Electric micromotor dynamics

The dynamometry technique uses a strobe flash which is triggered from a phase excitation signal after a known time delay. This acts essentially as a video shutter allowing the position of the rotor as a function of the time delay to be recorded and measured. A dynamic model is developed that includes an electrostatic drive term, a velocity-dependent viscous drag term, and a Coulomb friction term that is dependent on the square of the drive voltage and the sign of the velocity. From the position-versus-time data, coefficients for this model are estimated using nonlinear least square error estimation. It is shown that both viscous drag and Coulomb friction terms are required if the model is to closely fit all the experimental data. The motor dynamics are shown to have a weak, if any, dependence on the rotor-bushing apparent area of contact