Risk-Aware Planning and Control of Robot Motion Including Intermittent Physical Contact

这个项目考虑了计划和控制涉及间歇性身体接触的运动的问题。这些运动包括在未探索的地形上行走，或操纵重量、形状或表面粗糙度不为人所知的物体。该项目通过两种方式解决这个问题。第一个是建立在人类通过改变四肢的有效弹性来应对不确定性的发现之上。该项目将通过寻找在不确定的初始条件下最小化风险的概率度量的机器人肢体刚度来制定相应的机器人控制方法。也就是说，项目的第一部分将找到一个运动可能的最佳结果，同时考虑到可能的起点的分布。该项目的第二部分解决了一个挑战，即考虑间歇性接触的小变化--例如当一只脚触地，或者手指接触工具--可能在较大任务中传播的所有方式。当所研究的问题具有称为“凸性”的属性时，有有效的方法来处理这种可变性，该属性允许有效地划分和搜索解的空间。接触问题不具有这种理想的性质，然而，该项目将探索通过一系列凸问题来逼近真实问题的方法。行走和抓取机器人将越来越多地帮助制造环境中的人类同事，并帮助老年人和残疾人完成日常任务。该项目将通过提高机器人行走和抓取的性能和可靠性来促进国民的健康和繁荣。这些结果不仅限于机器人学，还将有益于生物力学和人类运动控制研究，在生物力学和人类运动控制研究中，它们可以为分析人类行为提供一个解释性框架。该项目将表征强健接触相互作用的最佳机械阻抗调制，并提供一种方法来计算开环健壮的运动，尽管环境不确定。它将利用风险敏感型最优控制和稳健优化方面的最新结果，明确考虑环境的不确定性，同时确保较低的计算复杂性。该项目的最后一个但也是关键的目标是进行广泛的机器人实验，使用一个单腿跳跃机器人，一个抓取未知物体的机械手，一个四足行走和跳跃的机器人，以及一个用手臂和腿爬上高台阶的人形机器人，从而证明该方法在现实和多样化的机器人场景中的普遍适用性。这些实验试图阐明外部干扰和环境不确定性对最佳阻抗调制和稳健运动的影响。此外，它们还将阐明使复杂任务能够在未知环境中稳健执行的重要因素。该项目还将比较已建立的建模方法预测的最佳腿部阻抗与人类行走数据。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project considers the problem of planning and controlling motions that involve intermittent physical contact. These motions include such tasks as walking across unexplored terrain, or manipulating an object with poorly known weight, shape, or surface roughness. The project approaches this problem in two ways. The first builds upon findings that humans respond to uncertainty by varying the effective springiness of their limbs. The project will formulate a corresponding approach to robot control by finding the robot limb stiffness that minimizes a probabilistic measure of risk under uncertain initial conditions. That is, the first part of the project will find the best possible outcome of a movement, while taking into account a spread of possible starting points. The second part of the project addresses the challenge of considering all the ways in which small changes to intermittent contacts -- such as when a foot hits the ground, or where a finger touches a tool -- can propagate through a larger task. There are efficient methods to handle such variability when the problem being study has a property called "convexity," which allows for efficient partitioning and search of the space of solutions. Contact problems do not have this desirable property, however the project will explore ways to approximate the true problem by a sequence of convex problems. Walking and grasping robots will increasingly help human co-workers in manufacturing settings, and assist elderly and disabled citizens in everyday tasks. This project will promote the national health and prosperity by improving the performance and reliability of robotic walking and grasping. The results are not limited to robotics and will also be beneficial in bio-mechanics and human motor control research, where they could suggest an explanatory framework for analyzing human behavior.The project will characterize the optimal mechanical impedance modulation for robust contact interactions and provide a methodology to compute motions that are open-loop robust despite environmental uncertainties. It will leverage recent results in risk-sensitive optimal control and robust optimization to explicitly consider uncertainty about the environment while ensuring low computational complexity. The last but key objective of the project is to conduct extensive robotic experiments with a one-legged jumping robot, a manipulator grasping unknown objects, a quadruped walking and jumping and a humanoid robot climbing up high steps using its arms and legs therefore demonstrating the general applicability of the methodology in realistic and diverse robotic scenarios. The experiments seek to clarify the influence of external disturbances and environmental uncertainty on optimal impedance modulation and robust movements. Additionally, they will shed light on the important factors enabling robust execution of complex tasks in unknown environments. The project will also compare the optimal leg impedance predicted by the established modeling methodology with human walking data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.