Optimization for Large or Linear Tunable Stiffness Control With a Concentric Circular Tapered Beam Design

Most examples of structure controlled Tunable Stiffness Mechanisms (TSM) systems have two predefined settings of stiffness, e.g. bi-stiffness behavior, or they have a low range in tunable stiffness. In this research, this problem of control is overcome though optimization of a novel concentric circular tapered spring beam design with the novel design concept of changing the mode of deformation from bending to axial or shear. A Monte Carlo (MC) function is used with an analytical model — the unit load method of virtual work, to determine the optimum shape of two concentric tapered beams where the minimum stiffness is set, and the objective is to achieve linear and/or large stiffness change control. Three optimum designs were 3D printed, tested, and the stiffness vs. loading angle of control was validated with excellent correlation. The optimum design was obtained by changing the dominant loading modes.