Concept of Self-Sensing Solid-State Actuators

4 Concept of Self-Sensing Solid-State Actuators 

The inherent sensor effect in active materials allows, in combination with proper measurement and signal processing methods, the simultaneous use of piezoelectric or magnetostrictive transducers as both sensors and actuators. At present there exists two different methods, a state quantity-related and a parameter-related for using these inherent sensor effects [336]. In both cases the mechanical values of F and s must be reconstructed from the measured electrical quantities. 

The state quantity-related sensing method makes use of the dependence of the thermodynamical dual electrical quantity y q,tp) on the electrical control quantity X(V, I) and the mechanical load F according to (6.55). The reconstructed mechanical load Fr is gained by means of measurements Am and j/m of the quantities A and y according to 

For this purpose the inverse of the y-F mapping with A as a parameter must be calculated. The reconstructed transducer displacement is then obtained in a second step by fitting in the reconstructed force F into the actuator equation (6.56). The corresponding reconstruction filter equation is 

This is done in a so-called reconstruction filter unit, compare Fig. 6.135. The measured values Am and are determined from the port quantities A and z by means of special electrical measurement circuits. Together with the driving electronics for the transducer, they form part of the measurement circuit and power electronics unit illustrated in Fig. 6.135. 

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Fig. 6.8. Concept of self-sensing solid-state actuators...

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