Dynamic and Repeatable Modular Assembly: How Kinematic Couplings and Proprioceptive Actuators Simplify Robotic Assembly

This paper presents a new assembler robot intended as part of a larger modular self-reconfigurable industrial machine system, with a design focus on (1) the integration of proprioceptive actuators into the assembler robot, and (2) the implementation of kinematic couplings in the modular connectors. We propose two comparison metrics concerning energy efficiency and mechanical repeatability, anticipating their growing importance as robot-assembled modular systems expand in scale. Our prototype assembler robot, Belty, employs high torque density quasi-direct drive belt transmission BLDC actuators. These offer benefits including superior efficiency, back-drivability, impact resilience, and the ability to perform dynamic motions such as hopping. Robust dynamic motion is advantageous for assembly tasks in restricted spaces, where contact-rich actions, such as dragging or bumping, can streamline assembly operations and algorithms. Additionally, we delve into the mechanical design of our connector, which is based on an exact-constraint mechanism called a kinematic coupling. This connector achieves a wide area of acceptance while also offering outstanding repeatability on the order of low tens of micrometers (10  \(\upmu \text {m}\) ).