Control system and control device

A control system comprising:

• a remote device;
• and a control device that repeatedly performs a series of pieces of processing comprising input/output (I/O) refresh processing and program execution processing in a first control period having a first length, the control device exchanging data with the remove device over a network, the control device comprising:
• a processor configured with a program to perform operations comprising:
• obtaining a first sample value group that is collected by repeatedly performing the I/O refresh processing in the first control period;
• obtaining a second sample value group that is collected in response to the I/O refresh processing being repeatedly performed in a second control period having a second length longer than the first length of the first control period;
• determining whether a first frequency component comprised in the first sample value group and a second frequency component comprised in the second sample value group comprise a degree of redundancy with each other that is greater than or equal to a predetermined value;
• and
• changing the first length of the first control period to the second length of the second control period in response to the first frequency component and the second frequency component comprising the degree of redundancy with each other that is greater than or equal to the predetermined value, wherein
• the processor is configured to perform the series of pieces of processing comprising the input/output (I/O) refresh processing and the program execution processing in the changed first control period in response to the change in the first length of the first control period to the second length.