Topology Synthesis of Compliant Mechanisms

Michael Y. WANG, Xiaoming WANG, Shikui CHEN (02/2005)

A compliant mechanism is able to deliver energy and motion from specified input ports to output ports utilizing the elastic deformation in some or all the parts of the structure. Compared with a rigid-body mechanism, a compliant mechanism has some intrinsic advantages. Being in a monolithic form, a compliant mechanism can be manufactured with small size, light weight and ease in assembly . Furthermore, it eliminates back slash, wear and friction, which are associated with a rigid-body mechanism, for it transmits motion and energy not by the rigid-body motion but by the flexibility of the structure. These merits have made compliant mechanisms useful in applications both in the macro domain and in the micro domain, for instance, for high precision manipulation stages, instruments for minimally invasive surgery, and Micro-Electro-Mechanical Systems (MEMS). However, compliant mechanisms present to us with a great challenge for their systematic designs.

 Our research goal is to develop a systematic method that is able to generate complex topologies of functional mechanisms. Different from traditional trial-and-error method, in our research, the topology optimization problem is considered as a variation problem with respect to a class of admissible boundaries of the design object. In this manner, the design problem is recasted as an inverse problem to find the favorable shape so that the design can acquire required performance. Our optimization process is distinguishedly characterized by the continuous moving of the dynamic boundaries. Being able to cope with topological changes in a natural way, Level Set Method (LSM) is employed to represent the moving boundaries on a fixed Eulerian grid. At the same time, a Hamilton-Jacobi equation is used to evolve the boundary during the optimization process.   Our research is hoped to be able to provide a practical answer to the present and future needs of efficient design, synthesis, and application of compliant mechanisms.

   Initial topologies (half)

Final designs

(Click  the picture to see the movie )

1. A Displacement Inverter

2. A pull-gripper

3. A push-gripper

4. Designs with different volumes

5. Compliant mechanisms and their rigid-body equivalents

6. Multi-material compliant mechanisms

Supported by:

• HKSAR Research Grants Council (RGC) Competitive Earmarked Research Grant (CERG).

• The Natural Science Foundation of China (NSFC).

• The Overseas Young Investigator Collaboration Award (50128503).

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