VIDI project

Large range of motion spatial flexure joints optimization – A topology synthesis method.

Unlike other bearings, flexure joints move by elastic material deformation of slender segments. As a result they have excellent repeatable motion (no friction, no backlash, low hysteresis) which makes them popular in high-precision applications. In addition, their monolithic nature potentially eliminates maintenance and assembly, and strongly reduces part count and mass.

Fundamentally, designers face a trade-off between flexibility for motion in certain desired directions and stiffness to constrain motion for guiding in the remaining directions. Typical flexures have a range of about 10 degrees beyond which the guiding stiffness and load bearing capacity decrease dramatically. Consequently, state-of-the-art positioning mechanisms require a total mechanism volume over workspace ratio of over 3600. This greatly impedes wide-spread application of otherwise superior flexure joints.

This project will break through this historic barrier by developing and combining:

  1. efficient non-linear computer modelling,
  2. a generic method of flexure synthesis,
  3. additive manufacturing techniques.

In 2013 we were the first to combine preliminary versions of these three techniques and achieved an unparalleled combination of 40 degrees range of motion with only 50% of guiding stiffness drop. Based on this result, we estimate that the proposed method will enable an unprecedented range of motion of 90 degrees, while maintaining a sufficiently large guiding stiffness, leading to a mechanism volume over workspace ratio of around 5. 

The aim is to capture the modelling and synthesis method in an open source software code which allows users to synthesize flexure joints for their own needs. We will demonstrate the validity and generality of the method by developing three demonstrators in the fields of precision engineering, medical technology, and robotics. The project outcome will directly impact the design of compact mechanisms for precision and aerospace applications, and lightweight, inherently safe, no-maintenance, design-for-no-assembly and low-cost robotic and medical mechanisms.