The analysis and design of low velocity estimation based on observer

Low velocity servo system needs precision velocity estimation. An observer for low velocity estimation was proposed in this paper. First, the source of low velocity estimation errors and the shortcomings of the single period difference were analyzed. The relationship between the estimation accuracy and estimator´s frequency characteristics was concluded. Then, the structure of the observer was proposed. Frequency characteristics were used to design the compensator which can stabilize the observer. The stability of the observer was also discussed. At last, the observer´s estimation accuracy was evaluated through a quantitative comparison. The results of simulation and experiment have shown that the quantized error in velocity estimation decreases dramatically when a velocity observer is used. Compared with some commonly-used estimators, the phase lag accompanying the observer is much less.