Publication
Compliant mechanisms can advantageously be preloaded by buckled beams in order to reduce their motion stiffness, and therefore also their actuation forces. However, preloading compliant mechanisms has the side-effect of modifying the deformation of their flexural elements, thus resulting in altered motion trajectories. In this paper, the case of a flexure-based translation stage is treated taking into account both issues at the same time, leading to a design benefiting from a preloaded buckled beam simultaneously for stiffness reduction and motion rectilinearity improvement. The studied mechanism is a compliant planar four-bar rectilinear stage based on four Remote Center of Compliance (RCC) pivots, called 4-RCC, manufactured in aluminum alloy by Electrical Discharge Machining (EDM), equipped with a buckled beam made of hardened spring steel. The mechanism is dimensioned based on analytical and finite element models to obtain simultaneously a near-zero stiffness and a quasi-rectilinear translation. Experimental results show that the buckled beam reduces the translational stiffness of the stage more than 98%, while decreasing the parasitic shift of the stage by more than 85%. In absolute terms, over a total translation stroke of 8 mm, a parasitic shift below 0.95 µm and a restoring force below 0.1 N were measured. This study validates the proposed design approach and paves the way for the use of such 4-RCC mechanism for precision positioning applications requiring high-straightness motion and low-power actuation.