DC and Quasi-DC Acceleration Observation for Servosystems with Piezoelectric Accelerometers

This paper presents two observers, which combine a piezoelectric accelerometer with a positional sensor that commonly exists in a servo system. The piezoelectric accelerometers have wide measurement bandwidth but cannot measure an acceleration's dc and quasi-dc components. The proposed observers can estimate dc and quasi-dc components of an acceleration, avoiding the piezoelectric accelerometers' drawback. In contrast to commonly used capacitive accelerometers, the proposed observers can produce wide dynamic bandwidth owing to the use of a piezoelectric accelerometer. Compared with existing acceleration observers, the proposed observers do not require a plant's model and are thus completely insensitive to model uncertainties. Moreover, the proposed observers do not directly differentiate the positional signal twice with respect to time and are thus more immune to positional sensor noise. The proposed observers are experimentally applied to a linear motion stage to investigate applicability and feasibility of the proposed schemes.