Design of a Compliant Hinge based on Closed Form Pressure Balancing

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Compliant mechanisms consist of a monolithic body and obtain motion through elastic deformation. Multiple compliant flexure designs are known but their range of motion and load capacity are often limited. When considering rotational hinges, improving the operational range requires reducing the rotation stiffness while increasing normal stiffness. This work introduces a novel compliant hinge design with increased stiffness ratio compared to the state of the art compliant hinges. The design makes use of a so-called closed form pressure balancing principle to obtain this high ratio. This principle utilizes incompressible fluid inside a closed body. A 2D parameter sweep is performed to identify the highest performing hinge design. Subsequently, a computational 3D analysis is performed and the resulting design is realized as a demonstrator. The performance is compared to conventional compliant hinges based on the ratio of the normal- and rotation-stiffness. This showed an increase of at least a factor 30 on the stiffness ratio.