Terramechanics-based investigation of grouser shape for rigid wheels: Comparison between rectangular and trapezoidal grousers

Abstract

It is important to further improve the traveling performances of the moon/planetary exploration rovers. To achieve this, we investigated the grouser shape of rigid wheels for use in such rovers, focusing particularly on rectangular and trapezoidal grousers. First, simple intrusion tests were carried out using the discrete element method. Grousers having a trapezoidal cross-sectional shape exerted a “packing effect” through which particles between grousers were strongly compressed. Next, single-wheel experiments were conducted, and the results show that sinkage was suppressed by the trapezoidal-shaped grousers. In addition, it was confirmed that trapezoidal-shaped grousers exhibited a drawbar-pull equivalent to that generated by the widely used rectangular-shaped grousers. Furthermore, we performed theoretical analysis using the resistive force theory to clarify the packing effect, and the results indicate that the use of a wheel with a trapezoidal-shaped grouser could be an effective method to improve the traveling performance of a rigid wheel.

Keywords:

• wheel–soil interaction
• grouser
• resistive force theory
• discrete-element method
• trafficability

PUBLIC INTEREST STATEMENT

Terramechanics is an interdisciplinary field that deals with the interaction between the ground and vehicles and is effective for trafficability characterization. In this paper, a wheel shape for the lunar/planetary exploration rover based on terramechanics is investigated. Concretely, it is proposed to use a trapezoidal shape for the grouser, which is a protrusion on the wheel surface. The trapezoidal-shaped grouser is expected to exert a packing effect in which particles are strongly compressed between them. When this shape is applied to a wheel, there is a possibility that the trafficability can be improved by suppressing sinkage without significantly reducing the traction. This study will contribute not only to the development of rover wheels but also to the development of undercarriage for other off-road vehicles such as construction machinery and disaster response robots.

Acknowledgements

This work was supported by the Impulsing Paradigm Change through Disruptive Technologies Program (ImPACT), tough Robotics Challenge (TRC), JST, Japan. Moreover, we would like to thank Editage (www.editage.com) for English language editing.

Additional information

Funding

This work was supported by the Japan Science and Technology Agency [ImPACT].

Notes on contributors

Hirotaka Suzuki

Hirotaka Suzuki is PhD candidate for the upcoming year at Department of Mechanical Engineering at Yokohama National University. His specialty is to evaluate the interaction between terrain surfaces and machines, and is the related numerical analyses.

Yutaro Watanabe is a master student at the Department of Mechanical Engineering at Yokohama National University. He is working on DEM analysis of granular media and its application to traveling of lunar/planetary exploration rover.

Taizo Kobayashi is the Professor at Department of Civil Engineering at Ritsumeikan University, Japan. His areas of expertise range from automation of construction work to lunar/planetary exploration.

Karl Iagnemma is President and CEO of Motional, and is co-founder of nuTonomy. As former Director of the Robotic Mobility Group at the Massachusetts Institute of Technology, he has published many technical papers related to terramechanics.

Shingo Ozaki is currently the Associate Professor at Department of Mechanical Engineering at Yokohama National University. His research area covers the computational mechanics of solids and tribology.