Hirokazu Tajima

Speed sensorless field orientation control of the induction machine

A speed estimation method is proposed for an induction machine and its application to the flux observer based field orientation (FOFO) control system is discussed. The motor speed is estimated based on the difference between two flux estimators. Its convergence performance is estimated and the authors propose an assignment method. The speed estimator is applied to the FOFO controller. Experiments show that the speed sensorless FOFO operates with enough stability and has a robustness to rotor resistance variation.<<ETX>>

Consideration about problems and solutions of speed estimation method and parameter tuning for speed-sensorless vector control of induction motor drives

A classical, model-based, speed sensorless field oriented control method for general purpose induction machine is considered. Improved versions of both speed and stator resistance on-line estimators are presented with the aim of extending control capabilities down to zero speed. Only electrical stator measurements are needed, making the method suitable for general purpose inverter applications. Online rotor resistance tuning is also included to fully compensate for thermal drift. Performance of the proposed drive is investigated by simulation and experiments.

A gravity survey on Volcano Huzi, Japan by means of a Worden gravimeter

SummaryObservations and reductions of the gravimeter survey on Volcano Huzi are fully described. The survey was accompanied by various inevitable difficulties but the accuracy of calculating the Bouguer anomalies is kept high enough to bear volcanological discussion. The results are rather suggestive to the theory of caldera-formation. Comparison with the gravity anomaly on the volcanic islands in the middle of the ocean is also made.