Combining ILC and repetitive control to handle repeating, event-triggered disturbances in precision inkjet printing

Learning and repetitive control are powerful instruments in handling recurring disturbances. Repetitive control properly handles constantly repeating variations, while iterative learning control is well-equipped when it comes to handling event triggered deviations. Neither controller is well equipped to adequately deal with repetitive disturbances, which are only present during limited, but varying, periods of time. These are often seen in precision handling systems such as production inkjet printers. This paper combines ILC and RC using a structure which originated in multi-period repetitive control. It is shown that this enables full suppression of the repeating event-triggered disturbances. The approach is successfully demonstrated in an illustrative simulation, as well as by using experimental data from a precision inkjet printing setup.