Snakes can move through almost any terrain. Similarly, snake robots hold the promise as a versatile platform to traverse complex environments like earthquake rubble. Unlike snake locomotion on flat surfaces which is inherently stable, when snakes traverse complex terrain by deforming their body out of plane, it becomes challenging to maintain stability. Here, we review our recent progress in understanding how snakes and snake robots traverse large, smooth obstacles that lack anchor points for gripping or bracing. First, we discovered that the generalist variable kingsnake combines lateral oscillation and cantilevering. Regardless of step height and surface friction, the overall gait is preserved. Next, to quantify static stability of the snake, we developed a method to interpolate continuous body in three dimensions (both position and orientation) between discrete tracked markers. By analyzing the base of support using the interpolated continuous body 3-D kinematics, we discovered that the snake maintained perfect stability during traversal, even on the most challenging low friction, high step. Finally, we applied this gait to a snake robot and systematically tested its performance traversing large steps with variable heights to further understand stability principles. The robot rapidly and stably traversed steps nearly as high as a third of its body length. As step height increased, the robot rolled more frequently to the extent of flipping over, reducing traversal probability. The absence of such failure in the snake with a compliant body inspired us to add body compliance to the robot. With better surface contact, the compliant body robot suffered less roll instability and traversed high steps at higher probability, without sacrificing traversal speed. Our robot traversed large step-like obstacles more rapidly than most previous snake robots, approaching that of the animal.

中文翻译：

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横向摆动和身体顺应性帮助蛇和蛇形机器人稳定地穿越大而光滑的障碍物

蛇几乎可以穿越任何地形。同样，蛇形机器人有望成为穿越地震瓦砾等复杂环境的多功能平台。与蛇在平坦表面上的运动本质上是稳定的不同，当蛇通过使身体偏离平面而穿越复杂地形时，保持稳定性变得具有挑战性。在这里，我们回顾了我们最近在理解蛇和蛇机器人如何穿越缺乏用于抓握或支撑的锚点的大而光滑的障碍物方面的进展。首先，我们发现通才变量 kingsnake 结合了横向摆动和悬臂。无论步高和表面摩擦如何，整体步态都保持不变。接下来，要量化蛇的静态稳定性，我们开发了一种方法，可以在离散的跟踪标记之间在三个维度（位置和方向）中插入连续体。通过使用插值连续体 3-D 运动学分析支撑基础，我们发现蛇在穿越过程中保持完美的稳定性，即使是在最具挑战性的低摩擦、高步上。最后，我们将这种步态应用到蛇形机器人上，并系统地测试了其在不同高度下穿越大步的性能，以进一步了解稳定性原理。机器人快速而稳定地跨过几乎高达其身长三分之一的台阶。随着台阶高度的增加，机器人更频繁地翻滚到翻倒的程度，从而降低了穿越概率。具有柔顺身体的蛇没有出现这种故障，这激发了我们为机器人增加身体柔顺性。具有更好的表面接触，柔顺体机器人遭受更少的滚动不稳定性并以更高的概率穿越高步，而不会牺牲穿越速度。我们的机器人比大多数以前的蛇形机器人更快地穿过大型台阶状障碍物，接近动物的障碍物。