A lever-bridge combined compliant mechanism for translation amplification

Abstract

The lever-type mechanism is one of the most widely used compliant mechanisms in precision engineering applications. To achieve large amplification ratios, the lever-type mechanisms are often connected in series. However, overstress during the deformation process of the mechanism appears frequently, resulting in the undesired deformation and the distortion of amplification ratios. Also, the enveloping area of the lever-type mechanism is relatively large, which limits its further application. This paper presents a novel combined compliant mechanism for translation amplification, which consists of a bridge mechanism and a two-stage lever mechanism. The compact mechanism could avoid overstress while maintaining a large amplification ratio. Firstly, the design of the mechanism is introduced. The corresponding amplification ratio is modeled and verified by the finite element method. This model includes the vertical drift of flexure hinges in the mechanism, which is consistent with the motion direction of the combined mechanism. Also, the flexures in the levers are characterized. For the sake of avoiding overstress and attaining a large amplification ratio, an optimization of the model is conducted by the genetic algorithm. The optimization results show that more than 100% improvement on the amplification ratio has been achieved, and the maximum stress of the mechanism is admissible. The optimized compliant mechanism is fabricated and tested. Quasi-static and dynamic experiments demonstrate that the amplification factor shows a good agreement with the analytical model.