Topology Synthesis of Compliant Systems with Embedded Actuators and Sensors.

Abstract

The basic premise of a compliant system is the integration of motion/force transmission via elastic deformation with embedded actuation and sensing. Current electromechanical systems are generally fashioned in the rigid-and-discrete paradigm where one first designs a rigid structure with mechanical joints and then adds actuators and sensors, with the design of controls only following as an afterthought. The objective of this research is a systems approach to synthesis of mechanism, structure, actuation, and sensing, thereby advancing from traditional mechanical design to automated compliant system design. In previous studies of compliant mechanisms and their synthesis, single-actuator mechanisms have primarily been considered, with the determination of the actuator’s type, orientation, size, and location occurring outside of the automated design synthesis, at the designer’s option. A new algorithmic framework is presented, in which structural topology and actuator/sensor placement are simultaneously synthesized for maximum energy efficiency and adaptive performance. Significantly, this is not a traditional ad hoc method; sensor and actuator placement affect structural topology and vice versa.

The methods used include genetic algorithms, graph searches for connectivity, and multiple load cases implemented with linear finite ele¬ment analysis. Fundamental metrics for the inclusion of embedded components in a multifunctional compliant system are developed and investigated. Actuators, modeled as both force generators and structural compliant elements, are included as topol¬ogy variables in the optimization. The essential framework for the integration of controls with compliant mechanisms is established. Specifically, the concepts of controllability and observability, as redefined for compliant systems, are proven as a successful starting point for the design of multifunctional, adaptive systems. These concepts refer to the unique sys¬tem response for each component (actuator or sensor) it contains. Results are presented for several problems, focusing on the application of shape-morphing aircraft structures. Through examples and design studies, the metrics and the methodology demonstrate that multiple, optimally-placed components indeed offer performance benefits for mechanical systems, both in terms of efficiency and multifunctional execution. Finally, the extension of controllability to address the problem of single-point manipulation is performed to show the generalized use of the new methodology in benefitting the design of compliant systems.