Amenosis J.R. Lopez-Arreguin and Enrico Stolloın
Wheels, 3D-printing, rover, in-situ, regolith
A series of tests were conducted for a typical metal rover wheel on sandy terrain. Stresses generated in the soil are normally integrated to yield the forces and moments acting on the wheel–soil interface. However, previous research suggests that their accuracy depends on (1) the slip ratio, (2) soil cohesion and (3) the sensor type, for which most work relied on many-axis force transducers and multiple sensing point measurements which are difficult to instrument in an actual rover. In this article, we review the problem suggesting that simple 1 DOF (degrees of freedom) transducers with a single measuring point can estimate the normal force better than 7% of error at very high slip. By combination of the real-time measurements of the normal stress profile detected with the sensor device, and analytical modelling of Janosi–Hanamoto for the shear stress, new terramechanics scenarios are studied fixing the centre of mass of the wheel and studying the contact angles, stresses and forces according to the number of revolutions (NOR). We have also shown that the force prediction error increases according to the NOR, up to 18% after 5 NOR. In-situ, a 3D-printed wheel was compared to a typical rigid metal rover wheel under the previous terramechanics scenarios showing no significant difference between both rapid prototyping and conventional wheels. The 3D-printed wheel displays suitable performance characteristics similar to the rigid metal-wheel in several key scenarios at fixed high slip ratio. This could eventually benefit the verification of more robust rover technologies in analogue terrains with fast-track approaches using rapid prototyping.
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