Identi cation of a Compact Disc Pick { up Mechanism

This paper discusses the control relevant parametric identi cation of a servo system present in a Compact Disc player. In this application an approximate closed loop identi cation problem is solved in order to come up with a linear multivariable discrete time model, suitable for control design. This identi cation problem is handled by a recently introduced two stage method. It yields an explicit and tunable expression for the bias distribution of the model being estimated, clearly showing the dynamics of the closed loop system in the (asymptotic) approximation criterion. This result will be exploited to identify the model in a control relevant way by additional data ltering. The recently introduced method in [20] for model uncertainty quanti cation is used to construct an upper bound for the corresponding model error.