Delay compensated control of the Stefan problem and robustness to delay mismatch

• Published in: International journal of robust and nonlinear control Vol. 30; no. 6; pp. 2304 - 2334
• Main Authors: Koga, Shumon, Bresch‐Pietri, Delphine, Krstic, Miroslav
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.04.2020; Wiley
• Subjects: Actuators; Automatic; backstepping; Control stability; Controllers; Delay; distributed parameter systems; Engineering Sciences; Interface stability; nonlinear stabilization; Ordinary differential equations; Partial differential equations; Robustness; Solid phases; Stefan problem; Temperature profiles; time delay systems; nonlinear stabilization; backstepping; distributed parameter systems; Stefan problem; time delay systems
• ISSN: 1049-8923; 1099-1239
• DOI: 10.1002/rnc.4909

Summary This paper presents a control design for the one‐phase Stefan problem under actuator delay via a backstepping method. The Stefan problem represents a liquid‐solid phase change phenomenon which describes the time evolution of a material's temperature profile and the interface position. The actuator delay is modeled by a first‐order hyperbolic partial differential equation (PDE), resulting in a cascaded transport‐diffusion PDE system defined on a time‐varying spatial domain described by an ordinary differential equation (ODE). Two nonlinear backstepping transformations are utilized for the control design. The setpoint restriction is given to guarantee a physical constraint on the proposed controller for the melting process. This constraint ensures the exponential convergence of the moving interface to a setpoint and the exponential stability of the temperature equilibrium profile and the delayed controller in the ℋ1 norm. Furthermore, robustness analysis with respect to the delay mismatch between the plant and the controller is studied, which provides analogous results to the exact compensation by restricting the control gain.