One of the major challenges faced by planetary exploration rovers today is the negotiation of difficult terrain, such as fine granular regolith commonly found on the Moon and Mars. Current testing methods on Earth fail to account for the effect of reduced gravity on the soil itself. This work characterizes the effects of reduced gravity on wheel–soil interactions between an ExoMars rover wheel prototype and a martian soil simulant aboard parabolic flights producing effective martian and lunar gravitational accelerations. These experiments are the first to collect wheel–soil interaction imagery and force/torque sensor data alongside wheel sinkage data. Results from reduced-gravity flights are compared with on-ground experiments with all parameters equal, including wheel load, such that the only difference between the experiments is the effect of gravity on the soil itself. In lunar gravity, a statistically significant average reduction in traction of 20% is observed compared with 1g, and in martian gravity an average traction reduction of 5–10% is observed. Subsurface soil imaging shows that soil mobilization increases as gravity decreases, suggesting a deterioration in soil strength, which could be the cause of the reduction in traction. Statistically significant increases in wheel sinkage in both martian and lunar gravity provide additional evidence for decreased soil strength. All of these observations (decreased traction, increased soil mobilization, and increased sinkage) hinder a rover’s ability to drive, and should be considered when interpreting results from reduced-load mobility tests conducted on Earth.

中文翻译：

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减重对行星漫游者机动性的影响

今天行星探测车面临的主要挑战之一是艰难地形的谈判，例如在月球和火星上常见的细颗粒风化层。目前地球上的测试方法无法考虑重力降低对土壤本身的影响。这项工作描述了重力降低对 ExoMars 漫游车车轮原型和抛物线飞行上的火星土壤模拟物之间的车轮-土壤相互作用的影响，产生有效的火星和月球重力加速度。这些实验是第一个收集车轮-土壤相互作用图像和力/扭矩传感器数据以及车轮下沉数据的实验。将减重飞行的结果与所有参数相同的地面实验进行比较，包括轮载荷、因此，实验之间的唯一区别是重力对土壤本身的影响。在月球重力中，观察到与 1g 相比，牵引力平均降低了 20%，具有统计学意义，而在火星重力中，观察到的牵引力平均降低了 5-10%。地下土壤成像显示，随着重力的降低，土壤流动性增加，表明土壤强度恶化，这可能是牵引力降低的原因。火星和月球重力下车轮下沉的统计显着增加为土壤强度降低提供了额外的证据。所有这些观察结果（牵引力降低、土壤流动增加和下沉增加）都会阻碍漫游车的驾驶能力，在解释地球上进行的减载移动性测试的结果时应予以考虑。