1. An irradiation apparatus for irradiating by scanning a target volume according to a predetermined dose profile with a scanning beam of charged particles forming an irradiation spot on said target volume, said apparatus comprising: a beam generating device, a reference generator for computing, from said predetermined dose profile, through a dynamic inverse control strategy, the time evolution of commanded variables, these variables being the beam current I(t), the spot position settings x(t),y(t) and the scanning speed settings v x (t), v y (t), a monitor device having means for detecting at each time (t), the actual spot position as a measured position defined by the values x m (t),y m (t) on the target volume, wherein said irradiation apparatus further comprises means for determining the differences e x (t), e y (t) between the measured values x m (t), y m (t) and the spot position settings x(t) and y(t), and means for applying a correction to the scanning speed settings v x (t) and v y (t) depending on said differences e x (t), e y (t).