Flexure Based Mechanisms

Dr. Simon Henein, CSEM Switzerland

Abstract
Although the basic principles of flexible bearings have been known for several decades, the design methods that could be found in literature have long remained fragmented. Only recently the interest for flexures and their applications has grown, leading to a more systematic treatise of the respective design methodologies. This development has been driven by the increasing need for motion accuracies in the nanometer ranges, in extreme environments like vacuum, cryogenic or high temperatures, radiations or outer space. While in conventional mechanical bearings motion is obtained by sliding or rolling between solid bodies, flexible bearings rely on the elastic properties of matter allowing several advantages to be obtained:

• no friction and associated hysteresis, no wear;
• no need for lubrication, no risk of jamming;
• no backlash;
• possibility of monolithic manufacturing;
• main sources of errors are systematic and therefore simple control laws can be used.

Outline of the presentation:

• Introduction to flexures and flexure-based mechanisms
• Design of flexure-based articulated structures: kinematical design of multi-degrees-of freedom articulated structures (2 to 6 DOFs), sound use of parallel kinematics, stroke maximization, compensation of parasitic movements, canceling of the elastic restoring forces, use of negative stiffness, bistable mechanisms, virtual levers with high scaling factors.
• Concrete examples from the application fields of equipment for accelerator facilities, space mechanisms, astrophysics instrumentation and high precision robotics.