A method for characterization of the amplitude (ΔS) of a play (S(t)) of an electromechanical actuator , the electromechanical actuator comprising an electric motor and a mobile element capable of being set in motion by the motor, said play (S) being defined as a distance or an angle (m, rad) which either of the motor and of the mobile element has to travel before it can transmit a movement or a stress to the other, the actuator comprising an upstream sensor suitable for measuring a position of the motor (X1(t)) and a downstream sensor suitable for measuring a position of the mobile element (X2(t)), as well as a force sensor suitable for measuring a load applied to the mobile element (Fl(t)), the method comprising steps of: - (E1) measuring the position of the motor (X1(t)), the position of the mobile element (X2(t)) and the load applied (Fl(t)) to the mobile element by means of the three sensors, - (E2) from the computer modelling of the actuator and the measured position of the motor (X1(t)), the measured position of the mobile element (X2(t)) and the load applied (Fl(t)) to the measured mobile element, estimation of a value of mechanical play (S(t)) by means of a state observer by considering the play (S(t)) as a component of the state, the play S(t) being modelled in the form: S t . = 0 + b t where S is the play, b is random white noise of known spectral density, and t is the time, one of the components of the state of the state observer being a deviation δX(t) between the measured position of the mobile element X2(t) and the measured position of the motor X1(t), such that the state vector x is expressed in the following form: x = δX δX . S T where δ ⁢ X = X 2 − X 1 , and the magnitude of measured output of the state observer is expressed in the following form: y = δX T - (E3) determination of the amplitude of the play (ΔS) from a set of values of the dynamic variable obtained at the preceding step for different instants (t) . - (E1) measuring the position of the motor (X1(t)), the position of the mobile element (X2(t)) and the load applied (Fl(t)) to the mobile element by means of the three sensors, - (E2) from the computer modelling of the actuator and the measured position of the motor (X1(t)), the measured position of the mobile element (X2(t)) and the load applied (Fl(t)) to the measured mobile element, estimation of a value of mechanical play (S(t)) by means of a state observer by considering the play (S(t)) as a component of the state, the play S(t) being modelled in the form: S t . = 0 + b t where S is the play, b is random white noise of known spectral density, and t is the time, one of the components of the state of the state observer being a deviation δX(t) between the measured position of the mobile element X2(t) and the measured position of the motor X1(t), such that the state vector x is expressed in the following form: x = δX δX . S T where δ ⁢ X = X 2 − X 1 , and the magnitude of measured output of the state observer is expressed in the following form: y = δX T - (E3) determination of the amplitude of the play (ΔS) from a set of values of the dynamic variable obtained at the preceding step for different instants (t) . <EOS>