Dynamics of spherical telescopic linear driven rotation robots

TL;DR

This work tackles the problem of exploring lunar caves with robust robotic systems by introducing DAEDALUS, a spherical robot that uses telescopic linear rods to locomote via pushing against the ground and leveraging gravitational torque. It develops a dynamic model for this rod-driven locomotion, analyzing three interaction modes—no-slip push, slip push, and leverage—and elucidates how friction coefficients and inertia shape translation and rotation. The study identifies regimes where rod leverage guarantees forward motion, characterizing the coupling between translation and rotation and highlighting the critical role of ground-friction parameters. The results establish foundational dynamics for dimensioning components and guiding future experiments, with practical implications for obstacle negotiation and integrated environment mapping via an onboard terrestrial laser scanner.

Abstract

Lunar caves are promising features for long-term and permanent human presence on the moon. However, given their inaccessibility to imaging from survey satellites, the concrete environment within the underground cavities is not well known. Thus, to further the efforts of human presence on the moon, these caves are to be explored by robotic systems. However, a set of environmental factors make this exploration particularly challenging. Among those are the very fine lunar dust that damages exposed sensors and actuators and the unknown composition of the surface and obstacles within the cavity. One robotic system that is particularly fit to meet these challenges is that of a spherical robot, as the exterior shell completely separates the sensors and actuators from the hazardous environment. This work introduces the mathematical description in the form of a dynamic model of a novel locomotion approach for this form factor that adds additional functionality. A set of telescopic linearly extending rods moves the robot using a combination of pushing away from the ground and leveraging the gravitational torque. The approach allows the system to locomote, overcome objects by hoisting its center of gravity on top, and transform into a terrestrial laser scanner by using the rods as a tripod.

Figures (7)

• Figure 1: The DAEDALUS sphere. From left to right: First, Daedalus sphere is descended into the pit by a crane. Second, DAEDALUS in scanning mode. Third, Different modes of DAEDALUS. Fourth, DAEDALUS overcoming obstacles by pushing with its rods.
• Figure 2: Force evaluation of the pushing approach with no slip due to an obstacle.
• Figure 3: Analytical solution of Equation \ref{['Eq:aDotOmegaNoSlip']}. Above: Solution for $A=10$. Below: Solution for $A=0.15$.
• Figure 4: Analytical solution of Equation \ref{['Eq:aDotOmegaNoSlip']} with $A=0.15$ and the geometrical possible $\dot{\zeta}$s with a radius of [0.4]m and a maximum length of [0.1]m. The force solution is limited by either the extension speed or the sheer fact that the pole length is not long enough to reach $\zeta$
• Figure 5: Force evaluation of the pushing approach with a complete slip of the poles.