A Parametric study and experimental testing of lunar-wheel suspension on dynamic terrainability

Abstract

The development of a flexible metallic wheel proved to be one of the most challenging and time-consuming aspects of the Lunar Roving Vehicle of the Apollo missions (V. Asnani, D. Delap, and C. Creager. 2009. Journal of Terramechanics, 46: 89 103). The design was realized through an iterative trial and error design process, driven primarily by manufacturability and physical testing. Although the wire-mesh-compliant wheel design was identified as the best choice for the Lunar Roving Vehicle, mission scenarios have evolved and future lunar vehicles are bound to have to meet different functional requirements and more severe life and operational constraints. For example, these vehicles will have to travel farther on the lunar surface, explore permanently shadowed craters, and perform a variety of tasks such as transporting sensitive payloads and excavatiing regolith, and allow for both unmanned and manned operation. This work focuses on optimizing the suspension design parameters of a flexible, compliant wheel for maximizing the dynamic terrainability performance of a lunar rover. The suspension design parameters are identified, independently of the explicit wheel configuration. The terrainability of the rover is defined here as the rover's ability to negotiate terrain irregularities. Terrainability is quantified by the objective functions describing road holding and rider comfort. These objective functions ensure that the rover payload is isolated from vehicle terrain-induced vibrations, and that the wheels maintain ground contact during higher speed traversals. A simplified vehicle model is used for the dynamics analysis of the terrain vehicle system with the terrain modeled as a random stationary ergodic process characterized by a power spectral density function. A sensitivity analysis is performed to identify conflicting objectives, and a recommendation on optimal wheel suspension design variables is made. Finally, experimental testing of reduced-scale wheels with different suspension properties is conducted on three irregular terrain types and results confirm the theoretical predictions. Ultimately, the results of this research will be used in a system-level analysis of the wheel design parameters on vehicle performance to guide the structural optimization of the compliant wheel for lunar surface exploration vehicles.

Terrain estimation via vehicle vibration measurement and cubature Kalman filtering

“…In this vehicle, no coil spring is present, and the suspension and tire stiffness may be combined into a joined stiffness k and sprung and unsprung mass can be condensed in a unique mass ms, as shown in Figure 10. This leads to a single-DOF system, as suggested in Faragalli et al (2011), whose model parameters are reported in Table 5.

Figure 10.General one degrees of freedom quarter-car model for the lunar rover vehicle.

…”

“…In this vehicle, no coil spring is present and the suspension and tire stiffness may be combined into a joined stiffness k, as well as, sprung and unsprung mass can be condensed in a unique mass m s , as shown in Figure 10. This leads to a single degree of freedom system, as suggested in Faragalli et al (2011), whose model parameters are reported in Table 5. The state and measurement vector of the corresponding estimation problem reduce respectively to x = [y 1 − hẏ 1 k tot ] T and z = [ÿ 1 ], whereas the transition matrix A can be obtained from that of the 2 DOF QC case by removing the third and fourth line and column, and matrices B, C, G can be adapted accordingly.…”

Design, properties, and applications of non-pneumatic tires: A review

“…Nevertheless, a substantial amount of NPTs that has been proposed is composed of a single elastomeric material such as TPU. 33,[124][125][126] Other approaches are based on alloys such as steel 102 or a shape memory alloy, 11 as of the examples proposed by NASA. Furthermore, tire sections can have distinct material compositions and production techniques.…”

“…This example dates to 2019 and is an evolution of the lunar roving vehicle tires, made of knitted metallic meshes, that were used during the Apollo (15/16/17) missions. [11][12][13][14][15] Some airless wheel concepts are already present in commercially available solutions for trailers, wheelchairs, or small electric scooters, with most of these being made from rubber or polymers. [16][17][18] Figure 1(g) shows an example of an electric scooter solid rubber tire.…”