Self-Aligning Rotational Latching Mechanisms: A Framework Extension For Orientations & Fast Latching

In previous work, we introduced LIMMS (Latching Intelligent Modular Mobility System), a modular robotic platform capable of acting as either a robotic arm or leg for last-mile delivery tasks. To switch modes, LIMMS modules latch and unlatch onto anchor points in its environment. If LIMMS needs to move a box, a pair of LIMMS can fix its bases to the walls of a delivery vehicle to serve as manipulator arms. If it needs to move outside, four LIMMS can affix to the box sides, serving as legs for a quadruped. In real world applications, latching can bottleneck LIMMS performance. To address this, we introduced a self-aligning rotational latching mechanism framework to mechanically ensure a wide area of acceptance in which latching would be guaranteed under certain assumptions. One such assumption was that the latching mechanism had to be parallel to the surface it was latching into. In this paper, we relax this strict condition. As a result, latching could theoretically still be guaranteed even while experiencing orientation deviations. Using our framework, the LIMMS prototype was able to reliably latch with an angular offset up to 0.3 rads, which was close to the estimated theoretical maximum offset of 0.415 rads. Furthermore, the latching mechanism was able to allow for a combined position and orientation offset of 3 cm and 0.2 rads, respectively. One set of experiments tested dynamic latching where LIMMS would swing from one base point to another. Despite LIMMS being relatively large, 0.83 m in length, it only took 2.4 secs to switch its base to an anchor point 0.65 m away without any visual feedback. Once making contact with the latching surface, it took only 0.149 secs to fully latch which is the fastest latching to our knowledge.