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.

Highlights

  • Providing of relatively low level of rotation The rotation is not pure due to the complex deformation of the flexure, as it is produced by axial shearing and possibly torsion loading The rotation center is not fixed The flexure hinge is sensitive to temperature variation which results in modification in the original compliance value In addition, the design of a compliant mechanism is more complicated than the design of a conventional rotational pin jointed mechanism, as it requires large deflection analysis, the consideration of the stored strain energy, and the solution of transcendental loop closure equations

  • The topology of each developed mechanisms were based on the symmetric five-bar structure (Ouyang, Zhang, & Gupta, 2008) due to the advantages such as high Amplification Ratio (AR) and minimal loss of Natural Frequency (NF) facilitated by this structure

  • This thesis study was started with an extensive review on various topologies available for developing compliant based mechanical amplifiers (CMA)

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Summary

Compliant Mechanism

A compliant mechanism is a mechanism that its components (i.e. parts) are linked together by some flexible, slender members known as flexure hinges. The flexure hinges must undergo a relative limited rotation in the mechanism to achieve a specific task (Lobontiu, 2002).

Application of Compliant Mechanisms in High Precision Manipulation Systems
Organization of the Thesis
Introduction
Compliant Mechanical Amplifiers
A Compact Low-Stiffness Six DoF Compliant Precision Stage
Environmental Consideration in the Design of Compliant Mechanisms
Topology Optimization Techniques
Topology of Symmetric Five-Bar Structure
Concluding Remarks
Design Requirements and constraints
Initial FEM Static and Dynamic Analysis
Design Parameters
Optimization Process
Static and Dynamic FEM Analysis on the Optimized Design (Unloaded CMDA)
Experiments for Unloaded and Loaded CMDA for Prostate MRE Application
Conclusion
Design Requirements and Constraints
Static and Dynamic FEM Analysis on the Optimized Design
Fabricated CDMA
Overview and Conclusions
Major Contributions of the Thesis
Future Research Work

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