Abstract:

Multicomponent measurement systems centered with piezoelectric force sensors are one of the most significant force measurement equipment’s in aerodynamic, aviation etc. The contact stiffness of sheets and electrodes, is a basic performance parameter, not only plays a significant role on load sharing and sensitivity of piezoelectric force sensors, but also affects the stiffness and static/dynamic performance of multicomponent measurement systems. As the contact stiffness has been generally neglected, there are little rules to design and packaging sensors; even it is rather different to calibration in multicomponent measurement systems. To solve these problems, influence factors of contact stiffness between sheets and electrodes is researched. Mathematical model is built based on fractal theory. The parameters such as surface topography of sheets, materials of sheets and electrodes and reload are optimized. Moreover, effect of contact stiffness on performance of sensors such as sensitivity and dynamic are expounded and an optimizing approach to surface roughness of sheets, with contact stiffness as constraint is put forward. Relationship between fractal parameters and measurement data is built using structure function method. The validation tests are performed using two kinds of piezoelectric materials-quartz and Langasite, four kinds of electrodes-TC4, 304, copper, aluminum. The results indicate that methods such as optimizing fractal parameters of sheets, increasing the reload and decreasing elasticity modulus of electrodes are significant for piezoelectric force sensors to improve contact stiffness and increase sensitivity even improve natural frequency. The results provide theory reference for high-performance piezoelectric sensors’ designing.

Key words: contact stiffness, fractal theory, Langasite, quartz, structure function, piezoelectric force sensor