Compensation of variable fractional delays in repetitive controllers Conference Paper uri icon

abstract

  • Repetitive schemes are composed by the interconnection of delay lines. These schemes are usually implemented in a digital way, where delay lines are replaced by discrete delays. Each discrete delay is obtained as the ratio between the required delay time in continuous time and the sampling period. A problem arises whenever the delay time of the controller is not an integer multiple of the sampling period. This is referred in the literature as the fractional delay (FD) issue. The delay time is, in general, a function of the fundamental frequency of the signals to be processed. There are, however, applications where the fundamental frequency varies on time, which entails variable FD (VFD). This work presents a relatively simple solution to implement repetitive schemes subject to a VFD issue. The solution consists in the introduction, on each delay line of the repetitive scheme, of an additional filter structure, called Farrow structure, aimed to compensate such a VFD issue. In particular, the present paper focuses on the 6fc ± 1 repetitive scheme, though similar approach can be applied to other repetitive schemes. Numerical results are presented to confirm the benefits of the proposed modification, experiments are in process and will be presented in the final version of the paper. © 2014 IEEE.

publication date

  • 2014-01-01