Nonlinear estimator design of automotive alternator utilizing battery current and speed measurements

Nonlinear estimator design for synchronous rectification of the automotive alternator used in the electrical power supply system is a desirable approach for estimating alternator's back electromotive forces without a direct sensor of the rotor position. Here, we focus on the theoretical development of the estimator design for a realistic case of variable engine speed using the "sliding mode observer" and "nonlinear asymptotic observer" schemes. We develop a no vel cascaded observer that is capable of recovering the back electromotive forces utilizing only measurements of the battery current (which is readily available in the control system), output DC voltage, and automotive engine speed. We use high gain observers with an asymptotically stable equilibrium point corresponding to the zero estimation error. Finally, performance of the proposed observers is validated by computer simulations.