This paper aims to identify friction-impeded servo-mechanical systems using a time-domain based approach with a multiple-relay feedback apparatus. By converting the closed-loop system into a triple-relay feedback system, switching conditions of a stable limit cycle are obtained. Following by this, stable oscillations are excited by choosing suitable relay gains. Hence, the level of Coulomb friction and other linear parameters are identified by numerically solving a set of equations with data from just a single limit cycle experiment. This method is also robust to measurement noise. Simulation and real-time experiments on a DC motor show the practical appeal of the proposed method.
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