Soft Sensor Modeling Method Based on SPA-GWO-SVR for Marine Protease Fermentation Process

Table 2

Selection of auxiliary variables based on GRA and SPA algorithm.

Key variables	Variable selection method	Number of variables	Auxiliary variables
Cell concentration (X)	Full	11	t, p, DO, pH, l, r, , μ, η, c1, c2
	GRA	8	p, DO, pH, , μ, η, c1, c2
	SPA	6	DO, pH, , μ, η, c1
Matrix concentration (S)	Full	11	t, p, DO, pH, l, r, , μ, η, c1, c2
	GRA	7	p, DO, pH, μ, η, c1, c2
	SPA	5	DO, pH, μ, η, c1
Enzyme activity (P)	Full	11	t, p, DO, pH, l, r, , μ, η, c1, c2
	GRA	8	DO, pH, l, , μ, η, c1, c2
	SPA	6	DO, pH, l, μ, η, c1