Giuseppe Radaelli

Isogeometric Shape Optimization for Compliant Mechanisms With Prescribed Load Paths

This paper presents a method for the design of compliant mechanisms with large deflections and prescribed load paths. While the approach is general, this paper treats the shape optimization for two dimensional beams. Due to the geometric non-linearity of the problem the non-linear analysis is nested into the optimization procedure. This requires accurate and efficient analysis of the structural problem. The analysis of the beam is based on the Isogeometric Analysis formulation, an alternative for conventional FEA especially appreciated for its shape-accuracy and efficiency. The method is applied to the synthesis of a balancer for a pendulum, which involves a two step load case: first a prestressing phase and subsequently a motion phase under the influence of gravity. To this end, a prestressed compliant beam was optimized with respect to its initial shape and the preload conditions. The rotationless character of the degrees of freedom of the Isogeometric beam requested the formulation of specific boundary conditions in order to apply rotations on the beam. The results of the shape optimization have been validated with a prototype out of carbon fiber composite material, which has been successfully tested. The experimental results are in agreement with the simulation results, with an error of 3%.Copyright

An energy approach to the design of single degree of freedom gravity balancers with compliant joints

A gravity balancer is a mechanism that compensates the weight of a mass over a range of motion. When no friction is present, this gives an energy efficient mechanism and little effort is required to move an object. Conventional mechanisms have drawbacks due to the use of conventional rigid joints. Compliant joints do not have these disadvantages, can be made from fewer parts and can increase performance compared to rigid body joints. The goal of this paper is to develop a new method for the design of single degree of freedom gravity balancers where all the rigid joints are replaced with compliant joints. The method is based on connecting rigid links with compliant joints. With a constant potential energy as an objective, the method allows new gravity balancers to be designed. The second goal is to construct a demonstrator as proof of principle. It can be concluded that for the first time a gravity balancer has been constructed where all the rigid joints are replaced with compliant joints. The gravity balancer had a peak moment reduction of 93%. The presented method is extensible and allows others to understand and further develop gravity balancers with compliant joints for other applications.Copyright

An Energy Approach to a 2DOF Compliant Parallel Mechanism With Self-Guiding Statically-Balanced Straight-Line Behavior

This paper presents a novel straight-line self-guiding statically-balanced mechanism which reflects on the advantages of lumped compliant mechanisms. The forthcoming structural design is conceived with an energy approach for static balancing of mechanisms. In this paper the application and effectiveness of the energy approach as a synthesis tool is validated. Moreover the paper demonstrates the translation from pseudo-rigid body model to lumped compliance in statically-balanced mechanisms. A physical prototype and a finite-element model served to evaluate the conceptual design. Manufacturing techniques are suggested for rapid, light-weight and cost-efficient prototyping. The presented self-guiding mechanism is statically-balanced along its straight-line range of motion while showing stable behavior in other directions.Copyright