This paper presents the simulation and fabrication of a bipedal humanoid system actuated with linear springs to produce a standing equilibrium position.

The humanoid system is comprised of two leg assemblies connected by a hip bracket. Eleven pairs of springs were attached to the system in locations designed to simulate the muscles and tendons in a human body. The assembly was modeled in the multi-body dynamics simulation software SimWise 4D. Simulations were performed to determine the springs’ stiffness and natural lengths using a top-down heuristic approach. After a set of springs were found to produce a good simulated stable position, they were cross referenced to standard commercially-available parts. A final simulation was then performed to verify that the real-world spring values produced a stable system.

Working in tandem with SimWise 4D, the humanoid assembly was fabricated using PLA plastic via an extrusion-type rapid prototyping machine. From the results of the simulation, the set of working springs were implemented onto the plastic model. After final modifications, the assembly then produced a standing equilibrium position. Finally, the assembly was perturbed in several directions to ensure that after the system experienced a displacement it would then return to its original position.

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