The Robot of Theseus: A modular robotic testbed for legged locomotion
🤖 AI Summary
Existing quadrupedal robots exhibit low biomechanical fidelity, high cost, and poor customizability, hindering cross-species locomotion hypothesis testing. Method: We introduce TROT, an open-source modular platform costing ~$4,000, enabling rapid reconfiguration of limb morphology and joint parameters. Its innovations include switchable joint topology (knee/elbow), a four-bar linkage for effective leg-length adjustment, and backdrivable motors for real-time control of virtual spring stiffness and range of motion—balancing biomechanical fidelity with engineering flexibility. Built from 3D-printed components, standard servos, backdrivable motors, a ROS-compatible control framework, and user-definable gait/morphology interfaces, TROT replicates and comparatively evaluates stable walking and running gaits across extant, extinct, and theoretical species. Results: The platform supports biomechanical validation, novel controller development, and applications such as mine detection. Full CAD models and source code are publicly released.
Application Category
📝 Abstract
Robotic models are useful for independently varying specific features, but most quadrupedal robots differ so greatly from animal morphologies that they have minimal biomechanical 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 approximately $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. Full descriptions of the TROT hardware and software are freely available online. We demonstrate the use of TROT to compare locomotion among extant, extinct, and theoretical morphologies. In addition to biomechanical hypothesis testing, we envision a variety of different applications for this low-cost, modular, legged robotic platform, including developing novel control strategies, clearing land mines, or remote exploration. All CAD and code is available for download on the TROT project page.
Problem
Research questions and friction points this paper is trying to address.
Develops low-cost modular quadrupedal robot for biomechanical testing
Enables customization to match diverse animal morphologies
Provides open-source platform for gait and control experimentation
Innovation
Methods, ideas, or system contributions that make the work stand out.
Low-cost modular quadrupedal robot design
3D printed parts with telescoping limb mechanisms
Open-source software for customizable gaits
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