A comparative study of piezoelectric unimorph and multilayer actuators as stiffness sensors via contact resonance

摘要

Piezoelectric bar-shaped resonators were pro-posed to act as hardness sensors in the 1960s and stiffness sensors in the 1990s based on the contact impedance method. In this work, we point out that both multilayer and uni-morph (or bimorph) piezoelectric actuators could act as stiffness/modulus sensors based on the principle of mechan-ical contact resonance. First, the practical design and the performance of a piezoelectric unimorph actuator–based stiffness sensor were presented. Then the working principle of piezoelectric multilayer actuator–based stiffness sensors was given and verified by numerical investigation. It was found that for these two types of resonance-based sen-sors, the shift of the resonance frequency due to contact is always positive, which is different from that of the contact impedance method. Further comparative sensitivity study indicated that the unimorph actuator–based stiffness sensor is very suitable for measurement on soft materials, whereas the multilayer actuator–based sensor is more suitable for hard materials.