Circadian phase control using observer-based back-stepping design

Circadian rhythms exist in most of living species, and control their daily biological activities. Disruption of these rhythms can cause circadian disorders or phase shifts. This paper deals with phase recovery of circadian rhythms. The phase restoration is carried out by synchronization of estimated trajectories of unknown state variables of a controlled system with trajectories of a reference system via back-stepping. The unknown state variables are estimated by using recently developed one-sided Lipschitz observer. Both reference and controlled systems are based on a 3rd order model of Neurospora circadian rhythms. Several simulation studies are carried out to verify the operation of proposed synchronization scheme with results shown in this paper.