Whole-Body Control (WBC) has emerged as an important framework in locomotion control for legged robots. However, most WBC frameworks fail to generalize beyond rigid terrains. Legged locomotion over soft terrain is difficult due to the presence of unmodeled contact dynamics that WBCs do not account for. This introduces uncertainty in locomotion and affects the stability and performance of the system. In this article, we propose a novel soft terrain adaptation algorithm called STANCE: Soft Terrain Adaptation and Compliance Estimation. STANCE consists of a WBC that exploits the knowledge of the terrain to generate an optimal solution that is contact consistent and an online terrain compliance estimator that provides the WBC with terrain knowledge. We validated STANCE both in simulation and experiment on the Hydraulically actuated Quadruped (HyQ) robot, and we compared it against the state-of-the-art WBC. We demonstrated the capabilities of STANCE with multiple terrains of different compliances, aggressive maneuvers, different forward velocities, and external disturbances. STANCE allowed HyQ to adapt online to terrains with different compliances (rigid and soft) without pretuning. HyQ was able to successfully deal with the transition between different terrains and showed the ability to differentiate between compliances under each foot.

中文翻译：

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姿态：软地形上的运动适应

全身控制 (WBC) 已成为腿式机器人运动控制的重要框架。然而，大多数 WBC 框架无法在刚性地形之外进行泛化。由于存在 WBC 未考虑的未建模的接触动力学，在软地形上的腿运动很困难。这会在运动中引入不确定性并影响系统的稳定性和性能。在本文中，我们提出了一种新的软地形自适应算法，称为 STANCE：Soft Terrain Adaptation and Compliance Estimation。STANCE 由 WBC 组成，该 WBC 利用地形知识生成接触一致的最佳解决方案，以及为 WBC 提供地形知识的在线地形符合性估计器。我们在液压驱动四足 (HyQ) 机器人的模拟和实验中验证了 STANCE，并将其与最先进的 WBC 进行了比较。我们展示了 STANCE 在不同顺应性、激进机动、不同前进速度和外部干扰的多种地形下的能力。STANCE 允许 HyQ 在线适应具有不同顺应性（刚性和软性）的地形，而无需预先调整。HyQ 能够成功处理不同地形之间的过渡，并显示出区分每只脚下的顺应性的能力。STANCE 允许 HyQ 在线适应具有不同顺应性（刚性和软性）的地形，而无需预先调整。HyQ 能够成功处理不同地形之间的过渡，并显示出区分每只脚下的顺应性的能力。STANCE 允许 HyQ 在线适应具有不同顺应性（刚性和软性）的地形，而无需预先调整。HyQ 能够成功处理不同地形之间的过渡，并显示出区分每只脚下的顺应性的能力。