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Control system design for plasma power generator




Sankaran, Aishwarya, author
Young, Peter M., advisor
Chong, Edwin, committee member
Anderson, Charles, committee member

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The purpose of this research is to develop advanced control strategies for precise control over power delivery to nonlinear plasma loads at high frequency. A high-fidelity MATLAB/Simulink simulation model was provided by Advanced Energy Industries, Inc (AE) and the data from this model was considered as the actual model under consideration. The research work requires computing a mathematical model of the plasma power generator system, analyzing and synthesizing robust controllers for individual operating points, and then developing a control system that covers the entire the grid of operating points. The modeling process involves developing computationally simple near-linear models representing relevant frequencies and operating points for the system consisting of nonlinear plasma load, RF Power Amplifier, and a Match Network. To characterize the (steady-state) mapping from power setpoint to delivered power the steady-state gains of the system are taken under consideration. Linear and nonlinear system identification procedures are used to adequately capture both the nonlinear steady-state gains and the linear dynamic model response. These near-linear or linear models with uncertainty description to characterize the robustness requirements are utilized in the second stage to develop a grid of robust controller designed at linear operating points. The controller from -synthesis design process optimizes robust performance for allowable perturbations as large as possible. It does all this while guaranteeing closed-loop stability for all allowable perturbations. The final stage of the research focuses on developing Linear Parameter Varying (LPV) controllers with non-linear offset. This single controller covers the entire operating range, including the case that the desired signals to track may vary over wide regions of the operating envelope. LPV controllers allows actual power to track the changing setpoint in a smooth manner over the entire operating range.


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