No abstract

Matching a drive system to the force-displacement characteristics of the load is the cardinal principle in electromechanical systems design. Unconventional actuation schemes, such as piezoelectric, electrostatic, and shape-memory alloys (SMA's), seem to exhibit certain limitations in terms of power density, stroke length, bandwidth, etc., when one attempts to employ them directly to an application. Integrating them with mechanical transmission elements so that the integrated actuator-transmission system matches the load characteristics of the application can enhance the utility of such unconventional actuators. Conventional mechanical devices are sometimes difficult to integrate with unconventional actuating schemes. For instance, the two-dimensional nature of microelectromechanical systems (MEMS) and no-assembly constraints arising from their batch fabrication make it difficult to fabricate, assemble, and integrate a conventional micromechanism with an electrostatic actuator. However, a monolithic "solid-state" mechanical transmission device enables easy integration. This paper presents a systematic method of designing such unconventional mechanisms. The paper presents a generalized methodology for designing compliant mechanisms. Our systematic synthesis formulations provide a mathematical basis for designing compliant mechanisms for: 1) topology generation-that is, establishing a feasible configuration to meet given functional requirements and 2) size and shape optimization-to meet the prescribed quantitative performance requirements, such as mechanical advantage, stroke amplification, etc. Design examples illustrate integration with electrostatic, piezoelectric, and SMA actuators for MEMS and smart-structures applications.

Compliant mechanisms are jointless mechanical devices that take advantage of elastic deformation to achieve a force or motion transformation. An important step toward automated design of compliant mechanisms has been the development of topology optimization techniques. The next logical step is to incorporate size and shape optimization to perform dimensional synthesis of the mechanism while simultaneously considering practical design specifications such as kinematic and stress constraints. An improved objective formulation based on maximizing the energy throughput of a linear static compliant mechanism is developed considering specific force and displacement operational requirements. Parametric finite element beam models are used to perform the size and shape optimization. This technique allows stress constraints to limit the maximum stress in the mechanism. In addition, constraints which restrict the kinematics of the mechanism are successfully applied to the optimization problem. Resulting optimized mechanisms exhibit efficient mechanical transmission and meet kinematic and stress requirements. Several examples are given to demonstrate the effectiveness of the optimization procedure.

No abstract