Identification and analysis of nonlinear dynamics of inertial actuators

This paper presents an experimental study of the nonlinear dynamics of electrodynamic proof mass actuators. When inertial actuators are used in velocity feedback controllers, their nonlinear dynamics can affect the stability margin of the feedback loop. Thus, it is crucial to identify the nonlinearity sources and to build reliable models that can be implemented in the stability analysis. Firstly, the underlying linear model parameters of an inertial actuator are identified for small excitation signals. The inductance losses at high frequencies due to eddy currents have also been included in the electrical impedance model. Secondly, the nonlinear model of the inertial actuator is determined using the detection, characterisation and identification process. Finally, a numerical analysis is carried out to highlight the implications of nonlinear dynamics of inertial actuators. The proposed methodology is applied to several electromagnetic proof mass actuators, including when the proof mass is not accessible to be directly instrumented.