An improved stiffness model for piezo-actuated complementary clamp flexures

Mechanically complementary clamp configuration is a recent concept in piezoworm motor technology where both clamping sections can be driven simultaneously by same signal which reduces the actuation steps and drive electronics. Despite their opposite functionality, both normally clamp (NC) and normally unclamp (NU) clamps are designed based on same stiffness estimation so far. An improved stiffness model is proposed for normally clamp (NC) clamp section by considering the effects of the preloading, actuator displacement and flexure link length-thickness ratio in order to increase the buckling strength of the spring. It provides a more reliable prediction of the clamp behaviour both during its initial assembly, as well as under subsequently applied tensile loads in service. Finite element analysis is used to validate the proposed stiffness model. Experimental assessments are performed on the prototype to evaluate effect of the clamp stiffness on its displacement.