Feedforward control of module-type deformable truss robot based on finite element method

Module-type deformable robots (MDRs), which combine multiple flexible modules to accomplish different tasks, offer superior adaptability over conventional fixed-morphology robots, making them ideal for rescue and exploration. However, existing control methods fail to fully exploit their potential due to insufficient consideration of external forces and mechanical characteristics of assembled structures. This study addresses these limitations utilizing a powerful structural analysis tool - a finite element method (FEM). As a fundamental step, we especially focused on demonstrating advantages of applying FEM to control of an MDR. We developed an FEM-based inverse analysis scheme using truss elements, along with a modular, deformable truss robot and its feedforward control system. The scheme takes target deformation and external forces as an input and solves a stiffness equation, estimating required actuation forces for each module. Embedded electromagnets and springs provide both passive and active axial movements with modules of the truss robot; the control system first performs inverse analysis and then converts actuation forces into current commands, considering internal and external force effects. Subsequent experiments showed the capability of the control system against simple two- and more complex four-module configurations even under significant self-weight influences. These results highlight the ability of FEM to control MDRs in various configurations and conditions, even without feedback loop, unlocking their full adaptability and functionality.