Optimum Supervisory Control of Paper Basis Weight and Machine Speed by Statistical Methods

A method for the control of basis weight by supervisory optimization is worked out. The objective is to determine the optimum supervisory machine speed and basis weight setpoint adjustments to maximize the profitability of production subject to the constraints of plant operation. The cost function consists of production cost and the loss due to rejects. An optimization scheme is worked out to calculate an optimization policy. Furthermore, the machine speed versus profit relations are developed to arrive at a supervisory machine speed which provides the globally minimized cost (maximized profit). The sampled measurements are processed to determine the variance and expected values of process variables. The expected values are used by the optimization system to determine the set point adjustments (corrections) by using the production and reject cost data. The supervisory machine speed is determined based on the optimum cost values of operation at various speeds, to reach a globally minimum cost value. The implementation by distributed control systems are described including the benefits of such a system.