Combining self-sensing with an unkown-input-observer to estimate the displacement, the force and the state in piezoelectric cantilevered actuators

Self-sensing techniques is defined as the use of an actuator as a sensor at the same time. The main advantage of such techniques is the embeddability and the packageability of the systems. This paper deals with the development of a self-sensing technique able to estimate the displacement, the force and the state in piezoelectric cantilevered actuators. The main novelties relative to previous works are: 1) three signals (displacement, force and states) are provided at the same time instead of only two (displacement and force), 2) and these three signals are provided in a complete way, i.e. low and high frequency information can be provided (instead of exclusively low or high frequency). It is therefore possible to further use the measurement for a displacement control or for a force control by using the output feedback methods or by using modern control methods (state-feedback). In order to allow such measurement possibilities, the proposed approach consists in combining an unknown-input-observer (UIO) with the classical electrical circuit of a self-sensing. The experimental results confirm the effectiveness of the proposed approach.