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Performance analysis of discrete-time disturbance observer for second-order systems

The disturbance observer (DOB) has been widely used in high speed and high precision motion control applications. Though most of DOBs have been implemented as the discrete-time form in digital devices, we are still short of the researches on discrete-time DOB in spite of rich references on continuous-time DOB. In this paper, we will discuss the disturbance rejection property and measurement noise effect of a discrete-time DOB. Especially, we focus on revealing the role of sampling time in designing the discrete-time DOB for second order systems. Finally, we show the validity of analysis through simulations and experiments for optical disk drive systems.