Drama Özge, Badri-Spröwitz Alexander
Dynamic Locomotion Group, Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
Front Bioeng Biotechnol. 2020 Dec 18;8:586534. doi: 10.3389/fbioe.2020.586534. eCollection 2020.
Bipedal running is a difficult task to realize in robots, since the trunk is underactuated and control is limited by intermittent ground contacts. Stabilizing the trunk becomes even more challenging if the terrain is uneven and causes perturbations. One bio-inspired method to achieve postural stability is the virtual point (VP) control, which is able to generate natural motion. However, so far it has only been studied for level running. In this work, we investigate whether the VP control method can accommodate single step-down perturbations and downhill terrains. We provide guidelines on the model and controller parameterizations for handling varying terrain conditions. Next, we show that the VP method is able to stabilize single step-down perturbations up to 40 cm, and downhill grades up to 20-40° corresponding to running speeds of 2-5 ms. Our results show that the VP approach leads to asymmetrically bounded ground reaction forces for downhill running, unlike the commonly-used symmetric friction cone constraints. Overall, VP control is a promising candidate for terrain-adaptive running control of bipedal robots.
双足跑步在机器人中是一项难以实现的任务，因为躯干的驱动不足，并且控制受到间歇性地面接触的限制。如果地形不平坦并产生扰动，稳定躯干将变得更具挑战性。一种受生物启发实现姿势稳定的方法是虚拟点（VP）控制，它能够产生自然运动。然而，到目前为止，它仅针对水平跑步进行了研究。在这项工作中，我们研究VP控制方法是否能够适应单步下降扰动和下坡地形。我们提供了关于处理不同地形条件的模型和控制器参数化的指导方针。接下来，我们表明VP方法能够稳定高达40厘米的单步下降扰动，以及对应于2-5米/秒跑步速度的高达20-40°的下坡坡度。我们的结果表明，与常用的对称摩擦锥约束不同，VP方法导致下坡跑步时地面反作用力不对称有界。总体而言，VP控制是双足机器人地形自适应跑步控制的一个有前途的候选方法。
