Design of an l/sub 1/ optimal controller for a hydrogen reformer plant

The design of an l/sub 1/ optimal controller for a hydrogen reformer is presented. The objective of the hydrogen reformer process is to produce hydrogen by catalysis from desulphurized hydrocarbons, mixed with superheated steam. The controller to be designed is the fuel flow controller, whose main objective is to maintain the reformer temperature constant despite important variations in the temperature of the input steam. The design approach used here involves solving a modified mixed sensitivity l/sub 1/ optimal control problem, with weights determined by the disturbance information and the performance specifications. These l/sub 1/-optimal controllers can often handle a wider set of specifications than other robust control techniques. With the l/sub 1/-optimal controller the output temperature variation can be reduced to +1.9/spl deg/C, compared with /spl plusmn/3.1/spl deg/C using the PID controller installed in the plant.