Modeling and Control of Thermal Printing

In this paper, we present the development of an optimal controller for thermal printheads. A first-order linear system and a nonlinear output mapping with stochastic noise is proposed as a model of the printing dynamics. The model parameters are identified and an optimal control problem is formulated to determine the printhead input. The control algorithm is successfully tested on a standard thermal printer. A sensitivity analysis is performed by simulations and experiments to analyze the printing quality on varying setups with different printheads, printing media and ribbons. A tuning strategy is derived to adapt to changing setups without having to recompute an optimization problem. The performance of the control system for a wide range of operating systems is observed in experiments. Comparing the proposed controller to a current control implementation shows a significant quality gain in barcode readability (ISO/IEC 15416).