Relaxed Lyapunov Criteria for Robust Global Stabilization of Nonlinear   Systems
  The notion of the relaxed Robust Control Lyapunov Function (relaxed RCLF) is introduced and is exploited for the design of robust feedback stabilizers for nonlinear systems. Particularly, it is shown for systems with input constraints that relaxed RCLFs can be easily obtained, while RCLFs are not available. Moreover, it is shown that the use of relaxed RCLFs usually results to different feedback designs from the ones obtained by the use of the standard RCLF methodology. Using the relaxed RCLFs feedback design methodology, a simple controller that guarantees robust global stabilization of a perturbed chemostat model is provided. 
Iasson Karafyllis, Costas Kravaris and Nicolas Kalogerakis