| Biological systems show a reliance upon their capability to adapt limb stiffness as a means to achieve dynamically similar locomotion over a wide range of terrains. The versatility of robotic platforms falls short in comparison to their biological counterparts. One possible method to enhance the performance of these systems is to integrate a variable stiffness mechanism into the locomotive structure to aid in their adaptability. To date, many variable stiffness mechanisms have been designed, but they have multiple drawbacks. The current mechanisms are typically too slow to achieve rapid adaptations during dynamic locomotion or too large for implementation onto smaller platforms. It is desirable to have a variable stiffness mechanism that is able to achieve a large reduction in stiffness in the minimal amount of time.;This work focuses on the development process of a dielectric elastomer based variable stiffness mechanism as a replacement for traditional springs on a legged hexapedal robot. A simulation is developed assessing the stability benefits of an ideal variable stiffness mechanism actuated over the period of a single stride during dynamic locomotion. The design process is detailed and the characterization of the mechanism in terms of its magnitude for stiffness reduction, transient response to stimuli, and implementability is presented. The newly developed system shows up to an order of magnitude reduction in stiffness at an actuation frequency approximated at 10Hz. The system is implemented onto an adapted version of the dynamic running robot, iSprawl, and its performance is characterized with respect to forward velocity. Reliability issues in the current manufacturing process pose a potential problem, but new methods are proposed to increase durability and repeatability of the mechanism. Finally, the next generation design for implementation onto a new platform is presented. |
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