Motion Analysis System for Robot Traction Device Evaluation and Design

Abstract

Though much research has been conducted regarding traction of tires in soft granular terrain, little empirical data exist on the motion of soil particles beneath a tire. A novel experimentation and analysis technique has been developed to enable detailed investigation of robot interactions with granular soil. This technique, the Shear Interface Imaging Analysis method, provides visualization and analysis capability of soil shearing and flow as it is influenced by a wheel or excavation tool. The method places a half-width implement (wheel, excavation bucket, etc.) of symmetrical design in granular soil up against a transparent glass sidewall. During controlled motion of the implement, high-speed images are taken of the sub-surface soil, and are processed via optical flow software. The resulting soil displacement field is of very high fidelity and can be used for various analysis types. Identification of clusters of soil motion, shear interfaces and shearing direction/magnitude allow for analysis of the soil mechanics governing traction. The Shear Interface Imaging Analysis Tool enables analysis of robot-soil interactions in richer detail than possible before. Prior state-of-art technique relied on longexposure images that provided only qualitative insight, while the new processing technique identifies sub-millimeter gradations in motion and can do so even for high frequency changes in motion. Results are presented for various wheel types and locomotion modes: small/large diameter, rigid/compliant rim, grouser implementation, and push-roll locomotion.

Traverse Performance Characterization for the Mars Science Laboratory Rover

“…Experimental testing has been performed at the single wheel level to determine the influence of several physical wheel parameters such as diameter, width, grouser size, and spacing (Ding et al., ). Similar experiments have been performed to characterize soil flow under a wheel in granular materials (Moreland et al., ; Senatore et al., ). A single wheel test apparatus has also been used in an attempt to characterize the soil properties of planetary bodies based upon wheel soil interaction (Sullivan et al., ).…”

“…As vehicle slip and consequently wheel sinkage increase, the motion resistance is increased due to the undisturbed terrain in front of the wheels (Wong, ). For the same sinkage, the high curvature of the smaller diameter wheel results in higher motion resistance than the larger diameter wheel of the same ground pressure (Skonieczny et al., ). This extra motion resistance at a given sinkage can be thought of as a steeper slope in front of the smaller wheel due to its higher curvature.…”

UTOPUS Traction Technology: A new method for planetary exploration of steep and difficult terrain

“…by inclining the surface and all devices acting thereon (Zou et al, 2015), or by conducting experiments in planes during parabolic flight maneuvers which achieve a temporary low gravity (Kobayashi, 2010, Nakashima 2011. Moreland et al (2014) introduce soil optical flow technique to study soil behavior under a vehicle. While not specifically addressing gravity, the method promises relevant insight also for the present innovation.…”

Interaction Mechanics Model for Rigid Driving Wheels of Planetary Rovers Moving on Sandy Terrain with Consideration of Multiple Physical Effects

“…(ii) Slip sinkage (Ding, Gao, Deng, & Tao, ; Ding et al., ; Leger et al., ): with the increase in the slip ratio, the wheel sinkage and resultant compression resistance increase rapidly, leading to an elevated risk of the wheel being stuck. (iii) Dimension effect (Ding et al., ; Moreland, Skonieczny, & Wettergreen, ): the radius and width of the wheels have an obvious influence on their driving performance. (iv) Load effect (Ding et al., ): the interaction of the wheel with the terrain is influenced by the normal load, and the tractive coefficient is increased if the normal load is smaller for a lugged wheel moving on sandy terrain.…”