Comparison of wheel load application methods in single-wheel testbeds

This work reviews wheel load application methods in single-wheel testbeds (SWTBs), used widely to study terramechanics. Normal force oscillations have been reported in SWTBs, and visible in time-series data when provided. This has usually been attributed to grousers, but is also visible for wheels without grousers suggesting other system dynamics (e.g. friction in the vertical axis) are the cause. Furthermore, accelerations related to periodic vertical displacements of the wheel (whether caused by grousers or otherwise) cannot explain more than a small fraction of the amplitude of normal force vari-ations. In this work, a 4-bar mechanism was developed that balances the normal load and ensures that a constant (not oscillating) normal force is achieved throughout terramechanics experiments. System behaviour with and without the 4-bar mechanism was assessed, highlighting the need for a 4-bar mech-anism or other method of balancing normal loads if a constant normal force is desired. No significant effects on average experimental results were observed due to normal force oscillation, but artifacts were observed in the time-series data. Comparisons of results with a system where wheel load is applied pneu-matically and characterization of friction in each testbed provide further support to the conclusion that normal force oscillations are mainly caused by friction in the vertical axis. (c) 2021 ISTVS. Published by Elsevier Ltd. All rights reserved.

这项工作综述了单轮试验台（SWTBs）中的轮载施加方法，单轮试验台被广泛用于研究地面力学。在单轮试验台中已经报道了法向力振荡，并且在提供的时间序列数据中可以看到。这通常归因于轮齿，但在没有轮齿的轮子上也能看到，这表明其他系统动力学（例如垂直轴上的摩擦）是原因。此外，与轮子周期性垂直位移相关的加速度（无论是由轮齿还是其他原因引起的）只能解释法向力变化幅度的一小部分。在这项工作中，开发了一种四杆机构，它可以平衡法向载荷，并确保在整个地面力学实验中实现恒定（无振荡）的法向力。评估了有和没有四杆机构时的系统行为，强调了如果需要恒定的法向力，就需要四杆机构或其他平衡法向载荷的方法。由于法向力振荡，没有观察到对平均实验结果有显著影响，但在时间序列数据中观察到了伪影。将结果与通过气动施加轮载的系统进行比较，并对每个试验台的摩擦特性进行描述，进一步支持了法向力振荡主要是由垂直轴上的摩擦引起的这一结论。（c）2021 ISTVS。由爱思唯尔有限公司出版。保留所有权利。