A robust multiple PI controller for the air distribution into an arc heater

This paper deals with the problem of controlling both the air total mass flow-rate and its distribution in a 70 MW electric arc heater by means of a five way air supply system. Firstly a description of the detailed dynamic model of the pneumatic process, obtained in the lumped parameter domain, is provided, then the proposed control strategy is described. In order to guarantee the desired distribution of the total air supplied along the arc heater, a multiple PI control technique is proposed to command five partitioning valves. A physical reduction of the process model allows us to reduce the control problem to the synthesis of five standard PI controllers for Linear Parameter Varying first order systems. A robust synthesis of the controller gains which makes use of the concept of quadratic stability with a fixed decay rate and with an H_∞ norm bound is proposed to cope with uncertainties, nonlinearities and disturbances. Numerical simulations are carried out to show the effectiveness of the control technique.