Network control system, process management method in this system, and recording medium on which a process management program is recorded

A process management method for managing various processes in a controlled object, comprising the steps of:

• calculating a control variable for execution of one of the processes in the controlled object in accordance with a control reference value and an actual process variable that was detected previously in the controlled object;
• generating a control signal including the calculated control variable and process variable detection time that has been transmitted from the controlled object;
• transmitting the control signal to the controlled object via an asynchronous network;
• measuring reception time of the control signal in the controlled object;
• calculating a transmission delay that is a difference between the control signal reception time and the process variable detection time;
• correcting the control variable included in the control signal in accordance with the calculated transmission delay;
• driving a driver in accordance with the corrected control variable, to thereby execute the process;
• detecting a process variable of the process being executed and measuring detection time thereof;
• and
• generating a process signal including the detected process variable and the measured process variable detection time, and transmitting the process signal to the control apparatus via said network.

A recording medium on which a process management program for managing various processes in a controlled object of an network type control system is recorded, the process management program being for causing a computer to execute the steps of:

• calculating a control variable for execution of one of the processes in the controlled object in accordance with a control reference value and an actual process variable that was detected previously in the controlled object;
• generating a control signal including the calculated control variable and process variable detection time that has been transmitted from the controlled object;
• transmitting the control signal to the controlled object via an asynchronous network;
• measuring reception time of the control signal in the controlled object;
• calculating a transmission delay that is a difference between the control signal reception time and the process variable detection time;
• correcting the control variable included in the control signal in accordance with the calculated transmission delay;
• driving a driver in accordance with the corrected control variable, to thereby execute the process;
• detecting a process variable of the process being executed and measuring detection time thereof;
• and
• generating a process signal including the detected process variable and the measured process variable detection time, and transmitting the process signal to the control apparatus via the asynchronous network.

A network control system in which a controlled object and a control apparatus are connected to each other bidirectionally, wherein:

• the controlled object comprises a process signal transmitting device, a control signal receiving device, and a timer for measuring transmission time and reception time;
• the process signal transmitting device has a function of transmitting a process variable observation value and process variable transmission time information together;
• the control apparatus has a function of transmitting process signal transmission time information and corresponding control signal together;
• and
• the control signal receiving device has means for calculating a transmission delay from the process signal transmission time and control signal reception time and processing the control signal based on the calculated transmission delay.

A network control system for transmitting signal between a control apparatus and a controlled object, comprising:

• a process signal outputting device connected to said controlled object, for outputting an observed process variable and an output time information;
• a control signal outputting device connected to said control apparatus, for outputting a control variable taking account of the observed process variable and the output time information;
• and,
• a process signal inputting device connected to said controlled object, for calculating delay time of the output time information from said control signal outputting device to said process signal inputting device, and re-calculating the process variable taking account of the calculating delay time.