An energy efficiency approach for unified topological and dimensional synthesis of compliant mechanisms.

Traditional engineered devices have been predominantly designed be strong and rigid. Often, strength and rigidity are critical to achieve designs which are practical, safe, and efficient. However, the inclusion of flexibility in conventional mechanism design can offer many potential benefits including ease of assembly, greater resistance to overloads, and elimination of backlash and friction associated with conventional mechanical joints. A compliant mechanism exploits flexibility from one or more of its members to achieve controlled transmission of forces and motions. Due to their advantages, compliant mechanisms are well-suited for many applications including micro-electro-mechanical systems (MEMS), bio-mechanical devices, smart structures, and general product design. High-performance compliant mechanisms are difficult to design using trial and error techniques. Consequently, the development of a systematic approach to design these devices is critical to improve performance and speed the development of new designs. The main challenge in designing compliant mechanisms has been to integrate the fundamentals of kinematics and structural mechanics to develop a rigorous and systematic design methodology. In this research a two-stage structural design procedure consisting of (i) topology synthesis and (ii) dimensional synthesis was developed. Central to the development of these procedures is the formulation of a robust and unified optimization a roach which has been effectively applied to both topology synthesis and dimensional synthesis problems. Two new models of a linear, static compliant mechanism are introduced and formalized as energy efficiency problems. These energy efficiency problems consider a compliant mechanism (i) a lifting an external load and (ii) pressing against a soft object. Optimization of mechanism designs is numerically implemented using linear finite element theory for truss element as well as frame element structures. Given the fundamental motion requirements, topology synthesis is accomplished by re-distributing a finite volume of material throughout a fixed design domain. Dimensional synthesis is accomplished by optimizing the geometry and cross-sectional sizing of structural members given specific boundary conditions and performance limitations (such as stress constraints) necessary to design practical compliant mechanisms. Results of the numerical implementation demonstrate the capability and robustness of the automated design procedure. Several new and innovative compliant devices are synthesized using the two-stage synthesis approach including a compliant wrench, several stroke-amplification mechanisms, and a micro compliant transmission.PhDApplied SciencesMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132151/2/9959775.pd