A novel state observer for dynamical systems with inaccessible outputs

This paper presents a state observer based on the action reaction law of dynamics. The proposed observer allows estimating states of single input flexible dynamical systems with unknown or inaccessible outputs where the instantaneous system reaction is utilized as a feedback like force/torque and used in the design of a state observer. Necessary and sufficient conditions for observability of this class of dynamical systems are investigated. Robustness of the proposed state observer to parameter uncertainties is further studied. The proposed observer makes it possible to keep a class of single input flexible dynamical systems free from any attached sensors while estimating their states. Validity of the proposed action reaction based state observer is evaluated experimentally.