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This paper deals with the speed and position estimation for synchronous reluctance motors (SyRMs) and interior permanent-magnet synchronous motors (IPMs). A unified design and analysis framework for a class of back electromotive force-based observers is developed and the links between apparently different estimation methods are brought out. State observers equipped with a speed-adaptation law are shown to be mathematically equivalent to voltage-model-based flux observers equipped with a position-tracking loop. The error signal driving the adaptation law or the tracking loop is presented in a generalized form. Using the framework, a stabilizing gain design is reviewed and detailed design guidelines are given. Selected observer designs are experimentally evaluated using a 6.7-kW SyRM drive and a 2.2-kW IPM drive. [ABSTRACT FROM AUTHOR]

Back-electromotive force (back-EMF) self-sensing is commonly used in induction machine (IM) drive systems for its maintenance cost and safety considerations. In recent years, compared with standard indirect field oriented control, deadbeat-direct torque and flux control (DB-DTFC) has been shown to be a highly effective method for IM control with a fixed switching frequency. It has advantages such as fast torque dynamics with one step dynamic response for torque and flux with no current regulator. This paper evaluates the synergy between back-EMF self-sensing technology and DB-DTFC for IM drive systems. In this paper, an observer-based closed-loop back-EMF tracking self-sensing control in an IM DB-DTFC drive system is presented. It includes a back-EMF state filter, back-EMF tracking observer, and cascaded motion observer. Back-EMF harmonic decoupling is explored to improve the low-speed performance. The band-pass filter method (BPF) for back-EMF self-sensing is also presented. Finally, the closed loop system dynamic stiffness at very low speeds, with and without the BPF method, is experimentally evaluated. [ABSTRACT FROM AUTHOR]

In speed sensorless induction machine control, the reduced-order observer, i.e., the combined voltage and current (UI) mode flux observer, obtains good flux estimation results in the full-speed range but has some drawbacks in the stability characteristics. This paper constructs the small-signal model of the UI mode flux observer and derives the characteristic matrix to realize the stability analysis, based on which the stable range with corresponding conditions has been calculated explicitly. Furthermore, a cross-coupling feedback mechanism is proposed to solve the instability problem when the machine runs in the low-speed regenerating or plugging-in mode. The cross-coupling feedback coefficient is adjusted by the estimated speed or the speed command (conditional) for further simplification and is easy to be implemented. The improvement strategy is well verified by both the simulation in MATLAB and corresponding experimental results. [ABSTRACT FROM AUTHOR]