Digital repetitive control is a technique which al-
lows to track periodic references and/or reject peri-
odic disturbances. Repetitive controllers are usually de-
signed assuming a fixed frequency for the signals to be
tracked/rejected, its main drawback being a dramatic per-
formance decay when this frequency varies. A usual ap-
proach to overcome the problem consists of an adap-
tive change of the sampling time according to the refer-
ence/disturbance period variation. However, this sam-
pling period adaptation implies parametric changes af-
fecting the closed-loop system behavior, that may compro-
mise the system stability. This article presents a design
strategy which allows to compensate for the parametric
changes caused by sampling period adjustment. Stabil-
ity of the digital repetitive controller working under time-
varying sampling period is analyzed. Theoretical devel-
opments are illustrated with experimental results.Peer ReviewedPostprint (published version