An Improved ADRC Parameters Self-Tuning Controller for Multi-Color Register System in Unit-Type Flexographic Printing Machines

A self-tuning control strategy for Active Disturbance Rejection Control (ADRC) parameters based on a Radial Basis Function (RBF) neural network is proposed to improve the control accuracy of the roll-to-roll flexographic printing multi-color register system for its multi-input–multi-output and multi-span coupling characteristics. Firstly, according to the actual physical structure of flexographic printing equipment and the multi-physical coupling interface between adjacent spans, a mathematical model of the register system is established, and the multi-span coupling model is decoupled. Then, the ADRC decoupling controller is designed to estimate the disturbance and control the coupling model, and the RBF neural network is used to adjust the parameters of the decoupling controller in real time. Finally, the robustness, system decoupling, and anti-disturbance performance of the designed controller are verified under simulated steady speed and acceleration conditions. The simulation results show that the designed controller has better control performance than the conventional Proportional-Integral-Derivative (PID) and decoupled PID controllers. In steady state and accelerated simulations of PET/BOPP materials, respectively, the error peak is reduced by 86.7% and is controlled within ±10 μm, which satisfies the high-accuracy control requirements of the register system.