatically performed for each of the terminal communication units when control is exercised by using sensors and actuators connected to the terminal communication units based on each transmission characteristic of the time when a physical quantity generated by driving each of the actuators propagates to each of the sensors and on the setup of required performance of control.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese 
         [0002]    Patent Application JP 2014-084168 filed on Apr. 16, 2014, the content of which is hereby incorporated by reference into this application. 
       FIELD OF THE INVENTION 
       [0003]    The present invention relates to a distributed control system which a plurality of sensors and actuators are connected to and controls the actuators based on information from the sensors. 
       BACKGROUND OF THE INVENTION 
       [0004]    In recent years, a distributed control system is employed which connects through a network and collectively controls distributed sensors and actuators in a single system to reduce the wiring for an industrial apparatus or a factory automation (FA) system. 
         [0005]    The distributed control system generally includes a central communication unit and a plurality of terminal communication units. The central communication unit provides integrated control of an overall sequence. The terminal communication units provide input/output control of the sensors and actuators. 
         [0006]    In the distributed control system, a network is formed between the central communication unit and the terminal communication units. 
         [0007]    The network is generally formed, for example, of a multi-drop topology or a daisy chain topology. 
         [0008]    The central communication unit transfers control information to the terminal communication units through the network. The terminal communication units exercise input/output control of the sensors and actuators in accordance with the control information. 
         [0009]    In addition, the terminal communication units transfer control information input from the sensors and actuators to the central communication unit through the network. 
         [0010]    As described above, the distributed control system transmits and receives the control information between the central communication unit and the terminal communication units through the network so that the central communication unit can provide overall control of the distributed sensors and actuators. 
         [0011]    Meanwhile, it is demanded in industrial fields that a control system using many sensors and actuators should have improved performance, for instance, by providing high speed and high accuracy. 
         [0012]    The improvement of the performance of the above-mentioned control system may be obstructed by the response performance of a network for the distributed control system. If the network&#39;s response performance is low, the improvement of the performance of the above-mentioned control system is significantly obstructed. Therefore, it is desired that the response performance of the network should be as high as possible. 
         [0013]    However, as common characteristics of the distributed control system, the response performance of the network deteriorates when the number of the sensors and actuators to be controlled increases. 
         [0014]    Therefore, special communication control methods are explored for the network in the distributed control system so that the response performance is maintained as high as possible for the control of many sensors and actuators. 
         [0015]    As a relevant related-art technology, for instance, JP 2006-209646 discloses a technology in which a synchronization signal is transmitted to all the external instruments when all the external instruments are confirmed ready for operation. 
         [0016]    However, the technology described in JP 2006-209646 does not provide measures against an increase in the adjustment and setup steps of communication control. Therefore, it is difficult for the above-mentioned related-art technology to reduce the adjustment and setup steps required when the distributed control system is applied to a control system including many sensors and actuators. 
         [0017]    The present invention has been made in view of the above circumstances to provide a distributed control system that is capable of automating adjustment and setup for communication control when the distributed control system is applied to a control system including many sensors and many actuators. 
         [0018]    The present invention has also been made to provide a communication control system that automates the adjustment and setup for communication control to achieve required performance of the control system including many sensors and many actuators. 
       SUMMARY OF THE INVENTION 
       [0019]    According to an aspect of the present invention, a distributed control system includes a central communication unit; a plurality of terminal communication units, each of which is connected to at least one sensor, at least one actuator, or both of at least one sensor and at least one actuator; a display and input unit connected to the central communication unit; and a network which connects the central communication unit and the terminal communication units with communication paths and has a plurality of communication channels between the central communication unit and the terminal communication units. The central communication unit includes a communication signal control section, a plurality of sets of communication ports, a central communication control section, and a communication control setup computation section. Each of the terminal communication units includes a communication signal control section, a plurality of sets of communication ports, a terminal communication control section, a communication channel setup section, a control information input/output setup section, a control computation section, and a device control section. The network includes a transmission path between at least one communication port of the terminal communication units and at least one communication port of the central communication unit or at least one communication port of another terminal communication unit. The central communication unit sets up communication control for the terminal communication units based on transmission characteristic which is increase/decrease characteristic of a physical quantity, the physical quantity is a quantity of a time when a physical quantity generated by driving the actuator connected to a terminal communication unit propagates to a sensor connected to the terminal communication unit or a sensor connected to another terminal communication unit. 
         [0020]    Preferably, the central communication unit further includes a transmission characteristic acquisition section. Each of the terminal communication units further includes a transmission characteristic computation section. Each of the terminal communication units computes a transmission characteristic from a set of the actuator and the sensor with the transmission characteristic computation section and transfers the computed transmission characteristic to the central communication unit. The central communication unit stores the transmission characteristic transferred from the terminal communication units in the transmission characteristic acquisition section. 
         [0021]    Preferably, the distributed control system is applied as a control apparatus for an active vibration damping instrument. A plurality of actuators and sensors which are connected to the terminal communication units are disposed at a plurality of locations of an object of which vibration is to be damped. 
         [0022]    Preferably, one of the terminal communication units connected to the actuator drives the actuator. The terminal communication unit driving the actuator transfers periodically an output value to the actuator through the network to all the terminal communication units connected to the sensor. All the terminal communication units connected to the sensor compute the transmission characteristic simultaneously with driving of the actuator by using a physical quantity input from the sensor and the output value to the actuator, which is transferred through the network. 
         [0023]    Preferably, a terminal communication unit performs an automatic control process in which a signal from at least one sensor connected to the terminal communication unit or other terminal communication units is used as an input and driving of at least one actuator connected to the terminal communication unit or other terminal communication units is used as an output. If another terminal communication unit intervenes between an input and output of the automatic control process, the terminal communication unit performs the automatic control process by using a communication of the network. 
         [0024]    Preferably, when an amplitude of the transmission characteristic is not greater than a threshold value set for the central communication unit, the central communication unit prevents a set of the terminal communication units connected to the actuator and the sensor related to the transmission characteristic from communicating during the automatic control process by setting a communication control method for each of the terminal communication units through the network. The terminal communication units communicate during the automatic control process in accordance with the communication control method set for the central communication unit. 
         [0025]    Preferably, the central communication unit selects a terminal communication unit to perform the automatic control process so as to minimize an amount of communication data required for the automatic control process of the terminal communication unit, and sets a method of the automatic control process for the selected terminal communication unit through the network. The terminal communication unit performs the automatic control process in accordance with the method of the automatic control process set by the central communication unit. 
         [0026]    Preferably, the central communication unit compares an amount of communication data required for the automatic control process of a terminal communication unit, a communication delay time calculated from the communication channels, and an acceptable delay time that is a maximum delay time acceptable for control input/output which is calculated from required performance of the automatic control process. The central communication unit selects a terminal communication unit to perform the automatic control process, sets a method of the automatic control process for the selected terminal communication unit through the network, and sets a communication channel and communication cycle in execution of the automatic control process for each of the terminal communication units connected to the actuator and the sensor related to the automatic control process, so that the value of the communication delay time does not exceed the acceptable delay time. A terminal communication unit for which the method of the automatic control process is set by the central communication unit performs the automatic control process in accordance with a setting of the automatic control process for the terminal communication unit. A terminal communication unit for which the communication channel and the communication cycle are set by the central communication unit performs communication control in accordance with the communication channel and the communication cycle that are set for the terminal communication unit. 
         [0027]    Preferably, the display and input unit has an input function to input setup information for the central communication unit, and transfer the setup information to the central communication unit. The display and input unit has an output function to acquire the setup information for the central communication unit, the transmission characteristic to be stored in the central communication unit, and the setup information for the terminal communication units from the central communication unit, and output the information acquired from the central communication unit. The input function and the output function are executable by using software-based GUI (graphical user interface). 
         [0028]    According to the present invention, the distributed control system can automate adjustment and setup for communication control, which makes it possible to reduce manual steps for adjustment and setup when the distributed control system is applied to a control system including many sensors and many actuators and the number of sensors and/or actuators is changed. 
         [0029]    According to the present invention, the distributed control system can ensure required performance of the control system including many sensors and many actuators, and makes it easy to perform adjustment and setup for the communication control. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIGS. 1A and 1B  are diagrams illustrating an example in which a distributed control system according to an embodiment of the present invention is used as a vibration damping instrument; 
           [0031]      FIG. 2  is a diagram illustrating a configuration of the distributed control system according to the embodiment of the present invention; 
           [0032]      FIG. 3  is a flowchart illustrating processing steps performed by the distributed control system according to the embodiment of the present invention; 
           [0033]      FIG. 4  is a flowchart illustrating processing steps of acquiring transmission characteristics of the distributed control system according to the embodiment of the present invention; 
           [0034]      FIG. 5  is a flowchart illustrating a setup sequence for an automatic control process and communication control of the distributed control system according to the embodiment of the present invention; 
           [0035]      FIG. 6  is a diagram illustrating an exemplary setup for the automatic control process and communication control of the distributed control system according to the embodiment of the present invention; and 
           [0036]      FIG. 7  shows a setup screen of a display and input unit according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    An embodiment of the present invention will now be described with reference to the drawings. The embodiment will now be described on the assumption that a distributed control system is applied to an active vibration damping instrument. If plural identical elements are to be distinguished from each other for explanation purposes, a reference numeral is suffixed with an alphabetical character (a, b, c, . . . ). If the identical elements need not particularly be distinguished from each other for explanation purposes, the reference numeral is not suffixed with an alphabetical character. 
       First Embodiment 
       [0038]      FIGS. 1A and 1B  are diagrams illustrating an example in which a distributed control system  10  according to the embodiment of the present invention is used as a vibration damping instrument. 
         [0039]    As shown in  FIG. 1A , the distributed control system  10  according to the present embodiment is applied as a vibration damping instrument that actively damps the vibration of an object  20  of which vibration is to be damped. The distributed control system  10  is connected to and controls sensors  130   a - 130   c  and actuators  131   a - 131   c,  which are mounted on the object  20 . 
         [0040]    As shown in  FIG. 1B , the distributed control system  10  includes a central communication unit  100 , plural terminal communication units  120   a - 120   f,  and a network  150 . The sensors  130   a - 130   c  and the actuators  131   a - 131   c  are respectively connected to the terminal communication units  120   a,    120   c,    120   e ,  120   b,    120   d,  and  120   f.    
         [0041]    The network  150  is configured to include a communication path among the central communication unit  100  and the terminal communication units  120   a,    120   d  and among the terminal communication units  120   a - 120   f.    
         [0042]      FIG. 2  is a diagram illustrating a configuration of the distributed control system  10  according to the present embodiment. 
         [0043]    The central communication unit  100  includes a communication signal control section  110 , plural sets of communication ports  140 , a central communication control section  101 , a transmission characteristics acquisition section  102 , and a communication control setup computation section  103 . 
         [0044]    Each of the terminal communication units  120  includes a communication signal control section  110 , plural sets of communication ports  140 , a terminal communication control section  121 , a communication channel setup section  122 , a control information input/output setup section  123 , a control computation section  124 , a transmission characteristics computation section  125 , and a device control section  126 . 
         [0045]    The network  150  is configured to include a transmission path between at least one communication port  140  of each terminal communication unit  120  and a communication port  140  of the central communication unit  100  or a communication port  140  of another terminal communication unit  120 . 
         [0046]    The communication signal control section  110  provides bidirectional communication between the central communication unit  100  and a terminal communication unit  120  or between a terminal communication unit  120  and another terminal communication unit  120  without regard to the direction of communication. 
         [0047]    Plural sensors  130  and actuators  131  may be connected to a terminal communication unit  120 . 
         [0048]    Operations of the elements of the distributed control system  10  will be described below with reference to the drawings. 
         [0049]    Processing steps performed by the distributed control system  10  will now be described with reference to  FIGS. 3 ,  4 ,  5 , and  6 . 
         [0050]      FIG. 3  is a flowchart illustrating the processing steps performed by the distributed control system  10  according to the present embodiment. 
         [0051]    First of all, the distributed control system  10  acquires transmission characteristics (S 300 ) by operations of the central communication unit  100  and the terminal communication units  120   a - 120   f,  the transmission characteristics being propagation characteristics of vibration of the object  20  from the actuators  131   a - 131   c  to the sensors  130   a - 130   c  connected to the terminal communication units  120   a - 120   f.    
         [0052]    A process performed in S 301  will now be described with reference to the flowchart of  FIG. 4 . 
         [0053]      FIG. 4  is a flowchart illustrating processing steps of acquiring transmission characteristics of the distributed control system  10  according to the present embodiment. 
         [0054]    First of all, the central communication unit  100 , by a process of the transmission characteristics acquisition section  102 , selects one of the terminal communication units  120   b,    120   d,    120   f  connected to the actuators  131   a - 131   c  (S 400 ). Here, it is assumed that the terminal communication unit  120   b  is selected. 
         [0055]    Next, the transmission characteristics acquisition section  102  of the central communication unit  100  transfers information about a method of vibrating the object  20  with an actuator  131  to the central communication control section  101 . 
         [0056]    This information is addressed to the selected terminal communication unit  120   b.    
         [0057]    The central communication control section  101  transmits the transferred information about the vibration method to the terminal communication unit  120   b  through the communication signal control section  110  and the network  150 . 
         [0058]    The terminal communication unit  120   b,  using the terminal communication control section  121 , receives the information about the vibration method, which is transmitted from the central communication unit  100 . The terminal communication control section  121  transfers the received information about the vibration method to the control information input/output setup section  123 . 
         [0059]    The control information input/output setup section  123  transfers the transferred information about the vibration method to the transmission characteristics computation section  125 . At the same time, the control information input/output setup section  123  changes its setup so that the terminal communication control section  121  and the transmission characteristics computation section  125  can transfer data. 
         [0060]    Further, the control information input/output setup section  123  changes its setup so that an output value of the actuator  131   a,  which is transferred from the transmission characteristics computation section  125 , is transferred to all the terminal communication units  120   a,    120   c,    120   e  connected to the sensors  130   a - 130   c,  respectively. 
         [0061]    The transmission characteristics computation section  125  drives the actuator  131   a  through the device control section  126  based on the transferred vibration method. At the same time, the transmission characteristics computation section  125  periodically transfers an output value for the actuator  131   a  to the control information input/output setup section  123  (S 401 ). 
         [0062]    As the vibration method, a random vibration method, a sweep vibration method, or other common vibration method may be used. 
         [0063]    It is preferred that, according to the sampling theorem, a frequency at which the output value for the actuator  131   a  is transferred to the control information input/output setup section  123  is at least two to four times the maximum frequency of the transmission characteristics to be acquired. 
         [0064]    Simultaneously with the process in S 401 , all the terminal communication units  120   a,    120   c,    120   e  connected to the sensors  130   a - 130   c  perform a process at the same time. First of all, the terminal communication units  120   a,    120   c ,  120   e  receives the output value of the actuator  131   a  transmitted from the terminal communication unit  120   b  with the terminal communication control section  121 . The terminal communication control section  121  transfers the received output value of the actuator  131   a  to the control information input/output setup section  123 . The control information input/output setup section  123  transfers the transferred output value of the actuator  131   a  to the transmission characteristics computation section  125 , and at the same time, changes its setup so that the terminal communication control section  121  and the transmission characteristics computation section  125  can transfer data. The transmission characteristics computation section  125  computes the transmission characteristics from the transferred output value of the actuator  131   a  and the input value of the sensors  130  that is acquired through the device control section  126  (S 402 ). 
         [0065]    After completion of all of the vibrating operation of the terminal communication unit  120   a  and the transmission characteristics computation process of the terminal communication units  120   b,    120   d,    120   f  in S 401  and S 402 , if any actuator  131  not vibrating is found (if S 403  is “YES”) in the terminal communication units  120   b,    120   d,    120   f  connected to the actuators  131   a - 131   c,  the transmission characteristics acquisition section  102  in the central communication unit  100  selects one terminal communication unit  120  that has not performed the vibrating operation from among the terminal communication unit  120   b,    120   d,    120   f  connected to the actuators  131   a - 131   c  (for example, the terminal communication unit  120   d  is selected) (S 404 ). Then, S 401  and S 402  are repeated. In S 403 , if all the actuators  131  are found to be vibrated (if S 403  is “NO”) among the terminal communication unit  120   b ,  120   d,    120   f  connected to the actuators  131   a - 131   c,  all the transmission characteristics from the actuators  131   a - 131   c , which are computed individually by the terminal communication units  120   b,    120   d,    120   f,  are transmitted from the transmission characteristics computation section  125  to the central communication unit  100  through the control information input/output setup section  123  (S 405 ). The transmission characteristics acquisition section  102  in the central communication unit  100  then receives all the transmission characteristics transmitted from the terminal communication units  120   b,    120   d,    120   f  through the central communication control section  101  and stores the received transmission characteristics in the transmission characteristics acquisition section  102 . 
         [0066]    Returning to the flowchart of  FIG. 3 , the processing steps performed by the distributed control system  10  will be described below beginning with S 301 . 
         [0067]    A display and input unit  160  of the distributed control system  10  displays the transmission characteristics stored in the transmission characteristics acquisition section  102  of the central communication unit  100 . Based on the transmission characteristics displayed on the display and input unit  160 , a user of the distributed control system  10  feeds the inputs from the sensors  130   a - 130   c  back to the outputs of the actuators  131   a - 131   c,  and designs a controller for an automatic control process to suppress vibration (S 301 ). 
         [0068]    The designed controller is stored in the communication control setup computation section  103  of the central communication unit  100  through the display and input unit  160 . 
         [0069]    Next, the central communication unit  100  performs automatic setup for an automatic control process on the terminal communication units  120   a - 120   f  and for communication control (S 302 ). 
         [0070]    A process performed in S 302  will be described with reference to the flowchart in  FIG. 5  and an exemplary setup shown in  FIG. 6 . 
         [0071]      FIG. 5  is a flowchart illustrating a setup sequence for an automatic control process and communication control that is performed by the distributed control system  10  according to the present embodiment. 
         [0072]    Based on the transmission characteristics displayed on the display and input unit  160 , a user of the distributed control system  10  sets an amplitude threshold value of the transmission characteristics used for automatic setup and a required performance as a control band for the automatic control process in the communication control setup computation section  103  through the display and input unit  160  (S 500 ). 
         [0073]    Next, the communication control setup computation section  103  of the central communication unit  100  extracts transmission characteristics not higher than the amplitude threshold value of the transmission characteristics from all the transmission characteristics stored in the communication control setup computation section  103  (S 501 ). 
         [0074]    Communication control setup information for inhibiting intercommunication during the execution of the automatic control process is transmitted through the central communication control section  101  to all the sets of the terminal communication units  120  that are connected to sensors  130  and actuators  131  related to the input/output of the transmission characteristics extracted in S 501 . The terminal communication units  120  transfer the communication control setup information, which is transmitted from the central communication unit  100 , to the control information input/output setup section  123  through the terminal communication control section  121 . The control information input/output setup section  123  performs setup for itself to inhibit communication to designated terminal communication units  120  during the execution of the automatic control process in accordance with the transferred communication control setup information (S 502 ). 
         [0075]    Next, the communication control setup computation section  103  of the central communication unit  100  selects a communication channel and a terminal communication unit  120  to perform the automatic control process so that the communication delay time is as small as possible with respect to the terminal communication units  120  permitted to establish communication during the process in S 502  (S 503 ). 
         [0076]    The process performed in S 503  will now be described in detail with reference to  FIG. 6 . 
         [0077]      FIG. 6  is a diagram illustrating an exemplary setup for the automatic control process and communication control of the distributed control system  10  according to the present embodiment. 
         [0078]    First of all, a group of two or more terminal communication units  120  that are capable of communicating with each other is regarded as a communication group. All the terminal communication units  120  are arranged in plural communication groups  600 . 
         [0079]    In the example of  FIG. 6 , the terminal communication units  120   a,    120   b,    120   c,    120   f  are arranged in a communication group  600   a,  and the terminal communication units  120   d,    120   e  are arranged in a communication group  600   b.    
         [0080]    Next, a terminal communication unit  120  that performs the automatic control process is selected so that the amount of communication data transmitted to the network  150  is minimized to reduce an increase in the communication delay time in the communication of the network  150 . 
         [0081]    More specifically, the total amount of data is calculated required for the input/output of all the sensors  130  and actuators  131  connected to each of all the terminal communication units  120  included in each communication group  600 . A terminal communication unit  120  handling the largest amount of data in each communication group  600  is then selected as the terminal communication unit  120  that performs the automatic control process. 
         [0082]    In the example of  FIG. 6 , the terminal communication unit  120   c  is selected as a terminal communication unit  120  to perform the automatic control process in the communication group  600   a , and the terminal communication unit  120   d  is selected as a terminal communication unit  120  to perform the automatic control process in the communication group  600   b.    
         [0083]    Next, a communication channel for each terminal communication unit  120  is set so that the communication delay time is as small as possible which would increase when the communication goes through the terminal communication units  120  as a repeater in the network  150 . 
         [0084]    More specifically, for each communication group  600  of terminal communication units  120 , a communication channel that minimizes the number of the terminal communication units  120  as a repeater in the communication channel is selected from all the communication channels between the terminal communication unit  120  performing the automatic control process and another terminal communication unit  120 . This selection process is performed for all the terminal communication units  120  included in all the communication groups  600 . 
         [0085]    In the example of  FIG. 6 , a communication channel indicated by a communication  601   a  is selected for the communication group  600   a,  and a communication channel indicated by a communication  601   b  is selected for the communication group  600   b.    
         [0086]    When the above process is performed, the communication control setup computation section  103  transmits a computation result about the automatic control process through the central communication control section  101  to a terminal communication unit  120  to perform the automatic control process which is selected from each communication group  600 . The terminal communication unit  120  to perform the automatic control process, using the control information input/output setup section  123 , receives the computation result about the automatic control process, which is transmitted from the central communication unit  100 , through the terminal communication control section  121 . The control information input/output setup section  123  performs setup for the execution of the automatic control process by storing the received computation result in the control computation section  124 . 
         [0087]    Further, in a similar way, the communication control setup computation section  103  transmits setup information about a communication channel selected for each terminal communication unit  120  to the corresponding terminal communication unit  120  through the central communication control section  101 . Each terminal communication unit  120 , using the communication channel setup section  122 , receives the setup information about a communication channel, which is transmitted from the central communication unit  100 , through the terminal communication control section  121 , and sets the communication channel by storing the received setup information in the communication channel setup section  122 . 
         [0088]    Returning to the flowchart of  FIG. 5 , a process from step S 504  will be described. 
         [0089]    The communication control setup computation section  103  calculates the communication delay time of each terminal communication unit  120  from the communication channel set for each terminal communication unit  120  and the amount of communication data of each terminal communication unit  120 . Further, the communication control setup computation section  103  calculates, for each communication group  600 , the maximum delay time, which is the maximum communication delay time in a communication group  600  of the terminal communication units  120 . 
         [0090]    The communication control setup computation section  103  calculates, for each communication group  600  of the terminal communication units  120 , the control band, which is the reciprocal of time that is approximately 8 to 10 times the maximum delay time (S 504 ). 
         [0091]    The value “approximately 8 to 10 times the maximum delay time” is a well-known multiplying factor used for calculating the control band. However, the value of the multiplying factor is not limited to the above-mentioned value. If, for example, an appropriate multiplying factor is experimentally predetermined, the predetermined factor maybe used to calculate the control band. 
         [0092]    Returning to the flowchart of  FIG. 3 , a process from step S 303  by the distributed control system  10  will be described. 
         [0093]    After the process of S 302 , if all the control bands calculated by the communication control setup computation section  103  satisfies the required performance of the control band set for itself (if S 303  is “YES”), the central communication unit  100  transmits a start command of the automatic control process to all the terminal communication units  120   a - 120   f  through the central communication control section  101 . All the terminal communication units  120   a - 120   f  then start the automatic control process in accordance with an operating method set for themselves (S 304 ). 
         [0094]    If all the control bands calculated by the communication control setup computation section  103  do not satisfy the required performance of the control band set for itself (if S 303  is “NO”), the central communication unit  100  presents an improvement method of the control band through the display and input unit  160  (S 305 ). 
         [0095]    In the process of S 305 , the communication control setup computation section  103  of the central communication unit  100  presents, as an improvement method of the control band, a communication path addition scheme for reducing terminal communication units  120  in a communication channel between a set of the terminal communication units  120  exhibiting the maximum delay time of a communication group  600  that does not satisfy the required performance, and also presents a change scheme for the layout of the terminal communication units  120  in the network  150 . 
         [0096]    Next, a user of the distributed control system  10  adds a communication path for the network  150 , changes the layout of the terminal communication units  120 , or resets the required performance of the control band (S 306 ) based on the method of improving the control band for the automatic control process, which is presented by the display and input unit  160 . Then, the automatic setup is repeated for the automatic control process on each terminal communication unit  120  and the communication control (S 302 ). 
         [0097]    As described above, the distributed control system  10  performs setup for itself automatically and executes the automatic control process. 
         [0098]      FIG. 7  shows a setup screen  700  of the display and input unit  160  according to the present embodiment. 
         [0099]    The setup screen  700  includes a communication performance setup/display section  701 , a communication control setup/display section  702 , a communication channel setup/display section  703 , and a control performance display section  704 . 
         [0100]    The communication performance setup/display section  701  displays the communication performance of each terminal communication unit  120  based on an automatically set communication control scheme when the distributed control system  10  performs the automatic control process. 
         [0101]    The communication control setup/display section  702  displays communication groups  600  set for individual terminal communication units  120 , communication channels for the individual terminal communication units  120 , and the terminal communication units  120  that perform the automatic control process when the distributed control system  10  performs the automatic control process. 
         [0102]    The communication channel setup/display section  703  sets an amplitude threshold value of the transmission characteristics, which is required for setting a communication channel for each terminal communication unit  120 , when the distributed control system  10  performs the automatic control process. Further, the communication channel setup/display section  703  displays the result of the automatic setup of the channel information about each terminal communication unit  120  based on the set threshold value. Here, it is assumed that a constant is used as the amplitude threshold value of the transmission characteristics , which is set by the communication channel setup/display section  703 . However, the amplitude threshold value of the transmission characteristics is not limited to a constant value and, for example, maybe a variable value depending on frequency. 
         [0103]    The control performance display section  704  displays the transmission characteristics between the actuators  131  and sensors  130  connected to the distributed control system  10 . At the same time, the control performance display section  704  shows magnitude relationship of the transmission characteristics compared to the amplitude threshold value of the transmission characteristics, which is set by the communication channel setup/display section  703 . 
         [0104]    In the present embodiment, even when the distributed control system.  10  is applied as a vibration damping instrument using many sensors  130  and many actuators  131 , it is possible to perform automatic setup for an automatic control process and for a communication channel used during the execution of a control process of each terminal communication unit  120 . Thus, adjustment and setup steps required for the distributed control system  10  can be reduced. Besides, it is easy to apply a vibration damping instrument later to the object  20  of which vibration is to be damped because the distributed control system  10  can be adjusted and set up to satisfy the required performance of the control. 
         [0105]    Further, in the present embodiment, communication is not performed between a set of terminal communication units  120  which are determined that communication is unnecessary based on the transmission characteristics acquired by the terminal communication units  120 . Therefore, communication paths of the network  150  through which communication is not performed can be reduced. Consequently, the distributed control system  10  according to the present embodiment can operate without sacrificing the functionality and performance even if such communication paths are reduced. 
       LIST OF REFERENCE CHARACTERS 
       [0106]      10  . . . Distributed control system 
         [0107]      20  . . . Object of which vibration is to be damped 
         [0108]      100  . . . Central communication unit 
         [0109]      101  . . . Central communication control section 
         [0110]      102  . . . Transmission characteristics acquisition section 
         [0111]      103  . . . Communication control setup computation section 
         [0112]      110  . . . Communication signal control section 
         [0113]      120 ,  120   a - 120   f  . . . Terminal communication unit 
         [0114]      121  . . . Terminal communication control section 
         [0115]      122  . . . Communication channel setup section 
         [0116]      123  . . . Control information input/output setup section 
         [0117]      124  . . . Control computation section 
         [0118]      125  . . . Transmission characteristics computation section 
         [0119]      126  . . . Device control section 
         [0120]      130 ,  130   a - 130   c  . . . Sensor 
         [0121]      131 ,  131   a - 130   c  . . . Actuator 
         [0122]      140  . . . Communication port 
         [0123]      150  . . . Network 
         [0124]      160  . . . Display and input unit 
         [0125]      600 ,  600   a,    600   b  . . . Communication group 
         [0126]      601 ,  601   a,    601   b  . . . Communication 
         [0127]      700  . . . Setup screen 
         [0128]      701  . . . Communication performance setup/display section 
         [0129]      702  . . . Communication control setup/display section 
         [0130]      703  . . . Communication channel setup/display section 
         [0131]      704  . . . Control performance display section