Design and optimization of compliant mechanical amplifiers

Abstract

Piezoelectric (PZT) actuators are micro motion generators capable of producing a high displacement resolution and low strain with high force outputs. However, due to their relatively short motion ranges, the functions of PZT actuators become limited or infeasible for many of the above mentioned applications. One technique to overcome the mentioned shortcoming is to integrate a PZT actuator with a mechanical displacement amplifier. Such an amplification mechanism can be based on a compliant mechanical displacement amplifier (CMDA). A CMDA has many advantages such as no friction losses, no need for lubrication, no tolerance, and et al. over conventional rotating pinjoint mechanisms. Hence, the primary goal of a CMDA is to achieve a large output displacement in desired direction(s) for a given input displacement generated by a PZT actuator, and to keep a high positioning resolution at the same time. This thesis describes a complete study on the design, development and optimization of two proposed CMDA’s, one for the use in prostate Magnetic Resonance Elastography (MRE) application, and the other for the use as a planar motion generator mechanism for the application in high precision manipulation systems. The design of the both proposed mechanisms are based on the symmetric five-bar topology which facilitates a high amplification ratio (AR) with maintaining a relatively high natural frequency (NF). The first proposed CMDA was designed and optimized to amplify the generated motion of a PZT actuator in only one direction with keeping the NF as high as possible. On the other hand, the design and optimization of the second proposed CMDA was done to convert the linear motions of the integrated PZT actuators into a XY planar motion with high accuracy and resolution. In this study the comprehensive FEM analysis and simulations of both proposed CMDA designs are provided.