Periodic variations are encountered in many real systems, which can exist in the system parameters, as<br>a disturbance or as the tracking objective. However, there exist a great number of situations where the<br>periodicity is not known in advance. Hence, how to compensate for the effects of time-varying parameters<br>with unknown periodicity remains a challenge for the controller design. In this paper, we proposed a switching<br>periodic adaptive control approach for continuous-time no
