Nonlinear observer and controller design for sensorless operation of a continuously rotating energy harvester

This paper presents the design of a nonlinear observer and a nonlinear feedback controller for sensorless operation of a continuously rotating energy harvester. A mathematical model of the harvester with its power electronic interface is discussed. This model is used to design an observer that estimates the mechanical quantities from the measured electrical quantities. The gains of the observer depend on the solution of a modified Riccati equation. The estimated mechanical quantities are used in a control law that sustains power generation across a range of source rotation speeds. The proposed scheme is assessed through simulations and experiments.