An energy saving, factory-validated disturbance decoupling control design for extrusion processes

This paper is focused on the design and factory testing of a disturbance decoupling control (DDC) approach for hose extrusion processes. A unique dynamic DDC strategy, based on the active disturbance rejection control (ADRC) framework, is designed and implemented in programmable logic control (PLC) code for temperature regulation in the volumetric flow of a polymer single-screw extruder. With the DDC method, it is shown that a largely unknown square multivariable system is readily decoupled by actively estimating and rejecting the effects of both the internal plant dynamics and external disturbances. The proposed DDC approach requires very little information on plant model and has the inherent disturbance rejection ability, and it proves to be a great fit for the highly nonlinear and multivariable extrusion processes. Recently, the DDC design strategy has been put under rigorous test at Parker Hannifin Parflex hose extrusion plant. Across multiple production lines for over eight months, the product performance capability index (Cpk) was improved by 30 percent and energy consumption is reduced over 50 percent. The production line data demonstrates that ADRC is a transformative control technology with great potentials in streamline factory operations, saving energy and improving quality, all at the same time.