Control system, control method for control system, and controller

A control method for a control system including:

• an IO node to which a field instrument configured to acquire measurement data is connected;
• multiple controllers configured to perform calculation based on the measurement data acquired by the field instrument;
• and
• a cache server,
• the control method comprising:
• at each of control timings that are regular periods of time predetermined at regular intervals, determining, by each of the multiple controllers, whether the measurement data acquired by the field instrument is being held;
• when the cache server is not holding the measurement data, acquiring, by each of the multiple controllers from the IO node, the measurement data acquired by the field instrument connected to the IO node;
• when the cache server is holding the measurement data, acquiring, by each of the multiple controllers from the cache server, the measurement data acquired by the field instrument;
• and
• performing, by each of the multiple controllers, predetermined calculation based on the measurement data received from the IO node or the cache server.

A controller configured to be communicable with a cache server, and an IO node to which a field instrument configured to acquire measurement data is connected, the controller configured to perform calculation based on the measurement data acquired by the field instrument, the controller comprising a controller configured to:

• determining, at each of control timings that are regular periods of time predetermined at regular intervals, whether the measurement data acquired by the field instrument is being held;
• when the cache server is not holding the measurement data, acquiring, from the IO node, the measurement data acquired by the field instrument connected to the IO node;
• when the cache server is holding the measurement data, acquiring, from the cache server, the measurement data acquired by the field instrument;
• and
• performing predetermined calculation based on the measurement data received from the IO node or the cache server.