Disturbance modeling in a tube glass production process

The modeling of disturbances in a tube glass production process is considered. After substantial disturbance reduction due to the application of process control, repetitive disturbances became visible in the outputs limiting the quality of the product measures: wall thickness and diameter. These output disturbances are caused by a discontinuous flow of the material inside the melting vessel as a result of bridge forming. A disturbance model has been developed consisting of a nonlinear and a linear part describing the behaviour of the disturbances inside and outside the melting vessel respectively. The nonlinear part models the relation between the pressures at the top of the furnace vessel and at the spout. The linear part describes the transfer between the spout pressure and the product measures which transfer has been identified by output-error minimization. Next, the complete model has been used to design a feedforward controller. The variances of the product measures using this approach can be reduced to less than 50% in simulations.