Other than the conventional soft sensor of output correction

the primary variables of soft sensor in FCCU riser reactor are completely unmeasurable in real time

and they can only be corrected on-line by secondary variables

so the state observer was used to build soft sensor.FCCU is an index-one nonlinear singular system

so an index-one nonlinear singular state observer was designed for soft sensor to estimate the unmeasurable variables on-line

including product yields and catalyst circulation rate of FCCU.For index-one nonlinear singular system

if the linear parameter-varying singular system from local linearization at current operating point was detectable

a nonlinear singular state observer could run in a wide range

and its feedback gain matrix can be obtained on-line by pole assignment of the linearized system.The existence of nonlinear singular state observer can ensure that the estimated values of the primary variables will converge to their ideal values.Simulation showed that even if the catalyst circulation rate was unknown

when it was augmented as state variable and the temperature of FCCU riser outlet as secondary variable was used for output correction

a soft sensor based on nonlinear singular state observer could be established to estimate the unmeasurable variables

such as product yields and catalyst circulation rate on-line.The estimated values of the unmeasurable variables converged to the ideal values and the proposed observer had good dynamic performance.