WheTLHLoc 4W is the second version of a hybrid leg–wheel–track small‐scale ground mobile robot, developed for surveillance and inspection applications. It differs from its predecessor, WheTLHLoc 2W, in two main aspects: the number of wheels (four instead of two), and the new leg design. The overall size of the robot varies depending on the configuration: 500 × 420 × 140 mm (length × width × height) in tracked mode with lowered legs, 315 × 420 × 310 mm in tracked mode with raised legs, and 430 × 420 × 260 mm in wheeled mode. The robot is sufficiently small to explore narrow spaces, both indoors and outdoors, switching between wheeled locomotion on compact surfaces and tracked locomotion on irregular and yielding terrain. Due to its small length, the robot can stand on one tread of a stair. Nevertheless, it is capable of climbing stairs, and the step height limit has been augmented from 165 mm to 180 mm (+9.1%) with respect to the first version, keeping constant the robot overall size. This enhancement has been achieved through a mechanical redesign of the two rotating legs: each leg now features a pair of smaller wheels, actuated by the same actuator through a gear train, instead of a single larger wheel. The significant increase in the maximum step height expands the robot's capabilities for indoor environments, as stairs with a rise higher than 180 mm are extremely uncommon. The paper discusses the mechanical design of WheTLHLoc 4W, the trajectory planning for step/stair climbing, and provides an analytical comparison between the novel architecture and the first version in terms of stability against overturn and slippage. These analytical results are then experimentally verified. The findings demonstrate that the new leg design not only increases the maximum step height (+9.1%), but also reduces the minimum friction coefficient required for successful stair climbing (−19.1% for the maximum step).

中文翻译：

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WheTLHLoc 4W：具有两个履带、两个旋转腿和四个轮子的小型检查地面移动机器人

WheTLHLoc 4W 是混合腿轮履带小型地面移动机器人的第二个版本，专为监视和检查应用而开发。它与其前身 WheTLHLoc 2W 的不同之处在于两个主要方面：车轮数量（四个而不是两个）和新的腿部设计。机器人的整体尺寸根据配置的不同而有所不同：履带式模式（腿降低）为 500 × 420 × 140 mm（长 × 宽 × 高）；履带式模式（腿抬起）为 315 × 420 × 310 mm； 430 × 420 ×轮式模式下为 260 毫米。该机器人足够小，可以探索室内和室外的狭窄空间，在紧凑表面上的轮式运动和不规则和易变形地形上的履带式运动之间切换。由于其长度较小，机器人可以站在楼梯的一个踏板上。尽管如此，它仍然能够爬楼梯，并且台阶高度限制相对于第一个版本从 165 毫米增加到 180 毫米（+9.1%），保持机器人整体尺寸不变。这种增强是通过对两个旋转腿进行机械重新设计来实现的：每个腿现在都有一对较小的轮子，由同一个执行器通过齿轮系驱动，而不是单个较大的轮子。最大台阶高度的显着增加扩展了机器人在室内环境中的能力，因为高度超过 180 毫米的楼梯极为罕见。本文讨论了 WheTLHLoc 4W 的机械设计、台阶/楼梯攀爬的轨迹规划，并在抗翻转和滑移稳定性方面对新型架构与第一个版本进行了分析比较。然后通过实验验证这些分析结果。研究结果表明，新的腿部设计不仅增加了最大台阶高度（+9.1%），而且还降低了成功爬楼梯所需的最小摩擦系数（最大台阶为-19.1%）。