Development of feedback control systems for an oscillating plasma jet

The dependencies of fluctuating characteristics of a plasma jet such as gas temperature, radiation intensity, electron temperature, electron density, jet length and jet width on the applied magnetic flux density and oscillation frequency are experimentally clarified, when the oscillating flow is injected into a non-equilibrium plasma jet as a disturbance. It is found that the radiation intensity is selected as an adjustable controlled variable, and the magnetic flux density as a manipulated variable, respectively, for feedback control system. Because all the fluctuating characteristics are suppressed effectively by applying magnetic field and the radiation intensity especially has a rapid response to the applied magnetic field. Finally, feedback control system is successfully constructed for an oscillating plasma jet to increase process efficiency in a stable plasma spraying for example. Constant value control of radiation intensity fluctuation and jet width fluctuation are achieved by using PID control method to stabilize an oscillating plasma jet. (C) 2004 Elsevier Ltd. All rights reserved.