Code-based Design for Consistent Prototyping, Manufacture and Physical Modeling of Multimodal Robots

The paper introduces build123things, a software tool for consistent robot design, manufacturing, and physical modeling. It is motivated by designing robotic systems with multimodal locomotion that require multiple simulation models to evaluate their motion capabilities using multimodal planning techniques. The tool uses a Hierarchical Assembly Graph and an algorithm to select the kinematic root, leveraging the Code-CAD library build123d and the OpenCASCADE geometry kernel. It employs explicit reference geometries to overcome the Topological Naming Problem (TNP) of existing mainstream Computer Aided Design (CAD) systems relying on implicit geometry element naming. Rich material annotations and assembly semantics enable use across design, simulation, and manufacturing, narrowing the sim-to-real gap. Its usage is demonstrated in a robotic arm design and a climbing magnetic robot case study, where build123things supports multimodal planning by implementing kinematic hierarchy transforms.