Model-Based Feedback Control of a kHz-Excited Atmospheric Pressure Plasma Jet

Atmospheric pressure plasma jets (APPJs) have widespread use in materials processing and biomedical applications. Safe and effective operation of hand-held APPJs is, however, highly sensitive to the intrinsic variability of plasma characteristics as well as exogenous disturbances such as variations in the separation distance between the device tip and target surface. This paper investigates feedback control of the thermal effect and intensity of a kHz-excited APPJ in helium using a proportional-integral control strategy and a model predictive control (MPC) strategy. A data-driven model of the APPJ, developed for a linear operating range using the subspace identification method, is utilized in the design of both control strategies. Realtime control experiments reveal that feedback control is crucial for effective operation of the APPJ in the presence of step disturbances in the device tip-to-surface separation distance. It is observed that the MPC strategy can more effectively regulate the multivariable dynamics of the APPJ for effective setpoint tracking and constraint handling in the face of disturbances.