Static shape control of smart structures: A new approach utilizing compliant mechanisms

Smart structures are "active" structures capable of sensing stimuli, and responding with active control. Static shape control of a smart structure is a controlled response involving quasi-static change in its configuration from a given state into another desired state. Static shape control of smart structures finds numerous potential applications, especially in the aerospace field, and is accomplished in the current practice by interfacing an "inert" structure with a distribution of a multitude of discrete smart materials based actuators and control capabilities. Such a distributed actuation approach has several advantages. However, the implementation of this technology in many practical applications is currently impeded by certain limitations such as inadequate stroke and response time of the state-of-the-art smart materials based actuators, numerousness of the actuators required, and the associated complexity of the distributed parameter control.; Therefore, motivated by the need for improved actuation schemes, a novel approach for static shape control of flexible structures has been developed in this dissertation. The new approach offers practicable solutions for real-scale applications while reducing the number of actuators and control complexity of the system. In this approach, a given beam segment is "deformed" into prescribed shapes by transmitting controlled displacements to "optimal" points on the segment from one or two actuators (not limited to smart materials) located away from the segment through a special class of mechanisms called compliant mechanisms--mechanisms that achieve mobility from the elastic deformations of its links and joints. This research has developed two procedures for systematic syntheses of complaint mechanisms for effectuating desired shape changes in a given segment in two possible modes: one involving pure bending and the other involving bending plus a rigid-body motion. The procedures are based on the first-principles of kinematics and mechanics combined through structural optimization techniques. In these procedures, first the topology of the compliant mechanism is systematically established by generating a frame-work of beam elements between predetermined "optimal" activation points on the given segment and the input actuation point(s); then, the dimensions of the mechanism are optimized by solving inverse problems. The two procedures are illustrated by an example for each case.