Softening Of Compliant Mechanism And Static Balancing Design

Compliant mechanism is a kind of mechanism that utilizes its flexibility (or somecomponent’s flexibility in it) to obtain all or partial of its motion. It has reduced numberof components and decreased process of assembling, avoids gap and friction betweencomponents and improves the motion accuracy and service life, thus making themechanism simple and reliable. However, elastic deformation increases the effectrequired to move a compliant mechanism. This leads undesired energy storage in themechanism, which releases in the form of work done by the spring back force when thedeformed components return to their initial shapes. The property of energy storage andenergy release of compliant mechanism reduces its usability in a certain extent, such asincrease of driving force and invalid perception of force feedback.In this thesis, we first give a brief introduction to compliant mechanisms and majordesign methods and application fields of them, present the concept of softening ofcompliant mechanism, and describe the approaches to achieve softening and staticbalancing of compliant mechanisms. Second, softening and static balancing of somecompliant mechanism designs are realized using the method aforementioned:(1) basedon a compliant four bar model, a mechanism that can be installed on trunk lid to meetits design requirements is designed through optimization, which shows a bi stablebehavior without extra driving equipment;(2) a similar design of a compliant four barmechanism to statically balance a weight that rotates around a fixed axis is obtained;(3)a statically balanced mechanism consisting of two multi stable mechanisms combinedin series is designed, and the static analysis of it in finite element analysis softwareANSYS indicates it can realize static balance in a certain range of motion;(4) themulti stable characteristics of partial or full compliant Sarrus mechanisms (a rigid bodySarrus mechanism is a spatial mechanism with6rigid rotation pivots) are studied, andthe methods of utilizing the multi stable characteristics to realize static balancing incompliant Sarrus mechanisms are presented. At last, the proposed methods for realizingsoftening and static balancing of compliant mechanisms are summarized, as well asdesign results achieved using these methods. The prospect of this work is presented.The methods of softening and balancing of compliant mechanism presented in thisthesis successfully realizes low stiffness or zero stiffness of compliant mechanism inspecial motion range, leading to wider applications of compliant mechanisms,especially efficient utilization in MEMS where high accuracy is often required. Softening and balancing of compliant mechanisms also improve the performance,simplify maintenance, reduce the actuators’ size and the volume and weight of themechanisms, and improve the safety and reliability.