Fig. 2
This “virtual subsystem” is regarded as a “virtual sensor” in the marine low-temperature alkaline protease MP fermentation process. It can be used as a dynamic compensator in series with the “virtual subsystem”, a unit compound system can be formed. Its the input and output present an identity mapping relationship, that is, the output of the composite system can completely reproduce the input of the original “virtual sensor”, and then the soft-sensing of x1, x2, x3 can be realized