Synthesis of shape morphing compliant mechanisms.

Life's creations have inspired engineering design for centuries. For example, the design of an aircraft was inspired by observation of birds in flight, although birds morph their wings while aircrafts have fixed wing shapes. Many designs in nature are found to be compliant, that is, they rely on elasticity to morph shapes, transmit forces and motions. This research focuses on exploiting compliance in structures to achieve desired shape morphing. Majority of the previous work on adaptive structures or structures that morph their shape on demand, focused on application of smart actuators with limited success. Exploiting the compliance of the underlying structures leads to scalable designs. Much of the previous research on compliant mechanisms focused on single-input single-output designs. Designing a compliant mechanism to function as an adaptive structure requires transmitting forces to multiple output points. The main contribution of this dissertation is the development of a systematic method for synthesizing the topology and dimensions of compliant mechanisms for shape morphing applications. The key features of this dissertation include: (a) Use of genetic algorithms for topology design. The topology design variables are represented in their natural, binary form. This eliminates the gray area issue seen in previous research which leads to ambiguity in the final topology interpretation. (b) Use of load path representation scheme for design domain parameterization to ensure structural connectivity among input, ground, and output members. This eliminates infeasible designs from the design space, resulting in efficient and effective convergence to feasible solutions. This representation does not require an initial ground structure, thus the resulting solution does not depend on designer's intuition. Many other aspects of compliant mechanisms design are addressed in this work including developing the design domain initialization for task feasibility analysis and output point identification; formulating alternate objective functions for shape morphing applications using least square errors and a modified Fourier Transformation method; and allowing variable mesh parameterization through the use of intermediate connection ports. The synthesis methodology is demonstrated through several design examples, including morphing airfoils and antenna reflectors. The methods developed in this work not only successfully solved the shape morphing problems, but they also applied well to single-input single-output compliant mechanism designs as well as design of structures. The generalized design synthesis method developed in this dissertation can also be applied to design of micro, meso, and macro scale artifacts.PhDApplied SciencesMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124248/2/3137882.pd