In this paper a modelling of a hybrid actuator is proposed. The hybrid actuator consists of a piezo-mechanical structure and a hydraulic ratio displacement. Particular attention is paid to a liquid spring model of the displacement ratio which represents the hydraulic part of the mechanism. Moreover, a repetitive control is proposed to track a periodic signal together with a proportional derivative (PD) one. Repetitive control is a control method, which is associated with periodic input variables and it is successfully used together with a supplementary control structure. The supplementary control structure must be devoted to the stabilisation of the control loop. Simulations and measured results of the closed loop carried out the suitability of the control approach.