Robotic models are useful for independently varying specific features, but most quadrupedal robots differ so greatly from animal morphologies that they have minimal evolutionary relevance. Commercially available quadrupedal robots are also prohibitively expensive for biological research programs and difficult to customize. Here, we present a low-cost quadrupedal robot with modular legs that can match a wide range of animal morphologies for biomechanical hypothesis testing. The Robot Of Theseus (TROT) costs ≈$4000 to build out of 3D printed parts and standard off-the-shelf supplies. Each limb consists of 2 or 3 rigid links; the proximal joint can be rotated to become a knee or elbow. Telescoping mechanisms vary the length of each limb link. The open-source software accommodates user-defined gaits and morphology changes. Effective leg length, or crouch, is determined by the four-bar linkage actuating each joint. The backdrivable motors can vary virtual spring stiffness and range of motion.
This work was collected to evaluate Stability Basins for characterizing the limits of human stability during Sit-to-Stand. and MATLAB code was used to process the data into individual trials. Trials are labeled by Sit-to-Stand type (Natural, Momentum-Transfer, or Quasi-Static) and experimental condition. MATLAB code for analyzing the data and computing Stability Basins is provided. A GUI is provided to animate a subject's movement and display projections of the Stability Basins in the horizontal and vertical planes.
https://arxiv.org/abs/1908.01876 and Holmes, P. D., Danforth, S. M., Fu, X.-Y., Moore, T. Y., & Vasudevan, R. (n.d.). Characterizing the limits of human stability during motion: Perturbative experiment validates a model-based approach for the Sit-to-Stand task. Royal Society Open Science, 7(1), 191410. https://doi.org/10.1098/rsos.191410