The invention relates to an unbalance dynamic load generator comprising at least one pair of eccentric rotating masses (M) which are symmetric with respect to a plane and whose motion is controlled by at least one control signal generated by a control module as a function of a preset signal (Fd(t)) having a given frequency. It is characterized in that, for at least one of the masses, it comprises a reference angular position sensor (C) delivering a position signal (SP) representing the passing of the said rotating mass (M) through a reference angular position and a control circuit comprising a calculation circuit (DSP) for calculating the periodicity of the rotation of the said mass from the successive position signals delivered by the position sensor (C) and for generating the said control signal (CS) as a function of the difference between the measured periodicity and the periodicity of the preset signal.